Complexes derived from 4-(diphenylphosphino)benzoic acid and related ligands that contain mixed-metal assemblies of palladium(II) or gold(I) in combination with the multiply bonded dirhenium(II) unit

The reactions of cis-Re2(μ-O2CCH3)2Cl2(μ-dppm)2 (dppm=Ph2PCH2PPh2) with substituted benzoic acids of the type 4-XC6H4CO2H (X=Ph2P, Ph2P(O), Ph2P(S) or Ph2P(O)CH2) and with quinoline–4-carboxylic acid afford the complexes cis-Re2(μ-O2CC6H44-X)2CI2(μ-dppm)2 (X=Ph2P (1), Ph2P(O) (2), Ph2P(S) (3) or Ph2P(O)CH2 (4)) and cis-Re2(μ-O2CC10H6N)2Cl2(μ-dppm)2 (5). Similar reactions of trans-Re2(μ-O2CCH3)2Cl2(μ-dppE)2 (dppE=Ph2PC(CH2)PPh2) with 4-Ph2PC6H4CO2H and quinoline–4-carboxylic acid give trans-Re2(μ-O2CC6H44-PPh2)2Cl2(μ-dppE)2 (6) and trans-Re2(μ-O2CC10H6N)2Cl2(μ-dppE)2 (7), respectively. The ability of the unbound ligand functionality on the μ-carboxylate ligands in complexes 1–7 to be used to form mixed-metal complexes is demonstrated by the reactions of 1 and 6 with AuCl(tht) (tht=tetrahydrothiophene) to give cis-Re2(μ-O2CC6H44-PPh2)2Cl2(μ-dppm)2(AuCl)2 (8) and trans-Re2(μ-O2CC6H44-PPh2)2Cl2(μ-dppE)2(AuCl)2 (9). In addition, the reaction of 1 with PdCl2(COD) affords the Re2Pd2 complex cis-Re2(μ-O2C6H44-PPh2)2Cl2(μ-dppm)2(Pd2Cl4) (10), in which the planar [(P)ClPd(μ-Cl)2PdCl(P)] unit has the unusual cis planar structure. An alternative method for preparing mixed-metal Re2Pd2 assemblies is shown by the reaction of cis-Re2(μ-O2CCH3)2Cl2(μ-dppm)2 with cis-PdCl2[(Ph2PCH2)2N4-C6H4CO2H] to produce the complex cis-Re2Cl2(μ-dppm)2[μ-O2CC6H44-N(CH2PPh2)2(PdCl2)]2 (11) in which the mononuclear cis-PdCl2(P)2 units are retained. The structures of 1, 7 and 10 have been established by X-ray crystallography.