Abstract
The reduction of the boryl-substituted Sn(II) bromide {(HCDippN)(2) B}Sn(IPrMe)Br with 1.5 equivalents of potassium graphite leads to the generation of the cyclic tetratin tetraboryl system K(2) [Sn(4) {B(NDippCH)(2) }(4) ], a homo-metallic heavier analogue of the cyclobutadiene dianion. This system is non-aromatic as determined by Nucleus Independent Chemical Shift Calculations (NICS(0)=-0.28, NICS(1)=-3.17), with the primary contributing resonance structures shown by Natural Resonance Theory (NRT) to involve a Sn=Sn double bond and 1,2-localized negative charges. Abstraction of the K(+) cations or oxidation leads to contraction or cleavage of the Sn(4) unit, respectively, while protonation generates the neutral dihydride 1,2-Sn(4) {B(NDippCH)(2) }(4) H(2) (a heavier homologue of cyclobutene) in a manner consistent with the predicted charge distribution in the [Sn(4) {B(NDippCH)(2) }(4) ](2-) dianion.