Synthesis and structural features of novel vanadium(II) amides. X-ray structures of the octahedral [(2-C5H4N)(CH3)N]2V(TMEDA) (TMEDA = N,N,N',N'-tetramethylethylenediamine) and the square-pyramidal [2,5-(CH3)2C4H2N]2V(pyridine)3 (py = pyridine)

Abstract

The reaction of trans-(TMEDA)2VCl2 (TMEDA = N,N,N',N'-tetramethylethylenediamine) with both mono- and bidentate alkali-metal amides has been investigated. Utilization of 2 equiv of bidentate amide (N segment N)-M [M = Li, Na; N segment N = 2-?? (MeN)C5H4N (1), PhNNNPh (2), 7-azaindolyl (3), PhNCHCNPh (4), (C5H4N)2N (5)] led to the formation of the corresponding monomeric and octahedral (R2N)2V(TMEDA) species. A spontaneous dimerization reaction was obtained in the case of the acetanilide PhNC(Me)O ligand, allowing the isolation of the nearly diamagnetic dimer [PhNC(Me)O]4V2(TMEDA) (6). While the compounds obtained with monodentate amide showed a high tendency to disproportionate, an unusual square-pyramidal monomeric complex [2,5-(CH3)2C4H2N]2V(Py)3 (Py = pyridine) (9) was formed, in the case of the pyrrolyl derivative, under the usual reaction conditions, followed by in situ treatment of the reaction mixture with pyridine. Crystal data for 1 and 9 are as follows. 1 [T = 100 K, lambda(Mo K-alpha) = 0.71073 angstrom]: monoclinic, space group P2(1)/n, a = 10.075 (1) angstrom, b = 13.731 (2) angstrom, c = 15.102 (2) angstrom, beta = 108.50 (1)degrees, V = 1981.2 (5) angstrom 3, Z = 4, d(calcd) = 1.279 g cm-3, mu = 5.0 cm-1, F(000) = 812, R = 0.047 (R(w) = 0.066). 9 [T = 298 K, lambda(Mo K-alpha) = 0.71073 angstrom]: monoclinic, space group P2(1)/n, a = 11.072 (3) angstrom, b = 13.067 (1) angstrom, c = 17.251 (5) angstrom, beta = 92.85 (1)degrees, V = 2532 (1) angstrom 3, Z = 4, d(calcd) = 1.250 g cm-3, mu = 4.0 cm-1, F(000) = 1004, R = 0.047 (R(w) = 0.026).