Synthesis and characterization of amine complexes of the cyclopentadienyliron dicarbonyl complex cation, [Cp(CO)2Fe]

The organometallic Lewis acid, [CpFe(CO)₂]⁺ (Cp = η⁵-C₅H₅) reacts with excess dry diethyl ether at low temperatures to form the labile complex [CpFe(CO)₂(Et₂O)]⁺[BF₄]⁻ (1) which is stable at low temperatures and has been fully characterized. Complex 1 in turn reacts with 1-aminoalkanes and α,ω-diaminoalkanes to form new complexes of the type [CpFe(CO)₂NH₂(CH₂)_nCH₃]BF₄ (n = 2-6) (2) and [{CpFe(CO)₂}₂μ-(NH₂(CH₂)_nNH₂)](BF₄)₂ (n = 2-4) (3), respectively. These complexes have been fully characterized and the mass spectral patterns of complexes 2 are reported. The structures of compounds 2a (n = 2) and 2b (n = 3) have been confirmed by single crystal X-ray crystallography. The single crystal X-ray diffraction data show that complex 2a, [CpFe(CO)₂NH₂(CH₂)₂CH₃]BF₄, crystallizes in a triclinic space group while 2b, [CpFe(CO)₂NH₂(CH₂)₃CH₃]BF₄, crystallizes in an orthorhombic Pca2₁ space group with two crystallographically independent molecular cations in the asymmetric unit. Furthermore, the reaction of 1 with 1-alkenes gives the η²-alkene complexes in high yield.     

Trimethylsilylplatinum(IV) complexes as reaction intermediates

The oxidative addition of I₂, PhCH₂Br and MeI with [Pt(CH₂SiMe₃)₂(DPK)], 1, DPK = di-2-pyridyl ketone, occurred with trans stereochemistry to give [PtI₂(CH₂SiMe₃)₂(DPK)], [PtBr(CH₂Ph)(CH₂SiMe₃)₂(DPK)] and [PtIMe(CH₂SiMe₃)₂(DPK)], respectively. Complex 1 reacted with acids HX (X = Cl or CF₃CO₂) to give initially the hydridoplatinum complexes [PtHX(CH₂SiMe₃)₂(DPK)], but these complexes were thermally unstable and decomposed largely by α-silyl migration to give compounds such as [PtX(SiMe₃)Me₂(DPK)], as determined by monitoring the reactions by NMR at low temperature. With excess acid, HX, at room temperature, the products were largely [PtX₂(DPK)], CH₄ and Me₃SiX with Me₄Si as a minor product only. The mechanism of the easy Si-CH₂ bond cleavage is discussed.     

Syntheses of some new methylcyclopentadienylmolybdenum complexes: Characterizations, crystal structures and comparisons with related complexes

As part of a long-term study of the substitution reactions of piano-stool type cyclopentadienylmetal carbonyl complexes, several new methylcyclopentadienylmolybdenum compounds have been prepared and characterized by methods including IR spectroscopy, electrospray ionization mass spectrometry and X-ray crystallography. The complexes reported here include [{Cp′Mo(CO)₃}₂I]BPh₄, cis-Cp′Mo(CO)₂(PPh₃)I and [Cp′Mo(CO)₃(CH₃CN)]BF₄ (Cp′ = η⁵-C₅H₄CH₃). In addition to their syntheses, comparisons are made between their IR spectroscopic and X-ray crystal structure data and those of similar complexes.     

A dinuclear,metal-metal bonded,carboxylato-bridged niobium(III) complex

Nb₂Cl₆(THT)₃, THT=tetrahydrothiophene, reacts with excess tetramethylammonium acetate to give an ionic Nb(III) complex, (NMe₄)[Nb₂Cl₂(THT)(CH₃CO₂)₅]·CH₂Cl₂. The compound has been characterized by NMR, IR, cyclic voltammetry and X-ray crystallography. It crystallizes in an orthorhombic space group P2₁2₁2₁ with a=11.326(3) Å, b=11.857(4) Å, c=24.343(6) Å, V=3269(3) ų and Z=4. The NbNb distance is equal to 2.764(1) Å which together with the diamagnetism of the complex indicates a double metal-metal bond. The acetato ligands coordinate in three different modes: bridging bidentate, chelating and bridging unidentate.     

Novel p-tolylimido rhenium(V) complexes incorporating quinoline-2-carboxylate ion - Synthesis, X-ray studies, spectroscopic characterization and DFT calculations

Novel p-tolylimido rhenium(V) complexes trans-[Re(p-NC₆H₄CH₃)X₂(quin-2-COO)(PPh₃)] and cis-[Re(p-NC₆H₄CH₃)X₂(quin-2-COO)(PPh₃)]·MeCN have been obtained in the reactions of [Re(p-NC₆H₄CH₃)X₃(PPh₃)₂] (X = Cl, Br) with quinoline-2-carboxylic acid. The compounds were identified by elemental analysis IR, UV-Vis spectroscopy and X-ray crystallography. The electronic structures of trans- and cis-halide isomers of [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] have been calculated with the density functional theory (DFT) method. Additional information about binding in the compounds [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] with cis- and trans-halide arrangement has been obtained by NBO analysis. The electronic spectra of trans and cis isomers of [Re(p-NC₆H₄CH₃)Cl₂(quin-2-COO)(PPh₃)] were investigated at the TDDFT level employing B3LYP functional in combination with LANL2DZ.     

Synthesis and characterization of new cationic hydride complexes of rhodium(III)

New cationic hydride complexes of rhodium(III) with PR₃ and R-DAB ligands have been prepared and characterised. The tertiary phosphines employed were PPh₃, PMePh₂, PEt₃ and the R-DAB ligands, (RN:CR′CR′:NR), c-Hex-DAB, Ph-DAB, NH2-DAB-(CH₃,CH₃). Hexacoordinate-dihydride complexes, characterized by ¹H and ³¹P NMR, with stoichiometry [RhH₂(R-DAB)(PR₃)₂]X were obtained. Compounds with other stoichiometries (R-DAB/PR₃=1 or 2) are also possible. Preliminary studies of the catalytic activity in hydrogenation of olefins have been carried out.     

Tetranuclear mixed-valence Co(II/III) and binuclear Ni(II) complexes incorporating hydroxyl-rich ligand: Syntheses, structures and magnetic properties

Three complexes of composition [Co₂^IICo₂^III(H₂hbhpd)₂(H₄hbhpd)₂(H₂O)₂]Cl₂(CH₃OH)₄ (1), [Co₂^IICo₂^III(H₂hbhpd)₂(H₄hbhpd)₂(H₂O)₂](NO₃)₂(CH₃OH)₄ (2) and [Ni₂(H₄hbhpd)₂(NO₃)](NO₃)(CH₃OH)_1.5 (3) (H₅hbhpd = 2-(2-hydroxy-benzylamino)-2-hydroxymethyl-propane-1,3-diol) have been synthesized and their structures have been characterized. Complexes 1 and 2 are mixed-valence cobalt clusters and display face-sharing monovacant dicubane structures. In the complexes 1 and 2, one of the three alkyl hydroxyl groups of H₅hbhpd ligand is deprotonated instead of deprotonation of phenyl hydroxyl group; thus monoanionic H₄hbhpd⁻ ligand displays novel η³, η¹, η¹, μ₃ coordination mode. Complex 3 is binuclear, and the two metal centers of 3 are bridged by two deprotonated phenyl hydroxyl oxygen atoms and iso-orthogonalized by a nitrato group in η¹η¹-O,O′ coordination fashion. Variable-temperature solid-state dc magnetization studies have been performed in the temperature range 2-300 K for compounds 1 and 3. Antiferromagnetic interactions were determined for 1 and ferromagnetic couplings were found for 3.     

Syntheses,characterization and redox properties of di- and poly-phosphine linked oligomeric complexes of oxo-centered triruthenium clusters

A series of phosphine-linked oligomers of oxo-centered triruthenium-acetate clusters have been prepared by the reaction of [Ru₃O(OAc)₆(py)₂(CH₃OH)](PF₆) (1) with di- or poly-phosphine. They have been characterized by elemental analysis, ESI-MS spectrometry, UV–Vis, IR, and ³¹P NMR spectroscopy, and cyclic and differential pulse voltammetry. The structures of diphosphine-linked dimeric compounds 4 and 7 were determined by X-ray crystallography. As revealed by redox wave splitting, weak to moderate electronic communication is operative between triruthenium clusters across bridging di- or poly-phosphine. With increase of the methylene number in Ph₂P(CH₂)_nPPh₂, electronic communication decreases rapidly in diphosphine-linked dimeric complexes [{Ru₃O(OAc)₆(py)₂}₂{μ-Ph₂P(CH₂)_nPPh₂}]²⁺ (n = 1–5).     

Synthesis and study on telluronium salts based on 1-oxa-4-organo-4-telluracyclohexane cation

A new series of heterocyclic telluronium salts (C₄H₈OTeRX: R=CH₃CH₂, CH₂CHCH₂, CH₃, C₄H₉, X=I; R=CH₂CHCH₂, X=Br; R=CH₃, X=ClO₄; R=CH₃, CH₃CH₂, C₆H₅, X=BPh₄) have been prepared. Conductivity measurements in dimethylsulphoxide (DMSO) and N,N-dimethytl- formamide (DMF) have shown that there is an ion pair interaction between the anion and the tellurium cation.¹H NMR studies showed that there is no reaction between the solute and the solvent. All compounds are stable in solution in DMSO. Infra-red spectra are reported and discussed.     

Conformations of model compounds of proteins. II. Infrared spectra of N-acetyl-amino acid methylamides

N-Acetyl-amino acid methylamides CH₃CONHCHRCONHCH₃ were prepared from L - and DL -alanine, L and DL -α-amino-n-butyric acid, L - and DL -norvaline, DL -norleucine, L - and DL -methionine, L - and DL -leucine, L -aspartic acid and DL -phenylalanine. The deuterium homologs of the type CH₃CONDCHRCONDCH₃, CD₃CONHCHRCONHCH₃, and CH₃CONHCHRCONHCD₃ were also prepared. The infrared spectra of these compounds were measured down to 300 cm^?1 in the crystalline state. The infrared spectra of N-isopropylacetamide CH₃CONHCH(CH₃)₂, N-methylisobutyramide (CH₃)₂CHCONHCH₃ and their deuterium homologs were also measured. The C?O in-plane and out-of-plane bending vibration bands of the CH₃CONHC^α group (amide IVa and VIa) and those of the –C^αCONHCH₃ group (amide IVb and VIb) were assigned from these data. Two crystalline modifications, form I and form II, were found for the compounds prepared from L -alanine, DL -leucine, L -aspartic acid and DL -phenylalanine. The two forms show quite different skeletal vibrations, which suggest, rotational isomerism. Two distinct patterns were found as to the positions of the amide IVa and VIa bands for the above compounds. The two amide bands were found near 630 and 600 cm^?1 in form I, whereas they were found near 600 cm^?1 in form II. The crystals of the remaining compounds were also classified into form I or form II on the basis of the arrangement of the amide bands. The X-ray structure analyses suggest that these two forms have different hydrogen-bond structures.     

Synthesis and spectroscopic studies of antimony pentachloride complexes with neutral oxygen, sulfur and selenium ligands

The compounds [SbCl₅(R₃EY)] (R = Me or Ph; E = P or As; Y = O or S) have been prepared from SbCl₅ and the appropriate ligand in CH₂Cl₂ or CCl₄ solutions, and characterised by analysis, IR, ¹H, ³¹P{¹H}, ¹²¹Sb NMR spectroscopy and conductance measurements. The [SbCl₅(μ-L-L)SbCl₅] L-L = Ph₂P(O)CH₂P(O)Ph₂, Ph₂P(O)(CH₂)₂P(O)Ph₂, Ph₂P(S)CH₂P(S)Ph₂, Ph₂As(O)CH₂As(O)Ph₂, and o-C₆H₄(P(O)Ph₂)₂ have been synthesised and similarly characterised. The unstable [SbCl₅(R₃PSe)] have been prepared at low temperatures and characterised by IR spectroscopy. In solution in chlorocarbons they decompose rapidly to Se and R₃PCl₂. The reactions of R₃SbS with SbCl₅ produced R₃SbCl₂.     

Hydrido-derivatives of [Ir4(CO)10(diphosphine)]: X-ray analyses of [Ir4H(CO)9(μ-Ph2PH(CH3)PPh2)] and [Ir4 H(CO)9(μ-Ph2P(CH2)nPPh2)] (n = 2, 3)

Some novel hydrido-anions of general formula [Ir₄H(CO)₉(μ-L-L)]⁻ (L-L = Ph₂PCH(CH₃)PPh₂, Ph₂P(CH₂)₂PPh₂, Ph₂P(CH₂)₃PPh₂ and Ph₂AsCH₂AsPh₂) have been obtained by the reaction of [Ir₄(CO)₁₀(μ-L-L)] with the base 1,8-diazabicyclo[5.4.0]undec-7-ene in wet dichloromethane. According to IR and ¹H, ³¹P and ¹³C NMR data at low temperature, these anionic derivatives display a single conformation in solution: three edge-bridging COs around the triangular basal face and both the hydride and the bidentate ligands located in axial positions relative to this face. The structures of four compounds were established by X-ray diffraction studies, which confirmed the configuration proposed on the basis of spectroscopic data.     

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.     

Reaction of FcCCo3(CO)9 with 2,3-bis(diphenylphosphino)maleic anhydride (bma). X-ray diffraction structure and redox properties of

A number of new coordination compounds with transition-metal salts and triazole-based heterocyclic ligands is described. The ligands used are disubstituted [1,2,4]triazolo[1,5-a]pyrimidines, with as substituents: ethyl, methyl and phenyl, and in addition a 2-methylthio-dimethyl ligand was used (sdmtp). To determine the structures of the coordination compounds in a number of cases 3D crystal structure determinations have been carried out, i.e. for [Fe(NCS)₂(detp)₃(H₂O)], [Co(NCS)₂(sdmtp)₂(H₂O)], [ZnBr₂(fmtp)₂], [Ni(NCS)₂(detp)₃(CH₃OH)] and [Fe(NCS)₂(fmtp)₂(H₂O)₂](fmtp). The latter compound is quite unusual as it contains an uncoordinated fmtp ligand in the crystal lattice with special packing features. The ligands and the coordination compounds have been further characterized by NMR, IR and LF spectra, as well as by C, H, N element analyses. The coordination around the metal varies from 4 (Zn), via 5 (Co) to 6 (for Ni and Fe).     

Coordination chemistry of substituted [1,2,4]triazolo[1,5-a]pyrimidines with first-row transition-metal ions: Synthesis, spectroscopy and single-crystal structure analysis

A number of new coordination compounds with transition-metal salts and triazole-based heterocyclic ligands is described. The ligands used are disubstituted [1,2,4]triazolo[1,5-a]pyrimidines, with as substituents: ethyl, methyl and phenyl, and in addition a 2-methylthio-dimethyl ligand was used (sdmtp). To determine the structures of the coordination compounds in a number of cases 3D crystal structure determinations have been carried out, i.e. for [Fe(NCS)₂(detp)₃(H₂O)], [Co(NCS)₂(sdmtp)₂(H₂O)], [ZnBr₂(fmtp)₂], [Ni(NCS)₂(detp)₃(CH₃OH)] and [Fe(NCS)₂(fmtp)₂(H₂O)₂](fmtp). The latter compound is quite unusual as it contains an uncoordinated fmtp ligand in the crystal lattice with special packing features. The ligands and the coordination compounds have been further characterized by NMR, IR and LF spectra, as well as by C, H, N element analyses. The coordination around the metal varies from 4 (Zn), via 5 (Co) to 6 (for Ni and Fe).     

Syntheses, crystal structures and thermal behaviors of three complexes with 4-acyl pyrazolone derivatives

Three new complexes, [Zn(PPePeP-PNH)(CH₃OH)]₂(CH₃OH) [PPePeP-PHN = N-(1-phenyl-3-phenylethyl-4-phenylethylene-5-pyrazolone) p-nitrobenzoylhydrazide] (1), [Mn(PPePeP-PNH)(CH₃OH)₂]₂(CH₃OH) (2), [Mn(PM4MbP-PNH)(C₂H₅OH)₃] [PM4MbP-PHN = N-(1-phenyl-3-methyl-4-(p-methylbenzoylene)-5-pyrazolone) p-nitrobenzoylhydrazide] (3), have been prepared and characterized by elemental analyses, IR spectra, UV-Vis absorption spectra, thermal-analyses and X-ray diffraction studies. The structural analyses show that the N(2) atoms of the pyrazolyl heterocycles play an important role in building the N-H?O hydrogen bonds of 1, 2, 3 and 1, 2 formed 2D networks and 3 formed 1D chain linked by hydrogen bonds, respectively.     

Diether functionalized rhodium(I)-N-heterocyclic carbene complexes and their catalytic application for transfer hydrogenation reactions

N-heterocyclic carbene (NHC) complexes of rhodium(I) (3 and 4) bearing one diether (MeOCH₂CH₂OCH₂CH₂-NHC) functionality on N¹ and bulky benzyl groups (CH₂-C₆H₂(CH₃)₃-2,4,6 and CH₂-C₆(CH₃)₅) on N³ of (5,6-dimethyl)benzimidazole were synthesized by deprotonation of the corresponding benzimidazolium salt with [Rh(μ-OMe)(1,5-cod)]₂ in dichloromethane at ambient temperature. All compounds have been fully characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. X-ray diffraction studies on single crystals of 3a and 3b confirm the cis square planar geometry. All of the new benzimidazol-2-ylidene rhodium(I) complexes were found to be effective catalysts for the transfer hydrogenation reaction.     

Synthesis, spectroscopic and structural characterization of Cu(II) derivatives of tris(pyrazol-1-yl)methanes

The reaction between CuX₂ (X=ClO₄, NO₃, Cl, Br and CH₃COO) and excess of tris(pyrazol-1-yl)methane ligands L (L=CH(pz)₃, CH(4-Mepz)₃, CH(3,5-Me₂pz)₃, CH(3,4,5-Me₃pz)₃ or CH(3-Mepz)₂(5-Mepz)) yields [CuX₂(L)], [{CuX₂}₃(L₂)₂] or [Cu(L₂)]X₂-type complexes. The ligand to metal ratio is dependent on the number and disposition of the Me substituents on the azole-type ligand and mainly on the nature of the counter-ion X. All complexes have been characterized in the solid state as well as in solution (IR and UV spectra, and conductivity determinations). The solid-state structures of [Cu{(3,5-Me₂pz)₃CH}₂](NO₃)₂, [Cu{(3,5-Me₂pz)₃CH}₂](ClO₄)₂·0.5H₂O, [Cu{(3,4,5-Me₃pz)₃CH}₂](NO₃)₂·H₂O, [Cu{(4-Mepz)₃CH}₂]Br₂·3H₂O have been determined by single crystal X-ray studies.     

Template synthesis of macrocyclic complexes and their spectroscopic and antibacterial studies

A new series of macrocyclic complexes of type [M(TML)X]X₂, where M = Cr(III), Fe(III), TML is tetradentate macrocyclic ligand, and X = Cl^?, NO₃^?, CH₃COO^?, have been synthesized by condensation of isatin and ethylenediamine in the presence of metal salt. The complexes were synthesized by both conventional and microwave methods. The complexes have been characterized with the help of elemental analysis, conductance measurement, magnetic measurement, and infrared, far infrared, and electronic spectral studies. Molar conductance values indicate them to be 1:2 electrolytes. Electronic spectra along with magnetic moments suggest five-coordinate square pyramidal geometry for these complexes. The complexes were also tested for their in vitro antibacterial activity. Some of the complexes showed satisfactory antibacterial activitiy.     

Cobalt(II) complexes of the antibiotic sulfadiazine, the X-ray single crystal structure of [Co(C10H9N4O2S)2(CH3OH)2]

Cobalt(II) complexes of sulfadiazine formulated as [Co(C₁₀H₉N₄O₂S)₂(CH₃OH)₂] and [Co(C₁₀H₉N₄S)₂(H₂O)₂] have been synthesized and characterized by elemental analysis, infrared and UV-Vis spectroscopy and magnetic susceptibility measurements. The crystal structures of the complex [Co(C₁₀H₉N₄O₂S)₂(CH₃OH)₂] and of free sulfadiazine are also reported. The cobalt complex and the sulfadiazine ligand both crystallize in the monoclinic space group, P21/c, with sulfadiazine acting as a bidentate ligand. Cobalt is coordinated to two-sulfonamide nitrogen and the pyrimidine nitrogen of the sulfadiazine. Two molecules of methanol complete the octahedral geometry around the cobalt, with interligand hydrogen bonding between methanol and sulfadiazine. Infrared spectroscopy confirmed the presence of water molecule in the coordination sphere of [Co(C₁₀H₉N₄S)₂(H₂O)₂]. The electronic spectra and magnetic moments of both complexes were similar, indicating that both complexes have similar structure.