RESUMO
In the solid state, the dinuclear iridium complex [µ-Cl-Ir(SiMe2CH2-o-C6H4)2PPh]2, 1, is shown by X-ray diffraction to bear dibenzylsilylphosphine ligands in SiPSi tridentate coordination modes as well as chloride bridges. In C6D6 solution, 1 dissociates into the 14-electron species [IrCl(SiMe2CH2-o-C6H4)2PPh] prone to coordinate one or two L-type ligands such as PR3 (R = Cy, Ph, OEt), CO and CH3CN giving rise to the corresponding mononuclear 16- or 18-electron complexes [IrCl(SiMe2CH2-o-C6H4)2PPh(L)x] (x = 1, 2) as evidenced by X-ray and NMR studies. The dinuclear structure is retained upon reaction with Et3SiH which results in the formation of [µ-Cl,µ-H-Ir2{(SiMe2CH2-o-C6H4)2PPh}2] with a bridging hydride. On the basis of NMR studies, the reaction of the triphenylphosphine complex [IrCl(SiMe2CH2-o-C6H4)2PPh(PPh3)] with LiBHEt3 leads to the hydride complex [IrH(SiMe2CH2-o-C6H4)(η2-H-SiMe2CH-o-C6H4)PPh(PPh3)] in which one SiPSi ligand has been transformed and is now bonded to iridium in a tetradentate mode via P, Si, an agostic Si-H bond, and C of a methine as a result of the activation of one methylene group.
RESUMO
The synthesis of a new trisbenzylsilanephosphine P{(o-C6H4CH2)SiMe2H}3 (1) is shown to proceed with high yields from P(o-tolyl)3. Compound 1 coordinates to the Rh and Ir dimers [MCl(COD)]2 (M = Rh, Ir) in a tetradentate or tridentate fashion, depending on the strict exclusion of water. The dimeric compounds [ClM(SiMe2CH2-o-C6H4)2P(o-C6H4-CH2SiMe2H)]2, 2Rh and 2Ir, feature a tetradentate coordination of the starting ligand with P and two Si atoms as well as a non-classical agostic Si-H group. The presence of adventitious water in the solvents leads to the formation of two new complexes [(µ2-Cl)2M2(SiMe2CH2-o-C6H4)2P(o-C6H4-CH2SiMe2OSiMe2CH2-o-C6H4-)P(SiMe2CH2-o-C6H4)2], 3Rh and 3Ir, which feature a siloxane bridge through Si-H bond breaking in 2. Reaction of [RhCl(COD)]2 with the bisbenzylsilanephosphine PhP{(o-C6H4CH2)SiMe2H}2 leads to the formation of compound 4Rh which features also a dimeric structure with the SiPSi ligand coordinated through the two silicon atoms, one of which occupies the apical position of a square-pyramidal geometry in the solid state, while the second is disposed equatorially trans to π-donor Cl. Finally, bidentate coordination of a PSi ligand is achieved by reaction of [RhCl(COD)]2 with Ph2P{(o-C6H4CH2)SiMe2H} which leads to the monometallic species [RhCl(SiMe2CH2-o-C6H4-PPh2)2], 5Rh, incorporating two chelating PSi ligands and maintaining a Cl ligand.
RESUMO
The synthesis of the new phosphinodi(benzylsilane) compound PhP{(o-C6H4CH2)SiMe2H}2 (1) is achieved in a one-pot reaction from the corresponding phenylbis(o-tolylphosphine). Compound 1 acts as a pincer-type ligand capable of adopting different coordination modes at Ru through different extents of Si-H bond activation as demonstrated by a combination of X-ray diffraction analysis, density functional theory calculations, and multinuclear NMR spectroscopy. Reaction of 1 with RuH2(H2)2(PCy3)2 (2) yields quantitatively [RuH2{[η(2)-(HSiMe2)-CH2-o-C6H4]2PPh}(PCy3)] (3), a complex stabilized by two rare high order ε-agostic Si-H bonds and involved in terminal hydride/η(2)-Si-H exchange processes. A small free energy of reaction (ΔrG298 = +16.9 kJ mol(-1)) was computed for dihydrogen loss from 3 with concomitant formation of the 16-electron species [RuH{[η(2)-(HSiMe2)-CH2-o-C6H4]PPh[CH2-o-C6H4SiMe2]}(PCy3)] (4). Complex 4 features an unprecedented (29)Si NMR decoalescence process. The dehydrogenation process is fully reversible under standard conditions (1 bar, 298 K).
