The following equilibrium has been studied by ¹¹⁹Sn NMR and Mossbauer spectroscopies:

The ¹¹⁹Sn Mossbauer spectrum of a solid sample of RSnSnRPh₂ at 78K provided evidence for the presence of three different tin environments. When RSnSnRPh₂ dissolves in toluene, a red solution is obtained, and at room temperature, the ¹¹⁹Sn NMR spectrum of this solution shows one broad signal at δ 1517 ppm. This chemical shift is similar to that observed for Sn(C₆H-2-^tBu-4,5,6-Me₃)₂. On cooling the solution to 233K, the signal at δ 1517 ppm gradually sharpens and at the same time, two new signals appear at δ 246 and 2857 ppm. Each of these new signals shows coupling J

Cooling further to 213K results in the disappearance of the signal at δ1517 ppm, and at this point, the solution is green in colour. A colour change from green to red is observed when the solution is warmed up to room temperature. Rationalize these observations.

Transcribed Image Text:

Sn 1 R R Si -Sn, 'Ph Ph 2RPhSn R=C6H3-2,6-(C6H₂-2,4,6-¹Pr3)2