Preparative, carbon-13 and phosphorus-31 nuclear magnetic resonance studies on dicarbonyl complexes of ruthenium(II) and ruthenium(I) containing tertiary mono-t-butyl- or di-t-butyl-phosphines

Abstract

Some new complexes of the types cis-[RuCl₂(CO)₂(PR₂Bu^t)₂](trans-phosphines but COs and Cls cis)(R = Me, Et, Prⁿ, Buⁿ, Ph, or p-tolyl), cis-[RuCl₂(CO)₂(PRBu^t₂)₂](R = Me or Prⁿ), and trans-[RuCl₂(CO)₂(PR₂Bu^t)₂](R = Et, Prⁿ, or Buⁿ) are described. ³¹P N.m.r. data for these and other dicarbonylruthenium–tertiary phosphine complexes are given. There is a linear correlation between the chemical shift of the free phosphine, δ_free, and the co-ordination shift, Δ, on complexation for the complexes trans-[RuCl₂(CO)₂L₂]. This linear relationship does not apply to the complexes cis-[RuCl₂(CO)₂L₂], possibly because of conformational effects. The ¹³C n.m.r. spectra have been recorded for a number of the complexes cis-[RuCl₂(CO)₂L₂] and a linear relationship between the ¹³C chemical shift of the carbonyl and the force constant for the C–O stretching vibration is reported. Treatment of cis-[RuCl₂(CO)₂(PPrⁿ₂Bu^t)₂] with KOH in 2-methoxyethanol gives [RuHCl(CO)₂(PPrⁿ₂Bu^t)₂]. The benzenediazonium cation is shown to insert into the ruthenium–hydrogen bond of [RuHCl(CO)₂(PPrⁿ₂Bu^t)₂] to produce the phenyldi-imide complex [RuCl(NHNPh)(CO)₂(PPrⁿ₂Bu^t)₂]BF₄. Binuclear ruthenium(I) complexes [RuX(CO)₂L]₂[X = Cl, Br, I, or OAc; L = Pbu^t₂Ph or PBu^t₂(p-tolyl)] with a ruthenium–ruthenium bond and a bent bridging system are also described. For X = Cl, phosphorus–phosphorus nuclear spin–spin coupling of ca. 80 Hz is transmitted through the ruthenium–ruthenium bond. The bridging system in [RuCl(CO)₂L]₂ is cleaved by Cl₂ to give [Ru₂Cl₄(CO)₄L₂], which undergo bridge-splitting reactions to give mononuclear complexes [RuCl₂(CO)₂QL](Q = pyridine or PMe₂Ph) or easy reduction back to [RuCl(CO)₂L]₂. I.r., ¹H, and ³¹P n.m.r. data are given and discussed.