Synthesis, characterization and reactivity of thiolate-bridged cobalt-iron and ruthenium-iron complexes

Thiolate-bridged hetero-bimetallic complexes [Cp*M(MeCN)N2S2FeCl][PF6] (2, M = Ru; 3, M = Co, Cp* =η5-C5Me5, N2S2 = N,N'-dimethyl-3,6-diazanonane-1,8-dithiolate) were prepared by self-assembly of dimer [N2S2Fe]2with mononuclear precursor [Cp*Ru(MeCN)3][PF6] or [Cp*Co(MeCN)3][PF6]2in the presence of CHCl3as a chloride donor. Complexes 2and 3exhibit obviously different redox behaviors investigated by cyclic voltammetry and spin density distributions supported by DFT calculations. Notably, iron-cobalt complex 3possesses versatile reactivities that cannot be achieved for complex 2. In the presence of CoCp2, complex 3can undergo one-electron reduction to generate a stable formally CoIIFeIIcomplex [Cp*CoN2S2FeCl] (4). Besides, the terminal chloride on the iron center in 3can be removed by dehalogenation agent AgPF6or exchanged with azide to afford the corresponding complexes [Cp*Co(MeCN)N2S2Fe(MeCN)][PF6]2(5) and [Cp*Co(MeCN)N2S2Fe(N3)][PF6] (6). In addition, complexes 2, 3and 4show distinct catalytic reactivity toward the disproportionation of hydrazine into ammonia. These results may be helpful to understand the vital role of the heterometal in some catalytic transformations promoted by heteromultinuclear complexes.