A COMPARATIVE-STUDY OF THERMAL-INDUCED AND RADIATION-INDUCED SINGLE-ELECTRON TRANSFER IN REACTIONS OF 1,4-DIAZA-1,3-BUTADIENES WITH DIALKYLZINC COMPOUNDS
E. Wissing et al., A COMPARATIVE-STUDY OF THERMAL-INDUCED AND RADIATION-INDUCED SINGLE-ELECTRON TRANSFER IN REACTIONS OF 1,4-DIAZA-1,3-BUTADIENES WITH DIALKYLZINC COMPOUNDS, Organometallics, 13(7), 1994, pp. 2609-2615
The reaction of R2Zn with t-BuDAB (t-BuN=CH-CH=N-t-Bu) results in the
quantitative formation of the red 1:1 coordination charge transfer com
plexes R2Zn-t-BuDAB (R = Me (1a), CH2SiMe3 (5a)). Upon heating (T > 35
-degrees-C), both complexes undergo an inner-sphere single electron tr
ansfer (SET) leading to the radical pair [(Rzn-t-BuDAB).(R.)], that co
llapses, depending on R., to several alkylation products, i.e. the N-a
lkylated product MeZn(t-BuN-CH=CH-N(Me)-t-Bu) (1b) and the exocyclic e
namines Rzn(t-BuN=CH-C(=CHR')N-t-Bu) (R = Me (1f), CH2SiMe3 (5f/5g); R
' = H, SiMe3). Alternatively, the alkyl radical R. escapes from the or
ganozinc radical (Rzn-t-BuDAB)., that subsequently dimerizes to the di
nuclear species (Rzn-t-BuDAB)2 (R = Me (1e), CH2SiMe3 (5e)). The charg
e transfer complex Me2-Zn-t-BuDAB was irradiated in order to induce a
SET reaction within the complex. The irradiation reaction resulted in
the formation of the symmetric dinuclear species 1e (30%) and the unsy
mmetric dinuclear species [MeZn{t-Bu(H)NCH(Me)CH(N-t-Bu)-} {-CH(N-t-Bu
)Cme=N-t-Bu)ZnMe] (1h) (70%). Product 1h was independently prepared fr
om MeZn(t-BuN-CH-(Me)-CH=N-t-Bu) (1c). The latter complex is in a taut
omeric equilibrium with its enamine MeZn(t-BuN-CH(Me)=CH-N(H)-t-Bu), t
hat reacts via a condensation reaction with a parent molecule 1c to gi
ve 1h.