Intramolecular hydrogen bonding in complexes containing bicyclic guanidine ligands

A series of complexes with the general formula MX2(hppH)2 [hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine: 1, M = Mn, X = Cl; 2, M = Fe, X = Cl; 3, M = Ni, X = Cl; 4 M = Zn, X = Br] have been synthesized and structurally characterized. In all cases, the neutral guanidine ligand bonds through the imine nitrogen atom to a tetrahedral metal centre, with additional interaction between the secondary amino NH and the metal bound halide. The intramolecular hydrogen bonding gives two isomeric forms in the solid-state, referred to as Δ and Λ, which co-crystallize in the unit cell. An example of intramolecular hydrogen bonding from the neutral hppH to oxygen within the dimeric core lithiated siloxide, [Ph3SiOLi(hppH)(THF)]2 (5), is also reported.

A series of complexes with formula MX2(hppH)2 [hppH 1,3,4,6,7,8-hexahydro-2Hpyrimido[1,2-a]pyrimidine have been structurally characterized revealing a tetrahedral metal centre, with intramolecular hydrogen bonding to the halide; the lithiated siloxide, [Ph3SiOLi(hppH)(THF)]2 is dimeric with intramolecular NH⋯O interactions.Figure optionsDownload as PowerPoint slide