L. Douce et al., Phosphine oxide functionalised with two bipyridine subunits: a novel ligand for the engineering of sterically hindered complexes, NEW J CHEM, 25(8), 2001, pp. 1024-1030
Ligand L, containing two 6-methyl-6'-methyl-yl-2,2'-bipyridine moieties lin
ked by a "PhP=O'' spacer, has been prepared. Subsequent complexation with [
Cu(CH3CN)(4)](BF4) led to a unique complex of formula [CuL](BF4). The molec
ular structure has been determined by X-ray crystallography in the solid st
ate and NMR studies in solution. The complex displays an intense absorption
band in the visible wavelength range with maxima at 418 and 509 nm, and is
oxidised reversibly at +0.66 V (DeltaE(p) = 80 mV) to the corresponding Cu
(II) species, while two successive reductions of the coordinated bipyridine
fragments occur at -1.60 (DeltaE(p) = 66) and -1.84 V (DeltaE(p) = 70 mV)
vs. SCE. Direct spectrophotometric titrations with global analysis allowed
us to elicit stability constants for the emergent complex and to highlight
the formation of a dinuclear complex in the presence of excess copper.