Mononuclear osmium(II) complexes bearing (S,S)-iPr-pybox and (R,R)-Ph-pybox ligands

The complexes trans-[OsCl2(L){(S,S)-iPr-pybox}] ((S,S)-iPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine; L = CNBn (3), CNCy (4) and MeCN (7)) and trans-[OsCl2(L){(R,R)-Ph-pybox}] ((R,R)-Ph-pybox = 2,6-bis[4′-(R)-phenyloxazolin-2′-yl]pyridine, L = CNBn (5), CNCy (6) and MeCN (8)) have been stereoselectively synthesized from the complexes trans-[OsCl2(η2-C2H4)(R-pybox)] (R = (S,S)-iPr (1), (R,R)-Ph (2)), via substitution of ethylene, under reflux or microwave irradiation conditions. The complex trans-[OsCl2(η2-MeO2CCCCO2Me){(S,S)-iPr-pybox}] (9) has been analogous prepared from complex 1. The activation of terminal alkynes and alkynols by olefin complex 1, under toluene reflux conditions, has been achieved to give vinylidene trans-[OsCl2{CC(H)Ph}{(S,S)-iPr-pybox}] (10), allenylidene trans-[OsCl2(CCC(R)Ph){(S,S)-iPr-pybox}] (R = Ph (11), H (12)) and cyclic carbene complexes trans-[OsCl2(){(S,S)-iPr-pybox}] (13).

Graphical abstractEthylene-isocyanide, -acetonitrile and –DMAD exchange reactions are reported for the complexes trans-[OsCl2(η2-C2H4)(R-pybox)] (1, 2). Moreover, the reaction of 1 with alkynes and alkynols involves the C–H activation allowing for the formation of osmium vinylidene (10), allenylidene (11, 12) and oxacyclic carbene (13) complexes.Figure optionsDownload full-size imageDownload as PowerPoint slide