Two precatalysts for application in propargylic CH activation

The complexes {bis[(2‐diphenylphosphanyl)phenyl] ether‐κ²P,P′}(η⁴‐norbornadiene)rhodium(I) tetrafluoridoborate, [Rh(C₇H₈)(C₃₆H₂₈OP₂)]BF₄, and {bis[(2‐diphenylphosphanyl)phenyl] ether‐κ²P,P′}[η⁴‐(Z,Z)‐cycloocta‐1,5‐diene]rhodium(I) tetrafluoridoborate dichloromethane monosolvate, [Rh(C₈H₁₂)(C₃₆H₂₈OP₂)]BF₄·CH₂Cl₂, are applied as precatalysts in redox‐neutral atomic‐economic propargylic CH activation [Lumbroso et al. (2013). Angew. Chem. Int. Ed. 52 , 1890–1932]. In addition, the catalytically inactive pentacoordinated 18‐electron complex {bis[(2‐diphenylphosphanyl)phenyl] ether‐κ²P,P′}chlorido(η⁴‐norbornadiene)rhodium(I), [RhCl(C₇H₈)(C₃₆H₂₈OP₂)], was synthesized, which can form in the presence of chloride in the reaction system.     

Crystal structures and spectroscopic characterization of MBr2(CNXyl)n (M = Fe and Co,n = 4; M = Ni,n = 2; Xyl = 2,6‐dimethylphenyl), and of formally zero‐valent iron as a cocrystal of Fe(CNXyl)5 and Fe2(CNXyl)9

Structures and spectroscopic characterization of the divalent complexes cis‐dibromidotetrakis(2,6‐dimethylphenyl isocyanide)iron(II) dichloromethane 0.771‐solvate, [FeBr₂(C₉H₉N)₄]·0.771CH₂Cl₂ or cis‐FeBr₂(CNXyl)₄·0.771CH₂Cl₂ (Xyl = 2,6‐dimethylphenyl), trans‐dibromidotetrakis(2,6‐dimethylphenyl isocyanide)iron(II), [FeBr₂(C₉H₉N)₄] or trans‐FeBr₂(CNXyl)₄, trans‐dibromidotetrakis(2,6‐dimethylphenyl isocyanide)cobalt(II), [CoBr₂(C₉H₉N)₄] or trans‐CoBr₂(CNXyl)₄, and trans‐dibromidobis(2,6‐dimethylphenyl isocyanide)nickel(II), [NiBr₂(C₉H₉N)₂] or trans‐NiBr₂(CNXyl)₂, are presented. Additionally, crystals grown from a cold diethyl ether solution of zero‐valent Fe(CNXyl)₅ produced a structure containing a cocrystallization of mononuclear Fe(CNXyl)₅ and the previously unknown dinuclear [Fe(CNXyl)₃]₂(μ₂‐CNXyl)₃, namely pentakis(2,6‐dimethylphenyl isocyanide)iron(0) tris(μ₂‐2,6‐dimethylphenyl isocyanide)bis[tris(2,6‐dimethylphenyl isocyanide)iron(0)], [Fe(C₉H₉N)₅][Fe₂(C₉H₉N)₉]. The (M)C—N—C(Xyl) angles of the isocyanide ligand are nearly linear for the metals in the +2 oxidation state, for which the ligands function essentially as pure donors. The νCN stretching frequencies for these divalent metal isocyanides are at or above that of the free ligand. Relative to Fe^II, in the structure containing iron in the formally zero‐valent oxidation state, the Fe—C bond lengths have shortened, the C[triple‐bond]N bond lengths have elongated, the (M)C—N—C(Xyl) angles of the terminal CNXyl ligands are more bent, and the νCN stretching frequencies have shifted to lower energies, all indicative of substantial M(dπ)→π* backbonding.     

Niobium isocyanide complexes,Nb(CNAr)6, with Ar = 2,6‐dimethylphenyl (Xyl), a diamagnetic dimer containing four reductively coupled isocyanides,and Ar = 2,6‐diisopropylphenyl (Dipp), a paramagnetic monomer analogous to the highly unstable hexacarbonylniobium(0)

Treatment of bis(mesitylene)niobium(0) with 6–7 equivalents of 2,6‐dimethylphenyl isocyanide (CNXyl) affords two products with the empirical formula Nb(CNXyl)_n (n = 7 or 6), which have been shown to be the diamagnetic dimers bis[μ‐N,N′,N′′,N′′′‐tetrakis(2,6‐dimethylphenyl)squaramidinato(2?)]bis[pentakis(2,6‐dimethylphenyl isocyanide)niobium(I)], [Nb₂(C₉H₉N)₁₀(C₃₆H₃₆N₄)] or [Nb(CNXyl)₅]₂[μ‐C₄(NXyl)₄]·xSolvent, 1 , and bis[μ‐N,N′,N′′,N′′′‐tetrakis(2,6‐dimethylphenyl)squaramidinato(2?)]bis[tetrakis(2,6‐dimethylphenyl isocyanide)niobium(I)] tetrahydrofuran trisolvate, [Nb₂(C₉H₉N)₈(C₃₆H₃₆N₄)]·3C₄H₈O or [Nb(CNXyl)₄]₂[μ‐C₄(NXyl)₄]·3THF (THF = tetrahydrofuran), 2 . Each contains Nb^I bound to either five or four terminal isocyanides, respectively, and to an unprecedented bridging tetraarylsquaramidinate(2?) unit, coordinated as a bidentate ligand to each niobium center, symmetrically due to the crystallographic inversion center that coincides with the centroid of the central C₄ unit. Thus, in the presence of CNXyl, the bis(mesitylene)niobium(0) is oxidized to niobium(I), resulting in the facile loss of both mesitylene groups and the reductive coupling of two CNXyl groups per niobium to provide the first examples of tetraarylsquaramidinate(2?) ligands, [cyclo‐C₄N₄Ar₄]^2?, coordinated to metals. In contrast, bis(mesitylene)niobium(0) reacts with the more crowded 2,6‐diisopropylphenyl isocyanide (CNDipp) to afford the paramagnetic monomer hexakis(2,6‐diisopropylphenyl isocyanide)niobium(0), [Nb(C₁₃H₁₇N)₆] or Nb(CNDipp)₆, 3 , the first zero‐valent niobium isocyanide analog of the highly unstable Nb(CO)₆, which is presently only known to exist in an argon matrix at 4.2 K.     

A new heteroleptic cuprous complex with strong yellow photoluminescence

In the title heteroleptic cuprous complex, (acetonitrile‐κN)({2‐[2‐(diphenylphosphanyl)phenoxy]phenyl}diphenylphosphane‐κ²P,P′)[2‐(pyridin‐4‐yl‐κN)‐1,3‐benzoxazole]copper(I) hexafluoridophosphate, [Cu(C₃₆H₂₈OP₂)(CH₃CN)(C₁₂H₈N₂O)]PF₆, conventionally abbreviated [Cu(POP)(CH₃CN)(4‐PBO)]PF₆, where POP is the diphosphane ligand {2‐[2‐(diphenylphosphanyl)phenoxy]phenyl}diphenylphosphane and 4‐PBO is the N‐containing ligand 2‐(pyridin‐4‐yl)‐1,3‐benzoxazole, the asymmetric unit consists of a hexafluoridophosphate anion and a whole mononuclear cation, where the Cu^I centre is coordinated by two P atoms from the POP ligand, by one N atom from the 4‐PBO ligand and by the N atom of the coordinated acetonitrile molecule, giving rise to a CuP₂N₂ distorted tetrahedral coordination geometry. The electronic absorption, photoluminescence and thermal stability properties of this complex have been studied on as‐synthesized samples, which had previously been examined by powder X‐ray diffraction. A yellow emission signal is attributed to an excited state arising from metal‐to‐ligand charge transfer (MLCT).     

Acetate and acetamide complexes of [Ni(Me4[12]aneN4)]PF6: a tale of two ligands

Although there are many examples of acetate complexes, acetamide complexes are virtually unknown. A side‐by‐side comparison in (acetato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₃O₂)(C₁₂H₂₈N₄)]PF₆, (1), and (acetamidato‐κ²O,O′)(1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane‐κ⁴N)nickel(II) hexafluoridophosphate, [Ni(C₂H₄NO)(C₁₂H₂₈N₄)]PF₆, (2), shows the steric equivalence between these two ligands, suggesting that acetamide could be considered as a viable acetate replacement for electronic tuning.     

Synthesis,characterization, and crystal structures of organonickel(II) complexes coordinated to novel 1‐bromo‐2,6‐bis{[(λ5‐phosphanylidene)imino]methyl}benzene NCN‐pincer ligands

A novel family of four 1‐bromo‐2,6‐bis{[(λ⁵‐phosphanylidene)imino]methyl}benzene ligands has been synthesized and characterized. The phosphiniminomethyl substituents are decorated with either three phenyl groups, two phenyl and one cyclohexyl group, one phenyl and two cyclohexyl groups, or three cyclohexyl groups. Each ligand was metallated using zero‐valent nickel through an oxidative addition to form a family of organonickel(II) complexes, namely (2,6‐bis{[(triphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II) dichloromethane hemisolvate, [NiBr(C₄₄H₃₇N₂P₂)]·0.5CH₂Cl₂, (2,6‐bis{[(cyclohexyldiphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II) diethyl ether hemisolvate, [NiBr(C₄₄H₄₉N₂P₂)]·0.5C₄H₁₀O, (2,6‐bis{[(dicyclohexylphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II), [NiBr(C₄₄H₆₁N₂P₂)], and (2,6‐bis{[(tricyclohexyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II), [NiBr(C₄₄H₇₃N₂P₂)]. This family of complexes represents a useful opportunity to investigate the impact of incrementally changing the steric characteristics of a complex on its structure and reactivity.     

A new heteroleptic phosphorescent cuprous complex supported by a BINAP ligand: synthesis,structure, luminescence properties and theoretical analyses

Luminescent cuprous complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The heteroleptic cuprous complex solvate rac‐(acetonitrile‐κN)(3‐aminopyridine‐κN)[2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl‐κ²P,P′]copper(I) hexafluoridophosphate dichloromethane monosolvate, [Cu(C₅H₆N₂)(C₂H₃N)(C₄₄H₃₂P₂)]PF₆·CH₂Cl₂, conventionally abbreviated as [Cu(3‐PyNH₂)(CH₃CN)(BINAP)]PF₆·CH₂Cl₂, ( I ), where BINAP and 3‐PyNH₂ represent 2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl and 3‐aminopyridine, respectively, is described. In this complex solvate, the asymmetric unit consists of a cocrystallized dichloromethane molecule, a hexafluoridophosphate anion and a complete racemic heteroleptic cuprous complex cation in which the cuprous centre, in a tetrahedral CuP₂N₂ coordination, is coordinated by two P atoms from the BINAP ligand, one N atom from the 3‐PyNH₂ ligand and another N atom from a coordinated acetonitrile molecule. The UV–Vis absorption and photoluminescence properties of this heteroleptic cuprous complex have been studied on polycrystalline powder samples, which had been verified by powder X‐ray diffraction before recording the spectra. Time‐dependent density functional theory (TD‐DFT) calculations and a wavefunction analysis reveal that the orange–yellow phosphorescence emission should originate from intra‐ligand (BINAP) charge transfer mixed with a little of the metal‐to‐ligand charge transfer ³(IL+ML)CT excited state.     

Oxidative degradation of the organometallic iron(II) complex [Fe{bis[3‐(pyridin‐2‐yl)‐1H‐imidazol‐1‐yl]methane}(MeCN)(PMe3)](PF6)2: structure of the ligand decomposition product trapped via coordination to iron(II)

Iron is of interest as a catalyst because of its established use in the Haber–Bosch process and because of its high abundance and low toxicity. Nitrogen‐heterocyclic carbenes (NHC) are important ligands in homogeneous catalysis and iron–NHC complexes have attracted increasing attention in recent years but still face problems in terms of stability under oxidative conditions. The structure of the iron(II) complex [1,1′‐bis(pyridin‐2‐yl)‐2,2‐bi(1H‐imidazole)‐κN³][3,3′‐bis(pyridin‐2‐yl‐κN)‐1,1′‐methanediylbi(1H‐imidazol‐2‐yl‐κC²)](trimethylphosphane‐κP)iron(II) bis(hexafluoridophosphate), [Fe(C₁₇H₁₄N₆)(C₁₆H₁₂N₆)(C₃H₉P)](PF₆)₂, features coordination by an organic decomposition product of a tetradentate NHC ligand in an axial position. The decomposition product, a C—C‐coupled biimidazole, is trapped by coordination to still‐intact iron(II) complexes. Insights into the structural features of the organic decomposition products might help to improve the stability of oxidation catalysts under harsh conditions.     

A new phosphorescent heteroleptic cuprous complex with a neutral 2‐methylquinolin‐8‐ol ligand: synthesis,structure characterization,properties and TD–DFT calculations

Luminescent Cu^I complexes have emerged as promising substitutes for phosphorescent emitters based on Ir, Pt and Os due to their abundance and low cost. The title heteroleptic cuprous complex, [9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)‐9H‐xanthene‐κ²P ,P ](2‐methylquinolin‐8‐ol‐κ²N ,O )copper(I) hexafluorophosphate, [Cu(C₁₀H₉NO)(C₃₉H₃₂OP₂)]PF₆, conventionally abbreviated as [Cu(Xantphos)(8‐HOXQ)]PF₆, where Xantphos is the chelating diphosphine ligand 9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)‐9H‐xanthene and 8‐HOXQ is the N ,O‐chelating ligand 2‐methylquinolin‐8‐ol that remains protonated at the hydroxy O atom, is described. In this complex, the asymmetric unit consists of a hexafluorophosphate anion and a whole mononuclear cation, where the Cu^I atom is coordinated by two P atoms from the Xantphos ligand and by the N and O atoms from the 8‐HOXQ ligand, giving rise to a tetrahedral CuP₂NO coordination geometry. The electronic absorption and photoluminescence properties of this complex have been studied on as‐synthesized samples, whose purity had been determined by powder X‐ray diffraction. In the detailed TD–DFT (time‐dependent density functional theory) studies, the yellow emission appears to be derived from the inter‐ligand charge transfer and metal‐to‐ligand charge transfer (M +L ′)→LCT excited state (LCT is ligand charge transfer).     

Counter‐anion role in the formation of two supramolecular complexes: [Ag2(DPP)2](ClO4)2·CH3CN and [Ag2(DPP)2(NO3)2] {DPP is N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine}

The title compounds, bis{μ‐N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine‐κ²N¹:P}disilver bis(perchlorate) acetonitrile monosolvate, [Ag₂(C₁₈H₁₇N₂P)₂](ClO₄)₂·CH₃CN, (1), and bis{μ‐N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine‐κ²N¹:P}bis[(nitrato‐κ²O,O)silver], [Ag₂(C₁₈H₁₇N₂P)₂(NO₃)₂], (2), each contain disilver macrocyclic [Ag₂(C₁₈H₁₇N₂P)₂]²⁺ cations lying about inversion centres. The cations are constructed by two N‐[(diphenylphosphanyl)methyl]pyridin‐4‐amine (DPP) ligands linking two Ag⁺ cations in a head‐to‐tail fashion. In (1), the unique Ag⁺ cation has a near‐linear coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands. Two ClO₄⁻ anions doubly bridge two metallomacrocycles through Ag...O and N—H...O weak interactions to form a chain extending in the c direction. The half‐occupancy acetonitrile molecule lies with its methyl C atom on a twofold axis and makes a weak N...Ag contact. In (2), there are two independent [Ag(C₁₈H₁₇N₂P)]⁺ cations. The nitrate anions weakly chelate to each Ag⁺ cation, leading to each Ag⁺ cation having a distorted tetrahedral coordination geometry consisting of one pyridine N atom and one P atom from two different DPP ligands, and two chelating nitrate O atoms. Each dinuclear [Ag₂(C₁₈H₁₇N₂P)₂(NO₃)₂] molecule acts as a four‐node to bridge four adjacent equivalent molecules through N—H...O interactions, forming a two‐dimensional sheet parallel to the bc plane. Each sheet contains dinuclear molecules involving just Ag1 or Ag2 and these two types of sheet are stacked in an alternating fashion. The sheets containing Ag1 all lie near x = , , etc, while those containing Ag2 all lie near x = 0, 1, 2 etc. Thus, the two independent sheets are arranged in an alternating sequence at x = 0, , 1, etc. These two different supramolecular structures result from the different geometric conformations of the templating anions which direct the self‐assembly of the cations and anions.     

Two nickel(II) bis[(pyridin‐2‐yl)methyl]amine complexes with homophthalic and benzene‐1,2,4,5‐tetracarboxylic acids

Two new Ni^II complexes involving the ancillary ligand bis[(pyridin‐2‐yl)methyl]amine (bpma) and two different carboxylate ligands, i.e. homophthalate [hph; systematic name: 2‐(2‐carboxylatophenyl)acetate] and benzene‐1,2,4,5‐tetracarboxylate (btc), namely catena‐poly[[aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)]‐μ‐2‐(2‐carboxylatophenyl)aceteto‐κ²O:O′], [Ni(C₉H₆O₄)(C₁₂H₁₃N₃)(H₂O)]_n, and (μ‐benzene‐1,2,4,5‐tetracarboxylato‐κ⁴O¹,O²:O⁴,O⁵)bis(aqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) bis(triaqua{bis[(pyridin‐2‐yl)methyl]amine‐κ³N,N′,N′′}nickel(II)) benzene‐1,2,4,5‐tetracarboxylate hexahydrate, [Ni₂(C₁₀H₂O₈)(C₁₂H₁₃N₃)₂(H₂O)₂]·[Ni(C₁₂H₁₃N₃)(H₂O)₃]₂(C₁₀H₂O₈)·6H₂O, (II), are presented. Compound (I) is a one‐dimensional polymer with hph acting as a bridging ligand and with the chains linked by weak C—H...O interactions. The structure of compound (II) is much more complex, with two independent Ni^II centres having different environments, one of them as part of centrosymmetric [Ni(bpma)(H₂O)]₂(btc) dinuclear complexes and the other in mononuclear [Ni(bpma)(H₂O)₃]²⁺ cations which (in a 2:1 ratio) provide charge balance for btc⁴⁻ anions. A profuse hydrogen‐bonding scheme, where both coordinated and crystal water molecules play a crucial role, provides the supramolecular linkage of the different groups.     

In situ synthesis of mononuclear copper(II) complexes of the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine

Two mononuclear copper complexes, {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}(3,5‐dimethyl‐1H‐pyrazole‐κN²)(perchlorato‐κO)copper(II) perchlorate, [Cu(ClO₄)(C₅H₈N₂)(C₁₂H₁₉N₅)]ClO₄, (I), and {bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐κN²)methyl]amine‐κN}bis(3,5‐dimethyl‐1H‐pyrazole‐κN²)copper(II) bis(hexafluoridophosphate), [Cu(C₅H₈N₂)₂(C₁₂H₁₉N₅)](PF₆)₂, (II), have been synthesized by the reactions of different copper salts with the tripodal ligand tris[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (TDPA) in acetone–water solutions at room temperature. Single‐crystal X‐ray diffraction analysis revealed that they contain the new tridentate ligand bis[(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methyl]amine (BDPA), which cannot be obtained by normal organic reactions and has thus been captured in the solid state by in situ synthesis. The coordination of the Cu^II ion is distorted square pyramidal in (I) and distorted trigonal bipyramidal in (II). The new in situ generated tridentate BDPA ligand can act as a meridional or facial ligand during the process of coordination. The crystal structures of these two compounds are stabilized by classical hydrogen bonding as well as intricate nonclassical hydrogen‐bond interactions.     

A twofold interpenetrating two‐dimensional zinc(II) coordination polymer: synthesis,crystal structure and physical properties

A novel twofold interpenetrating two‐dimensional (2D) Zn^II coordination framework, poly[[(μ‐1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene‐κ²N³:N³)(μ‐naphthalene‐2,6‐dicarboxylato‐κ²O²:O⁶)zinc(II)] dimethylformamide monosolvate], {[Zn(C₁₂H₆O₄)(C₁₄H₁₄N₄)]·C₃H₇NO}_n or {[Zn(1,3‐BMIB)(NDC)]·DMF}_n (I), where H₂NDC is naphthalene‐2,6‐dicarboxylic acid, 1,3‐BMIB is 1,3‐bis(2‐methyl‐1H‐imidazol‐1‐yl)benzene and DMF is dimethylformamide, was prepared and characterized through IR spectroscopy, elemental analysis, thermal analysis and single‐crystal X‐ray diffraction. Single‐crystal X‐ray diffraction analysis revealed that (I) exhibits an unusual twofold interpenetrating 2D network. In addition, it displays strong fluorescence emissions and a high photocatalytic activity for the degradation of Rhodamine B (RhB) under UV‐light irradiation.     

Two ZnII mononuclear coordination compounds with pyridinedicarboxylate and auxiliary N‐(pyridin‐4‐ylmethylidene)hydroxylamine ligands

Two new mononuclear coordination compounds, bis{4‐[(hydroxyimino)methyl]pyridinium} diaquabis(pyridine‐2,5‐dicarboxylato‐κ²N,O²)zincate(II), (C₆H₇N₂O)₂[Zn(C₇H₃NO₄)₂(H₂O)₂], (1), and (pyridine‐2,6‐dicarboxylato‐κ³O²,N,O⁶)bis[N‐(pyridin‐4‐ylmethylidene‐κN)hydroxylamine]zinc(II), [Zn(C₇H₃NO₄)(C₆H₆N₂O)₂], (2), have been synthesized and characterized by single‐crystal X‐ray diffractometry. The centrosymmetric Zn^II cation in (1) is octahedrally coordinated by two chelating pyridine‐2,5‐dicarboxylate ligands and by two water molecules in a distorted octahedral geometry. In (2), the Zn^II cation is coordinated by a tridentate pyridine‐2,6‐dicarboxylate dianion and by two N‐(pyridin‐4‐ylmethylidene)hydroxylamine molecules in a distorted C₂‐symmetric trigonal bipyramidal coordination geometry.     

Platinum complexes of oxopurines: cis‐bis(theophyllinato‐N7)bis(triphenylphosphine)platinum(II) and cis‐chloro(theobrominato‐N1)bis(triphenylphosphine)platinum(II) ethanol hemisolvate

The syntheses and structures of two mixed‐ligand complexes of platinum(II) with deprotonated oxopurine bases and tri­phenyl­phosphine are reported, namely the theophyllinate complex cis‐bis(1,2,3,6‐tetra­hydro‐1,3‐di­methyl­purine‐2,6‐dionato‐κN⁷)­bis(tri­phenyl­phosphine‐κP)­platinum(II), [Pt(C₇H₇N₄O₂)₂(C₁₈H₁₅P)₂], (I), and the theobrominate complex cis‐chloro(1,2,3,6‐tetrahydro‐3,7‐dimethylpurine‐2,6‐dionato‐κN¹)­bis(tri­phenyl­phosphine‐κP)­platinum(II) ethanol hemisolvate, [PtCl(C₇H₇N₄O₂)(C₁₈H₁₅P)₂]·0.5C₂H₅OH, (II). In (I), the coordination geometry of Pt is square planar, formed by the two coordinating N atoms of the theophyl­linate anions in a cis arrangement and two P atoms from the tri­phenyl­phosphine groups. In (II), there are two crystallographically independent mol­ecules. They both exhibit a square‐planar coordination geometry around Pt involving one Cl atom, the coordinating N atom of the theobrominate anion and two P atoms from the tri­phenyl­phosphine groups. The two tri­phenyl­phosphine groups are arranged in a cis configuration in both structures. The heterocyclic rings are rotated with respect to the coordination plane of the metal by 82.99 (8) and 88.09 (8)° in complex (I), and by 85.91 (16) and 88.14 (18)° in complex (II). Both structures are stabilized by intramolecular stacking interactions involving the purine rings and the phenyl rings of adjacent tri­phenyl­phosphine moieties.     

Complexation du 2‐[(5‐méthyl­pyrazolyl)méthyle]benzimidazole par les chlorures de cuivre et de cadmium

The structures of dichloro{2‐[(5‐methyl‐1H‐pyrazol‐3‐yl‐κN²)methyl]‐1H‐1,3‐benzimidazole‐κN³}copper(II), [CuCl₂(C₁₂H₁₂N₄)], and di‐μ‐chloro‐bis(chloro{2‐[(5‐methyl‐1H‐pyrazol‐3‐yl‐κN²)methyl]‐1H‐1,3‐benzimidazole‐κN³}­cadmium(II)), [Cd₂Cl₄(C₁₂H₁₂N₄)₂], show that these compounds have the structural formula [ML(Cl)₂]_n, where L is 2‐[(5‐methylpyra­zolyl)methyl]benzimidazole. When M is copper, the complex is a monomer (n = 1), with a tetrahedral coordination for the Cu atom. When M is cadmium (n = 2), the complex lies about an inversion centre giving rise to a centrosymmetric dimer in which the Cd atoms are bridged by two chloride ions and are pentacoordinated.     

Tantalum isocyanide complexes: TaI(CNDipp)6 (Dipp is 2,6‐diisopropylphenyl) and ionic [Ta(CNDipp)7][Ta(CNDipp)6], a formal disproportionation product of the 17‐electron Ta0 metalloradical Ta(CNDipp)6

Treatment of tetraethylammonium hexacarbonyltantalate, [Et₄N][Ta(CO)₆], with 1.1 equivalents of molecular iodine (I₂) in tetrahydrofuran (THF) at 200 K, followed by the addition of 6.0 equivalents of 2,6‐diisopropylphenyl isocyanide (CNDipp) and slow warming to 293 K over a 24 h period gave the tantalum(I) iodide derivative hexakis(2,6‐diisopropylphenyl isocyanide‐κC)iodidotantalum(I), [TaI(C₁₃H₁₇N)₆] or TaI(CNDipp)₆, 1 . Recrystallization of this substance from pentane provided deep‐red nearly black parallelepipeds of the product, which was characterized by single‐crystal X‐ray diffraction. Addition of 1 in THF at 200 K to a suspension of an excess (5.8 equivalents) of caesium graphite (CsC₈), followed by warming, filtration, and solvent removal, afforded a dark‐green oily solid of unknown composition, from which several red–brown rhombohedral plates of the ditantalum salt heptakis(2,6‐diisopropylphenyl isocyanide‐κC)tantalum hexakis(2,6‐diisopropylphenyl isocyanide‐κC)tantalate, [Ta(C₁₃H₁₇N)₇][Ta(C₁₃H₁₇N)₆] or [Ta(CNDipp)₇][Ta(CNDipp)₆], 2 , were harvested. Salt 2 is a unique substance, as it is the only known example of a salt containing a homoleptic cation, [ML_x]⁺, and a homoleptic anion, [ML_y]^?, with the same transition metal and π‐acceptor ligand L. In solution, 2 undergoes full comproportionation to afford the recently reported 17‐electron paramagnetic zerovalent tantalum complex Ta(CNDipp)₆, the only known isolable TaL₆ complex of Ta⁰.     

Copper(I) and copper(II) complexes of an ethylene cross‐bridged cyclam

The preparation and crystal structures of (4,11‐di­benzyl‐1,4,8,11‐tetra­aza­bi­cyclo­[6.6.2]­hexa­decane‐κ⁴N)copper(I) hexa‐fluorophosphate, [Cu(C₂₆H₃₈N₄)]PF₆, and acetonitrile(4,11‐dibenzyl‐1,4,8,11‐tetraazabicyclo[6.6.2]hexadecane‐κ⁴N)‐copper(II) bis(hexafluorophosphate), [Cu(C₂H₃N)(C₂₆H₃₈‐N₄)](PF₆)₂, are described. The Cu^I ion is tetracoordinated in a very distorted tetrahedron, while the Cu^II analogue is pentacoordinated in a square pyramid.     

The bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ2P,P′]iron(II) tetrabromidoferrate(II) and μ‐oxido‐bis[tribromidoferrate(III)] complex salts

Orange crystals of bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ²P,P′]iron(II) tetrabromidoferrate(II), [Fe(CH₃CN)₂(C₂₆H₂₅NP₂)₂][FeBr₄], (I), and red crystals of bis(acetonitrile‐κN)bis[N,N‐bis(diphenylphosphanyl)ethanamine‐κ²P,P′]iron(II) μ‐oxido‐bis[tribromidoferrate(III)], [Fe(CH₃CN)₂(C₂₆H₂₅NP₂)₂][Fe₂Br₆O], (II), were obtained from the same solution after prolonged exposure to atmospheric oxygen, resulting in partial oxidation of the [FeBr₄]²⁻ anion to the [Br₃FeOFeBr₃]²⁻ anion. The asymmetric unit of (I) consists of three independent cations, one on a general position and two on inversion centres, with two anions, required to balance the charge, located on general positions. The asymmetric unit of (II) consists of two independent cations and two anions, all on special positions. The geometric parameters within the coordination environments of the cations do not differ significantly, with the major differences being in the orientation of the phenyl rings on the bidentate phosphane ligand. The ethyl substituent in the cation of (II) and the Br atoms in the anions of (II) are disordered. The P—Fe—P bite angles represent the smallest angles reported to date for octahedral Fe^II complexes containing bidentate phosphine ligands with MeCN in the axial positions, ranging from 70.82 (3) to 70.98 (4)°. The average Fe—Br bond distances of 2.46 (2) and 2.36 (2) Å in the [FeBr₄]²⁻ and [Br₃FeOFeBr₃]²⁻ anions, respectively, illustrate the differences in the Fe oxidation states.     

Chromium complexes bearing disubstituted organophosphate ligands and their use in ethylene polymerization

The crystal structures of three unusual chromium organophosphate complexes have been determined, namely, bis(μ‐butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO:κO′)di‐μ‐hydroxido‐bis[(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl hydrogen phosphato‐κO)(butyl 2,6‐di‐tert‐butyl‐4‐methylphenyl phosphato‐κO)chromium](Cr—Cr) heptane disolvate or {Cr₂(μ₂‐OH)₂[μ₂‐PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO:κO′]₂[PO₂(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂[HOPO(OBu)(O‐2,6‐^tBu₂‐4‐MeC₆H₂)‐κO]₂}·2C₇H₁₆, [Cr₂(C₁₉H₃₂O₄P)₄(C₁₉H₃₃O₄P)₂(OH)₂]·2C₇H₁₆, denoted ( 1 )·2(heptane), [μ‐bis(2,6‐diisopropylphenyl) phosphato‐1κO:2κO′]bis[bis(2,6‐diisopropylphenyl) phosphato]‐1κO,2κO‐chlorido‐2κCl‐triethanol‐1κ²O,2κO‐di‐μ‐ethanolato‐1κ²O:2κ²O‐dichromium(Cr—Cr) ethanol monosolvate or {Cr₂(μ₂‐OEt)₂[μ₂‐PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO:κO′][PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl(EtOH)₃}·EtOH, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₃Cl(C₂H₆O)₃]·C₂H₆O, denoted ( 2 )·EtOH, and di‐μ‐ethanolato‐1κ²O:2κ²O‐bis{[bis(2,6‐diisopropylphenyl) hydrogen phosphato‐κO][bis(2,6‐diisopropylphenyl) phosphato‐κO]chlorido(ethanol‐κO)chromium}(Cr—Cr) benzene disolvate or {Cr₂(μ₂‐OEt)₂[PO₂(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂[HOPO(O‐2,6‐ⁱPr₂‐C₆H₃)₂‐κO]₂Cl₂(EtOH)₂}·2C₆H₆, [Cr₂(C₂H₅O)₂(C₂₄H₃₄O₄P)₂(C₂₄H₃₅O₄P)₂Cl₂(C₂H₆O)₂]·2C₆H₆, denoted ( 3 )·2C₆H₆. Complexes ( 1 )–( 3 ) have been synthesized by an exchange reaction between the in‐situ‐generated corresponding lithium or potassium disubstituted phosphates with CrCl₃(H₂O)₆ in ethanol. The subsequent crystallization of ( 1 ) from heptane, ( 2 ) from ethanol and ( 3 ) from an ethanol/benzene mixture allowed us to obtain crystals of ( 1 )·2(heptane), ( 2 )·EtOH and ( 3 )·2C₆H₆, whose structures have the monoclinic P2₁, orthorhombic P2₁2₁2₁ and triclinic P space groups, respectively. All three complexes have binuclear cores with a single Cr—Cr bond, i.e. Cr₂O₆P₂ in ( 1 ), Cr₂PO₄ in ( 2 ) and Cr₂O₂ in ( 3 ), where the Cr atoms are in distorted octahedral environments, formally having 16 ē per Cr atom. The complexes have bridging ligands μ₂‐OH in ( 1 ) or μ₂‐OEt in ( 2 ) and ( 3 ). The organophosphate ligands demonstrate terminal κO coordination modes in ( 1 )–( 3 ) and bridging μ₂‐κO:κO′ coordination modes in ( 1 ) and ( 2 ). All the complexes exhibit hydrogen bonding: two intramolecular O_phos…H—O_phos interactions in ( 1 ) and ( 3 ) form two {H[PO₂(OR)₂]₂} associates; two intramolecular Cl…H—O_Et hydrogen bonds additionally stabilize the Cr₂O₂ core in ( 3 ); two intramolecular O_phos…H—O_Et interactions and two O…H—O intermolecular hydrogen bonds with a noncoordinating ethanol molecule are observed in ( 2 )·EtOH. The presence of both basic ligands (OH^? or OEt^?) and acidic [H(phosphate)₂]^? associates at the same metal centres in ( 1 ) and ( 3 ) is rather unusual. Complexes may serve as precatalysts for ethylene polymerization under mild conditions, providing polyethylene with a small amount of short‐chain branching. The formation of a small amount of α‐olefins has been detected in this reaction.