Coordinatively unsaturated semisandwich complexes of ruthenium with phosphinoamine ligands and related species:: A complex containing (R,R)-1,2-Bis(diisopropylphosphino)amino)cyclohexane in a new coordination form κ3P,P',N-η2 P,N

The syntheses of the chloro complexes [Ru(eta(5)-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a-d) have been carried out by reaction of [(eta(5)-C5H5)RuCl(PPh3)(2)] or {(eta(5)-C5Me5)RuCl}(4) with the corresponding phosphinoamine (R,R)-1,2-bis((diisopropylphosphino)amino)cyclohexane), R,R-dippach, or 1,2-bis(((diisopropylphosphino)amino)ethane), dippae. The chloride abstraction reactions from these compounds lead to different products depending on the starting chlorocomplex and the reaction conditions. Under argon atmosphere, chloride abstraction from [(eta(5)-C5Me5)-RuCl(R,R-dippach)] with NaBAr'(4) yields the compound [(eta(5)-C5Me5)Ru(kappa P-3,P'-(R,R)-dippach)][BAr'(4)](2b) which exhibits a three-membered ring Ru-N-P by a new coordination form of this phosphinoamine. However, under the same conditions the reaction starting from [(eta(5) -C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(Y5C5Me5)Ru(dippae)][BAr'(4)] (2d). The bonding modes of R,R-dippach and dippae ligands have been analyzed by DFT calculations. The possibility of tridentate P,N,P-coordination of the phosphinoamide ligand to a fragment [(eta(5)-C5Me5)Ru](+) is always present, but only the presence of a cyclohexane unit in the ligand framework converts this bonding mode in a more favorable option than the usual P,P-coordination. Dinitrogen [(eta(5)-C5R5)Ru(N-2)(L)][BAr'(4)] (3a-d) and dioxygen complexes [eta(5)-C5H5)Ru(O-2)(R,R-dippach)][BPh4] (4a) and [(eta(5)-C5Me5)Ru(O-2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(eta(5)-C5H5)Ru(R,R-dippach)](+) species in fluorobenzene solutions of the corresponding dinitrogen or dioxygen complexes in conjunction with the presence of [BAr'(4)](-) gave in some cases a small fraction of [Ru(eta(5)-C5H5)(eta(6)-C6H5F)][BAr'(4)] (5a), which has been isolated and characterized by X-ray diffraction.