Thermodynamics of Inter- and Intramolecular Hydrogen Bonding in (Diphosphine)platinum(II) Diolate Complexes and Its Role in Carbohydrate Complexation Regioselectivity.
Thermodynamic data are reported for intermolecular hydrogen-bonding association of 1 and 2 equiv of phenol with [1,3-bis(diphenylphosphino)propane](phenylethane-1,2-diolato)platinum(II) ((dppp)Pt(Ped)) in dichloromethane solution: = -7.0 +/- 0.1 kcal/mol, = -7.7 +/- 0.4 kcal/mol, = -11.3 +/- 0.4 eu, and = -17.8 +/- 1.2 eu. For comparison, the thermodynamics for hydrogen bonding of phenol to triphenylphosphine oxide in dichloromethane were also determined: DeltaH degrees = -5.1 +/- 0.3 kcal/mol; DeltaS degrees = -8.8 +/- 1.0 eu. Competitive coordination exchange reactions have been used to determine the apparent intramolecular hydrogen bond strengths in (dppp)Pt(1,2-O,O'-glycerolate) and (dppp)Pt(1,2-O,O'-butane-1,2,4-triolate) in both dichloromethane (DeltaG(313) = -2.05 +/- 0.05 and -2.52 +/- 0.06 kcal/mol, respectively) and pyridine (DeltaG(313) = -0.62 +/- 0.03 and -0.82 +/- 0.03 kcal/mol, respectively). Based on these findings, the role of hydrogen-bonding interactions in determining the regioselectivities of complexation of carbohydrates to diphosphine Pt(II) is discussed.
Andrews
Mark A.
MA
Chemistry Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000.
Cook
Gerald K.
GK
Shriver
Zachary H.
ZH