Dinuclear Manganese(II), Cobalt(II), and Nickel(II) Aryl Phosphates Incorporating 4′‐Chloro‐2,2′:6′,2′′‐Terpyridine Coligands – Efficient Catalysts for Alcohol Oxidation

Abstract

The dinuclear cyclo(metallo)phosphates [M(dipp)(Cl‐terpy)]2 [M = Mn (1), Ni (2)] and the mononuclear cobalt phosphate [Co(dippH)(Cl‐terpy)(MeOH)(H2O)]·dippH (3) were synthesized through the reactions of 4′‐chloro‐2,2′:6′,2′′‐terpyridine (Cl‐terpy) and 2,6‐diisopropylphenyl phosphate (dippH2) with manganese, nickel, and cobalt acetates. The formation of 1–3 is supported by spectroscopic, thermogravimetric, and microanalytical data. The molecular structures of 1 and 3 were confirmed by single‐crystal X‐ray diffraction studies. Compounds 1 and 2 are dimeric and feature two octahedral metal centers bridged by dianionic dipp ligands. On the other hand, 3 exists as a monomer in the solid state, but dissolution in methanol converts it to a dimeric form similar to those of 1 and 2, as evidenced by ESI‐MS studies. Compounds 1–3 were employed as catalysts for alcohol oxidation reactions with tert‐butyl hydroperoxide (TBHP) as the oxidant. The manganese phosphate 1 exhibits better catalytic activity in terms of selectivity and substrate conversion compared with those of 2 and 3 under similar conditions.