Tris(tert-butyl isocyanide)bis[tris(4-methoxyphenyl)phosphine]cobalt(I) perchlorate dichloromethane disolvate and tris(tert-butyl isocyanide)bis[tris(4-methoxyphenyl)phosphine]cobalt(II) bis(perchlorate) dichloromethane disolvate: modification of a trigonal-bipyramidal structure with change of metal oxidation state.

The title complexes, [Co(C(5)H(9)N)(3)(C(21)H(21)O(3)P)(2)]ClO(4).2CH(2)Cl(2), (I), and [Co(C(5)H(9)N)(3)(C(21)H(21)O(3)P)(2)](ClO(4))(2).2CH(2)Cl(2), (II), respectively, crystallize in the hexagonal space group P6(3)/m and the monoclinic space group P2(1)/n, respectively. The cation of complex (I) has D(3h) site symmetry around the Co atom and the overall symmetry is C(3h). Complex (II) is best described as having a distorted trigonal-bipyramidal coordination, with a Co site symmetry of C(s). Compounds (I) and (II) form an analogous pair of five-coordinate Co(I) and Co(II) complexes with the same ligands, making it possible to establish (i) if the Co site coordination for both complexes is indeed trigonal-bipyramidal, as initially assumed, and (ii) if significant structural differences occur when the oxidation state of the metal is changed.