om9807001_si_001.pdf (1.07 MB)
Synthetic, Structural, and Solution Thermochemical Studies in the Dimethylbis(phosphine)platinum(II) System. Dichotomy between Structural and Thermodynamic Trends
journal contribution
posted on 1999-01-16, 00:00 authored by Christopher M. Haar, Steven P. Nolan, William J. Marshall, Kenneth G. Moloy, Alfred Prock, Warren P. GieringReaction enthalpies of the complex (COD)PtMe2 (COD = η4-1,5-cyclooctadiene) with an
extensive series of unidentate phosphines have been measured by solution calorimetry. The
molecular structures of cis-P2PtMe2 for P = PEt3, PMe2Ph, P(pyrrolyl)3, and PCy3 have been
determined by single-crystal X-ray diffraction. The relative stabilities of the resulting P2PtMe2 complexes are strongly influenced by the size (cone angle) of the incoming phosphine,
with larger cone angles resulting in less thermodynamically stable complexes. Crystallographic and 31P NMR data, however, do not reflect the enthalpic stability scale and are
more closely correlated to the electronic (χ) character of the phosphine ligands. The strength
of the Pt−P interaction, as determined from these structural data, is greatest for phosphines
with electron-withdrawing substituents, regardless of phosphine size or reaction enthalpy.