Syntheses and reactivity of oxo niobocene complexes Cp*2Nb(O)X (X=H, OCH3) and crystal structures of [Cp*2Nb(OH)F]BF4 and Cp*2Nb(O)OC(O)H (Cp*=η5-C5Me5)
摘要:
Reaction of Cp-2*NbCl2 (Cp* = eta(5)-C5Me5) with KOH or Ba(OH)(2) . 8H(2)O in THF forms the complexes Cp-2*Nb(=O)X OC = Cl: 2, H: 3). The ratio of 2 and 3 depends on the stoichiometry. If NaOMe is added or MeOH in solution Cp-2*Nb(=O)OMe 4 is formed in good yields. Reactivity studies with 3 and 4 show that the Nb=O as well as the Nb-X unit behave as chemically active sites. Protonation of 3 or 4 with HBF4 is followed by an attack of fluoride (from BF4- anion) to give [Cp-2*Nb(OH)F]BF4 6 and [Cp-2*NbF2]BF4 7. In contrast the reaction of 3 or 4 with HCO2H results in an exchange of X- by formate to give Cp-2*Nb(=O)OC(O)H 8. The crystal structures of 6 and 8 are reported. Electrochemical investigations of 2-4 and 7, 8 reveal reaction pathways for the transformation of 1 into 3. (C) 1998 Elsevier Science S.A. All rights reserved.
Syntheses and reactivity of oxo niobocene complexes Cp*2Nb(O)X (X=H, OCH3) and crystal structures of [Cp*2Nb(OH)F]BF4 and Cp*2Nb(O)OC(O)H (Cp*=η5-C5Me5)
摘要:
Reaction of Cp-2*NbCl2 (Cp* = eta(5)-C5Me5) with KOH or Ba(OH)(2) . 8H(2)O in THF forms the complexes Cp-2*Nb(=O)X OC = Cl: 2, H: 3). The ratio of 2 and 3 depends on the stoichiometry. If NaOMe is added or MeOH in solution Cp-2*Nb(=O)OMe 4 is formed in good yields. Reactivity studies with 3 and 4 show that the Nb=O as well as the Nb-X unit behave as chemically active sites. Protonation of 3 or 4 with HBF4 is followed by an attack of fluoride (from BF4- anion) to give [Cp-2*Nb(OH)F]BF4 6 and [Cp-2*NbF2]BF4 7. In contrast the reaction of 3 or 4 with HCO2H results in an exchange of X- by formate to give Cp-2*Nb(=O)OC(O)H 8. The crystal structures of 6 and 8 are reported. Electrochemical investigations of 2-4 and 7, 8 reveal reaction pathways for the transformation of 1 into 3. (C) 1998 Elsevier Science S.A. All rights reserved.