Synthesis, Characterization, and Reactivity of an Oxoruthenium(IV) Complex Containing a Bis(oxazoline) Ligand. Crystal Structure of [Ru((S)-bpop)(Cl)(trpy)](BF₄)

The synthesis and characterization of two [Ru(L)(O)(trpy)](ClO₄)2 complexes (where trpy = 2,2′:6′,2?-terpyridine and L = (S)- or (R)-bpop = 2,2-bis[2-[4(S)- or 4(R)-phenyl-l,3-oxazolinyl]]propane) are described. These complexes are among the first high oxidation state oxoruthenium complexes which contain an optically active ligand fixed in a position cis to the oxo moiety. The preparations of the precursor materials, [Ru(L)(Cl)(trpy)]-(BF4) and [Ru(H2O)(L)(trpy)](BF₄)₂, are also described. A single-crystal X-ray diffraction analysis of [Ru((S)-bpop)(Cl)(trpy)](BF₄) was undertaken. The crystals belong to the monoclinic system, space group P2₁, with a = 12.1507(16) Å,b= 12.3633(10) Å, c = 12.4606 (14) Å, ß = 113.332(9)°, V = 1718.9(3) ų, and Z = 2. The structure was solved and refined to R = 2.28% and R_w = 2.98% for all 6085 independent reflections. (R = 1.99% for those 5680 reflections with F_o > 6s(F_o).) This is the first report of a (bis(oxazoline))ruthenium single-crystal X-ray structural analysis. To establish the viability of these complexes for ligand effect studies, the pK_a value of the bpop ligand was measured along with the rate constant for the ligand substitution of the aqua ligand of [Ru(H₂O)((R)-bpop)(trpy)](ClO₄)₂ by acetonitrile. Our initial substrate oxidation studies of these new (bis-(oxazoline))oxoruthenium(IV) complexes with methyl p-tolyl sulfide or racemic methyl p-tolyl sulfoxide yield results consistent with our previous mechanistic studies on sulfide and sulfoxide oxidations with oxo(phosphine)-ruthenium(IV) complexes.