Synthesis of Heterometal Cluster Complexes by the Reaction of Cobaltadichalcogenolato Complexes with Groups 6 and 8 Metal Carbonyls

Metalladichalcogenolate cluster complexes [{CpCo(S2C6H4)}2Mo(CO)2] (Cp = η5-C5H5) (3), [{CpCo(S2C6H4)}2W(CO)2] (4), [CpCo(S2C6H4)Fe(CO)3] (5), [CpCo(S2C6H4)Ru(CO)2(PtBu3)] (6), [{CpCo(Se2C6H4)}2Mo(CO)2] (7), and
[{CpCo(Se2C6H4)}(Se2C6H4)W(CO)2] (8) were synthesized by the reaction of [CpCo(E2C6H4)] (E = S, Se) with
[M(CO)3(py)3] (M = Mo, W), [Fe(CO)5], or [Ru(CO)3(PtBu3)2], and their crystal structures and physical properties
were investigated. In the series of trinuclear group 6 metal−Co complexes, 3, 4, and 7 have similar structures, but
the W−Se complex, 8, eliminates one cobalt atom and one cyclopentadienyl group from the sulfur analogue, 4,
and does not satisfy the 18-electron rule. 1H NMR observation suggested that the CoW dinuclear complex 8 was
generated via a trinuclear Co2W complex, with a structure comparable to 7. The trinuclear cluster complexes, 3,
4, and 7, undergo quasi-reversible two-step one-electron reduction, indicating the formation of mixed-valence
complexes CoIIIM0CoII (M = Mo, W). The thermodynamic stability of the mixed-valence state increases in the order
4 < 3 < 7. In the dinuclear group 8 metal−Co complexes, 5 and 6, the CpCo(S2C6H4) moiety and the metal
carbonyl moiety act as a Lewis acid character and a base character, respectively, as determined by their
spectrochemical and redox properties. Complex 5 undergoes reversible two-step one-electron reduction, and an
electron paramagnetic resonance (EPR) study indicates the stepwise reduction process from CoIIIFe0 to form CoIIIFe-I
and CoIIFe-I.