Dirhenium complexes with S2CPR3 bridges donating four and eight electrons - X-ray structures of [Re2(CO)8{μ-η1;η1-S 2CPCy3}] and [Re2(CO)6{μ-η2;η3-S 2CPCy3}]

Article abstract of DOI:10.1002/cber.19971301025

The reaction of fac-[Re(CO)₃(S₂CPR₃)Br] with [Re(CO)₅]^- affords the dinuclear octacarbonyl compounds [Re₂(CO)a(|.iS₂CPR₃)] (3a-b), which have been isolated and characterized by spectroscopic methods. An X-ray crystal-structure determination of the derivative 3a (R = Cy) shows that the S2CPCy3 ligand acts as an η¹(S);η¹(S′) bridge donating two electrons to each metal atom of a symmetrical (CO)₄ReRe(CO)₄ unit. This unit is presumably formed through a concerted process involving carbonyl/sulfur exchange in the nonsymmetrical octacarbonyl (CO)₃(S₂CPR₃)Re-Re(CO)₅ generated after the coupling of the bromo derivative with the carbonyl anion. Complexes 3a-b can be obtained more directly by adding S₂CPR₃ to [Re₂(CO)₈(μ-H)(μ-CH= CHnBu)], which is formed by irradiation of Re₂(CO)₁₀ with 1-hexene. Hydride addition to the central carbon atom of the S₂CPR₃ ligand of 3a-b occurs with loss of PR₃, to give the anion [Re₂(CO)₈(μ-S₂CH)]~ which may be isolated as a salt with the PPN-cation. The octacarbonyl compounds 3a-b can be converted into hexacarbonyl complexes [Re₂(CO)₆(nS₂CPR₃)] (5a-b) by heating in toluene or octane at reflux temperature. According to an X-ray crystal-structure determination of the derivative 5 a (R = Cy), the loss of one carbonyl ligand from each rhenium atom is accompanied by the rearrangement of the S₂CPR₃ ligand which changes its bonding mode from η₁(S);η¹(S′) donating four electrons to η³(S,C,S′);η²(S,S′) donating eight electrons. WILEY-VCH Verlag GmbH,.