From gallium hydride halides to molecular gallium sulfides

摘要

Complexes of the type (L)GaHCl2, with L tertiary phosphines or pyridines, have been prepared from (HGaCl2)(2) and the ligands in diethyl ether. The products are stable crystalline solids soluble in common organic solvents. The presence of the Ga-H function has been confirmed by IR and NMR spectroscopy and by single crystal X-ray diffraction, carried out for the 1:1 adducts with L PCy3 and PPh3 (two polymorphs) and for the 2:1 adduct with L (CH2PPh2)(2) (dppe, two different solvates). The reaction of PVi(3) with (HGaCl2)(2) gives an insoluble polymer owing to the hydrogallation of vinyl groups by the gallium hydride units (no Ga-H functions are left in the product). Treatment of the complexes (R3P)GaHCl2 with H2S, metal sulfides or (Me3Si)(2)S gave only in soluble, ill-defined products. - The 1: 1 adduct (L')GaHCl2, with L' = 4-dimethylamino-pyridine, reacts with (Me3Si)(2)S in acetonitrile at ambient temperature to give an only partially sulfur-substituted product of the net formula (U)GaSH0.66Cl0.34. With excess ligand U, under reflux conditions and after longer reaction times, a pyridine complex of the tetranuclear, molecular gallium sulfide Ga4S6 is obtained in low yield. The core of the compound with the composition (L')(4)Ga4S6 has an adamantane structure resembling a cluster unit of the binary gallium sulfide polymorphs Ga2S3. The edge-sharing Ga3S3 six-membered rings are all in a chair conformation as found previously for the pyridine complexes of the ternary compounds [(L)GaEX](3)(with E = S, Se and X = Cl, l3r) and for the bicyclic dication [(L)(6)Ga4S5](2+). Thermolysis and degradation under mass spectrometry conditions lead to sublimation of U and leave amorphous Ga2S3. The reaction of (L')GaCl3 with (Me3Si)(2)S did not afford any molecular gallium sulfide complex. A comparison of the structural data for (L')GaCl3 and (L')(4)Ga4S6 suggests a much poorer acceptor character of the gallium sulfide cluster.