SURFACE ORGANOMETALLIC CHEMISTRY OF TIN - CONTROLLED THERMAL TRANSFORMATION IN VACUO OF SN(N-C4H9)(3) FRAGMENTS GRAFTED ON THE SURFACE OF ALUMINA

The thermal transformation in vacuo of the well defined surface organo metallic fragments [AlO]Sn-x(n-C4H9)(3) (x = 1, 2) 1 grafted on variou s partially dehydroxylated aluminas (alpha, gamma, eta) has been inves tigated. The surface reactions were followed by qualitative and quanti tative determination of the evolved gases including IR spectroscopy, C -13 cross-polarisation magic angle spinning and Sn-119 magic angle spi nning NMR studies. On all aluminas, comparable transformations of 1 we re identified showing that the ratio of octahedral: tetrahedral alumin ium sites in the aluminas is not an important parameter. Solvolysis re actions of 1 led to the formation of the surface multigrafted species (AlO)(x+z)SnBu(3-z) (x = 1, 2; z = 1, 2, 3), while beta-H elimination of but-1-ene followed by reductive elimination led to inorganic tin(II ) compounds on the surface of the alumina. These transformations occur at temperatures lower than those observed with =SiOSnBu(3) grafted on the surface of silica. This is possibly related to the more acidic pr operties of alumina or to the higher concentration and/or mobility of Al hydroxy groups with respect to Si hydroxy groups.