A new bonding mode for the bicyclic guanidinate, [hpp]−, in the tetrametallic yttrium oxide cluster, Y4(hpp)8Cl2(μ4-O)

Oxygen incorporation in the product of the reaction between YCl3 and the lithium salt of 1,3,4,6,7,8-hexahydro-2Hpyrimido[1,2-a]pyrimidine (hppH) afforded the tetrametallic cluster Y4(hpp)8Cl2(μ4-O), in which four of the guanidinate anions are involved in a previously unreported μ,η2,η2-bridging mode between two metal centres.