Selective Photochemistry at Stereogenic Metal and Ligand Centers of cis-[Ru(diphosphine)2(H)2]: Preparative, NMR, Solid State, and Laser Flash Studies
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- 作者：Marius V. C芒mpian ; Robin N. Perutz ; Barbara Procacci ; Robert J. Thatcher ; Olga Torres ; Adrian C. Whitwood
- 刊名：The Journal of the American Chemical Society
- 出版年：2012
- 出版时间：February 22, 2012
- 年：2012
- 卷：134
- 期：7
- 页码：3480-3497
- 全文大小：713K
- 年卷期：v.134,no.7(February 22, 2012)
- ISSN：1520-5126
文摘
Three ruthenium complexes 螞-[cis-Ru((R,R)-Me-BPE)2(H)2] 螞-R,R-Ru1H2, 螖-[cis-Ru((S,S)-Me-DuPHOS)2(H)2] 螖-S,S-Ru2H2, and 螞-[cis-Ru((R,R)-Me-DuPHOS)2(H)2] 螞-R,R-Ru2H2 (1 = (Me-BPE)2, 2 = (Me-DuPHOS)2) were characterized by multinuclear NMR and CD spectroscopy in solution and by X-ray crystallography. The chiral ligands allow the full control of stereochemistry and enable mechanistic studies not otherwise available. Oxidative addition of E鈥揌 bonds (E = H, B, Si, C) was studied by steady state and laser flash photolysis in the presence of substrates. Steady state photolysis shows formation of single products with one stereoisomer. Solid state structures and circular dichroism spectra reveal a change in configuration at ruthenium for some 螖-S,S-Ru2H2/螞-R,R-Ru2H2 photoproducts from 螞 to 螖 (or vice versa) while the configuration for 螞-R,R-Ru1H2 products remains unchanged as 螞. The X-ray structure of silyl hydride photoproducts suggests a residual H(1)路路路Si(1) interaction for 螖-[cis-Ru((R,R)-Me-DuPHOS)2(Et2SiH)(H)] and 螖-[cis-Ru((R,R)-Me-DuPHOS)2(PhSiH2)(H)] but not for their Ru(R,R-BPE)2 analogues. Molecular structures were also determined for 螞-[cis-Ru((R,R)-Me-BPE)2(Bpin)(H)], 螞-[Ru((S,S)-Me-DuPHOS)2(畏2-C2H4)], 螖-[Ru((R,R)-Me-DuPHOS)2(畏2-C2H4)], and trans-[Ru((R,R)-Me-DuPHOS)2(C6F5)(H)]. In situ laser photolysis in the presence of p-H2 generates hyperpolarized NMR spectra because of magnetically inequivalent hydrides; these experiments and low temperature photolysis with D2 reveal that the loss of hydride ligands is concerted. The reaction intermediates [Ru(DuPHOS)2] and [Ru(BPE)2] were detected by laser flash photolysis and have spectra consistent with approximate square-planar Ru(0) structures. The rates of their reactions with H2, D2, HBpin, and PhSiH3 were measured by transient kinetics. Rate constants are significantly faster for [Ru(BPE)2] than for [Ru(DuPHOS)2] and follow the substrate order H2 > D2 > PhSiH3 > HBpin.