Further study of estertin trichlorides, Cl3SnCH2CH2CO2R. Lewis acidity towards acetonitrile. Crystal structure of Cl3SnCH2CH2CO2Pr-i

Abstract Crystals of Cl 3 SnCH 2 CH 2 CO 2 Pri-i are orthorhombic, space group P 2 1 2 1 2 1 with a 9.638(6), b 10.004(7) and c 12.848(8) A. The tin atom is five-coordinate with two chlorines and carbon equatorial and the remaining chlorine and the carbonyl oxygen axial, in a distorted trigonal-bipyramidal arrangement: (SnCl) ax 2.389(3), average (SnCl) eq 2.320(2), SnC 2.142(9), SnO 2.337(5) A. Apart from the equatorial chlorine and the terminal carbons in the isopropyl group, all non-hydrogen atoms are essentially coplanar. The molecule approaches C 2 v symmetry although not constrained to do so by the crystallographic space group. In MeCN solution, the compounds Cl 3 SnCH 2 CH 2 CO 2 R (I, R = Me, Pr-i, C 6 H 4 X (X = p -MeO, H, p -Cl, o -MeO or C 6 H 3 Cl 2 -2,4) form as equilibrium mixtures of 1/1 and 2/1 MeCN/I complexes; the chelate ring is broken in the 2/1 complexes. Equilibrium constants indicate that the strength of the intramolecular SnO coordination in I increases with the electron releasing ability of the R group.