"Coordination Compounds of 2,5-Bis(4'-tert-butylpyridinium-1'-yl)-3,6-dioxy-1,4-benzoquinone"

Coordination complexes which stabilize low oxidation states in metals are of interest for use in homogenous catalysis. The coordination behavior of the zwitterion 2,5-Bis(4'-tert-butylpyridinium-1'-yl)-3,6-dioxy-1,4-benzoquinone (PBQL) with cobalt(II), chromium(III), and ruthenium(III) was explored. Compounds formed include Co(PBQL)2Cl2, Co(PBQL)3Cl2, Cr(PBQL)2Cl3, and Ru(PBQL)3Cl3. Electrochemical studies are presented, as well as UV-Vis, FT-IR, and 1H NMR spectra. Cyclic voltammetry indicates that Co(PBQL)2Cl2 is able to ease reduction in the CoII/I couple, changing the potential from -1.295V to -1.23V. Variable-temperature 1H NMR shows paramagnetic shifting, with especially drastic changes in chemical shift for Co(PBQL)2Cl2. Cr(PBQL)2Cl3 is shown to have multiple reduction potentials, implying the formation of an oligomeric complex having Cr+3 in a variety of environments. Paramagnetic line broadening is observed in Cr(PBQL)2Cl3, but the extreme chemical shifts observed in Co(PBQL)2Cl2 are absent.