Tricarbonyl Derivatives of Manganese(I) with Diphosphinite Chelating Ligands

Reaction of [MnBr(CO)₃L] [L = Ph₂POCH₂CH₂OPPh₂, L¹ , {(CH₃)₂CH}₂POCH₂CH₂OP{CH(CH₃)₂}₂, L² ] with AgO₃SCF₃ and AgO₂CCF₃ in dichloromethane afforded the new complexes [Mn(O₃SCF₃)(CO)₃L] and [Mn(O₂CCF₃)(CO)₃L], respectively. Substitution of O₃SCF₃ resulted in the new species [Mn(SCN)(CO)₃L], [Mn(NCCH₃)(CO)₃L](O₃SCF₃) and, in the case of L² , [Mn(CN)(CO)₃L²]. By contrast, any attempt to displace the O₂CCF₃ ligand in the same way was unsuccessful. After maintaining for some days the complex [Mn(CH₃CN)(CO)₃L¹](O₃SCF₃) in dichloromethane at room temperature, the new complex [MnCl(CO)₃L¹] was formed. All the new complexes were characterized by elemental analysis, mass spectrometry and IR and NMR spectroscopies. In the case of [Mn(O₃SCF₃)(CO)₃L¹], [Mn(O₂CCF₃) (CO)₃L¹], [MnCl(CO)₃L¹], [Mn(CH₃CN) (CO)₃L²] (O₃SCF₃), [Mn(CN)(CO)₃L²] and [Mn(O₂CCF₃)(CO)₃L²], together with the previously synthesized complex [MnBr(CO)₃L²], suitable crystals for X‐ray structural analysis were isolated. In all of them the Mn atom adopts six‐coordination by bonding to the three CO ligands, the two P atoms of L and either one C atom (CN), one oxygen atom (O₂CCF₃, O₃SCF₃), one N atom (CH₃CN, SCN) or the halogen atom (Cl, Br).     

Synthesis and structural characterization of silver(I) complexes with moon-shaped benzo[1,2-b;4,3-b′]dithiophene phosphine derivative ligands

New silver complexes of general formula [Ag(O₃SCF₃)(PPh₂{bzt})_n] (n = 1–3, bzt = benzo[1,2-b;4,3-b′]dithiophene) have been synthesized and characterized. Spectroscopic studies shown neutral ligand fluxionallity, typical of silver(I) complexes. The solid state structure of the complexes was determined by X-ray crystallographic studies, showing a decrease in structure complexity with increasing number of neutral ligands in silver coordination sphere: [Ag(O₃SCF₃)(PPh₂{bzt})] is a dimer with two bridging triflate anions, further linked into polymeric bidimensional chains along bc plane, through Ag?Ph close contacts; Ag(O₃SCF₃)(PPh₂{bzt})₂] is also a dimmer with two bridging triflate anions, displaying an interesting packing feature, with zig-zag alignment of bzt groups along direction b; [Ag(O₃SCF₃)(PPh₂{bzt})₃] is a monomer.     

New tripodal N-heterocyclic carbene chelators for small molecule activation

In an effort to develop new tripodal N-heterocyclic carbene (NHC) ligands for small molecule activation, two new classes of tripodal NHC ligands TIME^R and TIMEN^R have been synthesized. The carbon-anchored tris(carbene) ligand system TIME^R (R = Me, t-Bu) forms bi- or polynuclear metal complexes. While the methyl derivative exclusively forms trinuclear 3:2 complexes [(TIME^Me)₂M₃]³⁺ with group 11 metal ions, the tert-butyl derivative yields a dinuclear 2:2 complex [(TIME^t-Bu)₂Cu₂]²⁺ with copper(I). The latter complex shows both “normal” and “abnormal” carbene binding modes and accordingly, is best formulated as a bis(carbene)alkenyl complex. The nitrogen-anchored tris(carbene) ligands TIMEN^R (R = alkyl, aryl) bind to a variety of first-row transition metal ions in 1:1 stoichiometry, affording monomeric complexes with a protected reactivity cavity at the coordinated metal center. Complexes of TIMEN^R with Cu(I)/(II), Ni(0)/(I), and Co(I)/(II)/(III) have been synthesized. The cobalt(I) complexes with the aryl-substituted TIMEN^R (R = mesityl, xylyl) ligands show great potential for small molecule activation. These complexes activate for instance dioxygen to form cobalt(III) peroxo complexes that, upon reaction with electrophilic organic substrates, transfer an oxygen atom. The cobalt(I) complexes are also precursors for terminal cobalt(III) imido complexes. These imido complexes were found to undergo unprecedented intra-molecular imido insertion reactions to form cobalt(II) imine species. The molecular and electronic structures of some representative metal NHC complexes as well as the nature of the metal–carbene bond of these metal NHC complexes was elucidated by X-ray and DFT computational methods and are discussed briefly. In contrast to the common assumption that NHCs are pure σ-donors, our studies revealed non-negligible and even significant π-backbonding in electron-rich metal NHC complexes.     

Synthesis and structure of new compounds with Pt-Ga bonds: Insertion of the bulky gallium (I) bisimidinate Ga(DDP) into Pt-Cl bond

Reactions of the sterically bulky mono-valent group 13 bisimidinate gallium(I), Ga(DDP) (1) (DDP = 2-{(2, 6-diisopropylphenyl)amino}-4-{(2, 6-diisopropylphenyl)imino}-2-pentene, HC(CMeNC₆H₃-2,6-ⁱPr₂)₂) with olefin supported group 10 complexes, [(diene)PtCl₂] [diene = 1,5-cyclooctadiene (COD), endo-dicyclopentadiene (dcy)] and [(COD)Pd(Me)(OTf)] (OTf = O₃SCF₃) are reported. These reactions afforded [(COD)Pt(Cl){ClGa(DDP)}] (2), [(dcy)Pt(Cl){ClGa(DDP)}] (3) and [(DDP)Ga(Me)(OTf)] (4) in moderate yields. Compounds 2-4 were characterized by elemental analysis, NMR (¹H, ¹³C) spectroscopy and also by single crystal X-ray structural analysis. The solid state structures of complexes 2 and 3 reveal the oxidative insertion of Ga(DDP) into the Pt-Cl bond without altering the π-coordinated double bonds in the olefin.     

Schwefeldioxid als Ligand und Synthon. XIII. Reaktionen von Isocyanid-tris(triphenylphosphan)nickel(0)-Komplexen mit Schwefeldioxid und N-p-Tolylsulfinylamin

Sulfur Dioxide as Ligand and Synthon. XIII. Reactions of Isocyanide-tris(triphenylphosphane)nickel(0) Complexes with Sulfur Dioxide and N-p-tolylsulfinylamine Reactions of the isocyanide-tris(triphenylphosphane)-nickel(0) complexes [(RNC)Ni(PPh₃)₃] (R = ^tBu, Cy, PhCH₂, p-TosCH₂) with SO₂ and p-TolNSO are described. The sulfur dioxide and N-p-tolylsulfinylamine complexes obtained by PPh₃ ligand substitution have been characterized by means of i.r. and ³¹P n.m.r. spectra. The X-ray crystal structure of [(Ph₃P)₂(CyNC)Ni(SO₂)] · 0.5 PhMe and (Ph₃P)(^tBuNC)Ni(η²-p-TolNSO) have been determined.     

Energy decomposition analysis of the metal-oxime bond in [M{RC(NOH)C(NO)R}2] (M = Ni(II), Pd(II), Pt(II), R = CH3, H, F, Cl, Br, Ph, CF3)

Quantum chemical calculations using gradient-corrected DFT at the BP86/TZ2P+ level were carried out for the metal-dioxime complexes [M{RC(NOH)C(NO)R}₂]with M = Ni, Pd, Pt, R = CH₃, H, F, Cl, Br, Ph, CF₃. The nature of the metal-ligand bond was investigated with an energy decomposition analysis (EDA). The complexes with electron donating substituents R = H, CH₃ have the strongest metal-ligand interaction energies ΔE_int, as well as the largest bond dissociation energies. The analysis of the bonding situation revealed that the metal ← ligand σ donation is much stronger than the metal → ligand π backdonation. The breakdown of the orbital interactions into the contributions of orbitals with different symmetry indicates that the donation from the in-plane lone-pair donor-orbitals of nitrogen into the d_xy AO of the metal provides about one half of the stabilization which comes from ΔE_orb. Inspection of the EDA data indicates that the electrostatic term ΔE_elstat is more important for the trend of the metal-oxime interactions in [M{RC(NOH)C(NO)R}₂] than the orbital term ΔE_orb.     

On the Stability of a POCsp3OP‐Type Pincer Ligand in Nickel(II) Complexes

We describe the results of a study on the stabilities of pincer‐type nickel complexes relevant to catalytic hydroalkoxylation and hydroamination of olefins, C? C and C? X couplings, and fluorination of alkyl halides. Complexes [(POC_sp3OP)NiX] are stable for X=OSiMe₃, OMes (Mes=1,3,5‐Me₃C₆H₂), NPh₂, and CC? H, whereas the O(tBu) and N(SiMe₃)₂ derivatives decompose readily. The phenylacetylide derivative transforms gradually into the zero‐valent species cis‐[{κ^P,κ^C,κ^C′‐(iPr₂POCH₂CHCH₂)}Ni{η²,κ^C,κ^C′‐(iPr₂P(O)CCPh)}]. Likewise, attempts to prepare [(POC_sp3OP)NiF] gave instead the zwitterionic trinuclear species [{(η³‐allyl)Ni}₂‐{μ,κ^P,κ^O‐(iPr₂PO)₄Ni}]. Characterization of these two complexes provides concrete examples of decomposition processes that can dismantle POC_sp3OP‐type pincer ligands by facile C? O bond rupture. These results serve as a cautionary tale for the inherent structural fragility of pincer systems bearing phosphinite donor moieties, and provide guidelines on how to design more robust analogues.     

Triphenylphosphan-Nickel(0)-Komplexe mit Isocyanid-Liganden — [(RNC)nNi(PPh3)4–n] (n = 1–3)

Triphenylphosphane Nickel(0) Complexes with Isocyanide Ligands — [(RNC)_nNi(PPh₃)_4–n] (n = 1–3) Synthesis and properties of the isocyanide triphenylphosphane nickel(0) complexes [(RNC)Ni(PPh₃)₃], [(RNC)₂Ni(PPh₃)₂] and [(RNC)₃Ni(PPh₃)] (R = ^tBu, Cy, PhCH₂, p-TosCH₂) are described. I.r. and ³¹P n.m.r. spectra were recorded and the X-ray crystal structure of [(PhCH₂NC)₂Ni(PPh₃)₂] was determined.     

Syntheses,characterisation and solid state thermal studies of 1-(2-aminoethyl)piperidine (L), 1-(2-aminoethyl)pyrrolidine (L′) and 4-(2-aminoethyl)morpholine (L″) complexes of nickel(II): X-ray single crystal structure analyses of trans-[NiL2(CH3CN)2](ClO4)2, trans-[NiL2(NCS)2] and trans-[NiL″2(NCS)2]

Reactions of nickel(II) salts with substituted ethane-1,2-diamine where one of the amine nitrogens is a part of a flexible cyclic ring, e.g. 1-(2-aminoethyl)piperidine (L), 1-(2-aminoethyl)pyrrolidine (L′) and 4-(2-aminoethyl)morpholine (L″) produce a number of complexes of the type: (i) Ni(AA)₂X₂ (where X=CF₃CO₂ ⁻, SCN⁻ and NO₂ ⁻; AA represents L/L′/L″); (ii) Ni(AA)₂(CH₃CN)₂X₂ (X=ClO₄ ⁻ and NO₃ ⁻); (iii) Ni(AA)₂(H₂O)₂X₂ (X=CF₃SO₃ ⁻, Cl⁻, Br⁻ and I⁻); and (iv) Ni(AA)₂(H₂O)₄X₂ (X=0.5SO₄ ²⁻, 0.5SeO₄ ²⁻ and CF₃SO₃ ⁻). The complexes possess octahedral geometry. The major complexes upon desolvation retain trans-geometry, some of which are cis with respect to the counter-anion and a few of them are square planar. X-ray single crystal structure analyses of trans-[NiL₂(CH₃CN)₂](ClO₄)₂, trans-[NiL₂(NCS)₂] (violet) and trans-[NiL″₂(NCS)₂] (sky-blue) have been done. The violet and sky-blue thiocyanato species have blue and green coloured isomers, respectively, and these pairs of isomers are proposed to be conformational isomers. Solid state thermal investigation of the complexes has been carried out. The complexes show thermochromism due to deaquation–anation/deaquation reaction/change of conformation. Only [NiL₂](ClO₄)₂, [NiL′₂(CF₃CO₂)₂] and [NiL″₂(NO₂)₂] undergo thermally induced phase transition. The effect of flexible ring size on diamine has been discussed.     

Synthesis of PCP‐Supported Nickel Complexes and their Reactivity with Carbon Dioxide

The Ni amide and hydroxide complexes [(PCP)Ni(NH₂)] ( 2 ; PCP=bis‐2,6‐di‐tert‐butylphosphinomethylbenzene) and [(PCP)Ni(OH)] ( 3 ) were prepared by treatment of [(PCP)NiCl] ( 1 ) with NaNH₂ or NaOH, respectively. The conditions for the formation of 3 from 1 and NaOH were harsh (2 weeks in THF at reflux) and a more facile synthetic route involved protonation of 2 with H₂O, to generate 3 and ammonia. Similarly the basic amide in 2 was protonated with a variety of other weak acids to form the complexes [(PCP)Ni(2‐Me‐imidazole)] ( 4 ), [(PCP)Ni(dimethylmalonate)] ( 5 ), [(PCP)Ni(oxazole)] ( 6 ), and [(PCP)Ni(CCPh)] ( 7 ), respectively. The hydroxide compound 3 , could also be used as a Ni precursor and treatment of 3 with TMSCN (TMS=trimethylsilyl) or TMSN₃ generated [(PCP)Ni(CN)] ( 8 ) or [(PCP)Ni(N₃)] ( 9 ), respectively. Compounds 3–7 , and 9 were characterized by X‐ray crystallography. Although 3 , 4 , 6 , 7 , and 9 are all four‐coordinate complexes with a square‐planar geometry around Ni, 5 is a pseudo‐five‐coordinate complex, with the dimethylmalonate ligand coordinated in an X‐type fashion through one oxygen atom, and weakly as an L‐type ligand through another oxygen atom. Complexes 2–9 were all reacted with carbon dioxide. Compounds 2 – 4 underwent facile reaction at low temperature to form the κ¹‐O carboxylate products [(PCP)Ni{OC(O)NH₂}] ( 10 ), [(PCP)Ni{OC(O)OH}] ( 11 ), and [(PCP)Ni{OC(O)‐2‐Me‐imidazole}] ( 12 ), respectively. Compounds 10 and 11 were characterized by X‐ray crystallography. No reaction was observed between 5 – 9 and carbon dioxide, even at elevated temperatures. DFT calculations were performed to model the thermodynamics for the insertion of carbon dioxide into 2 – 9 to form a κ¹‐O carboxylate product and understand the pathways for carbon dioxide insertion into 2 , 3 , 6 , and 7 . The computed free energies indicate that carbon dioxide insertion into 2 and 3 is thermodynamically favorable, insertion into 8 and 9 is significantly uphill, insertion into 5 and 7 is slightly uphill, and insertion into 4 and 6 is close to thermoneutral. The pathway for insertion into 2 and 3 has a low barrier and involves nucleophilic attack of the nitrogen or oxygen lone pair on electrophilic carbon dioxide. A related stepwise pathway is calculated for 7 , but in this case the carbon of the alkyne is significantly less nucleophilic and as a result, the barrier for carbon dioxide insertion is high. In contrast, carbon dioxide insertion into 6 involves a single concerted step that has a high barrier.     

First structurally characterized triazinyl palladium complexes via oxidative addition of cyanuric chloride derivatives

The reaction of cyanuric chloride and two disubstituted derivatives with [Pd(PPh₃)₄] is described, leading to the trans-triazinyl complexes [(PPh₃)₂Pd(C₃N₃R₂)Cl] 2a-c (R = Ph (a), t-Bu (b), Cl (c)) in good to excellent yield via oxidative addition. The complexes were fully characterized including X-ray structure determination.     

Ni(II) and Cu(II) complexes of new unsymmetrical N2O2 Schiff bases derived from 3-(2-aminobenzylimino)-1-phenylbutan-1-ol: synthesis,structure, antibacterial properties,and electrochemistry

Two new N₂O₂ unsymmetrical Schiff bases, H₂L¹ = 3-[({o-[(E)-(o-hydroxyphenyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol and H₂L² = 3-[({o-[(E)-(2-hydroxy-1-naphthyl)methylideneamino]phenyl}methyl)imino]-1-phenyl-1-buten-1-ol, and their copper(II) and nickel(II) complexes, [CuL¹] (1), [CuL²] (2), [NiL¹] (3), and [NiL²] (4), have been synthesized and characterized by elemental analyses and spectroscopic methods. The crystal structures of these complexes have been determined by X-ray diffraction. The coordination geometry around Cu(II) and Ni(II) centers is described as distorted square planar in all complexes with the CuN₂O₂ coordination more distorted than the Ni ones. The electrochemical studies of these complexes indicate a good correlation between the structural distortion and the redox potentials of the metal centers. The ligand and metal complexes were also screened for their in vitro antibacterial activity.     

Charge Effects in PCP Pincer Complexes of NiII bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis

This contribution reports on a new family of Ni^II pincer complexes featuring phosphinite and functional imidazolyl arms. The proligands ^RPIMC^HOP^R′ react at room temperature with Ni^II precursors to give the corresponding complexes [(^RPIMCOP^R′)NiBr], where ^RPIMCOP^R=κ^P,κ^C,κ^P‐{2‐(R′₂PO),6‐(R₂PC₃H₂N₂)C₆H₃}, R=iPr, R′=iPr ( 3 b , 84 %) or Ph ( 3 c , 45 %). Selective N‐methylation of the imidazole imine moiety in 3 b by MeOTf (OTf=OSO₂CF₃) gave the corresponding imidazoliophosphine [(^iPrPIMIOCOP^iPr)NiBr][OTf], 4 b , in 89 % yield (^iPrPIMIOCOP^iPr=κ^P,κ^C,κ^P‐{2‐(iPr₂PO),6‐(iPr₂PC₄H₅N₂)C₆H₃}). Treating 4 b with NaOEt led to the NHC derivative [(NHCCOP^iPr)NiBr], 5 b , in 47 % yield (NHCCOP^iPr=κ^P,κ^C,κ^C‐{2‐(iPr₂PO),6‐(C₄H₅N₂)C₆H₃)}). The bromo derivatives 3–5 were then treated with AgOTf in acetonitrile to give the corresponding cationic species [(^RPIMCOP^R)Ni(MeCN)][OTf] [R=Ph, 6 a (89 %) or iPr, 6 b (90 %)], [(^RPIMIOCOP^R)Ni(MeCN)][OTf]₂ [R=Ph, 7 a (79 %) or iPr, 7 b (88 %)], and [(NHCCOP^R)Ni(MeCN)][OTf] [R=Ph, 8 a (85 %) or iPr, 8 b (84 %)]. All new complexes have been characterized by NMR and IR spectroscopy, whereas 3 b , 3 c , 5 b , 6 b , and 8 a were also subjected to X‐ray diffraction studies. The acetonitrile adducts 6 – 8 were further studied by using various theoretical analysis tools. In the presence of excess nitrile and amine, the cationic acetonitrile adducts 6 – 8 catalyze hydroamination of nitriles to give unsymmetrical amidines with catalytic turnover numbers of up to 95.     

Dimeric scandium(III) and monomeric lanthanide(III) complexes with perfluoropropane-1,3-disulfonates as counter anions for Lewis acid catalysis

A novel scandium(III) complex with disulfonates as counter anions, [Sc(μ-OH)(H₂O)₅]₂[O₃S(CF₂)₃SO₃]₂ (5), was prepared from scandium oxides (Sc₂O₃) and perfluoropropane-1,3-disulfonic acid (1, HO₃SCF₂CF₂CF₂SO₃H). By X-ray analysis, 5 was found to be a μ-OH-bridged dimeric structure bearing two perfluoropropane-1,3-disulfonates without bonding to scandium(III) centers. A series of lanthanide(III) complexes were also prepared from 1 and lanthanide oxides (Ln₂O₃; Ln = La, Nd, Sm, and Gd). In sharp contrast to the dimeric scandium(III) complex, the corresponding lanthanide(III) complexes had monomeric structures. Interestingly, the dimeric scandium(III) complex, but not the monomeric lanthanide complexes, with perfluoropropane-1,3-disulfonates served as an efficient Lewis acid catalyst for the hydrolysis of esters.     

Syntheses, spectral and thermal analyses of heteronuclear aqua(2-methylpyrazine)metal(II) complexes with tetracyanonickelate ion and crystal structure of supramolecular [Cd(H2O)(2mpz)Ni(μ-CN)4]n complex

Polymeric tetracyanonickelate complexes of the type [M(H₂O)(2mpz)Ni(μ-CN)₄] _n (2mpz = 2-methylpyrazine, M = Mn(II) (1) or Cd(II) (2)) have been prepared and characterized by FT-IR, Raman spectroscopy, thermal, and elemental analyses. The crystal structure of supramolecular [Cd(H₂O)(2mpz)Ni(CN)₄] _n complex has been determined by X-ray single crystal diffraction. It crystallizes in the orthorhombic system, space group Pnma. The structure consists of corrugated and cyanide-bridged polymeric two-dimensional networks. In the Hofmann-type complexes, the coordination environment of the M(II) ions can be described as distorted octahedral geometry, whereas around the Ni(II) center has square planar geometry. The spectral features suggest that the 2mpz is coordinated to metal ions of the adjacent layers of [M-Ni(CN)₄] _n as monodentate ligand. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) decomposition of the 2-methylpyrazine ligands, and (iii) release of the CN groups and burning of organic residue.     

Quantum chemical study of the bond orders in the ruthenium,diruthenium and dirhodium nitrosyl complexes

Density functional calculations with the B3LYP functional were carried out for the [Ru(NO)Cl₅]²⁻, [Ru(NO)(NH₃)₅]³⁺, [Ru(NO)(CN)₅]²⁻, [Ru(NO)(CN)₅]³⁻, [Ru(NO)(hedta)]^q (hedta = N-(hydroxyethyl)ethylenediaminetriacetate triple-charged anion; q = 0, −1, −2), Rh₂(O₂CR)₄, Rh₂(O₂CR)₄(NO)₂, Ru₂(O₂CR)₄, Ru₂(O₂CR)₄(NO)₂, Ru₂(dpf)₄, and Ru₂(dpf)₄(NO)₂ (dpf = N,N′-diphenylformamidinate ion; R = H, CH₃, CF₃) complexes. The electronic structure was analyzed in terms of Mayer and Wiberg bond order indices. The technique of bond order indices decomposition into σ-, π-, and δ-contributions was proposed.     

Polymer complexes. LXXI. Spectroscopic studies,thermal properties,DNA binding and antimicrobial activity of polymer complexes

Polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) were prepared by the reaction of 3‐allyl‐5‐[(4‐nitrophenylazo)]‐2‐thioxothiazolidine‐4‐one (HL) with metal ions. The structure of polymer complexes was characterized by elemental analysis, IR, UV–Vis spectra, X‐ray diffraction analysis, magnetic susceptibility, conductivity measurements and thermal analysis. Reaction of HL with Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) ions (acetate or chloride) give polymer complexes ( 1–5 ) with general stoichiometric [M(L)(O₂CCH₃)(H₂O)₂]_n (where L = anionic of HL and M = Co(II) (1) or Ni(II) (2) ), [Mn(HL)₂(OCOCH₃)₂]_n (3) , [Cr(L)₂(Cl)(H₂O)]_n (4) and [Cd(HL)(O₂CCH₃)₂]_n (5) . The value of HOMO–LUMO energy gap (ΔE) for forms (A‐C) of monomer (HL) is 2.529, 2.296 and 2.235 eV, respectively. According to ΔE value, compound has minimum ΔE is the more stable, so keto hydrazone form (C) is more stable than the other forms (azo keto form (A), azo enol form (B)). The interaction between HL, polymer complexes of Co(II), Ni(II), Mn(II), Cr(III) and Cd(II) with Calf thymus DNA showed hypochromism effect. The HL and its polymer complexes were tested against some bacterial and fungal species. The results showed that the Cr(III) polymer complex (4) has more antibacterial activity than HL and polymer complexes (1–3 and 5) against Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium.     

A comparative study of the packing of two polymorphs of the nickel(II) pincer complex [2,6‐bis(di‐tert‐butylphosphinoyl)‐4‐(3,5‐dinitrobenzoyloxy)phenyl‐κ3P,C1,P′]chloridonickel(II)

Pincer complexes can act as catalysts in organic transformations and have potential applications in materials, medicine and biology. They exhibit robust structures and high thermal stability attributed to the tridentate coordination of the pincer ligands and the strong σ metal–carbon bond. Nickel derivatives of these ligands have shown high catalytic activities in cross‐coupling reactions and other industrially relevant transformations. This work reports the crystal structures of two polymorphs of the title Ni^II POCOP pincer complex, [Ni(C₂₉H₄₁N₂O₈P₂)Cl] or [NiCl{C₆H₂‐4‐[OCOC₆H₄‐3,5‐(NO₂)₂]‐2,6‐(OP^tBu₂)₂}]. Both pincer structures exhibit the Ni^II atom in a distorted square‐planar coordination geometry with the POCOP pincer ligand coordinated in a typical tridentate manner via the two P atoms and one arene C atom via a C—Ni σ bond, giving rise to two five‐membered chelate rings. The coordination sphere of the Ni^II centre is completed by a chloride ligand. The asymmetric units of both polymorphs consist of one molecule of the pincer complex. In the first polymorph, the arene rings are nearly coplanar, with a dihedral angle between the mean planes of 27.9 (1)°, while in the second polymorph, this angle is 82.64 (1)°, which shows that the arene rings are almost perpendicular to one another. The supramolecular structure is directed by the presence of weak C—H…O=X (X = C or N) interactions, forming two‐ and three‐dimensional chain arrangements.     

C−H Bond Trifluoromethylation of Arenes Enabled by a Robust,High‐Valent Nickel(IV) Complex

The robust, high‐valent Ni^IV complex [(Py)₂Ni^IVF₂(CF₃)₂] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X‐ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 °C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric Ni^IIICF₃ complexes 2 ⋅Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X‐ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C−H bond‐breaking/C−CF₃ bond‐forming sequence can occur both at Ni^IVCF₃ and Ni^IIICF₃ centers.     

Synthesis,crystal structures and magnetic properties of a series of new cyano-bridged complexes derived from templates [Ni(CN)4]2− and [Co(III)(CN)6]3−

Three new cyano-bridged complexes 1 [Ni(tn)₂Ni(CN)₄] (tn?=?1,3-diaminopropane), 2 [Cu^II(dipn)Ni^II(CN)₄], and 3 [Cu(dipn)]₆[Co(CN)₆]₄?·?4H₂O (dipn?=?dipropylenetriamine) have been assembled by the templates [Ni(CN)₄]^2? and [Co(CN)₆]^3?. 1 consists of a one-dimensional linear chain–Ni(tn)₂–NC–Ni(CN)₂–CN–Ni(tn)_2? in which the Ni(II) centers are linked by two CN groups. One 1-D zigzag chain of 2 is formed with–Ni(2)–C–N–Cu(1)–N–C–linkages. A 2D structure of 3 is formed by an alternate array of [Co(CN)₆]^3? and [Co][Cu₆] units. For 1, there is an overall weak antiferromagnetic interaction between Ni(II) ions through the–NC–Ni–CN–bridges of the diamagnetic [Ni(CN)₄]^2? anions. 2 exhibits a weak antiferromagnetic exchange interaction between copper(II) ions mediated by [Ni(CN)₄]^2? diamagnetic bridges. Complex 3 exhibits a weak ferromagnetic interaction between nearest Cu^II and Cu^II atoms through–NC–Co–CN–bridges.