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), (H2ArOSeO), 1. Reaction of Ti(NEt2)4 with two equivalents of 1 affords Ti(ArOSeO)2, 2. Salt metathesis of ZrCl4 and HfCl4 with two equivalents of Na2ArOSeO produces Zr(ArOSeO)2(THF), 3, and Hf(ArOSeO)2(THF), 4, respectively. Protonolysis of ThCl[N(SiMe3)2]3 with two equivalents of 1 yields Th(ArOSeO)2(THF)2, 5. Salt metathesis of Ce(OTf)3 and two equivalents of Na2ArOSeO produces [Na(THF)3][Ce(ArOSeO)2], which was oxidized in situ using 0.5 equivalents of I2 to yield the diamagnetic Ce(IV) product, Ce(ArOSeO)2(THF)2, 6. Addition of 2,2′-bipyridyl to 6 forms Ce(ArOSeO)2(bipy), 6a. Each diamagnetic complex was characterized using 1H, 13C, and 77Se 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 6 are also reported.