Substitution, abstraction and addition chemistry of low-coordinate gallium and indium ligand systems

Substitution, abstraction and addition processes have been shown to be viable chemistries for the modification of ligand systems featuring heavier group 13 element donor atoms. Thus substitution of the bromide in Cp∗Fe(CO)2In(Br)Mes∗ (1) can be carried out with retention of the Fe–In bond, using 1 equiv. of the aryloxide nucleophile [OC6H4tBu-4]− to give Cp∗Fe(CO)2In(OC6H4tBu-4)Mes∗ (2). Structural and spectroscopic comparisons of 1 and 2 reveal that variation in the steric and/or π donor properties of the indyl ligand substituents have little effect on the nature of the Fe–In bond. Sequential reaction of [Cp∗Fe(CO)2]2GaCl (3) with the halide abstraction agent View the MathML sourceNa[BAr4f] and 4-picoline in dichloromethane proceeds via the known two-coordinate gallium cation View the MathML source[{Cp∗Fe(CO)2}2(μ-Ga)]+[BAr4f]- (4). The net result is replacement of the gallium bound chloride substituent with a 4-picoline moiety, yielding View the MathML source[{Cp∗Fe(CO)2}2(μ-Ga·4pic)]+[BAr4f]- (5) via a two-step abstraction/addition process. 5 represents only the second structurally characterized complex containing a cationic three-coordinate gallium centre, and the first displaying bonds to a transition metal.