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Interconversion between CO2 + H2 and FA/formate is the most promising strategy for the fixation of carbon dioxide and reversible hydrogen storage; however, FA dehydrogenation and CO2 hydrogenation are usually studied separately using different catalysts for each reaction. This report describes of the catalysis of [Cp*Ir(N∧N)(X)]n+ (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; X = Cl, n = 0; X = H2O, n = 1) bearing a proton-responsive N∧N pyridylpyrrole ligand for both reactions. Complex 2-H2O catalyzes FA dehydrogenation at 90 °C with a TOFmax of 45 900 h-1. Its catalysis is more active in aqueous solution than in neat solution under base-free conditions. These complexes also catalyze CO2 hydrogenation in the presence of base to formate under atmospheric pressure (CO2/H2 = 0.05 MPa/0.05 MPa) at 25 °C with a TOF value of 4.5 h-1 in aqueous solution and with a TOF value of 29 h-1 in a methanol/H2O mixture solvent. The possible mechanism is proposed by intermediate characterization and KIE experiments. The extraordinary activity of these complexes are mainly attributed to the metal-ligand cooperative effect of the the pyrrole group to accept a proton in the dehydrogenation of formic acid and assist cooperative heterolytic H-H bond cleavage in CO2 hydrogenation.

Spurred by the rapid growth of Ru-based complexes as molecular water oxidation catalysts (WOCs), we propose novel ruthenium(II) complexes bearing pyridylpyrrole-carboxylate (H2ppc) ligands as members of the WOC family. The structure of these complexes has 4-picoline (pic)/dimethyl sulfoxide (DMSO) in [Ru(ppc)(pic)2(dmso)] and pic/pic in [Ru(ppc)(pic)3] as axial ligands. Another ppc2- ligand and one pic ligand are located at the equatorial positions. [Ru(ppc)(pic)2(dmso)] behaves as a WOC as determined by electrochemical measurement and has an ultrahigh electrocatalytic current density of 8.17 mA cm-2 at 1.55 V (vs NHE) with a low onset potential of 0.352 V (vs NHE), a turnover number of 241, a turnover frequency of 203.39 s-1, and kcat of 16.34 s-1 under neutral conditions. The H2O/pic exchange of the complexes accompanied by oxidation of a ruthenium center is the initial step in the catalytic cycle. The cyclic voltametric measurements of [Ru(ppc)(pic)2(dmso)] at various scan rates, Pourbaix diagrams (plots of E vs pH), and kinetic studies suggested a water nucleophilic attack mechanism. HPO42- in a phosphate buffer solution is invoked in water oxidation as the proton acceptor.

Treatment of [Ir(PPh3)3Cl] with 2-[5-(pyridin-2-yl)-1H-pyrrol-2-yl]pyridine (Hdpp) in refluxing toluene affords an unexpected pyrrole-metalated iridium(III) hydride complex, [Ir(K2C,N-dpp)(H)(Cl)(PPh3)2] (1), via Cpyrrole-H activation, while the presence of the base KOtBu as the deprotonation reagent produces a pyridine-metalated iridium(III) hydride complex, [Ir(K3C,N,N-dpp)(H)(PPh3)2] (2), via Cpyridine-H activation. Treatment of [Ir(PPh3)3Cl] prepared by a convenient method with Hdpp in the presence of KOtBu under the refluxing mixture solvent toluene/methanol (2:1, v/v) generates the N,N-chelating complex [Ir(K2N,N-dpp)(H)(Cl)(PPh3)2] (3) together with 1 and the N,N-chelating dihydride complex [Ir(K2N,N-dpp)(H)2(PPh3)2] (4). Complex 4 is also readily produced by the reaction of [Ir(PPh3)3Cl] and Hdpp in the presence of KOtBu under refluxing methanol or by the reaction of IrCl3 and PPh3 in refluxing 2-ethoxyethanol. Complexes 1-4 are fully characterized by NMR, IR, and UV-vis spectroscopy and X-ray diffraction analysis. The dpp-/dpp2- ligand shows rich coordination capability, of which pyridine- and pyrrole-cyclometalated coordination modes are first reported. The formation of structural isomers 1 and 3 involved the selective activation of the C-H and N-H bonds of Hdpp is rationalized by theoretical calculations.

Treatment of [Ru 3 (CO) 12 ] with 2,5-di(2-pyridyl)pyrrole (HL1) and 2,5-di(2-(5-bromopyridyl)pyrrole (HL2) in refluxing toluene afforded the dinuclear Ru(I) carbonyl complexes [Ru 2 (CO) 4 (L)] (L = L1 ( 1 ), L2 ( 3 ), respectively). Alternatively, 1 along with a minor mononuclear product [Ru(CO) 2 (L1) 2 ] ( 2 ) was synthesized from reaction of [Ru(CO) 2 Cl 2 ] n with HL1 in methanol in the presence of triethylamine. Complexes 1 – 3 have been fully characterized by NMR, IR, UV–vis, ESI-MS, and elementary analysis. Single-crystal X-ray diffraction indicates that both 1 and 3 feature a Ru–Ru single bond and the di(pyridyl)pyrrolide ligands bind to the two Ru(I) centers in a μ-κ 2 N,N’ :κ 1 N” chelating-bridging mode. Complex 2 is mononuclear Ru(II) complex with two κ 2 N , N ’ di(pyridyl)pyrrolide ligand. The spectroscopic and electrochemical properties of 1 and 3 were also explored.

The diethylphosphonate ligand HL 1 substituted pyridylpyrrole was synthesized by treatment of 2-bromo-6-(1H'-pyrrol-2-yl)pyridine and diethylphosphite in presence of base triethylamine and catalyst Pd(PPh 3 ) 4 under refluxing toluene conditions. The HL 1 ligand was treated with bromotrimethylsilane and followed hydrolysis by methanol to afford diphosphonic acid ligand H 3 L 2 . Treatment of H 3 L 2 with [Ru(NO)Cl 3 ] in presence of triethylamine in refluxing thf was generated diruthenium nitrosyl complex [Ru(L 2 )(NO)(Cl)] 2 ·(Et 3 NH) 2 ([ 1 ]·(Et 3 NH) 2 ), which is water soluble. The ligands and metal complex were fully characterized by NMR, IR, ESI-MS and single crystal X-ray diffraction technology. The solid state structure analysis displays 1 2- is dinuclear species, of which two ruthenium atoms are linked by two PO 3 2- groups. Photorelease of nitric oxide from 1 2- was monitored by UV-Vis spectra and the amount of the NO was determined by Griess reaction and DPPH radical scavenging reaction.

We herein report the synthesis and characterization of a series of ruthenium-substituted Keggin-type heteropolytungstates containing {Ru(II)(NO)}, {Ru(III)(H2O)} or {Ru(IV)Cl} species. Although anionic [PW11O39Ru(II)(NO)](4-) (1) and [PW11O39Ru(III)(H2O)](4-) (2) are known, a new synthetic method for the preparation of (n-Bu4N)4[1] and (n-Bu4N)4[2] is developed in this paper. Treatment of (n-Bu4N)4[XW11O39(Ru[triple bond, length as m-dash]N)] with Me3NO afforded the ruthenium(ii) nitrosyl complex (n-Bu4N)4[1] in almost quantitative yield. Photolysis of (n-Bu4N)4[1] solution in CH3CN/H2O gives (n-Bu4N)4[2], which is readily oxidized by PhICl2 to yield the Ru(IV) complex (n-Bu4N)4[PW11O39Ru(IV)Cl] ((n-Bu4N)4[3]). These complexes are fully characterized by (1)H NMR and (31)P NMR spectroscopy, infrared spectroscopy, cyclic voltammetry, elemental analysis, thermogravimetric-differential thermal analysis, electrospray ionization mass spectrometry (ESI-MS) and X-ray photoelectron spectroscopy (XPS).

The treatment of [Ce(LOEt)2(NO3)2] (LOEt– = [Co(η5-C5H5){P(O)(OEt)2}3]–) with KMnO4 in water afforded a diamagnetic purple solid 1, which is tentatively formulated as a CeIV permanganate complex, “[Ce(LOEt)2(MnO4)2]”. The ZrIV analogue, [Zr(LOEt)2(MnO4)2] (2), has been prepared similarly from [Zr(LOEt)2(NO3)2] and KMnO4. The recrystallization of 1 from CH2Cl2/hexanes at –18 °C led to the isolation of dinuclear [(CeLOEt)2(μ-LOEt′)2][MnO4]2 (3), which contains the dianionic tripodal ligand [LOEt′]2– ([(η5-C5H5)Co{P(O)(OEt)2}2{P(O)2(OEt)}]2–). The reactions of 1 with K[ReO4] and [NH4][OsO3N] afforded the heterodimetallic complexes [Ce(LOEt)2(ReO4)2] (4) and [Ce(LOEt)2(NOsO3)2] (5), respectively. The crystal structures of 3 and 5 have been determined. Freshly prepared 1 can oxidize alkylbenzenes such as toluene, ethylbenzene, and cumene at room temperature to give the corresponding ketone and/or alcohol products. Ce–LOEt complexes are efficient promoters of the aerobic oxidation of alkylbenzenes by a radical mechanism. For example, cumene in the presence of [Ce(LOEt)2(H2O)2]Cl (1 mM) in air at 100 °C for 10 h afforded a ca. 6:1 mixture of 2-phenyl-2-propanol and acetophenone with a total turnover number of 6810.

Ruthenium(VI) complexes with a sterically bulky bidentate Schiff base ligand, 2-[(2,6-diisopropylphenyl)imino]methyl-4,6-dibromophenolate (L−), have been synthesized and their reactivity studied. Treatment of [Bun4N][Ru(N)Cl4] in tetrahydrofuran with 2 equivalents of NaL afforded cis-[Ru(N)Cl(L)2] (1) that reacted with Ag(OTf) (OTf− = triflate) in acetone to give trans-[Ru(N)(H2O)L2][OTf] (2). Reactions of complex 1 with Me3NO and elemental sulfur afforded cis-[Ru(NO)(Cl)L2] (3) and cis-[Ru(NS)(Cl)L2] (4), respectively. Reaction of complex 1 with Me3SiN3 in MeCN afforded [Ru(MeCN)(Cl)L2], which could alternatively be prepared by photolysis of complex 3 in CH2Cl2–MeCN with UV light. The crystal structures of complexes 1 and 2 have been determined.

Treatment of the 2,5-bis(2′-pyridyl)pyrrolato (PDP−) anion with {Ru(COD)Cl2}n in THF readily yielded [Ru(PDP)(COD)Cl] (1) in almost quantitative yield. Anion metathesis of 1 in organic solvent by NO3− and OTf− (OTf− = triflato) gave [Ru(PDP)(COD)(NO3)] (2) and [Ru(PDP)(COD)(OTf)] (3), and in aqueous solution by BF4− and PF6− afforded aqueous complexes [Ru(PDP)(COD)(H2O)](BF4) (4+·BF4−) and [Ru(PDP)(COD)(H2O)](PF6) (4+·PF6−), respectively. Treatment of 1 with PhICl2 in CH2Cl2 afforded 5 with halogenated pyrrole. These complexes exhibit similar structure, including one Ru(II) atom, one 2,5-bis(2′-pyridyl)pyrrole and one monodentate anion or aqua ligand. Each Ru(II) tightly binds to three adjacent coplanar sites of PDP− ligand to form a meridional configuration. Complex 1 with NaIO4 as the oxidant in EtOAc–CH3CN–H2O (ratio = 3 : 1 : 2) proved to be highly effective in the catalytic oxidation of olefins to carbonyl products.

Dinuclear ruthenium nitrido complexes supported by the Kläui's tripodal ligand [CpCo{P(O)(OEt)(2)}(3)](-) (L(OEt)(-)) have been synthesized starting from the ruthenium(VI) nitrido precursor [L(OEt)Ru(VI)(N)Cl(2)] (1). Heating a solution of 1 in CCl(4) at reflux, followed by recrystallization from hexane under nitrogen, afforded the mixed-valence ruthenium(V)-ruthenium(IV) μ-nitrido complex [L(OEt)Cl(2)Ru(V)(μ-N)Ru(IV)Cl(2)L(OEt)] (2). The cyclic voltammogram of 2 exhibited reversible couples at 0.19 and 1.13 V versus Cp(2)Fe(+/0), which are assigned as the Ru(V)-Ru(IV)/Ru(IV)-Ru(IV) and Ru(V)-Ru(V)/Ru(V)-Ru(IV) couples, respectively. Recrystallization of 2 from Et(2)O/heptane in air yielded the diamagnetic Ru(IV)-Ru(IV) complex [H(13)O(6)][{L(OEt)Ru(IV)Cl(2)}(2)(μ-N)] ([H(13)O(6)][2]), which underwent cation exchange with n-Bu(4)NOH to give [n-Bu(4)N][2]. X-ray diffraction revealed that the complex anions in [H(13)O(6)][2] and [n-Bu(4)N][2] contain linear, symmetric Ru-N-Ru bridges. Treatment of 1 with [(η(6)-p-cymene)Ru(II)Cl(2)](2) in benzene afforded the tetranuclear ruthenium(IV) complex [L(OEt)Cl(2)Ru(IV)(μ-N)Ru(IV)(H(2)O)Cl(2)](2) (3) containing symmetric Ru(IV)-N-Ru(IV) bridges. The reaction of 1 with [Ru(II)(H)(Cl)(CO)(PCy(3))(2)] (Cy = cyclohexyl) gave the ruthenium(VI)-ruthenium(II) nitrido complex [L(OEt)Cl(2)Ru(VI)(μ-N)Ru(II)(H)Cl(CO)(PCy(3))(2)] (4). The observed short Ru(II)-N bond distance [1.915(5) Å] and high C-O stretching frequency (1985 cm(-1)) in 4 are suggestive of π interaction between Ru(II) and the nitride.

Treatment of [Ru( CHR)Cl2(PCy3)2] (Cy = cyclohexyl) with Tl[N(Pr2iPO)2] and AgLOEt (LOEt− = [CpCo{P(O)(OEt)2}3]−) afforded the Ru carbene complexes [Ru( CHPh)(PCy3)Cl{N(Pr2iPO)2}] (1) and [LOEtRu( CHR)(PCy3)Cl] (2), respectively. Chloride abstraction of complex 2 with TlPF6 in MeCN afforded [LOEtRu( CHPh)(PCy3)(MeCN)][PF6] (3). Complexes 1 and 2 are capable of catalyzing ring-closing metathesis of diethyl 1,2-diallylmalonate. The crystal structure of complex 2 has been determined.

Bismuth(III) compounds containing the Klaui's oxygen tripodal ligand [CpCo{P(O)(OEt)(2)}(3)](-) (L(OEt)(-)) have been synthesized, and their interactions with dichromate in aqueous media were studied. The treatment of Bi(5)O(OH)(9)(NO(3))(4) with NaL(OEt) in water afforded [L(OEt)Bi(NO(3))(2)](2) (1), whereas that of BiCl(3) with NaL(OEt) in CH(2)Cl(2) yielded L(OEt)BiCl(2) (2). Chloride abstraction of 2 with AgX afforded [L(OEt)BiX(2)](2) [X(-) = triflate (OTf(-)) (3), tosylate (OTs(-)) (4)]. In aqueous solutions at pH > 4, 4 underwent ligand redistribution to give the bis(tripod) complex [(L(OEt))(2)Bi(H(2)O)][OTs] (5). The treatment of 4 with Na(2)Cr(2)O(7) in acetone/water afforded the Bi(III)/Cr(VI) oxo cluster [(L(OEt))(4)Bi(4)(μ(3)-CrO(4))(2)(μ(3)-Cr(2)O(7))(2)] (6) containing a unique Bi(4)Cr(4)O(12) oxometallic core. Compound 6 oxidized benzyl alcohol to give ca. 6 equiv of benzaldehyde. The reaction between 2 and CrO(3) yielded [L(OEt)Bi(OCrO(2)Cl)](2)(μ-Cl)(2) (7). The crystal structures of complexes 4-7 have been determined.

Treatment of Ru(CO)(Cl)(H)(PPh3)3 with NaLOEt (LOEt − = [CpCo{P(O)(OEt)2}3]−) afforded the hydride complex (PPh3)(CO)-LOEtRu(H) (1), which has been characterized by X-ray crystallography. Similarly, the tricyclohexylphosphine analogue, (PCy3)(CO)LOEtRu(H) (2), was synthesized from Ru(CO)Cl(H)(PCy3)2 and NaLOEt. Treatment of complex 1 with R’sO2N3 afforded the (arylsulfonyl)amido complexes LOEtRu(CO)(PPh3)(NHSO2R) (R = 2,4,6-i-Pr3C6H2 (3), 4-t-BuC6H4 (4)). The crystal structure of complex 3 has been determined. The Ru-N distance and Ru-N-S angle in 3 are 2.076(3) A and 126.14(16)°, respectively. Reactions of complex 1 with acids have been studied.

Heating [Rh(dtbpy)(κ2-C,C′-CH2CMe2C6H4)(CH2CMe2Ph)] (1; dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridyl) in p-xylene at 110 °C resulted in the formation of the 2-tert-butylphenyl complex [Rh(dtbpy)(κ2-C,C′-CH2CMe2C6H4)(C6H4tBu-2)] (3). Treatment of complex 1 with diethyl phosphite gave the phosphito-bridged dimer [Rh(dtbpy)(κ2-C,C′-CH2CMe2C6H4){P(O)(OEt)2}]2 (4). Refluxing [Ir(dtbpy)(κ2-C,C′-CH2CMe2C6H4)(C6H4tBu-2)] (2) with 2-phenylpyridine (ppyH) and 4-(2-pyridyl)benzaldehyde in toluene followed by column chromatography afforded [Ir(dtbpy)(CH2CMe2Ph)Cl(κ2-N,C-ppy)] (5) and the carbonyl complex [Ir(dtbpy)(CH2CMe2Ph)(CO)(R)] (6) [R = 4-(2-pyridyl)phenyl], respectively. Anion metathesis of [M(dtbpy)(CH2CMe2Ph)(H2O)(OTs)2] with NaBArF4 [ArF = 3,5-(CF3)2C6H3] afforded cationic [M(dtbpy)(CH2CMe2Ph)(H2O)(μ-OTs)]2[BArF4]2 [M = Rh (7), Ir (8)] that are capable of catalyzing H/D exchange of tetrahydrofuran by using D2O as the deuterium source. The crystal structures of complexes 4–7 were determined.

Treatment of [Cp∗Ir(ppy)Cl] (Cp∗ = η5-C5Me5, ppyH = 2-(2-pyridyl)phenyl) with Ag(OTf) (OTf− = triflate) in MeOH and MeCN gave the solvento complexes [Cp∗Ir(ppy)(solv)][OTf] (solv = MeOH (1) and MeCN (2)). Complex 1 is capable of catalyzing oxidation and azirdination of styrene with PhIO and PhINTs (Ts = tosyl), respectively. Treatment of 2 with a stoichiometric amount of PhINTs resulted in the insertion of the NTs group into the Ir–C(ppy) bond and formation of [Cp∗Ir(η2-ppy-NTs)(MeCN)][OTf] (3). Treatment of 1 with R2E2 afforded [Cp∗Ir(ppy)(η1-R2E2)][OTf] (E = S (4), Se (5), Te (6)). Reactions of 4 and 5 with Ag(OTf) resulted in cleavage of the E–E bond and insertion of an ER group into the Ir–C(ppy) bond. The crystal structures of complexes 2–6 and [Cp∗Ir(η2-ppy-S-p-tol)(H2O)][OTf]2 have been determined.

Treatment of Ru(═CHPh)Cl2(PCy3)2 (Cy = cyclohexyl) with K[N(i-Pr2PS)2] afforded a mixture of Ru(═CHPh)[N(i-Pr2PS)2](PCy3)Cl (1) and Ru(═CHPh)[N(i-Pr2PS)2]2 (2). Reaction of 1 with TlOPh gave Ru(═CHPh)[N(i-Pr2PS)2](PCy3)(OPh) (3), whereas that with NaOMe yielded the Ru(II) hydride compound Ru(H)[N(i-Pr2PS)2][PCy2(η2-C6H9)] (4), in which the dicyclohexyl(cyclohex-3-enyl)phosphine ligand binds to Ru via the phosphorus atom and the C═C bond of the cyclohex-3-enyl ring. The structures of complexes 3 and 4 have been established by X-ray crystallography.

Treatment of [Bun4N][Ru(N)Cl4] with Na(OR) afforded [Bun4N][Ru(N)(OR)4] (R = C6F5 (1), C6F4H (2), C6Br5 (3)), whereas that with [Bun4N][Os(N)Cl4] gave [Bun4N][Os(N)(OR)3Cl] (R = C6F5 (4), C6F4H (5), C6Br5 (6)). Treatment of [Bun4N][M(N)Cl4] with Na(SC6F4H) and Na(Sxyl) (xyl = 2,6-dimethylphenyl) afforded [Bun4N][M(N)(SC6F4H)4] (M = Ru (7), Os (8)) and [Bun4N][M(N)(Sxyl)4] (M = Ru (9), Os (10)), respectively. The crystal structures of compounds 1, 6 and 9 have been determined.

Interaction of [LOEtZrF3] ( L OEt - = [Co(η5-C5H5){P(O)(OEt)2}3]−) (1) with 3 equivalents of bis(trimethylsilyl) sulfate afforded the ZrIV hydrogensulfato complex [(LOEt)2Zr2(SO4)2(HSO4)2] (2) that reacted with Et3N to give [Et3NH][LOEtZr(H2O)(SO4)2] (3). Treatment of complex 1 with 3 equivalents of trimethylsilyl acetate afforded [LOEtZr(OCOCH3)3] (4), whereas that with 1 and 2 equivalents of trimethylsilyl trimethylsiloxyacetate yielded [LOEtZrF(OCOCH2O)]2 (5) and [LOEtZr(OCOCH2OH)(OCOCH2O)]2 (6), respectively. The crystal structures of complexes 2 and 6 have been determined.

Self-assemblies of two unsymmetrical tridentate N2O/N2S donor Schiff base ligands, that is, 2-((2-(dimethylamino)ethylimino)methyl)phenol (HL1) and methyl-2-pyridylmethylidenehy-drazinecarbodithioate (HL2), with different cadmium salts have led to 11 anion-controlled complexes, namely, [Cd(Ln)2] [n = 1 for 1 and n = 2 for 2], [Cd(L1)(HL1)](ClO4) (3), [Cd(HL2)(L2)](ClO4)(H2O) (4), [Cd(L2)Cl2] (5), [Cd(L1)Cl]2 (6), [Cd(L1)(NO3)]2 (7), [Cd(L2)(NO3)(CH3OH)]2 (8), [Cd(L2)(NO3)(H2O)]2 (8a), [Cd2(L1)2(SCN)2]n (9), and [CdL2(SCN)2]n (10), respectively. Eleven compounds were characterized by elemental analyses, IR spectra, MS and thermogravimetric analyses, of which 10 structures 2, 3, 4, 5, 6, 7, 8, 8a, 9, and 10 were further determined by single-crystal X-ray diffraction analyses. The compounds 2, 3, and 4 are mononuclear, in which the neutral molecule unit CdII(L2)2 (in 2) as well as cation units [CdII(HL1−2)(L1−2)]+ (L1 for 3 and L2 for 4) are respectively connected by hydrogen bonds C−H···S, O−H···O, and C−H·...

The Klaui oxygen tripodal ligands [(η 5 -C 5 H 5 )Co{P(O)(OR) 2 } 3 ] − (L OR − where R = alkyl group), which have been recognized as oxygen analogues of cyclopentadienyl, can form stable complexes with a range of main group and transition metal ions. This review reports on the recent developments in the coordination and organometallic chemistry of the Klaui tripodal ligands. Special attention will be paid to polynuclear M-L OEt (M = Ti, Zr) oxo and hydroxo compounds that may serve as models for group 4 metal aqua ions.

Treatment of [n-Bu4N][Ru(N)Cl4] with [AgL(OEt)] (L(OEt)- = [(eta5-C5H5)Co{P(O)(OEt)2}3]-) afforded the ruthenium(VI) nitrido complex [L(OEt)Ru(N)Cl2] (1), which reacted with PPh3 to give the ruthenium(IV) phosphiniminato complex [L(OEt)Ru(NPPh3)Cl2] (2). The cyclic voltammogram of 2 displays the RuIV/III couple at ca. 0 V vs ferrocenium/ferrocene. Treatment of 1 with Me3NO afforded [LOEtRu(NO)Cl2] (3), which reacted with Ag(OTf) (OTf- = triflate) to give the chloro-bridged tetranuclear ruthenium/silver complex [L(OEt)Ru(NO)Cl2]2[Ag(OTf)]2 (4). Treatment of 1 with Na2S2O3 gave the thionitrosyl complex [L(OEt)Ru(NS)Cl2] (5). The solid-state structures of 1-4 have been established by X-ray crystallography.

Treatment of [Ti(OPri)2Cl2] with K(tpip) (tpip− = [N(PPh2O)2]−) followed by chlorination with HCl afforded cis-[Ti(tpip)2Cl]2 (1). Reduction of 1 with Na/Hg in THF gave [Ti(tpip)3] (2), which could also be prepared from [TiCl3(THF)3] and K(tpip). Recrystallization of [V(O)(tpip)2] (3) from CH2Cl2–Et2O in air afforded trinuclear [{V(O)}3(μ-tpip)3(μ-O)3] (4). Treatment of [Cr(NBut)2Cl2] and [Cr(NBut)Cl3(dme)] (dme = 1,2-dimethoxyethane) with [Ag(tpip)]4 led to isolation of [Cr(tpip)3] (6) and [Cr(NBut)(tpip)2Cl] (7), respectively. The Ti- and V-tpip complexes are capable of catalyzing oxidation of sulfides with tert-butyl hydroperoxide and H2O2. The crystal structures of 1, 2, and 4 have been determined.

Treatment of [L OEt Ti(OTf) 3 ] ( L OEt − = [ CpCo { P ( O ) ( OEt ) 2 } 3 ] - , OTf − = triflate) with S -binapO 2 (binap = 2,2′-bis(diphenylphosphinoyl)-1,1′-binaphthyl) afforded the terminal hydroxo complex [L OEt Ti( S -binapO 2 )(OH)][OTf] 2 ( 1 ). Treatment of [L OEt Ti(OTf) 3 ] with K(tpip) (tpip − = [N(Ph 2 PO) 2 ] − ) afforded [L OEt Ti(tpip)(OTf)][OTf] ( 2 ) that reacted with CsOH to give [L OEt Ti(tpip)(OH)][OTf] ( 3 ). The structures of 1 and 2 have been determined.

Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaL(OEt) (L(OEt) (-)=[(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)}(3)](-)) afforded the mu-sulfato complex [(L(OEt)Ti)(2)(mu-O)(2)(mu-SO(4))] (2). In more concentrated sulfuric acid (>1 M), the same reaction yielded the di-mu-sulfato complex [(L(OEt)Ti)(2)(mu-O)(mu-SO(4))(2)] (3). Reaction of 2 with HOTf (OTf=triflate, CF(3)SO(3)) gave the tris(triflato) complex [L(OEt)Ti(OTf)(3)] (4), whereas treatment of 2 with Ag(OTf) in CH(2)Cl(2) afforded the sulfato-capped trinuclear complex [{(L(OEt))(3)Ti(3)(mu-O)(3)}(mu(3)-SO(4)){Ag(OTf)}][OTf] (5), in which the Ag(OTf) moiety binds to a mu-oxo group in the Ti(3)(mu-O)(3) core. Reaction of 2 in H(2)O with Ba(NO(3))(2) afforded the tetranuclear complex (L(OEt))(4)Ti(4)(mu-O)(6) (6). Treatment of 2 with [{Rh(cod)Cl}(2)] (cod=1,5-cyclooctadiene), [Re(CO)(5)Cl], and [Ru(tBu(2)bpy)(PPh(3))(2)Cl(2)] (tBu(2)bpy=4,4'-di-tert-butyl-2,2'-dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L(OEt))(2)Ti(2)(O)(2)(SO(4)){Rh(cod)}(2)][OTf](2) (7), [(L(OEt))(2)Ti(O)(2)(SO(4)){Re(CO)(3)}][OTf] (8), and [{(L(OEt))(2)Ti(2)(mu-O)}(mu(3)-SO(4))(mu-O)(2){Ru(PPh(3))(tBu(2)bpy)}][OTf](2) (9), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 mu(B). Treatment of zirconyl nitrate with NaL(OEt) in 3.5 M sulfuric acid afforded [(L(OEt))(2)Zr(NO(3))][L(OEt)Zr(SO(4))(NO(3))] (10). Reaction of ZrCl(4) in 1.8 M sulfuric acid with NaL(OEt) in the presence Na(2)SO(4) gave the mu-sulfato-bridged complex [L(OEt)Zr(SO(4))(H(2)O)](2)(mu-SO(4)) (11). Treatment of 11 with triflic acid afforded [(L(OEt))(2)Zr][OTf](2) (12), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{L(OEt)Zr(SO(4))(H(2)O)}(3)(mu(3)-SO(4))][OTf] (13). The Zr(IV) triflato complex [L(OEt)Zr(OTf)(3)] (14) was prepared by reaction of L(OEt)ZrF(3) with Me(3)SiOTf. Complexes 4 and 14 can catalyze the Diels-Alder reaction of 1,3-cyclohexadiene with acrolein in good selectivity. Complexes 2-5, 9-11, and 13 have been characterized by X-ray crystallography.

The treatment of [Ru(L(OEt))(N)Cl(2)] (1; L(OEt)(-) = [Co(η(5)-C(5)H(5)){P(O)(OEt)(2)}(3)](-)) with Et(3)SiH affords [Ru(L(OEt))Cl(2)(NH(3))] (2), whereas that with [Ru(L(OEt))(H)(CO)(PPh(3))] (3) gives the dinuclear imido complex [(L(OEt))Cl(2)Ru(μ-NH)Ru(CO)(PPh(3))(L(OEt))] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) Å. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10(-5) M(-1) s(-1).

The treatment of HfCl(4) with NaL(OEt) (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)}(3)](-)) in nitric acid afforded L(OEt)Hf(NO(3))(3) (1). Hydrolysis of 1 in acetone/water (4:1, v/v) yielded the hydroxy-bridged dimer [(L(OEt))(2)Hf(2)(H(2)O)(4)(mu-OH)(2)][NO(3)](4) (2). The treatment of (NH(4))(2)[Ce(NO(3))(6)] with 2 equiv of NaL(OEt) in water afforded (L(OEt))(2)Ce(NO(3))(2) (3), whereas that with 1 equiv of NaL(OEt) in CH(2)Cl(2) gave L(OEt)Ce(NO(3))(3) (4). While 4 is stable in organic solvents such as acetone, it was converted completely to 3 in acetone/water. The treatment of 3 with bis(p-nitrophenyl)phosphate (BNPP) afforded (L(OEt))(2)Ce[eta(1)-OPO(OR)(2)](2) (5; R = p-NO(2)C(6)H(4)), whereas the reaction of 4 with NaPO(2)(OR)(2) yielded dinuclear [L(OEt)Ce(NO(3))(2){mu-O(2)P(OR)(2)}](2) [R = p-NO(2)C(6)H(4) (6), Ph (7)]. The addition of 3 in acetone to an aqueous solution of NaH(2)PO(4) yielded the cerium(IV) dihydrogen phosphate complex (L(OEt))(2)Ce(PO(4)H(2))(2) (8). Complexes 1-5 and 7 have been characterized by X-ray crystallography. The hydrolysis of BNPP with L(OEt)M(NO(3))(3) (M = Zr, Hf, Ce) in acetone/water has been studied by (1)H NMR spectroscopy. At 25 degrees C, with [Ce] = 20[BNPP], in an acetone-d(6)/N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (4:1, v/v) buffer solution (50 mM) (4:1, v/v), the hydrolysis of BNPP with 4 was found to exhibit first-order kinetics with a rate constant of (1.1 +/- 0.1) x 10(-3) s(-1).

Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaL(OEt) (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)](3)](-)) in the presence of Na(3)PO(4) and Na(4)P(2)O(7) led to isolation of [(L(OEt)Ti)(3)(mu-O)(3)(mu(3-)PO(4))] (1) and [(L(OEt)Ti)(2)(mu-O)(mu-P(2)O(7))] (2), respectively. The structure of 1 consists of a Ti(3)O(3) core capped by a mu(3)-phosphato group. In 2, the [P(2)O(7)](4-) ligands binds to the two Ti's in a mu:eta(2),eta(2) fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaL(OEt) and 1.5 equiv of Na(2)Cr(2)O(7) gave [(L(OEt)Ti)(2)(mu-CrO(4))(3)] (3) that contains two L(OEt)Ti(3+) fragments bridged by three mu-CrO(4)(2-)-O,O' ligands. Complex 3 can act as a 6-electron oxidant and oxidize benzyl alcohol to give ca. 3 equiv of benzaldehyde. Treatment of [L(OEt)Ti(OTf)(3)] (OTf(-) = triflate) with [n-Bu(4)N][ReO(4)] afforded [[L(OEt)Ti(ReO(4))(2)](2)(mu-O)] (4). Treatment of [L(OEt)MF(3)] (M = Ti and Zr) with 3 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(3)] (5) and [L(OEt)Zr(ReO(4))(3)(H(2)O)] (6), respectively. Treatment of [L(OEt)MF(3)] with 2 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(2)F] (7) and [[L(OEt)Zr(ReO(4))(2)](2)(mu-F)(2)] (8), respectively, which reacted with Me(3)SiOTf to give [L(OEt)M(ReO(4))(2)(OTf)] (M = Ti (9), Zr (10)). Hydrolysis of [L(OEt)Zr(OTf)(3)] (11) with Na(2)WO(4).xH(2)O and wet CH(2)Cl(2) afforded the hydroxo-bridged complexes [[L(OEt)Zr(H(2)O)](3)(mu-OH)(3)(mu(3)-O)][OTf](4) (12) and [[L(OEt)Zr(H(2)O)(2)](2)(mu-OH)(2)][OTf](4) (13), respectively. The solid-state structures of 1-3, 6, and 11-13 have been established by X-ray crystallography. The L(OEt)Ti(IV) complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic Ti/ Re complexes 5 and 9 were found to be more active catalysts for the sulfide oxidation than other Ti(IV) complexes presumably because Re alkylperoxo species are involved as the reactive intermediates.

The title compound, C6H8O4NP·H2O, contains one phosphon­ate group and one pyridyl ring connected by a CH(OH) group. The pyridyl N atom and one of the three phospho­nate O atoms are protonated. Extensive hydrogen-bonding interactions, as well as π–π-stacking interactions, are found between the mol­ecules, thus generating a three-dimensional supramolecular network structure.

Treatment of [(L(OEt))(2)Ti(2)(mu-O)(2)(mu-SO(4))] (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)}(3)](-)) with [Ru(H)(Cl)(CO)(PPh(3))(3)] and Ag(OTf) (OTf(-) = triflate) in the presence of Na(2)CO(3) gave the Ti(IV)-Ru(II) complex [(L(OEt))(2)Ti(2)(mu-O)(3)(mu(3)-SO(4))Ru(CO)(PPh(3))(2)] (2) whereas that with [Re(CO)(5)(OTf)] afforded the Ti(IV)-Re(I) complex [H(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))Re(CO)(3)(H(2)O)] (3). The crystal structures of complexes 2.HOTf and [3.2/3(Et(3)NHOTf).5/12(H(2)O)](3) have been determined. Complex 2 consists of an adamantane-like Ti(2)RuSO(6) core, in which the {Ru(II)(PPh(3))(2)(CO)} moiety is facially coordinated to a tridentate-O,O',O''(sulfate) [(L(OEt))(2)Ti(2)(mu-O)(3)(mu(3)-SO(4))](2-) metalloligand. The anion [(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))Re(CO)(3)(H(2)O)](-) in 3 can be viewed as consisting of a fac-{Re(I)(CO)(3)} fragment coordinated with one aqua ligand and a bidentate-O,O'-[(L(OEt))(2)Ti(2)(mu-O)(3)(mu-SO(4))](2-) metalloligand.