From gallium hydride chlorides to molecular gallium sulfides

In an effort to prepare molecular components for the construction of larger aggregates - from nanostructures to multidimensional arrays - of gallium sulfide, the chemistry of the (chloro)gallium hydrides GaH n Cl 3 - n hasbeen developed further and employed for selective substitution reaction. The synthetic pathways to [HGaCl 2 ] 2 have been optimized and the structure of the crystalline product determined. The dinuclear compound was converted into mononuclear 1:1 complexes with series of both tertiary phosphines and substituted pyridines. The complexes are stable and soluble in common organic solvents to allow efficient purification. The crystal structures of selected examples have been determined including those of coordination compounds of ditertiary phosphines. Reference compounds with GaCl 3 and GaH 3 have also been prepared and fully characterized. On controlled thermal decomposition, the HGaCl 2 complexes undergo dehydrogenative coupling to give almost quantitative yields of GaCl 2 complexes which are diamagnetic dinuclear species with a Ga-Ga single bond, as demonstrated for phosphine and pyridine adducts. The 2:1 complex of GaH 3 with 2,4dirnethylpyridine undergoes an internal 1,4-hydrogallation reaction to afford the 4-hydro-pyridyl-(pyridine)gallium dihydride. (HGaCl 2 ) 2 can be readily converted into ternary compounds [GaYX] which are soluble in pyridines (L) as the trinuclear complexes [GaYX(L)] 3 with X = Cl, Br and Y = S, Se. Their molecular structures (six-membered rings) and conformations have been determined. With excess ligand L, these trinuclear compounds can be transformed into bicyclic tetranuclear dications of the type [Ga 4 Y 5 (L) 6 ] 2 + and finally into molecular species [Ga 4 Y 6 (L) 4 ] containing e.g. molecular gallium sulfide Ga 4 S 6 as a soluble pyridine complex.