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
(η5-C5Me5)MCl4
(M = Mo, W) with the primary amines RNH2 (R =
t-Bu, i-Pr, C6F5, and
2,6-(i-Pr)2C6H3) lead to
the formation
of the imido complexes
[(η5-C5Me5)M(NR)Cl2]
(3a−h). X-ray structure
analyses of 3a, 3c, and 3e reveal
their
monomeric nature. 3c and 3e crystallize in
the monoclinic space group P21/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) Å3 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) Å3 for 3c. 3a
crystallizes in the
orthorhombic space group
P212121 with
a = 8.6040(10) Å, b = 12.0490(10)
Å, c = 17.020(2) Å, and V
=
1764.5(3) Å3. 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.
(η5-C5Me5)W(NC6F5)Cl2
(3g) decomposes in the presence
of air to the half-sandwich tungsten(VI) imido complex
(η5-C5Me5)W(NC6F5)Cl3
(4) and a green solid. Further
hydrolysis of 3g results in the dinuclear tungsten(VI)
oxo complex
[(η5-C5Me5)WO2]2(μ-O).C6F5NH2
(5) with a
linear W−O−W bridge. The complexes have been characterized by
X-ray diffraction. 4 crystallizes in the
triclinic space group P1̄, 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)
Å3; 5 crystallizes in the monoclinic space
group P21/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)
Å3.