Reversible Coordination of Dioxygen by Tripodal Tetraamine Copper Complexes Incorporated in a Porous Silica Framework

The present study reports the synthesis and rational design of porous structured materials by using a templating method. A tetraethoxysilylated tripodal tetraamine (TREN) was covalently incorporated in a silica framework with a double imprint: A surfactant template and a metal ion imprint. The presence of a cationic surfactant (CTAB) endowed the material with a high porosity, and the tripodal or square‐pyramidal topology of the ligand was preserved thanks to the use of the silylated Cu^II complex. After removal of the surfactant and de‐metalation, the incorporated tetraamine was quantitatively complexed by CuCl₂ and the material has shown after thermal activation that a reversible binding of O₂ on the metal ions occurred. This chemisorption process was monitored by UV/Vis and EPR spectroscopies, and the Cu:O₂ adduct was postulated to be an end‐on μ‐η¹:η¹‐peroxodicopper(II) complex bridged by a chloride ion. The Cu^I‐active species, formed during the activation step, were fully recovered during several O₂ binding cycles. The high reactivity of the copper complexes and the room‐temperature stability of the dioxygen adduct were explained by the fine adaptability of the tripodal ligand to different geometries, the confinement of the active sites in the hybrid silica that protect them from degradation by a control of the metal‐ion microenvironment, as well as the short‐range lamellar order of the copper complexes in the framework.     

Syntheses and Structural Characterization of 1D Chain and 1D Ladder Coordination Polymers Assembled from Exo‐bidentate Imidazolyl Ligands

Five novel coordination polymers, [(Cu(L¹)₂OH) · Cl · 3H₂O] ( 1 ) [L¹ = bis(N‐imidazolyl)methane], [Cd(L¹)₂(NCS)₂] ( 2 ), [Zn(L¹)₂(NCS)₂] ( 3 ), [Cu(L¹)₂(NO₃)₂] ( 4 ), and [Cu(L²)_1.5(NCS)₂] ( 5 ) [L² = 1,4‐bis(N‐imidazolyl)butane] were obtained from self‐assembly of the corresponding metal salts with flexible ligands and their structures were fully characterized by X‐ray diffraction (XRD) analysis, Fourier Transform Infrared (FT‐IR) spectroscopy, elemental analysis and thermogravimetric (TGA) measurements. X‐ray diffraction analyses revealed that complexes 1 , 2 , 3 , and 4 exhibit 1D double‐stranded chain structures, which result from doubly bridged [CuOH], [M(NCS)₂] (M = Cd, Zn), and [Cu(NO₃)₂] units, respectively. The polymeric copper complex 5 displays 1D ladder structure., These complexes, with the exception of complex 1 , are stable up to 300 °C.     

Functionalised Tris(pyrazolyl)methane Ligands and Re(CO)3 Complexes Thereof

The synthesis of new tripodal nitrogen ligands derived from tris(pyrazolyl)methane (Tpm^R, R = H, tBu, Ph in 3‐position) is described. After deprotonation of the parent tris(pyrazolyl)methane Tpm^R, the carbanion reacts readily with ethylene oxide to yield the 3,3,3‐tris(3′‐substituted pyrazolyl)propanol ligands[(3‐Rpz)₃CCH₂CH₂OH, R = H, tBu, Ph, 1a – c ]. These ligands can be easily derivatised at the alcohol function. Microwave‐assisted reactions of these ligands and [Re(CO)₅Br] yields the complex [( 1a )Re(CO)₃]Br ( 4 ) in the case of ligand 1a , whereas in the case of the substituted ligands 1b and 1c degradation was observed. The degradation products are identified as [(Hpz^R)₂Re(CO)₃Br] [R = tBu ( 7b ), Ph ( 7c )]. These complexes were also prepared directly from [Re(CO)₅Br] and the corresponding pyrazoles by microwave‐assisted synthesis. The Re(CO)₃ complexes 4 and [( 1a )Re(CO)₃]OTf ( 5 ) are water‐soluble. The structures of 5· H₂O and [{(pz)₃CCH₂CH₃}Re(CO)₃]OTf · 1.5H₂O · ¹/₂CH₃CN ( 6· 1.5H₂O · ¹/₂CH₃CN) as well as the structure of 7b have been elucidated by X‐ray crystallography.     

P−P Condensation and P−N/P−P Bond Metathesis: Facile Synthesis of Cationic Tri‐ and Tetraphosphanes

[L_C^RP((PhP)₂C₂H₄)][OTf] ( 4 a,b [OTf]) and [L_C^iPrP(PPh₂)₂][OTf] ( 5 b [OTf]) were prepared from the reaction of imidazoliumyl‐substituted dipyrazolylphosphane triflate salts [L_C^RP(pyr)₂][OTf] ( 3 a,b [OTf]; a : R=Me, b =iPr; L_C^R=1,3‐dialkyl‐4,5‐dimethylimidazol‐2‐yl; pyr=3,5‐dimethylpyrazol‐1‐yl) with the secondary phosphanes PhP(H)C₂H₄P(H)Ph) and Ph₂PH. A stepwise double P?N/P?P bond metathesis to catena‐tetraphosphane‐2,3‐diium triflate salt [(Ph₂P)₂(L_C^MeP)₂][OTf]₂ ( 7 a [OTf]₂) is observed when reacting 3 a [OTf] with diphosphane P₂Ph₄. The coordination ability of 5 b [OTf] was probed with selected coinage metal salts [Cu(CH₃CN)₄]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph₂PPL_C^iPr)Au}₄][OTf]₄ ( 9 [OTf]₄) was unexpectedly formed as a result of a chloride‐induced P?P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [( 5 b )M(CH₃CN)₃][OTf]₂ (M=Cu, Ag) ( 10 [OTf]₂, 11 [OTf]₂).     

Synthesis and Characterization of Copper(I) Complexes Containing Tri(2‐Pyridylmethyl)Amine Ligand

Reaction of copper halides CuX (X=Cl, Br, I) with tri(2‐pyridylmethyl)amine) (TPMA) in THF under N₂ affords a series of monomeric copper(I) complexes CuX(TPMA) (X=Cl ( 1 ), Br ( 2 ) and I ( 3 )). Treatment of [CuCl(TPMA)] ( 1 ) with 0.5 equivalent of 1,4‐diisocyanobenzene following by equimolar amount of NaBF₄ affords a novel binuclear complex [(TPMA)Cu(μ‐1,4‐CNC₆H₄NC)Cu(TPMA)](BF₄)₂ ( 4 ). The copper(I) halide TPMA complexes show interesting fluxional behaviors in temperature dependence in the ¹H NMR spectrum that can be explained by the dissociation and reassociation of the pyridyl group and alkylamine nitrogen of TPMA ligand. The crystal structures of 1 , 3 and 4 are determined by an X‐ray diffractometer. Complexes 1 and 3 are distorted tetrahedral coordinates with strong bonding between three pyridyl N atoms and the corresponding halide donor. Crystallographic results of 4 clearly indicates two Cu(I) ions are bridged by 1,4‐diisocyanobenzene, forming a centro‐symmetrical homobinuclear complex with a “dangling” uncoordinated pyridyl group.     

New Functional Cyclic Aminomethylphosphine Ligands for the Construction of Catalysts for Electrochemical Hydrogen Transformations

Eight‐membered cyclic functional bisphosphines, namely 1,5‐di‐aryl‐3,7‐di(2‐pyridyl)‐1,5‐diaza‐3,7‐diphosphacyclooctanes (aryl=2‐pyridyl, m‐tolyl, p‐tolyl, diphenylmethyl, benzyl, (R)‐(+)‐(α‐methyl)benzyl), with 2‐pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2‐pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X‐ray crystallography. The bisphosphines readily form neutral P,P‐chelate complexes [(κ²‐P,P‐L)MCl₂], cationic bis‐P,P‐chelate complexes [(κ²‐P,P‐L)₂M]²⁺, or a five‐coordinate complex [(κ²‐P,P‐L)₂NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel‐cell test, have been studied.     

Facile Carbon–Fluorine Bond Activation and Subsequent Functionalisation of 1,1‐Difluoroethylene and Tetrafluoroethylene Promoted by Adjacent Metal Centres

The bridging fluoroolefin ligands in the complexes [Ir₂(CH₃)(CO)₂(μ‐olefin)(dppm)₂][OTf] (olefin=tetrafluoroethylene, 1,1‐difluoroethylene; dppm=μ‐Ph₂PCH₂PPh₂; OTf^?=CF₃SO₃^?) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me₃SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me₃SiOTf to the tetrafluoroethylene‐bridged species gives the difluorovinylidene‐bridged product [Ir₂(CH₃)(OTf)(CO)₂(μ‐OTf)(μ‐C?CF₂)(dppm)₂][OTf]. The 1,1‐difluoroethylene species is exceedingly reactive, reacting with water to give 2‐fluoropropene and [Ir₂(CO)₂(μ‐OH)(dppm)₂][OTf] and with carbon monoxide to give [Ir₂(CO)₃(μ‐κ¹:η²‐C?CCH₃)(dppm)₂][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir₂(κ¹‐C₂F₃)(OTf)(CO)₂(μ‐H)(μ‐CH₂)(dppm)₂][OTf], obtained through single C? F bond activation of the tetrafluoroethylene‐bridged complex, reacts with H₂ to form trifluoroethylene, allowing the facile replacement of one fluorine in C₂F₄ with hydrogen.     

Dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate and bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ2N,N′)copper(I) tetrafluoroborate

The single‐crystal X‐ray structures of dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate, C₁₄H₁₂N₂O₄, and the copper(I) coordination complex bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ²N,N′)copper(I) tetrafluoroborate, [Cu(C₁₄H₁₂N₂O₄)₂]BF₄, are reported. The uncoordinated ligand crystallizes across an inversion centre and adopts the anticipated anti pyridyl arrangement with coplanar pyridyl rings. In contrast, upon coordination of copper(I), the ligand adopts an arrangement of pyridyl donors facilitating chelating metal coordination and an increased inter‐pyridyl twisting within each ligand. The distortion of each ligand contrasts with comparable copper(I) complexes of unfunctionalized 2,2′‐bipyridine.     

Synthesis,Characterization, and Reactivity of Cationic Gold Diarylallenylidene Complexes

Methoxide abstraction from gold acetylide complexes of the form (L)Au[η¹‐C≡CC(OMe)ArAr′] (L=IPr, P(^tBu)₂(ortho‐biphenyl); Ar/Ar′=C₆H₄X where X=H, Cl, Me, OMe) with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at ?78 °C resulted in the formation of the corresponding cationic gold diarylallenylidene complexes [(L)Au=C=C=CArAr′]⁺ OTf^? in ≥85±5 % yield according to ¹H NMR analysis. ¹³C NMR and IR spectroscopic analysis of these complexes established the arene‐dependent delocalization of positive charge on both the C1 and C3 allenylidene carbon atoms. The diphenylallenylidene complex [(IPr)Au=C=C=CPh₂]⁺ OTf^? reacted with heteroatom nucleophiles at the allenylidene C1 and/or C3 carbon atom.     

Sterically‐Directed Consecutive and Size‐Selective Self‐Assembly of Palladium Diphosphane Complexes with an Ar‐BIAN Ligand: Unexpected Formation of Pentameric and Hexameric Aggregates

The coordination properties of N,N′‐bis[4‐(4‐pyridyl)phenyl]acenaphthenequinonediimine (L¹) and N,N′‐bis[4‐(2‐pyridyl)phenyl]acenaphthenequinonediimine (L²) were investigated in self‐assembly with palladium diphosphane complexes [Pd(P^P)(H₂O)₂](OTf)₂ (OTf=triflate) by using various analytical techniques, including multinuclear (¹H, ¹⁵N, and ³¹P) NMR spectroscopy and mass spectrometry (P^P=dppp, dppf, dppe; dppp=bis(diphenylphosphanyl)propane, dppf= bis(diphenylphosphanyl)ferrocene, and dppe=bis(diphenylphosphanyl)ethane). Beside the expected trimeric and tetrameric species, the interaction of an equimolar mixture of [Pd(dppp)]²⁺ ions and L¹ also generates pentameric aggregates. Due to the E/Z isomerism of L¹, a dimeric product was also observed. In all of these species, which correspond to the general formula [Pd(dppp)L¹]_n(OTf)_2n (n=2–5), the L¹ ligand is coordinated to the Pd center only through the terminal pyridyl groups. Introduction of a second equivalent of the [Pd(dppp)]²⁺ tecton results in coordination to the internal, sterically more encumbered chelating site and induces enhancement of the higher nuclearity components. The presence of higher‐order aggregates (n=5, 6), which were unexpected for the interaction of cis‐protected palladium corners with linear ditopic bridging ligands, has been demonstrated both by mass‐spectrometric and DOSY NMR spectroscopic analysis. The sequential coordination of the [Pd(dppp)]²⁺ ion is attributed to the dissimilar steric properties of the two coordination sites. In the self‐assembled species formed in a 1:1:1 mixture of [Pd(dppp)]²⁺/[Pd(dppe)]²⁺/L¹, the sterically more demanding [Pd(dppp)]²⁺ tectons are attached selectively to the pyridyl groups, whereas the more hindered imino nitrogen atoms coordinate the less bulky dppe complexes, thus resulting in a sterically directed, size‐selective sorting of the metal tectons. The propensity of the new ligands to incorporate hydrogen‐bonded solvent molecules at the chelating site was confirmed by X‐ray diffraction studies.     

Phenol Based‐Ligands with Two Adjacent N,N′,O‐Binding Pockets

The synthesis of three new ligands and their coordination behavior towards zinc ions with strongly coordinating anions and cobalt ions with weakly coordinating anions are reported. The ligands have two adjacent imidazolyl‐pyridinyl and pyrazolyl‐pyridinyl binding pockets, respectively, which are linked by a phenol unit. We also investigated the dynamic behavior of the ligand having the imidazolyl‐pyridiyl sidearm in solution. The reaction of the ligands and ZnCl₂ yielded complexes of the type [ L Zn₂Cl₃]. When we used Co^II salts with weakly coordinating anions, complexes of the general formula [ L ₂Co₂]²⁺ were formed.     

First Dinuclear Copper/Gallium Complexes: Supporting Cu0 and CuI Centres by Low‐Valent Organogallium Ligands

The synthesis and structural characterisation of low‐valent dinuclear copper(I) and copper(0) complexes supported by organogallium ligands has been accomplished for the first time by the reductive coordination reaction of [GaCp*] (Cp*=pentamethylcyclopentadienyl) and [Ga(ddp)] (ddp=HC(CMeNC₆H₃‐2,6‐iPr₂)₂ 2‐diisopropylphenylamino‐4‐diisopropylphenylimino‐2‐pentene) with readily available copper(II) and copper(I) precursors. The treatment of CuBr₂ and Cu(OTf)₂ (OTf=CF₃SO₃) with [Ga(ddp)] under mild conditions resulted in elimination of [Ga(L)₂(ddp)] (L=Br, OTf) and afforded the novel gallium(I)/copper(I) compounds [{(ddp)GaCu(L)}₂] (L=Br ( 1 ), OTf ( 2 )). The single‐crystal X‐ray structure determinations of 1 and 2 reveal that these molecules are composed of {(ddp)GaCu(L)} dimeric units, with planar Cu^I? Ga^I four‐membered rings and short Cu^I???Cu^I distances, with 2 exhibiting the shortest Cu^I???Cu^I contact reported to date of 2.277(3) Å. The all‐gallium coordinated dinuclear [Cu₂(GaCp*)(μ‐GaCp*)₃Ga(OTf)₃] ( 3 ) is formed when Cu(OTf)₂ is combined with [GaCp*] instead of [Ga(ddp)]. Notably, in the course of this redox reaction Lewis acidic Ga(OTf)₃ is formed, which coordinates to one of the electron‐rich copper(0) centres. Compound 3 is suggested as the first case of a structurally characterised complex of copper(0). By changing the copper(II) to a copper(I) source, that is, [Cu(cod)₂][OTf] (cod=1,5‐cyclooctadiene), the salt [Cu₂(GaCp*)₃(μ‐GaCp*)₂][OTf]₂ ( 4 ) is formed, the cationic part of which is related to previously described isoelectronic dinuclear d¹⁰ complexes of the type [M₂(GaCp*)₅] (M=Pd, Pt).     

Synthesis,Characterization, and Reactivity of Cationic Gold Diarylallenylidene Complexes

Methoxide abstraction from gold acetylide complexes of the form (L)Au[η¹‐C≡CC(OMe)ArAr′] (L=IPr, P(^tBu)₂(ortho‐biphenyl); Ar/Ar′=C₆H₄X where X=H, Cl, Me, OMe) with trimethylsilyl trifluoromethanesulfonate (TMSOTf) at −78 °C resulted in the formation of the corresponding cationic gold diarylallenylidene complexes [(L)Au=C=C=CArAr′]⁺ OTf⁻ in ≥85±5 % yield according to ¹H NMR analysis. ¹³C NMR and IR spectroscopic analysis of these complexes established the arene‐dependent delocalization of positive charge on both the C1 and C3 allenylidene carbon atoms. The diphenylallenylidene complex [(IPr)Au=C=C=CPh₂]⁺ OTf⁻ reacted with heteroatom nucleophiles at the allenylidene C1 and/or C3 carbon atom.     

Tracking the dissolution–recrystallization structural transformation (DRST) of copper(II) complexes: a combined crystallographic,mass spectrometric and DFT study

Methanol‐ and temperature‐induced dissolution–recrystallization structural transformation (DRST) was observed among two novel Cu^II complexes. This is first time that the combination of X‐ray crystallography, mass spectrometry and density functional theory (DFT) theoretical calculations has been used to describe the fragmentation and recombination of a mononuclear Cu^II complex at 60 °C in methanol to obtain a binuclear copper(II) complex. Combining time‐dependent high‐resolution electrospray mass spectrometry, we propose a possible mechanism for the conversion of bis(8‐methoxyquinoline‐κ²N,O)bis(thiocyanato‐κN)copper(II), [Cu(NCS)₂(C₁₀H₉NO)₂], Cu1 , to di‐μ‐methanolato‐κ⁴O:O‐bis[(8‐methoxyquinoline‐κ²N,O)(thiocyanato‐κN)copper(II)], [Cu₂(CH₃O)₂(NCS)₂(C₁₀H₉NO)₂], Cu2 , viz. [Cu(SCN)₂( L )₂] ( Cu1 ) → [Cu( L )₂] → [Cu( L )]/ L → [Cu₂(CH₃O)₂(NCS)₂( L )₂] ( Cu2 ). We screened the antitumour activities of L (8‐methoxyquinoline), Cu1 and Cu2 and found that the antiproliferative effect of Cu2 on some tumour cells was much greater than that of L and Cu1 .     

Copper(I) and copper(II) complexes with pyrazine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide

Four copper(II) complexes and one copper(I) complex with pyridine-containing pyridylalkylamide ligands N-(pyridin-2-ylmethyl)pyrazine-2-carboxamide (HL^pz) and N-(2-(pyridin-2-yl)ethyl)pyrazine-2-carboxamide (HL^pz?) were synthesized and characterized. The X-ray crystal structures of [Cu₂(L^pz)₂(4,4?-bipy)(OTf)₂] (1, OTf?=?trifluoromethanesulfonate, 4,4?-bipy?=?4,4?-bipyridine) and [Cu(L^pz)(py)₂]OTf·H₂O (2, py?=?pyridine) revealed binuclear and mononuclear molecular species, respectively, while [Cu(L^pz)(μ₂-1,1-N₃)]_n (3), [Cu(L^pz?)(μ₂-1,3-N₃)]_n (4), and [Cu(HL^pz)Cl]_n (5) are coordination polymer 1-D chains in the solid state.     

Ligand‐Modification Effects on the Reactivity,Solubility, and Stability of Organometallic Tantalum Complexes in Water

Tantalum complexes [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NMe₂)?CH)py}] ( 4 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NH₂)?CH)py}] ( 5 ), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ³‐N,O,O‐(OCH₂)(OCH)py}] (Cp*=η⁵‐C₅Me₅) with HC?CCH₂NMe₂ and HC?CCH₂NH₂, respectively. The reactions of [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(Ph)?CH)py}] ( 2 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH)py}] ( 3 ) with triflic acid (1:2 molar ratio) rendered the corresponding bis‐triflate derivatives [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(Ph)?CH₂)py}] ( 6 ) and [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH₂)py}] ( 7 ), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water‐soluble cationic complex [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH)py}]OTf ( 8 ). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H₂O){κ³‐N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH₂)py}](OTf)₂ ( 9 ). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH)py}](OTf)₂ ( 10 ), which afforded the corresponding protonolysis derivative [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH₂)py}](OTf) ( 11 ) in solution. Complex 8 reacted with CNtBu and potassium 2‐isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13 , respectively. The molecular structures of complexes 5 , 7 , and 10 were established by single‐crystal X‐ray diffraction studies.     

Synthesis,Spectroscopic, and Electrochemical Properties of Four Novel Trinuclear RuII Polypyridyl Complexes Containing Diazafluorene

Four tripodal ligands L^1–4 derived from 4,5‐diazafluoren‐9‐one were synthesized. L^1–2 formed by the reaction of 4,5‐diazafluoren‐9‐oxime with 1,3,5‐tris(bromomethyl)benzene, and 1,1,1‐tris(p‐tosyloxymethyl)propane, respectively and L^3–4 formed by the condensation of 9‐(4‐hydroxy)phenylimino‐4,5‐diazafluorene with 1,3,5‐tris(bromomethyl)benzene, and 1,1,1‐tris(p‐tosyloxymethyl)propane, respectively. Four trinuclear complexes [(bpy)₆Ru₃L^1–4](PF₆)₆ ( Ru‐L^1–4 ) were obtained by reaction of Ru(bpy)₂Cl₂ · 2H₂O with ligands L^1–4. The photophysical behaviors of these complexes were investigated by UV/Vis absorption and emission spectrometry. The complexes display metal‐to‐ligand charge transfer absorptions at 441–445 nm and emissions at 571–578 nm. Cyclic voltammetry data of the complexes show one Ru^II‐centered oxidation and three successive ligand‐centered reductions.     

N‐Heterocyclic Carbene–Phosphinidene Complexes of the Coinage Metals

Coinage metal complexes of the N‐heterocyclic carbene–phosphinidene adduct IPr ? PPh (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were prepared by its reaction with CuCl, AgCl, and [(Me₂S)AuCl], which afforded the monometallic complexes [(IPr ? PPh)MCl] (M=Cu, Ag, Au). The reaction with two equivalents of the metal halides gave bimetallic [(IPr ? PPh)(MCl)₂] (M=Cu, Au); the corresponding disilver complex could not be isolated. [(IPr ? PPh)(CuOTf)₂] was prepared by reaction with copper(I) trifluoromethanesulfonate. Treatment of [(IPr ? PPh)(MCl)₂] (M=Cu, Au) with Na(BAr^F) or AgSbF₆ afforded the tetranuclear complexes [(IPr ? PPh)₂M₄Cl₂]X₂ (X=BAr^F or SbF₆), which contain unusual eight‐membered M₄Cl₂P₂ rings with short cuprophilic or aurophilic contacts along the chlorine‐bridged M???M axes. Complete chloride abstraction from [(IPr ? PPh)(AuCl)₂] was achieved with two equivalents of AgSbF₆ in the presence of tetrahydrothiophene (THT) to form [(IPr ? PPh){Au(THT)}₂][SbF₆]₂. The cationic tetra‐ and dinuclear complexes were used as catalysts for enyne cyclization and carbene transfer reactions.     

Kupferkomplexe des neuen Chelatliganden 1‐Methyl‐2‐(2‐thiophenolato)‐1H‐benzimidazol (mtpb) und dessen Oxidationsprodukten

Copper Complexes of the New Chelate Ligand 1‐Methyl‐2‐(2‐thiophenolato)‐1H‐benzimidazole (mtpb) and of its Oxidation Products Anodic electrolysis of copper in acetonitrile in the presence of Hmtpb leads to formation of yellow [Cu₄(mtbp)₄] which was crystallized as a dichloromethane solvate with two crystallographically independent cluster molecules in the unit cell. The copper(I) atoms exhibit slightly pyramidal S₂N coordination with bridging thiolate sulfur atoms. The two clusters contain the four copper atoms arranged in a more (Cu1‐Cu4) or less (Cu5‐Cu8) distorted bisphenoidal arrangement. Reaction of mtpb^— with Cu(ClO₄)₂ under anoxic conditions also produces [Cu₄(mtpb)₄]. However, the admittance of O₂ in the reaction of mtpb^— with copper(II) acetate in methanol causes oxidation of the sulfur atoms; a square‐pyramidal configurated copper(II) complex [Cu(CH₃CO₂‐κ²O)(L₁‐κN)(L₂‐κN, O)] has been isolated and crystallographically characterized in which L₁ is the neutral sulfinic methyl ester and L₂^— is the sulfonate derived from mtpb^—.     

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.