Synthesis and structural elucidation of cage-shaped phosphonium trisphenolato gallium compounds

The reaction of GaX3 with the phosphorus-centered trisphenol (2-HO-3,5-tBu2-C6H2)3P, 1, affords the cage shaped phosphonium trisphenolates XGa{(2-O-3,5-tBu2-C6H2)3PH} (X = Et, 2; Cl, 3). The new compounds are C3 symmetric and isostructural with the previously reported aluminum analogs EtAl{(2-O-3,5-tBu2-C6H2)3PH}, 5, and ClAl{(2-O-3,5-tBu2-C6H2)3PH}, 6, but display longer M–O bonds due to the lower polarity of the Ga-O bonds. Compounds 2 and 3 were characterized by IR and multinuclear NMR spectrometry and mass spectrometry, and the crystal structure of compound 2 was also determined. No single products were observed in reactions aimed at the alcoholysis of the Ga-Et group in 2 as well as in attempts to abstract the ethide group with the trityl salt [Ph3C][B(C6F5)4] or Me3SiOTf (OTf = OSO2CF3), possibly a result of the lower polarity of Ga-C bonds.