Organometallics 1994,13, 3315-3323
3315
Azavinylidene and Azavinylidene-Bridged Compounds of Iridium and Rhodium Miguel A. Esteruelas,* Fernando J. Lahoz, Montserrat Olivh, Enrique Oiiate, and Luis A. Oro* Departamento de Quimica InorgCinica, Instituto de Cienciu de Materiales de Araghn, Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain Received March 31, 1994@
The synthesis of the azavinylidene and azavinylidene-bridged compounds Ir(=N=CPh& (diolefWPCy3) (6, diolefin = tetrafluorobenzobarreleneU"B); 6,diolefin = 1,5-cyclooctadiene (COD)) and [Ir@-N=CPhz)(diolefin)l2 (7,diolefin = COD; 8, diolefin = TFB) is described. The azavinylidene derivatives 6 and 6 were prepared by reaction of the corresponding squareplanar methoxy complex Ir(OMe)(diolefin)(PCy3)with benzophenone imine, whereas the azavinylidene-bridged 7 and 8 were similarly obtained from [Ir@-OMe)(diolefin)l~(diolefin = COD, TFB). The complexes 7 and 8 react with CO to give [Ir@N=CPh2)(C0)212 (91, which affords [Ir@-N=CPh2)(CO)(PCy3)12(10) in the presence of PCy3. The preparation of the related compounds [Rh$-N=CPh2)(diolefin)l2 (diolefin = COD (131, TFB (1411,[RhbN=CPh2)(C0)2]2 (E),Rh2$-N=CPhz)z(CO)sPCys (161,and [Rhb-N=CPh2)(CO)(PCy3)]2 (17) is also reported. The structure of 14 was determined by a n X-ra investigation. 14 crystallizes in the space group Pi with a = 16.468(5)A, b = 16.569(5) c = 18.139(5)A, a = 66.03(1)",/3 = 74.32(2)", y = 89.71(2)", and 2 = 4. The molecular structure reveals that the core of the molecule is formed by a Rh2N2 skeleton in a bent configuration.
1,
Introduction In contrast to the well-documented vinylidene (I) and vinylidene-bridged(11)complexes, which have been the subject of intensive studies in recent years,l little is known about the related azavinylidene (111)and azavinylidene-bridged (Iv> compounds with nitrogen instead of carbon in the a-position of the unsaturated ligands. R\
I
H
R\
111
/R C II
/R
C II
IV
The azavinylidene compounds previously reported are W,7 Re> R U ,and ~ Oslo complexes, S C ,Ti,3 ~ Zr,4 Cr,5 M o , ~ Abstract published in Advance ACS Abstracts, July 1, 1994. (1)Bruce, M. I. Chem. Rev. 1991,91,197. (2)Bercaw, J. E.; Davies, D. L.; Wolczanski, P. T. Organometallics 1986,5,443. (3)(a)Bochmann, M.; Wilson, L. M. J. Chem. Soc., Chem. Commun. 1986,1610. (b) Latham, I. A.;Leigh, G. J.; Huttner, G.; Jibril, I. J. Chem. Soc., Dalton Trans. 1986,377. (c) Bochmann, M.; Wilson, L. M.; Hursthouse, M. B. Motevalli, M. Organometallics 1988, 7,1148. (4)(a)Erker, G.;"berg, W.; Atwood, J. L.; Hunter, W. E. Angew. W.; Erker, G. J. Chem., Znt. Ed. Engl. 19&1,23,68. (b) "berg, Organomet. Chem. 1986,280,343. (c) Jordan, R. F.; Bajgur, C. 5.; Dasher, W. E.; Rheingold, A. L. Organometallics 1987,6,1041. (d) Erker, G.;"berg, W.; Krtiger, C.; Raabe, E. J.Am. Chem. Soc. 1988, 110,2400. (e) Woo, H. G.; Tilley, T. D. J. Organomet. Chem. 1990, 393,C6. (0Borkowsky, S. L.; Jordan, R. F.; Hinch, G. D. Organometallics 1991,10,1268. (g) Alelyunas, Y.W.; Jordan, R. F.; Echols, S. F.; Borkowsky, S. L.; Bradley, P. K Organometallics 1991,10,1406. @
which have been prepared in some of the following ~ays:~-lO (i) reaction of halogenhydridometal compounds with oximes in the presence of AgPFs, (ii) deprotonation of imine complexes, (iii) treatment of halogeno compounds with ketenimino derivatives such as LiN=CRR, NaN-CRR, and MesSi-N=CRR, (iv) exchange of an oximato ligand by reaction with an imine, (v) insertion of nitriles into M-H, M-C, and M-Si bonds, (vi) deprotonation of an imido ligand at a Cp atom, ( v i ) nucleophilic attack at a coordinated nitrile carbon, (viii) addition of CN- and Hf t o carbene compounds, and (ix)isomerization of azaallyl complexes. The formation of azavinylidene-bridged compounds has only been described in a few cases for Ti,ll Mn,12 Fe,13and Co.l4 In general, these compounds have been synthesized by reaction of dinuclear complexes with diazirines. (5)Barron, A. R.;Salt, J. E.; Wilkinson, G.; Motevalli, M.; Hursthouse, M. B. J. Chem. Soc., Dalton Trans. 1987,2947. (6) (a) Farmery, K.; m e r , M.; Midcalf, C. J. Chem. Soc. A 1970, 2279. (b) m e r , M.; Midcalf, C. J. Chem. Soc.A 1971,292.(c) Green, M.; Mercer, R. J.; Morton, C. E.; Orpen, A. G. Angew. Chem.,Znt. Ed. Engl. 1985,24,422. (7)(a) Colquhoun, H. M.; Crease, A. E.; Taylor, S. A.; Williams, D. J. J. Chem. SOC.,Dalton Trans. 1988,2781. (b)Maatta, E. A.; Du,Y. J.Am. Chem. Soc. 1988,110,8249. (c) Feng, 5.G.; Templeton, J. L. J. Am. Chem. Soc. 1989,111, 6477. (d) Debad, J. D.; Legzdine, P.; Batchelor, R. J.; Einstein, F. W. B. Organometallics 1992,11,6. (e) Feng, S. G.; Templeton, J. L. Organometallics 1992,11,1295.(0 Feng, S.G.; White, P. S.; Templeton, J. L. Organometallics 1993,12,2131. WChatt, J.; Dosser, R. J.; King, F.; Leigh, G. J. J. Chem. Soc., Dalton Trans. 1976,2436. (9)Werner, H.; Daniel, T.; Knaup, W.; Ntimberg, 0. J. Organomet. Chem. 1993,462,309. (10)(a)Werner, H.; Knaup, W.; Dziallas, M. Angew. Chem.,Znt. Ed. Engl. 1987,26, 248. (b) Daniel, T.; Mliller, M.; Werner, H. Znorg. Chem. 1991,30,3118. (c) Daniel, T.; Werner, H. 2.Naturforsch., B 1992,47,1707. (d) Daniel, T.; Knaup, W.; Dziallas, M.; Werner, H. Chem. Ber. 1993,126,1981.(d) Daniel, T.; Werner, H. J. Chem. SOC., Dalton Trans. 1994,221. (11)Melhdez, E.; Arif, A. M.; Ziegler, M. L.; Emst, R. D. Angew. Chem., Znt. Ed. Engl. 1988,27,1099. (12)Churchill, M. R.;Lin, K K G. Znorg. Chem. 1975,14,1675.
0276-7333/94/2313-3315$04.50/00 1994 American Chemical Society
3316 Organometallics, Vol. 13, No. 8,1994 We have previously reported that the reaction of the dimer [Ir@-OMe)(COD)12(COD = 1,5-cyclooctadiene) with PCy3 leads to the mononuclear Ir(OMe)(COD)(PCyd, which is a useful starting material for the synthesis of o-alkynyl, dihydrido silyl, and new alkoxy compounds.15 We have now observed that the reactions of Ir(0Me)(COD)(PCy3)and the related tetrafluorobenzobarrelene (TFB) derivative Ir(OMe)(TFB)(PCys)with benzophenone imine afford unusual iridium(1) compounds of formula Ir(=N=CPh2)(diolefin)(PCy3). Similarly, the reactions of the dimers [M@-OMe)(diolefin)l2(M = Ir, Rh) with benzophenone imine lead to [M@-N=CPh2)(dio1efin)lz(M = Ir, Rh). The present paper describes the preparation and characterization of these unusual azavinylidenes and azavinylidene-bridged compounds.
Results and Discussion Synthesis and Characterization of (Azavinylidene)iridium(I)Compounds. Similarly to the reaction of [I~~-OM~)(COD)IZ (1)with PCy3 to give Ir(0Me)(COD)(PCy3)(21, the reaction of [IdpOMe)(TFB)12(3) with the stoichiometric amount of PCy3 in methanol, after 30 min, leads to Ir(OMe)(TFB)(PCyd (41, which was isolated as an orange solid in 85% yield (eq 1). [lr(p-0Me)(TFB)ln + 2 PCy,
-
3
F 4
The 'H NMR spectrum of 4 is compatible with a square-planar structure, analogous to that of 2. It hows a singlet at 4.12 ppm due to the methoxy protons. The characteristic resonances of the diolefin are two broad signals at 5.29 and 3.59 ppm. The first signal is attributable to the tertiary CH protons and the second signal to the olefinic protons trans to the PCy3 group. The resonance due to the olefinic protons trans to the methoxy group is masked by the complex aliphatic resonances (2.00- 1.10 ppm) of the tricyclohexylphosphine ligand. The presence of the methoxy group is also supported by the IR spectrum in Nujol, which shows a band at 1035 cm-l assignable to v(C0). The 31P{1H} spectrum contains a singlet a t 19.2 ppm. The easy synthesis and stability of 2 and 4 allow the preparation of the azavinylidenes 5 and 6 (eq 2). Thus, treatment of 2 and 4 with benzophenone imine in hexane at room temperature affords orange solids in 36% and 60% yields, respectively. With regard to the spectroscopic data, there is no doubt that 5 and 6 have (13)(a)Brigth, D.;Mills, 0. S. J.Chem. Soc., Chem. Commun. 1967, 245. (b) Carty, A. J.; Madden, D. P.; Mathew, M.; P a l e d , G. J.; Birchall, T. J. Chem. Soc.,Chem. Commun. 1970,1664.(c) Andrianov, V. G.; Struchkov, Yu. T. Koord. Khim. 1978,4,937; Chem. Abstr. 1978, 89,121230~. (d) Klose, A.;Solari, E.; Ferguson, R.; Floriani, C.; ChiesiVilla, A.; Rizzoli, C. Organometallics 1993,12,2414. (14)Carofiglio, T.; Stella, S.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. J. Chem. Soc., Dalton Trans. 1989,1957. (15) (a) F e m h d e z , M. J.; Esteruelas, M. A.; Covarmbias, M.; Oro, L. A.; Apreda, M. C.; Foces-Foces, C.; Cano, F. H. Organometallics 1989,8,1158. (b) Fernhdez, M. J.; Esteruelas, M. A.; Covarrubias, M.; Oro, L. A. J. Organomet. Chem. 1990,381,275.
Esteruelas et al.
5
F
6
a square-planar geometry. The lH NMR spectrum of 5 shows two broad resonances a t 4.43 and 2.99 ppm, assigned to the vinyl protons of the 1,5-cyclooctadiene ligand trans t o PCy3 and N=CPh2, respectively. In agreement with this, the 13C{lH} N M R spectrum of 5 also shows two resonances due to the vinyl carbon atoms. The carbon atoms of the olefinic bond trans to PCy3 appear at 83.39 ppm as a doublet with a P-C coupling constant of 12.9 Hz, whereas the olefinic carbon atoms trans to N-CPh2 appear at 48.41 ppm as a singlet. The C-N carbon atom of the azavinylidene ligand was found a t 156.28 ppm as a doublet with a P-C coupling constant of 1.8 Hz. In the lH NMR spectrum of 6 the resonance due to the vinyl protons trans to N=CPh2 is masked by the aliphatic resonances of PCy3. However, in the 13C{lH}NMR spectrum, the resonance attributable to the corresponding olefinic carbon atoms can clearly be observed as a singlet a t 16.15 ppm. The olefinic carbon atoms trans to PCy3 appear a t 56.70 ppm as a doublet with a P-C coupling constant of 11.9 Hz. Similarly to the l3C{lH} NMR spectrum of 5, the l3C{IH} NMR spectrum of 6 shows the C=N carbon atom of the azavinylidene ligand at 157.90 ppm as a doublet with a P-C coupling constant of 1.4 Hz. In addition, it should be noted that the resonances due to the olefinic carbon atoms trans to the azavinylidene ligand appear at unusually high field. This is in agreement with the great n-donor power of the azavinylidene groups, which are generally viewed as three-electron-donor l i g a n d ~ . ~ " J ~ J ~ The presence of the azavinylidene ligand in 5 and 6 is also supported by the IR spectra of both compounds, which show a band at 1625 (5) and 1640 (6) cm-l assignable to v(C=N). Singlets at 12.02 (5) and 15.84 (6) ppm, in the 31P{1H}NMR spectra, are also characteristic of the new species. To the best of our knowledge, the only iridiumazavinylidene complex described so far is the pentamethylcyclopentadienyl-iridium(II1) derivative [Ir(v5C5Me5)(=N=CPh2)(PMetBuz)lPF6obtained by Werner et al. by reaction of Ir(7;15-C5Me5)C12(PMetBu2)with benzophenone imine in the presence of AgpF6.'Ob Therefore, our compounds are the first iridium(1) azavinylidene complexes, and the first examples of neutral iridium azavinylidene derivatives. Synthesis and Characterization of Azavinylidene-Bridged Iridium Compounds. The methoxy dimer complexes 1 and 3 react with the stoichiometric (16) Kilner, K. Adu. Organomet. Chem. 1972,10,115. (17)Chan, L.H.; Rochow, E. G. J. Organomet. Chem. 1967,9,231.
Organometallics, Vol. 13, No. 8, 1994 3317
Azavinylidene Compounds of Ir and Rh
Scheme 1
1 -
2 HN=CPh2
lco
. .
“
Ph
