Donor-assisted tetramethylaluminate/gallate exchange in organolanthanide complexes: pushing the limits of Pearson's HSAB concept.

La(GaMe(4))(3) and (C(5)Me(5))La(GaMe(4))(2) are obtained by reacting La(AlMe(4))(3) and (C(5)Me(5))La(AlMe(4))(2), respectively, with GaMe(3).OEt(2). Diethyl ether as a donor reverses the commonly observed Ln-GaR(4)--> Ln-AlR(4) transformation by producing the more stable AlMe(3).OEt(2), thus making homoleptic and half-sandwich tetramethylgallate complexes of the largest rare-earth metal accessible.