An unusual six-co-ordinate platinum(II) complex containing a neutral I2 ligand

The present paper deals with a rare platinum(II) complex containing the kappa-I2 ligand, which is an unusual example of a six-co-ordinated octahedral platinum(II) complex.     

A tetrameric neptunyl(v) cluster supported by a Schiff base ligand

The first tetrameric cation-cation neptunyl(v) cluster, [{NpO(2)(salen)}(4)(μ(8)-K)(2)][K(18C6)Py](2), has been synthesized in non-aqueous solution from the reaction of [(NpO(2)Py(5))(KI(2)Py(2))](n) with K(2)salen and its structure determined in the solid state and in solution where the complex retains its tetrameric form.     

Light-induced water oxidation by a Ru complex containing a bio-inspired ligand

The new Ru complex 8 containing the bio-inspired ligand 7 was successfully synthesized and characterized. Complex 8 efficiently catalyzes water oxidation using Ce(IV) and Ru(III) as chemical oxidants. More importantly, this complex has a sufficiently low overpotential to utilize ruthenium polypyridyl-type complexes as photosensitizers.     

An unusual ligand in copper chemistry: coordination oligomers and polymers containing the [[CpMo(CO)2]2(mu,eta2-Sb2)] cluster

The coordination behavior of [[CpMo(CO)(2)}(2)(mu,eta(2)-Sb(2))] (1; Cp = cyclopentadiene) toward Cu(I) was investigated. Its reaction with CuX (X = Br, Cl, and I) produced oligomers or polymers of the general formula [[CpMo(CO)(2)](2)(mu,eta(2)-Sb(2))(mu-CuX)](n). While 2 (X = Cl, n = 2) and 3 (X = Br, n = 2) proved to be halogen-bridged dimers in both solution and solid state, the molecules of 4 (X = I, n = infinity) self-assembled in the crystal forming a linear polymer with a Cu-I skeleton supported by Sb-Cu bonds. The reaction of 1 with Cu[GaCl(4)] resulted in the formation of the ionic complex [[CpMo(CO)(2)](2)(mu,eta(2)-Sb(2))](4)Cu(2)[GaCl(4)](2) (5). Its dication contains four [[CpMo(CO)(2)](2)(mu,eta(2)-Sb(2))] ligands arranged around a Cu-Cu dumbbell. All new compounds were characterized using IR, electrospray ionization mass spectrometry, (1)H NMR, elemental analysis, and single-crystal X-ray diffraction. The ligand was oxidized by both silver(I) and copper(II), and a cyclovoltammetric study revealed that 1 suffered irreversible reduction and oxidation in a dichloromethane solution at -2.04 and 0.10 V, respectively, versus ferrocene.     

A Cu(I) cluster bearing a bridging phosphane ligand

The solid state structure of a Cu(I) cluster bearing bridging phosphane ligands is described. This Cu₄ cluster results from a formal Cl-abstraction of the CH₂Cl₂ solvent. This derivative is the first example of a multinuclear Cu(I) complex bearing bridging phosphane ligands in which the Cu(I) centers have different coordination geometries. The four Cu(I) ions participate in metallophilic interactions within this cluster. Interestingly, despite the gross molecular structure being highly dissymmetrical, the μ-P atoms bridge symmetrically the metal centers.     

Dynamic behaviour of Ru and Ru-Pt complexes containing tetrahedro-P4 ligand

Dynamic processes involving the P(4) cage coordinated to transition metal fragments were observed for the mononuclear complex trans-[Ru(dppm)(2)(H)(η(1)-P(4))]BF(4) and for the bimetallic derivative trans-[Ru(dppm)(2)(H)(μ ,η(1:2)-P(4)){Pt(PPh(3))(2)}]BF(4) as demonstrated by NMR experiments and DFT calculations.     

Synthesis and crystal structure of a new oxamidato-bridged trinuclear Cu2 II MnII complex containing a macrocyclic ligand

A new oxamidato-bridged trinuclear complex [(CuL)₂Mn](ClO₄)₂ (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4, 8,12-tetraazacyclo-pentadeca-7,3-dien)] was prepared and its structure determined. The complex is monoclinic, space group P2₁/n, with a = 10.625(3), b = 11.602(3), c = 16.020(5)?Å, β = 91.031(5)°, Z = 2; it was refined to R1 = 0.0555. In the solid state, the structure consists of centrosymmetric [(CuL)₂Mn]²⁺ cations separated by perchlorate anions; the central manganese atom is four coordinated with square planar geometry.     

An engineered azurin variant containing a selenocysteine copper ligand

Modulating the properties of proteins through de novo design or redesign of existing proteins has been a longstanding goal in protein chemistry. Over the past two decades, site-directed mutagenesis has been a powerful tool to probe the role of certain residues and to fine-tune the activity of proteins. A limitation of this approach has been the accessibility of only a restricted number of functional groups through the 20 amino acids in the genetic code. The more recent technique of expressed protein ligation (EPL) provides an alternative route that allows efficient incorporation of nonnatural residues into proteins. We report here the preparation and spectroscopic characterization of an azurin variant in which a cysteine ligand to the blue copper center has been replaced by EPL with selenocysteine (Sec). This reports marks the first time that selenocysteine is artificially incorporated into the active site of a metalloprotein. The variant displays a significantly increased A(parallel) (from 56 to 104 G) and red-shifted CT band (from 625 to 677 nm), while maintaining the general type 1 copper characteristics, including similarity in reduction potentials. This study illustrates that iso-structural substitution using EPL can fine-tune the structural and functional properties of a metal-binding site without loss of most of its characteristics. Further spectroscopic and X-ray crystallographic studies of this and other EPL variants will provide new insights into the fine-control of the structure and function of metalloproteins.     

Trimethyltriazacyclohexane as bridging ligand for triangular Cu3 units and C-H hydride abstraction into a Cu6 cluster

Reaction of [Cu(MeCN)4](BF4) with N,N',N"-trimethyl-1,3,5-triazacyclohexane in CH2Cl2 leads to two Cu6 clusters containing the triazacyclohexane as a ligand to triangular Cu3 units with the abstraction and incorporation of chloride and hydride.     

An unprecedented 8-fold interpenetrating diamondoid-like coordination polymer containing a Cu+(4)(RCO2)(4) cluster as connecting node

The reaction of Cu(I)(CH(3)CN)(4)BF(4) with 4-pyridylacrylic acid (4-HPYA) affords an unprecedented 8-fold interpenetrating diamondoid-like coordination polymer network [Cu(I)(3)(4-PYA)(2)(H(2)O)(BF(4)) ] (1) with a Cu(+)(4)(CO(2))(4) cluster as connecting node. The interpenetration in metal coordination polymers is the highest degree ever found within diamondoid nets containing a cluster as connecting note. Its fluorescent property was also reported.     

Formation of a tetranuclear nickel(ii) complex containing an unusual bridging ligand

Russian Chemical Bulletin -     

Synthesis and crystal structure of a new triosmium alkylidyne carbonyl cluster containing a chiral ferrocenylphosphine ligand

The synthesis, spectroscopic characterization and X-ray crystal structure of a new chiral triosmium alkylidyne carbonyl cluster, (R,S)-[Os3(mu-H)2(CO)9{mu3-CPPh2(eta(5)-C5H4)Fe(eta(5)-C5H3(PPh2)CH(Me)NM(2)}] (1) are described. Compound 1 crystallizes in the non-centrosymmetric space group P2(1) and its absolute configuration has been established.The structure consists of an Os3C metal core with one of the PPh2 moieties of the chiral ferrocenylphosphine bonded to the apical alkylidyne carbon atom to give a zwitterionic cluster complex, reminiscent of the phosphorus ylide.     

A bis 1,10-phenanthroline ligand leading to octahedral Ru(II) complexes containing a well-defined axis

A bis-chelating ligand (1), made of two 1,10-phenanthroline subunits connected with a p-(CH₂)₂C₆H₄(CH₂)₂- spacer through their 4 positions, has been prepared, using Skraup syntheses and reaction of the anion of 4-methyl-7-anisyl-1,10-phenanthroline with α,α’-dibromo-p-xylene. Complexation of 1 with Ru(CH₃CN)₄Cl₂ and subsequent reaction with 4,4’-dimethyl-2,2’-bipyridine afforded an octahedral Ru(II) tris-diimine complex, in which a well-defined axis running through the terminal anisyl substituents and the central metal has been created, as shown by an X-ray molecular structure analysis.     

An iron(III) phosphonate cluster containing a nonanuclear ring

This communication reports the first example of cyclic ferric clusters with an odd number of iron atoms capped by phosphonate ligands, namely, [Fe9(mu-OH)(7)(mu-O)2(O3PC6H9)8(py)12]. The magnetic studies support a S = 1/2 ground state with an exchange coupling constant of about J approximately equal to -30 K.     

Ru and Os complexes containing a P,N-donor heterotopic ligand: the effect of solvent on stereochemistry

Ruthenium and osmium complexes of the general formula MCl 2(PyP) 2 (where PyP is the P,N- donor ligand 1-(2-diphenylphosphinoethyl)pyrazole) were synthesized from MCl 2(PPh 3) 3 (where M = Ru or Os). Three of the five possible stereoisomers of RuCl 2(PyP) 2 were synthesized and characterized in solution by multinuclear NMR spectroscopy, and the structure of these in the solid state was determined by X-ray crystallography. Two of the analogous Os isomers were also synthesized. It was found that different solvents induced isomerization between these stereoisomers, indicating either lability of the chloride anion or hemilability of the PyP ligand. Bimetallic complexes of the general formula [Ru(mu-Cl)(PyP) 2] 2[X] 2 were synthesized from chloride abstraction from RuCl 2(PyP) 2 using either silver (X = OSO 2CF 3, BF 4) or sodium (X = BPh 4) salts. The osmium analogue of the Ru bimetallic complexes, [Os(mu-Cl)(PyP) 2] 2[BPh 4] 2, was also synthesized. Solid-state structures were obtained using X-ray crystallography for the osmium bimetallic complex and the ruthenium bimetallic complex where X = OSO 2CF 3. The hemilability of PyP was demonstrated through the synthesis of RuCl 2(CO)(kappa (1)- P-PyP)(kappa (2)- P, N-PyP), which contains one pendant PyP ligand, bound through the P-donor atom.     

Synthesis,crystal structure and nonlinear optical properties of a cluster compound containing the bipy ligand

The [MoO_0.75S_3.25Cu₃Cl(bipy)₂] complex was synthesized for nonlinear optical studies by the reaction of (NH₄)₂[MoOS₃], CuCl and bipy in CH₂Cl₂ solution. A single crystal X-ray analysis revealed that the complex consists of a nest-shaped core. The Mo atom is tetrahedrally coordinated by four S atoms, or three S atoms and one terminal O atom. There are two types of copper atom in the MoO_0.75S_3.25Cu₃ aggregate: two copper atoms are tetrahedrally coordinated and another copper atom is trigonally coordinated. The third-order nonlinear optical properties were investigated by the Z-scan technique with 8 ns laser pulses at 532 nm. The cluster exhibits both optical self-focusing and optical nonlinear absorption (effectively n ₂ = 1.3 × 10^–11 e.s.u., ₂ = 1.2 × 10^–10 m W^–1 in a 2.68 × 10^–4 mol dm^–3 CH₂Cl₂ solution).     

Heterometallic cluster [CpMn(CO)2]2S2Ni(Dppe) containing the binuclear manganese disulfide complex as a ligand

A reaction of the disulfide complex [CpMn(CO)₂]₂S₂ with the Ni(0) diphosphine acetylene complex, (Dppe)Ni(C₂Ph₂) (I), yielded the heterometallic complex [CpMn(CO)₂]₂S₂Ni(Dppe) (II). An X-ray diffraction study revealed lateral coordination of the disulfide group to the Ni atom in complex II, which results in lengthening of both the S-S and Mn-S bonds against those in the starting complex. However, the Mn-S and Ni-S bonds are still much shorter than the sums of the covalent radii of the corresponding atoms.     

Photodecomposition of peroxides containing a 1,4-bis(phenylethynyl)benzene chromophore

The photodecomposition dynamics of 1,4-bis(2-[4-tert-butylperoxycarbonylphenyl]ethynyl)benzene (1) have been compared with those of model compounds in the picosecond and nanosecond time domains by various photophysical techniques. Ultrafast visible transient absorption spectrometry revealed the singlet excited state of 1,4-bis(4-phenylethynyl)benzene (BPB) depopulates radiatively with a rate of 1.75 x 10(9) s(-1) and 95% efficiency. Phenyl ester moieties attached to the BPB core accelerate intersystem crossing (k = 2.8 x 10(8) s(-1)) and reduce the fluorescence quantum yield (phi(FL) = 0.82). The peroxide oxygen-oxygen bond of 1 cleaves (k = 3.6 x 10(11) s(-1)) directly from the singlet excited state (60% efficiency) causing a highly reduced fluorescence yield and leading to formation of aroyloxyl radicals. The next reaction step involves decarboxylation of the aroyloxyl radicals. Transient absorption signals in the MID IR region correspond to CO2 with the formation rate (2.5 x 10(6) s(-1)) as measured by nanosecond transient IR experiments. The transient IR spectra of the excited state of BPB, as well as of the aroyloxyl radical, evidenced a red shift in the acetylene triple bond absorption indicative of a decrease in the bond order. This clearly shows that delocalization of excitation energy over the BPB chromophore induces significant structural changes. The proposed mechanism is based on the rates of photophysical and photochemical channels and involves an additional population channel of the BPB triplet excited state from the upper singlet states.     

An unexpected and unusual V(5+)10 cluster containing oxygen bridges as well as six bidentate acetylacetonates

Structural Chemistry - A cluster of 10 vanadium (5+) atoms bridged by 22 oxygen atoms and having six of the vanadiums around the periphery each bound to a single bidentate acetylacetone is...