Synthesis and X-ray structures of dilithium complexes of the phosphonate anions [PhP(E)(N(t)Bu)(2)](2-) (E = O, S, Se, Te) and dimethylaluminum derivatives of [PhP(E)(N(t)Bu)(NH(t)Bu)](-) (E = S, Se)

The dilithium salts of the phosphonate dianions [PhP(E)(N(t)Bu)(2)](2-) (E = O, S, Se) are generated by the lithiation of [PhP(E)(NH(t)Bu)(2)] with n-butyllithium. The formation of the corresponding telluride (E = Te) is achieved by oxidation of [Li(2)[PhP(N(t)Bu)(2)]] with tellurium. X-ray structural determinations revealed dimeric structures [Li(THF)(2)[PhP(E)(N(t)Bu)(2)]](2) in which the monomeric units are linked by Li-E bonds. In the case of E = Se or Te, but not for E = S, transannular Li-E interactions are also observed, resulting in a six-rung ladder. By contrast, for E = O, this synthetic approach yields the Li(2)O-templated tetramer [(THF)Li(2)[PhP(O)(N(t)Bu)(2)]](4).Li(2)O in THF or the tetramer [(Et(2)O)(0.5)Li(2)[PhP(O)(N(t)Bu)(2)]](4) in diethyl ether. The reaction of trimethylaluminum with PhP(E)(NH(t)Bu)(2) produces the complexes Me(2)Al[PhP(E)(N(t)Bu)(NH(t)Bu)] (E = S, Se), which were shown by X-ray crystallography to be N,E-chelated monomers.