The red, five-coordinate complexes Ru(CO)Cl(PPh3) 2(CH=CHPh) and [Ru(CO)Cl(PPh3)2] 2(μ-CH=CHC6H4CH= CH) undergo reversible coordination of PPh3 at low temperature to produce the pale yellow, six-coordinate complexes Ru(CO)Cl(PPh3)3(CH=CHPh) and [Ru(CO)Cl(PPh3)3]2(μ-CH=CHC 6H4CH=CH). X-ray crystal structures of the latter complex and of the hydride complex RuH(CO)Cl(PPh3)3 were obtained. 1H and 31P NMR spectra between 20 and -70°C exhibit large changes in both equilibrium constants and dynamic effects. Thermodynamic parameters, ΔH = -17.5 ± 2.0 kcal/mol and ΔS = -57.5 ± 7.6 eu, were obtained for PPh3 coordination to the monoruthenium complex, and activation parameters, ΔH‡ = 20.6 ± 0.7 kcal/mol and ΔS‡ = 41.6 ± 2.0 eu, were obtained for the reverse decoordination. Coordination of PPh3 was not observed upon cooling of the shorter bridged complex, [Ru(CO)Cl(PPh 3)2]2(μ-CH=CHCH=CH).
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry