Syntheses and characterization of tin(II) complexes containing 10-pi-electron ring systems

The compounds [(i-Pr)(2)ATI]SnCl (1) and {[(i-Pr)(2)ATI]Sn}[eta(5)-C5H5)ZrCl2(mu-Cl-3)ZrCl2(eta(5)-C5H5)] (2) in which [(i-Pr)(2)ATI] = N-isopropyl-2-(isopropylamino)troponimine have been prepared and characterized by H-1, C-13, and Sn-119 NMR spectroscopies and X-ray crystallography. Compounds 1 and 2 feature heterobicyclic C7N2Sn ring systems with basically three- and two-coordinate tin atoms, respectively. Solid state structures of 1 and 2 show weak Sn...Cl interactions. The Sn-119 NMR signal of 2 appears at a significantly lower field compared to that of 1. This is consistent with the reduction in coordination number at the Sn center of 2. The H-1 NMR data also provide evidence for the formation of a more symmetric solution species with the removal of Cl- from 1. X-ray structural features of C7N2Sn moiety in [(i-Pr)(2)ATI]SnCl and the {[(i-Pr)(2)ATI]Sn}(+) cation are very similar. The Sn-N bond distances of {[(i-Pr)(2)ATI]Sn}(+) cation are not indicative of any significant Sn-N multiple bonding. The pi-electrons of the C7N2Sn ring system, therefore, appears to be mostly delocalized over nitrogen and carbon atoms.