Lewis base character of the phosphorus atom in phosphanido-niobocene complexes. Synthesis of new early-early homo- and heterobimetallic entities

The reaction of phosphanido complexes Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(PPh(2))] L = CO (1), CNXylyl (2)] with early transition metal halides in high oxidation states has been carried out. New bimetallic niobocene complexes {Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(5))] M = Nb, L = CO (3), L = CNXylyl (4); M = Ta, L = CO (5), L = CNXylyl (6)] have been successfully synthesized by the reaction with MCl(5)](2) (M = Nb or Ta). In a similar way {Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)}(μ-PPh(2))(MCl(4))] M = Ti, L = CO (13), CNXylyl (14); M = Zr, L = CO (15), CNXylyl (16)] were synthesized using MCl(4) (M = Ti or Zr). Solutions of complexes 4-6 in chloroform produced new ionic derivatives Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(H)Ph(2))(L)] MCl(6)] M = Nb, L = CO (7), L = CNXylyl (8); M = Ta, L = CO (9), L = CNXylyl (10)]. Ionic complexes Nb(η(5)-C(5)H(4)SiMe(3))(2)(P(Cl)Ph(2))(L)] NbCl(4)O(thf)] L = CO (11), CNXylyl (12)] were formed from solutions in thf - rapidly in the case of 3 but more slowly for 4. New heterometallic complexes Nb(η(5)-C(5)H(4)SiMe(3))(2)(L)(μ-PPh(2)){(Ti(η(5)-C(5)R(5))Cl(3)}] R = H, L = CO (17), CNXylyl (18); R = CH(3), L = CO (19), CNXylyl (20)] were synthesized by the reaction of 1 or 2 with Ti(η(5)-C(5)R(5))Cl(3)] (R = H or CH(3)). All of these compounds were characterized by IR and multinuclear NMR spectroscopy, and the molecular structures of 9 and 12 were determined by single-crystal X-ray diffraction.