Twenty-four 2,2-di-n-butyl- and 2,2-diphenyl-6-aza-1,3-dioxa-2-stannabenzocyclononen-4-ones, each having a transannular N-->Sn bond, have been prepared by one-step reactions of alpha-amino acids (1 a-l), salicylaldehyde (2), and either di-n-butyltin(IV) oxide (3) or diphenyltin(IV) oxide (4). The new methodology constitutes an easy, highly efficient one-step synthesis of diorganotin(IV) derivatives, such as 5 a-l and 6 a-l, from iminic tridentate ligands without isolation of the Schiff bases. The structures of all the compounds have been established by a combination of (1)H, (13)C, (15)N, and (119)Sn NMR spectroscopy, IR spectroscopy, mass spectrometry, and elemental analysis. In all cases, the (119)Sn chemical shifts, as well as the (1)J((119)Sn,(13)C) coupling constants, are indicative of pentacoordinated tin atoms in solution. The structures of compounds 5 a, d, f, 6 a, b, b-racemic, c, d, f, g, and l have been established by single-crystal X-ray diffraction analyses. The tin atoms in 5 d, f, 6 a, b, b-racemic, c, d, g, and l each have a distorted trigonal-bipyramidal (TBP) geometry, with the oxygen atoms from the phenol and carboxylate moieties occupying the axial positions, and the imine nitrogen and phenyl or n-butyl substituents occupying the equatorial positions. Compounds 5 a and 6 f show distorted octahedral (DOC) geometries due to intermolecular coordination of the carbonyl oxygen to the tin atom, in a trans disposition to the N-->Sn bond, leading to trimeric 5 a and a polymeric structure for compound 6 f. Additionally, measurement of the one-bond coupling constants (1)J((119)Sn,(13)C) in diphenyltin(IV) complexes (6 a-l) and their correlation with the CSn-C bond angles has allowed the derivation of an equation that can be applied to assess the geometry around the tin atom for other diphenyltin(IV) compounds in solution.

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A series of molecules, based on the smallest carbon cluster with one planar tetracoordinate carbon atom, C5(2-), are presented. To gain a better understanding about which electronic factors contribute to their stabilization, several global reactivity indexes, molecular scalar fields, and magnetic responses were calculated. The optimized bond lengths and the topological analysis of the electron density show that the central carbon atom in the parent dianion C5(2-) has a planar local environment, and it is coordinated to four other carbon atoms. The bonding of the parent dianion with the metal cations is highly ionic. The magnetic properties show that the C5(2-) derivatives are strongly diatropic and have a remarkable transferability of structural and electronic features from the anion to the salts. The theoretical analysis suggests that the lithium salt, C5Li2, is the most plausible candidate for experimental detection.