Synthesis of Square‐Planar Aluminum(III) Complexes

The synthesis of two four‐coordinate and square planar (SP) complexes of aluminum(III) is presented. Reaction of a phenyl‐substituted bis(imino)pyridine ligand that is reduced by two electrons, Na 2 ( Ph I 2 P 2− ), with AlCl 3 afforded five‐coordinate [( Ph I 2 P 2− )Al(THF)Cl] ( 1 ). Square‐planar [( Ph I 2 P 2− )AlCl] ( 2 ) was obtained by performing the same reaction in diethyl ether followed by lyphilization of 2 from benzene. The four‐coordinate geometry index for 2 , τ 4 , is 0.22, where 0 would be a perfectly square‐planar molecule. The analogous aluminum hydride complex, [( Ph I 2 P 2− )AlH] ( 3 ), is also square‐planar, and was characterized crystallographically and has τ 4 =0.13. Both 2 and 3 are Lewis acidic and bind 2,6‐lutidine.