The synthesis and structural characterization of a series of pentacoordinate diorganotin(IV) N-arylidene-α-amino acid complexes

Eight new diorganotin complexes formulated as R2Sn(OArCR″=NCHR′COO) were prepared and characterized by 1H and 13 C NMR, IR, and elemental analysis. A single crystal X-ray diffraction study of the dibutyltin N-salicylidenevaline complex, Bu2Sn(OC6H4CH=NCH(i-Pr)COO), determines the molecular structure. The crystals are orthorhombic, space group P212121 with a = 9.187(2) A, b = 10.003(2) A, c = 23.482(4) A, V = 2157.8(6) A3, Z = 4, and Dc = 1.392 g cm−3. The final discrepancy factors are RF = 0.040, and Rw = 0.021 for 1131 significant reflections. The tin atom has a distorted trigonal bipyramidal coordination, with no short intermolecular contacts. The two axial Sn—O bonds of 2.078(10) and 2.151(8) A and the equatorial Sn—N bond of 2.158(8) A are among the shortest found in related complexes. The fact that the closest intermolecular Sn—O distance is 4.511(8) A indicates a nonbridging carbonyl group.