π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

A review of the study titled 'π-bonding and the lone pair effect in multiple bonds between heavier main group elements', focusing on the synthesis, structure, and bonding of stable compounds of heavier main group elements, is presented. It is found that the red aluminum derivative is generated in solution by a reduction process and this highly reactive molecule undergoes rapid cyclization in toluene. The parent metal amides and related derivatives are prepared by photolysis of Al, Ga, or In atoms and isolated in NH 3-doped frozen argon matrixes. The first experimental evidence for a transiently formed silicon-carbon double bond was depicted through pyrolysis of 1,1-dimethyl-1-silacyclobutane, forming 1,1-dimethylsilene as a transient intermediate. The trisila-allene is characterized by short Si-Si distances of 2.179(3) and 2.206(3) Å, in contrast to the lighter homologues which display a strictly linear arrangement of a bent trisila array.