Abstract
The insertion reaction between 1 equiv. of carbodiimide, R′N=C=NR′, and the zinc bis(amide) [Zn{N(SiMe~3~)~2~}~2~] affords the homoleptic zinc(II) guanidinate compounds [Zn{(Me~3~Si)~2~NC(NR′)~2~}~2~] (3, R′ = i__Pr; 4, R′ = Cy) in preference to the monosubstituted compounds. Compound 3 also results from the protonation reaction of 1 equiv. of the neutral guanidine (Me~3~Si)~2~NC(N__i__Pr)(NH__i__Pr) (2) with [Zn{N(SiMe~3~)~2~}~2~] or ZnMe~2~. In contrast, the N‐dimethylguanidine analogue Me~2~NC(N__i__Pr)(NH__i__Pr) (1) reacts cleanly with 1 equiv. of ZnMe~2~ to afford the dimeric species [Zn{Me~2~NC(N__i__Pr)~2~}Me]~2~ (5). Attempted protonation of the Zn−C bond in 5 with 2,6‐di‐tert‐butylphenol resulted in preferential reaction at the Zn−N bond and formation of the mixed (aryloxo)methyl complex [Zn(OAr)Me·{Me~2~NC(N__i__Pr)(NH__i__Pr)}] (6), isolated as the guanidine adduct. Heating of 6, in an attempt to promote methane elimination, afforded a small amount of the dimetallic complex [{Zn(OAr)}~2~(μ‐{Me~2~NC(N__i__Pr)~2~})(μ‐NMe~2~)] (7) as a result of the extrusion of NMe~2~^−^ from the guanidine‐based ligand. The amine‐elimination reaction between [Zn{N(SiMe~3~)~2~}~2~] and 1 equiv. of 1,3,4,6,7,8‐hexahydro‐2__H‐pyrimido[1,2‐a]pyrimidine (hppH) proceeds smoothly to afford the mixed (guanidinate)(amide) complex [Zn(hpp){N(SiMe~3~)~2~}]~2~ (8), which forms a dimer in the solid state. Crystal structures of compounds 3−8 are reported and a preliminary study of the activity of 8 in the ring‐opening polymerisation of lactide is described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004