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 organometallic fragments [AlO]Sn-x(n-C4H9)(3) (x = 1, 2) 1 grafted on various partially dehydroxylated aluminas (alpha, gamma, eta) has been investigated. The surface reactions were followed by qualitative and quantitative determination of the evolved gases including IR spectroscopy, C-13 cross-polarisation magic angle spinning and Sn-119 magic angle spinning NMR studies. On all aluminas, comparable transformations of 1 were identified showing that the ratio of octahedral: tetrahedral aluminium sites in the aluminas is not an important parameter. Solvolysis reactions 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 properties of alumina or to the higher concentration and/or mobility of Al hydroxy groups with respect to Si hydroxy groups.