Cd(II) complexes with N8 and N4O4 donor macrocyclic ligands

The coordination capability of the octaaza 24-membered (L¹) and the tetraoxotetraaza 28-membered (L²) macrocycle ligands - with different sizes, nature and number of the donor atoms - has been investigated with nitrate and perchlorate Cd(II) salts. The complexes were prepared in 1:1 and 2:1 Cd:L molar ratio. The characterization by elemental analysis, IR, LSI mass spectrometry, conductivity measurements and ¹H NMR spectroscopy, together with the crystal structure of the complexes [CdL¹](NO₃)₂ · 0.5H₂O, [CdL¹](ClO₄)₂ and [CdL²(CH₃CN)₂](ClO₄)₂ · CH₃CN · H₂O confirms the formation of mononuclear complexes in all cases. The [CdL¹](NO₃)₂ · 0.5H₂O and [CdL¹](ClO₄)₂ present a mononuclear endomacrocyclic structure with the metal ion coordinated by the eight donor nitrogen atoms from the macrocyclic backbone in a square antiprism geometry. The complex [CdL²(CH₃CN)₂](ClO₄)₂ · CH₃CN · H₂O is also mononuclear, but the cadmium ion is in an octahedral environment coordinated by four amine nitrogen atoms from the macrocyclic framework and two nitrogen atoms from two acetonitrile molecules. The ether oxygen atoms from the ligand are not coordinated.     

Sn-S and Ru-Ru bonds cleavage reactions between [Ph3SnS(CH2)3SSnPh3] and Ru3(CO)12: X-ray crystal structures of [Ph3SnS(CH2)3SSnPh3] and trans-[Ru(CO)4(SnPh3)2]

The organotin complex [Ph₃SnS(CH₂)₃SSnPh₃] (1) was synthesized by PdCl₂ catalyzed reaction between Ph₃SnCl and disodium-1,3-propanedithiolate which in turn was prepared from 1,2-propanedithiol and sodium in refluxing THF. Reaction of 1 with Ru₃(CO)₁₂ in refluxing THF affords the mononuclear complex trans-[Ru(CO)₄(SnPh₃)₂] (2) and the dinuclear complex [Ru₂(CO)₆(μ-κ²-SCH₂CH₂CH₂S)] (3) in 20 and 11% yields, respectively, formed by cleavage of Sn-S bond of the ligand and Ru-Ru bonds of the cluster. Treatment of pymSSnPPh₃ (pymS = pyrimidine-2-thiolate) with Ru₃(CO)₁₂ at 55-60 °C also gives 2 in 38% yield. Both 1 and 2 have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

Synthesis, crystal structure and DNA interaction studies on mononuclear zinc complexes

A new family of mononuclear Zn(II) complexes [Zn(Pyimpy)₂](ClO₄)₂ (1), [Zn(Pyimpy)(Cl)₂] (2), [Zn(Pyimpy)(SCN)₂] (3) and [Zn(Pyimpy)(N₃)₂] (4) were synthesized using designed tridentate ligand Pyimpy having NNN donors (Pyimpy: (2-((2-phenyl-2-(pyridin-2-l)hydazono)methyl)pyridine)). Complexes were characterized by different spectroscopic studies and it has been found out that all complexes exhibited strong fluorescent emission at room temperature. Molecular structures of [Zn(Pyimpy)₂](ClO₄)₂·C₆H₅CH₃·0.5H₂O (1·C₆H₅CH₃·0.5H₂O) and [Zn(Pyimpy)(Cl)₂]·CH₃CN (2·CH₃CN) were determined by X-ray crystallography and ligand coordinated Zn(II) ions was described as distorted octahedral and distorted square pyramidal, respectively. DNA binding properties of these complexes were investigated by absorption spectral, fluorescence quenching and circular dichroism spectral studies.     

Syntheses and structures of the heterometallic clusters [(Ph3PAu)3Re(CO)4], [(Ph3PAu)4Re(CO)4], [(Ph3PAu)6AuRe2(CO)8], and [(Ph3PAu)6Re(CO)3]

The reaction of [HRe₃(CO)₁₂]²⁻ with an excess of Ph₃PAuCl in CH₂Cl₂ yields [(Ph₃PAu)₄Re(CO)₄]⁺ as the main product, which crystallizes as [(Ph₃PAu)₄Re(CO)₄]PF₆ · CH₂Cl₂ (1 · CH₂Cl₂) after the addition of KPF₆.The crystal structure determination reveals a trigonal bipyramidal Au₄Re cluster with the Re atom in equatorial position.If [(Ph₃PAu)₄Re(CO)₄]⁺ is reacted with PPh₄Cl, a cation [Ph₃PAu]⁺ is eliminated as Ph₃PAuCl, and the neutral cluster [(Ph₃PAu)₃Re(CO)₄] (2) is formed.It combines with excess [(Ph₃PAu)₄Re(CO)₄]⁺ to afford the cluster cation, [(Ph₃PAu)₆AuRe₂(CO)₈]⁺. It crystallizes from CH₂Cl₂ as[(Ph₃PAu)₆AuRe₂(CO)₈]PF₆ · 4CH₂Cl₂ (3 · 4CH₂Cl₂). In [(Ph₃PAu)₃Re(CO)₄] the metal atoms are arranged in form of a lozenge while in [(Ph₃PAu)₆AuRe₂(CO)₈]⁺ two Au₄Re trigonal bipyramids are connected by a common axial Au atom.The treatment of [(Ph₃PAu)₄Re(CO)₄]⁺ with KOH and Ph₃PAuCl in methanol yields the cluster cation [(Ph₃PAu)₆Re(CO)₃]⁺, which crystallizes with from CH₂Cl₂ as [(Ph₃PAu)₆Re(CO)₃]PF₆ · CH₂Cl₂ (4 · CH₂Cl₂). The metal atoms in this cluster form a pentagonal bipyramid with the Re atom in the axial position.     

Structure of binuclear Rh(II) carboxylato complexes with 2,2-bipyridine and an unprecedented rhodium wire with Rh4 core

Structures of rhodium(II) binuclear complexes [Rh₂(OOCCH₃)₂(bpy)₂(H₂O){(CH₃)₂CHOH}][B(C₆H₅)₄]₂ · H₂O (1), [Rh₂Cl₂(OOCCH₃)₂(bpy)₂] · 2H₂O (2), [Rh₂Br₂(OOCCH₃)₂(bpy)₂] · 3H₂O (3), and [Rh₂I₂(OOCCH₃)₂(bpy)₂] (4), as well as an unprecedented wire with infinite Rh-Rh chain, {[Rh₄(μ-OOCH)₄(bpy)₄](BF₄)}_n · 0.5nC₄H₈O₂ (5), have been determined and discussed. Mass spectra of complexes [Rh₂(OOCMe)₂(bpy)₂(H₂O)₂](MeCOO)₂ and [Rh₂(OOCMe)₂(phen)₂(H₂O)₂](MeCOO)₂ have showed stability of polynuclear cations with rhodium in oxidation states in the range +1.25 to +1.75.     

Synthesis, characterization and electrocatalysis of diiron propanediselenolate derivatives as the active site models of [FeFe]-hydrogenases

As an extension of our study on the H-cluster model compounds, a series of diiron propanediselenolate (PDS)-type models have been successfully synthesized. Reaction of diselenol HSe(CH₂)₃SeH with Fe₃(CO)₁₂ in THF (tetrahydrofuran) at reflux gave the parent model compound [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₆ (1) in 48% yield. Further reaction of 1 with PPh₃ or PPh₂H in the presence of Me₃NO in MeCN at room temperature afforded the phosphine-monosubstituted model compounds [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₅(L) (2, L = PPh₃; 3, L = PPh₂H) in 76% and 68% yields, respectively. Similarly, the N-heterocyclic carbene I_Mes-monosubstituted model compound [μ-Se(CH₂)₃Se-μ]Fe₂(CO)₅(I_Mes) (4) could be prepared in 46% yield by reaction of imidazolium salt I_Mes · HCl with n-BuLi followed by treatment of the resulting I_Mes ligand with 1 in THF at room temperature. Compounds 1-4 were fully characterized by elemental analysis and various spectroscopic methods. While the structures of 1-4 were further confirmed by X-ray crystallography, the comparative study of 1 and its analog [μ-S(CH₂)₃S-μ]Fe₂(CO)₆ demonstrates that 1 is a better catalyst for TsOH proton reduction to hydrogen under electrochemical conditions.     

Iron(III), nickel(II) and cadmium(II) complexes of triazamacrocyclic ligand with pendant nitrile groups 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane: Synthesis, structural characteristics and artificial nuclease activity

Three novel transition metal complexes with 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane (L) were synthesized and structurally characterized. In complex [FeLCl₃]·2H₂O (1), three N-donors from the macrocyclic backbone and three chloride anions complete the coordination polyhedron around Fe(III) and lead to a neutral [FeLCl₃] unit. The neutral Fe(III) units of the same chirality are linked through weak interactions into 3D supramolecular network with hexagonal channels. Guest water molecules trapped inside the channel are associated into an unprecedented 1D linear chain. The crystal structures of complexes [NiL(CH₃CN)₃](ClO₄)₂·0.5H₂O (2) and [CdL(CH₃CN)₃](ClO₄)₂·0.5H₂O (3) reveal that the metal center lies in a distorted octahedral N6 environment with three acetonitrile occupying the remaining coordination sites opposite to the macrocyclic ring. The artificial nuclease activity of redox-active complex 1 towards pMD-AMT plasmid DNA was assessed by gel electrophoresis. As a result, complex 1 can effectively cleave supercoiled DNA under near physiological conditions with/without H₂O₂ in a time- and complex concentration-dependent manner.     

Syntheses, structures, and magnetic properties of three Fe(II) complexes with reduced radical ligands

Three new Fe(II) complexes [Fe(HIM2py)₂(SCN)₂] (1), [Fe(HIM2py)₂(H₂O)₂](ClO₄)₂ · 2H₂O (2), and [Fe(HIM2py)₂(4,4-bipy)](ClO₄)₂ · 3CH₃CH₂OH (3) (4,4-bipy = 4,4′-bipyridine, HIM2py = 1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole) have been synthesized and characterized structurally as well as magnetically. The X-ray analysis reveals that HIM2py ligands are coordinated to the metal ions as an unusual six-membered didentate chelate with the κ²N(py), O(HIM) mode. Fe(II) ions in complex 3 are bridged by 4,4-bipy, leading to a 1D chain structure. The magnetic behavior of complex 3 is investigated, showing weak antiferromagnetic interactions.     

Two forms of a copper(II) complex of 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole: a six-coordinate monomer versus a five-coordinate polymer

The reaction of the new bidirectional ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (pyppt) with Cu(ClO₄)₂ · 6H₂O in a 2:1 molar ratio in EtOH affords the complex [Cu^II(pyppt)₂(ClO₄)₂] · H₂O (1) as a microcrystalline turquoise solid. Recrystallisation of complex 1 from MeCN by vapour diffusion of Et₂O gives blue crystals of the monomeric octahedral complex [Cu^II(pyppt)₂(ClO₄)₂] · MeCN (2). In contrast, addition of EtOH to a solution of complex 1 in MeCN followed by slow evaporation yields blue crystals of the five-coordinate polymeric complex {[Cu^II(pyppt)₂](ClO₄)₂ · EtOH}_∞ (3). The structures of both complexes have been determined by single crystal X-ray diffraction.     

Copper(I) and silver(I) tertiary phosphines complexes: Synthesis, X-ray structures and spectroscopic characterization

Six new complexes, [Cu₄I₄(PPh₂Cy)₄]·2H₂O (1), [CuI(PPhCy₂)₂] (2), [CuCl(PPhCy₂)₂] (3), and [CuBr(PPh₃)₃]·CH₃CN (4), [Ag(PPhCy₂)₂(NO₃)] (5), [Ag(PCy₃)(NO₃)]₂ (6) [where Ph = phenyl, Cy = cyclohexyl], have been synthesized and structurally characterized by X-ray diffraction, IR absorption spectra and NMR spectroscopic studies (except complex 4). The X-ray diffraction analysis of complex (1), pseudo polymorph of complex [Cu₄I₄(PPh₂Cy)₄], reveals a stella quadrangula structure. The four corners of the cube are occupied by copper(I) atoms and four I atoms are present at the alternative corners of the cube, further more the copper(I) atoms are coordinated to a monodentate tertiary phosphine. Complexes (2) and (3) are isostructural with trigonal planar geometry around the copper(I) atom. The crystal structure of complex (4) is a pseudo polymorph of complex [CuBr(PPh₃)₃] and the geometrical environment around the copper(I) centre is distorted tetrahedral. In the Ag^I complexes (5) and (6), the central metal atoms have pseudo tetrahedral and trigonal planar geometry, respectively. Spectroscopic and microanalysis results are consistent with the single crystal X-ray diffraction studies.     

Ternary copper(II) complexes with hippurate derivatives and 1,10-phenanthroline: Synthesis and biological activity

Several new Cu-hippurate derivative-phenanthroline ternary complexes have been prepared. The X-ray structure of one of them, [Cu(hip)(phen)₂]⁺·(hip⁻) (2) (where hip is hippurate and phen is 1,10-phenanthroline) has been solved. The structure of this new compound shows important differences (3D-pattern) to other similar related complexes (2D-pattern). A study of the biological activity of [Cu(hip)(phen)₂]⁺·(hip⁻)·2H₂O (2), [Cu(BGG)(phen)₂]⁺·(BGG⁻)·6H₂O (3), [Cu(B^IGG)₂(phen)](H₂O) (4) and [Cu(I-hip)(bpy)₂]⁺·(I-hip⁻)·3.5H₂O (5) (where I-hip is ortho-iodohippurate, BGG corresponds to benzoylglycilglycine, and B^IGG is ortho-iodobenzoylglycilglycine) is included and compared with the anti-proliferative activity of [Cu(I-hip)(phen)₂]⁺·(I-hip⁻)·7H₂O (1) previously described, resulting in a greater cytotoxic activity of the compounds with 1,10-phenanthroline instead of those with 2,2′-bipyridyl, in the same way that removing iodine substitution or lengthening the peptidic chain diminishes the activity of compounds compared with 1. The presence of an ortho-iodine group and the direct bond between Ar-CO and glycine moieties yield to the best results.     

Manganese (III) cyclam complexes with aqua, iodo, nitrito, perchlorato and acetic acid/acetato axial ligands

The syntheses, structures and magnetic properties of five new manganese (III) cyclam complexes, trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O, trans-[Mn(cyclam)I₂]I, trans-[Mn(cyclam)(ONO)₂]ClO₄, trans-[Mn(cyclam)(OClO₃)₂]ClO₄ and trans-[Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂, are reported. Cyclam is the tetradentate amine ligand 1,4,8,11-tetraazacyclotetradecane. The complexes all exhibit pronounced tetragonal elongation of the coordination octahedron with the four cyclam nitrogens occupying the four equatorial positions. The magnetic properties are consistent with the formulation of the complexes as high-spin d⁴ systems. trans-[Mn(cyclam)(OH₂)₂](CF₃SO₃)₃ · H₂O is shown to be a convenient starting material for the syntheses of trans cyclam complexes. [Mn(cyclam)(CH₃COO)(CH₃COOH)](ClO₄)₂ exhibits extremely short intermolecular hydrogen bonds resulting in a pseudo-chain structure. The tilt of the axial ligands with respect to the equatorial plane containing the manganese and the cyclam nitrogen atoms is discussed.     

Synthesis, spectral and X-ray structural studies of a NO donor Schiff base ligand and its Ni(II) complexes

The Schiff base ligand, 4-isopropylbenzaldehyde[N-(3-oxo-3,4-dihydro-2-quinoxalinyl)hydrazone] (Ipbh), the 1:1 condensation product of 4-isopropylbenzaldehyde and 2-hydroxy-3-hydrazinoquinoxiline, has been synthesized and characterized by X-ray crystallography. A series of complexes of Ipbh with Nickel(II), viz., [Ni(Ipbh)₂]Cl₂ (1), [Ni(Ipbh)₂]Br₂ (2), [Ni(Ipbh)₂]I₂ (3), [Ni(Ipbh)₂·(CH₃OH)₂](NO₃)₂·(CH₃OH)₂ (4) and [Ni(Ipbh)₂ClO₄]ClO₄ (5) have been synthesized. All the complexes were characterized by elemental analysis, molar conductivity, CHN analysis, spectroscopic studies, magnetic susceptibility measurements and TG/DTA methods. The solid-state structure of the complex 4 was established by single crystal X-ray crystallography. In all the complexes, Ipbh acts as a bidentate NO chelating agent, coordinated to the metal ion through the imine nitrogen and quinoxaline oxygen. In complex 4, Nickel(II) is in a distorted octahedral environment with an identical set of donor atoms, N₂O₄, coming from two imine nitrogen and two quinoxaline oxygen atoms of two Ipbh moieties as well as two oxygen atoms of the two methanol molecules. The crystal packing of Ipbh and the complex 4 exhibits 1D and 2D supramolecular networks, respectively through different intermolecular hydrogen-bonding interactions.     

Structures of homoleptic eight- and nine-coordinate uranium(IV) perchlorate complexes with sulfoxide molecules as ligands

Homoleptic eight- and nine-coordinate U(IV) perchlorate complexes with sulfoxide ligands have been characterized crystallographically. Crystals of [U(dmso)₈](ClO₄)₄ · 0.75CH₃NO₂, [U(dmso)₉](ClO₄)₄ · 4dmso (dmso = dimethyl sulfoxide), and [U(tmso)₈](ClO₄)₄ · 2tmso (tmso = tetramethylene sulfoxide) were found to have dodecahedral, tricapped trigonal prismatic, and square antiprismatic geometries, respectively. Average U-O bond distances in [U(dmso)₈](ClO₄)₄ · 0.75CH₃NO₂, [U(dmso)₉](ClO₄)₄ · 4dmso, and [U(tmso)₈](ClO₄)₄ · 2tmso are 2.35(3), 2.41 (4), and 2.35(3) Å, respectively. Furthermore, it was found that [U(dmso)₈]⁴⁺ is in equilibrium with [U(dmso)₉]⁴⁺ in CH₃NO₂ solution containing dmso. Thermodynamic parameters for such an equilibrium are as follows: K (25 °C) = 3.4 ± 0.2 dm³ mol⁻¹, ΔH = −54.9 ± 4.5 kJ mol⁻¹, and ΔS = −174 ± 15 J K⁻¹ mol⁻¹.     

Synthesis, structures, and magnetic properties of dicopper(II) and dinickel(II) complexes with a new bis(macrocycle), 7,7-(2-hydoxypropane-1,3-diyl)bis{3,7,11,17-tetraazabicyclo[11.3.1]- heptadeca-1(17),13,15-triene}

A new bis(macrocycle) ligand, 7,7^′-(2-hydoxypropane-1,3-diyl)-bis{3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene} (HL), and its dicopper(II) ([Cu₂(HL)Cl₂](NO₃)₂ · 4H₂O (4a), [Cu₂(HL)I₂]I₂ · H₂O (4b)) and dinickel(II) ([Ni₂(L)(OH₂)](ClO₄)₃ (5a), [Ni₂(L)(OH₂)]I₃ · 2H₂O (5b), [Ni₂(L)N₃](N₃)₂ · 7H₂O (5c)) complexes have been synthesized. The alkoxide bridged face-to-face structure of the dinickel(II) complex 5c has been revealed by X-ray crystallography, as well as the “half-opened clamshell” form of the bis(macrocyclic) dicopper(II) complex 4b. Variable temperature magnetic susceptibility studies have indicated that there exists intramolecular antiferromagnetic coupling (J=−33.8 cm⁻¹ (5a), −32.5 cm⁻¹ (5b), and −29.7 cm⁻¹ (5c)) between the two nickel(II) ions in the nickel(II) complexes.     

Photoluminescent coordination polymers of d metals with 4,4′-dipyridylsulfide (dps)

Reactions of AgClO₄, Zn(CH₃COO)₂ · H₂O and CuI with the ligand 4,4′-dipyridylsulfide (dps) in 1:1 ratio give rise to coordination polymers 1-3 and 5, the structures of which were characterized by X-ray crystallography. Polymers [Ag₂(dps)₂](ClO₄)₂ · MeCN (1) and [Ag₂(dps)₂(μ₂-MeCN)(MeCN)](ClO₄)₂ · MeCN · H₂O (2) are pseudo-supramolecular isomers, differing from each other in the coordination geometry of silver atom and the packing pattern. Both 1 and 2 are zigzag coordination polymers bridged by weak Ag?Ag, Ag?S or Ag?NC-CH₃ interactions to form double stranded coordination polymers. While [Zn(dps)(CH₃COO)₂] (3) is a zigzag single stranded coordination polymer, [Zn(dps)₂(H₂O)₂](ClO₄)₂ · H₂O (4) is an unusual mononuclear complex with a box-like structure. Interesting intermolecular hydrogen bonding present in the compounds 3 and 4 leads to 3D hydrogen-bonded network structure.Coordination polymer [Cu₂I₂(dps)₂] (5) is a non-interpenetrating (4,4) net. Photoluminescence properties of the compounds 1-5 have been examined in solid states at room temperature. These compounds have been found to exhibit yellow and blue photoluminescence.     

Synthesis, crystal structure and esterification of a novel iron(III) 18-metallacrown-6 complex

The trianionic heptadentate ligand, (Z)-3-(5′-chlorosalicylhydrazinocarbonyl) propenoic acid, has been synthesized and reacted with FeCl₃·6H₂O, to produce the complex [Fe^III₆(C₁₂H₈N₂O₅Cl)₆(H₂O)₄(CH₃OH)₂]·8H₂O·4CH₃OH. In the self-assembly process the ligand was esterified and transferred into (Z)-methyl 3-(5′-chlorosalicylhydrazinocarbonyl) propenoate. In the crystal structure, the neutral Fe(III) complex contain a 18-membered metallacrown ring consisting of six Fe(III) and six trianionic ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Fe(III)-N-N]. Due to the meridional coordination of the ligands to the Fe³⁺ ions, the ligands enforce the stereochemistry of the Fe³⁺ ions as a propeller configuration with alternating Λ/Δ forms. The metallacrown can be treated with SnCl₂ or Zn powder to obtain purified ester.     

A bicarbonate bridged diruthenium(I) complex: Key evidence for the decarboxylation step in the base-assisted reduction of Ru2Cl4(CO)6

Base-assisted reduction of [Ru(CO)₃Cl₂]₂ in the presence of NP-Me₂ (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru₂(CO)₄Cl₂(NP-Me₂)₂] (1). Two NP-Me₂ and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru-Ru single bond. Reaction of [Ru(CO)₃Cl₂]₂, TlOTf, KOH and NP-Me₂ in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru₂(CO)₂(μ-CO)₂(μ-O₂COH)(NP-Me₂)₂](OTf) (2). The in situ generated CO₂ is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [Ru^II(CO)₃Cl₂]₂ → [Ru^I₂(CO)₄]²⁺.     

Dithionitronium hexachloroantimonate: A thionitrosylating reagent

The reaction of Ru(CO)₃(PPh₃)₂ with (NS₂)(SbCl₆) in acetonitrile results in the formation of [Ru(CO)₂(NS₂)(PPh₃)₂](SbCl₆) which reacts with PPh₃ to give the thionitrosyl complex [Ru(CO)₂(NS)(PPh₃)₂](SbCl₆). The NS₂-complex in CH₂Cl₂ gives Ru(CO)₂Cl₂(PPh₃)₂.     

Synthesis and structural characterization of dinuclear iridium hydrido complex with 3,6-bis(2-pyridyl)tetrazine, [Ir2(H)4(PPh3)4(bptz)](PF6)2 · 4CH2Cl2

Reaction of the precursor Ir complex [Ir(H)₂(PPh₃)₂(Me₂CO)₂]PF₆ with 3,6-bis(2-pyridyl)tetrazine (bptz) in CH₂Cl₂ gave a novel dinuclear Ir hydrido complex [Ir₂(H)₄(PPh₃)₄(bptz)](PF₆)₂ · 4CH₂Cl₂. Crystallographic study described an interesting coordination environment having a π-π interaction and ¹H NMR study showed unique upfield shifts of pyridyl rings that are likely induced by the ring current effect of neighboring PPh₃ ligands.