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 ) 2 MX ( 4 ). Reaction of LiCab C,P ( 2; LiCab C,P = closo -1-[(dimethylphosphino)methyl]-2-lithio- o -carborane) with MX 3 (M = Al, Ga, In; X = Cl, Br) in a 1:1 molar ratio produced the tetracoordinated metallacyclic compound (Cab C,P )MX 2 ( 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 MX 3 in a 2:1 molar ratio. The 1 H and 13 C 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 ) 2 InCl ( 4c ). Similar intramolecularly base-stabilized gallanes, (Cab C,P )GaMe 2 ( 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 PMe 3 to yield the pentacoordinated adduct (Cab C,P )GaCl 2 ·PMe 3 ( 7b ). The 1 H and 13 C NMR spectra revealed that intramolecular Ga−P coordination occurs in solution, resulting in a pentacoordinated structure.