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 Na[BAr4f] and 4-picoline in dichloromethane proceeds via the known two-coordinate gallium cation [{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 [{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.

Substitution, abstraction and addition processes are shown to be viable chemistries for the modification of ligand systems featuring heavier group 13 element donor atoms. Thus, substitution of the pendant bromide in Cp∗Fe(CO)2In(Br)Mes∗ (1) gives Cp∗Fe(CO)2In(OC6H4tBu-4)Mes∗ (2), and sequential reaction of [Cp∗Fe(CO)2]2GaCl (3) with Na[BAr4f] and 4-picoline yields [{Cp∗Fe(CO)2}2(μ-Ga·4pic)]+[BAr4f]- (5). 2 and 5 have been fully characterized by spectroscopic and crystallographic methods.Figure optionsDownload as PowerPoint slide