- Bond activation in iron(II) and nickel(II) complexes of polypodal phosphanes
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A pyridine-derived tetraphosphane ligand (donor set: NP4) has been found to undergo remarkably specific C-P bond cleavage reactions, thereby producing a ligand with an NP3 donor set. The reaction may be reversed under suitable condit
- Gentschow, Simon-Andreas,Kohl, Stephan W.,Bauer, Walter,Heinemann, Frank W.,Wiedemann, Dennis,Grohmann, Andreas
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- Electron-Rich Compounds with Thiophosphinamide, Carboxamide, O-Silylurethane, and O-Silylisourea Functionality. Synthesis, Spectroscopy, Chemical and Electrochemical Reactivity
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1,4-Dihydropyrazines with the N,N'-substituents C(O)OSiMe3 (5), C(NPh)OSiMe3 (6), P(S)Me2 (7) and C(O)Me (9) have been synthesized by reductive addition to pyrazine (7, 9) or by insertion of CO2 (5) or phenyl isocyanate (6) into the N-Si bonds of the N,N'-bis(trimethylsilyl) derivate 3.At room temperature, 1H-NMR spectroscopy reveals hindered rotation around the N-C(=X) "single" bonds in compounds 5, 6, and 9 but not in 7 or in the C(O)NMe2-disubstituted compound 8.NMR shifts, colours, the oxidation potentials from cylic voltammetry, and the reactivity towards air and TCNE illustrate that the electron-withdrawing capability increase in the substituent order SiR3 C(O)OSiMe3 C(NPh)OSiMe3 ca.P(S)Me2 C(O)Me.Notwithstanding, the N,N'-bis(thiophosphinyl) (7) and the N,N'-diacetyl derivative 9 are easily converted to persistent radical cations whereas the O-silylated compounds 5 and 6 are only irreversibly oxidized albeit at very low potentials. - Key Words: Pyrazines / Organosilicon compounds / Organophosphorus compounds / Electrochemistry / ESR spectroscopy
- Bessenbacher, Christian,Kaim, Wolfgang,Stahl, Thomas
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p. 933 - 940
(2007/10/02)
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- Magnetic properties of anhydrous and hydrated dimethylphosphinates of manganese(II). The crystal and molecular structure of poly-bis(μ-dimethylphosphinato)diaquomanganese(II)
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The dimethylphosphinate of manganese(II), Mn2, and its dihydrate have been prepared and studied using magnetic susceptibility, differential scanning calorimetry,and electronic and vibrational spectroscopic methods.The dihydrate was obtained in crystalline form and a single crystal X-ray diffraction study revealed a polymeric structure.Crystals of poly-bis(μ-dimethylphosphinato)diaquomanganese(II) are monoclinic, a = 20.722(3), b = 4.8652(2), c = 11.0689(14) Angstroem, β = 102.209(7) deg, Z = 4, space group C2/c.The structure was solved by conventional heavy-atom methods and was refined by full-matrix least-squares procedures to R = 0.030 and Rw = 0.033 for 983 reflections with I >/= 3?(I).The structure consists of infinite centrosymmetric chains of Mn(II) atoms linked by double phosphinate bridges and extending along the crystallographic b axis.The water molecules are involved in both interchain and bifurcated intrachain hydrogen bonding (O...O = 2.734(2), 2.899(3) and 3.120(3) Angstroem).The coordination about Mn is slightly distorted octahedral with libration-corrected bond lenghts Mn-O(phosphinato) = 2.156(2) and 2.212(2), Mn-OH2 = 2.247(2) Angstroem.Magnetic susceptibility studies on the dihydrate from 300 to 4.2 K reveal a magnetic moment of ca. 5.9 BM over most of the range and give no evidence for significant magnetic exchange.The anhydrous compound, which is considered on the basis of indirect evidence to retain the double phosphinate bridged structure exhibited by the dihydrate, shows relatively strong antiferromagnetic behaviour.The data have been analyzed according to two theoretical models both of which employ the isotropic Heinsenberg Hamiltonian.The scaling model of Wagner and Friedberg gives J = -2.94 cm-1 and g = 2.02 and the interpolation scheme of Weng gives J = -2.69 cm-1 and g = 2.01.The manitude of the exchange coupling is considered in relation to that observed in related manganese compounds and possible reasons for the observed damping of the exchange on hydration are discussed.
- Cicha, Walter V.,Haynes, John S.,Oliver, Katherine W.,Rettig, Steven J.,Thompson, Robert C.,Trotter, James
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p. 1055 - 1062
(2007/10/02)
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- Ligating Properties of t-Phosphine/Arsine Sulphides and Selenides: Part VIII - Synthesis and Characterization of Mercury(II) Complexes with Some Ditertiaryphosphine Disulphides
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Ditertiaryphosphine sulphides, namely, 1,1-methylene(MDPS)-, 1,2-dimethylene(EDPS)-, 1,3-trimethylene(PDPS)- and 1,4-tetramethylene(BDPS)-bis(diphenylphosphine sulphides) react with mercury(II) nitrate in acetone forming complexes of the type Hg(NO3)2.L.Tetramethyldiphosphine disulphide(TMDPS) gives 1:1 adduct with mercury(II) bromide and 3:2 adduct (metal:ligand) with mercury(II) chloride and iodide.Characterization of the complexes has been carried out on the basis of their elemental analyses, IR spectra and molar conductances in nitrobenzene.All the adducts are non-electrolytes.Complexes of TMDPS and MDPS, forming five- and six-membered rings, have been assigned chelated tetrahedral stereochemistry, while the complexes of EDPS, PDPS and BDPS have been assigned polymeric structures.
- Lobana, T. S.,Sharma, K. B.
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p. 710 - 711
(2007/10/02)
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- Phosphorus-Phosphorus Nuclear Spin Coupling in Tetraorganobiphosphines and Some of Their Derivatives
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The signs and magnitudes of (31)P-(31)P and (31)P-H spin coupling constants in tetraorganobiphosphines RR'PPRR' with Me, Ph, and/or Bu-t as substituents, and in their sulphides and selenides RR'P(X)P(X)RR' (X = S or Se), have been determined by (1)H- heteronuclear double resonance.Large variation in (1)J((31)P-(31)P) arise as a result of changes in the phosphorus hybridization and/or effective nuclear charge, and smaller variations as a result of changes in the position of rotameric equilibrium in the gauche conformers of the biphosphines.
- McFarlane, H. Christina E.,McFarlane, William,Nash, John A.
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p. 240 - 244
(2007/10/02)
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