Models for the reactive states of homocuprates: syntheses, structures and reactivities of [Cu(2)Li(2)Mes(4)] and Cu(3)LiMes(4)]

The synthesis and characterisation of two novel tetranuclear and thermally-stable lithium arylcuprates, [Cu(2)Li(2)Mes(4)] and [Cu(3)LiMes(4)], are reported and [Cu(3)LiMes(4)] is shown to be a highly active promoter for the 1,4-addition of organolithiums to enones.