Lignin is a unique potential source of aromatic chemicals derived from renewable resources.Homogeneous oxovanadium, copper and cobalt complexes exhibit intriguing selectivity for the aerobic oxidation of complex lignin models, affording some control of C-C, C-H and C-O bond cleavage. In this work these catalysts are compared, along with a metal-free variant, for their performance in oxidation and depolymerisation of organosolv lignin, as determined by gel permeation chromatography (GPC), quantitative-heteronuclear single quantum correlation (q-HSQC) and 31 P NMR spectroscopy of derived phosphite esters. Although most catalysts oxidized the lignin extracts, the oxovanadium(V) complexes, [VO(O i Pr)L n ] (L n ¼ dipic or (HQ) 2 where dipic ¼ dipicolinate and HQ ¼ 8-oxyquinoline) demonstrated the highest degree of lignin depolymerisation. Further ligand development is achieved with a tethered base (pyridine) in the novel BPAMP(V V )(O)(O i Pr) catalyst [H 2 PAMP ¼ N,N-bis(3,5-di-tertbutyl-2-phenol)-N-(methylpyridine)amine]. Efficient oxidation and some degree of depolymerisation is achieved with this new bifunctional catalyst without the addition of exogenous base.

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