Hydrothermal synthesis and crystal structure of [Ni(Bptc)<Subscript>2</Subscript>(Bimb)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]

In the compound [Ni(Bptc)₂(Bimb)₂(H₂O)₂] (I), where H₄Bptc is 3,3′,4,4′-biphenyltetracarboxylic acid; Bimb is 4,4′-bis(1-imidazolyl)biphenyl), Ni(II) has a distorted octahedral coordination geometry, which was bonded with two N atoms from two Bimb ligands, two O atoms from two H₂Bptc²⁻ ligands and two water O atoms. The crystal structure of compound I is stabilized by the π-π-stacking and hydrogen bonds interaction.     

Standard molar enthalpies of formation of [RE(Gly)<Subscript>4</Subscript>(Im)(H<Subscript>2</Subscript>O)](ClO<Subscript>4</Subscript>)<Subscript>3</Subscript> (<Emphasis Type="Italic">RE</Emphasis>=Eu,Sm)

The two complexes, [RE(Gly)₄(Im)(H₂O)](ClO₄)₃(s)(RE = Eu, Sm), have been synthesized and characterized. The standard molar enthalpies of reaction for the following reactions, RECl₃·6H₂O(s)+4Gly(s)+Im(s)+3NaClO₄(s) = =[RE(Gly)₄(Im)(H₂O)](ClO₄)₃(s)+3NaCl(s)+5H₂O(l), were determined by solution-reaction colorimetry. The standard molar enthalpies of formation of the two complexes at T = 298.15 K were derived as Δ_f H _m^Θ {Eu(Gly)₄(Im)(H₂O)}(ClO₄)₃(s)} = = −(3396.6±2.3) kJ mol⁻¹ and Δ_f H _m^Θ {Sm(Gly)₄(Im)(H₂O)}(ClO₄)₃(s)} = −(3472.7±2.3) kJ mol⁻¹, respectively.     

Synthesis of Pd(II) complexes containing the protonated form or molecule of 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline (L). The crystal structure of [Pd(HL)Cl<Subscript>3</Subscript>]

The diamagnetic complexes [Pd(HL)Cl₃](I) and PdLCl₂(II), where L is 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline, were obtained. According to X-ray diffraction data, the crystal structure of complex I consists of mononuclear acentric molecules. The coordination polygon PdNCl₃ is a distorted square (trapezium) made up of the pyrazole N atom of the monodentate ligand (cation HL⁺) and three Cl atoms. Complex II seems to contain the square polygon PdN₂Cl₂.     

Reaction of Sulfur and Oxygen-Bridged 8-Quinolinolato Trinuclear Molybdenum Cluster [Mo<Subscript>3</Subscript>OS<Subscript>3</Subscript>(qn)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>]<Superscript>+</Superscript> with Acetylene Carboxylic Acids

The reaction of a sulfur and oxygen-bridged 8-quinolinolato trinuclear molybdenum cluster [Mo₃OS₃(qn)₃(H₂O)₃]⁺ (3; Hqn = 8-quinolinol) with equimolar amounts of acetylene carboxylic acid, 4-pentynoic acid, 5-hexynoic acid, acetic acid, and pimelic acid gave clusters having μ-carboxylato groups, [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡CCOO)] (6), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₂COO)] (7), [Mo₃OS₃(qn)₃(H₂O)(μ-HC≡C(CH₂)₃COO)] (8), [Mo₃OS₃(qn)₃(H₂O)(μ-CH₃COO)] (4), and [{Mo₃OS₃(qn)₃(C₂H₅OH)}₂(μ-C₇H₁₀O₄)] (5), respectively. X-ray structural analyses, ¹H NMR, and electronic spectra of these clusters made clear that each of the COO⁻ groups of the reagents bridges two Mo atoms in each cluster and that no adduct formation occurred at the sulfurs in the clusters. The reaction of 3 with a large excess-molar amount (50 times) of acetylene carboxylic acid gave [Mo₃OS(μ₃-SCH=C(COOH)S)(qn)₃(H₂O)(μ-HC≡CCOO)] (9) with two molecules of acetylene carboxylic acid, one acting as a carboxylato bridge and the other in adduct formation, as supported by the electronic and ¹H NMR spectra. The corresponding aqua cluster [Mo₃OS₃(H₂O)₉]⁴⁺ (1), on the contrary, reacts with acetylene carboxylic acid to give adduct [Mo₃OS(μ₃-SCH=C(COOH)S)(H₂O)₉]⁴⁺ (2). Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Formation of Cu<Superscript>I</Superscript>(CH<Subscript>3</Subscript>CN)<Subscript>4</Subscript>ClO<Subscript>4</Subscript> in the reactions of copper(II) perchlorate with acetonitrile in the presence of sulfur-containing organic compounds

Cu(ClO₄)₂·6H₂O was shown to react with 2,2′-[propane-1,3-diylbis(thio-2-phenylnemethylidene]-bis(3-pyridylamine) (I) or (5Z)-2-ethoxycarbonylmethyl-(2-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-one (II) in the presence of CH₃CN with the reduction of copper(II) to copper(I) and the formation of the tetrahedral complex Cu^I(CH₃CN)₄ClO₄ (III). In the course of the reaction the organic ligands I and II were oxidized to the corresponding sulfoxides.     

Synthesis,crystal structure and magnetic properties of the complex Co[Me<Subscript>2</Subscript>NC(S)NP(S)(OPr-<Emphasis Type="Italic">i</Emphasis>)<Subscript>2</Subscript>]<Subscript>2</Subscript>

The reaction of N-(diisopropoxyphosphorothioyl)-N′,N′-dimethylthiourea [Me₂NC(S)NHP(S)(OPr-i)₂, HL) potassium salt with Co(II) cation in aqueous ethanol gave the chelate complex Co(L-S,S′)₂(CoL₂). The structure of the resulting compound was studied by means of IR spectroscopy, microanalysis, and X-ray analysis. The metal center was found to occur in a tetrahedral S₄ environment formed by the C=S and P=S sulfur atoms of two deprotonated ligands L. Magnetic properties of the complex CoL₂ were also studied.     

Synthesis and crystal structure of complex of Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript> with N-(3-methyl-pyridin-2-yl)-formimidoyl-(3-methyl-pyridin-2-yl) hydrazone

The reaction of 3,6-di-(3-methyl-pyridin-2-yI)-s-tetrazine (DMPTZ, II) with Ce^III salt [Ce(NO₃)₃ · 6H₂O] generates a new ligand, N-(3-methyl-pyridin-2-yl)-formimidoyl-(3-methyl-pyridin-2-yl) hydrazone (L), and forms a new complex: a mononuclear complex [Ce(L)(NO₃)₂ (H₂O)₃] · NO₃ (III). Crystal data for III: space group P-1, with a = 0.7133(4) nm, b = 1.1139(2) nm, c = 1.4572(3) nm, α= 102.13(2)°, β= 99.81(3)°, γ= 91.10(3)°, Z = 2, V = 1113.6(7) nm³, μ = 2.123 mm⁻¹ and F(000) = 630. L acts as a tri-dentate chelating ligand in III. There are 10 coordination sites around Ce³⁺ of III, which are respectively occupied by seven oxygen atoms (four from two nitrate anions and three from three H₂O molecules) and three nitrogen atoms (all from L). The cerium atom and three chelating nitrogen atoms are coplanar. The mechanism of the metal assisted decomposition is discussed briefly.     

A study of complexation between crystalline <Emphasis Type="Italic">trans</Emphasis>-[Pd(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>] and acetylacetone

Complexation between crystalline trans-[Pd(H₂O)₂(NO₃)₂] and acetylacetone was studied. The complexes Pd₂(Acac)₂(μ-NO₃)₂(I) and Pd₂(Acac)₂(μ-Acac)(μ-NO₃)(II) were obtained and examined by elemental analysis, X-ray powder diffraction analysis, differential scanning calorimetry, simultaneous thermal analysis, mass spectrometry, and vibrational spectroscopy.     

Synthesis and structural characterization of a novel trinickel cluster: {[Ni(H<Subscript>2</Subscript>L)(EtOH)]<Subscript>2</Subscript>(OAc)<Subscript>2</Subscript>Ni} · 2EtOH

A novel trinuclear Ni^II cluster, {[Ni(H₂L)(EtOH)]₂(OAc)₂Ni} · 2EtOH [H₄L:5,5′-Dihydroxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol], has been synthesized and structurally characterized. The X-ray crystal structure of the cluster reveals that two acetates coordinate to three nickel ions through Ni–O–C–O–Ni bridges and four μ-phenoxo oxygen atoms from two [Ni(H₂L)] units also coordinate to nickel ions. Around three nickel atoms are all octahedral geometries.     

Structure and properties of H<Subscript>8</Subscript>(PW<Subscript>11</Subscript>TiO<Subscript>39</Subscript>)<Subscript>2</Subscript>O heteropoly acid

Heteropoly acid (HPA) H₈(PW₁₁TiO₃₉)₂O·xH₂O (I) is synthesized by three different ways and studied by chemical analysis, potentiometric titration, mass-spectrometry, IR, ³¹P, ¹⁸³W, and ¹⁷O NMR spectroscopy, thermogravimetry, and transmission electron microscopy. Anion I consists of two subparticles of the Keggin structure bridged by Ti-O-Ti. The dimeric anion exists in HPA aqueous solutions at [I] > 0.02 M. At pH > 0.6 it splits to a [PW₁₁TiO₄₀]⁵⁻ monomer stable up to pH ∼ 6. When heated (150–400)°C, I splits into H₃PW₁₂O₄₀ and, apparently, H₃PW₁₀Ti₂O₃₈ without phase separation. Thermolysis products are soluble and when dissolved in water turn again into I. Complete decomposition of I to oxides occurs at ∼450°C.     

Synthesis and characterization of the [Ru<Subscript>3</Subscript>O(CH<Subscript>3</Subscript>COO)<Subscript>6</Subscript>(py)<Subscript>2</Subscript>(BPE)Ru(bpy)<Subscript>2</Subscript>Cl](PF<Subscript>6</Subscript>)<Subscript>2</Subscript> dimer

The polymetallic [Ru₃O(CH₃COO)₆(py)₂(BPE)Ru(bpy)₂Cl](PF₆)₂ complex (bpy = 2,2′-bipyridine, BPE = trans-1,2-bis(4-pyridil)ethylene and py = pyridine) was assembled by the combination of an electroactive [Ru₃O] moiety with a [Ru(bpy)₂(BPE)Cl] photoactive centre, and its structure was determined using positive ion electrospray (ESI-MS) and tandem mass (ESI-MS/MS) spectrometry. The [Ru₃O(CH₃COO)₆(py)₂(BPE)Ru(bpy)₂Cl]²⁺ doubly charged ion of m/z 732 was mass-selected and subject to 15 eV collision-induced dissociation, leading to a specific dissociation pattern, diagnostic of the complex structure. The electronic spectra display broad bands at 409, 491 and 692 nm ascribed to the [Ru(bpy)₂(BPE)] charge-transfer bands and to the [Ru₃O] internal cluster transitions. The cyclic voltammetry shows five reversible waves at −1.07 V, 0.13 V, 1.17 V, 2.91 V and −1.29 V (vs SHE) assigned to the [Ru₃O]^{−1/0/+1/+2/+3} and to the bpy^0/−1 redox processes; also a wave is observed at 0.96 V, assigned to the Ru^+2/+3 pair. Despite the conjugated BPE bridge, the electrochemical and spectroelectrochemical results indicate only a weak coupling through the π-system, and preliminary photophysical essays showed the compound decomposes under visible light irradiation.     

Synthesis,structure, and NO-donor activity of the paramagnetic complex [Fe<Subscript>2</Subscript>(SC<Subscript>3</Subscript>H<Subscript>5</Subscript>N<Subscript>2</Subscript>)<Subscript>2</Subscript>(NO)<Subscript>4</Subscript>] as a model of nitrosyl [2FE-2S] proteins

The neutral dinuclear iron nitrosyl complex [Fe₂(SC₃H₅N₂)₂(NO)₄] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction of the thiosulfate ligands in the [Fe₂(S₂O₃)₂(NO)₄]²⁻ anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μ_B and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007.     

New uranyl complex with imidazolidine-2-one [UO<Subscript>2</Subscript>(Imon)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)](ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>: Structure and some properties

A complex of uranyl perchlorate with imidazolidine-2-one as the molecular ligand, [UO₂(Imon)₄(H₂O)](ClO₄)₂ (I), was synthesized and structurally characterized by X-ray diffraction analysis. The coordination number of the uranium atom is 7. The nearest environment of the uranyl ion includes four O atoms of the imidazolidine-2-one molecules and one O atom of the water molecule. The perchlorate anions are outer-sphere ligands. The crystals are monoclinic: space group P2₁/c; a = 16.294(3) Å, b = 16.135(3) Å, c = 9.987(2) Å, = 97.69 (3)°, V = 2603.0 (9) ų, (calcd) = 2.117 g/cm³, Z = 4. The IR and luminescence spectra of the complex were recorded.Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 919–924.Original Russian Text Copyright © 2004 by Andreev, Antipin, Budantseva, Tuchina, Serezhkina, Fedoseev, Yusov.     

Synthesis,structure, and electrochemistry of <Emphasis Type="Italic">trans</Emphasis>-[Co<Superscript>III</Superscript>{(BA)<Subscript>2</Subscript>pn}(L)<Subscript>2</Subscript>]ClO<Subscript>4</Subscript> complexes

The structure, spectroscopic, and electrochemical properties of [Co{(BA)₂pn}(L)₂]ClO₄ complexes, where (BA)₂pn = N,N′-bis(benzoylacetone)-1,3-propylenediimine dianion and the two ancillary ligands (L) are pyridine, py (1), and 4-methylpyridine, 4-Mepy (2), have been investigated. These complexes have been characterized by elemental analyses, IR, UV–Vis and ¹H-NMR spectroscopy. The crystal structure of [Co{(BA)₂pn}(py)₂]ClO₄ (1) has been determined by X-ray diffraction. The coordination geometry around cobalt(III) is best described as a distorted octahedron. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Co^III–Co^II is electrochemically irreversible, which is accompanied by the dissociation of the axial N(py)–cobalt bonds. This process becomes quasi-reversible upon the addition of excess py ligands. The second reduction step of Co^II/I shows reversible behavior and is not influenced by the nature of the axial ligands. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Reactivity of triangular oxalate cluster complexes [M<Subscript>3</Subscript>Q<Subscript>7</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>3</Subscript>]<Superscript>2−</Superscript> (M = Mo or W; Q = S or Se)

The reactions of the oxalate complexes [M₃Q₇(C₂O₄)₃]²⁻ (M = Mo or W; Q = S or Se) with Mn^II, Co^II, Ni^II, and Cu^II aqua and ethylenediamine complexes in aqueous and aqueous ethanolic solutions were studied. The previously unknown heterometallic complexes [Mo₃Se₇(C₂O₄)₃Ni(H₂O)₅]·3.5H₂O (1) and K₃{[Cu(en)₂H₂O]([Mo₃S₇(ox)₃]₂Br)}·5.5H₂O (2) were synthesized. In these complexes, the oxalate clusters serve as monodentate ligands. The K(H₂en)₂[W₃S₇(C₂O₄)₃]₂Br·4H₂O salt (3) was isolated from solutions containing Co^II, Ni^II, or Cu^II aqua complexes and ethylenediamine. The reaction of [Mo₃Se₇(C₂O₄)₃]²⁻ with HBr produced the bromide complex [Mo₃Se₇Br₆]²⁻, which was isolated as (Bu₄N)₂[Mo₃Se₇Br₆] (4). Complexes 1–3 were characterized by X-ray diffraction, IR spectra, and elemental analysis. The formation of 4 was detected by electrospray mass spectrometry. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1645–1649, September, 2007.     

Synthesis,crystal structure,and biological properties of the complex [Co(DmgH)<Subscript>2</Subscript>(Seu)<Subscript>1.4</Subscript>(Se-Seu)<Subscript>0.5</Subscript>(Se<Subscript>2</Subscript>)<Subscript>0.1</Subscript>][BF<Subscript>4</Subscript>]

A new Co(III) dioxime complex with selenocarbamide was obtained by the reaction of Co(BF₄)₂ ? 6H₂O, DmgH₂, and Seu (DmgH2 = dimethylglyoxime, Seu = selenocarbamide). According to X-ray diffraction (CIF file CCDC no. 1485732), the product was an ionic coordination compound with unusual composition, [Co(DmgH)₂(Seu)_1.4(Se-Seu)_0.5(Se₂)_0.1][BF₄] (I). Apart from two monodeprotonated DmgH￣ molecules, the central atom coordinates neutral Seu, Se-Seu, and Se₂ molecules. Thus, the crystal contains the complex cations [Co(DmgH)₂(Seu)₂]⁺, [Co(DmgH)₂(Seu)(Se-Seu)]⁺, and [Co(DmgH)₂(Seu)(Se₂)]⁺. Each [BF₄]￣ anion is linked to the cations not only by electrostatic forces but also by intermolecular N–H···F hydrogen bonds (H-bonds). The complex cations are combined by intermolecular N–H···O H-bonds. The new coordination compound was found to possess biological activity. Treatment of the garlic (Allium sativum L.) foliage with an aqueous solution of I optimizes the content of selenium in the leaves and cloves and enhances the growth and plant productivity. The organs of treated plants are characterized by enhanced antioxidant protection owing to increasing activity of antioxidant enzymes and contents of proline and assimilation pigments, and decreasing lipid peroxidation.     

Gas phase structure of micro-hydrated [Mn(ClO<Subscript>4</Subscript>)]<Superscript>+</Superscript> and [Mn<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>3</Subscript>]<Superscript>+</Superscript> ions probed by infrared spectroscopy

Gas-phase infrared photodissociation spectroscopy is reported for the microsolvated [Mn(ClO₄)(H₂O) _n ]⁺ and [Mn₂(ClO₄)₃(H₂O) _n ]⁺ complexes from n = 2 to 5. Electrosprayed ions are isolated in an ion-trap where they are photodissociated. The 2600–3800 cm⁻¹ spectral region associated with the OH stretching mode is scanned with a relatively low-power infrared table-top laser, which is used in combination with a CO₂ laser to enhance the photofragmentation yield of these strongly bound ions. Hydrogen bonding is evidenced by a relatively broad band red-shifted from the free OH region. Band assignment based on quantum chemical calculations suggest that there is formation of water—perchlorate hydrogen bond within the first coordination shell of high-spin Mn(II). Although the observed spectral features are also compatible with the formation of structures with double-acceptor water in the second shell, these structures are found relatively high in energy compared with structures with all water directly bound to manganese. Using the highly intense IR beam of the free electron laser CLIO in the 800–1700 cm⁻¹, we were also able to characterize the coordination mode (η²) of perchlorate for two clusters. The comparison of experimental and calculated spectra suggests that the perchlorate Cl—O stretches are unexpectedly underestimated at the B3LYP level, while they are correctly described at the MP2 level allowing for spectral assignment.     

Pivalates with the M<Superscript>II</Superscript><Subscript>4</Subscript>O<Subscript>4</Subscript> cubane core (M = Co,Ni): synthesis,structure, magnetic properties,and solid-state thermolysis

Methods were developed for the controlled thermal synthesis of high-spin cubane-like pivalates {M^II ₄(μ₃−OR)₄} (M = Co or Ni; R = H or Me) starting from mono-and polynuclear complexes. The solid-state thermal decomposition of the known pivalate clusters [M^II ₄(μ₃−OMe)₄−(μ₂−OOCBu^t)₂(η²−OOCBu^t)₂(MeOH)₄] and the new clusters [M₄^II(μ₃)−OH₄(η¹−OOCBu^t)₃−(μ−(NH₂)₂C₆H₂Me₂)₃(η¹−(NH₂)₂C₆H₂Me₂)₃]⁺(OOCBu^t)− (M = Co or Ni) was studied by differential scanning calorimetry and thermogravimetry. The thermolysis of cubane-like CoII and NiII pivalates is a destructive process. The phase composition of the decomposition products is determined by the nature of coordinated ligands and the structural features of the metal core.     

Synthesis and crystal structures of terephthalato-bridged macrocyclic nickel(II) complexes with <Emphasis Type="Italic">cis</Emphasis> configurations

Three dinuclear terephthalato-bridged nickel(II) complexes [Ni(rac-L)]₂(μ-TPA)(ClO₄)₂ (1), [Ni(RR-L)]₂(μ-TPA)(ClO₄)₂ (2), and [Ni(SS-L)]₂(μ-TPA)(ClO₄)₂ (3) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, TPA = terephthalic acid) have been synthesized and characterized. Single-crystal X-ray diffraction analyses revealed that the Ni(II) atoms have six-coordinated distorted octahedral environments, and the terephthalato ligand bridges two Ni(II) centres in a bis bidentate fashion to form dimers in all three complexes. The monomers of {[Ni(RR-L)]₂(μ-TPA)}²⁺ and {[Ni(SS-L)]₂(μ-TPA)}²⁺ are connected through intermolecular hydrogen bonds to generate 1D right-handed and left-handed helical chains, respectively. The racemic character of 1 and the homochiral natures of 2 and 3 are confirmed by the results of CD spectroscopy.     

Steric distortion of planar NiP<Subscript>2</Subscript>N<Subscript>2</Subscript> chromophores: a spectral,cyclic voltammetric and single crystal X-ray structural study

The complexes trans-[Ni(4-MP)₂(NCS)₂]·MeCN (1) and trans-[Ni(3-MP)₂(NCS)₂] (2) (4-MP = tri(4-methylphenyl)phosphine, 3-MP = tri(3-methylphenyl)phosphine) were prepared and characterized by IR, UV–visible, NMR spectra, CV, TGA and single crystal X-ray crystallography. Both the complexes have planar geometry and are diamagnetic. The Ni–P distances in both complexes are relatively short as a result of strong back donation from nickel to phosphorus. The phenyl rings in the 3-MP analogue (2) show increased pitching with reference to the plane formed by the ipso carbons due to increased steric effects. For complex (2), the N–Ni–N and P–Ni–P angles are significantly lower than the almost linear N–Ni–N and N–Ni–P angles observed for both complex (1) and trans-[Ni(PPh₃)₂(NCS)₂]. This observation indicates that the 3-methylphosphine ligand forces complex (2) to distort towards a tetrahedral geometry. IR spectra of both complexes show strong bands around 2,090 cm⁻¹ due to N-coordinated thiocyanate, while the electronic spectra contain d–d transitions around 452 nm. Cyclic voltammograms show that the irreversible one-electron reduction potentials increase in the following order: trans- [Ni(PPh₃)₂(NCS)₂] < trans- [Ni(3-MP)₂(NCS)₂] < trans-[Ni(4-MP)₂(NCS)₂], revealing the electron releasing effect of the methyl groups. The planar complexes exhibit interallogony in coordinating solvents.