64065-08-3Relevant academic research and scientific papers
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
Preparation and Characterization of Co(III)-Dimethyldithiocarbamato Complexes Containing R2P(CH2)nPR2 (R=CH3, C6H5; n=1,2,3,4) and PR3 (R=C2H5, C6H5). Crystal Structure of 2>(BF4)2
Kita, Masakazu,Okuyama, Akiyoshi,Kashiwabara, Kazuo,Fujita, Junnosuke
, p. 1994 - 2001 (1990)
Twelve new cobalt(III)-phosphine complexes, 3-x>(3-x)+ (x=1,2; n=1,2,3), >(+) (n=1,2,3,4), and trans-(+) (R=C2H5, C6H5) were prepared, where dtc denotes dimethyldithiocarbamate(1-).The molecular structure of 2>(BF4)2 was determined by X-ray analysis.Crystal data are monoclinic, space group Cc, a=15.927(4), b=11.726(2), c=14.422(7) Angstroem, β=91.38(3) deg, V=2692.6(15) Angstroem3, Z=4, R=0.058 for 225l reflections.The complex ion forms a distorted octahedron with the sm all P-Co-P (73.1(2) and 75.5(2) deg) and S-Co-S (75.97(9) deg) chelate angles.The mean Co-P and Co-S distances are 2.238(5) and 2.285(3) Angstroem, respectively.On the basis of the angular overlap model (AOM) treatment, the ligand field bands were assigned and the effect of ring size of diphosphine chelates on these bands are examined.Positive e?(P) values were necessary to satisfy the observed data, and the result indicates that the Co-d? orbitals are destabilized by coordination of the phosphine ligand.
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.
α-Stabilization by Silyl and Phosphino Substitution
Roemer, Bettina,Gatev, Geo G.,Zhong, Meili,Brauman, John I.
, p. 2919 - 2924 (2007/10/03)
The electron affinity of the bis(dimethylphosphino)methyl radical was measured to be 35.3+/-0.2 kcal/mol, using electron photodetachment spectroscopy in an ion cyclotron resonance spectrometer.Using equilibrium measurements, ΔHacido of bis(dimethylphosphino)methane and bis(trimethylsilyl)methane was determined to be 370+/-3 and 373+/-3 kcal/mol, respectively.From measured and known electron electron affinities and gas-phase acidities, we derive C-H bond dissociation energies: bis(dimethylphosphino)methane, 92+/-3 kcal/mol, and bis(trimethylsilyl)methane, 95+/-3 kcal/mol. ΔHacido of trimethylphosphine was bracketed at 383-387 kcal/mol.The α-stabilization effect of silyl and phosphino substitution is large and comparable in size to stabilization by thio and chloro substitution.Possible mechanisms of stabilization 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.
Oligophosphaalkanes, VI. Syntheses and NMR Spectroscopic Characterization of PH-functional Methylene Bridged Diphosphanes R2P-CH2-PRH and HRP-CH2-PRH
Hietkamp, Sibbele,Sommer, Herbert,Stelzer, Othmar
, p. 3400 - 3413 (2007/10/02)
1,3-Diphosphapropane, H2P-CH2-PH2 (1) was synthesized in about 40 percent yield by reduction of Cl2P-CH2-PCl2 with LiAlH4.The mono-, di-, and tri-substituted derivatives RHP-CH2-PH2 (R = iPr, CH2Ph, 3a, b) RHP-CH2-PHR (R = iPr, CH2Ph, tBu, 5a - c), R2P-CH2-PRH (R = Me, iPr, CH2Ph, 10b, 7a, b) are accessible using Cl2P-CH2-PCl2 as a starting material.A multiple stage synthesis based on MePCl2 affords the disecondary phosphane MeHP-CH2-PMeH (10d), which in contrast to reports given in the literature is thermally stable to at least 100 deg C.The 31P and 1H NMR spectra of 1 have been analyzed and simulated by use of computer programs.The structure of the phosphanes is discussed on the basis of their 1H, 31P, 31P, and 13C NMR spectra.
Alkyl Substituted Diphosphinomethanes: Mixed Cl/t-Bu and Me/CH2SiMe3 Derivatives
Karsch, Hans H.
, p. 1027 - 1030 (2007/10/02)
The syntheses of (t-Bu)2PCH2P(t-Bu)2 and (PhO)2PCH2P(OPh)2 and an improvement of the synthesis of Me2PCH2PMe2 are described.Mixed Me/CH2SiMe3 and Cl/t-Bu diphosphinomethane derivatives are characterized by means of NMR spectroscopy. - Key words: Diphosphi
Functional Derivatives of Trimethylphosphane, XV. (Chloromethyl)dimethylphosphane
Karsch, Hans Heinz
, p. 823 - 827 (2007/10/02)
(Chloromethyl)dimethylphosphane, Me2P(CH2Cl) (3), which is unstable at room temperature, has been synthesized.Reactions with O2, CH3Br and LiPMe2 give Me2P(O)(CH2Cl) (4), Br (5b) and Me2PCH2PMe2 (2), respectively.NMR data for these and related compounds are given.
