- Synthesis and characterization of new RhI complexes bearing CO, PPh3 and chelating P,O- or Se,Se-ligands: Application to hydroformylation of styrene
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The complexes [Rh(CO)(PPh3){Ph2PNP(O)Ph2-P,O}] (3), [Rh(CO)2{Ph2P(Se)NP(Se)Ph2-Se,Se′ }] (5), and [Rh(CO)(PPh3){Ph2P(Se)NP(Se)Ph2-Se,Se ′}] (6), were synthesised by stepwise reactions of CO and PPh3 with [Rh(cod){Ph2PNP(O)Ph2-P,O}] (2) and [Rh(cod){Ph2P(Se)NP(Se)Ph2-Se,Se′}] (4), respectively. The complexes 3, 5 and 6 have been studied by IR, as well as 1H and 31P NMR spectroscopy. The ν(CO) bands of complexes 3 and 6 appear at approximately 1960 cm-1, indicating high electron density at the RhI centre. The structure of complexes 3 and 6 has been determined by X-ray crystallography, and the 31P NMR chemical shifts have been resolved via low temperature NMR experiments. Both complexes exhibit square planar geometry around the metal centre, with the five-membered ring of complex 3 being almost planar, and the six-membered ring of complex 6 adopting a slightly distorted boat conformation. The C-O bond of the carbonyl ligand is relatively weak in both complexes, due to strong π-back donation from the electron rich RhI centre. The catalytic activity of the complexes 2, 3 and 6 in the hydroformylation of styrene has been investigated. Complexes 2 and 3 showed satisfactory catalytic properties, whereas complex 6 had effectively no catalytic activity.
- Chatziapostolou, Konstantinos A.,Vallianatou, Kalliopi A.,Grigoropoulos, Alexios,Raptopoulou, Catherine P.,Terzis, Aris,Kostas, Ioannis D.,Kyritsis, Panayotis,Pneumatikakis, Georgios
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p. 4129 - 4138
(2008/02/10)
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- Late transition-metal complexes with the heterofunctional phosphine Ph2PNHP(O)Ph2
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The complexes [MCl(cod)(HL)] (M = Rh or Ir), [PdCl(η3-C3H5)(HL)], [PdCl(L-L)(HL)], trans-[RhCl(CO)(HL)2] and [AuCl(HL)] have been synthesised by reaction of either [{M(μ-Cl)(cod)}2] (M = Rh or Ir; cod = cycloocta-1,5-diene), [{Pd(μ-Cl)(η3-C3H5)}2], [{Pd(μ-Cl)(L-L)}2] (L-L = C12H12N, C10H8N or C9H12N), [{Rh(μ-Cl)(CO)2}2] or [AuCl(tht)] (tht = tetrahydrothiophene) with Ph2PNHP(O)Ph2 (HL). In all these complexes the ligand is monodentate P-bound. Chloride abstraction from [PdCl(C12H12N)(HL)] or [PdCl(η3-C3H5)(HL)], using Ag[BF4], gave the cationic compounds [Pd(C12H12N)(HL)][BF4] or [Pd(η3-C3H5)(HL)][BF4] in which the ligand HL is P,O-chelated. Removal of the amine proton in metal complexes of HL (monodentate P-bound) with KOBut afforded a new class of neutral metallacycles incorporating either an MP2NO or M2P4N2O2 framework based on the [Ph2PNP(O)Ph2]- (L-) ligand. Reaction of [{Pd(μ-Cl)-(C9H12N)}2] with 4 equivalents of HL in methanol at ambient temperature yielded the neutral palladium(II) complex [PdCl{Ph2PNP(O)Ph2-P,O}(Ph2POMe)] in which one HL ligand has undergone P-N bond scission. The reaction of the iridacycle [Ir(COd){Ph2PNP(O)Ph2-P,O}] with MeI was shown to proceed with cis addition affording the iridium(III) metallacycle [IrI(Me)(cod){Ph2PNP(O)Ph2-P,O}]. All compounds described have been characterised by a combination of 31P-{1H} NMR spectroscopy, microanalysis and in some cases by 1H NMR and IR spectroscopy. The molecular structures of four complexes have been determined by single-crystal X-ray diffraction. The metallacycles show π-electron delocalisation in the P-N-P-O fragment.
- Slawin, Alexandra M. Z.,Smith, Martin B.,Woollins, J. Derek
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p. 1283 - 1293
(2007/10/03)
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