Bis axial ligation of simple imine and methyleneamido groups by ruthenium porphyrins

Abstract

Bis(N-ethylideneethanamine)-ruthenium(II) porphyrins, [RuII(Por)-(N(Et)=CHMe)2] (Por=TTP, 4-Cl-TPP), were prepared by the reaction of dioxoruthenium(VI) porphyrins with triethylamine in ≈85% yields. The reaction between dioxoruthenium(VI) porphyrins and benzophenone imine afforded bis-(diphenylmethyleneamido)ruthenium(IV) porphyrins, [RuIV(Por)(N=CPh2)2] (Por= TTP, 3,4,5-MeO-TPP), in ≈65% yields. These new classes of metalloporphyrins were characterized by 1H NMR, UV/ Vis, and IR spectroscopy as well as by mass spectrometry and elemental analysis. The X-ray crystallographic structures of [RuII(TTP)(N(Et)=CHMe)2] and [RuIV(3,4,5-MeO-TPP)(N=CPh2)2] revealed an axial Ru-N bond length of 2.115(6) Å for the imine complex and 1.896(8) Å for the methyleneamido complex. Each of the N=CPh2 axial groups in [RuIV(3,4,5-MeO-TPP)-(N=CPh2)2] adopts a linear coordination mode with a corresponding Ru-N-C angle of 175.9(9)°. Spectral and structural studies revealed essentially single bonding character for the bis(imine) complexes but a multiple bonding character for the bis(methyleneamido) complexes with respect to their axial Ru-N bonds.