Magnetic resonance spectroscopic studies of a tetraaryl-distannene and -digermene [M2R4] (R = C6HBut-2-Me3-4,5,6 and M = Sn or Ge)†

Tin-119 NMR spectral studies in the solid state and in solution of [Sn2R4] (R = C6HBut-2-Me3-4,5,6) 3 are presented. The ambient temperature 119Sn CP-MAS NMR spectrum displayed a single resonance at δiso 819, while variable-temperature spectra in toluene clearly indicated the existence of a rapid equilibrium between the loosely held dimer 3 and its monomer SnR2. Photolysis of either 3 or its digermanium analogue in benzene yielded the persistent radicals [MR3]˙ (M = Ge or Sn), which were studied by ESR spectroscopy. The ESR parameters are compared with other trialkyl- and triamido-tin(III)- and -germanium(III)-centred radicals. Noteworthy is the first observation of 13C hyperfine coupling for a Group 14 metal-centred radical, 18(1) G for [SnR3]˙ and 10(1) G for [GeR3]˙.