pubs.acs.org/OrganometallicsPublished on Web 09/18/2009r 2009 American Chemical Society

Organometallics 2009, 28, 5757–5764 5757

DOI: 10.1021/om9006517

(η6-Bromoarene)Mn(CO)3

þComplexes: Synthesis and Applications to

the Functionalization of (η5-Cyclohexadienyl)Mn(CO)3 Complexes by

Halogen-Metal Exchange Reaction

Antoine Eloi, Franc-oise Rose-Munch,* Eric Rose,* and Petra Lennartz

UPMCUniv Paris 06, IPCM,CNRSUMR7201, Equipe Chimie Organique et Organom�etallique, Case 181,4 Place Jussieu, F-75005 Paris, France

Received July 23, 2009

(η6-Bromoarene)Mn(CO)3þ complexes substituted by methoxy or silyl groups were easily pre-

pared in good to excellent yields, and the molecular structure of [(η6-1-bromo-4-methoxy-benzene)Mn(CO)3]

þBF4- has been determined by X-ray crystallography. Nucleophilic additions

of LiAlH4 or PhMgCl delivered the corresponding neutral (η5-bromocyclohexadienyl)Mn(CO)3complexes. Using ClCO2Et and DMF as electrophiles, bromide substitution was achieved bymetal-halogen exchange reaction applied to the (η5-bromocyclohexadienyl)Mn(CO)3 com-plexes and allows the regioselective functionalization of the η5-cyclohexadienyl ligand when thetwo substituents of the starting complex are not adjacent. Furthermore the synthesis of the first(η5-cyclohexadienyl)Mn(CO)3 complexes substituted at one of the extremities of the π-system by aformyl group and the X-ray analysis of one of them emphasized the excellent agreement between thestructural and energetic data obtained in the present work and the computed results already reported.

Introduction

Cationic arene π complexes of manganese1 are of impor-tance as auxiliaries in the synthesis of natural and pharma-ceutical products2 and of dearomatized compounds withinteresting selectivities.3 More recently they were usednot only as building blocks for coordination network archi-tectures4 and for nanostructures on surfaces5 but also inthe preparation of new manganese-based ligands forenantioselective catalysis.6 Functionalization of cationic(η6-arene)Mn(CO)3

þ complexes and of the correspondingneutral η5-cyclohexadienyl complexes, formed by an exoaddition of a nucleophile to the coordinated arene ring, has

found widespread applications after the discovery of palla-dium cross-coupling7 and lithiation/electrophilic quenchreactions8 in the η5-cyclohexadienyl-Mn series. These recentdevelopments enable ready access to a large variety ofsubstituted η5-cyclohexadienyl-Mn complexes and conse-quently to the corresponding cationic η6-arene-Mn whenthe η5-cyclohexadienyl-Mn complex is substituted by ahydrogen atom at the sp3 carbon atom: indeed, in that case,it can be easily rearomatized by hydride abstraction withtriphenylmethyl tetrafluoroborate.7a,9 These two methodsof functionalization require the presence of a halogenosubstituent on the η5 π-system in the case of the palladiumcross-coupling reactions and of an alkoxy or halogenogroup for their good ortho-directing properties in the caseof the lithiation/electrophilic sequence. Furthermore thewell-precedented ipso nucleophilic substitution has also beendeveloped for the functionalization of (η6-halogenoarene)-Mn(CO)3

þ, and it was shown that the halogen on thecoordinated arene ring was easily substituted by amino,alkoxy, and thio groups.10 Thus, the presence of a halogeno

*To whom correspondence should be addressed. E-mail: francoise.rose@upmc.fr; eric.rose@upmc.fr.(1) (a) Rose-Munch, F.; Gagliardini, V.; Renard, C.; Rose, E.Coord.

Chem. Rev. 1998, 178-180, 249. (b) Rose-Munch, F.; Rose, E. Eur. J.Inorg. Chem. 2002, 1269. (c) K€undig, E. P. Topics in OrganometallicChemistry; Springer: Berlin, 2004; Vol. 7. (d) “Manganese CompoundswithCO Ligands”. Sweigart, D. A.; Reingold, J. A.; Son, S. U. InComprehensiveOrganometallic Chemistry III; Crabtree, R. H., Mingos, D. M. P., Eds.;Elsevier Science Ltd: Oxford, UK, 2006; Vol. 5, p 761. (e) Astruc, D.Organometallic Complexes and Catalysis,; Springer: Heidelberg, 2007; pp243-249.(2) See for example: (a) Pearson, A. J.; Lee, S. H.; Gouzoules, F. J.

Chem. Soc., Perkin Trans. 1990, 2251. (b) Pearson, A. J.; Bruhn, P. R. J.Org. Chem. 1991, 56, 7092. (c) Pearson, A. J.; Shin, H. Tetrahedron 1992,48 (36), 7527. (d)Miles,W.H.; Brinkman,H. R.TetrahedronLett. 1992, 33,589.(3) (a) Pape, A. R.; Kaliappan, K. P.; K€undig, E. P.Chem. Rev. 2000,

100, 2917. (b) Roell, B. C.; Mc Daniel, K. F.; Vaughan, W. S.; Macy, T. S.Organometallics 1993, 12, 224. (c) Pearson, A. J.; Vickerman, R. J.Tetrahedron Lett. 1998, 39, 5931.(4) Oh,M.;Carpenter,G.B.; Sweigart,D.A.Acc.Chem.Res. 2004, 1, 1.(5) Oh,M.; Carpenter, G. B.; Sweigart, D. A.Angew. Chem., Int. Ed.

2009, 1, 1.(6) Cetiner, D.; Jacques, B.; Payet, E.; Chavarot-Kerlidou,M.; Rose-

Munch, F.; Rose, E.; Tranchier, J. P.; Herson, P.Dalton Trans. 2009, 27.

(7) (a)Auffrant, A.; Prim,D.; Rose-Munch, F.; Rose, E.; Schouteeten,S.; Vaisserman, J.Organometallics 2003, 22, 1898. (b) Prim, D.; Andrioletti,B.; Rose-Munch, F.; Rose, E.; Couty, F. Tetrahedron 2004, 60, 3325.

(8) (a) Jacques, B.; Chavarot, M.; Rose-Munch, F.; Rose, E. Angew.Chem., Int. Ed. 2006, 45, 3481. (b) Jacques, B.; Chanaewa, A.; Chavarot-Kerlidou, M.; Rose-Munch, F.; Rose, E.; G�erard, H. Organometallics 2008,27, 626. (c) Jacques, B.; Eloi, A.; Chavarot-Kerlidou, M.; Rose-Munch, F.;Rose, E.; G�erard, H.; Herson, P. Organometallics 2008, 27, 2505. (d) Eloi,A.; Rose-Munch, F.; Rose, E.; Chavarot-Kerlidou, M.; G�erard, H. Organo-metallics 2009, 28, 925.

(9) Woo, K.; Williard, P. G.; Sweigart, D. A.; Duffy, N. W.;Robinson, B. H.; Simpson, J. J. Organomet. Chem. 1995, 487, 111.

(10) (a) Pauson, P. L.; Segal, J. A. J. Chem. Soc., Dalton Trans. 1975,1677. (b) Pearson, A. J.; Shin, H. J. Org. Chem. 1994, 59, 2314, andreferences therein.

5758 Organometallics, Vol. 28, No. 19, 2009 Eloi et al.

group has been found to be essential for the functionalizationof η5 and, hence, η6 Mn complexes. To the best of ourknowledge, only chloro-substituted η6 Mn complexes havebeen used in the literature up to now. Indeed, they are easilyprepared by the arene coordination to the [Mn(CO)3]

þ

entity, which is formed either by the Fischer-Hafner reac-tion from Mn(CO)5Br and AlCl3 or by “the anhydridetrifluoroacetic method” under very harsh reaction condi-tions in the presence of Mn2(CO)10, Mn(CO)5Br, or[Mn2(CO)8(μ-Cl)2], a strong acid, and trifluoroacetic anhy-dride.11

In the course of our research dealing with the functiona-lization of η5-cyclohexadienyl-Mn complexes, we were inter-ested in extending the study of the substitution of thesecomplexes using (η6-bromoarene)Mn(CO)3

þ complexes asstartingmaterial.We report herein the efficient synthesis of aseries of cationic η6-bromoarene-Mn complexes and of theircorresponding neutral η5-cyclohexadienyl-Mn derivativesand their application, which is illustrated by their functio-nalization using bromine-metal exchange reaction.

Results and Discussion

Synthesis of Cationic (η6-Halogenoarene)Mn(CO)3

þCom-

plexes.Toour knowledge, concerning fluoro-substitutedMncomplexes only one publication reports the attempt to pre-pare a (η6-fluorobenzene)Mn(CO)3

þ complex,10a but it wasimpossible to isolate it because of its too high reactivity. Asfor the bromo-substituted ones, one synthesis has beenreported more than 30 years ago10a using Fischer-Hafnerreaction conditions by reacting bromobenzene with a mix-ture of AlCl3 and Mn(CO)5Br. The expected complex wasobtained contaminated with (η6-benzene)Mn(CO)3

þ, corre-sponding to the carbon-bromide bond cleavage. After athree-step procedure for the purification, (η6-bromo-benzene)Mn(CO)3

þ was isolated in a poor yield of 8%. Toour knowledge, no other preparation of bromo-substitutedmanganese complexes has been reported since then.

In a preliminary experiment, we performed the coordina-tion of bromobenzene usingAgBF4 andMn(CO)5Br to formthe [Mn(CO)5]

þ fragment (“AgBF4 method”),12 but nosatisfying result was obtained. This is exactly the case ofthe (chlorobenzene)Mn(CO)3 complex, whose preparation isdescribed in 6% yield under the “AgBF4 method” condi-tions,11 whereas the coordination of chloroarenes substi-tuted by electron-donor groups such as alkyl or alkoxy

groups was reported with good yields.12,13 Thus we tried toachieve the complexation of the ortho-bromoanisole 1a usingthe “AgBF4 method”, and we were pleased to obtain thecorresponding η6 complex in 69% yield (Table 1, entry 1).The same conditionswere used for the complexation ofmeta-and para-bromoanisole (arenes 1b and 1c, entries 2 and 3) aswell as formeta-trimethylsilylbromobenzene 3 (entry 4), andthe corresponding complexes, 2b, 2c, and 4, were easilyobtained in good to excellent yields of 79, 76, and 85%,respectively (Table 1, entries 2-4).

Pleasingly, monocrystals of complex 2c14 were readilyobtained by slow evaporation of an acetone solution of thecomplex. Two ORTEP views are shown in Figure 1. TheMn(CO)3 moiety exhibits the well-known regular piano-stool geometry.7a,11 The methoxy group and the C2 and C6

carbon atoms are almost eclipsed by one Mn-CO bond.Indeed the values of the torsion angles C4-C100-Mn-C8,C6-C100-Mn-C9, and C2-C100-Mn-C10, C100 beingthe center of the six-membered ring, are -3.92�, -3.75�,and -1.76�, respectively. Five of the Mn-C arene bondshave roughly the same length, with values ranging from2.182(3) to 2.226(3) A, whereas the Mn-C4 bond is signifi-cantly longer, with a 2.302(4) A value, involving a bending ofthe arene ring in a direction opposite the Mn(CO)3 moiety.This is in good agreement with the distortion observed in thearene rings of mono- and disubstituted (η6-arene)tricarbo-nylchromium complexes.15,16 Indeed the angular deviation

Table 1. Complexation of Halogeno-Arenes to the [Mn(CO)3]þ

Entity

entry arene X R η6 complex [yield %]

1 1a Br o-OMe 2a [69]2 1b Br m-OMe 2b [79]3 1c Br p-OMe 2c [76]4 3 Br m-SiMe3 4 [85]5 5 I p-OMe 6 [68]

Figure 1. ORTEP view of complex 2cwith thermal ellipsoids atthe 30% probability level. Selected interatomic distances (A):Mn-C1 2.182(3); Mn-C2 2.189(3); Mn-C3 2.218(4); Mn-C4

2.302(4); Mn-C5 2.226(3); Mn-C6 2.182(3); C1-Br 1.899(4);C1-C2 1.420(5); C2-C3 1.397(5); C3-C4 1.430(5); C4-C5

1.425(5); C5-C6 1.421(5).

(11) Jackson, J. D.; Villa, S. J.; Bacon, D. S.; Pike, R. D. Organome-tallics 1994, 13, 3972.(12) Pearson, A. J.; Richards, I. C. J. Organomet. Chem. 1983, 258,

C41–C44.(13) Balssa, F.; Gagliardini, V.; Rose-Munch, F.; Rose, E. Organo-

metallics 1996, 15, 4373.(14) X-ray crystal structure determination for 2c and 21. Crystal data

for complex 2c: C10H7BBrF4MnO4, M = 412,80, monoclinic, spacegroup P21/c ; dimensions a = 18.5888(16) A, b = 7.6169(10) A, c =20.189(2) A, β=100.105(10)�.V=2814.2(5) A3;Z=8. The data werecollected in the h k l range:-25 to 26,-10 to 10,-28 to 28. Independentreflections: 8139; data were collected up to a 2θmax value of 60�. Numberof variables: 381; R(I > 2σ(I)) = 0.035, wR2(all) = 0.062, S = 1.026;highest residual electron density 1.45 e A-3. Crystal data for complex 21:C17H14MnO5,M=353.23, monoclinic, space groupP21/c ; dimensionsa=10.1656(13) A, b=9.5568(9) A, c=17.075(2) A, β=104.778(11)�.V=1604.0(3) A3;Z=4. The data were collected in the h k l range:-14to 12, -13 to 13, -24 to 22. Independent reflections 4665. Data werecollected up to a 2θmax value of 60�. Number of variables: 209; R(I >2σ(I)) = 0.043, wR2(all) = 0.126, S = 0.946; highest residual electrondensity 1.13 e A-3.

(15) (a) Hunter, A. D.; Shilliday, L.; Furey, W. S.; Zawarotko, M. J.Organometallics 1992, 11, 1550. (b) Hunter, A. D.; Mozol; Tsai, S. D.Organometallics 1992, 11, 2251.

(16) Djukic, J. P.; Rose-Munch, F.; Rose, E.; Vaissermann, J. Eur. J.Inorg. Chem. 2000, 1295.

Article Organometallics, Vol. 28, No. 19, 2009 5759

of the substituted carbons (ipso carbons) depends on theelectronegativity, the inductive and the resonance effects ofarene substituents, a π-accepting group bending the aro-matic ipso carbon toward the Cr(CO)3 moiety, while theopposite was observed with a π-donating group.

Encouraged by these results, we tried to synthesize aniodo-substituted complex under the same experimental con-ditions, starting from para-iodoanisole 5, and the expectedcomplex 6 was obtained in 68% yield (Table 1, entry 5). Tothe best of our knowledge, this compound represents the firstexample of a (η6-iodoarene)Mn(CO)3

þ complex ever re-ported in the literature. 1H NMR spectra of the η6-arenecomplexes 2c and 6 and those of (η6-para-chloroanisole)-Mn(CO)3

þ do not exhibit significant changes in the chemicalshifts of the two characteristic doublets, which are thefingerprints of such para-disubstituted arenes:13 7.47 and6.53 ppm for 2c, 7.48 and 6.42 ppm for 6, and 7.51 and 6.65ppm for the chloro-substituted complex.Nucleophilic Additions. We then explored the reactivity of

the bromo-substituted complexes toward nucleophiles suchas LiAlH or PhMgBr, and the usual experimental conditionsfor such additions were used.7a,10a,17 The correspondingneutral (η5-cyclohexadienyl)Mn(CO)3 complexes were iso-lated in yields ranging from 65 to 94% (Table 2). Theaddition is regioselective for the anisole derivative complexeswhatever the nucleophile: ortho to the bromine atom for the

ortho- and para-disubstituted complexes (Table 2, entries 1,3, 5); this is in good agreement with what is known in thechloro-anisole series due to the synergic effects of the in-ductive ortho-directing halogeno group and the meso-meric meta-orienting methoxy group.7a,13,17 The additionoccurs meta to the bromine atom for the meta-disubstitutedcomplexes (Table 2, entries 2, 4), in good agreement with thestrongestmeta-orienting effect of the methoxy group.Meta-silylated bromoarene complex 4, after reacting withPhMgBr, gave rise to the formation of two η5-cyclohexadie-nyl complexes corresponding to the nucleophile additionortho and meta to the bromine atom in a 3:1 ratio in 92%yield (Table 2, entry 6).Functionalization of (η5-Cyclohexadienyl)Mn(CO)3 Com-

plexes by Halogen-Metal Exchange Reaction. Up to now,two methodologies have been developed to functionalize theπ system of η5-cyclohexadienyl complexes: the pallado-cata-lyzed reactions (Scheme 1, steps a and b) and the lithiation/electrophilic quench (Scheme 1, step c).

These functionalization methods need some comments tounderstand their efficiency:• Palladium coupling: the chloro-substituted η5-cyclohexa-

dienyl complexes are easily transformed, by palladium-catalyzed cross-coupling reactions, into the correspondingcompounds due to the ipso substitution of the halogen by thenucleophile R2 (Scheme 1, step a) or into the keto derivativesif the coupling is achieved under carbonylative conditions(Scheme 1, step b).7a Organomanganese transmetalationcatalyzed by Fe(acac)3 was shown to be an easy and com-plementarymethod to prepare keto η5-cyclohexadienyl com-plexes that cannot be made by palladium cross-couplingreactions.8d Nevertheless, in any case, it was impossible tograft the strategic aldehyde group using these conditions. Itwas also observed that when the chloride substituent is atthe C2 position, pallado-catalyzed reactions were muchslower and the corresponding substituted η5-cyclohexadie-nyl complexes were obtained in lower yields than when thechloride substituted the C1 position.• Lithiation: if the η5-cyclohexadienyl complexes were

substituted by ortho-directing groups such as a OMe or aCl group, the lithiation always occurred ortho to the sub-stituent, and thus, it was impossible to functionalize at themeta positionwith respect to an ortho-directing group.Whenboth OMe and Cl ortho-directing groups were present on theη5 system at C1 and C4 positions for example, two regioi-somers were obtained, corresponding to lithiation orthowithrespect to each substituent. Without the presence of theactivating Cl substituent, the reaction requires the additionof TMEDA for complete conversion of the substrate.8

Table 2. (η5-Bromocyclohexadienyl)Mn(CO)3 Complexes

aThe Mn(CO)3 tripod was omitted for clarity.

Scheme 1. FunctionalizationMethods ofη5-Cyclohexadienyl-Mn

Complexes

(17) Chung, Y. K.; Williard, P. G.; Sweigart, D. A. Organometallics1982, 1, 1053.

5760 Organometallics, Vol. 28, No. 19, 2009 Eloi et al.

Finally, it was observed that, whatever the experimentalconditions, deprotonation could never occur at the extremityof the η5 π system (C1 or C5 carbon atom), which preventsintroducing synthetically important groups, such as a formylgroup, in such positions.

We undertook the study of the lithiation of bromo-sub-stitutedη5-cyclohexadienyl complexes. nBuLiwas added to asolution of complex 7a-H in THF at low temperaturefollowed by CH3OD quenching. A mixture of three deuter-ated η5 complexes, 11, 12, and 13, was obtained in a 1:5:2ratio (Scheme 2). Complex 11 corresponds to the substitu-tion of Br by D, complex 12 to the debromination of thestarting complex 7a-H then lithiation and electrophilicquench by Dþ at the C3 position, and finally complex 13 toa lithiation/deuteration quench at the ortho position of theOMe group in complex 7a-H (Scheme 2).

In order to try to obtain a better regioselectivity and, thus,to favor halogen-metal exchange reaction, the reverse addi-tion of the reactants was achieved and a solution of complex7a-H was transferred at low temperature to a solution ofnBuLi in THF. After 10 min of stirring, CH3OD was added.After usual workup, only complex 11 was isolated, in anexcellent yield of 94%. Once the experimental conditionssettled, they were applied to other electrophiles (ClCO2Etand DMF) with complex 7a-H and to bromo-η5-cyclohexa-dienyl regioisomers such as 7c-H and 8b-H. With complex7a-H and ClCO2Et and DMF as electrophiles, two regio-isomers were obtained in a 1:1 ratio in each case. Complexes14 and 15 (Table 3, entry 1) and 16 and 17 (entry 2) wereisolated in 72% (7:1 ratio) and 79% yield (1:1 ratio),respectively. The lack of regioselectivity could be explainedby the formation of the anion at the C1 carbon, strongly

stabilized by the methoxy group, which could rearrange intothe C3 carbon anion, also stabilized by the methoxy group.

In contrast, the reaction with other complexes substitutedby a bromine group at the C1 carbon and with the OMegroup at the C4 carbon such as complexes 7c-H and 7c-Ph isregioselective, and the expected complexes were isolated in54 and 60%moderate yields when ClCO2Et was taken as theelectrophile, probably due to their unstability (Table 4,entries 1 and 3), and in better yields when DMF was chosenas the electrophile (75 and 81%, entries 2 and 4).

The halogen-metal exchange was also revealed to beefficient in the case of 2-bromo-4-methoxycyclohexadienylderivatives. Again, the yields were higher with DMF as theelectrophile (82 and 79%, Table 5, entries 2 and 4) thanthosewithClCO2Et as the electrophile (64 and 55%, entries 1and 3). The C4 carbon anion is not stabilized by the methoxygroup at the C2 carbon as in the previous case (Table 4),which could explain the regioselectivity of the reaction inboth cases.

Thus the exchange reaction is very fast, and no addition ofTMEDA was necessary to obtain a complete conversion asobserved for some “direct” lithiations.8 The reaction isregioselective when the halogeno group is not adjacent tothe methoxy substituent. It is the only way to introduce aformyl group at the C1 carbon, which cannot be performedby “direct” lithiation or palladium cross-coupling reactions.

Scheme 2. Addition of nBuLi to Complex 7a-H Followed by Dþ

Quenching

Table 3. Halogen-Metal Exchange of a 1,2-Disubstituted η5-

Cyclohexadienyl-Mn Complex

entry -E products ratio yield (%)

1 -CO2Et 14a þ 15

a 7:1 722 -CHO 16a þ 17a 1:1 79

aPurified by chromatography.

Table 4. Halogen-Metal Exchange in 1,4-Disubstituted η5-

Cyclohexadienyl Complexes

entry -E R product yield (%)

1 -CO2Et H 18 542 -CHO H 19 753 -CO2Et Ph 20 604 -CHO Ph 21 81

Table 5. Halogen-Metal Exchange in 2,4-Disubstituted η5-

Cyclohexadienyl Complexes

entry -E R product yield [%]

1 -CO2Et H 22 642 -CHO H 23

a 823 -CO2Et Ph 24 554 -CHO Ph 25a 79

aPurified by chromatography.

Article Organometallics, Vol. 28, No. 19, 2009 5761

Furthermore, this reaction allows the functionalization atthe meta position with respect to an ortho-directing groupsuch as a methoxy group (complexes 22, 23, 24, and 25).

Complexes 19 and 21 were the first η5 complexes substi-tuted by a formyl group at the C1 position; thus it wasinteresting to know more about their structure in the solidstate. Crystals of complex 21

14 suitable for a radiocrystallo-graphic study were readily obtained from a diethyl ethersolution by a two-well diffusion procedure (petroleum etherin the outer well). The ORTEP view is shown in Figure 2

It was interesting to compare this structure with the one ofcomplex 26,18 which differs from complex 21 only by thepresence of the keto thienyl group at the C1 carbon instead ofthe formyl group. The presence of a formyl group does notmodify the η5-cyclohexadienyl structure with five coplanarsp2 carbon atoms and the remaining sp3 carbon located 42.8�above this plane (38� in 26). The Mn-C bond lengths rangefrom 2.129 to 2.216 A (2.119 to 2.215 A in 26). The formylgroup is nearly coplanar with the cyclohexadienyl moiety,the angle between the two planes being 5.2�, whereas the ketogroup in 26 is deviated by 26� toward the Mn(CO)3 entityfrom the [C1, C2, ... C5] plane and by 14� from the thienylring. The carbonyl groupof the formyl function is pointing inthe direction of the C6 sp3 carbon (syn conformation), incontrast with that of the keto group in 26, which is located inthe direction opposite the C6 carbon, thus adopting an anticonformation with respect to the C6 carbon.

In the course of a previous work,8d computational studieswere reported concerning the relative energies of the three(η5-formylcyclohexadienyl)Mn(CO)3 regioisomers (namely,a, b, c, Figure 3) without any substituent on the π system andwith two hydrogens at the C6 carbon, as no effect of the Phsubstituent at C6 was observed, as well as the vibrationalfrequencies of the three formyl groups. For each of them, thepreferred conformation of the CHO group was computed(Figure 3). It was shown that themost stable regioisomerwasthe conformer a, with a syn conformation of the CdO formylgroup with respect to the C6 sp3 carbon, in good agreementwith the X-ray structure of complex 21, as long as thepresence of the OMe group at the C4 carbon does notmodifythis conformation. Up to now, only values of computed IRfrequencies of b and c could be compared with the experi-mental ones; indeed the corresponding complexes were easilyavailable by lithiation/electrophilic quench of the η5 system.

Having in hand a method to introduce a formyl groupat the extremity of the π system, we tried to prepare the“missing candidate”, namely, complex 28 (Scheme 3). As thepreparation of the cationic (η6-bromobenzene)Mn(CO)3

þ

was reported in a yield <6%, another starting material,the silylated complex 9b-Ph, was chosen for the synthesisof 28. Addition of a THF solution of 9b-Ph in a THF solu-tion of nBuLi followed by reaction with DMF led to theformation of complex 27 in 66% yield, substituted bya formyl group at the C1 carbon. Addition of tetrabutylam-monium fluoride to a THF solution of complex 27 gave thedesired complex 28 in 62% yield by C-Si bond cleavage.The IR spectrum of 28 exhibits a vibrational frequency of1672 cm-1 for the CHO group. In the 1H NMR spectrum,the H3 proton is, as expected for an η5-Mn complex, themost deshielded and appears as a triplet at 5.95 ppm. It isworthy to note a deshielding effect of the H2 proton (doubletat 5.52 ppm) with respect to the H4 proton (triplet at 5.34

Figure 2. ORTEP view of complexes 21 and 2618 with thermal ellipsoids at the 30% probability level (insets show the correspondingchemical structures). Selected interatomic distances (A) in complex 21: Mn-C1 2.208(2); Mn-C2 2.129(2); Mn-C3 2.172(2); Mn-C4

2.211(2); Mn-C5 2.216(2).

Figure 3. Energies relative to the most stable regioisomer andνCO computed vibrational frequencies (in parentheses, reportedunscaled) and experimental vibrational frequencies (in bracketsin cm-1) for the three aldehyde derivatives. The most stableconformer is used and represented for each regioisomer.8d

Scheme 3. Synthesis of the Formyl Complex 28

5762 Organometallics, Vol. 28, No. 19, 2009 Eloi et al.

ppm) due to the electronic effect of the formyl group at theC1

carbon.Figure 3 now completed by the experimental IR value of

complex 28 (1672 cm-1) shows that the formyl group of theC2 regioisomer has the largest value (1710 cm-1) comparedto the two others. Thus, the electronic delocalization is betterwhen the CHO group is linked to the C1 and C3 carbonsrather than to theC2 carbon, and the frequency shift betweenC2 and C1 carbons amounts to 38 cm-1, very close to thecomputed 41 cm-1. These experimental data are in excellentagreement with the computed results reported in Figure 3.The same observation can be made for the ester derivatives18, 22, and 15. Indeed the experimental IR value of the estergroup of complex 22 (1725 cm-1) is the highest one com-pared to that of the two other regioisomers: C1 isomer, 1697cm-1; C3 isomer, 1688 cm-1.

Conclusion

Our results show that when a bromo-arene is substitutedby electron-donor groups, it can be easily coordinated to aMn(CO)3

þ entity to deliver unprecedented complexes. Thus,we successfully developed the synthesis of (η6-bromoarene)-Mn(CO)3

þ substituted by methoxy and silylated groups ingood to excellent yields. Nucleophilic additions of LiAlH4 orPhMgBr deliver the corresponding neutral (η5-bromocyclo-hexadienyl)Mn(CO)3 complexes bearing a bromo group onthe π system, which were easily lithiated and functionalizedby ester or formyl groups using metal-halogen exchangereaction. This reaction, applied for the first time in theη5-Mncomplex series, is highly regioselective when the brominegroup is not adjacent to the ortho-directing group such as themethoxy and offers a useful complementary functionaliza-tion method to those previously reported, namely, the palla-dium cross-coupling and the lithiation/electrophilic quenchreactions. It is particularly important for the introduction ofsubstituents (i) at the C1 or C5 ends of the cyclohexadienylligand, which were difficult or even impossible to reach upto now, and (ii) at the “meta” position with respect to anortho-directing group. The synthesis of the first (η5-cyclohexadienyl)Mn(CO)3 complexes substituted at the C1

position by a formyl group and the X-ray structure of one ofthem confirmed that the structural and energetical data arein excellent agreement with the computed results alreadyreported.

Experimental Section

General Methods. All reactions were routinely performedunder a dry nitrogen atmosphere using standard Schlenk tech-niques. THF and Et2O were dried over sodium benzophenoneketyl and distilled. CH2Cl2 and DMF were distilled over CaH2.NMR spectra were recorded on a Bruker ARX 200 MHz orAvance 400 MHz spectrometer. 1H and 13C signals of NMRsolvents were used as internal standards respectively at δ=7.26ppm and δ=77.36 ppm inCDCl3 and at δ=2.09 ppm and δ=30.60 ppm in acetone-d6. The Mn(CO)3 carbonyl signal isknown to be difficult to observe, especially when only lowquantities of complex are available. Infrared spectra weremeasured on a Bruker Tensor 27 spectrometer. Elementalanalyses were performed by the Service de Microanalyses del’Universit�e Pierre etMarie Curie.Mass spectra were performedby theGroupe de Spectrom�etrie deMasse (UMR7613,UPMC).

Complexes 2a, 2b, 2c, 4, and 6were obtained by the silver saltprocedure used for the preparation of complexes 1a and 1b.13

BrMn(CO)5 and AgBF4 in a 1:1 ratio were dispersed inCH2Cl2 and refluxed for 3 h. One equivalent of the free arenewas then added at room temperature, and the solution washeated again for 20 h. After a usual workup the pale yellow solidobtained was dissolved in a minimum of acetone and precipi-tated when poured in 400 mL of Et2O.

Complex 2a. Yield: 69%. IR (ATR Diamant): 1997(Mn(CO)3

þ); 2071 (Mn(CO)3þ) cm-1. 1H NMR ((CD3)2CO,

200MHz):δ 4.35 (3H, s,OMe); 6.34 (1H, t,H5, J=6.5Hz); 6.77(1H, d,H3, J=6.5Hz); 7.08 (1H, t, H4, J=6.5Hz); 7.63 (1H, d,H6, J= 6.5 Hz) ppm. 13C NMR ((CD3)2CO, 100 MHz): δ 60.8(OMe); 82.1 (C3); 92.0 (C5); 105.2 (C4); 109.6 (C6); 131.5 (C1);148.5 (C2) ppm. HRMS (ESI, positive mode): m/z 324.8909(calcd for C10H7BrMnO4

þ: 324.8903). Anal. Calcd forC10H7BrMnO4BF4: C, 29.10; H, 1.71. Found: C, 29.21; H, 1.86.

Complex 2b. Yield: 79%. IR (ATR Diamant): 2014(Mn(CO)3

þ); 2075 (Mn(CO)3þ) cm-1. 1H NMR ((CD3)2CO,

200MHz): δ 4.31 (3H, s, OMe); 6.45 (1H, d, H4, J=7Hz); 6.72(1H, d,H6, J=7Hz); 6.99 (1H, s,H2); 7.32 (1H, t, H5, J=7Hz)ppm. 13CNMR ((CD3)2CO, 100MHz): δ 60.2 (OMe); 82.4 (C4);88.0 (C2); 94.0 (C6); 123.8 (C1); 132.5 (C5); 151.7 (C3) ppm.Anal.Calcd for C10H7BrMnO4BF4: C, 29.10; H, 1.71. Found: C,29.28; H, 1.83.

Complex 2c. Yield: 76%. IR (ATR Diamant): 2012(Mn(CO)3

þ); 2032 (Mn(CO)3þ), 2087 (Mn(CO)3

þ) cm-1. 1HNMR ((CD3)2CO, 200MHz): δ 4.17 (3H, s, OMe); 6.53 (2H, d,H3 þH5, J= 7.1 Hz); 7.47 (2H, d, H2 þH6, J= 7.1 Hz) ppm.13CNMR ((CD3)2CO, 100MHz): δ 59.9 (OMe); 85.2 (C3þC5);91.8 (C1); 108.1 (C2þ C6); 149.7 (C4) ppm. Anal. Calcd for C10-H7BrMnO4BF4: C, 29.10; H, 1.71. Found: C, 29.31; H, 1.75.

Complex 4. Yield: 85%. IR (ATR Diamant): 2010(Mn(CO)3

þ); 2073 (Mn(CO)3þ) cm-1. 1H NMR ((CD3)2CO,

200 MHz): δ-0.58 (9H, s, SiMe3); 6.91 (2H, m, H5 þH6); 7.35(2H, m, H2 þ H4) ppm. 13C NMR ((CD3)2CO, 100 MHz):δ -1.1 (SiMe3); 102.8 (C5); 105.6 (C6); 106.9 (C4); 109.4 (C2);111.6 (C3) ppm. HRMS (ESI, positive mode): m/z 366.9193(calcd for C12H13BrMnO3Si

þ, 366.9192).Complex 6. Yield: 68%. IR (ATR Diamant): 2008

(Mn(CO)3þ); 2035 (Mn(CO)3

þ), 2076 (Mn(CO)3þ) cm-1. 1H

NMR ((CD3)2CO, 200MHz): δ 4.15 (3H, s, OMe); 6.42 (2H, d,H3 þ H5, J = 6.9 Hz); 7.48 (2H, d, H2 þ H6, J = 6.9 Hz)ppm. 13CNMR ((CD3)2CO, 100MHz): δ 55.2 (C1); 59.7 (OMe);85.9 (C3 þ C5); 113.8 (C2 þ C6); 150.3 (C4) ppm. HRMS (ESI,positive mode): m/z 372.8768 (calcd for C10H7IMnO4

þ,372.8764).

Typical Procedure for the Hydride Addition to η6 Cationic

Complexes. To a suspension of η6 complex (1 equiv) in THFcooled at -78 �C was slowly added LiAlH4 (1 equiv). After 5min stirring at-78 �C, the mixture was slowly warmed to roomtemperature. After 5 min, the crude mixture was hydrolyzedwith water, and the aqueous layer was extracted with diethylether. The combined organic layers were washed with water,then brine, and dried over magnesium sulfate. After filtrationover Clarcel and evaporation of the solvents, the mixture waspurified by flash chromatography on silica gel.

Complex 7a-H. Yield: 65%. IR (ATR Diamant): 1930(Mn(CO)3); 2012 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 3.72 (1H, d, H6exo, J = 12 Hz); 3.21 (2H, m, H5 þH6endo); 3.89 (3H, s, OMe); 4.74 (1H, tapp, H

4, J = 7 Hz); 5.67(1H, d,H3, J=7Hz) ppm. 13CNMR (CDCl3, 100MHz): δ 39.4(C6); 51.3 (C1); 55.9 (OMe); 56.5 (C5); 62.7 (C3); 93.1 (C4); 140.3(C2) ppm. HRMS (ESI, positive mode): m/z 348.8875 ([Μ þNa]þ, calcd for C10H8BrMnNaO4

þ, 348.8879).Complex 8b-H. Yield: 81%. IR (ATR Diamant): 1916

(Mn(CO)3); 2011 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 2.26 (1H, d, H6exo, J = 12.0 Hz); 2.76 to 2.83 (2H,m,H6endoþH1); 3.24 (1H, dt, H5, J=1.8 and 4.1Hz); 3.48 (3H,s, OMe); 6.17 (1H, t, H3, J = 1.8 Hz) ppm. 13C NMR (CDCl3,

(18) Eloi, A.; Rose-Munch, F.; Jonathan, D.; Tranchier, J.-P.; Rose,E. Organometallics 2006, 25, 4554.

Article Organometallics, Vol. 28, No. 19, 2009 5763

100 MHz): δ 29.8 (C6); 36.5 (C1); 54.9 (OMe or C5); 55.1 (C5 orOMe); 73.0 (C3); 101.2 (C2); 141.2 (C4) ppm. HRMS (ESI,positive mode): m/z 348.8874 ([Μ þ Na]þ, calcd for C10H8-BrMnNaO4

þ, 348.8879). Anal. Calcd for C10H8BrMnO4: C,36.73; H, 2.47. Found: C, 36.39; H, 2.61.Complex 7c-H. Yield: 85%. IR (ATR Diamant): 1928

(Mn(CO)3); 2015 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 2.72 (1H, d, H6exo, J = 12.0 Hz); 3.18 (2H, m, H5 þH6endo); 5.31 (1H, dd, H2, J=2.0 and 6.0 Hz); 5.66 (1H, dd, H3,J= 2.0 and 6.0 Hz) ppm. 13C NMR (CDCl3, 100 MHz): δ 37.3(C6); 38.4 (C5); 55.0 (OMe); 65.2 (C3); 74.4 (C1); 94.2 (C2); 144.4(C4) ppm. HRMS (ESI, positive mode): m/z 348.8876 ([Μ þNa]þ, calcd for C10H8BrMnNaO4

þ, 348.8879).Typical Procedure for the Grignard Addition to η6 Cationic

Complexes. To a suspension of η6 complex (1 equiv) in THFcooled at 0 �Cwas slowly addedPhMgCl (1.5 equiv). After 5minstirring at -78 �C, the mixture was slowly warmed to roomtemperature. After 5 min, the crude mixture was hydrolyzedwith water, and the aqueous layer was extracted with diethylether. The combined organic layers were washed with water,then brine, and dried over magnesium sulfate. After filtrationover Clarcel and evaporation of the solvents, the mixture waspurified by flash chromatography on silica gel.Complex 8b-Ph. Yield: 82%. IR (ATR Diamant): 1912

(Mn(CO)3); 2008 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 3.38 (1H, dt, H5, J = 1.8 and 6.0 Hz); 3.51 (3H, s,OMe); 3.75 (1H, dt,H1, J=1.8 and 6.0Hz); 3.97 (1H, t, H6, J=6.0 Hz); 6.04 (1H, t, H3, J=1.8 Hz); 6.90 to 6.94 (2H, m, HPh);7.17 to 7.29 (3H, m, HPh) ppm. 13C NMR (CDCl3, 100MHz): δ44.2 (C5); 45.0 (C6); 55.0 (OMe); 61.2 (C1); 72.6 (C3); 100.7 (C2);125.6 (CPh); 127.4 (CPh); 128.9 (CPh); 140.6 (C4); 146.8 (CPh)ppm. HRMS (ESI, positive mode): m/z 424.9198 ([Μ þ Na]þ,calcd for C16H12BrMnNaO4

þ, 424.9192).Complex 7c-Ph. Yield: 94%. IR (ATR Diamant): 1924

(Mn(CO)3); 2010 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 3.45 (3H, s, OMe); 3.54 (1H, d, H6, J = 5.8 Hz); 4.40(1H, d, H5, J=5.8 Hz); 5.35 (1H, d, H2, J=6.1 Hz); 5.58 (1H,d, H3, J = 6.1 Hz); 7.01 to 7.26 (5H, m, HPh) ppm. 13C NMR(CDCl3, 100MHz): δ 46.1 (C6); 53.8 (C5); 55.0 (OMe); 66.5 (C3);67.2 (C1); 95.4 (C2); 126.4 (CPh); 127.9 (CPh); 128.9 (CPh); 141.9(C4); 144.1 (CPh) ppm. HRMS (ESI, positive mode): m/z424.9195 ([ΜþNa]þ, calcd for C16H12BrMnNaO4

þ, 424.9192).Complex 9b-Ph. Yield: 69%. IR (ATR Diamant): 1928

(Mn(CO)3); 2010 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 0.51 (9H, s, SiMe3); 3.86 (1H, tapp, H

5, J = 7.0 Hz);4.33 (1H, d, H6, J= 7.0 Hz); 4.82 (1H, d, H4, J= 7.0 Hz); 5.31(1H, s, H2); 7.06 to 7.31 (5H, m, HPh) ppm. 13C NMR (CDCl3,100 MHz): δ-0.5 (SiMe3); 51.0 (C

6); 64.1 (C5); 97.7 (C4); 101.6(C2); 126.7 (CPh); 128.0 (CPh); 128.8 (CPh); 144.4 (CPh) ppm.HRMS (ESI, positive mode): m/z 466.9485 ([Μ þ Na]þ, calcdfor C18H18BrMnNaO3Si

þ, 466.9481).Complex 10b-Ph. Yield: 23%. IR (ATR Diamant): 1923

(Mn(CO)3); 2011 (Mn(CO)3) cm-1. 1H NMR (CDCl3, 200MHz): δ 0.19 (9H, s, SiMe3); 3.34 (1H, t, H6, J = 6.5 Hz);3.93 (2H,m,H1þH5); 5.93 (1H, s,H3); 6.89 to 7.22 (5H,m,HPh)ppm. 13CNMR (CDCl3, 100MHz): δ-1.8 (SiMe3); 44.5 (C

1 orC5); 60.7 (C6); 62.1 (C5 or C1); 86.4 (C3); 104.2 (C2); 104.8 (C4);125.9 (CPh); 127.4 (CPh); 128.9 (CPh); 147.3 (CPh) ppm. HRMS(ESI, positive mode): m/z 466.9484 ([Μ þ Na]þ, calcd forC18H18BrMnNaO3Si

þ, 466.9481).Typical Procedure for Lithium-Bromide Exchange Followed

by Electrophilic Quench. nBuLi (3 equiv) was dropped in a THFsolution cooled to -78 �C. Then a solution of η5 bromo-substituted complex (1 equiv) in THF was very slowly added,giving rise to a deep yellow-orange solution, which was stirred at-78 �C for 10 min. The electrophile (DMF or ClCO2Et, 3.5equiv) was added, and the solution was very slowly warmed toroom temperature. The crude mixture was hydrolyzed withwater, and the aqueous layer was extracted with diethyl ether.The organic layers were washed with water, then brine, and

dried over magnesium sulfate. After filtration over Clarcel andevaporation of the solvents, the mixture was purified by flashchromatography on silica gel.

Complexes 14 and 15. Yield: 72%.Complex 14. Yield: 63%. IR (ATR Diamant): 1685 (CO2Et);

1918 (Mn(CO)3); 2014 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.28 (3H, t, CH3, J= 7.1 Hz); 2.14 (1H, d, H6exo, J=12.0 Hz); 3.13 (1H, dd, H6endo, J= 7.0 and 12.0 Hz); 3.31 (1H,tapp, H

5, J=7.0Hz); 3.87 (3H, s, OMe); 4.20 (2H,m, CH2); 4.91(1H, tapp, H

4, J=7.0Hz); 5.73 (1H, d,H3, J=7.0Hz) ppm. 13CNMR (CDCl3, 100 MHz): δ 14.5 (CH3); 28.1 (C6); 37.8 (C1);55.8 (OMe); 56.9 (C5); 61.1 (CH2); 65.2 (C3); 94.6 (C4); 147.5(C2); 160.4 (CO ester) ppm. HRMS (ESI, positive mode): m/z342.9987 ([Μ þ Na]þ, calcd for C13H13MnNaO6

þ, 342.9985).Complex 15. Yield: 9%. IR (ATR Diamant): 1688 (CO2Et);

1936 (Mn(CO)3); 2023 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.40 (3H, m, CH3); 2.13 (1H, d, H6exo, J = 12.0 Hz);3.14 (2H, m, H1 þH6endo); 3.40 (1H, tapp, H

5, J= 6.8 Hz); 3.78(3H, s, OMe); 4.33 (2H, m, CH2); 5.51 (1H, d, H4, J = 6.8 Hz)ppm. 13CNMR(CDCl3, 100MHz):δ 14.3 (CH3); 27.1 (C

6); 44.3(C1); 61.5 (CH2); 62.0 (C3); 63.5 (OMe); 96.8 (C4); 110.3 (C2);166.6 (CO ester) ppm. HRMS (ESI, positive mode): m/z342.9983 ([Μ þ Na]þ, calcd for C13H13MnNaO6

þ, 342.9985).Complexes 16 and 17. Yield: 79%.Complex 16. Yield: 39%. IR (ATR Diamant): 1651 (CHO);

1924 (Mn(CO)3); 2018 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.93 (1H, d, H6exo, J=13.0 Hz); 3.24 (1H, dd, H6endo,J=6.0 and 13.0Hz); 3.42 (1H, tapp,H

5, J=6.0Hz); 3.86 (3H, s,OMe); 5.09 (1H, tapp, H

4, J= 6.0 Hz); 5.72 (1H, d, H3, J= 6.0Hz); 9.40 (1H, s, CHO) ppm. 13C NMR (CDCl3, 100 MHz): δ22.9 (C6); 49.2 (C1); 55.5 (OMe); 57.3 (C5); 65.2 (C3); 95.0 (C4);149.1 (C2); 191.2 (CHO) ppm. HRMS (ESI, positive mode):m/z298.9728 ([Μ þ Na]þ, calcd for C11H9MnNaO5

þ, 298.9723).Complex 17.Yield: 40%. Same spectroscopic data as in ref 8c.Complex 18. Yield: 54%. IR (ATR Diamant): 1697 (CO2Et);

1919 (Mn(CO)3); 2016 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.25 (3H, m, CH3); 2.05 (1H, d, H6exo, J = 12.1 Hz);3.17 (2H,m,H5þH6endo); 3.45 (3H s, OMe); 4.15 (2H,m, CH2);5.93 (2H, m, H2 þ H3) ppm. 13C NMR (CDCl3, 100 MHz): δ14.5 (CH3); 25.8 (C6); 38.8 (C5); 45.9 (C1); 54.8 (OMe); 61.0(CH2); 72.3 (C3); 98.6 (C2); 144.4 (C4); 170.6 (CO ester) ppm.HRMS (ESI, positive mode): m/z 342.9981 ([Μ þ Na]þ, calcdforC13H13MnNaO6

þ, 342.9985). Anal. Calcd forC13H13MnO6:C, 48.77; H, 4.09. Found: C, 48.65; H, 4.01.

Complex 19. Yield: 75%. IR (ATR Diamant): 1666 (CHO);1917 (Mn(CO)3); 2016 (Mn(CO)3) cm

-1. 1HNMR (CDCl3, 200MHz): δ 1.94 (1H, d, H6exo, J = 12.0 Hz); 3.20 (2H, m, H5 þH6endo); 3.50 (1H, s, OMe); 5.61 (1H, d, H2, J = 7.0 Hz); 6.04(1H, d, H3, J = 7.0 Hz); 8.82 (1H, s, CHO) ppm. 13C NMR(CDCl3, 100MHz): δ 22.7 (C6); 38.5 (C5); 55.2 (OMe); 70.5 (C1);74.1 (C3); 100.7 (C2); 145.3 (C4); 193.1 (CHO) ppm. HRMS(ESI, positive mode): m/z 298.9728 ([Μ þ Na]þ, calcd forC11H9MnNaO5

þ, 298.9723). Anal. Calcd for C10H8MnO5: C,47.85; H, 3.29. Found: C, 47.94; H, 3.33.

Complex 20. Yield: 60%. IR (ATR Diamant): 1683 (CO2Et);1930 (Mn(CO)3); 2020 (Mn(CO)3) cm

-1. 1HNMR (CDCl3, 200MHz): δ 1.26 (3H, m, CH3); 3.52 (3H, s, OMe); 3.66 (1H, d, H5,J = 6.8 Hz); 4.16 (2H, m, CH2); 4.43 (1H, d, H6, J = 6.8 Hz);5.90 (2H,m,H2þH3); 6.97 to 7.19 (5H,m,HPh) ppm. 13CNMR(CDCl3, 100 MHz): δ 14.5 (CH3); 40.8 (C6); 45.3 (C5); 55.1(OMe); 61.2 (CH2); 71.9 (C

3); 97.0 (C2); 126.1 (CPh); 127.2 (CPh);128.7 (CPh); 146.4 (CPh); 148.6 (C4); 170.3 (CO ester) ppm.HRMS (ESI, positive mode): m/z 419.0297 ([Μ þ Na]þ, calcdfor C19H17MnNaO6

þ, 419.0298).Complex 21. Yield: 81%. IR (ATR Diamant): 1655 (CHO);

1943 (Mn(CO)3); 2019 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 3.59 (3H, s, OMe); 3.71 (1H, d, H5, J = 7.2 Hz); 4.44(1H, d, H6, J=7.2 Hz); 5.57 (1H, d, H2, J=7.0 Hz); 5.89 (1H,d, H3, J=7.0Hz); 6.95 to 7.20 (5H, m, HPh); 8.95 (1H, s, CHO)ppm. 13C NMR (CDCl3, 100 MHz): δ 38.0 (C6); 44.3 (C5); 55.4

5764 Organometallics, Vol. 28, No. 19, 2009 Eloi et al.

(OMe); 63.7 (C1); 73.6 (C3); 99.0 (C2); 126.0 (CPh); 127.3 (CPh);128.8 (CPh); 145.2 (CPh); 145.9 (C4); 192.6 (CHO) ppm. HRMS(ESI, positive mode): m/z 375.0035 ([Μ þ Na]þ, calcd forC17H13MnNaO5

þ, 375.0036). Anal. Calcd for C17H13MnO5:C, 57.97; H, 3.72. Found: C, 58.06; H, 3.82.Complex 22. Yield: 64%. IR (ATR Diamant): 1725 (CO2Et);

1921 (Mn(CO)3); 2012 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.31 (3H, t, CH3, J= 7.1 Hz); 2.15 (1H, d, H6exo, J=11.3Hz); 2.86 (2H,m,H1þH6endo); 3.56 (3H, s OMe); 3.59 (1H,m, H5); 4.26 (2H, q, CH2, J= 7.1 Hz); 6.48 (1H, t, H3, J= 1.8Hz) ppm. 13CNMR (CDCl3, 100MHz): δ 14.3 (CH3); 24.6 (C

6);38.9 (C1); 55.1 (OMe); 55.3 (C5); 62.4 (CH2); 67.3 (C

3); 96.4 (C4);146.1 (C2); 167.6 (CO ester) ppm. HRMS (ESI, positivemode): m/z 342.9984 ([Μ þ Na]þ, calcd for C13H13MnNaO6

þ,342.9985).Complex 23. Yield: 82%. IR (ATR Diamant): 1705 (CHO);

1907 (Mn(CO)3); 2002 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 2.24 (1H, d, H6exo, J = 12.6 Hz); 2.98 (2H, m, H1 þH6endo); 3.36 (1H, m, H5); 3.58 (3H, s, OMe); 6.28 (1H, s, H3);9.20 (1H, s, CHO) ppm. 13C NMR (CDCl3, 100 MHz): δ 26.9(C6); 36.7 (C1); 53.7 (C5); 55.0 (OMe); 65.2 (C3); 101.1 (C4);143.4 (C2); 192.5 (CHO) ppm.HRMS (ESI, positive mode):m/z298.9725 ([Μ þ Na]þ, calcd for C11H9MnNaO5

þ, 298.9723).Complex 24. Yield: 55%. IR (ATR Diamant): 1725 (CO2Et);

1921 (Mn(CO)3); 2013 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 1.31 (3H, t, CH3, J=7.2Hz); 3.42 (1H, dt, H1, J=2.0and 5.9 Hz); 3.60 (3H, s, OMe); 4.10 (2H, m, H5 and H6); 4.26(2H, q, CH2, J = 7.2 Hz); 6.35 (1H, t, H3, J = 2.0 Hz); 6.88 to7.25 (5H, m, HPh) ppm. 13C NMR (CDCl3, 100 MHz): δ 14.3(CH3); 42.1 (C6); 44.2 (C1); 54.9 (OMe); 58.7 (C5); 62.4 (CH2);67.2 (C3); 94.9 (C4); 125.6 (CPh); 127.2 (CPh); 128.8 (CPh); 142.1(C2); 147.0 (CPh); 167.4 (CO ester) ppm. HRMS (ESI, positivemode): m/z 419.0292 ([Μ þ Na]þ, calcd for C19H17MnNaO6

þ,419.0298). Anal. Calcd for C19H17MnO6: C, 57.59; H, 4.32.Found: C, 57.21; H, 4.13.Complex 25. Yield: 79%. IR (ATR Diamant): 1709 (CHO);

1919 (Mn(CO)3); 2013 (Mn(CO)3) cm-1. 1HNMR (CDCl3, 200

MHz): δ 3.50 (1H, m, H1); 3.62 (3H, s, OMe); 3.88 (1H, dt, H5,J=1.7 and 6.1Hz); 4.15 (1H, t, H6, J=6.1Hz); 6.14 (1H, t, H3,J=1.7 Hz); 6.87 to 7.26 (5H, m, HPh); 9.29 (1H, s, CHO) ppm.13C NMR (CDCl3, 100 MHz): δ 42.0 (C6); 44.7 (C1); 55.1(OMe); 60.5 (C5); 64.7 (C3); 99.4 (C4); 125.5 (CPh); 127.5(CPh); 128.9 (CPh); 142.9 (C2); 146.7 (CPh); 192.7 (CHO) ppm.HRMS (ESI, positive mode): m/z 375.0035 ([Μ þ Na]þ, calcdfor C17H13MnNaO5

þ, 375.0036).

Complex 27. Yield: 66%. IR (ATR Diamant): 1666 (CHO);1930 (Mn(CO)3); 2021 (Mn(CO)3) cm

-1. 1HNMR (CDCl3, 200MHz): δ 0.36 (SiMe3); 3.94 (1H, tapp, H

5, J=6.9 Hz); 4.31 (1H,d,H6, J=6.9Hz); 5.16 (1H, d,H4, J=6.9Hz); 5.30 (1H, s,H2);6.88 to 7.11 (5H, m, HPh); 8.93 (1H, s, CHO) ppm. 13C NMR(CDCl3, 100 MHz): δ -0.7 (SiMe3); 36.1 (C6); 64.9 (C5); 66.8(C1); 91.4 (C3); 101.4 (C4); 104.7 (C2); 126.5 (CPh); 127.4 (CPh);128.7 (CPh); 145.6 (CPh); 193.7 (CHO) ppm. HRMS (ESI,positive mode): m/z 417.0328 ([Μ þ Na]þ, calcd forC19H19MnNaO4Si

þ, 417.0325). Anal. Calcd for C19H19MnO4-

Si: C, 57.86; H, 4.86. Found: C, 57.75; H, 4.71.Protodesilylation ofComplex 27: Synthesis of Complex 28. In a

two-neck flask, complex 27 (102 mg, 0.259 mmol, 1 equiv) wasdissolved at room temperature in 5 mL of THF. TBAF (0.4 mL,0.4mmol, 1.5 equiv)was added, and the pale yellow solutionwasstirred at room temperature for 5 min. Water (20 mL) wasadded, and the aqueous layer was extracted with diethyl ether(30 mL). The organic layers were washed with 50 mL of waterand 50 mL of brine and dried over magnesium sulfate, and thesolvents were removed. The crude mixture was then purified byflash chromatography on silica gel, affording complex 28 as ayellow solid (91 mg, 0.20 mmol, 62%).

Complex 28. Yield: 62%. IR (ATR Diamant): 1672 (CHO);1943 (Mn(CO)3); 2019 (Mn(CO)3) cm

-1. 1HNMR (CDCl3, 200MHz): δ 3.94 (1H, tapp, H

5, J=6.9Hz); 4.40 (1H, d, H6, J=6.9Hz); 5.34 (1H, tapp,H

4, J=6.9Hz); 5.52 (1H, d,H2, J=6.9Hz);5.95 (1H, tapp, H

3, J = 6.9 Hz); 6.96 to 7.26 (5H, m, HPh); 9.04(1H, s, CHO) ppm. 13C NMR (CDCl3, 100 MHz): δ 35.8 (C6);62.0 (C5); 64.1 (C1); 83.0 (C3); 98.6 (C4); 100.9 (C2); 126.2 (CPh);127.3 (CPh); 128.7 (CPh); 145.4 (CPh); 193.5 (CHO) ppm.HRMS(ESI, positive mode): m/z 344.9934 ([Μ þ Na]þ, calcd forC16H11MnNaO4

þ, 344.9930). Anal. Calcd for C16H11MnO4:C, 59.64; H, 3.44. Found: C, 59.49; H, 3.29.

Acknowledgment. This work was supported by theCNRS. We thank P. Herson (CIM2, UMR 7071, UnivParis 06) for the X-ray structure analyses and theEcole Normale Sup�erieure (Paris) for financial supportto A.E.

Supporting Information Available: Text giving X-ray crystal-lographic data for complexes 2c and 21 and the correspondingCIF files. Thismaterial is available free of charge via the Internetat http://pubs.acs.org.