Syntheses and crystal structures of intramolecularly stabilized organo aluminum, gallium, and indium compounds containing the C,P-chelating o-carboranylphosphino ligand [o-C2B10H10(CH2PMe2)-C,P]- (CabC,P).: X-ray structure of pentacoordinated group 13 metal complexes (CabC,P)2MX (M = Ga, In; X = Cl)

The new phosphino-o-carborane ligand HCab(P) (1; Cab(P) = closo-1-[(dimethylphosphino)methyl]-1,2-dicarbaborane) with substitution at the carbon and phosphorus atoms was used for the synthesis of the C,P-chelated bis(phosphino-o-carborane) group 13 metal complexes (Cab(C,P),P)(2)MX (4). Reaction of LiCab(C,P) (2; LiCab(C,P) = closo-1-[(dimethylphosphino)methyl]-2-lithio-o-carborane) with MX3 (M = Al, Ga, In; X = Cl, Br) in a 1:1 molar ratio produced the tetracoordinated metallacyclic compound (Cab(C,P))MX2 (3), in which the metal atom was stabilized via intramolecular C,P-coordination. The corresponding bis-chelate complexes, (Cab(C,P))(2)MX (4), were synthesized by reacting 3 with an additional C,P-chelate ligand 2. Complexes 4 were also formed upon reaction of 2 with MX3 in a 2:1 molar ratio. The H-1 and C-13 NMR spectra of 4 revealed that intramolecular M-P coordination occurs in solution, resulting in the formation of pentacoordinated complexes (Cab(C,P))(2)MX (4). The trigonal bipyramidal (tbp) coordination of the metal center was confirmed by single-crystal X-ray determination of the complexes (Cab(C,P))(2)GaCl (4b) and (Cab(C,P))InCl (4c). Similar intramolecularly base-stabilized gallanes, (Cab(C,P))GaMe2 (5b) and (Cab(C,P))(2)GaMe (6b), which were tetra- and pentacoordinated, respectively, were synthesized from the reaction of 3b and 4b with LiMe or MeMgBr. The Lewis acid 3b added the base PMe3 to yield the pentacoordinated adduct (Cab(C,P))GaCl2 center dot PMe3 (7b). The H-1 and C-13 NMR spectra revealed that intramolecular Ga-P coordination occurs in solution, resulting in a pentacoordinated structure.