Vier- und fünffach koordinierte Organometall-Phosphankomplexe von Aluminium, Gallium, Indium und Thallium / Four- and Five-Coordinate Organometal Phosphine Complexes of Aluminum, Gallium, Indium, and Thallium

Abstract

The organometal phosphine complexes ML 3 (L = [o-(Ph 2 PCH 2 )C 6 H 4 ] - ; M = Al 3+ , Ga 3+ , In 3a+ ) are obtained from MC1 3 and the lithiated ligand in diethyl ether. Tl[o-(Ph 2 PCH 2 )C 6 H4] 3 is prepared from T1C1 by a disproportionation reaction. M 1 species could not be detected with L as ligand. Al[o-(Ph 2 PCH 2 )C 6 H4] 3 is the first triorganoaluminum bis(phosphine) adduct where C 3 P 2 pentacoordination at aluminum has been definitely proven for both the solution (δ( 27 Al) =131 ppm, w 1/2 = 12 kHz) and the solid state (d(Al–P) = 2.676(3)/2.782(2) A). The trigonal-bipyramidal coordination geometry (C 3 P 2 ) at Al is achieved by two of the anionic phosphines acting as chelating ligands, spanning equatorial (C atoms) and axial sites (P atoms), while the third phosphine is only carbon-bonded. Like AlL 3 , the heavier congeners ML 3 (M = Ga, In, Tl) are stereochemically nonrigid molecules in solution. Surprisingly, in the solid state only InL 3 resembles the aluminum complex (C 3 P 2 penta-coordination) while GaL 3 and T1L 3 contain four-coordinate metal centers (C 3 P). This may be rationalized by the noticeably less polar Ga–P bonds as compared to Al–P and In–P bonds, while in T1L 3 the span of the ligand is not sufficient to allow for chelating coordination at a five- (or six-)coordinate Tl center.