Unsymmetrical dirhenium complexes that contain [Re2]6+ and [Re2]5+ cores complexed by tridentate ligands with P2O and P2N donor sets

The quadruply bonded dirhenium(III) complex (n-Bu4N)(2)Re2Cl8 reacts with tridentate ligands that contain essentially planar P,O,P donor sets to afford the complexes Re2Cl6(eta(3)-L-1) (3) (L-1 = bis[2-(diphenylphosphino)phenyl]ether) and (n-Bu4N)[Re2Cl7(eta(1)-L-2)] (4) (L-2 = 4,6-bis(diphenylphosphino)dibenzofuran). Spectroscopic and electrochemical data support the unsymmetrical structure Cl4ReReCl2(eta(3)-L-1) in the case of 3, while 4 contains monodentate P-bound L-2; both complexes contain Re-Re-4 bonds. The synthon cis-Re-2(mu-O2CCH3)(2)Cl-4(H2O)(2) reacts with ligands L-1, L-2 2,6-bis(diphenylphosphinomethyl)pyridine (L-3), bis[2-(diphenylphosphino)ethyl]amine (L-4), and N,N-bis[2-(diphenylphosphino)ethyl]trimethylacetamide (L-5) to give the paramagnetic complexes Re-2(mu-O2CCH3)Cl-4(eta(3)-L-n) (5-9) with Re-Re-3.5 bonds. The lability of the p-acetato ligands in 5-9 has been demonstrated by the reactions of compounds 5 (n = 1) and 7 (n = 3) with 4-Ph2PC6H4CO2H, 2-Ph2PC6H4CO2H, and quinoline-4-carboxylic acid to give complexes 10-12 (from 5) and 13-15 (from 7), respectively. These products contain uncoordinated donor atoms that can be used to produce mixed-metal assemblies. Compounds 5 and 7 also react with terephthalic acid (1,4-C6H4(CO2H) to give [Re2Cl4(eta(3)-L-1)](2)(mu-O2CC6H4CO2) (16) and [Re2Cl4(eta(3)-L-3)](2)(mu-O2CC6H4CO2) (17) in which electronic coupling between the paramagnetic sets of dirhenium units is very weak. Single-crystal X-ray structure determinations have been carried out on complexes 5-8, 11, 12, and 14-16.