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The synthesis and characterization of a new ruthenium(ii) complex containing a hemilabile P^N-ligand are reported.

The syntheses of two new series of ruthenium(II) complexes incorporating substituted 4′-phenylterpyridine, triphenylphosphine and chloride (A Series) or hydride (B Series) are reported. In both series 4′-phenyl-terpyridine incorporated substituents of varying electronic character at the 4-position: 4`-(4-chlorophenyl)-2,2´:6´,2``-terpyridine (ClPh-tpy); 4`-(4-nitrophenyl)-2,2´:6´,2``-terpyridine (NO 2 Ph-tpy) and 4`-(4-methoxyphenyl)-2,2´:6´,2``-terpyridine (OMePh-tpy). The complexes have been characterized by elemental analysis and UV-Vis, IR and NMR spectroscopy and their electrochemical properties studied. The substituents on the 4′-phenylterpyridine ligand influence the properties of the metal center. For all complexes prepared, λ max of a characteristic low energy band in the UV-Vis spectrum was found to move to shorter wavelengths as the solvent polarity increased (a hypsochromic shift). For the B series complexes, the low energy band was broader and undergoes a small shift to lower frequencies as a result of the substitution of chloride by a hydride. The 1 H-and 31 P-NMR spectra clearly indicate that the geometry of the 4′-phenyl-terpyridine ligand is meridional in the complexes, with the two triphenylphosphines trans to each other. Upon optimization of the experimental procedures the yields increased to 70% for the B series complexes.