Coordination behavior of omega-(trichlorostannyl)alkyl acetates, CH3COO(CH2)(n)SnCl3 (n=3-5): A solution and solid-state multinuclear NMR and AM1 quantum-chemical study

The coordination behavior of three ester-functionalized monoorganotin trichlorides of the type omega-(trichlorostannyl)alkyl acetate, CH3COO(CH2)(n)SnCl3 (n = 3-5), has been investigated by multinuclear solid- and solution-state NMR, as well as AM1 quantum-chemical calculations. The data reveal basically the existence of a fast equilibrium between two species involved respectively in an intramolecular and intermolecular donor-acceptor interaction between the ester function and the tin atom. In the n = 3 case, the species involving the intramolecular interaction is by far the dominant one, with a coordination from the alkoxy oxygen atom to the tin atom, resulting in an interaction of the type -CH2O(Ac)-->SnCl3 (Ac = CH3CO-). In contrast, for the n = 4 and 5 cases, the species involving the intermolecular interaction prevails, resulting in (cyclo)dimeric or oligomeric species displaying coordinations from the carbonyl oxygen atom to the tin atom of the type -CH2OC(CH3)=O-->SnCl3.