Preparation of RSn(I)-Sn(I)R with Two Unsymmetrically Coordinated Sn(I) Atoms and Subsequent Gentle Activation of P4

This article reports the reduction of [{2,6-iPr(2)C(6)H(3)NC(CH3)}(2)C6H3SnCl] (1) with potassium graphite to afford a new distannyne [{2,6-iPr(2)C(6)H(3)NC(CH3)}(2)C6H3Sn](2) (2) with a Sn-Sn bond. The most striking phenomenon of 2 is the presence of two differently coordinated Sn atoms (one is three-coordinated, the other is four-coordinated). The Sn-Sn bond length in 2 is 248981(9) angstrom, which is very dose to that of a Sn-Sn single bond (2.97-3.06 angstrom). To elucidate the nature of the Sn-Sn bond, DFT calculation is carried out that shows there is no multiple bond Character in 2. Furthermore, the reaction of 2 with white P-4 affords the tetraphosphabicylobutane derivative 3. This is the first example of gentle activation of white phosphorus by a compound with low Valent Sn atoms. Note that, unlike 2, in 3 both Sn atoms are four-coordinated.