Synthesis and reactivity of cationic vinylidene and allenylidene ruthenium(II) complexes containing the phosphinoether Pri2PCH2CH2OMe as chelating ligand

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Abstract
An efficient method for the preparation of the chelate complex [RuCl2(κ2P,O-Pri 2PCH2CH2OMe)2]2, using [{RuCl2(C8H12)}n]1 as starting material, has been developed. Compound 2 reacts with terminal alkynes HCCR (R = Ph, C6H4Me-p or C6H4CCH-m) in the presence of Ag(O3SCF3) to give the octahedral cationic vinylidene complexes [RuCl(CCHR)(κ2P,O-Pri 2PCH2CH2OMe)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(CCPh)(κ2P,O-Pri 2PCH2CH2OMe)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(CCPh)(CO)2(κP-Pri 2PCH2CH2OMe)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 [RuX2(CCHPh)(κP-Pri 2PCH2CH2OMe)(κ2P,O-Pri 2PCH2CH2OMe)](X = CN, I or Br) were obtained from 4 and KCN, NaI and LiBr, respectively. The reaction of 2 with propargylic alcohols HCCCR(Ph)OH in the presence of Ag(O3SCF3), followed by treatment with acidic Al2O3, afforded the cationic allenylidene compounds [RuCl{CCC(Ph)R}(κ2P,O-Pri 2PCH2CH2OMe)2][O3SCF3](R = Ph or C6H4Me-o) in moderate yields. The crystal structure where R = Ph has been determined and reveals an almost linear RuCCC chain with one of the methoxy groups trans to the allenylidene ligand. While the R = C6H4Me-o derivative reacts with CO to give the cationic carbonyl compound [RuCl(CO)(κ2P,O-Pri 2PCH2CH2OMe)2][O3SCF3], the reaction of 4 with CO gives a mixture of this complex, 9/10, and trans,trans,trans-[RuCl2(CO)2(κP-Pri 2PCH2CH2OMe)2]. The latter is formed quantitatively from 2 and carbon monoxide.

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