Syntheses, Structures, and Reactivity of a Series of (Pentamethylcyclopentadienyl)molybdenum(V) and -tungsten(V) Imido Complexes

Reactions of the (pentamethylcyclopentadienyl)molybdenum(V) and -tungsten(V) tetrachlorides (η 5 -C 5 Me 5 )MCl 4 (M = Mo, W) with the primary amines RNH 2 (R = t- Bu, i -Pr, C 6 F 5, and 2,6-( i -Pr) 2 C 6 H 3 ) lead to the formation of the imido complexes [(η 5 -C 5 Me 5 )M(NR)Cl 2 ] ( 3a − h ). X-ray structure analyses of 3a, 3c, and 3e reveal their monomeric nature. 3c and 3e crystallize in the monoclinic space group P 2 1 / c with the lattice parameters a = 15.171(3) Å, b = 7.615(2) Å, c = 14.758(3) Å, β = 90.29(3)°, and V = 1704.9(7) Å 3 for 3e and a = 10.4502(7) Å, b = 10.6897(8) Å, c = 15.915(2) Å, β = 94.342(8)°, and V = 1772.7(3) Å 3 for 3c . 3a crystallizes in the orthorhombic space group P 2 1 2 1 2 1 with a = 8.6040(10) Å, b = 12.0490(10) Å, c = 17.020(2) Å, and V = 1764.5(3) Å 3 . The metal−nitrogen distances of these 17-electron complexes (1.719(3) Å for 3a, 1.716(12) Å for 3e, and 1.748(2) Å for 3c ) correspond to a triple bond. (η 5 -C 5 Me 5 )W(NC 6 F 5 )Cl 2 ( 3g ) decomposes in the presence of air to the half-sandwich tungsten(VI) imido complex (η 5 -C 5 Me 5 )W(NC 6 F 5 )Cl 3 ( 4 ) and a green solid. Further hydrolysis of 3g results in the dinuclear tungsten(VI) oxo complex [(η 5 -C 5 Me 5 )WO 2 ] 2 (μ-O) . C 6 F 5 NH 2 ( 5 ) with a linear W−O−W bridge. The complexes have been characterized by X-ray diffraction. 4 crystallizes in the triclinic space group P 1̄, with a = 7.3843(1) Å, b = 11.529(2) Å, c = 11.558(2) Å, α = 77.38(2)°, β = 80.15(2)°, γ = 79.88(2)°, and V = 936.2(3) Å 3; 5 crystallizes in the monoclinic space group P 2 1 / n, with a = 1.3246(3) Å, b = 1.0042(3) Å, c = 1.4102(3) Å, β = 104.37(3)°, and V = 1.8173(6) Å 3 .