Abstract
The preparation of a family of dinuclear monocyclopentadienyl imidoniobium and ‐tantalum complexes was achieved by two different synthetic routes. The diimido complexes [{M(Cp′)Cl~2~}~2~(μ‐1,i‐NC~6~H~4~N)] [Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, i = 4 (1); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, i = 3 (2); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, i = 2 (3); Cp′ = η^5^‐C~5~Me~5~, M = Nb, i = 4 (4); Cp′ = η^5^‐C~5~Me~5~, M = Nb, i = 3 (5); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Ta, i = 4 (6); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Ta, i = 3 (7)] were prepared by the reaction of one equivalent of the trichloro precursor [{MCl~3~}~2~(μ‐1,i‐NC~6~H~4~N)] (M = Nb, Ta, i = 4, 3 or 2) with two equivalents of either C~5~H~4~(SiMe~3~)~2~ or C~5~Me~5~(SiMe~3~). Complexes 1−7 can also be prepared by the reaction of two equivalents of [MCp′Cl~4~] (Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, Ta; Cp′ = η^5^‐C~5~Me~5~, M = Nb, Ta) with one equivalent of the corresponding aniline compound, N,N,N′,N′‐tetrakis(trimethylsilyl)‐1,4‐, ‐1,3‐, or ‐1,2‐phenylenediamine, respectively. The synthesis of [{Ta(Cp′)Cl~2~}~2~(μ‐1,i‐NC~6~H~4~N)] [Cp′ = η^5^‐C~5~Me~5~, i = 4 (8); Cp′ = η^5^‐C~5~Me~5~, i = 3 (9)] was only successful with the second preparative method. The reaction of 1, 2 and 8 with alkylating reagents gave the corresponding tetraalkyl derivatives, [{M(Cp′)R~2~}~2~(μ‐1,i‐NC~6~H~4~N)] [Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = Me, i = 4 (10); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = CH~2~SiMe~3~, i = 4 (11); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = CH~2~Ph, i = 4 (12); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = Me, i = 3 (13); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = CH~2~SiMe~3~, i = 3 (14); Cp′ = η^5^‐C~5~H~4~SiMe~3~, M = Nb, R = CH~2~Ph, i = 3 (15); Cp′ = η^5^‐C~5~Me~5~, M = Ta, R = Me, i = 4 (16); Cp′ = η^5^‐C~5~Me~5~, M = Ta, R = CH~2~SiMe~3~, i = 4 (17); Cp′ = η^5^‐C~5~Me~5~, M = Ta, R = CH~2~Ph, i = 4 (18)]. The alkylated complexes with other stoichiometries, [{M(Cp′)(Me)(X)}~2~(μ‐1,4‐NC~6~H~4~N)] [Cp = η^5^‐C~5~H~4~SiMe~3~, M = Nb, X = Cl (19); Cp = η^5^‐C~5~H~4~SiMe~3~, M = Nb, X = NMe~2~ (20); Cp = η^5^‐C~5~Me~5~, M = Ta, X = Cl (21)], were also prepared. The molecular structures of complexes 1, 8 and 17 were determined by single‐crystal X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)