Niobium(I) and tantalum(I) tetracarbonyl derivatives containing nitrogen ligands

Diamino derivatives of niobium(l) and tantalum(l) of general formula MX(CO)4(NN), MNb, Ta; XCl, 1; NNethylendiamine (en), N,N%dimethylethylendiamine (dmen), N,N,N%,N%-tetramethylethylendiamine (tmen), 2,2-dipyridyl (2,2%-dipy), 4,4%- dipyridyl (4,4%-dipy), have been prepared by oxidation of the [M(CO)6] anions with either 1,1%-dimethyl-4,4%-dipyridilium diiodide (methylviologen, mvI2) in the presence of the diamine or the diprotonated salt of the corresponding diamine, [(NN)H2]Cl2. Alternatively, these derivatives have been obtained by amine exchange reactions on [MCl(CO)4(4,4-dipy)]n or by chloride substitution on the dinuclear anion [Nb2(m-Cl)3(CO)8]. The MX(CO)4(NN) derivatives have been characterized by analytical, spectroscopic and, in the case of TaI(CO)4 (tmen), also by single crystal diffractometry. Crystal data. TaI(CO)4(tmen), monoclinic, space group P21:c (No. 14); a16.222 (5); b12.855 (3); c16.452 (6) A° , b117.67 (2)°, M536.10 g mol1; V3038.4 (1) A° 3; Z8; Dc2.344 g cm3; l0.7107 A° ; T203 K; m91.71 cm1; F(000)1984; R0.045; Rw0.048