ACTIVATION OF WATER MOLECULES - 2. GENERATION OF STRONG HYDROXO BASES BY THE REACTION OF WATER WITH PLATINUM (0) PHOSPHINE COMPLEXES AND THE APPLICATIONS AS CATALYSTS FOR H-D EXCHANGE AND HYDRATION REACTIONS.

Article abstract of DOI:10.1021/ja00502a017

The dissociation of Pt(PEt//3)//4 in organic solvents (THF, n-heptane) occurs to give Pt(PEt//3)//3 L equals 0. 5 M in THF at 20 degree C), no further dissociation being detected, while Pt left bracket P(i-Pr)//3 right bracket //3, upon dissolution in the above solvents, exists mainly as Pt left bracket P(i-Pr)//3 right bracket //2 (K//L equals 0. 14 M in THF at 20 degree chemical Addition of water to PtL//(L equals PEt//3//, P(i-Pr)//3) generates strong hydroxy bases, left bracket PtHL//3 right bracket OH (L equals PEt//3) or trans- left bracket PtH(S)L//2 right bracket OH (L equals P(i-Pr)//3//, S equals solvent), while the addition to Pt left bracket P(i-Pr)//3 right bracket //2 gives a sigma -hydrido hydroxo compound, trans-PtH(OH) left bracket P(i-Pr)//3 right bracket //2. Quantitative study on the reversible water addition to PtL//3 in organic solvents was carried out by pH and conductance measurements. The conductometric behaviors of the system PtL//3(L equals PEt//3)/H//2O in pyridine and THF are described in terms of two equilibria. The mechanism was studied for H-D exchange of C//6H//5COCH//3 to show that the reaction follows a rate equation, R equals k left bracket Pt right bracket left bracket C//6H//5COCH//3 right bracket , and involves a reversible condensation, M** plus OD** minus plus C//6H//5COCH//3 reversible reaction MCH// 2COC//6H//5 plus DHO, as the rate-determining step. Unlike the alkaline base-catalyzed reaction, alpha -olefinic, allylic, and aldehydic hydrogen atoms of alpha , beta -unsaturated carbonyl compounds were exchanged. The hydration of the nitrile and double bonds of RCH equals CHCN catalyzed by left bracket PtHL//3 right bracket OH or left bracket PtH(S)L//2 right bracket OH and trans-Pt(OH)(R)(PPh//3)//2 occurs with excellent chemical yields.