Ethynyltetrakis(trimethylphosphine)cobalt(I), [Co(CCH){P(CH₃)₃}₄]

The title compound consists of a neutral [Co(C₂H)(C₃H₉P)₄] unit, with the ligands arranged in a distorted trigonal bipyramidal configuration, retaining threefold axial symmetry. The C[triple bond]CH unit occupies an axial position, with a C[triple bond]C bond length of 1.185 (6) Å. This compound represents the first structurally characterized example of a cobalt(I)–ethynyl complex.

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