T H E S Y N T H E S I S OF S O M E : N E W

W I T H Q U I N O N E S

Vo S. K h a n d k a r o v a a n d S.

R H O D I U M v - C O M P L E X E S

P . G u b i n UDC 542.91 +541.49 +547.567 +546.97

A v-complex of a quinone, v-duroquinoneirontricarbonyl, was first obtained by the photochemical r e - action of Fe(CO)s with dimethylacetylene [1]. Already-made quinones were later used to synthsize ~-com- plexes [2~ Thus, it was shown that the reaction of Ni(CO)4 with duroquinone leads to the formation of b is - (v-duroquinone)nickel (0) [2]. Also, mixed v-complexes were obtained, where the second v-ligand was a bidentate cyclic diene [3, 4]. Mixed complexes of the ~-duroquinonemetal-v-cyclopentadienyl type have also been obtained for cobalt, rhodium, and iridium [5, 6]. Schrauzer concluded, on the basis of his experimen- tal resul ts , that not all quinones are capable of forming ~-complexes; only those whose v-acceptor ability is too small to oxidize the metal are good ligands. Thus, it was shown that unsubstituted benzoquinone-l,4 and toluquinone-l,4 do not give v-complexes with nickel, while t r imethyl- , 2,5-dimethyl-, and 2,6-dimethyl- benzoquinone-l,4 give, in the presence of cyclooctadiene-l ,5, the corresponding cyclooctadiene-l ,5-qui- none complexes of nickel [7, 8]. However, 2,3-dimethylbenzoquinone-l,4 oxidizes the nickel atom under similar reaction conditions.

In the present work, we describe the preparation of some new v-complexes of rhodium with quinones. We have shown that ~-complexes with 2,6-di-t-butylbenzoquinone-l,4 (I) can be obtained under the condi- tions described by Schrauzer for synthesizing v-duroquinonerhodium-v-cyclopentadienyl. The (I) is a stable, yellow, crystall ine substance which melts at 266-267 ~ (with decomposition). Under the same conditions, 1,4-naphthoquinone reacts with RhC13" 3H20 to form a blackish-red chloride complex. This complex reacts with C 5HsNa to form, among numerous other products, a small amount of an orange-yellow solid which con- talus metal and melts at 215 ~ (with decomposition). The infrared spectrum of this compound agrees sat is- factorily with that expected for v-naphthoquinone-l,4-rhodinm-v-cyclopentadienyl (n).* In the mixed com- plex, v-duroquinonerhodium-v-cyclopentadienyl, we replaced the cyclopentadienyl by v-indenyl and acetyl- acetonate. The reaction of v-duroquinonerhodium chloride with potassium indenyl, under the usual condi- tions for the formation of ~-cyclopentadienyl complexes [6], leads to the formation of v-duroquinonerho- dium-v-indenyl (m). The (II1) is an orange-yellow crystalline substance which melts at 282-284 ~ (with decomposition). When v-duroquinonerhodium chloride is heated with sodium acetylacetonate in alcoholic solution, NaC1 separates out and red, crystalline v-duroquinonerhodium acetylacetonate (IV) is formed.

All of the complexes obtained in the present work were character ized by IR and NMR spectra, which confirmed the s t ructures proposed. Thus, it was shown that it is possible to form ~-complexes with such quinones as 2,6-di-t-butylbenzoquinone-l,4 and naphthoquinone-l,4. It has been shown recently that unsub- stituted benzoquinone-l,4 also forms complexes when it reacts with molybdenum and tungsten carbonyls [9].

E X P E R I M E N T A L

The IR spectra were obtained for KBr pellets with a UR-10 apparatus. NMR spectra were taken on a JNM-4H-100 apparatus at a frequency of 100 MHz. Hexamethyldisiloxane was used as an internal stan- dard.

P r e p a r a t i o n o f v - C y c l o p e n t a d i e n y l r h o d i u m - 2 , 6 - d i - t - b u t y l b e n z o q u i n o n e - l , 4 (1).. A mixture of 3.0 g 2,6-di-t-butylbenzoquinone-l,4, 1.12 g RhC13 �9 3H20 , and 100 ml ethanol was boiled for 4 h in a flask fitted with a reflux condenser. The solvent was distilled off in vacuum and the residue freed from water by azeotropic distillation with benzene. The dry substance was washed several times

�9 The IR spectrum contains bands in the carbonyl region at 1660 and 1590 cm -1, and other bands at 3080, 1405, 1010, and 794 cm -1 which are character is t ic of the ~r-CsH ~ ring. Of interest is the absence of a band in the 1100 cm -~ region.

Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1898-1900, August, 1968. Original article sub- mitred February 22, 1968.

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with pe t ro l eum e ther (40-60~ Af te r drying, 1.3 g of an orange product was obtained. The LR spec t rum has C----O absorpt ion bands at 1667 and 1550 cm - i , while the C=O group of the s ta r t ing quinone absorbs ~:t 1657 and 1595 cm -I . To a solution of 1.2 g of the product in 200 ml absolute t e t r ahydro fu ran (THF) was added a solution of 0.0091 M sodium cyclopentadienyl (obtained f rom 0.35 g Na and 1 ml cyclopentadiene) in 30 ml absolute THF. Af te r 3 h the solvent was r e m o v e d in vacuo and the lus t rous dark brown res idue was washed s e v e r a l t imes with sma l l por t ions of CH2C12 (argon a tmosphere ) until the ex t rac t s r ema ined co lo r l e s s . Af te r separa t ion of the solvent , the res idue was r e c r y s t a l l i z e d f rom pe t ro l eum e ther (40-60~ Half a g r a m (38.5% of the theore t i ca l yield) of a yellow subs tance , melt ing at 266-267 ~ with decomposi t ion, was obtained. Found %: C 58.81, 58.92; H 6.60, 6.65. CigH25RhO 2. Calcula ted %: C 58.76; H 6.49.

The IR sp ec t rum had a b road band in the carbonyl region at 1638-1613 cm -1 which co r r e sponds to C=O absorpt ion in the coordinated quinone. The re were also bands at 3094, 1437, 1100, 1010, and 830 em -1 which a re c h a r a c t e r i s t i c of the V-ChH 5 r ing. The NMR spec t rum (CC14) had th ree s inglets with a ra t io of 18 :2 : 5. The signal with 6 = 1.19 ppm is due to the methyl protons of two t -bu ty l groups on the quinone. Two protons in the 3 and 5-posi t ions in the quinone give the s ignal with 5 = 5.2 ppm. The signal f r o m the five protons of the r -Cal l ~ is obs e rved at 5 = 5.53 ppm.

P r e p a r a t i o n o f v - D u r o q u i n o n e r h o d i u m - v - i n d e n $ 1 (Ill). To 1 .67gduroqu inone rhod ium chlor ide in 200 ml absolute dimethoxyethane was added 0.0094 tVi po ta s s ium indenyl (obtained f rom 0.366 g K and 1.7 ml indene) in 100 ml absolute dimethoxyethane (argon a tmosphere) . Af te r 5 h the solvent was s e p a r a t e d in vacuo and the o range-ye l low res idue was ex t rac ted with sma l l por t ions of CH2C12 in an argon a tmosphe re until the ex t r ac t r em a i ned co lo r l e s s . Af ter separa t ion of the solvent , the o range-ye l low r e s i - due was pur i f ied by ch roma tog raphy on an A1203 column in a CH2C12 sys tem. The (HI) was eluted with a 2 : 1 mix tu re of CH2C12 and THF. The yield of the o range-ye l low sol id was 1.90 g (90%). The m a t e r i a l for analys is was r e c r y s t a l l i z e d twice f r o m a 1 : 1 mix tu re of THF and hexane; mp 282-284 ~ (with decomposi t ion , begins to darken at 200~ Found %: C 59.58, 59.59; H 5.08, 5.01; Rh 26.75, 26.50. Cl~I1902Rh. Calcu la ted %: C 59.70; H 5.01; Rh 26.92.

In the NMR s p e c t r u m , the four protons in the s i x - m e m b e r e d ring give a mul t ipIet s ignal of the A2B 2 type with a cen te r at 6 = 7.19 ppm. The s ignals f rom the th ree protons of the f i v e - m e m b e r e d r ing have the shape c h a r a c t e r i s t i c of an A2B sys tem: two equivalent protons give a s ignal with a cen te r at 6 = 5.596 ppm, and one proton at 6 = 5.37 ppm. The sp in-sp in coupling constant JAB is 2 Hz. The twelve equivalent p r o - tons of the duroquinone methyl groups give a s inglet at 6 = 1.82 ppm~

P r e p a r a t i o n o f ~ - D u r o q u i n o n e r h o d i u m A c e t y l a c e t o n a t e (IV). A m i x t u r e o f 0 . 5 g duroquinonerhodium chloride and 0.21 g sodium ace ty lace tonate in 75 ml ethanol was heated in a l lask fi t ted with a ref lux condenser for 5 h in an a rgon a tmosphere . The solvent was r e m o v e d under vacuum. The d ry r ed subs tance was ex t rac ted s e v e r a l t imes with benzene. The benzene ex t r ac t s were evapora ted in vacuo. The resul t ing r o s e - r e d , c rys ta l l ine product was obtained with a 43% yield (0.26 g). The compound was r e c r y s t a l l i z e d f rom pe t ro l eum e ther (40-60~ mp 233-234 ~ (with decomposi t ion , begins to darken at 210~ Found %: C 48.87, 48.94; H 5.24, 5.34; Rh 27.77, 27.98. CihH1904Rh. Calcula ted %: C 49.19; H 5.23; Rh 28.10. In the NMR s p e c t r u m , * the twelve equivalent protons of the duroquinone methyl groups give a s ing - let at 6 = 1.63 ppm; the six equivalent methyl protons of the ace ty lace tonate give a s inglet at 5 = 1.96 ppm; and the cen t ra l proton in the ace ty lace tonate group gives a s inglet at 6 = 5.22 ppm.

The authors thank G. A. Nikiforov for the gift of 2 ,6 -d i - t -bu ty lbenzoqu inone- l ,4 and I. F. Leshchevaya for taking and discuss ing the NMR spec t ra .

C O N C L U S I O N S

New ~-complexes of rhodium with quinones were p r e p a r e d and the i r s t r u c t u r e s were de termined.

le 2. 3. 4. 5. 6.

L I T E R A T U R E C I T E D

H. W. S te rnberg , R. Markby, and J. Wender , J. A m e r . Chem. Soc., 80, 1009 (1958). G. N. Sch rauze r and H. Thyre t , J. Amer . Chem. Soc., 82, 6420 (1960). G. N. Sch rauze r and H. Thyre t , Z. Na tu r fo r sch . , 17b, 73 (1962). G. N. Seh rauze r , Advances in Organometa l l ic C h e m i s t r y , 2 , Academic P r e s s , New York (1964). G. N. Schrauze r and H. Thyre t , Angew. Chemie , 75,641 (1963). G. N. Sch ranze r and K. C. Dewhirs t , J. Amer . Chem. Soc. , 86, 3265 (1964).

*The NMR spec t rum was taken on a Hitachi 60-H at a f requency of 60 MHz.

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7e 8. 9.

G. N. Schrauzer and H. Thyret, Chem. Ber., 96, 1755 (1963). G. N. Schrauzer and H. Thyret, Angew. Chemie, 74, 488 (1962). F. Calderazzo and R. Henzi, J. Organometal. Chem., 10, 483 (1967).

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