Ruthenium and osmium-nitrogen mulitple bonded complexes with chelating nitrogen and/or oxygen atom donor ligands : synthesis, structures and reactivity studies
(Uncorrected OCR) Abstract of thesis entitled RUTHENIUM AND OSMIUM-NITROGEN MULITPLE BONDED COMPLEXES WITH CHELATING NITROGEN AND / OR OXYGEN ATOM DONOR LIGANDS: SYNTHESIS, STRUCTURES AND REACTIVITY STUDIES Submitted by Yip Ka Lai for the degree of Doctor of Philosophy at The University of Hong Kong in March 2005 The chemistry of late transition metal-nitrido complexes have been a growing interest especially for nitrido-ruthenium(VI) and -osmium(VI) metal complexes. However, the reactivity studies on those nitride complexes are sparse in the literature. As a result, the reactivities of nitridoruthenium(VI) complexes toward nucleophilic, electrophilic and oxidizing agents were studied. [Ru^CNXL^Cl] [H2L1 = 2,6-bis(2,2-diphenyl-2-hydroxyethyl)pyridine] underwent nitrogen atom transfer reaction with PPI13, PPhMe2 (dimethylphenylphosphine) and dppe [l,2-bis(diphenylphosphino)ethylene] to give [RuIII(HL1)(PPh3)Cl2], [Ru^XPPhMe^Cl] and [RuIII(L1)(dppe)Cl], respectively. In the presence of py or Hpz, the reaction of [Ru^^XL^Cl] gave [RuIII(L1)(py)2Cl] and [RuIII(L1)(Hpz)3]Cl as respective products. An unsymmetrical u-nitrido dinuclear ruthenium complex, [Ru^L^ChCu-N^u^L'XCsHioN^l], was formed upon reaction of [Ru^CNXL^Cl] with 2,6-dimethylaniline. Excess (Me30)BF4 reacted with [Ru^CNXL^Cl] to give a dinuclear u-OH complex, [Ru2(N)2(L1)2(OH)]PF6. For the analogous reaction with [n-Bu4N][MVI(NXL)] [L = L2 and L3; M = Os and Ru; H4L = l,2-dichloro-4,5-bis(2-hydroxybenzamido)benzene, H4L = l,2-bis(2-hydroxybenzamido)benzene], protonation at the auxiliary ligand occurred to give [M^CNXHL)] as product. Oxidation of [n-Bu4N][OsVI(N)(L2)] by PhI(OAc)2 produced [n-Bu4N][OsVI(N)(L202)] in 10% yield. Based on X-ray crystal analysis, the coordinated phenoxy moiety was converted to a benzoquinone moiety while the Os=N group remained intact. A synthetic route for preparing ruthenium pyridyl-amine complexes bearing chelating tertiary amine 'ligands was developed. At pH 1.0, the cyclic voltammogram of [Runi(Me3tacn)(H2L3)](C104)2 revealed a reversible one-electron oxidation couple at E?= 0.21 V and an irreversible proton-coupled multi-electron wave at Epa = 1.53 V. At pH 1.0-7.0, the first couple is pH-dependent, whereas the Epa value of the second wave is pH-dependent. The second redox wave is assigned to oxidation of Ru(III) to a Ru(V) imido species. Chemical oxidation of pR.un(Tet-Me6)(H3L1)](C104)2 (H3L1 = 2-amidinopyridium) and [Ruin(Me3tacn)(H2L3)](C104)2 (H2L3 cc-(l -amino- l-methylethyl)-2-pyridinemethanol) with (NH4)2CeIV(N03)6 or bromine led to decomposition of the complexes. A synthetic route for Ru ?H3 complexes containing chelating amine ligands was developed. [RuII(pyxn)(NH3)2](C104)2 [pyxn = N,W -dimethy l-NJF -bis(2-pyridy lmethyl)cyclohexane-1,2-diamine] is an effective catalyst for aziridination of styrene by PhlNTs. Using 1,2-dichloroethane as solvent, A^-(p-tolylsulphonyl)-2-phenylaziridine was produced in up to 85 % yield. An ESI-MS study revealed that the aziridination reaction may involve a [Ru(NTs+styrene)]+ intermediate. Chemical oxidation of [Run(pyxn)(tmen)](C104)2 (tmen = 2,3-diamino-2,3-dimethylbutane) with bromine resulted in C? bond cleavage of the tmen ligand, leading to the formation of imine species. Chemical oxidation of [Run(4-'Bubipy)2(aniline)2](CF3S03)2 and [Run(Me3tacn)(bipy)(amline)](C104)2 resulted in coupling of the aniline ligand. Oxidation of [Run(TMC)(NH3)Cl]+ (TMC = l,4,8,ll-tetramethyl-l,4,8,ll-tetraazacyclotetradecane) by (NH4)2CeIV(N03)6 gave [Run(TMC)NO(OH2)]+ as the major product. By means of ESI-MS analysis, oxidation of [RuII(pyxn)(tmen)]+ by wzeta-chloroperbenzoic acid (wCPBA) produced [Ru(pyxn)(Cl-C6H4-C02)(OH2)]+ species, which has not been documented in the literature. In the presence of Zn/Hg, a nitridoosmium(VI) complex [Os(N)(L1)Cl] was transformed to a trinuclear osmium complex [Os3(H2L1)3(/w-N)2(J?OH)(/<-(CH3 C(=0)-N)(OH2))] containing two bridging nitrido ligands. The complex has been structurally characterized by X-ray crystallography and presumably, the formation of the trinuclear osmium complex occurred by nitrido coupling reaction of [Os^CL^Cl].
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:ruthenium compounds synthesis osmium ligands chelates
Date of Publication:01/01/2005