Metal Complexes Bearing Dianionic Trityl/Aryloxide Ligands: Rational Synthesis, Structural Diversity and Redox Property

Lithium complexes containing bidentate dianionic trityl/aryloxide ligands, Li-2[(R) OC](Et2O)(n) ([(R) OC](2-) = [kappa(2)-O,C-OC6H2-2-C(3,5-R2C6H3)(2)-4,6-tBu(2)](2-); 2a (R = H, n = 1) and 2b (R = Me, n = 0)) were synthesized through double metalation of ortho-benzhydryl phenols with nBuLi. Similarly, sodium compound Na-2[(OC)-O-H](THF)(2.5) (3a) was obtained when phenol H-2[(OC)-O-H] (1a) was treated with two equiv. of nBuLi/NaOtBu. The lithium compounds were employed for the preparation of other metal complexes supported by [(R) OC](2-) ligands, i.e. {Zn[(R) OC](THF)}(2) (R = H (4a) or Me (4b)), Sn[(OC)-O-H](2) (5a) and Cp*Ir[(OC)-O-Me] (6b, Cp* = eta(5)-C5Me5), by salt metathesis reactions with metal halides. The solid-state structures of all metal complexes were established by X-ray crystallography. The nuclearity of these metal complexes and the coordination fashion of the [(R) OC](2-) ligands were found to be highly dependent on the identity of metal centers. Additionally, compound 2a was found to be facilely oxidized, as revealed by both electrochemical and reactivity study.