Subvalent Group 4B metal alkyls and amides. Part 4. An electron spin resonance study of some long-lived photochemically synthesised trisubstituted silyl, germyl, and stannyl radicals

Abstract
A number of solution-stable species of general formula MR3˙[R = CH(SiMe3)2: M = Si. Ge. or Sn], M(NR′2)3˙ and M (NR′R″)3˙(R′= SiMe3, R″= CMe3, M = Ge or Sn) have been prepared and characterised by e.s.r. spectroscopy. Most of the radicals have been generated by photolysis of the bivalent Group 4 species MR, M(NR′2)2 or M(NR′R″)2 when available; others have been obtained by alternative photochemical experiments. The e.s.r. parameters indicate that the radicals have non-planar structures similar to those of analogous transient species such as MMe3˙. The mechanism of formation of the radicals is discussed : their unusual stability (e.g. SnR3˙ has a halflife of ca. 1 year at 20 °C) is attributed mainly to steric hindrance to dimerisation.

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