Bicyclic Guanidinates in Mono- and Di-Valent Metal Complexes, Including Group 1/2 and Group 1/12 Heterometallic Systems

Abstract

Complexes containing mono-, di-, and mixed mono-/di-valent metal centres supported by the [hpp]– anion (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine) are reported. Amine elimination from Mn(N{SiMe3}2)2 using the neutral guanidine is a clean route to the heteroleptic compound [Mn(hpp)(N{SiMe3}2)]2. Addition of 18-crown-6 to a solution of the hpp– potassium salt (hppK) enables the first potassium derivative of [hpp]– to be structurally analysed, showing that the crown ether restricts aggregation to afford a monometallic structure. Mixed lithium–magnesium and lithium–zinc compounds of general formula Li2M2(hpp)6 (M = Mg, Zn) have been characterised crystallographically showing the guanidinate anions to be present in two different coordination modes, bridging two- or four-metal centres. Spectroscopic measurements suggest a robust framework that is maintained in solution.