Generation and Reactivity of Polychalcogenide Chains in Binuclear Cobalt(II) Complexes.

A series of six binuclear Co(II)-thiolate complexes, [Co(BPMP)(S-CH--X)] (X = OMe, ; NH, ), [Co(BPMP)(μ-S-CH--O)] (), and [Co(BPMP)(μ-Y)] (Y = bdt, ; tdt, ; mnt, ), has been synthesized from [Co(BPMP)(MeOH)(Cl)] () and [Co(BPMP)(Cl)] (), where BPMP is the anion of 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol. While and could allow the two-electron redox reaction of the two coordinated thiolates with elemental sulfur (S) to generate [Co(BPMP)(μ-S)] (), the complexes, , could not undergo a similar reaction. An analogous redox reaction of with elemental selenium ([Se]) produced [{Co(BPMP)(μ-Se)}{Co(BPMP)(μ-Se)}] () and [Co(BPMP)(μ-Se)] (). Further reaction of these polychalcogenido complexes, and /, with PPh allowed the isolation of [Co(BPMP)(μ-S)] () and [Co(BPMP)(μ-Se)] (), which, in turn, could be converted back to and upon treatment with S and [Se], respectively. Interestingly, while the redox reaction of the polyselenide chains in and with S produced and [Se], the treatment of with [Se] gave back only the starting material (), thus demonstrating the different redox behavior of sulfur and selenium. Furthermore, the reaction of and / with activated alkynes and cyanide (CN) allowed the isolation of the complexes, [Co(BPMP)(μ-EC(COR))] (E = S: , R = Me; , R = Et; E = Se: , R = Me; , R = Et) and [Co(BPMP)(μ-SH)(NCS)] (), respectively. The present work, thus, provides an interesting synthetic strategy, interconversions, and detailed comparative reactivity of binuclear Co(II)-polychalcogenido complexes.