Delocalisation guanidine

While stabilisation by delocalisation in the cation (12) would not be expected to be as effective as that in the guanidine cation (10) above, ethanamidine, CH3C(=NH)NH2 (pKa = 12-4), is found to be a much stronger base than ethylamine, MeCH2NH2 (pKa = 10-67). 

On protonation of guanidine, the (H2N)2C=NH+ cation is stabilised by extensive delocalisation of the charge by the electron-donating NH2 (+M) groups (see below). 

All of the guanidinate and p-diketiminate compounds exhibit significant delocalisation over their ligand backbones, though there is considerable variation in the relative orientation of the two Mg heterocycles within the series. This is most probably due to a low barrier to rotation around the Mg-Mg bonds, and probably reflects the sterics of the ligand involved and/or crystal packing forces. The two Mg... 

---