Synthesis and Reactivity of [Ru(Cp*)(L)(MeCN) 2 ][PF 6 ] (L = Ph 2 POMe or Ph 2 P‐ o ‐tolyl) and {Ru(Cp*)[Ph 2 PCH 2 C( t Bu)=O](MeCN)}[PF 6 ] Complexes, Their Involvement as Catalyst Precursors for Regioselective Allylic Substitution Reactions and Related [Ru(Cp*)Cl(Ph 2 POMe)(RCHCHCH 2 )][PF 6 ] η 3 ‐Allyl Ruthenium( IV ) Intermediates

The synthesis of the new complexes [Ru(Cp*)(L)(MeCN) 2 ][PF 6 ] (L = Ph 2 POMe or Ph 2 P‐ o ‐tolyl) and {Ru(Cp*)[Ph 2 PCH 2 C( t Bu)=O](MeCN)}[PF 6 ] ( 2a – c ) is achieved starting from [Ru(Cp*)(MeCN) 3 ][PF 6 ]. The acetonitrile ligands in complexes 2a – c are labile, as emphasised by the easy formation of {Ru(Cp*)(CO) 2 [Ph 2 PCH 2 C(=O) t Bu]}[PF 6 ] ( 3 ). The keto‐phosphane is used as a tool to convert 3 into {Ru(Cp*)(CO)[Ph 2 PCH 2 C( t Bu)=O]}[PF 6 ] ( 5 ). Complex 5 reacts with 1,1‐diphenyl‐2‐propyn‐1‐ol in methanol as solvent toafford the vinyl‐carbene complex {Ru(Cp*)(CO)[=C(OMe)CH=CPh 2 ][Ph 2 PCH 2 C(=O) t Bu]}[PF 6 ]. The new η 3 ‐allyl ruthenium( IV ) derivatives [Ru(Cp*)Cl(Ph 2 POMe)(CH 2 CMeCH 2 )][PF 6 ] and [Ru(Cp*)Cl(Ph 2 POMe)(RCHCHCH 2 )][PF 6 ] (R = Me; n Pr, 8d ; or Ph, 8e ) are obtained by reacting 2a with the appropriate allylic halide. The X‐ray crystal structure determination of the compounds 8d and 8e disclosed an endo‐trans ‐RCHCHCH 2 η 3 ‐allyl ligand. The formation of branched allyl aryl ethers is regioselectively favoured when complexes 2a – c are involved as catalyst precursors for the etherification of cinnamyl chloride, chlorohexene and 3‐chloro‐4‐phenylbut‐1‐ene with phenol, p ‐methoxyphenol, cresols and ( o or p )‐chlorophenols, in the presence of K 2 CO 3 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)