title: Temperature-dependent coordination of phosphine to five-coordinate alkenylruthenium complexes.
abstract: The red, five-coordinate complexes Ru(CO)Cl(PPh(3))2(CH=CHPh) and [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHC(6)H(4)CH=CH) undergo reversible coordination of PPh(3) at low temperature to produce the pale yellow, six-coordinate complexes Ru(CO)Cl(PPh(3))3(CH=CHPh) and [Ru(CO)Cl(PPh(3))3]2(mu-CH=CHC(6)H(4)CH=CH). X-ray crystal structures of the latter complex and of the hydride complex RuH(CO)Cl(PPh(3))3 were obtained. 1H and 31P NMR spectra between 20 and -70 degrees C exhibit large changes in both equilibrium constants and dynamic effects. Thermodynamic parameters, DeltaH = -17.5 +/- 2.0 kcal/mol and DeltaS = -57.5 +/- 7.6 eu, were obtained for PPh(3) coordination to the monoruthenium complex, and activation parameters, DeltaH = 20.6 +/- 0.7 kcal/mol and DeltaS = 41.6 +/- 2.0 eu, were obtained for the reverse decoordination. Coordination of PPh(3) was not observed upon cooling of the shorter bridged complex, [Ru(CO)Cl(PPh(3))2]2(mu-CH=CHCH=CH).
authors.affiliation: Department of Chemistry, Syracuse University, Syracuse, New York 13244-4100, USA.
authors.forename: Sripriya K
authors.initials: SK
authors.lastname: Seetharaman
authors.forename: Min-Chul
authors.initials: MC
authors.lastname: Chung
authors.forename: Ulrich
authors.initials: U
authors.lastname: Englich
authors.forename: Karin
authors.initials: K
authors.lastname: Ruhlandt-Senge
authors.forename: Michael B
authors.initials: MB
authors.lastname: Sponsler