Designing Stability into Thermally Reactive Plumbylenes

We complete the picture of thermally stable and volatile N-heterocyclic metallylenes with the synthesis, structural analysis, and thermal characterization of rac-N2,N3-di-tert-butylbutane-2,3-diamido lead(II) (1Pb). Transamination of bis[bis(trimethylsilyl)amido] lead(II) with the free diamino ligand yields 1Pb in high yield, whereas salt-metathesis leads to oxidative cleavage of the butane backbone and production of acetaldehyde-tert-butylimine. 1Pb itself undergoes [2+2+1] cycloreversion at 150 °C to the same imine, but with a vapour pressure of 1 Torr at 94 °C a wide thermal window is available for use as a vapour deposition precursor.

We contrast this with the the extreme instability of its sisters N2,N3-di-tert-butylethane-2,3-diamido lead(II) (2Pb) and N2,N3-di-tert-butylethylene-2,3-diamido lead(II) (3Pb), which both reductively eliminate Pb(0) at or below room temperature. This is also in start contrast to the stability of the lighter Si, Ge and Sn congeners.