Structure and dynamics of [Nb(η5C5H4SiMe3)2(η2-H2BR2)] (R2 = O2C6H4, C8H14, H2) complexes.: A combined experimental and theoretical study

Dihydrogen elimination from the reaction of the niobocene trihydride Cp'2NbH3 (Cp' = eta(5)-C5H4SiMe3) and the appropriate borane provides a synthetic route to the new borate-containing niobocene complexes [Nb(eta(5)-C5H4SiMe3)(2)(eta(2)-H2BR2)] (R-2 = O2C6H4 (1)r C8H14 (2), H-2 (3)). The reaction with H2BO2C6H4 or H2BC8H14 proceeds at mild temperature, and the BH3. THF adduct reacts even at low temperature. Complexes 2 and 3 show dynamic behavior in solution. Spectroscopic and theoretical studies were carried out in order to clarify these dynamic processes. In addition, X-ray diffraction studies of 2 were carried out and the results correlated with the theoretical data. Finally, reactions of Cp'Nb-2(H)(L) (L = CO, CN(2,6-Me2C6H3), (BuOOCH)-Bu-t=(CHCOOBU)-B-t) with BH3. THF give rise to the complex 3, with the elimination of the appropriate ancillary ligand L.