Synthesis and reactivity of cationic vinylidene and allenylidene ruthenium(II) complexes containing the phosphinoether Pr(2)(i)PCH(2)CH(2)OMe as chelating ligand

An efficient method for the preparation of the chelate complex [RuCl2(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)(2)] 2, using [{RuCl2(C8H12)}(n)] 1 as starting material, has been developed. Compound 2 reacts with terminal alkynes HC=CR (R = Ph, C(6)H(4)Me-p or C6H4C=CH-m) in the presence of Ag(O3SCF3) to give the octahedral cationic vinylidene complexes [RuCl(=C=CHR)(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)(2)][O3SCF3] 4-6 in 70-80% yield. The parent derivative 3 (R = H) has been prepared analogously but is stable only under an acetylene atmosphere. Crystal structural analysis of 4 (R = Ph) confirms a cis arrangement of the chloro and vinylidene ligands. Treatment of 4 with basic Al2O3 produces, by deprotonation, a mixture of two isomers [RuCl(C=CPh)(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)(2)] 7, 8 with the alkynyl and chloro ligands in either cis or trans disposition. Compounds 7, 8 easily react by partial cleavage of the chelate bonds to give the corresponding dicarbonyl derivatives [RuCl(C=CPh)(Co)(2)(kappa P-Pr(2)(i)PCH(2)CH(2)OMe)(2)] 9, 10. The isomeric mixture can be completely converted into the thermodynamically preferred species 9 with the two CO and the alkynyl and chloro ligands cis disposed. The neutral vinylidene complexes [RuX(2)(=C=CHPh)(kappa P-Pr(2)(i)PCH(2)CH(2)OMe)(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)] (X = CN, I or Pr) were obtained from 4 and KCN, NaI and LiBr, respectively. The reaction of 2 with propargylic alcohols HC=C-CR(Ph)OH in the presence of Ag(O3SCF3), followed by treatment with acidic Al2O3, afforded the cationic allenylidene compounds [RuCl{=C=C=C(Ph)R}(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)2][O3SCF3] (R = Ph or C(6)H(4)Me-o) in moderate yields. The crystal structure where R = Ph has been determined and reveals an almost linear Ru=C=C=C chain with one of the methoxy groups trans to the allenylidene ligand. While the R = C(6)H(4)Me-o derivative reacts with CO to give the cationic carbonyl compound [RuCl(CO)(kappa(2)P,O-Pr(2)(i)PCH(2)CH(2)OMe)(2)][O3SCF3], the reaction of 4 with CO gives a mixture of this complex, 9/10, and trans,trans,trans-[RuCl2(CO)(2)(kappa P-Pr(2)(i)PCH(2)CH(2)OMe)(2)]. The latter is formed quantitatively from 2 and carbon monoxide.