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

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 [Ru(II)(Pc)(HN=CPh2)2] (1 a) and [Ru(II) (Pc)(HNQu)2 ] (1b; HNQu=N-phenyl-1,4-benzoquinonediimine) with PhI(OAc)2 affords bis(ketimido) ruthenium(IV) phthalocyanines [Ru(IV)(Pc)(N=CPh2)2] (2a) and [Ru(IV)(Pc)(NQu)2] (2b), respectively. X-ray crystal structures of 1b and [Ru(II) (Pc)(PhN=CHPh)2] (1c) show Ru-N(ketimine) distances of 2.075(4) and 2.115(3) Å, respectively. Complexes 2a,b readily revert to 1a,b upon treatment with phenols. (1)H NMR spectroscopy reveals that 2a,b are diamagnetic and 2b exists as two isomers, consistent with a proposed eclipsed orientation of the ketimido ligands in these ruthenium(IV) complexes. The reaction of 1a,b with PhI(OAc)2 to afford 2a,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 1b and 2b, which provide support for the diamagnetic nature of 2b and reveal a significant barrier for rotation of the ketimido group about the Ru-N(ketimido) bond.