Synthesis, characterization and electronic structure of the novel ‘stellated’ octahedral cluster [Co6(µ3-S)7(µ3-H)(PEt3)6]+. Crystal and molecular structure of [Co6(µ3-S)7(µ3-H)(PEt3)6]0.7[Co6(µ3-S)8(PEt3)6]0.3[BPh4]

Abstract

Reaction of Co(O₂CMe)₂·4H₂O with an excess of PEt₃ and H₂S afforded the novel diamagnetic octahedral cluster [Co₆(µ₃-S)₇(µ₃-H)(PEt₃)₆]⁺ together with a minor amount of the known paramagnetic isostructural [Co₆(µ₃-S)₈(PEt₃)₆]⁺. Solid solutions of the two cluster cations have been isolated as the BPh₄^– salt. The deuteriated derivative [Co₆(µ₃-S)₇(µ₃-D)(PEt₃)₆]⁺ has been prepared for comparison. The compounds have been characterized by ¹H, ³¹P NMR, mass spectrometry and electrochemical measurements. The molecular structure of a sample of composition [Co₆(µ₃-S)₇(µ₃-H)(PEt₃)₆]_0.7[Co₆(µ₃-S)₈(PEt₃)₆]_0.3[BPh₄] has been determined by single-crystal X-ray diffraction. It consists of a solid solution of [Co₆(µ₃-S)₇(µ₃-H)(PEt₃)₆]⁺ and [Co₆(µ₃-S)₈(PEt₃)₆]⁺. The cation [Co₆(µ₃-S)₇(µ₃-H)(PEt₃)₆]_0.7[Co₆(µ₃-S)₈(PEt₃)₆]_0.3⁺ is isostructural with the series [M₆(µ₃-S)₈(PEt₃)₆]ⁿ⁺, having a metal–metal separation averaging 2.739(8)Å. The electronic structure of the novel hydridoderivative has been investigated through density functional calculations.