Trialkyl imido niobium and tantalum compounds: synthesis, structural study and migratory insertion reactionsCCDC reference number 781634. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c0dt01449dThis paper is dedicated to the memory of Dr Amelio Vázquez de Miguel who died the last April 20, 2010 and whom we remember with affection.

Trialkyl imido niobium and tantalum complexes [MR3(NtBu)] (M = Nb, R = Me 2, CH2CMe33, CH2CMe2Ph 4, CH2SiMe35; M = Ta, R = Me 6, CH2CMe2Ph 7, CH2SiMe38) have been prepared by treatment of solutions containing [MCl3(NtBu)py2] (M = Nb 1a, Ta 1b) with three equivalents of magnesium reagent. By an unexpected hydrolysis reaction of the tris-trimethylsilylmethyl imido tantalum compound 8a, a μ-oxo derivative [(Me3SiCH2O)(Me3SiCH2)3Ta(μ-O)Ta(CH2SiMe3)2(NtBu)] (8a) was formed and its structure was studied by X-ray diffraction methods. Reactions of trialkyl imido compounds with two equivalents of isocyanide 2,6-Me2C6H3NC result in the migration of two alkyl groups, leading to the formation of a series of alkyl imido bisiminoacyl derivatives [MR(NtBu){C(R)NAr}2] (Ar = 2,6-Me2C6H3; M = Nb, R = Me 9, CH2CMe310, CH2CMe2Ph 11, CH2SiMe312, CH2Ph 13; M = Ta, R = CH2CMe314, CH2CMe2Ph 15, CH2SiMe316). All compounds were studied by IR and NMR (1H, 13C and 15N) spectroscopy. [ABSTRACT FROM AUTHOR]