Syntheses and Reactivity of Ruthenium σ-Pyridylacetylides

Ruthenium σ-acetylides containing a dangling pyridine were synthesized from the reactions of CpRu(L) 2 Cl (L = PPh 3, 1 / 2 (C 5 H 4 PPh 2 ) 2 Fe) with 4-ethynylpyridine, ( E )-1-(4-ethynylphenyl)-2-(4-pyridyl)ethylene, or 4-(ethynylphenyl)(4-pyridyl)acetylene in the presence of NH 4 + PF 6 - followed by deprotonation with a base. The dangling pyridine can be protonated, methylated, or ligated to tungsten carbonyl fragments. The ruthenium donor to the pyridinium acceptor charge-transfer absorption appears at longer wavelength as the conjugation chain becomes longer. The quadratic hyperpolarizabilities of the methylated derivatives were determined using the hyper Rayleigh scattering method. X-ray analysis was employed to examine the structure of the dinuclear complex Ru(C⋮CC 5 H 4 N{W(CO) 4 (PPh 3 )})(η 2 -dppf)(η 5 -C 5 H 5 ) (dppf = 1,1‘-bis(diphenylphosphino)ferrocene).