Gold(I) and Silver(I) Complexes of Diphosphacyclobutadiene Cobaltate Sandwich Anions

The synthesis and structural characterization of the first coordination compounds of bis(diphosphacyclobutadiene) cobaltate anions [M(P2C2R2)2] is described. Reactions of the new potassium salts [K(thf)3{Co(4-P2C2tPent2)2}] (1) and [K(thf)4{Co(4-P2C2Ad2)2}] (2) with [AuCl(tht)] (tht=tetrahydrothiophene), [AuCl(PPh3)] and Ag[SbF6] afforded the complexes [Au{Co(P2C2tPent2)2}(PMe3)2] (3), [Au{Co(P2C2Ad2)2}]x (4), [Ag{Co(P2C2Ad2)2}]x (5), [Au(PMe3)4][Au{Co(P2C2Ad2)2}2] (6), [K([18]crown-6)(thf)2][Au{Co(P2C2Ad2)2}2] (7), and [K([18]crown-6)(thf)2][M{Co(P2C2Ad2)2}2] (8: M=Au 9: M=Ag) in moderate yields. The molecular structures of 2 and 3, and 69 were elucidated by X-ray crystallography. Complexes 49 were thoroughly characterized by 31P and 13C solid state NMR spectroscopy. The complexes [Au{Co(P2C2Ad2)2}]x (4) and [Ag{Co(P2C2Ad2)2}]x (5) exist as coordination polymers in the solid state. The linking mode between the monomeric units in the polymers is deduced. The soluble complexes 13, 6, and 7 were studied by multinuclear 1H-, 31P{1H}-, and 13C{1H} NMR spectroscopy in solution. Variable temperature NMR measurements of 3 and 6 in deuterated THF reveal the formation of equilibria between the ionic species [Au(PMe3)4]+, [Au(PMe3)2]+, [Co(P2C2R2)2], and [Au{Co(P2C2R2)2}2] (R=tPent and Ad).