Complexes of the general
formulae M(CO)3(dam)I2, M(CO)3(dam)2I2,
and M(CO)2(dam)2I2
have been prepared and characterized [M = Mo, W; dam = bis(diphenylarsino)methane].
All of the compounds are diamagnetic and non-electrolytes in acetone solution.
The tungsten derivatives were prepared by direct interaction of dam with diiodotetracarbonyltungsten(11), but the molybdenum
analogues were obtained by iodine oxidation of the zero-valent
complex Mo(CO)4(dam)2 whose preparation is
reported for the first time in this paper. The bis(dam)tricarbonyl
complexes, M(C0)3(dam)2I2, are unstable in
solution giving M(CO)2(dam)I2 and free dam in equilibrium
with undissociated complex. The bis(dam)tricarbonyl
complexes also readily lose carbon monoxide, especially in the case of
molybdenum, to give M(CO)z(dam)2I2. These
dicarbonyl complexes readily absorb carbon monoxide to re-form the tricarbonyl
complexes to give a reversible carbon monoxide carrying system. Overall, these
systems may be represented by the general equations :
M(CO)3(dam)I2 + dam ↔ M(CO)3(dam)2I2
+ CO
These equilibria
have been studied using both infrared and nuclear magnetic resonance
techniques.
Carbonyl halides of the Group VI transition metals. XXII. Reaction of Halopentacarbonyl-chromium, -molybdenum, and -tungsten(0) anions with carbon monoxide
