- Synthesis, characterization and DFT studies of electron-rich iridium(I) carbonyl complexes of an unsymmetrical phosphine–phosphine monoselenide ligand and their reactivity towards alkyl halides
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A series of halocarbonyliridium(I) complexes of the type [Ir(CO)(P ~ Se)2X] (1) {where P-Se = 1,2-bis(diphenylphosphinomethaneselenide); X = Cl (1a), Br (1b), I (1c)} have been synthesized by the reaction of [Ir(CO)2X2]? with the ligand Ph2PCH2P(Se)Ph2. The complexes exhibit a single ν (CO) band in the region 1926 cm?1 which is significantly lower in frequency compared to Vaska's complex, trans-[Ir(CO)Cl(PPh3)2] (1965 cm?1), and substantiate the enhanced electron density at the metal centre. The complexes undergo oxidative addition (OA) reactions with electrophiles like CH3I and C2H5I to form Ir(III) alkyl species like [Ir(CO)R(P ~ Se)2IX]; [R = CH3 (2), C2H5 (3)] which exhibit ν (CO) bands in the region of 2070 cm?1. Kinetic measurements for the CH3I oxidative addition with complex 1a indicate a first order reaction. The complexes have been characterized by elemental analyses, IR and NMR spectroscopy. Density functional calculations reveal that the activation barrier for the OA is the lowest with 1a, which is also in tune with the experimental observations.
- Guha, Ankur Kanti,Nath, Jayashree,Saikia, Lakshi,Sarmah, Bhaskar Jyoti
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- Oxotrihalogenoselenates(IV): Preparation, Structure and Properties of P(C6H5)4SeOCl3, P(C6H5)4SeOBr3 and As(C6H5)4SeOBr3
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The novel oxotribromoselenate(IV) SeOBr3(-) anion was prepared from the reaction of stoichiometric quantities of SeOBr2 and bromide in acetonitrile solution, and it was isolated as the tetraphenylphosphonium and -arsonium salts in crystalline form.For the synthesis of the analogous SeOCl3(-) as P(C6H5)4SeOCl3, SeCl4 was reacted in the presence of a small quantity of H2O with P(C6H5)4Cl in acetonitrile.Complete X-ray structural analyses of P(C6H5)4SeOCl3 (space group P, a = 10.981(3), b = 11.059(3), c = 10.358(3) Angstroem, α = 73.77(2) deg, β = 83.33(2) deg, γ = 80.51(2) deg, V = 1187.9(6) Angstroem3) and of P(C6H5)4SeOBr3 (space group P21/c, a = 11.719(4), b = 16.088(4), c = 13.124(4) Angstroem, β = 94.72(3) deg, V = 2466(1) Angstroem3) show dimeric centrosymmetric Se2O2Cl6(2-) and Se2O2Br6(2-) anions being present in the solid.In the anions two square-pyramidal (ψ-octahedral) SeOHal4 groups are connected through a common Hal-Hal edge.The axial oxygen ligands (Se-O: 1.597(4) and 1.584(6) Angstroem) cause a pronounced sterochemical trans-activation of the inert pairs at the Se atoms.As(C6H5)4SeOBr3 is isotypic with P(C6H5)4SeOCl3. - Key words: Oxohalogenoselenate, Crystal Structure, Selenium
- Krebs, Bernt,Schaeffer, Andreas,Hucke, Marita
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p. 1410 - 1417
(2007/10/02)
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- Synthesis of Some Dicyclohexyltin(IV) and Cyclohexylphenyltin(IV) Anionic Complexes
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Tetraalkylammonium, R4N (R = CH3, C2H5 or C4H9) and tetraphenyl-phosphonium, -arsonium and -stibonium salts of dicyclohexyl, dicyclohexylphenyl and cyclohexyldiphenyltin(IV)-halo or halo-pseudohalo anions nPh3-nSnX2 and CynPh3-nSnXY, where Cy = cyclo-C6H11, X = Cl, Br, I, N3 or NCS; Y = Br, I or NCS and n = 1 or 2> have been synthesised and characterized on the basis of melting points, elemental analyses and infrared spectra.Conductance measurements and values of Van't Hoff factor (i) suggest the presence of complex anions in the solution.Attempts to obtain complexes of the type and have been unsuccessful.
- Bhattacharya, S. N.,Raj, Prem,Awasthi, V. K.
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p. 592 - 594
(2007/10/02)
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