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

Abstract

The 1,4-benzenebis( N,N′-dialkylamidine) compounds, 1,4-C 6H 4[C{NR}{NHR}] 2 ( 1, R=Cy; 2, R= i Pr) 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-Li 2C 6H 4 and the appropriate carbodiimide. Alternatively, the neutral silylated derivatives, 1,4-C 6H 4[C{NR}{N(SiMe 3)R}] 2 ( 3, R=Cy; 4, R= i Pr) are synthesised by quenching the 1,4-benzenebis(amidinate) with excess Me 3SiCl. Structural characterisation of selected examples are reported, showing that the neutral N H 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-C 6H 4[C{N i Pr} 2AlMeX] 2 ( 5, X=Cl; 6, X=Me) was achieved from AlMe 2Cl 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 C 6-group.