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(P(2)(2)R(2))(2)](-) is described. Reactions of the new potassium salts [K(thf)(3){Co(η(4)-P(2)C(2)tPent(2))(2)}] (1) and [K(thf)(4){Co(η(4)-P(2)C(2)Ad(2))(2)}] (2) with [AuCl(tht)] (tht = tetrahydrothiophene), [AuCl(PPh(3))] and Ag[SbF(6)] afforded the complexes [Au{Co(P(2)C(2)tPent(2))(2)}(PMe(3))(2)] (3), [Au{Co(P(2)C(2)Ad(2))(2)}](x) (4), [Ag{Co(P(2)C(2)Ad(2))(2)}](x) (5), [Au(PMe(3))(4)][Au{Co(P(2)C(2)Ad(2))(2)}(2)] (6), [K([18]crown-6)(thf)(2)][Au{Co(P(2)C(2)Ad(2))(2)}(2)] (7), and [K([18]crown-6)(thf)(2)][M{Co(P(2)C(2)Ad(2))(2)}(2)] (8: M = Au 9: M = Ag) in moderate yields. The molecular structures of 2 and 3, and 6-9 were elucidated by X-ray crystallography. Complexes 4-9 were thoroughly characterized by (31)P and (13)C solid state NMR spectroscopy. The complexes [Au{Co(P(2)C(2)Ad(2))(2)}](x) (4) and [Ag{Co(P(2)C(2)Ad(2))(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 1-3, 6, and 7 were studied by multinuclear (1)H-, (31)P{(1)H}-, and (13)C{(1)H} 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(PMe(3))(4)](+), [Au(PMe(3))(2)](+), [Co(P(2)C(2)R(2))(2)](-), and [Au{Co(P(2)C(2)R(2))(2)}(2)](-) (R = tPent and Ad).
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