Structural diversity in bishydroxylamine complexes of gallium

Reactions of bishydroxylamines of the type HON(R)CH2CH2N(R)OH (R=Me, tBu) with trimethyl- and triisopropylgallium gave bicyclic metalla cages of the formula R'2GaO(R)NCH2CH2N(R)OGaR'2 [R'=Me, R=Me (), tBu (); R'=iPr, R=Me (), tBu ()] with six-membered Ga2O2N2-rings. While the complexes show the same core constitution in the solid state, NMR spectra reveal the steric influence of the isopropyl substituent of the compounds / on its behaviour in solution. The reaction of the sterically more demanding substituted tri-tert-butylgallium with HON(Me)CH2CH2N(Me)OH yielded a heterodimeric complex O'-[HON(Me)CH2CH2NH(Me)O(tBu2Ga)]-cyclo-(tBu2Ga)-O,N'-[ON(Me)CH2CH2N(Me)O] () with two gallium atoms of different surrounding and two different bishydroxylamine ligands, one doubly deprotonated and one protonated, but at one end in its tautomeric aminoxide form. Further condensation of was observed to give a tricyclic compound cyclo-[(tBuGa)ON(Me)CH2CH2N(Me)O]2 () with a central Ga2O2N2 ring resulting from two Ga-N donor-acceptor bonds.     

Structural diversity of yttrium(III) halide complexes

X-ray crystallographic data on yttrium(III) compounds containing halide (pseudohalide) ligands in the coordination sphere have been summarized and systematized. Trends in the change in the coordination number (CN) and the coordination polyhedron geometry, as well as specific features of the central ion environment in monomeric, dimeric, and polymeric complexes, have been considered. 139 references.     

An iron(II) dihydrogen hydrido complex containing the tripodal tetraphosphine ligand P(CH2CH2PMe2)3

The dihydrogen hydrido complex [FeH(H2)(PP3)]+ 1 (PP3 = P(CH2CH2PMe2)3 2) was formed by the protonation of the dihydrido complex FeH2(PP3) 3 with methanol or ethanol. The observation of H-D coupling in partially deuterated isotopomers of 1 and measurement of T1 relaxation times for the hydrido and dihydrogen resonances of 1 confirmed the presence of the eta2-dihydrogen ligand. Complex 1 shows dynamic NMR behaviour in both the 31P and 1H NMR spectra with facile exchange between the protons in the eta2-dihydrogen ligand and the eta1-hydrido ligand. The dihydrogen ligand of 1 is easily displaced by both anionic and neutral ligands to afford the corresponding hydrido complexes [FeHX(PP3)]+ (X = CO 11, X = PPh3 12) or FeHX(PP3)(X = Cl 13, X = Br 14, X = I 15, X = N3 16). Small quantities of the alkoxy hydrido complexes FeH(OR)(PP3)(R = Me 4; R = Et 5) are observed in methanol and ethanol solutions containing 1. In methanol solution, FeH(OMe)(PP3) 4 reacts to form the carbonyl hydrido complex [FeH(CO)(PP3)]+ 11 and isotopic labelling confirms that the carbonyl ligand of 11 is derived from the methanol solvent. The mechanism of methanol oxidation presumably proceeds through beta-hydride elimination from FeH(OMe)(PP3) to produce formaldehyde as an intermediate which is further dehydrogenated to form the carbonyl ligand. [FeH(H2)(PP3)]+ 1 and FeHCl(PP3) 13 react rapidly with paraformaldehyde to also form [FeH(CO)(PP3)]+ 11. Complex 11 also decarbonylates acetaldehyde to afford the methyl carbonyl complex [FeMe(CO)(PP3)]+ 17. The structure of 17 was confirmed by X-ray crystallography.     

Synthesis, spectral, thermal, and a crystalline structure of complexes containing [MeC(CH2PPh2)3Cu(I)]

The preparation of new [MeC(CH₂PPh₂)₃CuCl] 1 and its derivatives was carried out directly by mixing of CuCl and MeC(CH₂PPh₂)₃ ligand in dry THF, the neutral precursor 1 served to prepare [MeC(CH₂PPh₂)₃Cu(NCCH₃)]BF₄ 2 and [MeC(CH₂PPh₂)₃Cu(PCH₂Ph)₃]BF₄ 3. These complexes are characterized on the basis of elemental analysis, IR, EDS, ¹H, ¹³C and ³¹P{¹H}NMR, FAB-MS, TG/DTA and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the Orthorhombic unit cells with the space group Pna2(1). The structural behavior of MeC(CH₂PPh₂)₃ ligand in the formed complexes during the coordination reaction was monitored by ³¹P{¹H}NMR in CDCl₃ at room temperature for the first time.     

Hydrogenation of Quinoline by Rhodium Catalysts Modified with the Tripodal Polyphosphine Ligand MeC(CH2PPh2)3

As part of our modelling studies of the hydrodenitrogenation of N‐heterocycles contained in raw oil materials, we investigated the selective hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline by rhodium catalysts modified with the tripodal polyphosphane ligand MeC(CH₂PPh₂)₃. Experiments in standard autoclaves and in high‐pressure sapphire NMR tubes, kinetic and isotope labelling studies, and independent reactions with isolated compounds have contributed to the elucidation of the catalytic mechanism as well as identification of the electronic requisites of the metal catalyst for selective and efficient hydrogenation.     

Aluminum(III), gallium(III), and indium(III) 4-hydroxyacridinato complexes

4-Hydroxyacridine (HAcr) is an O,N-chelating ligand whose coordination chemistry toward group 13 M(III) ions has received little attention. The molecular structure of HAcr consists of a 2,3-disubstituted-8-hydroxyquinoline; thus, in order to compare 8-hydroxyquinoline (HQ), 2-methyl-8-hydroxyquinoline (HMeQ′), and 2,3-disubstituted-8-hydroxyquinoline (HAcr) for steric and/or electronic influence, HAcr chelating ability toward the Al(III), Ga(III), and In(III) triad has been investigated. Irrespective of the nature of M(III), only complexes containing two equivalents of deprotonated HAcr are obtained. This article describes the synthesis and characterization of different series of bis-chelated pentacoordinated (Acr)₂MY (M = Al, Ga, In; Y = Cl, Br, I, NCS, N₃) or (Acr)₂MZ (M = Ga or In; HZ = C₆H₅OH, C₆H₁₃OC₆H₄OH, C₆H₅COOH, or C₆H₁₃OC₆H₄COOH) six-coordinate neutral (Acr)₂In(acac) (H(acac) =acetylacetone), or ionic [(Acr)₂In(N,N)][CF₃SO₃] (N,N = 2,2′-bipyridine or 1,10-phenanthroline) complexes. These results significantly contribute to elucidating the complexation capability of HAcr.     

Synthesis, properties, and structure of dimethylgold(III) complexes [(CH3)2AuI]2 and (CH3)2AuS2CN(C2H5)2

Volatile diethyldithiocarbamate of dimethylgold(III) was prepared by the interaction of dimethylgold(III) iodide with sodium diethyldithiocarbamate. The complex is examined by the elemental analysis, DTA, IR and electronic spectroscopy. The starting dimeric complex [(CH₃)₂AuI]₂ and a novel monomeric volatile gold(III) complex (CH₃)₂AuS₂CN(C₂H₅)₂ with the AuC₂S₂ coordination core were investigated by single crystal X-ray diffraction for the first time.     

Vanadium complexes of the N(CH2CH2S)3(3-) and O(CH2CH2S)2(2-) ligands with coligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.     

Structural and electronic behavior of unprecedented five-coordinate iron(III) and gallium(III) complexes with a new phenol-rich electroactive ligand

A new asymmetric pentadentate ligand was designed to impose low symmetry to trivalent ions. Five-coordinate Fe3+ and Ga3+ complexes were investigated by crystallographic, electrochemical, and electron paramagnetic resonance methods showing enhanced redox reversibility. Calculations were performed to account for the observed trends.     

Experimental infrared spectra of Cl-(ROH) (R = H, CH3, CH3CH2) complexes in the gas-phase

Infrared multiple photon dissociation spectra for the chloride ion solvated by either water, methanol or ethanol have been recorded using an FTICR spectrometer coupled to a free-electron laser, and are presented here along with assignments to the observed bands. The assignments made to the Cl(-)/H(2)O, Cl(-)(CH(3)OH), and Cl(-)(CH(3)CH(2)OH) spectra are based on comparison with the neutral H(2)O, CH(3)OH, and CH(3)CH(2)OH spectra, respectively. This work confirms that a band observed around 1400 cm(-1) in the Cl(-)(H(2)O) spectrum is not due to the Ar tag in Ar predissociation spectra. The carrier of this band is, most likely, the first overtone of the OHCl bend. Based on the position of the overtone in the IRMPD spectrum, 1375 cm(-1), the fundamental must occur very close to 700 cm(-1) and observation of this band should aid theoretical treatments of the spectrum of this complex. B3LYP/6-311++G(2df,2pd) calculations are shown to reproduce the IRMPD spectra of all three solvated chloride species. They also predict that attaching one or two Ar atoms to the Cl(-)(H(2)O) complex results in a shift of no more than a few wavenumbers in the fundamental bands for the bare complex, in agreement with previous experiment. For both alcohol-Cl(-) complexes, the S(N)2 "backside attack" isomers are not observed and Cl(-) is predicted theoretically, and confirmed experimentally, to be bound to the hydroxyl hydrogen. For Cl(-)(CH(3)CH(2)OH), the trans and gauche conformers are similar in energy, with the gauche conformer predicted to be thermodynamically favoured. The experimental infrared spectrum agrees well with that predicted for the gauche conformer but a mixture of gauche and anti conformers cannot be ruled out based on the experimental spectra nor on the computed thermochemistry.     

Thermal decomposition of di-t-butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals

A study of the reaction initiated by the thermal decomposition of di-t-butyl peroxide (DTBP) in the presence of (CH₃)₂C?CH₂ (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH₃ (M·), (CH₃)₂CCH₂CH₃ (MB·) and (CH₃)₂?CH₂C(CH₃)₂CH₂CH₃ (MBB·) radicals. The cross-combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively, where θ = RT ln 10 and the units are dm^3/2 mol^?1/2 s^?1/2 for k₂/k and k₉/k, s^?1 for k₀, and kJ mol^?1 for E. Various disproportionation-combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ₁(M·, MB·) = 0.79 ± 0.35, Δ₁(MB·, MB·) = 3.0 ± 1.0, Δ₁(MBB·, MB·) = 0.7 ± 0.4, Δ₁(M·, MBB·) = 4.1 ± 1.0, Δ₁(MB·, MBB·) = 6.2 ± 1.4, and Δ₁(MBB·, MBB·) = 3.9 ± 2.3, where Δ₁ refers to H-abstraction from the CH₃ group adjacent to the center of the second radical, yielding a 1-olefin. © 1994 John Wiley & Sons, Inc.     

Tris(difluoro and trifluorobutane-2,4-dionato) gallium(III) and indium(III) complexes

Eight tris(β-diketonate)gallium(III) and seven tris(β-diketonate)-indium(III) complexes M(RCOCH-COR′)₃, with R′being difluoromethyl and trifluoromethyl substituents and R′ being methyl, phenyl, aryl, 2′-naphthyl and 2′-thienyl substituents have been studied by nuclear magnetic resonance spectroscopy. The complexes are all nonrigid (fluxional) and their ¹⁹F NMR spectra show four resonances in the nonexchanging regions due to cis and trans isomers. A variable low temperature study of these complexes was done for the gallium chelates and activation parameters are calculated. The indium complexes all have nonexchanging regions below ?100°C. The ¹³C NMR data on the complexes are also reported.     

Synthesis of facial cyclometalated iridium(III) complexes triggered by tripodal ligands

The tripodal ligands composed of the 1,3,5-trisubstituted cyclohexyl moiety as a molecular scaffold and 2-phenylpyridyl moieties as a coordination site were designed. The homoleptic cyclometalated fac-Ir(C^N)(3) complexes could be obtained by the reaction of IrCl(3)·nH(2)O with the designed tripodal ligands. The single crystal X-ray structure determination confirmed the fac configuration and a distorted octahedral geometry with three intramolecular cyclometalated 2-phenylpyridyl ligands surrounding the iridium metal center. Also, the cyclohexyl scaffold was found to serve as a flexible scaffold to induce the fac configuration. The thus-obtained homoleptic cyclometalated fac-Ir(C^N)(3) complexes exhibited a broad emission band in the emission spectra at 298 K.     

Trigonal (-3) symmetry octahedral lanthanide(III) complexes of zwitterionic tripodal ligands: luminescence and magnetism

Sandwich coordination complexes, [Ln^III(H₃L)₂]X₃?solvents, of Tb(III), Eu(III), Dy(III), Ho(III) and Er(III) were prepared with two new zwitterionic ester-substituted tripodal amine ligands, tris((2-hydroxy-5-n-butyl benzoate)aminoethyl)-amine (H₃L¹) and tris((2-hydroxy-5-methyl benzoate)aminoethyl)-amine (H₃L²). These ligands were synthesised by condensation of the appropriately substituted salicylaldehyde with tris(2-aminoethyl)amine (tren) followed by in situ reduction of the tris-imine to tris-amine. Subsequent 2:1 reaction with lanthanide(III) ions yields [Ln^III(H₃L)₂]X₃?solvents (L = L¹, L²; X = Cl^?, NO₃^?; solvents = MeOH or H₂O). All complexes were characterised by microanalysis, infrared spectroscopy, high resolution mass spectrometry and solid-state photoluminescence measurements. The crystal structures of [Tb^III(H₃L¹)₂]Cl₃·6MeOH, [Dy(H₃L¹)₂]Cl₃·6MeOH, [Eu^III(H₃L¹)₂]Cl₃·6MeOH and [Tb^III(H₃L¹)₂](NO₃)₃ reveal high-crystallographic ?3 symmetry at the O₆-coordinated octahedral lanthanide(III) ions and that the tripodal ligands are bound in zwitterionic form: the protons from the phenolic oxygens have migrated to the amino nitrogens. Photoluminescence measurements indicate various degrees of energy transfer of the ligand chromophore to the lanthanide ions, as both ligand and lanthanide emission features are observed. Despite the high-crystallographic symmetry and the likely small transverse magnetic anisotropy of the complexes, no evidence of slow relaxation of the magnetisation, characteristic of a single-molecule magnet, was observed for [Tb^III(H₃L¹)₂]Cl₃·MeOH·3H₂O, [Dy^III(H₃L¹)₂]Cl₃·6H₂O, [Ho^III(H₃L¹)₂](NO₃)₃·2H₂O, [Er^III(H₃L¹)₂]·H₂O and [Tb^III(H₃L¹)₂](NO₃)₃ down to 2.0 K.     

Density functional description of the early stages of the dioxygenation of [(MeC(CH2PPh2)3)M(catecholate)]+ complexes [M = Co(III), Ir(III)]: toward a rationalization of the catalytic mechanism of ring-opening dioxygenases

Density Functional Theory (DFT) has been applied to characterize the early stages of the reaction of dioxygenation of [(triphos)M(catecholate)]+ complexes [M = Co(III), Ir(III); triphos = MeC(CH2PPh2)3], which have been considered to be models of ring-opening dioxygenases. The structural features of the starting complexes and of the intermediate complexes formed by addition of O2 to the coordinated catecholato ion are well reproduced. The calculations showed that this preliminary stage can be obtained only when the oxygen molecule attacks the molecule on the catecholato site.     

New superhindered polydentate polyphosphine ligands P(CH2CH2P(t)Bu2)3, PhP(CH2CH2P(t)Bu2)2, P(CH2CH2CH2P(t)Bu2)3, and their ruthenium(II) chloride complexes

The synthesis and characterization of the extremely hindered phosphine ligands, P(CH(2)CH(2)P(t)Bu(2))(3) (P(2)P(3)(tBu), 1), PhP(CH(2)CH(2)P(t)Bu(2))(2) (PhP(2)P(2)(tBu), 2), and P(CH(2)CH(2)CH(2)P(t)Bu(2))(3) (P(3)P(3)(tBu), 3) are reported, along with the synthesis and characterization of ruthenium chloro complexes RuCl(2)(P(2)P(3)(tBu)) (4), RuCl(2)(PhP(2)P(2)(tBu)) (5), and RuCl(2)(P(3)P(3)(tBu)) (6). The bulky P(2)P(3)(tBu) (1) and P(3)P(3)(tBu) (3) ligands are the most sterically encumbered PP(3)-type ligands so far synthesized, and in all cases, only three phosphorus donors are able to bind to the metal center. Complexes RuCl(2)(PhP(2)P(2)(tBu)) (5) and RuCl(2)(P(3)P(3)(tBu)) (6) were characterized by crystallography. Low temperature solution and solid state (31)P{(1)H} NMR were used to demonstrate that the structure of RuCl(2)(P(2)P(3)(tBu)) (4) is probably analogous to that of RuCl(2)(PhP(2)P(2)(tBu)) (5) which had been structurally characterized.     

Structural diversity in dinickel(II) complexes of thiosemicarbazones

2,6-Diformyl-p-cresol serves as a starting point for the generation of multidentate N/O/S chelating agents. Condensation with 4-(X-phenyl) thiosemicarbazide yields the pentadentate ligand having SNONS donor sequences, capable of holding two metal ions in close proximity. The ligands behave as mono/di/tri basic depending on the pH of the medium. Stereochemical diversity in the reaction product of such ligands with nickel(II) chloride at different pH is observed. Sterically demanding substituted ligands in association with various exogenous bridges dictate the geometry and coordination number of such complexes. The compounds were investigated by elemental analysis, molar conductivities, electronic spectra, IR, NMR, FAB mass spectra, TG-DTG, magnetic susceptibility measurements. Varieties of geometries such as square planar, square pyramidal, octahedral and square planar–square pyramidal are observed. Cryomagnetic data for the complexes (79–296 K) can be reproduced by an equation based on the Heisenberg model (H=−2JS₁S₂, S₁=S₂=1). The singlet–triplet splitting, J varies systematically with the coordination geometry about the Ni₂(SNONS) core, with the hydroxo bridged complex exhibiting the greatest degree of antiferromagnetic coupling. The coupling is somewhat weaker for the chloro-bridged complexes. None of the complexes have shown any appreciable antimicrobial activity.     

Extraction-spectrophotometric investigations on two ternary ion-association complexes of gallium(III)

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions w.r.t. pH, extraction time, concentration of ADR and concentration of TTC for the extraction of Ga(III) as an ion-associate complex were found.. The composition of the extracted complexes, (TT⁺)[Ga(PAR)₂] (I), (TT⁺)[Ga(TAR)₂] (II) or (TT⁺)₂[Ga(OH)(TAR)₂] (III), and the constants of association (β) between 2,3,5-triphenyltetrazolium cation (TT⁺) with corresponding anionic chelates were established by several methods. The constants of distribution (K_D) and extraction (K_ex) of the principal species I and III were determined as well. The apparent molar absorptivities of the chloroform extract at the optimum extraction-spectrophotometric conditions were ɛ′₅₁₀=9.5×10⁴ L mol⁻¹ cm⁻¹ (I) and ɛ′₅₃₀=4.6×10⁴ L mol⁻¹ cm⁻¹ (III). The validity of Beer’s law was checked and analytical characteristics that were calculated are reported herein.