REACTIVITY OF NIOBOCENE DIHALOGENIDES TOWARD NITROSO DERIVATIVES - EPR AND IR CHARACTERIZATION OF THE FIRST NIOBIUM(IV) COMPLEXES CONTAINING AN ARNO-N,O LIGAND

The reaction of [Nb(eta(5)-C(5)H(4)R)(2)X(2)][1:R = SiMe(3), X = Cl; 2 : R = SiMe(3), X = Br; 3: R = H, X = Cl; 4: R = (t)Bu, X = Cl] with ni troso derivatives ArNO [a: Ar = Ph; b: Ar = o-CH3-C6H4; c: Ar = p-(CH3 )(2)NC6H4] yields paramagnetic complexes formulated as (eta(5)-C(5)H(4 )R)(eta(3)-C(5)H(4)R)X(2)(ArNO-N,O) 1a, 1b, 1c, 2a, 3a, 4a and 4c, whi ch have been characterized by ESR and IR spectroscopy.