Reaction of a Germylene, Stannylene, or Plumbylene with Trimethylaluminum and Trimethylgallium: Insertion into Al–C or Ga–C Bonds, a Reversible Metal–Carbon Insertion Equilibrium, and a New Route to Diplumbenes

The
reaction of the tetrylenes Ge­(ArMe6)2, Sn­(ArMe6)2, and Pb­(ArMe6)2 [ArMe6 = C6H3-2,6-(C6H2-2,4,6-(CH3)3)2] with the group
13 metal alkyls trimethylaluminum and trimethylgallium afforded (ArMe6)2Ge­(Me)­AlMe2 (1), (ArMe6)2Ge­(Me)­GaMe2 (2), and (ArMe6)2Sn­(Me)­GaMe2 (3) in good
yields via insertion reaction routes. In contrast, the reaction of
AlMe3 with Sn­(ArMe6)2 afforded the [1.1.1]­propellane analogue Sn2{Sn­(Me)­ArMe6}3 (5) in
low yield, and the reaction of AlMe3 or GaMe3 with Pb­(ArMe6)2 resulted
in the formation of the diplumbene {Pb­(Me)­ArMe6}2 (6) and AlArMe6Me2 (7) or GaArMe6Me2 (8) via metathesis.
The reaction of Sn­(ArMe6)2 with gallium trialkyls was found to be reversible under ambient
conditions and analyzed through the reaction of Sn­(ArMe6)2 with GaEt3 to form (ArMe6)2Sn­(Et)­GaEt2 (4), which displayed a dissociation constant Kdiss and ΔGdiss of 8.09(6) × 10–3 and 11.8(9) kJ mol–1 at 296 °C. The new compounds were characterized
by X-ray crystallography, NMR (1H, 13C, 119Sn, and 207Pb), IR, and UV–vis spectroscopies.