Chromium(III) Bis-alkynyl complexes supported by C-substituted cyclam MPC

Abstract

Macrocyclic CrIII bis-alkynyl complexes have recently been used as a precursor in the synthesis of mono-alkynyl complexes, which can serve as synthetic intermediates towards the formation of dissymmetric bis-alkynyl complexes. The trans stereochemistry is essential to generate stable macrocyclic CrIII mono-alkynyl complexes, however, previously explored cyclam (1,4,8,11-tetraazacyclotetradecane) and its derivatives heavily favor the cis isomer after Cr insertion. The C-substituted cyclam MPC (5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane) has shown a noteworthy preference towards the trans isomer upon insertion of Cr, making it desirable for the pursuit of dissymmetric bis-alkynyl complexes in significant quantity. Reported herein are the synthesis and characterization of trans-[Cr(MPC)(C2Ar)2]+ complexes, where Ar is Ph (1), Np (2), or C6H4tBu (3). Complexes 1 – 3 have structural and optical properties similar to previous CrIII bis-alkynyl complexes based on single-crystal X-ray diffraction, UV-vis and phosphorescence spectroscopical characterizations.