Thermal treatment of [Os3(CO)12] with diphenyl(2‐thienyl)phosphane, Ph2P(C4H3S), results in the formation of [Os3(CO)12–x{Ph2P(C4H3S)}x] (x = 1–3, 1–3), but no C–H bond activation was observed. Reaction of [H2Os3(CO)10] with diphenyl(2‐thienyl)phosphane at ambient temperature affords [HOs3(μ‐H)(CO)10{Ph2P(C4H3S)}] (4), but when the samereaction is repeated at elevated temperatures, the cyclometallated species [(μ‐H)Os3(CO)9{μ3‐Ph2P(C4H2S)}] (5) and[(μ‐H)Os3(CO)8{μ3‐Ph2P(C4H2S)}{Ph2P(C4H3S)}] (6) are formed. In addition, two more products, tentatively assigned as [(μ‐H)Os3(CO)6{μ3‐Ph2P(C4H2S)}{μ‐Ph2P(C4H3S)}{Ph2P(C4H3S)}] (7) and [(μ‐H)Os3(CO)7{μ‐Ph2P(C4H2S)}{μ‐Ph2P(C4H3S)}{Ph2P(C4H3S)}] (8) are obtained. The dynamic behaviours of 2, 5 and 6 have been studied by variable‐temperature (VT) 1H and 31P{1H} NMR spectroscopy. The VT 31P{1H} NMR spectra of [Os3(CO)10{Ph2P(C4H3S)}2] (2) demonstrate that a mixture of two isomers, which are in rapid exchange at room temperature, is present and that the less common cis‐trans isomer, whose structure has been determined by X‐ray crystallography, is favoured for this cluster. The VT 1H NMR spectra of 5 indicate the presence of two isomers which are proposed to arise from an oscillation of the σ,η2‐vinyl group of the thienyl moiety between two metal atoms. A similar fluxional process is proposed to occur in 6 and the assignment of the room‐temperature structure(s) of this cluster was confirmed by 1H‐187Os 2D HMQC spectroscopy. In addition to 2, the solid‐state structures of 3, 5 and 6 have been determined by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A series of unsymmetrical PCN pincer ligands (1-(3-((di-tert-butylphosphino)methyl)phenyl)-N,N-dialkylmethanamine) were cyclometalated with palladium to generate a series of new PCN supported Pd(II) chloro complexes, (PCN)PdCl (4–6), where alkyl = methyl, ethyl, and n-propyl, which were fully characterized by NMR spectroscopy and X-ray crystallography. The N,N-dimethyl complex 4 reacts with methyl lithium to give the corresponding methyl and dimethyl complexes (PCN)PdMe (12) and Li[(PCN)PdMe2] (13), which could not be isolated but were characterized in solution. The substitution reactions of (PCN)PdCl (4–6) with iodide to form the corresponding iodo complexes (PCN)PdI (7–9) were investigated by use of UV–vis stopped-flow spectrophotometry. The experiments were performed in methanol over a temperature range from 293 to 325 K. The reactions are reversible and were shown to proceed exclusively via the solvento complex in two reversible consecutive steps. Activation parameters for both the forward and reverse reactions were determined, and they, together with reactivity trends, support an associative pathway. No displacement of the nitrogen donor was detected, and overall this points to a limited hemilability of the ligands on palladium.
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