Basal site substitution in the sulfido-bridged cluster Ru3(CO)9(μ3-S)2 by the redox-active diphosphine 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd). Synthesis, X-ray structure and electrochemical properties of Ru3(CO)7(bpcd)(μ3-S)2

Abstract

Abstract The sulfido-bridged cluster Ru 3 (CO) 9 ( μ 3 -S) 2 ( 1 ) has been allowed to react with the redox-active diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in the presence of Me 3 NO to give the new cluster Ru 3 (CO) 7 (bpcd)( μ 3 -S) 2 ( 2 ) in 61% yield. The ancillary bpcd in 2 is bound at one of the basal ruthenium sites in a chelating fashion, being derived by the replacement of axial and equatorial CO groups. This cluster represents the first example of a cluster derived from Ru 3 (CO) 9 ( μ 3 -S) 2 that contains a chelating diphosphine ligand. Cluster 2 has been characterized in solution by IR and NMR ( 1 H and 31 P) spectroscopies and in the solid state by X-ray diffraction analysis. Ru 3 (CO) 7 (bpcd)( μ 3 -S) 2 , which exists as two crystallographically independent molecules in the unit cell, crystallizes in the monoclinic space group P2 1 /c, a= 19.451(1), b = 21.865(2) A , Z = 8, D calc = 1.702 cm −3 ; R = 0.0411 , R w = 0.0447 for 5622 observed reflections. The redox properties of 2 were explored by cyclic voltammetry in MeCN, which revealed the presence of a reversible one-electron reduction process (bpcd based) and an irreversible oxidation (metal based). The natture of the HOMO and LUMO in 2 has been examined by carrying out extended Huckel MO calculations on the model cluster Ru 3 (CO) 7 (H 4 -bpcd)( μ 3 -S) 2 , and the results are discussed relative to the observed electrochemistry.