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In Search of Cationic Germanium(II)−Transition Metal Complexes L2Ge+W(CO)5 and L2Ge+W(CO)4Ge+L2

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journal contribution
posted on 06.06.2005, 00:00 by Isabelle Saur, Sonia Garcia Alonso, Heinz Gornitzka, Virginie Lemierre, Anna Chrostowska, Jacques Barrau
New germanium(II)−tungsten complexes [L2(X)Ge]nW(CO)6-n (L2 = NPhC(Me)CHC(Me)NPh, n = 1, X = OTf (2); n = 2, X = Cl (13)) have been synthesized and characterized by X-ray crystallography. In compound 2 the triflate was found to be very weakly coordinating to the germanium in the solid state, and this result is confirmed by DFT calculations. All the spectroscopic data are consistent with the L2(X)Ge ligands being good σ-donors and poor π-acceptors in these complexes, similar to the phosphine ligands in homologous R3P complexes. Starting from the chlorogermanium(II)−tungsten complexes (L2(Cl)Ge)nW(CO)6-n (n = 1 (1), n = 2 (13)), metathesis reactions with halide or weakly coordinating anions A- (A- = TfO-, BPh4-, PF6-) have been investigated as a general approach to obtain the cationic germanium species [L2Ge+]nW(CO)6-n. In the case of A- = TfO-, spontaneous dissociation of the anion leading to an equilibrium between a neutral and a cationic tetracoordinated germanium species is observed in coordinating solvents. Treatment of L2(X)Ge with MX3 (M = Ga, X = Cl; M = In, X = I) afforded the neutral complexes L2MX2 (M = Ga (7) and In (8)) by ligand transfer reactions. The crystal structure of 8 was determined by X-ray structure analysis.