Synthesis and Reactivity of [Ru(Cp*)(L)(MeCN)2][PF6] (L = Ph2POMe or Ph2P‐o‐tolyl) and {Ru(Cp*)[Ph2PCH2C(tBu)=O](MeCN)}[PF6] Complexes, Their Involvement as Catalyst Precursors for Regioselective Allylic Substitution Reactions and Related [Ru(Cp*)Cl(Ph2POMe)(RCHCHCH2)][PF6] η3‐Allyl Ruthenium(IV) In