Synthesis, Characterization, and Reactivity of Isocyanidephosphidoniobocene Derivatives: X-ray Diffraction Structures of New Isocyanideniobocene Complexes, [Nb(η⁵-C₅H₄SiMe₃)₂(CNR)(PMePh₂)]I, R = Xylyl, Cy

The reaction of the hydride niobocene complexes [Nb(η5-C5H4SiMe3)2H(L)] [L = CNBun (1), CNCy (2), and CNXylyl (3)] with ClPPh2 yielded the cationic niobocene complexes [Nb(η5-C5H4SiMe3)2(PHPh2)(L)]Cl [L = CNBun (4), CNCy (5), and CNXylyl (6)]. Treatment of these complexes with NaOH yielded a new family of phosphidoniobocene derivatives [Nb(η5-C5H4SiMe3)2(PPh2)(L)] [L = CNBun (7), CNCy (8), and CNXylyl (9)] by elimination of the hydrogen atom directly bonded to the phosphorus. The cationic d2 species [Nb(η5-C5H4SiMe3)2(PRPh2)(L)]X [R = Me, X = I, L = CNBun (10), CNCy (11), and CNXylyl (12); R = CH2Ph, X = Br, CNBun (13), CNCy (14), and CNXylyl (15); R = CH2CH2Ph, X = Br, CNBun (16), CNCy (17), and CNXylyl (18)] were prepared by the reaction of alkyl halides RX (R = Me, X = I; CH2Ph, X = Br; CH2CH2Ph, X = Br) with 7, 8, or 9 by electrophilic attack on the phosphorus atom present in the phosphido terminal ligand. In the same way, the reaction of 9 with ICH2CH2I or iodine yielded the complex [Nb(η5-C5H4SiMe3)2(P(I)Ph2)(CNXylyl)]I3 (19). The insertion reaction of carbon disulfide into the Nb−P bond of 7, 8, or 9 yielded a new family of diphenylphosphidodithioformato complexes with the niobocene system [Nb(η5-C5H4SiMe3)2(κ1-S-SC(S)(PPh2))(L)] [L = CNBun (20), CNCy (21), and CNXylyl (22)]. The molecular structures of 11 and 12 were determined by single-crystal X-ray diffraction studies.