Tin(IV) porphyrin complexes. Crystal structures of meso-tetraphenylporphyrinatotin(IV) diacetate, bis(dichloroacetate), bis(trifluoroacetate) and diformate, and structural correlations for tin(IV) porphyrin complexes with O-bound anionic ligands
J.C. Mcmurtrie, D.P. Arnold
Keywords: tin porphyrins, X-ray crystallography, carboxylato complexes, structure correlations
Pages: 113-119
Abstract
Structures of four tetraphenylporphyrinatotin(IV) bis(carboxylato) complexes [Sn(tpp)(OCOR)2] have been determined by single crystal X-ray diffraction. All complexes have typical octahedral geometry. The average Sn-N bond lengths for R = CH3, CHCl2, CF3 and H are 2.091, 2.084, 2.082 and 2.086 Å, respectively. The Sn-O bond lengths are 2.096, 2.091, 2.109 and 2.090 Å respectively. These bond lengths and those of all other reported Sn(tpp) complexes of O-bound anionic ligands are compared. There is an inverse correlation between the Sn-N and Sn-O bond lengths, indicating that stronger electron donation by the axial anionic ligand results in an expansion of the porphyrin core. Correlation of the Sn-O bond lengths with the pKa of the conjugate acids of the axial ligands shows that the stronger the acid, the longer the Sn-O bonds, indicating that the bonding is dominated by electrostatic effects.
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