The utilization of sterically demanding ligands in the stabilization of main group metal complexes

The syntheses and molecular structures of group 13 and 15 organometallic complexes are presented herein. Five different ligand systems were employed in this work: (1) tetraphenylbutadienyl; (2) pentamethylphenyl; (3) adamantyl; (4) ferrocenyl; and (5) triphenylmethyl. The tetraphenylbutadienyl ligand has previously been used to isolate the first spirogallane as well as a number of interesting group 14 organometallic complexes. Utilizing 1,4-dilithiotetraphenylbutadiene with MX3 (M = P or B; X = Br) yields a novel diphosphine, [(Ph4C4)PP(C4Ph4)] I, and the fused-ring borane [(Ph4C4)2(C2H5)]B II. Using both organolithium and organomagnesium derivatives of the pentamethylphenyl ligand, various aluminum and gallium complexes have been isolated (III-V). These complexes possess dihedral angles which distinguish them from previous complexes which have employed phenyl-based ligands. The reaction of adamantylmagnesium bromide with AlCl3, GaCl3, Me2GaCl, and Me2AlCl gives complexes which are the first examples of adamantyl-based group 13 organometallic compounds (VI-IX). These ionic main group complexes possess not only main group adamantyl anions, but also unusual trimetallic magnesium cluster cations. The use of the ferrocenyl and triphenylmethyl moieties as ligands is also explored in this work. These molecules, although not traditionally thought of or used as ligands, are potentially useful due to their interesting structural features.