Inactive ruthenium(II)-xantphos complexes from attempted catalyzed lignin reactions

Tests on the use of Ru(H)2(CO)(PPh3)(xantphos) (1) as a hydrogenolysis catalyst for a lignin model compound in bromobenzene at 135 °C under Ar lead to formation of the corresponding, catalytically inactive, but fully characterized complexes, Ru(H)Br(CO)(xantphos) (2) and RuBr2(CO)(xantphos) (3). In 1, the xantphos [xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene] is bidentate with cis-coordinated P-atoms, whereas in 2 and 3 the xantphos is mer-P,O,P-coordinated with the P-atoms trans.