Stabilization of MIV = Ti, Zr, Hf, Ce, and Th using a selenium bis(phenolate) ligand

We report M(iv) M = Ti, Zr, Hf, Ce, and Th, complexes of a selenium bis(phenolate) ligand, 2,2'-selenobis(4,6-di-tert-butylphenol), (H(2)(Ar)OSeO), 1. Reaction of Ti(NEt(2))(4) with two equivalents of affords Ti((Ar)OSeO)(2), 2. Salt metathesis of ZrCl(4) and HfCl(4) with two equivalents of Na(2)(Ar)OSeO produces Zr((Ar)OSeO)(2)(THF), 3, and Hf((Ar)OSeO)(2)(THF), 4, respectively. Protonolysis of ThCl[N(SiMe(3))(2)](3) with two equivalents of yields Th((Ar)OSeO)(2)(THF)(2), 5. Salt metathesis of Ce(OTf)(3) and two equivalents of Na(2)(Ar)OSeO produces [Na(THF)(3)][Ce((Ar)OSeO)(2)], which was oxidized in situ using 0.5 equivalents of I(2) to yield the diamagnetic Ce(iv) product, Ce((Ar)OSeO)(2)(THF)(2), 6. Addition of 2,2'-bipyridyl to forms Ce((Ar)OSeO)(2)(bipy), 6a. Each diamagnetic complex was characterized using (1)H, (13)C, and (77)Se NMR and IR spectroscopy and the structures of 2-6a were established with X-ray crystallography. Electrochemical measurements using cyclic voltammetry on complexes 2, 5, and 6a re also reported.