Experimental and Theoretical Study of the Kinetic and Thermodynamic Sites of Protonation in (CO)Pt(-PBut2)2
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- 作者：Piero Leoni ; Marco Pasquali ; Valerio Cittadini ; Alessandro Fortunelli ; and Massimo Selmi
- 刊名：Inorganic Chemistry
- 出版年：1999
- 出版时间：November 15, 1999
- 年：1999
- 卷：38
- 期：23
- 页码：5257 - 5265
- 全文大小：324K
- 年卷期：v.38,no.23(November 15, 1999)
- ISSN：1520-510X
文摘
The PtIPtI monocarbonyl derivative (But2HP)Pt(
-PBut2)2Pt(CO) (5), with a planar, asymmetrically substitutedPt2(-PBut2)2 core, reacts with CF3SO3H to give the new PtIIPtII carbonyl hydride [(But2HP)Pt(-PBut2)2Pt(CO)(H)]CF3SO3 (6a). Complex 6a, in which the proton is terminally attached to the Pt atom bearing the carbonylligand, is formed under kinetic control and is stable in well-dried nonbasic solvents. This isomer is convertedquantitatively by an external weak base into the thermodynamically favored form, [(PBut2H)(H)Pt(-PBut2)2Pt(CO)]CF3SO3 (6b), in which the proton is terminally attached to the Pt atom bearing the phosphine group. In thepresence of an excess of triflic acid, 6a is further protonated to give [Pt2(-PBut2)(-H)(CO)(PBut2H)(
2-PBut2H)](CF3SO3)2 (7) by the formation of a P-H bond between the hydride and the adjacent phosphido ligandinduced by metal protonation. Complex 7 was characterized by multinuclear NMR spectroscopy, which stronglysuggests a Pt-H-P agostic interaction. Like 6a, complex 7 is stable in nonbasic media, but yields 6b rapidly andquantitatively in the presence of a base. Experimental data compare well with the results of ab initio calculationson model compounds corresponding to 5, 6a+, and 6b+, whose structures have been optimized in the gas phase.
-PBut2)2Pt(CO) (5), with a planar, asymmetrically substitutedPt2(-PBut2)2 core, reacts with CF3SO3H to give the new PtIIPtII carbonyl hydride [(But2HP)Pt(-PBut2)2Pt(CO)(H)]CF3SO3 (6a). Complex 6a, in which the proton is terminally attached to the Pt atom bearing the carbonylligand, is formed under kinetic control and is stable in well-dried nonbasic solvents. This isomer is convertedquantitatively by an external weak base into the thermodynamically favored form, [(PBut2H)(H)Pt(-PBut2)2Pt(CO)]CF3SO3 (6b), in which the proton is terminally attached to the Pt atom bearing the phosphine group. In thepresence of an excess of triflic acid, 6a is further protonated to give [Pt2(-PBut2)(-H)(CO)(PBut2H)(2-PBut2H)](CF3SO3)2 (7) by the formation of a P-H bond between the hydride and the adjacent phosphido ligandinduced by metal protonation. Complex 7 was characterized by multinuclear NMR spectroscopy, which stronglysuggests a Pt-H-P agostic interaction. Like 6a, complex 7 is stable in nonbasic media, but yields 6b rapidly andquantitatively in the presence of a base. Experimental data compare well with the results of ab initio calculationson model compounds corresponding to 5, 6a+, and 6b+, whose structures have been optimized in the gas phase.