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A series of cyclometalated iridium(III) complexes with either 4-(2-pyridyl)-1,2,3-triazole or 1-(2-picolyl)-1,2,3-triazole ancillary ligands to give complexes with either 5- or 6-membered chelate rings were synthesized and characterized by a combination of X-ray crystallography, electron spin ionization-high-resolution mass spectroscopy (ESI-HRMS), and nuclear magnetic resonance (NMR) spectroscopy. The electronic properties of the complexes were probed using absorption and emission spectroscopy, as well as cyclic voltammetry. The relative stability of the complexes formed from each ligand class was measured, and their excited-state properties were compared. The emissive properties are, with the exception of complexes that contain a nitroaromatic substituent, insensitive to functionalization of the ancillary pyridyl-1,2,3-triazole ligand but tuning of the emission maxima was possible by modification of the cyclometalating ligands. It is possible to prepare a wide range of optimally substituted pyridyl-1,2,3-triazoles using copper Cu(I)-catalyzed azide alkyne cycloaddition, which is a commonly used "click" reaction, and this family of ligands represent an useful alternative to bipyridine ligands for the preparation of luminescent iridium(III) complexes. [ABSTRACT FROM AUTHOR]

The reaction of MoVIO2(L-NS2) [L-NS2 = 2,6-bis(2,2-diphenyl-2-thioethyl)pyridinate(2-)] or MoV2O3(L-NS2)2 with excess PPh3 in N,N-dimethylformamide at 70 °C results in the formation of gray-green (L-NOS)MoIV(¼-O)((¼-S)MoIV(L-NS2) [L-NOS = 2(¼(2,2-diphenyl-2-thioethyl)-6-(2,2-diphenyl-2-oxoethyl)pyridinate(2-)] (1). The crystal structure of 1 revealed a dinuclear complex comprised of two trigonal bipyramidal Mo centers bridged along an axial-equatorial edge (the ¼-O-(¼-S vector) such that the MoN bonds are trans to the bridging atoms and are anti with respect to the MoMo bond (d(MoMo) = 2.5535(5) Å); the remaining coordination sites are occupied by the S- and O-donor atoms of the L-NOS and L-NS2 ligands. The diamond core is asymmetric, with Mo(1/2)-O(1) distances of 1.845(2) and 2.009(2) Å and Mo(1/2)-S(1) distances of 2.374(1) and 2.230(1) Å. Compound 1 is unique in possessing a planar, diamond-core unit devoid of terminal oxo ligation and a new tridentate L-NOS ligand formed via a novel intramolecular modification of the original L-NS2 ligand. [ABSTRACT FROM AUTHOR]

The article provides information on a study that reported on the synthesis and characterization of the first molybdenum-copper carbon monoxide dehydrogenase complexes. The study stated that a unique heterobimetallic Mo/Cu active site is present in the carbon monoxide dehydrogenase from Oligotropha carboxidovorans. This enzyme catalyzes the oxidation of carbon oxide and carbon dioxide. Some of the experiments done regarding the paramagnetic active site models indicated that few mechanisms invoke the direct participation of the sulfido ligand in the formation of thiocarbonate intermediates.

Reaction of TpiPrMoVIOS(OAr) with cobaltocene in toluene results in the precipitation of brown, microcrystalline oxosulfido-Mo(V) compounds, [CoCp2][TpiPrMoVOS(OAr)] (Cp- = έ5-C5H5-, TpiPr- = hydrotris(3-isopropylpyrazol-1-yl)borate, OAr- = phenolate or 2-sBu, 2-tBu, 3-tBu, 4-sBu, 4-Ph, 3,5-sBu2, 2-CO2Me, 2-CO2Et or 2-CO2Ph derivative thereof). The compounds are air- and water-sensitive and display ν(Mo-O) and ν(Mo-S) IR absorption bands at ca. 890 and 435 cm-1, respectively, 20-40 cm-1 lower in energy than the corresponding bands in TpiPrMoOS(OAr). They are electrochemically active and exhibit three reversible cyclovoltammetric waves (E(MoVI/MoV) = -0.40 to -0.66 V, E([CoCp2]+/CoCp2) = -0.94 V and E(CoCp2/[CoCp2]-) = -1.88 V vs SCE). Structural characterization of [CoCp2][TpiPrMoOS(OC6H4CO2Et-2)]·2CH2Cl2 revealed a distorted octahedral Mo(V) anion with Mo-O and Mo-S distances of 1.761(5) and 2.215(2) Å, respectively, longer than corresponding distances in related TpiPrMoOS(OAr) compounds. The observation of strong S(1s) → (S(3p) + Mo(4d)) S K-preedge transitions indicative of a d¹ sulfido-Mo(V) moiety and the presence of short Mo-O (ca. 1.72 Å) and Mo-S (ca. 2.25 Å) backscattering contributions in the Mo K-edge EXAFS further support the oxosulfido-Mo(V) formulation. The compounds are EPR-active, exhibiting highly anisotropic (Δg 0.124-0.150), rhombic, frozen-glass spectra with g1 close to the value observed for the free electron (ge = 2.0023). Spectroscopic studies are consistent with the presence of a highly covalent Mo-S π* singly occupied molecular orbital. The compounds are highly reactive, with reactions localized at the terminal sulfido ligand. For example, the compounds react with cyanide and PPh3 to produce thiocyanate and SPPh3, respectively, and various (depending on solvent) oxo-Mo(V) species. Reactions with copper reagents also generally lead to desulfurization and the formation of oxo-Mo(V) or -Mo(IV) complexes. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L¹), that is used as promoter to enhance CuI-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L¹ reveals a dinuclear cation, [Ag2(L¹)2]2+, that is essentially isostructural to the copper(I) analogue. While the [Ag2(L¹)2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L²), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the CuI complex [Cu3I(L²)2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction. [ABSTRACT FROM AUTHOR]

The synthesis of new cage amine macrobicyclic ligands with pendent carboxylate functional groups designed for application in copper radiopharmaceuticals is described. Reaction of [Cu((NH2)2sar)]2+ (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) with either succinic or glutaric anhydride results in selective acylation of the primary amine atoms of [Cu((NH2)2sar)]2+ to give derivatives with either one or two aliphatic carboxylate functional groups separated from the cage amine framework by either a four- or five-atom linker. The CuII serves to protect the secondary amine nitrogen atoms from acylation, and can be removed to give the free ligands. The newly appended carboxylate functional groups can be used as sites of attachment for cancer-targeting peptides such as Lys3-bombesin. The synthesis of the first dimeric sarcophagine-peptide conjugate, possessing two Lys3-bombesin peptides tethered to a single cage amine, is presented. This species has been radiolabeled with copper-64 at ambient temperature and there is minimal dissociation of CuII from the conjugate even after two days of incubation in human serum. [ABSTRACT FROM AUTHOR]

Sky-blue Tp*WOCl2 has been synthesized from the high-yielding reaction of Tp*WO2Cl with boron trichloride in refluxing toluene. Dark-red Tp*WOI2 was prepared via thermal decarbonylation followed by aerial oxidation of Tp*WI(CO)3 in acetonitrile. From these precursors, an extensive series of mononuclear tungstenyl complexes, Tp*WOXY [X = C-, Y = OPh-, SPh-; X = Y = OPh-, 2-(n-propyl)pheno1ate (PP-), SPh-, SePh; XY = toluene-3,4-dithiolate (tdt2-), quinoxaline-2,3-dithiolate (qdt2-), benzene-1,2-diselenolate (bds2-); Tp* = hydrotris(3,5-dimethylpyrazol-l-yl)borate], was prepared by metathesis with the respective alkali-metal salt of X-/XY2- or (NHEt3)2(qdt). The complexes were characterized by microanalysis, mass spectrometry, electrochemistry, IR, electron paramagnetic resonance (EPR), and electronic absorption spectroscopies, and X-ray crystallography (for X Y = OPh-, PP-, SPh-; XY = bds²). The six-coordinate, distorted-octahedral tungsten centers are coordinated by terminal oxo [W≡O = 1.689(6)-1.704(3) Å], tridentate Tp*, and monodentate or bidentate O/S/Se-donor ligands. Spin Hamiltonian parameters derived from the simulation of fluid-solution X-band EPRspectra revealed that the soft-donor S/Se ligand complexes had largerg values and smaller 183W hyperfine coupling constants than the less covalent hard-donor O/Cl species. The former showed low-energy ligand-to-metal charge-transfer bands in the near-IR region of their electronic absorption spectra. These oxotungsten(V) complexes display lower reduction potentials than their molybdenum counterparts, underscoring the preference of tungsten for higher oxidation states. Furthermore, the protonation of the pyrazine nitrogen atoms of the qdt2- ligand has been examined by spectroelectrochemistry; the product of the one-electron reduction of [Tp*WO(qdtH)]+ revealed usually intense low-energy bands. [ABSTRACT FROM AUTHOR]

Green/blue Tp[sup/Pr]rMoO(S[sub2]PR[sub2]) (Tp[sup/Pr] = hydrotris(3-isopropylpyrazolyl)borate; R Pr[supi], Ph, OEt, OPr[supi], (-)-mentholate) complexes were synthesized and characterized by elemental analysis, mass spectrometry, IR and NMR spectroscopy, and X-ray crystallography. The diamagnetic, six-coordinate, oxo-Mo(IV) complexes possess distorted octahedral geometries defined by terminal oxo, bidentate dithio acid, and tridentate Tp ligands. The R = Pr[supi] and Ph derivatives are isomers of previously reported 1,2-borotropically shifted complexes, Tp[sup/Pr*]MoO(S[sub2]PR[sub2]) (Tp[sup/Pr*] = hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate; ref: Inorg. Chem. 1996, 35, 5368). Conversion of Tp[sup/Pr]MoO(S2PPh2) into Tp[sup/Pr*]MoO(S[sub2]PPh[sub2]) at elevated temperatures (>80 °C) showed that the borotropically shifted isomer was thermodynamically more stable than the unshifted species. Reaction with methanol converts Tp[sup/Pr]MoO(S[sub2]PPr[supi][sub2]) into (HB(OMe)(Prsupi]pz)[sub2])MoO(S[sub2]PPr[supi]) (Pr[supi]pz = 3-isopropylpyrazolyl), which was characterized by spectroscopic and crystallographic methods. [ABSTRACT FROM AUTHOR]

Atom transfer reactions have been employed to convert Tp/PrMoO2(OAr) into monomeric cis- oxosulfido-Mo(VI) and dimeric y-disulfido-Mo(V) species, [Tp/PrrMoOS(OAr)]n (Tp/Pr = hydrotris(3-isopropyl- pyrazol-1 -yl)borate; OAr = phenolate or naphtholate derivative; n = 1 and 2, respectively). Dark red, monomeric Tp/PrMoOS(OAr) complexes contain distorted octahedral cis-oxosulfido-Mo(VI) centers, with d(Mo=O) = 1.692(5) Å, d(Mo=S) = 2.132(2) Å, and ∠(O=Mo=S) = 103.68(16)° for the 2-sec-butylphenolate derivative. Dark red-purple, dimeric [Tp/PrMoOS(OAr)]2 complexes undergo S–S bond cleavage forming monomeric oxosulfido-Mo(VI) species in solution. In the solid state, the 3,5-di-tert- butylphenolate derivative exhibits a centrosymmetric structure, with distorted octahedral anti oxo-Mo(V) centers bridged by a disulfido-κS,κS' ligand. Hydrolysis of the oxosulfido-Mo(VI) complexes results in the formation of [Tp/PrMoO]2(μ-S2)(μ-O). In anaerobic solutions, certain oxosulfido-Mo(Vl) complexes convert to molybdenyl complexes bearing bidentate 2-mercaptophenolate or related naphtholate ligands formed via intramolecular attack of the sulfido ligand on a coligand C-H group. The oxosulfido-Mo(Vl) complexes serve as precursors to biologically relevant Mo(V) and heterobimetallic MoO(μ-S)Cu species and undergo a range of biomimetic reactions. [ABSTRACT FROM AUTHOR]

The first member of a water-soluble family of bis(thiosemiCarbazone) ligands is reported. It forms a 1:1 complex with Zn" that absorbs intensely in the visible region (λmax) = 414 nm; ϵ 1.8(4) x M-1 cm-1; pH 7.3). Its affinity for Znll (KD = 5.9(3) x 10-9 M at pH 7.3) was determined by competition with ligand ethylene glycol O,σ-bis(2-aminoelhyl)-N,N,M,N'-tetraacetic acid. Its potential application as a chromophoric probe was demonstrated by estimation of the Znll binding affinities of the soluble metal-binding domains of two plant metal-transporting proteins. [ABSTRACT FROM AUTHOR]