Zusammenfassung
The reaction of [Cp-2*NbCl2] (Cp* = eta (5)-C5Me5) with KOH or Ba(OH)(2).8H(2)O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp-2*Nb(=O)H] (1), the new compound [Cp-2*Nb(=O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp-2*Nb(=O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp-2*Nb(=O){OC(O)NHPh}] (4). Complexes 3 and 4 were ...
Zusammenfassung
The reaction of [Cp-2*NbCl2] (Cp* = eta (5)-C5Me5) with KOH or Ba(OH)(2).8H(2)O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp-2*Nb(=O)H] (1), the new compound [Cp-2*Nb(=O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp-2*Nb(=O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp-2*Nb(=O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either eta (1)-S-thiocarbamato (3) or eta (1)-O-carbamato ligand (4) along with a terminal Nb=O group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp-2*NbH{OC(O)NPh}] (5) along with some 4. The molecular structure of 5 contains a niobocene unit comprising eta (2)-N,O-carbamato chelate, which formally is a [2 + 2] cycloaddition product of the Nb=O group and the heterocumulene. A hydride ligand completes the coordination sphere around Nb. Reaction of l with excess PhNCO gave a mixture of heterocycles (PhNCO)(2) (6) and (PhNCO)(3) (7) in the approximate ratio 3:2. By contrast, the reaction of [Cp-2*Nb(=O)OMe] with PhNCO in molar ratios from 1:3 to 1:100 gave nearly pure triphenylisocyanurate 7. (C) 2001 Published by Elsevier Science B.V.
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