Organometallics 1993,12, 381-388
381
Formation of $-Iminoacyl Compounds by Protonation of a Ketenimine Ligand in Bis( (trimethylsily1)cyclopentadienyl) Compounds of Niobium. Molecular Structures of [Nb (q5-C5H4SiMe3)2C1( q2( C,N) -EtPhHCCNPh)]+BF4- and [Nb(q5-C5H4SiMe3)2F( q2( C,N)-Ph2HCCNPh)]+BF4Antonio Antifiolo,+Mariano Fajardo,$ Raquel Gil-Sanz,* Carmen L6pez-Mardomingo,* Patricia Martin-Villa,$ Antonio Otero,'?t Marek M. Kubicki,§ Yves Mugnier,s S. El Krami,s and Y. Mourads Departamento de Qufmica Inorghnica, Orghnica y Bioqufmica, Facultad de Qufmicas, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain, Departamento de Qufmica Inorghnica and Departamento de Qulmica Orghnica, Campus Universitario, Universidad de Alcalh, 28871 Alcalh de Henares, Spain, and Laboratoire de S y n t h b e et d'Electrosynth2se Organometalliques associ6 au CNRS (URA 33), Facult6 des Sciences, 6 Boulevard Gabriel, 21000 Dijon, France Received June 11, 1992
Nb(q5-C5H4SiMe3)2X(q2(C,N)-R1R2CCNR3) (X = C1, Br) reacts with 1equiv of HBF4-OEt2 to give in one step the q2-iminoacylcomplexes [Nb(~-CsH4SiMe3)2X(~(C~-R1R2HCC~31 +BF4(1, X = C1, R1= R2 = R3 = C6H5(Ph); 2, X = Br, R1 = R2 = R3 = Ph; 3, X = F, R1 = R2 = R3 = Ph; 4, X = C1, R1 = R3 = Ph, R2 = C2H5 (Et); 5, X = Br, R1 = R3 = Ph, R2 = Et; 6, X = C1, R1 = R3 = Ph, R2 = CH3 (Me); 7, X = Br, R1 = R3 = Ph, R2 = Me; 8, X = C1, R1 = R2 = Ph, R3 = p-Br-C6H4;9, X = Br, R1 = R2 = Ph, R3 = p-Br-C&) through protonation a t the free terminus of the complexed ketenimine ligands. Complex 3 has also been isolated as both the N-outside and N-inside conformers in the three-step reaction (oxidation, F abstraction, and with 2 equiv of HBFcOEt2. protonation processes) of Nb(q5-CsH4SiMe3)~(q2(C,N)-Ph2CCNPh) The chemical (Na/Hg) and electrochemical one-electron reductions of complexes 1-9 yield the starting ketenimine complexeswith the evolution of H2. The structures of 3 and 4 were determined by single-crystal diffractometry. Com ound 3 crystallizes in the monoclinic space group P 2 d n with a = 11.004 (4) A, b = 17.702 (5) ,c = 18.679 (4) A, fl = 91.60 (2)", 2 = 4, V = 3637.3 A3, Pc&d = 1.358 g/mL, R = 0.051, and R, = 0.058 based on 6832 reflections. Com ound 4 crystallizes in the monoclinic space group C2/c with a = 23.962 (8) A, b = 21.408 (5) , c = 16.456 (3) A, fl = 123.30 (2)O, 2 = 8, V = 7055.5 A3,Pcdcd = 1.368 g/mL, R = 0.046, and R, = 0.048 based on 5856 reflections. The molecular structures show a typical bent-metallocene geometry around the niobium atom with an q2(C,N)-bonded iminoacyl ligand.
R
Introduction Insertion reactions of isocyanides into transition-metalcarbon bonds to give iminoacyl groups are commonly encountered in organometallic chemistry.' For early transition metals the most extensive studies have been reported on the spectroscopic and structural properties of the group 4 metal q2-iminoacyl derivatives.2 In contrast, the study of analogous group 5 metal complexes has been + Universidad t Universidad
de Castilla-La Mancha. de Alcalh. Laboratoire de SynthLe et d'Electrosynth8se Organometalliques. (1)(a) Singleton, E.; Oosthuizen, H. E. Adu. Organomet. Chem. 1983, 22,209. (b) Treichel, P. M. Adu. Organomet. Chem. 1983,11,21.(c) Durfee, L. D.; Rothwell, I. A. Chem. Reo. 1988,88,1059. (2)(a) Clark, R. J. H.; Stockwell, J. A.; Wilkins, J. D. J. Chem. SOC., Dalton Trans. 1976,120. (b) Lappert, M. F.; Luong Thi, N. T.; Milne, C. R.J.Organomet. Chem. 1979,174,C35. (c) Wolczanski,P. T.; Bercaw, J. E. J. Am. Chem. SOC.1979,101,6450.(d) Andersen, R. A. Inorg. Chem. 1979,18,2928.(e) De Boer, E. J. M.; Teuben, J. H. J . Organomet. Chem. 1979,166, 193. (0Bolhuis, F.; De Boer, E. J. M.; Teuben, J. H. J. Organomet. Chem. 1979,170, 299. (g) Dormond, A.; Dahchour, A. J. Organomet. Chem. 1980,193,321.(h) Klei, E.; Telgen, J. H.; Teuben, J. H. J. Organomet. Chem. 1981,209,297.(i) Reger, D. L.; Tarquini, M. K.; Lebioda, L. Organometallics 1983,2,1763. Fandos, R.; Meetama, A.; Teuben, J. H. Organometallics 1991,IO, 2665. (k) Martin, B. D.; Matchett, S. A,; Norton,J. R.; Anderson, 0. P. J . Am. Chem. SOC.1985, 107,7952. (1) Lubben, T. V.; Plbesl, K.; Norton, J. R.; Miller, M. M.; Anderson, 0. P. Organometallics 1992,11, 122.
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much less thorough. Several years ago, Wilkinson et reported the first tantalum iminoacyl complexes from the interactionsof Me,TaCl+, complexeswith the appropriate isocyanides, and recently several related complexes containing the ancillary aryloxide ligand have also been de~cribed.~A structurally characterized (iminoacy1)vanadocene complex has also been r e p ~ r t e d .To ~ date in the niobium chemistry only a few (iminoacy1)niobocene complexes, described by some of us,6J have been reported. One of those was specifically prepared from a neutral (3) Chiu,K.W.;Jones,R.A.;Wilkineon,G.;Galas,A.M.R.;Hursthouee, M. B. J. Chem. SOC., Dalton Trans 1981,2088. (4)(a) Chamberlain, L. R.; Durfee, L. D.; Fanwick, P. E.; Kobriger, L.; Latesky, S. L.; McMullen, A. K.; Rothwell, I. P.; Folting, K.; Huffman, J. C.; Streib, W. E.; Wang, R. J. Am. Chem. SOC.1987, 109,390. (b) McMullen, A. K.;Rothwell, I. P.; Huffman, J. C. J . Am. Chem. SOC.1985, 107,1072.(c) Latesky, S.L.; McMullen, A. K.; Niccolai, G.P.; Rothwell, I. P.; Huffman, J. C. Organometallics 1985,4,1896. (d) Chamberlain, L. R.; Rothwell, I. P.; Huffmann, J. C. J. Chem. Soc., Chem. Commun. 1986,1203. (5)Carrier, A. M.;Davidson, J. G.;Barefield, E. K.; Van Derveer, D. G. Organometallics 1987,6,454. (6)Martlnez de Ilarduya, J. M.; Otero, A,; Royo, P. J. Organomet. Chem. 1988,340,187. (7)Antiflolo, A.; Fajardo, M.; L6pez-Mardomingo, C.; Ohm, A.; Mourad, Y.; Mugnier, Y.; Sanz-Aparicio, J.; Fonseca, I.; Florencio, F. Organometallics 1990,9,1919.
0276-733319312312-0381$04.00/00 1993 American Chemical Society
Antinolo et al.
382 Organometallics, Vol. 12, No. 2, 1993
(ketenimine)niobium(IV)complex by means of a two-step process, as illustrated in eq 1. ,NPh (q5-C5H4SiMe3)2Nb\A NCPh, NPh (q5-CsH,SiMe3)2Nb
