Synthesis and structure of a gallate of strontium with Sr–C–Ga three-center two-electron bonds

The addition reaction of strontium bis[bis(trimethylsilyl)amide] with triethylgallane yields quantitatively strontium bis[triethyl-bis(trimethylsilyl)aminogallate] (1). The strontium cation shows the unusual low coordination number of four to two nitrogen and two carbon atoms. Sr–C bond lengths with a mean value of 282 pm are observed with the Sr–C–Ga three-center two-electron bonds. Due to the mainly ionic character of this compound a fast exchange of the bridging and terminal ethyl groups is observed on the NMR time scale.