New RuII(arene) Complexes with Halogen‐Substituted Bis‐ and Tris(pyrazol‐1‐yl)borate Ligands

[RuCl(arene)(μ‐Cl)]₂ dimers were treated in a 1:2 molar ratio with sodium or thallium salts of bis‐ and tris(pyrazolyl)borate ligands [Na(Bp)], [Tl(Tp)], and [Tl(Tp^{iPr, 4Br})]. Mononuclear neutral complexes [RuCl(arene)(κ²‐Bp)] ( 1 : arene=p‐cymene (cym); 2 : arene=hexamethylbenzene (hmb); 3 : arene=benzene (bz)), [RuCl(arene)(κ²‐Tp)] ( 4 : arene=cym; 6 : arene=bz), and [RuCl(arene)(κ²‐Tp^{iPr, 4Br})] ( 7 : arene=cym, 8 : arene=hmb, 9 : arene=bz) have been always obtained with the exception of the ionic [Ru₂(hmb)₂(μ‐Cl)₃][Tp] ( 5′ ), which formed independently of the ratio of reactants and reaction conditions employed. The ionic [Ru(CH₃OH)(cym)(κ²‐Bp)][X] ( 10 : X=PF₆, 12 : X=O₃SCF₃) and the neutral [Ru(O₂CCF₃)(cym)(κ²‐Bp)] ( 11 ) have been obtained by a metathesis reaction with corresponding silver salts. All complexes 1 – 12 have been characterized by analytical and spectroscopic data (IR, ESI‐MS, ¹H and ¹³C NMR spectroscopy). The structures of the thallium and calcium derivatives of ligand Tp, [Tl(Tp)] and [Ca(dmso)₆][Tp]₂ ? 2 DMSO, of the complexes 1 , 4 , 5′ , 6 , 11 , and of the decomposition product [RuCl(cym)(Hpz^{iPr, 4Br})₂][Cl] ( 7′ ) have been confirmed by using single‐crystal X‐ray diffraction. Electrochemical studies showed that 1 – 9 and 11 undergo a single‐electron Ru^II→Ru^III oxidation at a potential, measured by cyclic voltammetry, which allows comparison of the electron‐donor characters of the bis‐ and tris(pyrazol‐1‐yl)borate and arene ligands, and to estimate, for the first time, the values of the Lever E_L ligand parameter for Bp, Tp, and Tp^{iPr, 4Br}. Theoretical calculations at the DFT level indicated that both oxidation and reduction of the Ru complexes under study are mostly metal‐centered with some involvement of the chloride ligand in the former case, and also demonstrated that the experimental isolation of the μ³‐binuclear complex 5′ (instead of the mononuclear 5 ) is accounted for by the low thermodynamic stability of the latter species due to steric reasons.     

Aldehyde‐Assisted Hydrogen Transfer during the Formation of Hydride–Iridafurans from Alkynes and Aldehydes

The bis(ethylene) Ir^I complex [TpIr(C₂H₄)₂] ( 1 ; Tp=hydrotris(3,5‐dimethylpyrazolyl)borate) reacts with two equivalents of aromatic or aliphatic aldehydes in the presence of one equivalent of dimethyl acetylenedicarboxylate (DMAD) with ultimate formation of hydride iridafurans of the formula [TpIr(H){C(R¹)?C(R²)C(R³)O }] (R¹=R²=CO₂Me; R³=alkyl, aryl; 3 ). Several intermediates have been observed in the course of the reaction. It is proposed that the key step of metallacycle formation is a C? C coupling process in the undetected Ir^I species [TpIr{η¹‐O‐R³C(?O)H}(DMAD)] ( A ) to give the trigonal‐bipyramidal 16 e^? Ir^III intermediates [TpIr{C(CO₂Me)?C(CO₂Me)C(R³)(H)O }] ( C ), which have been trapped by NCMe to afford the adducts 11 (R³=Ar). If a second aldehyde acts as the trapping reagent for these species, this ligand acts as a shuttle in transfering a hydrogen atom from the γ‐ to the α‐carbon atom of the iridacycle through the formation of an alkoxide group. Methyl propiolate (MP) can be used instead of DMAD to regioselectively afford the related iridafurans. These reactions have also been studied by DFT calculations.     

Synthesis and Characterization of a Family of POCOP Pincer Complexes with Nickel: Reactivity Towards CO2 and Phenylacetylene

A cyclohexyl‐based POCOP pincer ligand (POCOP=cis‐1,3‐bis(di‐tert‐butylphosphinito)cyclohexyl) cyclometalates with nickel to generate a series of new POCOP‐supported Ni^II complexes, including the halide, hydride, methyl, and phenyl species. trans‐[NiCl{cis‐1,3‐bis(di‐tert‐butylphosphinito)cyclohexane}], [(POCOP)NiCl] ( 1 a ) and the analogous bromide complex ( 1 b ) were synthesized and fully characterized by NMR spectroscopy and X‐ray crystallography. Cyclic voltammetry measurements of 1 a and 1 b alongside their bis(phosphine) analogues [(PCP)NiCl] ( 2 a ) and [(PCP)NiCl] ( 2 a ) (PCP=cis‐1,3‐bis(di‐tert‐butylphosphino)cyclohexyl) indicate a reduced electron density at the metal center upon introducing electron‐withdrawing oxygen atoms in the pincer arms. The methyl [(POCOP)NiMe] ( 3 ) and phenyl [(POCOP)NiPh] ( 4 ) complexes were formed from 1 a by reaction with the corresponding organolithium reagents. 1 a also reacts with LiAlH₄ to give the hydride complex [(POCOP)NiH] ( 5 ). The methyl complex 3 reacts with phenyl acetylene to give the acetylide complex [(POCOP)NiCCPh] ( 6 ). The reactivity of compounds 3 – 5 towards CO₂ was studied. The hydride complex 5 and the methyl complex 3 both underwent CO₂ insertion to form the formate species [(POCOP)NiOCOH] ( 7 ) and acetate species [(POCOP)NiOCOCH₃] ( 8 ), respectively, although with a higher barrier of insertion in the latter case. Compound 4 was unreactive towards CO₂ even at elevated temperatures. Complexes 3 – 8 were all characterized by NMR spectroscopy and X‐ray crystallography.     

Reduction of CO2 by Pyridine Monoimine Molybdenum Carbonyl Complexes: Cooperative Metal–Ligand Binding of CO2

[(^ArPMI)Mo(CO)₄] complexes (PMI=pyridine monoimine; Ar=Ph, 2,6‐di‐iso‐propylphenyl) were synthesized and their electrochemical properties were probed with cyclic voltammetry and infrared spectroelectrochemistry (IR‐SEC). The complexes undergo a reduction at more positive potentials than the related [(bipyridine)Mo(CO)₄] complex, which is ligand based according to IR‐SEC and DFT data. To probe the reaction product in more detail, stoichiometric chemical reduction and subsequent treatment with CO₂ resulted in the formation of a new product that is assigned as a ligand‐bound carboxylate, [(PMI)Mo(CO)₃(CO₂)]^2?, by NMR spectroscopic methods. The CO₂ adduct [(PMI)Mo(CO)₃(CO₂)]^2? could not be isolated and fully characterized. However, the C?C coupling between the CO₂ molecule and the PDI ligand was confirmed by X‐ray crystallographic characterization of one of the decomposition products of [(PMI)Mo(CO)₃(CO₂)]^2?.     

Functionalization of Non‐activated C?H Bonds of Alkanes: An Effective and Recyclable Catalytic System Based on Fluorinated Silver Catalysts and Solvents

The complexes F_n‐TpAg(L) (F_n‐Tp=a perfluorinated hydrotris(indazolyl) borate ligand; L=acetone or tetrahydrofuran) efficiently catalyze the functionalization of non‐activated alkanes such as hexane, 2,3‐dimethylbutane, or 2‐methylpentane by insertion of CHCO₂Et units (from N₂CHCO₂Et, ethyl diazoacetate, EDA) into their C? H bonds. The reactions are quantitative (EDA‐based), with no byproducts derived from diazo coupling being formed. In the case of hexane, the functionalization of the methyl C? H bonds has been achieved with the highest regioselectivity known to date with this diazo compound. This catalytic system also operates under biphasic conditions by using fluorous solvents such as Fomblin or perfluorophenanthrene. Several cycles of catalyst recovery and reuse have been performed, with identical chemo‐ and regioselectivities.     

Small Molecule Activation by POCOP‐Nickel Complexes

This contribution describes the reactivities of CO₂, CO, O₂, and ArNC with the pincer‐type complexes [(κ^P,κ^C,κ^P′‐POCOP)NiX] (POCOP=(R₂POCH₂)₂CH; R=iPr; X=OSiMe₃, NArH; Ar=2,6‐iPr₂C₆H₃). Reaction of the amido derivative with CO₂ and CO leads to a simple insertion into the Ni?N bond to give stable carbamate and carbamoyl derivatives, respectively, the pincer ligand backbone remaining intact in both cases. In contrast, the analogous reactions with the siloxide derivative produced kinetically labile insertion products that either revert to the starting material (in the case of CO₂) or react further to give the mixed‐valent, dinickel species [(POCOP)Ni^II{μ,κ^O,κ^P,κ^P′‐OCOCH(CH₂CH₂OPR₂)₂}Ni⁰(CO)₂]. The zero‐valent center in the latter compound is ligated by a new ligand arising from transformation of the POCOP ligand backbone. The carbonylation and carboxylation of the siloxido derivative also produced minor quantities of a side‐product identified as the trinickel species, [{(η³‐allyl)Ni(μ^O,κ^P‐R₂PO)₂}₂Ni], arising from total dismantling of the POCOP ligand. Similar reactivities were observed with isonitrile, ArNC: reaction with the siloxido derivative resulted in a complex sequence of steps involving initial insertion, a 1,3‐hydrogen shift, and an Arbuzov rearrangement to give [Ni(CNAr)₄] and a methacrylamide based on fragments of the POCOP ligand. Oxygenation of the amido and siloxido derivatives led to the phosphinate derivative, [(POCOP)Ni(OP(O)R₂)], arising from oxidative transformation of the original ligand frame; the reaction with the Ni‐NHAr derivative also gave ArHNP(O)R₂ through a complex N?P bond‐forming reaction.     

Aryl‐Copper(III)‐Acetylides as Key Intermediates in CCsp Model Couplings under Mild Conditions

The mechanism of copper‐mediated Sonogashira couplings (so‐called Stephens–Castro and Miura couplings) is not well understood and lacks clear comprehension. In this work, the reactivity of a well‐defined aryl‐Cu^III species ( 1 ) with p‐R‐phenylacetylenes (R=NO₂, CF₃, H) is reported and it is found that facile reductive elimination from a putative aryl‐Cu^III‐acetylide species occurs at room temperature to afford the C_aryl?C_sp coupling species ( I_R ), which in turn undergo an intramolecular reorganisation to afford final heterocyclic products containing 2H‐isoindole ( P , P , P_Ha ) or 1,2‐dihydroisoquinoline ( P_Hb ) substructures. Density Functional Theory (DFT) studies support the postulated reductive elimination pathway that leads to the formation of C?C_sp bonds and provide the clue to understand the divergent intramolecular reorganisation when p‐H‐phenylacetylene is used. Mechanistic insights and the very mild experimental conditions to effect C_aryl?C_sp coupling in these model systems provide important insights for developing milder copper‐catalysed C_aryl?C_sp coupling reactions with standard substrates in the future.     

Atomic Dopants Involved in the Structural Evolution of Thermally Graphitized Graphene

Thermally doped nitrogen atoms on the sp²‐carbon network of reduced graphene oxide (rGO) enhance its electrical conductivity. Atomic structural information of thermally annealed graphene oxide (GO) provides an understanding on how the heteroatomic doping could affect electronic property of rGO. Herein, the spectroscopic and microscopic variations during thermal graphitization from 573 to 1 373 K are reported in two different rGO sheets, prepared by thermal annealing of GO (rGO_therm) and post‐thermal annealing of chemically nitrogen‐doped rGO (post‐therm‐rGO). The spectroscopic transitions of rGO in thermal annealing ultimately showed new oxygen‐functional groups, such as cyclic edge ethers and new graphitized nitrogen atoms at 1 373 K. During the graphitization process, the microscopic evolution resolved by scanning tunneling microscopy (STM) produced more wrinkled surface morphology with graphitized nanocrystalline domains due to atomic doping of nitrogen on a post‐therm‐rGO sheet. As a result, the post‐therm‐rGO‐containing nitrogen showed a less defected sp²‐carbon network, resulting in enhanced conductivity, whereas the rGO_therm sheet containing no nitrogen had large topological defects on the basal plane of the sp²‐carbon network. Thus, our investigation of the structural evolution of original wrinkles on a GO sheet incorporated into the graphitized N‐doped rGO helps to explain how the atomic doping can enhance the electrical conductivity.     

Reaction site diversity in the reactions of titanium hydrazides with organic nitriles, isonitriles and isocyanates: Ti=N(α) cycloaddition, Ti=N(α) insertion and N(α) -N(β) bond cleavage

We report a range of new transformations of the diamide–amine supported Ti?NNPh₂ functional group with a variety of unsaturated substrates, along with DFT studies of the key mechanisms. Reaction of [Ti(N₂N^py)(NNPh₂)(py)] ( 4 , N₂N^py=(2‐NC₅H₄)CMe(CH₂NSiMe₃)₂; py=pyridine) with MeCN gave the dimeric species [Ti₂(N₂N^py)₂{μ‐NC(Me)(NNPh₂)}₂] through a [2+2] cycloaddition process. Reaction of 4 or [Ti(N₂N^Me)(NNPh₂)(py)] ( 5 , N₂N^Me=MeN(CH₂CH₂NSiMe₃)₂) with fluorinated benzonitriles gave the terminal hydrazonamide complexes [Ti(N₂N^R){NC(Ar)NNPh₂}(py)] (R=py or Me; Ar=2,6‐C₆H₃F₂ or C₆F₅). DFT studies showed that this proceeds through an overall [2+2] cycloaddition–reverse cycloaddition, resulting in net insertion of ArCN into the Ti?N_α bonds of the respective hydrazides. Reaction of 4 with a mixture of MeCN and PhCCMe gave the metallacycle [Ti(N₂N^py){NC(Me)C(Ph)C(Me)NNPh₂}] by sequential coupling of Ti?NNPh₂ with PhCCMe and then MeCN. A related product, [Ti(N₂N^py){NC(Me)C(Ar^F)C(H)NNPh₂}], was formed by insertion of MeCN into the Ti? C bond of the isolated azatitanacyclobutene [Ti(N₂N^py){N(NPh₂)C(H)C(Ar^F)}] (Ar^F=3‐C₆H₄F). Reaction of 4 with two equivalents of B(Ar)₃ (Ar=C₆F₅) formed the zwitterionic borate [Ti(N₂N^py){η²‐N(NPh₂)B(Ar)₃}] by electrophilic attack at N_α. Compounds 4 and 5 reacted with tBuNC and/or XylNC (Xyl=2,6‐C₆H₃Me₂) to give the N_α? N_β bond cleavage products, [Ti(N₂N^R)(NCNR′)(NPh₂)] (R=py or Me; R′=tBu or Xyl), containing metallated carbodiimide ligands. DFT studies of these reactions found an initial addition of RNC across Ti?N_α followed by N_β coordination, and finally complete N_α transfer from the NNPh₂ to the RNC fragment. Reaction of 5 with Ar′NCE (E=O, S, Se; Ar′=2,6‐C₆H₃iPr₂) gave the [2+2] cycloaddition products [Ti(N₂N^Me){N(NPh₂)C(NAr′)O}(py)] and [Ti(N₂N^Me){N(NPh₂)C(NAr′)E}] (E=S or Se), which did not undergo further transformation of the Ti? N? NPh₂ moiety.     

The First Lutetacyclopentadienes: Synthesis,Structure, and Diversified Insertion/CH Activation Reactivity

The first well‐defined lutetacyclopentadienes are synthesised from pentamethylcyclopentadienyl lithium (Cp*Li), 1,4‐dilithio‐1,3‐butadienes, and LuCl₃. The lutetacyclopentadiene shows excellent reactivity towards some small molecules, such as pivalaldehyde, Se, carbon dioxide, and isonitrile to efficiently construct 3‐, 5‐, 7‐, 8‐, and 9‐membered rare‐earth metallacycles. Both monoinsertion and double‐insertion of two Lu?C bonds are observed. Specially, the reaction between lutetacyclopentadiene and isonitrile afforded [3,5,5]‐fused metallacycles. The distinguished reactivity can be attributed to the highly ionic character and the cooperative reactivity of two Lu?C bonds.     

Transition‐Metal‐Catalyzed CH Bond Functionalizations: Feasible Access to a Diversity‐Oriented β‐Carboline Library

Diversification of the β‐carboline skeleton has been demonstrated to assemble a β‐carboline library starting from the tetrahydro‐β‐carboline framework. This strategy affords feasible access to heteroaryl‐, aryl‐, alkenyl‐, or alkynyl‐substituted β‐carbolines at the C1, C3, or C8 position through three categorically different types of transition‐metal‐catalyzed C?C bond‐forming reactions, in the presence of multiple potentially reactive positions. These site‐selective functionalizations include; 1) the Cu‐catalyzed C1/C3‐selective decarboxylative C?C and C?C_sp coupling of hexahydro‐β‐carboline‐3‐carboxylic acid with a C?H bond of a heteroarene or terminal alkyne; 2) the chelation‐assisted Pd‐catalyzed C1/C8‐selective C?H arylation of hexahydro‐β‐carboline with aryl boron reagents; and 3) the chelation‐assisted Pd‐catalyzed C1/C3‐selective oxidative C?H/C?H cross‐coupling of β‐carboline‐N‐oxide with arenes, heteroarenes, or alkenes. The saturated structural feature of the hexahydro‐β‐carboline framework can increase reactivity and control site selectivity. The robustness of these approaches has been demonstrated through the synthesis of hyrtioerectine analogues and perlolyrine. We believe that these strategies could provide inspiration for late‐stage diversifications of bioactive core scaffolds.     

Acceleration of Reductive Elimination of [Ar‐Pd‐C] by a Phosphine/Electron‐Deficient Olefin Ligand: A Kinetic Investigation

Dramatic rate enhancement of reductive elimination of [Ar‐Pd‐C] was observed in the presence of a phosphine/electron‐deficient olefin ligand. Through systematic kinetic investigations of the Negishi coupling of ethyl 2‐iodobenzoate with alkylzinc chlorides (see scheme), the rate constants for reductive elimination of [Ar‐Pd‐C] were determined to be greater than 0.3 s^?1, which is about four or five orders of magnitude greater than values reported previously.

     

1H, 13C and 15N nuclear magnetic resonance coordination shifts in Au(III), Pd(II) and Pt(II) chloride complexes with phenylpyridines

¹H, ¹³C and ¹⁵N nuclear magnetic resonance studies of gold(III), palladium(II) and platinum(II) chloride complexes with phenylpyridines (PPY: 4‐phenylpyridine, 4ppy; 3‐phenylpyridine, 3ppy; and 2‐phenylpyridine, 2ppy) having the general formulae [Au(PPY)Cl₃], trans‐/cis‐[Pd(PPY)₂Cl₂] and trans‐/cis‐[Pt(PPY)₂Cl₂] were performed and the respective chemical shifts (δ, δ and δ) reported. ¹H, ¹³C and ¹⁵N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: , , ) were discussed in relation to the type of the central atom (Au(III), Pd(II) and Pt(II)), geometry (trans‐/cis‐) and the position of a phenyl group in the pyridine ring system. Copyright © 2009 John Wiley & Sons, Ltd.     

Tunable Keplerate Type‐Cluster “Mo132” Cavity with Dicarboxylate Anions

The internal functionalization of the Keplerate‐type capsule Mo₁₃₂ has been carried out by ligand exchange leading to the formation of glutarate and succinate containing species isolated as ammonium or dimethylammonium salts. Solution NMR analysis is consistent with asymmetric inner dicarboxylate ions containing one carboxylato group grafted onto the inner side of the spheroidal inorganic shell while the second hangs toward the center of the cavity. Such a disposition has been confirmed by the single‐crystal X‐ray diffraction analysis of the glutarate containing {Mo₁₃₂} species. A detailed NMR solution study of the ligand‐exchange process allowed determining the binding constant K_L of acetate (AcO^?), succinate (HSucc^?) or glutarate (HGlu^?) ligands at the 30 inner coordinating sites, which vary such as K<K<K‐supported by the associated thermodynamic parameters Δ_rS* and Δ_rH*. Such a variation is mainly explained by a positive entropic gain attenuated by unfavorable steric effect. Furthermore, these results are completed by ¹H DOSY and ¹H EXSY NMR experiments which are in agreement with bulky guests firmly trapped within the cavity. At last, variable temperature ¹H NMR study below 290 K revealed a striking line broadening occurring abruptly within a 5 K range. Such an effect appears closely related to the presence of the ammonium cations suspected to be present within the cavity and then has been interpreted as an inner‐phase transition leading to a frozen state.     

Stable Mixed‐Valent Radicals from Platinum(II) Complexes of a Bis(dioxolene) Ligand

Three diplatinum(II) complexes [{PtL}₂(μ‐thea)] (H₄thea=2,3,6,7‐tetrahydroxy‐9,10‐dimethyl‐9,10‐dihydro‐9,10‐ethanoanthracene) have been prepared, with diphosphine or bipyridyl “L” co‐ligands. One‐electron oxidation of these complexes gave radical cations containing a mixed‐valent [thea]^3? ligand with discrete catecholate and semiquinonate centers separated by quaternary methylene spacers. The electronic character of these radicals is near the Robin–Day class II/III border determined by UV/Vis/NIR and EPR spectroscopies. Crystal‐structure determinations and a DFT calculation imply that oxidation of the thea^4? ligand may lead to an increased through‐space interaction between the dioxolene π systems.     

Addition of Ethylene or Hydrogen to a Main‐Group Metal Cluster under Mild Conditions

Reaction of the tin cluster Sn₈(Ar)₄ (Ar=C₆H₂‐2,6‐(C₆H₃‐2,4,6‐Me₃)₂) with excess ethylene or dihydrogen at 25 °C/1 atmosphere yielded two new clusters that incorporated ethylene or hydrogen. The reaction with ethylene yielded Sn₄(Ar)₄(C₂H₂)₅ that contained five ethylene moieties bridging four aryl substituted tin atoms and one tin–tin bond. Reaction with H₂ produced a cyclic tin species of formula (Sn(H)Ar)₄, which could also be synthesized by the reaction of {(Ar)Sn(μ‐Cl)}₂ with DIBAL‐H. These reactions represent the first instances of direct reactions of isolable main‐group clusters with ethylene or hydrogen under mild conditions. The products were characterized in the solid state by X‐ray diffraction and IR spectroscopy and in solution by multinuclear NMR and UV/Vis spectroscopies. Density functional theory calculations were performed to explain the reactivity of the cluster.     

Electrophilicity versus Electrofugality of Tritylium Ions in Aqueous Acetonitrile

First‐order rate constants k_w for the reactions of a series of donor‐substituted triphenylmethylium (tritylium) ions with water in aqueous acetonitrile have been determined photometrically at 20 °C using stopped‐flow and laser‐flash techniques. The rate constants follow the linear free energy relationship log k(20 °C)=s(N+E). The reactivities k_w of the methyl‐ and methoxy‐substituted tritylium ions towards water correlate linearly with the corresponding pK values with a Leffler–Hammond coefficient α=δΔG^≠/δΔG⁰ of 0.62. The amino‐substituted compounds react more slowly than expected from the correlation of the less stabilized systems. Quantum chemical calculations of tritylium ions and the corresponding triarylmethanols and 1,1,1‐triarylethanes have been performed at the MP2(FC)/6‐31+G(2d,p)//B3LYP/6‐31G(d,p) level. The calculated gas‐phase hydroxide and methyl anion affinities of the tritylium ions correlate linearly with a slope of unity, indicating that the relative anion affinities do not depend on the nature of the anion. The pK values of the methyl‐ and methoxy‐substituted tritylium ions correlate linearly with the calculated gas‐phase hydroxide affinities, and the slope of this correlation shows that the differences in carbocation stabilities in the gas phase are attenuated to 66 % in solution. Mono‐ and bis(dimethylamino)‐substituted derivatives deviate from this correlation; their pK values are higher than expected from their calculated gas‐phase hydroxide affinities, which is explained by the extraordinary solvation of unsymmetrically amino‐substituted tritylium ions. Complete free‐energy profiles for the solvolyses of substituted trityl benzoates in 90:10 (v/v) acetonitrile/water have been constructed.     

On the ν1/2 ν2 Resonance in the Complex of Carbon Dioxide with Dimethyl Ether

Infrared and Raman spectra of solutions in liquid argon and krypton containing dimethyl ether or its fully deuterated isotopomer and ¹²CO₂ or ¹³CO₂ are investigated. The spectra lead to new data on the ν₁/2 ν₂ resonances appearing in the complex of CO₂ with the ether. The experimental data, and their interpretation, is supported by MP2/6‐311++G(2d,2p) calculations of the cubic and quartic force constants and of the first and higher order dipole moment derivatives required for the modelling of the Fermi and Darling‐Dennison resonances observed.     

Shape‐Selective Interception by Hydrocarbons of the O2‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Picky ferryl : The complex [Fe(Tp)(BF)] (Tp=hydrotris(3,5‐diphenylpyrazolyl)borate; BF=benzoylformate) reacts with O₂ to generate an oxidant (see picture; O red, pink; Fe yellow; N blue; C gray; H white) that oxidizes added hydrocarbons shape‐selectively. Discrimination derives from a cleft formed by two phenyl groups of the Tp ligand, favoring oblate spheroidal substrates.