Acetylenedithiolate as directional bridging ligand in cobalt(i) alkyne platinumdithiolato bimetallic complexes

Abstract

The η²-C,C′-acetylenedithiolate (acdt²⁻) complex K[(triphos)Co(acdt)], K-5, {triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane} was obtained by consecutive removal of S-protection groups in [(triphos)Co(1)]PF₆, 3-PF₆ (1 = 1-Trimethylsilyl-7-phenyl-3,6-dithiahept-4-ine). Reaction of K-5 with selected Pt(II) salts resulted in the formation of the new heterobimetallic complexes [(phen)Pt(5)]BPh₄, 6-BPh₄, (phen = 1,10-phenanthroline) and [(dppe)Pt(5)]BPh₄, 7-BPh₄, {dppe = 1,2-bis(diphenylphosphino)ethane}, which were fully characterized. X-ray diffraction studies showed that Co and Pt are linked by acdt²⁻ in the η²-C,C′-κ²-S,S′-bridging mode. The electronic structure of 6-BPh₄ and 7-BPh₄ was investigated by electronic absorption spectroscopy, cyclic voltammetry and X-band EPR spectroscopy of neutral 7. In addition, NMR spectroscopy, X-ray diffraction and reactivity studies with the alkyne complexes [(PMe₃)₃Co(1)]-PF₆, 2-PF₆, with 3-PF₆ and the intermediate product [(triphos)Co{η²-(S)C₂(SCH₂Ph)}], 4, uncovered the flexibility of the CoC₂S₂-moiety within the persisting complex scaffold throughout the synthetic scheme.