Effects of solvent on the relative stability of mono and di-aluminium aryloxide complexes of bipyridines:anomalous behavior of[(~tBu)_2Al(OPh)]_2(mu-4,4-bipy)

摘要

We have recently reported the synthesis and characterization of bridged dialuminium compounds,[R_(3-n)Al(OPh)_n]_2(u-L),formed from the reaction of [(~tBu)_2Al(mu-OPh)]_2 with 4,4'-bipyridine(bipy),1,2-bis(4-pyridyl)ethane(bipetha),and trans-l,2-bis(4-pyridyl)ethylene(bipethe).The solution ~1H and ~(13)C NMR spectra show multiple sets of resonances associated with the 2:1 complexes(la-3a)and the 1:1 complexes(lb-3b).In addition,the spectra for the bipy derivative in CDC1,shows signals due to the free ligand and [(~tBu)2Al(mu-OPh)]_2.The presence of these species is consistent with two equilibria(eqn.(1)and(2)).