Funktionelle Trimethylphosphanderivate, XXII [1] Struktur und Reaktivität von Lithium-tris(dimethylphosphino)methanid sowie Molekülstruktur von / Functional Trimethylphosphine Derivatives, X X II [1] Structure and Reactivity of Lithium-tris(dimethylphosphino)methanide and Molecular Structure of

Abstract

Abstract The reaction of Lithium-tris(dimethylphosphino)methanide with methyl iodide is sensitive to the choice of the solvent and reaction conditions; in pentane at room temperature and in the presence of tetramethylethylenediamine, Me3P = C(PMe2)2 is the major product, whereas in tetrahydrofuran, (Me2P)3C -CH3 is formed predominantly. Under similar conditions, Lithium-bis- (dimethylphosphino)methanide reacts with Mel to give (Me2P)2C(CH3)H as the main product. An X-ray structure determination of the tetrahydrofuran solvate of LiC(PMe2)3 reveals this compound to be dimeric with one solvent molecule coordinating to Li. A pseudo tetrahedral coordination sphere around each Li atom is completed by two phosphino groups of one [C(PMe2)3]- anion and a contact ion pair interaction with the carbanionoid center of the second. The crystals are monoclinic, space group P21/n, with a = 928.5(2), b = 1250.8(3), c = 1407.9(3) pm, β = 100.07(1)°, V = 1609.9 • 106 pm3 Dc = 1.13 g/cm3 for Z - 4 at -40 °C. Full-matrix least-squares refinement of 249 parameters based on 2158 reflections converged at R = 0.029. The ligand properties of (Me2P)3CCH3 are tested in its reactions with (CO)4Cr(C7H8) and (CO)5Cr[CH2S(O)Me2] from which and may be isolated. The latter crystallizes in the monoclinic space group P21/c with a - 1218.5(3). b = 881.7(3), c = 1824.1(4) pm, β = 106.66(2)°, V = 1877.6(9) • 106 pm3, Dc = 1.37 g/cm3 for Z = 4. Least-squares refinement of 218 parameters on 1615 reflections produced R = 0.063. The structure determination confirms the molecule to contain a five-membered heterocycle in an approximate envelope conformation.