Diverse Co(II) Coordination Polymers with the Same Mixed Ligands: Evaluation of Chemical Stability and Structural Transformation.

Reactions of Co(OAc)2·4H2O, N'N'-bis(3-pyridylmethyl)oxalamide (L) and 4,4'-sulfonyldibenzoic acid (H2SDA) afforded four coordination polymers with the same mixed ligands, {[Co(L)(SDA)(H2O)2]·H2O·CH3OH}n, 1, {[Co(L)0.5(SDA)]·2H2O·0.5L}n, 2, {[Co(L)1.5(SDA)(H2O)]·H2O}n, 3, and {[Co2(L)1.5(SDA)2(H2O)2]·4H2O}n, 4, which have been structurally characterized using single-crystal X-ray crystallography. Complexes 1-4 are 2D layers, revealing topologies of sql, 2,6L1, (4,4)Ia, and 6L12, respectively, and demonstrating that the metal-to-ligand ratio, solvent system, and reaction temperature are important in determining the structural diversity. The immersion of these complexes into various solvents shows that the structural types govern the chemical stabilities of 1-4. Reversible structural transformation is shown for complexes 1 and 2 upon solvent removal and adsorption, while those of 3 and 4 are irreversible.

Cu(II) Coordination Polymers Containing Mixed Ligands with Different Flexibilities: Structural Diversity and Iodine Adsorption.

Reactions of N,N'-bis(3-methylpyridyl)oxalamide (L1), N,N'-bis(3-methylpyridyl)adipoamide (L2) and N,N'-bis(3-methylpyridyl)sebacoamide (L3) with tricarboxylic acids and Cu(II) salts afforded {[Cu(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 1, {[Cu1.5(L2)1.5(1,3,5-BTC)(H2O)2]·6.5H2O}n, 2, [Cu(L2)0.5(1,3,5-HBTB)]n (1,3,5-H3BTB = 1,3,5-tri(4-carboxyphenyl)benzene), 3, [Cu4(L3)(OH)2(1,3,5-BTC)2]n, 4, {[Cu3(L3)2(1,3,5-BTB)2]·2.5MeOH·2H2O}n, 5, and {[Cu3(L3)2(1,3,5-BTB)2 ]·DMF·2H2O}n, 6, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1-4 form a 2D layer with the {44.62}-sql topology, a 2D layer with the (4.62)2(42.62.82)-bex topology, a three-fold interpenetrated 3D net with the (412·63)-pcu topology and a 3D framework with the (410·632·83)(42·6)2(43·63) topology, respectively, whereas 5 and 6 are 3D frameworks with the (63)2(64·82)(68·85·102) topology. Complex 5 shows a better iodine adsorption factor of 290.0 mg g-1 at 60 °C for 360 min than the other ones, revealing that the flexibility of the spacer ligand governs the structural diversity and the adsorption capacity.

Ligand effect of cyclometallated iridium(iii) complexes on N-alkylation of amines in hydrogen borrowing reactions.

Dinuclear iridium complexes with the general formula (C^N)2Ir(µ-Cl)2Ir(C^N)2 (C^N = bidentate ligand with carbon and nitrogen donor atoms) were prepared and used in catalytic systems for N-alkylation of amines through the hydrogen borrowing pathway. Triphenylphosphine derivatives were used as auxiliary in catalytic systems to provide excellent conversion of amines to N-alkylation products in yields ranging from 57% to 100%. The catalytic ability of the catalyst depends on the structure of its coordination ligands, including bidentate ligands (C^N) and triphenylphosphine derivatives. These catalytic systems adopt an environmentally friendly and sustainable reaction process through a hydrogen self-transfer strategy, using readily available alcohols as alkylating agents without the need for bases, solvents, and other additives, showing potential in the synthetic and pharmaceutical industries.

Metal and Ligand Effect on the Structural Diversity of Divalent Coordination Polymers with Mixed Ligands: Evaluation for Photodegradation.

Eight coordination polymers constructed from divalent metal salts, N,N'-bis(pyridin-3-ylmethyl)terephthalamide (L), and various dicarboxylic acids are reported, affording [Co(L)(5-ter-IPA)(H2O)2]n (5-tert-H2IPA = 5-tert-butylisophthalic acid), 1, {[Co(L)(5-NO2-IPA)]⋅2H2O}n (5-NO2-H2IPA = 5-nitroisophthalic acid), 2, {[Co(L)0.5(5-NH2-IPA)]⋅MeOH}n (5-NH2-H2IPA = 5-aminoisophthalic acid), 3, {[Co(L)(MBA)]⋅2H2O}n (H2MBA = diphenylmethane-4,4'-dicarboxylic acid), 4, {[Co(L)(SDA)]⋅H2O}n (H2SDA = 4,4-sulfonyldibenzoic acid), 5, {[Co2(L)2(1,4-NDC)2(H2O)2]⋅5H2O}n (1,4-H2NDC = naphthalene-1,4-dicarboxylic acid), 6, {[Cd(L)(1,4-NDC)(H2O)]⋅2H2O}n, 7, and {[Zn2(L)2(1,4-NDC)2]⋅2H2O}n, 8, which were structurally characterized by using single-crystal X-ray diffraction. The structural types of 1-8 are subject to the metal and ligand identities, showing a 2D layer with the hcb, a 3D framework with the pcu, a 2D layer with the sql, a polycatenation of 2-fold interpenetrated 2D layer with the sql, a 2-fold interpenetrated 2D layer with the 2,6L1, a 3D framework with the cds, a 2D layer with the 2,4L1, and a 2D layer with the (102⋅12)(10)2(4⋅10⋅124)(4) topologies, respectively. The investigation on the photodegradation of methylene blue (MB) by using complexes 1-3 reveals that the degradation efficiency may increase with increasing surface areas.

Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing.

Hg(II) halide complexes [HgCl2] 2L1 [L1 = N,N'-bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide), 1, [HgBr2(L1)]n, 2, [HgI2(L1)], 3, [Hg2X4(L2)2] [X = Cl, 4, Br, 5, and I, 6; L2 = N,N'-bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide] and {[HgX2(L3)]⋅H2O}n [X = Cl, 7, Br, 8 and I, 9; L3 = 4,4'-oxybis(N-(pyridine-3-yl)benzamide)] are reported and structurally characterized using single-crystal X-ray diffraction analyses. The linear HgCl2 units of complex 1 are interlinked by the L1 ligands through Hg---N and Hg---O interactions, resulting in 1D supramolecular chains. Complex 2 shows 1D zigzag chains interlinked through the Br---Br interactions to form 1D looped supramolecular chains, while the mononuclear [HgI2L2] molecules of 3 are interlinked through Hg---O and I---I interactions, forming 2D supramolecular layers. Complexes 4-6 are isomorphous dinuclear metallocycles, and 7-9 form isomorphous 1D zigzag chains. The roles of the ligand type and the halide anion in determining the structural diversity of 1-9 is discussed and the luminescent properties of 7-9 evaluated. Complexes 7-9 manifest stability in aqueous environments. Moreover, complexes 7 and 8 show good sensing towards Fe3+ ions with low detection limits and good reusability up to five cycles, revealing that the Hg-X---Fe3+ (X = Cl and Br) interaction may have an important role in determining the quenching effect of 7 and 8.

Nickel(II) Coordination Polymers Supported by Bis-pyridyl-bis-amide and Angular Dicarboxylate Ligands: Role of Ligand Flexibility in Iodine Adsorption.

Reactions of N'N'-bis(3-pyridylmethyl)oxalamide (L1), N'N'-bis(4-pyridylmethyl)oxalamide (L2), or N,N'-bis(3-pyridylmethyl)adipoamide) (L3) with angular dicarboxylic acids and Ni(II) salts under hydro(solvo)thermal conditions afforded a series of coordination polymers: {[Ni(L1)(OBA)(H2O)]·H2O}n (H2OBA = 4,4-oxydibenzoic acid), 1, {[Ni(L1)(SDA)(H2O)2]·H2O·CH3OH}n (H2SDA = 4,4-sulfonyldibenzoic acid), 2, {[Ni(L2)(OBA)]·C2H5OH}n, 3, {[Ni(L2)(OBA)]·CH3OH}n, 4, {[Ni2(L2)(SDA)2(H2O)3]·5H2O}n, 5, {[Ni2(L2)(SDA)2(H2O)3]·H2O·2C2H5OH}n, 6, {[Ni(L3)(OBA)(H2O)2]·2H2O}n, 7, {[Ni(L3)(SDA)(H2O)2]·2H2O}n, 8, and {[Ni(L3)0.5(SDA)(H2O)2]·0.5C2H5OH}n, 9, which have been structurally characterized by using single-crystal X-ray crystallography. Complex 1 exhibits an interdigitated 2D layer with the 2,4L2 topology and 2 is a 2D layer with the sql topology, while 3 and 4 are 3D frameworks resulting from polycatenated 2D nets with the sql topology and 5 and 6 are 2-fold interpenetrated 3D frameworks with the dia topology. Complexes 7 and 8 are 1D looped chains and 9 is a 2D layer with the 3,4L13 topology. The various structural types in 1-9 indicate that the structural diversity is subject to the flexibility and donor atom position of the neutral spacer ligands and the identity of the angular dicarboxylate ligands, while the role of the solvent is uncertain. The iodine adsorption of 1-9 was also investigated, demonstrating that that the flexibility of the spacer L1-L3 ligands can be an important factor that governs the feasibility of the iodine adsorption. Moreover, complex 9 shows a better iodine adsorption and encapsulates 166.55 mg g-1 iodine in the vapor phase at 60 °C, which corresponded to 0.38 molecules of iodine per formula unit.

Eight-Fold Interpenetrating Diamondoid Coordination Polymers for Sensing Volatile Organic Compounds and Metal Ions.

Reactions of divalent metal salts with 4,4-oxybis(N-(pyridine-4-yl)-benzamide), L, and naphthalene-1,4-dicarboxylic acid (1,4-H2NDC) in various solvents gave [Zn(L)(1,4-NDC)·H2O]n, 1, [Cd(L)(1,4-NDC)(H2O)·MeOH]n, 2, and [Co(L)(1,4-NDC)(H2O)0.5·MeOH]n, 3, which have been structurally characterized. Complexes 1-3 show eight-fold interpenetrating frameworks with the dia topology, which exhibit porosities substantiated by CO2 adsorption, whereas 1 and 2 manifest stability in aqueous environments and show high selectivity toward sensing of mesitylene molecules and Fe3+ ions with low detection limits and good reusability up to five cycles.

Impact of Isomeric Dicarboxylate Ligands on the Formation of One-Dimensional Coordination Polymers and Metallocycles: A Novel cis→trans Isomerization.

A series of Co(II), Ni(II) and Cu(II) coordination polymers and dinuclear metallocycles containing 4-aminopyridine (4-ampy) and benzenedicarboxylate ligands, {[M(4-ampy)2(1,4-BDC)]·H2O·CH3CH2OH}n (M = Ni, 1a; Co, 1b, 1,4-H2BDC = benzene-1,4-dicarboxylic acid), {[Ni2(4-ampy)4(1,3-BDC)2]·H2O·CH3CH2OH}n (1,3-H2BDC = benzene-1,3-dicarboxylic acid), 2, [M2(4-ampy)4(1,2-BDC)2] (M = Ni, 3a; Co, 3b, 1,2-H2BDC = benzene-1,2-dicarboxylic acid), [Co(4-ampy)2(1,3-BDC)]n, 4, {[Cu(4-ampy)2(1,4-BDC)] CH3CH2OH}n, 5a, and {[Cu(4-ampy)2(1,4-BDC)]·H2O}n, 5b·H2O, are reported, which were hydrothermally prepared and structurally characterized by using single crystal X-ray diffraction. Complexes 1a and 1b are isomorphous 1D zigzag chains, while 2 displays a concave-convex chain and 3a and 3b are dinuclear metallocycles that differ in the boding modes of the 1,2-BDC2- ligands, forming a 3D and a 2D supramolecular structures with the pcu and sql topologies, respectively. Complex 4 exhibit a 1D helical chain and complexes 5a and 5b·H2O are 1D linear and zigzag chains, in which the Cu2-1,4-BDC2- units adopt the cis and trans configurations, respectively. A novel irreversible structural transformation due to cis→trans isomerization of the Cu2-1,4-BDC2- units was observed in 5b⋅H2O and 5a upon water adsorption of the desolvated product of 5b·H2O.

A reduced graphene oxide-supported iridium nanocatalyst for selective transformation of alcohols into carbonyl compounds via a green process.

A nanocatalyst constructed from reduced graphene oxide and iridium atoms (RGOIrNc) showed high selectivity (99%-100%) and reliability for the transformation of aromatic alcohols into carbonyl compounds via ultrasonication without using harmful chemicals and solvents. Experimental data including Fourier transform infrared spectroscopy, x-ray diffraction, spherical-aberration-corrected field emission transmission electron microscopy and Raman spectra confirmed the nanostructure of the RGOIrNc. Noticeably, the structural characteristics of this catalyst remained unchanged within 25 catalytic cycles and the activity and selectivity for the transformation of benzylic alcohols showed good stability. The average turnover frequency is greater than 9000 h-1, the total turnover number is more than 150 000 after 25 catalytic cycles and the productivity of carbonyl compounds reaches 376 048 [Formula: see text], indicating that RGOIrNc catalyst has good durability and stability and high 'greenness'.

A Pair of CoII Supramolecular Isomers Based on Flexible Bis-Pyridyl-Bis-Amide and Angular Dicarboxylate Ligands.

Thermal reactions of cobalt(II) salts with flexible N,N'-bis(pyrid-3-ylmethyl)adipoamide (L) and angular 4,4'-sulfonyldibenzoic acid (H2SDA) in H2O and CH3OH afforded a pair of supramolecular isomers: [Co2(L)(SDA)2], 1, and [Co2(L)(SDA)2]⋅CH3OH⋅H2O, 2. The structure of complex 1 can be simplified as a one-dimensional (1D) looped chain with L ligands penetrating into the middles of squares, forming a new type of self-catenated net with the (42⋅54)(4)2(5)2 topology, whereas complex 2 displays a 2-fold interpenetrated 2D net with the rare (42⋅68⋅8⋅104)(4)2-2,6L1 topology. While both complexes 1 and 2 display antiferromagnetism with strong spin-orbital coupling, the antiferromagnetism of 2 is accompanied by a cross-over behavior and probably a spin canting phenomenon.

Graphene oxide-iridium nanocatalyst for the transformation of benzylic alcohols into carbonyl compounds.

A catalyst constructed from graphene oxide and iridium chloride exhibited high activity and reliability for the selective transformation of benzylic alcohols into aromatic aldehydes or ketones. Instead of thermal reaction, the transformation was performed under ultrasonication, a green process with low byproduct, high atomic yield and high selectivity. Experimental data obtained from spherical-aberration corrected field emission TEM (ULTRA-HRTEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy and Raman spectra confirm the nanostructure of the title complex. Noticeably, the activity and selectivity for the transformation of benzylic alcohols remained unchanged within 25 catalytic cycles. The average turn over frequency is higher than 5000 h-1, while the total turnover number (TON) is more than one hundred thousand, making it a high greenness and eco-friendly process for alcohol oxidation.

One-Dimensional Mercury Halide Coordination Polymers Based on A Semi-Rigid N-Donor Ligand: Reversible Structural Transformation.

Four one-dimensional (1D) mercury(II) halide coordination polymers have been synthesized by using a semi-rigid N-donor ligand, 2,2'-(1,4-phenylene)-bis(N-(pyridin-3-yl)acetamide) (1,4-pbpa). While [Hg(1,4-pbpa)Cl2·CH3OH]n, 1, forms a sinusoidal chain, the complexes [Hg(1,4-pbpa)X2]n (X = Cl, 2; Br, 3; I, 4) are helical. The sinusoidal 1 undergoes reversible structural transformation with helical 2 upon removal and uptake of CH3OH, which was accompanied with the conformation adjustment of the 1,4-pbpa ligand from trans anti-anti to trans syn-anti. Pyridyl ring rotation of the 1,4-pbpa ligand that results in the change of the ligand conformation is proposed for the initiation of the structural transformation.

Mg(II) Coordination Polymers Based on Flexible Isomeric Tetracarboxylate Ligands: Syntheses, Structures, Structural Transformation and Luminescent Properties.

By using a new flexible tetracarboxylic acid, bis(3,5-dicarboxyphenyl) adipoamide, H4L¹, and its isomer, bis(2,5-dicarboxyphenyl)adipoamide, H4L², three Mg(II) coordination polymers, {[Mg2(L¹)(H2O)2]·2EtOH·3H2O}n, 1, [Mg2(L¹)(H2O)8]n, 2, and {[Mg2(L²)(H2O)6]·H2O}n, 3, have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 are the solvent ratio-dependent hydrothermally stable products. The tetracarboxylate ligand of complex 1 connects eight Mg(II) ions through nine oxygen atoms, resulting in a three-dimensional (3D) 5-connected uninodal net with a rare non-interpenetrating (44.66)-pcu-5-Pmna topology, whereas those of 2 and 3 link four Mg(II) ions through four oxygen atoms and six Mg(II) ions through six oxygen atoms, forming a 1D linear chain and a 3,6-connected 2-nodal 3D net having {4.6²}2{4².610.8³}-rtl topology, respectively. Complex 1 shows a series of structural transformations on heating to 200 °C and almost reversible structural transformation when the activated products were immersed in a mixture of ethanol and water or on hydrothermal. Likewise, complex 2 exhibits a reversible structural transformation on heating/hydrothermal, while 3 exhibits irreversible structural transformations. All three complexes exhibit blue light emissions, with that of complex 3 being much more intense.

Metal and Ligand Effects on the Construction of Divalent Coordination Polymers Based on bis-Pyridyl-bis-amide and Polycarboxylate Ligands.

Ten coordination polymers constructed from divalent metal salts, polycarboxylic acids, and bis-pyridyl-bis-amide ligands with different donor atom positions and flexibility are reported. They were structurally characterized by single-crystal X-ray diffraction. The ten coordination polymers are as follows: (1) {[Ni(L¹)(3,5-PDA)(H2O)3]·2H2O}n (L¹ = N,N'-di(3-pyridyl)suberoamide, 3,5-H2PDA = 3,5-pyridinedicarboxylic acid); (2) {[Ni2(L¹)2(1,3,5-HBTC)2(H2O)4]·H2O}n (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid); (3) {[Ni(L²)(5-tert-IPA)(H2O)2]·2H2O}n (L² = N,N'-di(3-pyridyl)adipoamide, 5-tert-H2IPA = 5-tert-butylisophthalic acid); (4) [Ni(L³)1.5(5-tert-IPA)]n (L³ = N,N'-di(4-pyridyl)adipoamide); (5) [Co(L¹)(1,3,5-HBTC)(H2O)]n; (6) {[Co3(L¹)3(1,3,5-BTC)2(H2O)2]·6H2O}n; (7) [Cu(L4)(AIPA)]n (L4 = N,N'-bis(3-pyridinyl)terephthalamide, H2AIPA = 5-acetamido isophthalic acid); (8) {[Cu(L²)0.5(AIPA)]·MeOH}n; (9) {[Zn(L4)(AIPA)]·2H2O}n; and (10) {[Zn(L²)(AIPA)]·2H2O}n. Complex 1 forms a 1D chain and 2 is a two-fold interpenetrated 2D layer with the sql topology, while 3 is a 2D layer with the hcp topology and 4 shows a self-catenated 3D framework with the rare (4²·67·8)-hxg-d-5-C2/c topology. Different Co/1,3,5-H3BTC ratios were used to prepare 5 and 6, affording a 2D layer with the sql topology and a 2D layer with the (4·85)2(4)2(8³)2(8) topology that can be further simplified to an hcp topology. While complex 7 is a 2D layer with the (4²·67·8)(4²·6)-3,5L2 topology and 8 is a 2-fold interpenetrated 3D framework with the pcu topology, complexes 9 and 10 are self-catenated 3D frameworks with the (424·64)-8T2 and the (44·610·8)-mab topologies, respectively. The effects of the identity of the metal center, the ligand isomerism, and the flexibility of the spacer ligands on the structural diversity of these divalent coordination polymers are discussed. The luminescent properties of 9 and 10 and their photocatalytic effects on the degradation of dyes are also investigated.

Hg(II) Coordination Polymers Based on N,N'-bis(pyridine-4-yl)formamidine.

Reactions of N,N'-bis(pyridine-4-yl)formamidine (4-Hpyf) with HgX2 (X = Cl, Br, and I) afforded the formamidinate complex {[Hg(4-pyf)2]·(THF)}n, 1, and the formamidine complexes {[HgX2(4-Hpyf)]·(MeCN)}n (X = Br, 2; I, 3), which have been structurally characterized by X-ray crystallography. Complex 1 is a 2D layer with the {44·6²}-sql topology and complexes 2 and 3 are helical chains. While the helical chains of 2 are linked through N⁻H···Br hydrogen bonds, those of 3 are linked through self-complementary double N⁻H···N hydrogen bonds, resulting in 2D supramolecular structures. The 4-pyf- ligands of 1 coordinate to the Hg(II) ions through one pyridyl and one adjacent amine nitrogen atoms and the 4-Hpyf ligands of 2 and 3 coordinate to the Hg(II) ions through two pyridyl nitrogen atoms, resulting in new bidentate binding modes. Complexes 1⁻3 provide a unique opportunity to envisage the effect of the halide anions of the starting Hg(II) salts on folding and unfolding the Hg(II) coordination polymers. Density function theory (DFT) calculation indicates that the emission of 1 is due to intraligand π→π * charge transfer between two different 4-pyf- ligands, whereas those of 2 and 3 can be ascribed to the charge transfer from non-bonding p-type orbitals of the halide anions to π * orbitals of the 4-pyf- ligands (n→π *). The gas sorption properties of the desolvated product of 1 are compared with the Cu analogues to show that the nature of the counteranion and the solvent-accessible volume are important in determining their adsorption capability.

N,N'-Bis(pyridin-3-yl)oxamide.

The title mol-ecule, C12H10N4O2, located about an inversion centre, is roughly planar, with an r.m.s. deviation from the least-squares plane of all non-H atoms of 0.019 Å. In the crystal, N-H⋯N hydrogen bonds between the amide N-H group and the pyridine N atom connect the mol-ecules into a corrugated layer parallel to (10-1).

Methyl 4-[N-(5-bromo-pyrimidin-2-yl)carbamo-yl]benzoate.

In the title compound, C(13)H(10)BrN(3)O(3), the pyrimidine and benzene rings are twisted with an inter-planar angle of 58.4 (1)°. The secondary amide group adopts a cis conformation with an H-N-C-O torsion angle of 14.8 (1)°. In the crystal, mol-ecules are connected into inversion dimers via pairs of N-H⋯N hydrogen bonds, generating an R(2) (2)(8) motif. The dimers are further connected through a C-Br⋯O inter-action [3.136 (1) Šand 169.31 (1)°] into a chain along [110]. Weak C-H⋯N hydrogen bonds between the methyl benzoate groups and pyrimidine rings are also observed in the crystal structure.

Methyl 4-[(5-chloro-pyrimidin-2-yl)carbamo-yl]benzoate.

Mol-ecules of the title compound, C(13)H(10)ClN(3)O(3), form centrosymmetric dimers via inter-molecular N-H⋯N hydrogen bonds generating an R(2) (2)(8) motif. The dimers are further connected through an O⋯Cl-C halogen bond [O⋯Cl = 3.233 (1) Šand O⋯Cl-C = 167.33 (1)°] into a chain along [110]. The secondary amide group adopts a cis conformation. Weak C-H⋯N hydrogen bonds among the methyl benzoate and pyrimidyl rings are also observed in the crystal structure.

Methyl 4-[(pyrimidin-2-yl)carbamo-yl]benzoate.

Mol-ecules of the title compound, C(13)H(11)N(3)O(3), are connected into centrosymmetric dimers via inter-molecular N-H⋯N hydrogen bonds, generating an R(2) (2)(8) motif. The pyrimidine and the phenyl rings are twisted with respect to each other by an inter-planar angle of 61.3 (1)°.

Water attack umpolung aromatic systems to release hydrogen.

The synthesis and structures of a series of cyclometalated iridium(III) complexes based on benzoxazole derivatives and triphenylphospine are reported. These complexes have a general formula (C^N)(2)Ir(Cl)(pph(3)) [where C^N is a monoanionic cyclometalating ligand, dfpbo = (difluorophenyl)benzoxazolato, pbo = 2-phenylbenzoxazolato, nbo = 2-(2-naphthyl)benzoxazolato, and pph(3) is a triphenylphospine ligand]. The complexes (dfpbo)(2)Ir(Cl)(pph(3)) (2a), (pbo)(2)Ir(Cl)(pph(3)) (2b), and (nbo)(2)Ir (Cl)(pph(3)) (2c) have been structurally characterized by X-ray crystallography. Complex 2a shows facile umpolung in the phenyl rings of the arylphosphine ligand and displays a catalytic propensity for water splitting.