Therrien, Bruno

2012, Ardizzoia, G. Attilio, Brenna, Stefano, Durini, Sara, Therrien, Bruno

A phosphino-oxazine based ligand (L; 2-(2-(diphenylphosphino)phenyl)-2,4-dihydro-1H-benzo[d][1,3]oxazine) showing a temp.-dependent equil. between a closed bidentate (LPN) and an opened tridentate (LPNO) form, has been synthesized and its coordination behavior toward ruthenium(II) centers studied. Under different exptl. conditions, two different species bearing the ligand in either its bidentate or tridentate coordination mode were isolated by reaction with Ru(PPh3)3Cl2. These species, resp. formulated as [Ru(PPh3)(LPNO)Cl2] (1) and [Ru(PPh3)(LPN)Cl2] (2), were fully characterized via NMR in soln. and by an x-ray structural detn. Notably, compd. 2 reacts with an excess of Et diazoacetate (EDA) in CH2Cl2 to give a stable ?3-diethyl maleate complex, [Ru(LPN)(cis-EtO(O)CCH:CHC(O)OEt)Cl2] (3). The crystal structure of 3 has also been detd. Substitution reactions with 4-picoline (4-Me-py) performed on 1 led to two new complexes: the neutral complex [Ru(4-Me-py)(LPNO)Cl2] (5) and the salt [Ru(4-Me-py)2(LPNO)Cl](Cl) (6a). The latter compd. catalyzed the intermol. cyclopropanation of styrene with EDA in high yields and with elevated cis diastereoselectivity (i.e., cis/trans = 80/20). [on SciFinder(R)]