64065-08-3Relevant articles and documents
Experimental and computational investigations of tautomerism and fluxionality in PCP- and PNP-bridged heavy chalcogenides
Elder, Philip J. W.,Chivers, Tristram,Thirumoorthi, Ramalingam
, p. 2867 - 2876 (2013)
The reaction of H2C(PCl2)2 with four equivalents of iPrMgCl produces H2C(PiPr2)2, which was treated with tellurium in boiling toluene, or selenium in toluene at room temperature, to give the monochalcogenides EPiPr2CH 2PiPr2 (E = Te, 4a; E = Se, 4b) in high yields. X-ray structural determinations show that 4a and 4b exist as the CH2 tautomers in the solid state with E-P-C-P dihedral angles of 56.1(2)° and 56.7(1)°, respectively. DFT calculations were carried out for the isolectronic series EPR2CH2PR2 and EPR 2NHPR2 (E = Se, Te; R = Me, iPr, tBu, Ph) and for their non-chalcogenated precursors in order to elucidate the factors that determine the preference for PH tautomers in some PNP-bridged systems. Compounds 4a and 4b were also characterized by multinuclear (1H, 13C, 31P, 77Se, 125Te) NMR spectroscopy. In solution, 4a exhibits fluxional behavior, which has been investigated by variable-temperature and variable-concentration multinuclear NMR spectroscopy. The observed behavior is consistent with an intermolecular tellurium transfer with an activation energy of 21.9 ± 3.2 kJ mol-1; consideration of selenium exchange in 4b indicates a much higher energetic barrier. DFT calculations provide insights into the pathway for the chalcogen exchange process in 4a (ΔE = 20.4 kJ mol-1). The outcome of reactions of 4a with selenium and nBuLi reflects the lability of the P-Te functionality. The monochalcogenides EPiPr2CH2PiPr 2 (E = Se, Te) exist as CH2 tautomers in the solid state; the contrast in this finding with that of the preferential formation of PH tautomers by PNP-bridged analogues is addressed through DFT calculations. In solution, the PCP-bridged tellurium derivative undergoes rapid intermolecular tellurium exchange with an activation energy of 21.9 ± 3.2 kJ mol -1. Copyright
Reactivity of the bridged-sulfide complex Pd2Cl 2(μ-S)(μ-dmpm)2 toward electrophiles
Pamplin, Craig B.,Rettig, Steven J.,Patrick, Brian O.,James, Brian R.
body text, p. 1991 - 2002 (2012/03/27)
The dipalladium(i) complex Pd2Cl2(dmpm)2 (1a) [dmpm = bis(dimethylphosphino)methane] is known to react with elemental sulfur (S8) to give the bridged-sulfide complex Pd2Cl 2(μ-S)(dmpm)2 (2a) but, in the presence of excess S8, PdCl2[P,S-dmpm(S)] (4a) and dmpm(S)2 are generated. Treatment of 1a with elemental selenium (Se8), however, gives only Pd2Cl2(μ-Se)(dmpm)2 (3a). Complex 4a is best made by reaction of trans-PdCl2(PhCN)2 with dmpm(S). Complex 2a reacts with MeI to yield initially Pd2I 2(μ-S)(dmpm)2 and MeCl, and then Pd2I 2(μ-I)2(dmpm)2 and Me2S, whereas alkylation of 2a with MeOTf generates the cationic, bridged-methanethiolato complex [Pd2Cl2(μ-SMe)(dmpm)2]OTf (5). Oxidation of 2a with m-CPBA forms a mixture of Pd2Cl 2(μ-SO)(dmpm)2 and Pd2Cl2(μ- SO2)(dmpm)2, whereas Pd2Br2(μ-S) (dmpm)2 reacts selectively to give Pd2Br 2(μ-SO)(dmpm)2 (6b). Treatment of the Pd 2X2(μ-S)(dmpm)2 complexes with X2 (X = halogen) removes the bridged-sulfide as S8, with co-production of PdII(dmpm)-halide species. X-ray structures of 3a, 5 and 6b are presented. Reactions of dmpm with S8 and Se8 are clarified. Differences in the chemistry of the dmpm systems with that of the corresponding dppm systems [dppm = bis(diphenylphosphino)methane] are discussed.
Catalytic (co)dimerization of alkyl acrylates
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, (2008/06/13)
The alkyl acrylates, e.g., methyl or ethyl acrylate, are improvedly dimerized, or codimerized with a conjugated diene, by contacting same with a catalytically effective amount of (a) at least one palladium source, (b) at least one organophosphorus(III) compound, and (c) at least one hydracid HY, the anion Y- of which does not coordinate with palladium ions.
