M-P versus M=M Bonds as Protonation Sites in the Organophosphide-Bridged Complexes [M2Cp2(-PR2)(mg
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- 作者：M. Angeles Alvarez ; M. Esther Garcí ; a ; M. Eugenia Martí ; nez ; Alberto Ramos ; Miguel A. Ruiz ; David Sá ; ez ; Jacqueline Vaissermann
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：August 21, 2006
- 年：2006
- 卷：45
- 期：17
- 页码：6965 - 6978
- 全文大小：203K
- 年卷期：v.45,no.17(August 21, 2006)
- ISSN：1520-510X
文摘
The unsaturated complexes [W2Cp2(
mages/entities/mgr.gif">-PR2)(mages/entities/mgr.gif">-PR'2)(CO)2] (Cp = mages/gifchars/eta.gif" BORDER=0 >5-C5H5; R = R' = Ph, Et; R = Et, R' = Ph)react with HBF4·OEt2 at 243 K in dichloromethane solution to give the corresponding complexes [W2Cp2(H)(mages/entities/mgr.gif">-PR2)(mages/entities/mgr.gif">-PR'2)(CO)2]BF4, which contain a terminal hydride ligand. The latter rearrange at room temperature to give[W2Cp2(mages/entities/mgr.gif">-H)(mages/entities/mgr.gif">-PR2)(mages/entities/mgr.gif">-PR'2)(CO)2]BF4, which display a bridging hydride and carbonyl ligands arranged parallel toeach other (W-W = 2.7589(8) Å when R = R' = Ph). This explains why the removal of a proton from the lattergives first the unstable isomer cis-[W2Cp2(mages/entities/mgr.gif">-PPh2)2(CO)2]. The molybdenum complex [Mo2Cp2(mages/entities/mgr.gif">-PPh2)2(CO)2] behavessimilarly, and thus the thermally unstable new complexes [Mo2Cp2(H)(mages/entities/mgr.gif">-PPh2)2(CO)2]BF4 and cis-[Mo2Cp2(mages/entities/mgr.gif">-PPh2)2(CO)2] could be characterized. In contrast, related dimolybdenum complexes having electron-rich phosphide ligandsbehave differently. Thus, the complexes [Mo2Cp2(mages/entities/mgr.gif">-PR2)2(CO)2] (R = Cy, Et) react with HBF4·OEt2 to give first theagostic type phosphine-bridged complexes [Mo2Cp2(mages/entities/mgr.gif">-PR2)(mages/entities/mgr.gif">-mages/gifchars/kappa.gif" BORDER=0 >2-HPR2)(CO)2]BF4 (Mo-Mo = 2.748(4) Å for R =Cy). These complexes experience intramolecular exchange of the agostic H atom between the two inequivalent Ppositions and at room-temperature reach a proton-catalyzed equilibrium with their hydride-bridged tautomers [ratioagostic/hydride = 10 (R = Cy), 30 (R = Et)]. The mixed-phosphide complex [Mo2Cp2(mages/entities/mgr.gif">-PCy2)(mages/entities/mgr.gif">-PPh2)(CO)2]behaves similarly, except that protonation now occurs specifically at the dicyclohexylphosphide ligand [ratio agostic/hydride = 0.5]. The reaction of the agostic complex [Mo2Cp2(mages/entities/mgr.gif">-PCy2)(mages/entities/mgr.gif">-mages/gifchars/kappa.gif" BORDER=0 >2-HPCy2)(CO)2]BF4 with CNtBu gavemono- or disubstituted hydride derivatives [Mo2Cp2(mages/entities/mgr.gif">-H)(mages/entities/mgr.gif">-PCy2)2(CO)2-x(CNtBu)x]BF4 (Mo-Mo = 2.7901(7) Å forx = 1). The photochemical removal of a CO ligand from the agostic complex also gives a hydride derivative, thetriply bonded complex [Mo2Cp2(H)(mages/entities/mgr.gif">-PCy2)2(CO)]BF4 (Mo-Mo = 2.537(2) Å). Protonation of [Mo2Cp2(mages/entities/mgr.gif">-PCy2)2(mages/entities/mgr.gif">-CO)] gives the hydroxycarbyne derivative [Mo2Cp2(mages/entities/mgr.gif">-COH)(mages/entities/mgr.gif">-PCy2)2]BF4, which does not transform into its hydrideisomer.