Metal–ylide complexes. Part I. Metallation reactions of N-(1-pyridinio)benzamidate and related compounds with palladium(II), platinum(II), rhodium(III), and iridium(III)

Abstract

The reaction of various ylides of general formula RCO··[graphic omitted] [R = Ph or m- or p-MeC₆H₄; X = N or CH; Y = pyridine, NMe₃, or PPh₃(most work has been carried out with PhCO··[graphic omitted]H₅C₅= L)] with halide salts of palladium(II), platinum(II), rhodium(III), and iridium(III) affords products containing metallated betaines. Spectroscopic data (i.r., ¹H, and ¹³C n.m.r.) show unambiguously that the aryl group R has become metallated in a position ortho to the carbonyl group and also that the ylide is bidentate (L′)via the group X. There is good evidence to indicate that the mechanism of the reaction involves preliminary co-ordination of the ylide followed by intramolecular electrophilic attack by the metal. Palladium tends to give di-µ-halogeno-complexes, [{Pd(L′)Y}₂], whereas in the case of platinum it is possible to prepare [PtL′₂] which has cis-Pt–C bonds. Rhodium affords ionic complexes, cis-[RhL′₂(H₂O)₂]Z (Z = Cl, Br, I, or BPh₄), which with 2,2′-bipyridyl give [RhL′₂(bipy)]Cl. Iridium gives a non-ionic derivative, [IrL′₂(H₂O)Cl],3H₂O. Reactions of the complexes with Ph₃P or Buⁿ₃P give new complexes containing phosphine oxide such as [PdL′{P(O)Ph₃}]Cl, [PtL′{P(O)Ph₃}Cl], [RhL′₂{P(O)-Buⁿ₃}Cl], and [IrL′₂{P(O)Ph₃}Cl]. The Pd–Cl and Pt–Cl bonds are trans to nitrogen when L = PhCO··[graphic omitted]H₅C₅. Carbon monoxide reacts reversibly with palladium and iridium complexes of PhCO··[graphic omitted]H₅C₅to give [PdL′(CO)Cl] and [IrL′₂(CO)₂]Cl. I.r. evidence suggests CO to be cis to the Pd–C bond in the palladium complex and other observations suggest that the mode of formation is not simple.