The chemistry of niobium and tantalum dithiocarbamato-complexes. Part 1. Synthesis, structure, and protonation of dinitrogen-bridged complexes
Abstract
Convenient, ‘single pot’ syntheses of [{MCl3(thf)2}2(µ-N2)](M = Nb or Ta, thf = tetrahydrofuran), using (Me3Si)2NN(SiMe3)2 and Me3SiNHNHSiMe3 respectively, have been achieved. The reaction of these dinitrogen complexes with an excess of SiMe3(S2CNEt2) gives the corresponding [{M(S2CNEt2)3}2(µ-N2)], and the X-ray crystal structure of the complex with M = Nb has been determined. Treatment of the dithiocarbamato-complexes with an excess of anhydrous HX (X = Cl or Br) gives a stoicheiometric yield of hydrazine and the corresponding [M(S2CNEt2)3X2]; the crystal structure of one such example, M = Ta, X = Br, has been determined. Attempts to obtain crystals of [NbCl2(S2CNEt2)3] suitable for X-ray crystallographic analysis resulted in the isolation of [Nb(S2CNEt2)4]2[NbCl5S], whose identity was established crystallographically. Niobium-93 n.m.r. spectroscopy has been used to identify the nature of solution species in the reactions of [{Nb(S2CNEt2)3}2(µ-N2)] with acid.