Bis(acetylacetonato)ruthenium(II) complexes containing bulky tertiary phosphines. Formation and redox behaviour of Ru(acac)2 (PR3) (RÂ =Â iPr, Cy) complexes with ethene, carbon monoxide, and bridging dinitrogen

Ruthenium(II) complexes of the types trans- and cis-[Ru(acac)2L2], trans- and cis-[Ru(acac)2(CO)(L)], and cis-[Ru(acac)2(η2-C2H4)(L)] (L = PiPr3, PCy3) have been prepared and the X-ray structures of several members of the series have been determined. The ruthenium(III)-ethene cation [Ru(acac)2(η2-C2H4)(PCy3)]+ has been detected by spectroelectrochemistry and is stable indefinitely at −50 °C. Ethene is readily displaced from cis-[Ru(acac)2(η2-C2H4)(PiPr3)] by dinitrogen to give the binuclear complex cis-[{Ru(acac)2(PiPr3)}2(μ-N2)], which undergoes two stepwise one-electron oxidations; the mixed-valence RuII,III mo nocation is very stable towards disproportionation to the RuIII,III dication and the neutral RuII,II species.