Optically active bis(β-diketonate) complexes of titanium.

The 2,2'-bis(methylene)biphenyl bridged bis(diketonate) (Tol(2)Bob)Ti(IV) fragment is resolved by reaction of the isopropoxide complex with (R)-1,1'-bi-2-naphthol, which selectively forms (S,Δ)-(Tol(2)Bob)Ti(R-BINOL). The binaphtholate ligand can be cleaved from titanium by careful treatment with trifluoromethanesulfonic acid to give (S,Δ)-(Tol(2)Bob)Ti(OTf)(2), which has a half-life toward racemization of at least 34 h at 51 °C. Racemization of the (Tol(2)Bob)Ti(IV) fragment is strongly accelerated under protic conditions, probably due to protonolysis of one of the diketonate ligands.

Tetradentate bis(hydroxamate) and hydroxamate-diketonate ligands and their titanium(IV) complexes.

A 2,2'-bis(methylene)biphenyl-bridged bis(hydroxamic acid) (HoxH(2)) is prepared by reaction of 2,2'-biphenyldiacetyl chloride with 2 equiv of N-methylhydroxylamine. Use of 1 equiv of CH(3)NHOH gives the cyclic diacylhydroxylamine, which is selectively ring-opened to give a mixed monohydroxamate-monodiketonate ligand HobH(2). Both ligands are metalated by Ti(O(i)Pr)(4) to give the corresponding LTi(O(i)Pr)(2) complexes as exclusively the cis-alpha, (R)-Lambda/(S)-Delta isomers, similar to the previously prepared bis(diketonate) analogues (Bob)TiX(2).