1,3‐Butadienyl Dianions as Non‐Innocent Ligands: Synthesis and Characterization of Aromatic Dilithio Rhodacycles

Herein we report that 1,4‐dilithio‐1,3‐butadienes, a type of 1,3‐butadienyl dianion, can act as non‐innocent ligands, taking electrons from low‐valent transition metals. Dilithio reagents reacted with [{RhCl(cod)}₂] to give dilithio rhodacycle 3 a . Single‐crystal X‐ray structural analysis revealed the structure of 3 a with averaged bond lengths. XPS data suggested that the oxidation state of Rh in 3 a was more likely to be Rh³⁺. CDA/ECDA confirmed the electron‐transfer process. ⁷Li NMR spectra of 3 a and theoretical calculations revealed a considerable aromatic character. In this process, the dilithio compounds behaved as non‐innocent ligands and formal oxidants. These results demonstrated that organolithium compounds with suitable π‐conjugation could be used as electron acceptor.     

An Abnormal 3.7 Volt O3‐Type Sodium‐Ion Battery Cathode

Layered O3‐type sodium oxides (NaMO₂, M=transition metal) commonly exhibit an O3–P3 phase transition, which occurs at a low redox voltage of about 3 V (vs. Na⁺/Na) during sodium extraction and insertion, with the result that almost 50 % of their total capacity lies at this low voltage region, and they possess insufficient energy density as cathode materials for sodium‐ion batteries (NIBs). Therefore, development of high‐voltage O3‐type cathodes remains challenging because it is difficult to raise the phase‐transition voltage by reasonable structure modulation. A new example of O3‐type sodium insertion materials is presented for use in NIBs. The designed O3‐type Na_0.7Ni_0.35Sn_0.65O₂ material displays a highest redox potential of 3.7 V (vs. Na⁺/Na) among the reported O3‐type materials based on the Ni²⁺/Ni³⁺ couple, by virtue of its increased Ni?O bond ionicity through reduced orbital overlap between transition metals and oxygen within the MO₂ slabs. This study provides an orbital‐level understanding of the operating potentials of the nominal redox couples for O3‐NaMO₂ cathodes. The strategy described could be used to tailor electrodes for improved performance.     

Nano‐sized metal complexes of azo L‐histidine: Synthesis,characterization and their application for catalytic oxidation of 2‐amino phenol

A novel azo dye ligand formed by the coupling of L‐histidine with 2‐hydroxy‐1‐naphthaldyhide(H₂L) and its Ru³⁺, Pd²⁺ and Ni²⁺ nano‐sized complexes were obtained and described by elemental analysis, TGA, magnetic moment measurements, molar conductance, UV‐Vis, ESR, X‐ray powder diffraction, IR, SEM, TEM, ¹H‐nmr, ¹³C‐nmr, and EI‐mass spectral studies. The analytical results and spectral studies detected that the H₂L ligand acts as dibasic tetradentate via aldehyde oxygen, azo nitrogen and deprotonated OH and COOH groups. The data showed the paramagnetic Ru³⁺ complex has octahedral geometry while Pd²⁺ and Ni²⁺ have square planar structures. The molar conductance measurements display all complexes are nonelectrolyte. The crystallinity, morphology and average particle size data revealed the prepared complexes were formed in the Nano scale. The average particle size as calculated from TEM images are found to be 13.72, 64.52 and 115.00 nm for Ru³⁺, Pd²⁺ and Ni²⁺ chelates, respectively. The catalytic activities of these compounds were checked for oxidation of 2‐amino phenol to 2‐amino‐3H phenoxazine‐3‐one as heterogeneous catalysts. A 96, 31 and 21% catalytic conversion are found when using Ru(III), Pd(II) and Ni(II) complexes respectively.     

Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand

Flexible, chelating bis(NHC) ligand 2 , able to accommodate both cis‐ and trans‐coordination modes, was used to synthesize ( 2 )Ni(η²‐cod), 3 . In reaction with GeCl₂, it produced ( 2 )NiGeCl₂, 4 , featuring a T‐shaped Ni⁰ and a pyramidal Ge center. Complex 4 could also be prepared from [( 2 )GeCl]Cl, 5 , and Ni(cod)₂, in a reaction that formally involved Ni–Ge transmetalation, followed by coordination of the extruded GeCl₂ moiety to Ni. A computational analysis showed that 4 possesses considerable multiconfigurational character and the Ni→Ge bond is formed through σ‐donation from the Ni 4s, 4p, and 3d orbitals to Ge. (NHC)₂Ni(cod) complexes 9 and 10 , as well as (NHC)₂GeCl₂ derivative 11 , incorporating ligands that cannot accommodate a wide bite angle, failed to produce isolable Ni–Ge complexes. The isolation of ( 2 )Ni(η²‐Py), 12 , provides further evidence for the reluctance of the ( 2 )Ni⁰ fragment to act as a σ‐Lewis acid.     

Quercetin 2,4‐Dioxygenase Activates Dioxygen in a Side‐On O2–Ni Complex

Quercetin 2,4‐dioxygenase (quercetinase) from Streptomyces uses nickel as the active‐site cofactor to catalyze oxidative cleavage of the flavonol quercetin. How this unusual active‐site metal supports catalysis and O₂ activation is under debate. We present crystal structures of Ni‐quercetinase in three different states, thus providing direct insight into how quercetin and O₂ are activated at the Ni²⁺ ion. The Ni²⁺ ion is coordinated by three histidine residues and a glutamate residue (E⁷⁶) in all three states. Upon binding, quercetin replaces one water ligand at Ni and is stabilized by a short hydrogen bond through E⁷⁶, the carboxylate group of which rotates by 90°. This conformational change weakens the interaction between Ni and the remaining water ligand, thereby preparing a coordination site at Ni to bind O₂. O₂ binds side‐on to the Ni²⁺ ion and is perpendicular to the C2?C3 and C3?C4 bonds of quercetin, which are cleaved in the following reaction steps.     

Enhanced Pseudocapacitance in Multicomponent Transition‐Metal Oxides by Local Distortion of Oxygen Octahedra

Anomalously high pseudocapacitance of a metal oxide was observed when Ni, Co, and Mn were mixed in a solid solution. Analysis by X‐ray absorption near‐edge spectroscopy (XANES) identified a wider redox swing of Ni as the origin of the enlarged pseudocapacitance. Ab initio DFT calculations revealed that aliovalent species resulting from the copresence of multiple transition metals can generate permanent local distortions of [NiO₆] octahedra. As this type of distortion breaks the degenerate e_g level of Ni²⁺, the Jahn–Teller lattice instability necessary for the Ni^2+/3+ redox flip can be effectively diminished during charge–discharge, thus resulting in the significantly increased capacitance. Our findings highlight the importance of understanding structure–property correlation related to local structural distortions in improving the performance of pseudocapacitors.     

Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Homo‐ and Heteronuclear meso,meso‐(E)‐Ethene‐1,2‐diyl‐Linked Diporphyrins: Preparation,X‐ray Crystal Structure,Electronic Absorption and Emission Spectra and Density Functional Theory Calculations

Homo‐ and heteronuclear meso,meso‐(E)‐ethene‐1,2‐diyl‐linked diporphyrins have been prepared by the Suzuki coupling of porphyrinylboronates and iodovinylporphyrins. Combinations comprising 5,10,15‐triphenylporphyrin (TriPP) on both ends of the ethene‐1,2‐diyl bridge M₂10 (M₂=H₂/Ni, Ni₂, Ni/Zn, H₄, H₂Zn, Zn₂) and 5,15‐bis(3,5‐di‐tert‐butylphenyl)porphyrinato‐nickel(II) on one end and H₂, Ni, and ZnTriPP on the other ( M₂11 ), enable the first studies of this class of compounds possessing intrinsic polarity. The compounds were characterized by electronic absorption and steady state emission spectra, ¹H NMR spectra, and for the Ni₂ bis(TriPP) complex Ni₂10 , single crystal X‐ray structure determination. The crystal structure shows ruffled distortions of the porphyrin rings, typical of Ni^II porphyrins, and the (E)‐C₂H₂ bridge makes a dihedral angle of 50° with the mean planes of the macrocycles. The result is a stepped parallel arrangement of the porphyrin rings. The dihedral angles in the solid state reflect the interplay of steric and electronic effects of the bridge on interporphyrin communication. The emission spectra in particular, suggest energy transfer across the bridge is fast in conformations in which the bridge is nearly coplanar with the rings. Comparisons of the fluorescence behaviour of H₄10 and H₂Ni10 show strong quenching of the free base fluorescence when the complex is excited at the lower energy component of the Soret band, a feature associated in the literature with more planar conformations. TDDFT calculations on the gas‐phase optimized geometry of Ni₂10 reproduce the features of the experimental electronic absorption spectrum within 0.1 eV.     

Hydride Reactivity of NiII?X?NiII Entities: Mixed‐Valent Hydrido Complexes and Reversible Metal Reduction

After the lithiation of PYR‐H₂ (PYR^2?=[{NC(Me)C(H)C(Me)NC₆H₃(iPr)₂}₂(C₅H₃N)]^2?), which is the precursor of an expanded β‐diketiminato ligand system with two binding pockets, its reaction with [NiBr₂(dme)] led to a dinuclear nickel(II)–bromide complex, [(PYR)Ni(μ‐Br)NiBr] ( 1 ). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(μ‐SEt)NiBr] ( 3 ). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt₃. This treatment afforded [(PYR)Ni(μ‐H)Ni] ( 2 ), which is a mixed valent Ni^I? μ‐H? Ni^II complex, and [(PYR‐H)Ni(μ‐SEt)Ni] ( 4 ), in which two tricoordinated Ni^I moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the Ni^I centres. The addition of a mild acid to complex 4 leads to the elimination of H₂ and the formation of a Ni^IINi^II compound, [(PYR)Ni(μ‐SEt)NiOTf] ( 5 ), so that the original Ni^II(μ‐SEt)Ni^IIX core of compound 3 is restored. All of these compounds were fully characterized, including by X‐ray diffraction, and their molecular structures, as well as their formation processes, are discussed.     

Synthesis and Reactivity of Six‐Membered Oxa‐Nickelacycles: A Ring‐Opening Reaction of Cyclopropyl Ketones

Cyclopropanecarboxaldehyde ( 1 a ), cyclopropyl methyl ketone ( 1 b ), and cyclopropyl phenyl ketone ( 1 c ) were reacted with [Ni(cod)₂] (cod=1,5‐cyclooctadiene) and PBu₃ at 100 °C to give η²‐enonenickel complexes ( 2 a – c ). In the presence of PCy₃ (Cy=cyclohexyl), 1 a and 1 b reacted with [Ni(cod)₂] to give the corresponding μ‐η²:η¹‐enonenickel complexes ( 3 a , 3 b ). However, the reaction of 1 c under the same reaction conditions gave a mixture of 3 c and cyclopentane derivatives ( 4 c , 4 c′ ), that is, a [3+2] cycloaddition product of 1 c with (E)‐1‐phenylbut‐2‐en‐1‐one, an isomer of 1 c . In the presence of a catalytic amount of [Ni(cod)₂] and PCy₃, [3+2] homo‐cycloaddition proceeded to give a mixture of 4 c (76 %) and 4 c′ (17 %). At room temperature, a possible intermediate, 6 c , was observed and isolated by reprecipitation at ?20 °C. In the presence of 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr), both 1 a and 1 c rapidly underwent oxidative addition to nickel(0) to give the corresponding six‐membered oxa‐nickelacycles ( 6 ai , 6 ci ). On the other hand, 1 b reacted with nickel(0) to give the corresponding μ‐η²:η¹‐enonenickel complex ( 3 bi ). The molecular structures of 6 ai and 6 ci were confirmed by X‐ray crystallography. The molecular structure of 6 ai shows a dimeric η¹‐nickelenolate structure. However, the molecular structure of 6 ci shows a monomeric η¹‐nickelenolate structure, and the nickel(II) 14‐electron center is regarded as having “an unusual T‐shaped planar” coordination geometry. The insertion of enones into monomeric η¹‐nickelenolate complexes 6 c and 6 ci occurred at room temperature to generate η³‐oxa‐allylnickel complexes ( 8 , 9 ), whereas insertion into dimeric η¹‐nickelenolate complex 6 ai did not take place. The diastereoselectivity of the insertion of an enone into 6 c having PCy₃ as a ligand differs from that into 6 ci having IPr as a ligand. In addition, the stereochemistry of η³‐oxa‐allylnickel complexes having IPr as a ligand is retained during reductive elimination to yield the corresponding [3+2] cycloaddition product, which is consistent with the diastereoselectivity observed in Ni⁰/IPr‐catalyzed [3+2] cycloaddition reactions of cyclopropyl ketones with enones. In contrast, reductive elimination from the η³‐oxa‐allylnickel having PCy₃ as a ligand proceeds with inversion of stereochemistry. This is probably due to rapid isomerization between syn and anti isomers prior to reductive elimination.     

trans‐Di­aqua­tetrakis(3,5‐di­methyl­pyrazole‐N2)­nickel(II) dichloride

The X‐ray structure analysis of [Ni(C₅H₈N₂)₄(H₂O)₂]Cl₂ was undertaken to elucidate the geometry around the Ni²⁺ ion. The molecule lies on a twofold axis which runs through the O—Ni—O atoms. The geometry around the Ni²⁺ ion is best described as slightly distorted tetragonal bipyramidal.     

齐聚噻吩衍生物电致变色性质

合成了四种齐聚噻吩衍生物：5,5"-二氰基-2,2’:5’,2"-三噻吩 (DCN3T), 5,5"’-二氰基-2,2’:5’,2":5",2"’-四噻吩 (DCN4T), 5,5"’-甲氧基-2,2’:5’,2":5",2"’-四噻吩(DMO4T) 和 4,4"-二羧基-5,5"-二丙基-2,2’:5’,2"-三噻吩 (BP3T-DCOOH),研究了它们的电致变色性质,研究结果发现,这四种齐聚噻吩衍生物膜在电场作用下,可以发生可逆的颜色变化。     

[Bis(3,5‐dimethylpyrazol‐1‐yl‐κN2)hydro(pyrazol‐1‐yl‐κN2)borato][(3,5‐dimethylpyrazol‐1‐yl‐κN2)dihydro(pyrazol‐1‐yl‐κN2)borato]nickel(II)

The title compound, [Ni(C₈H₁₂BN₄)(C₁₃H₁₈BN₆)] or Bp′Tp′Ni^II, where Bp′ is (3,5‐dimethylpyrazol‐1‐yl)dihydro(pyrazol‐1‐yl)borate and Tp′ is bis(3,5‐dimethylpyrazol‐1‐yl)hydro(pyrazol‐1‐yl)borate, contains a divalent Ni^II centre bound by the chelating N atoms of the polysubstituted pyrazolylborate ligands. It is shown to lack a strong agostic B—H...Ni interaction, implying that the sixth coordination site is unoccupied in the solid state. This square‐pyramidal complex is the only known crystal structure where the Ni^II centre is pentacoordinated while bonded exclusively to pyrazolyl units. This is of interest with respect to electrochemical and catalytic properties.     

Synthese,Strukturen, EPR‐ und ENDOR‐spektroskopische Untersuchungen an Übergangsmetallkomplexen von N,N‐Diisobutyl‐N′‐(2, 6‐difluor)benzoylselenoharnstoff

Synthesis, Structures, EPR and ENDOR Investigations on Transition Metal Complexes of N, N‐diisobutyl‐N′‐(2, 6‐difluoro)benzoyl selenourea The synthesis and the structures of the Ni^II and Pd^II complexes of the ligand N, N‐diisobutyl‐N′‐(2, 6‐difluoro)benzoylselenourea HBuⁱ₂dfbsu are reported. The ligands coordinate bidentately forming bis‐chelates. The structure of the ligand could not be obtained, however, the structure of its O‐ethyl ester will be reported. Attempts to prepare the Cu^II complex result only in the formation of oily products. However, the Cu^II complex could be incorporated into the corresponding Ni^II and Pd^II compounds. From this diamagnetically diluted powder and single‐crystal samples were obtained being suitable for EPR‐ENDOR measurements. We report X‐ and Q‐band EPR investigations on the systems [Cu/Ni(Buⁱ₂dfbsu)₂] and [Cu/Pd(Buⁱ₂dfbsu)₂] as well as a single‐crystal X‐band EPR study for [Cu/Ni(Buⁱ₂dfbsu)₂]. The obtained ^{63, 65}Cu and ⁷⁷Se hyperfine structure tensors allow a determination of the spin‐density distribution within the first coordination sphere. In addition, orientation selective ¹⁹F Q‐band pulse ENDOR investigations on powder‐samples of [Cu/Ni(Buⁱ₂dfbsu)₂] have been performed. The hyperfine structure tensors of two intramolecular ¹⁹F atoms could be determined. According to the small ¹⁹F couplings only a vanishingly small spin‐density of < 1 % was obtained for these ¹⁹F atoms.     

Nickel(II)‐Mediated Reversible Thiolate/Disulfide Conversion as a Mimic for a Key Step of the Catalytic Cycle of Methyl‐Coenzyme M Reductase

According to the well‐accepted mechanism, methyl‐coenzyme M reductase (MCR) involves Ni‐mediated thiolate‐to‐disulfide conversion that sustains its catalytic cycle of methane formation in the energy saving pathways of methanotrophic microbes. Model complexes that illustrate Ni‐ion mediated reversible thiolate/disulfide transformation are unknown. In this paper we report the synthesis, crystal structure, spectroscopic properties and redox interconversions of a set of Ni^II complexes comprising a tridentate N₂S donor thiol and its analogous N₄S₂ donor disulfide ligands. These complexes demonstrate reversible Ni^II‐thiolate/Ni^II‐disulfide (both bound and unbound disulfide‐S to Ni^II) transformations via thiyl and disulfide monoradical anions that resemble a primary step of MCR's catalytic cycle.     

Ionic Ferrocenyl Coordination Compounds Derived from Imidazole and 1,2,4‐Triazole Ligands and Their Catalytic Effects During Combustion

Alkylferrocene‐based burning‐rate catalysts (BRCs) show conspicuous migration tendency and volatility during prolonged storage and fabrication process of a composite solid propellant. To enhance anti‐migration ability of the BRCs, forty novel ionic coordination compounds, [M(L)₄(H₂O)₂]_mX_n (M = Mn²⁺, Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Fe²⁺, Pb²⁺, Cr³⁺, Bi³⁺, or Cd²⁺; L = ferrocenylmethyl imidazole or ferrocenylmethyl‐1,2,4‐triazole; X = picrate or trinitroresorcinolate), were synthesized and characterized by FT‐IR, UV/Vis, and elementary analysis. Additionally, the crystal structures of six compounds were confirmed by single‐crystal X‐ray diffraction. The TG analyses revealed that the new compounds show high thermal stability. Cyclic voltammetry studies suggested that theyare irreversible redox systems. Their catalytic activities in the thermal degradation of ammonium perchlorate (AP), 1,3,5‐trinitro‐1,3,5‐triazacyclo‐hexane (RDX) and 1,2,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) were examined by DSC technique. The results indicated that all the new compounds exert great effects on the thermal decomposition of AP and RDX, among them some compounds are more active than catocene. Compound 26 has good catalytic ability in the thermal decomposition of HMX, representing a rare example of the reported ferrocene‐based BRCs which show catalytic activity during combustion of HMX.     

An unusual partial occupancy of labile chloride and aqua ligands in cocrystallized isomers of a nickel(II) complex bearing a tripodal N4‐donor ligand

A novel Ni²⁺ complex with the N₄‐donor tripodal ligand bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl][2‐(pyridin‐2‐yl)ethyl]amine (L), namely, aqua{bis[(1‐methyl‐1H‐imidazol‐2‐yl‐κN³)methyl][2‐(pyridin‐2‐yl‐κN)ethyl]amine‐κN}chloridonickel(II) perchlorate, [NiCl(C₁₇H₂₂N₆)(H₂O)]ClO₄ or [NiCl(H₂O)(L)Cl]ClO₄ ( 1 ), was synthesized and characterized by spectroscopic and spectrometric methods. The crystal structure of 1 reveals an interesting and unusual cocrystallization of isomeric complexes, which are crystallographically disordered with partial occupancy of the labile cis aqua and chloride ligands. The Ni²⁺ centre exhibits a distorted octahedral environment, with similar bond lengths for the two Ni—N(imidazole) bonds. The bond length increases for Ni—N(pyridine) and Ni—N(amine), which is in agreement with literature examples. The bond lengths of the disordered labile sites are also in the expected range and the Ni—Cl and Ni—O bond lengths are comparable with similar compounds. The electronic, redox and solution stability behaviour of 1 were also evaluated, and the data obtained suggest the maintenance of structural integrity, with no sign of demetalation or decomposition under the studied conditions.     

Coordination Centres of Purine Nucleotides: Adenosine‐5′‐diphosphate and Adenosine‐5′‐triphosphate in their Reactions with Nickel(II), Cobalt(II) and Tetramines

Interactions between the nucleotides: adenosine‐5′‐diphosphate (ADP) and adenosine‐5′‐triphosphate (ATP) with Ni^II and Co^II ions, as well as with spermine (Spm) and 1,11‐diamine‐4,8‐diazaundecane (3,3,3‐tet) are the subject of this study. Composition and stability constants of mixed complexes thus formed have been determined on the basis of the potentiometric measurements, whereas interaction centres in ligands have been identified by VIS and NMR spectral parameter analysis. Mixed tetraprotonated complexes with Ni^II, i.e. Ni(ADP)H₄(Spm), Ni(ATP)H₄(Spm), Ni(ADP)H₄(3,3,3‐tet) and Ni(ATP)H₄(333‐tet), are identified as ML·······L′ type adducts, in which the main coordination centre is the nucleotide nitrogen N(1) or N(7) donor atom, and the fully protonated polyamine is engaged in noncovalent interactions with nucleotide phosphate group oxygen atoms. Ni(ADP)H₂(Spm), Ni(ATP)H₂(Spm), Ni(ADP)H₂(3,3,3‐tet) and Ni(ATP)H₂(3,3,3‐tet) complexes represent the {N3} coordination type In diprotonated mixed complexes of Ni^II with spermine are weak noncovalent interligand interactions, providing an additional stabilising effect. Formation of ML·······L′ type molecular complexes has been observed in systems with Co^II: Co(ADP)H₄(Spm), Co(ATP)H₄(Spm), Co(ADP)H₄(3,3,3‐tet) and Co(ATP)H₄(3,3,3‐tet), in which the N(7) atom and oxygen atoms of the phosphate group are involved in coordination and the fully protonated polyamine is engaged in noncovalent interactions with the nucleotide N(1).     

Bis(1,5‐di­aza­cyclo­octane‐N,N′)nickel(II) dibromide

The crystal structure of the title complex, [Ni(C₆H₁₄N₂)₂]Br₂, consists of discrete [Ni(C₆H₁₄N₂)₂]²⁺ cations and bromide counter‐anions. The Ni^II ion is at the center of symmetry and is four‐coordinated by four nitro­gen donors of the mesocyclic ligand 1,5‐di­aza­cyclo­octane (DACO) [Ni—N 1.935 (2)–1.937 (2) Å]. The coordination geometry of Ni^II can be considered as square planar and both DACO ligands take the boat–chair conformation. The bromide anions are hydrogen bonded with the nitro­gen donors of the ligands to form a macrocycle‐like ring system.     

Aquachlorobis[4,4,5,5‐tetramethyl‐2‐(2‐pyridyl)‐4,5‐dihydro‐1H‐imidazol‐1‐oxyl 3‐oxide‐κ2O1,N2]nickel(II) nitrate methanol disolvate monohydrate

The title complex, [NiCl(C₁₂H₁₆N₃O₂)₂(H₂O)]NO₃·2CH₄O·H₂O, was obtained from a methano­lic solution of Ni(NO₃)₂·6H₂O, 2‐pyridyl nitro­nyl nitro­xide (2‐NITpy) and (NEt₄)₂[CoCl₄]. The equatorial coordination sites of the octahedral Ni^II centre are occupied by two chelating radical ligands, with the axial positions occupied by the Cl^? and water ligands. The H₂O—Ni—Cl axis of the complex lies along a crystallographic twofold axis, so that only half the cation is present in the asymmetric unit. The Ni—Cl bond length [2.3614 (17) Å] is significantly shorter than distances typical of octahedral Ni^II centres [2.441 (5) Å]. However, with only one nitrate anion per formula unit, the oxidation state of the metal must be assigned as Ni^II. The 2‐NITpy ligands bend away from the equatorial plane, forming a hydro­phobic region around the Cl atoms. Conversely, the ligated water mol­ecule forms moderately strong hydrogen bonds with the disordered methanol solvent mol­ecules, which in turn form interactions with the water of crystallization and the disordered nitrate anion. These interactions combine to give hydro­philic regions throughout the crystal structure.