Syntheses and Crystal Structures of Intramolecularly Stabilized Organogallium Compounds Containing an o-Carboranyl C,N-Chelating Ligand System

The reaction of HCab N ( 1; HCab N = closo -1-[(dimethylamino)methyl]- o -carborane) with GaCl 3 yielded the simple Lewis acid−base adduct complex HCab N ·GaCl 3 ( 3 ). The reaction of LiCab N ( 2; LiCab N = closo -1-[(dimethylamino)methyl]-2-lithio- o -carborane) with GaCl 3 in a 1:1 ratio produced the four-coordinated metallacyclic organogallium compound Cab N GaCl 2 ( 4 ), in which the gallium atom was stabilized via intramolecular C,N-coordination. A similar intramolecularly base-stabilized four-coordinated gallane, Cab N GaMe 2 ( 5 ), was synthesized from the reaction of 2 with Me 2 GaCl. Complex 5 was also formed upon reaction of the complex 4 with 2 equiv of LiMe. The X-ray structural studies of complexes 4 and 5 indicate that the gallium atom is located in the center of a distorted tetrahedron. The Lewis acid 4 added the base pyridine to yield the adduct Cab N GaCl 2 ·NC 5 H 5 ( 6 ). The trigonal-bipyramidal coordination of the metal center was proven by the single-crystal X-ray determination of the complex 6 . The reaction of LiCab N ( 2 ) with GaCl 3 in a 2:1 ratio afforded the bis[((dimethylamino)methyl)- o -carboranyl]gallium compound (Cab N ) 2 GaCl ( 7 ). The NMR spectra revealed that intramolecular Ga−N coordination occurs in solution, resulting in a pentacoordinate (Cab N ) 2 GaCl structure. Crystals of (Cab N ) 2 GaCl(H 2 O) ( 8) were obtained while recrystallizing 7 in toluene over a period of several days. X-ray analysis of this complex 8 provides support for the assignment of the water-coordinated bis[((dimethylamino)methyl)- o -carboranyl]gallane structure.