Ketimido metallophthalocyanines : an approach to phthalocyanine-supported mononuclear high-valent ruthenium complexes

摘要

A "metal-ketimine+ArI(OR)2" approach has been developed for preparing metal-ketimido complexes, and ketimido ligands are found to stabilize high-valent metallophthalocyanine (M-Pc) complexes such as ruthenium(IV) phthalocyanines. Treatment of bis(ketimine) ruthenium(II) phthalocyanines [RuII(Pc)(HN=CPh2)2] (1 a) and [RuII(Pc)(HNQu)2] (1 b; HNQu=N-phenyl-1,4- benzoquinonediimine) with PhI(OAc)2 affords bis(ketimido) ruthenium(IV) phthalocyanines [RuIV(Pc)(N=CPh2) 2] (2 a) and [RuIV(Pc)(NQu)2] (2 b), respectively. X-ray crystal structures of 1 b and [RuII(Pc)(PhN=CHPh) 2] (1 c) show Ru-N(ketimine) distances of 2.075(4) and 2.115(3) Å, respectively. Complexes 2 a,b readily revert to 1 a,b upon treatment with phenols. 1H NMR spectroscopy reveals that 2 a,b are diamagnetic and 2 b exists as two isomers, consistent with a proposed eclipsed orientation of the ketimido ligands in these ruthenium(IV) complexes. The reaction of 1 a,b with PhI(OAc)2 to afford 2 a,b suggests the utility of ArI(OR) 2 as an oxidative deprotonation agent for the generation of high-valent metal complexes featuring M-N bonds with multiple bonding characters. DFT and time-dependent (TD)-DFT calculations have been performed on the electronic structures and the UV/Vis absorption spectra of 1 b and 2 b, which provide support for the diamagnetic nature of 2 b and reveal a significant barrier for rotation of the ketimido group about the Ru-N(ketimido) bond.