Coordinatively Unsaturated Semisandwich Complexes of Ruthenium with Phosphinoamine Ligands and Related Species: A Complex Containing (<i>R</i>,<i>R</i>)-1,2-Bis((diisopropylphosphino)amino)cyclohexane in a New Coordination Form κ³<i>P</i>,<i>P</i>‘,<i>N</i>-η²-<i>P</i>,<i>N</i>

The syntheses of the chloro complexes [Ru(η5-C5R5)Cl(L)] (R = H, Me; L = phosphinoamine ligand) (1a−d) have been carried out by reaction of [(η5-C5H5)RuCl(PPh3)2] or {(η5-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 [(η5-C5Me5)RuCl(R,R-dippach)] with NaBAr‘4 yields the compound [(η5-C5Me5)Ru(κ3P,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 [(η5-C5Me5)RuCl(dippae)] yields the unsaturated 16 electron complex [(η5-C5Me5)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 [(η5-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 [(η5-C5R5)Ru(N2)(L)][BAr‘4] (3a−d) and dioxygen complexes [(η5-C5H5)Ru(O2)(R,R-dippach)][BPh4] (4a) and [(η5-C5Me5)Ru(O2)(L)][BPh4] (4b,d) have been prepared by chloride abstraction under dinitrogen or dioxygen atmosphere, respectively. The presence of 16 electron [(η5-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(η5-C5H5)(η6-C6H5F)][BAr‘4] (5a), which has been isolated and characterized by X-ray diffraction.