A new class of linked-bis(N,N′-dialkylamidinate) ligand: applications in the synthesis of bimetallic aluminium complexes

The 1,4-benzenebis(N,N′-dialkylamidine) compounds, 1,4-C6H4[C{NR}{NHR}]2 (1, R=Cy; 2, R=iPr) were synthesised via addition of a stoichiometric amount of water to the 1,4-benzenebis(amidinate) species, generated from the in situ reaction between 1,4-Li2C6H4 and the appropriate carbodiimide. Alternatively, the neutral silylated derivatives, 1,4-C6H4[C{NR}{N(SiMe3)R}]2 (3, R=Cy; 4, R=iPr) are synthesised by quenching the 1,4-benzenebis(amidinate) with excess Me3SiCl. Structural characterisation of selected examples are reported, showing that the neutral NH compounds are monomeric with a E-syn:E-syn arrangement of the N-alkyl substituents, while in the silylated derivative 4, the E-anti:E-anti form is present in the solid-state. Synthesis of the bimetallic aluminium compounds 1,4-C6H4[C{NiPr}2AlMeX]2 (5, X=Cl; 6, X=Me) was achieved from AlMe2Cl using 2 by either the direct protonolysis of an AlC bond (5), or the trans-metallation reaction of the in situ generated dilithio-salt (6). Structural characterisation of 6 revealed a monomeric complex with a perpendicular arrangement of the amidinate units with respect to the C6-group.