Thermochromism in nickel(II) complexes: thermal, solid state H NMR and single crystal X-ray analysis of bis-(N,N-dimethyl-1,2-ethanediamine) nickel(II) perchlorate

The complex bis-(N,N-dimethyl-1,2-ethanediamine) nickel(II) perchlorate undergoes a first-order thermochromic phase transition at ca. 476 K, changing its color from orange to red. The room temperature X-ray crystal structure determination showed that the nickel ion possesses a square-planar geometry with two five membered chelate rings, in the δλ conformation, forming the NiN₄ chromophore. The broad-line ¹H NMR indicates the onset of a dynamic disorder of diamine chelate rings at the phase transition temperature region, while T₁ measurement of ¹H affords the activation energy of the puckering metal chelate rings to be 26 kJ mol⁻¹. The electronic spectrum revealed that a weakening of ligand field around the nickel is associated with the phase transition.     

Complete 1H, 13C{1H}, and 31P NMR spectral parameters of some pyrophosphates

The ¹H, ¹³C{¹H}, and ³¹P NMR spectral parameters of some pyrophosphates were determined in CDCl₃. The most complicated ¹H spectrum can be solved fully only as (A₃MN)R₆XX′R₆′(MNA₃)′, where R₆ (= ―N(CH₃)₂) is coupled only to phosphorus (X). Second‐order coupling between phosphorus was found and solved with iterative analysis. A signal shape of one of the carbon resonance cannot be explained only with couplings. Explanation for exceptional shape was searched from molecular modeling results. Copyright © 2017 John Wiley & Sons, Ltd.     

31P-{1H} NMR spectra of some o-tolylbis (triphenylphosphine)nickel derivatives

Conclusion ³¹P NMR spectroscopy was used to show that o-tolylbis(triphenylphosphine)nickel carboxylates may exist in solution in two forms. A study of the exchange reactions of these complexes with triphenylphosphine indicated that the difference between these forms is a consequence of the chelation or lack of chelation of the nickel atom with the carboxylate group oxygen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1028–1031, May, 1988.     

1H, 13C and 31P NMR spectral analysis of monoalkyl (α‐anilinobenzyl)phosphonates and their dipalladium(II) metallocyclic complexes

A ¹H, ¹³C and ³¹P NMR study of monoethyl (HL1) and monobutyl (HL2) esters of (α‐anilinobenzyl)phosphonic acid and their metallocyclic dipalladium complexes (Pd₂L₄,L = L1, L2) in DMSO‐d₆ was performed, based on 1D and 2D homo‐ and heteronuclear experiments including ¹H,¹³C,³¹P,APT,¹H–¹H COSY, ¹H–¹³C COSY, gs‐HMQC and gs‐HMBC NMR techniques. The results obtained are discussed with respect to those for some palladium(II) complexes reported for various anilinobenzylphosphonate derivatives. Copyright © 2002 John Wiley & Sons, Ltd.     

187Os subspectra in 1H and 31P{1H} spectra of triosmium carbonyl clusters

A survey of the use of ¹⁸⁷Os satellite subspectra in ¹H and ³¹P{¹H} spectra of triosmium carbonyl clusters is reported. By varying evolution delays in HMQC spectra of [Os₃(µ‐H)₂(CO)₁₀] we have selectively extracted the values for ¹J(Os,H) and ²J(Os,H), respectively. An analysis of the principal modes of phosphine coordination in triosmium clusters demonstrates that ³¹P{¹H}¹⁸⁷Os satellite subspectra are diagnostic for equatorial coordination [¹J(Os,P) = 211–223 Hz] or for axial coordination (perpendicular to the plane of the cluster) [¹J(Os,P) ≈ 147 Hz]. Chelating and bridging diphosphines yield ¹⁸⁷Os satellite subspectra which are the sum of A₂X and AA′X spin systems. If significant P–P coupling is present, the AA′X component requires simulation. All observed ²J(Os,P) trans‐equatorial couplings fall in the range 38–65 Hz. Copyright © 2001 John Wiley & Sons, Ltd.     

Aminomethylphosphine Oxides: Synthesis,dissociation and stability constants, 31P{1H}-NMR-controlled titrations

The title compounds are prepared via Gabriel-synthesis following known or improved procedures. Novel methods using ³¹P{¹H}-NMR controlled titrations of aminomethylphosphine oxides lead to dissociation constants (given as basicity or acidity constants resp.) and to stability constants. Dynamically averaged and ion specific chemical shifts δ_P were derived.     

Reactions of alkynes with bis(triphenylphosphine)platinum-ethylene: A 31P-{1H} NMR study

Internally consistent assignments of the ³¹P-{¹H} NMR parameters of the complexes [Pt(RCCR′)(PPh₃)₂] are proposed, based on the premise that the magnitude of ¹J(PtP) depends mainly on the nature of the moiety CR trans to P. For a given R, ²J(PP) correlates with ¹J(PtP) for thebond trans to CR. The alkynes PhCCSnEt₃, PhCCSnPh₃, Me₃SiCCCl, Me₃SiCCBr, Et₃SiCCI and MeCCI undergo oxidative addition reactions with [Pt(C₂H₄)(PPh₃)₂]; the intermediate alkyne complex was detected for PhCCSnEt₃, Me₃SiCCCl and Me₃CCBr. The triyne Me(CC)₃Me forms platinum(0) complexes by coordination with the central or terminal CC bond and appears also to give a platinum(II) complex by oxidative addition.     

A 31P CP/MAS NMR study of PbS surface O,O'-dialkyldithiophosphate lead(II) complexes

31P CP/MAS NMR spectroscopy was used to study the adsorption of six different O,O'-dialkyldithiophosphate ions on the surface of synthetic galena (PbS). The 31P CP/MAS NMR spectra of the surface lead(II) dithiophosphates were compared with the 31P CP/MAS NMR spectra of polycrystalline lead(II) dithiophosphate complexes of the same ligands. Surface complexation of the dialkyldithiophosphate ions was established on the surface of PbS. A terminal S,S(')-chelating coordination is suggested for the surface complexes. The bulkier alkyl groups lead to surface precipitation in addition to the surface adsorption. Derivatives of monothiophosphoric and phosphoric acids were displayed as hydrolysis products of dialkyldithiophosphates on the synthetic PbS, the amount of which depends on the type of alkyl group.     

Crystalline O,O′-di-sec-butyl and O,O′-diethyl dithiophosphate platinum(II) complexes: Synthesis, C and P CP/MAS NMR, single crystal X-ray diffraction studies and thermal behaviour

Crystalline bis(O,O′-di-sec-butyldithiophosphato)platinum(II) was prepared and studied by means of ¹³C, ³¹P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. The unit cell of the platinum(II) compound is comprised of one centrosymmetric mononuclear molecule [Pt{S₂P(O-sec-C₄H₉)₂}₂], in which the dithiophosphate groups display structural equivalence in both ³¹P NMR and XRD data. A pair of the dithiophosphate ligands exhibit the same S,S′-bidentate chelating structural function and form two planar four-membered chelate rings, [PtS₂P], in this molecule. The planar configuration of the [PtS₄] chromophore in structure 1 is governed by the dsp²-hybrid state of platinum(II). The structural states of the dithiophosphate groups in two different samples of complex 1 (one crystallised from ethanol and the other one precipitated from an aqueous solution) are all characterised by almost rhombic ³¹P chemical shift tensors. The observed essential dispersion of the ³¹P NMR chemical shift is caused by a coexistence of six optical isomers of molecule 1. The thermal behaviour of this compound was studied by means of simultaneous thermal analysis (a combination of TG and DSC) under an argon atmosphere. The thermal behaviour shows that the mass of 1 is lost in three steps, involving successive thermal decompositions of the organic and inorganic parts of this compound with platinum(II) dithio-meta-phosphate and reduced metallic platinum as the intermediate and the final products, respectively.     

Efficient alkylation of ketones with primary alcohols catalyzed by ruthenium(II)/P,N ligand complexes

An efficient catalytic system containing [RuCl₂(η⁶-p-cymene)]₂ and one P,N ligand, N-diphenylphosphino-2-aminopyridine (L1) was loaded in catalyzing the alkylation of ketones with primary alcohols for a diverse array of substrates. Other five P,N ligands based on pyridin-2-amine and pyrimidin-2-amine were also examined in this reaction to explore the influence of steric hindrance and electronic effects. Monitoring by ¹H NMR and ESI-MS reveals a stable cationic L1-coordinated ruthenium hydride intermediate, identified as [Ru(η⁶-p-cymene)(κ²-L1)H]⁺. Organic intermediates consistent with a three-step dehydrogenation, alkylation and hydrogenation pathway were also observed. The final step in this reaction, the ruthenium-catalysed transfer hydrogenation reduction of α,β-unsaturated ketone with benzyl alcohol was performed separately.     

1,10-(phenanthroline)-bis{1-alkyl-2-(arylazo)imidazole} ruthenium(II) perchlorate: Synthesis,spectral study,and electrochemistry

The hetero-tris-chelates of the formula [Ru(Phen)(RAaiR′)₂](ClO₄)₂ (Phen = 1,10-phenanthroline, RAaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C₆H₄-N=N-C₃H₂-NN-1-R′, where R = H (a), Me (b), Cl (c) and R′ = Me (II), Et (III), CH₂Ph (IV)) have been isolated from the reaction of ctc-[RuCl₂(RAaiR′)₂] with AgNO₃ + Phen or [Ag(Phen)₂](ClO₄) in acetone at 40°C in dark followed by the addition of NaClO₄ (aq). The stereo-chemistry of the complexes have been supported by ¹H NMR data. Considering the arylazoimidazole and phenanthroline moietie there are twenty different carbon atoms in the molecule which gives a total of twenty different peaks in the ¹³C NMR spectrum of complex Ia. Cyclic voltammograms show Ru(III)/Ru(II) couple at 1.3–1.4 V vs SCE along with three successive ligand reductions. The article is published in the original.     

Synthesis,characterization and crystal structure of ruthenium(II) polypyridyl complexes

[Ru(bipy)2(5-R-phen)](ClO4)2 complexes have been prepared, where bipy=2,2- bipyridine, phen=1,10-phenanthroline, and R=H, Me, NO2 or NH2. The influence of the different 5- substituted phen on the electron delocalization and ligand-ligand interactions have been investigated by solution n.m.r.. The ligand- ligand interaction has also been observed in the solid state by determining the single crystal structure of [Ru(bipy)2(5- NO2-phen)](ClO4)2. The strong steric interaction between the polypyridyl ligands was relieved neither by the elongation of Ru–N bonds (2.055–2.086Å) nor by increase of N–Ru–N bite angles (77.8–79.4°), but rather by distortion of the coordination sphere by forming specific angles (=2.0, 3.2 and 4.2°) between the polypyridyl ligand planes and coordination planes (N–Ru–N), and larger torsion angles (5.8 and 8.2°) between the two pyridine rings for each bipy.     

Synthesis and multinuclear NMR study of Hg(II), Cd(II), and Pd(II) complexes with biphenylmethylenetriphenylphosphorane: X-ray crystal structure of [{C6H5C6H4CO{(C6H5)3P}CH}HgI2]2

Reactions of title ylide, {(C₆H₅)₃PCHCOC₆H₄C₆H₅)} (BPPPY), with mercury(II) halides in equimolar ratios in methanol yielded dinuclear complexes [(BPPPY)HgCl₂]₂ (1), [(BPPPY)HgBr₂]₂ (2), and [(BPPPY)HgI₂]₂ (3). Reactions of BPPPY with CdCl₂ in equimolar ratios gave [(BPPPY)CdCl₂]₂ (4). Reaction of PdCl₂ with BPPPY (1/2) in acetonitrile at room temperature gave cis/trans [PdCl₂{CH(PPh₃)COC₆H₄C₆H₅}₂] (5). The same reaction at reflux gave the orthopalladated complex [Pd{CH{P(2-C₆H₄)Ph}(COC₆H₄C₆H₅)}(μ-Cl)]₂ (6) along with the phosphonium salt [Ph₃PCHCOC₆H₄C₆H₅]Br. The compounds were characterized by elemental analysis, IR-, ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. Single crystal X-ray analysis of 3 reveals the centrosymmetric dimeric structure containing the ylide and HgI₂. Crystallographic data for 3 are: crystal system, monoclinic; space group, P 2₁/n, a = 15.7744(7), b = 23.0288(9), c = 20.2867(9) Å, β = 112.237(3)°, V = 6821.4(5) ų, and Z = 1.     

Synthesis,spectral, and catalytic studies of ruthenium(II) unsymmetrical Schiff-base complexes

Unsymmetrically-substituted ruthenium(II) Schiff-base complexes, [Ru(CO)(B)(L ^x )] [B = PPh₃, AsPh₃ or Py; L ^x = dianion of tetradentate unsymmetrical Schiff-base ligand; x = 4–7, L⁴ = salen-o-hyac, L⁵ = valen-o-hyac, L⁶ = salphen-o-hyac, L⁷ = valen-2-hacn], were prepared and characterized by analytical, IR, electronic, and ¹H NMR spectral studies. The new complexes were tested for their catalytic activity towards the oxidation of benzylalcohol to benzaldehyde.     

(1)H-NMR study of ternary platinum(II) complexes with N-(1-Naphtyl)methyl-1,2-ethanediamine or N-(9-anthrylmethyl)-1,2-ethanediamine and bipyridine or phenanthroline and restricted single bond rotation due to aromatic-aromatic ring interaction

(1)H-NMR spectra of square-planar complexes with the formula [Pt(L(1))(L(2))]X(2) where L(1) is 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) and L(2) is N-(1-naphthyl)methyl-1,2-ethanediamine (Npen) or N-(9-anthryl)methyl-1,2-ethanediamine (Aten) indicate that the N-naphthylmethyl and N-anthrylmethyl groups are forced to adopt a pseudo axial disposition due to intramolecular repulsion of hydrogen atoms of the aromatic diimines. The aromatic-aromatic interactions in the N-arylmethyl-1,2-ethanediamine complexes and aromatic diimines caused them to undergo intramolecular stacking. (1)H-NMR spectra of these complexes showed a significant concentration and temperature dependence. The monomer-dimer equilibrium was estimated, based on the concentration dependency. Restricted single bond rotation was estimated from temperature dependency data. The rotation of the anthracene ring of the [Pt(bpy)(Aten)](2+) complex showed an activation energy of ca. 38 kJ mol(-1), which is in good agreement with a mechanism involving successive rotations about single bonds with restriction by intramolecular aromatic-aromatic ring interactions.     

Copper(II) and cadmium(II) complexes of 2-benzylthio-4-formyl-1-p-methoxyphenylimidazole: crystal structure,spectral properties and thermal behaviour

Summary The coordinative capacity of 2-benzylthio-4-formyl-1-p-methoxyphenylimidazole (ALME) with several transition metal ions has been investigated and has led to only copper(II) and cadmium(II) complexes of general formula [M^IICl₂(ALME)₂]·nH₂O. These compounds were studied by spectral (i.r., u.v.-vis. n.i.r. and e.p.r.) and thermal methods (t.g., d.t.g. and d.s.c.) as well as magnetic susceptibility measurements.The crystal structure of the copper complex has been solved, although a full refinement of the structure has not been possible as very few measured reflections were observed. The structure consists of discrete [CuCl₂-(ALME)₂] units in which Cu(II) ion is 4 + 2 Cl₂N₂O₂ surrounded [Cu{ie481-01}Cl(1), 2.28(1) Å; Cu{ie481-02}Cl(2), 2.29(1) Å; Cu{ie481-03}N, 2.00(2) Å; Cu{ie481-04}O, 2.71(2) Å]. The ALME ligand acts as bidentate chelator through the N(3) imidazolic atom and the oxygen of the formyl group, the Cu{ie481-05}O interaction being very weak. Water molecules have not been localized.