Ruthenium(II) complexes with a new potentially trifunctional phosphinoester and its enolate as ligands

Abstract

Both RuCl₃·nH₂O and [RuCl₂(PPh₃)₃]reacted with PBu^t(CH₂CO₂Me)₂ to give a mixture of two isomeric ruthenium(II) complexes [RuCl₂{PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}₂]1a and 1b(ratio 3 : 1) which contain two molecules of the ester as bidentate chelating ligands. Treatment of 1a, 1b with AgPF₆ led, after abstraction of one chloride ligand, to the cationic complex [RuCl{PBu^t[CH₂C(OMe)O]₂-κ³P,O,O}{PBu^t-[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}]PF₆2 in which one molecule of the phosphinoester is a bi- and the other a tri-dentate ligand. Reaction of 2 with KOBu^t or NaN(SiMe₃)₂ yielded the neutral phosphinoenolate-ruthenium(II) compound [RuCl{PBu^t[CHC(OMe)O][CH₂C(OMe)O]-κ³P,O,O}{PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}]3 which, by cleavage of the Ru-O(ester) bonds, reacted with CO or CNMe to give the corresponding monocarbonyl or bis(isocyanide) complexes [RuCl(CO){PBu^t[CHC(OMe)O](CH₂CO₂Me)-κ²P,O}{PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}]4 or [RuCl(CNMe)₂{PBu^t[CHC(OMe)O](CH₂CO₂Me)-κ²P,O}{PBu^t(CH₂CO₂Me)₂-κP}]5 respectively. On treatment with PhNCO compound 3 underwent an insertion reaction of the isocyanate into the C–H bond of the metal enolate to give the ring-substituted derivative [RuCl{PBu^t[C(CONHPh)C(OMe)O][CH₂C(OMe)O]-κ³P,O,O}{PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}]6. While compound 3 reacted with water in tetrahydrofuran to yield almost quantitatively the phosphino(monoester)acetate complex [RuCl{PBu^t[CH₂C(O)O][CH₂C(OMe)O]-κ³P,O,O}{PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}]7, reaction of 3 with CNBu^t, in the presence of water, yielded the bis(isocyanide) adduct [RuCl(CNBu^t)₂{PBu^t[CH₂C(O)O](CH₂CO₂Me)-κ²P,O}{PBu^t(CH₂CO₂Me)₂-κP}]8. Treatment of 3 with HCl or PhSH reconverted the phosphinoenolate into the phosphinoester moiety with concomitant formation of compounds 1a, 1b and [RuCl(SPh){PBu^t[CH₂C(OMe)O](CH₂CO₂Me)-κ²P,O}₂]9, respectively. The molecular structures of 1a and 3 have been determined by X-ray crystallography.