A new technique for differentiating between 2J(C,H) and 3/4J(C,H) connectivities

We present a new pulse sequence that yields two simultaneously detected types of long‐range correlation spectra. The one spectrum is to show all ⁿJ(C,H) connectivities and the other is to show exclusively ²J(C,H) connectivities. The method is demonstrated by using strychnine as a test sample. A comparison with HMBC shows that the ²J(C,H)/ⁿJ(C,H) experiment supplies a ⁿJ(C,H) spectrum that is of equal standard with regard to sensitivity and spectral information. The additional ²J(C,H) spectrum allows the disentanglement of ²J(C,H) and ⁿJ(C,H) signals (n > 2) in HMBC type spectra, which greatly simplifies signal assignment and structure elucidation in general. Copyright © 2003 John Wiley & Sons, Ltd.     

4-Hydroxycoumarin/2-hydroxychromone tautomerism: Infrared spectra of 2-13c and 3-D labeled 4-hydroxycoumarin and its anion

Bands with primarily v (C=O) and v (C=O) character in the spectra of 4-hydroxycoumarin and its anion were identified by isotopic substitution with either ¹³C or deuterium. Two bands of each type were found for spectra of 4-hydroxycoumarin in solution in chloroform, dioxane, or dimethylsulfoxide, with v (C=O) at 1704–1733 cm^?1 and ～ 1567 cm^?1. Two bands, at 1618 and 1559 cm^?1, are associated with v (C=C) in the spectrum of crystalline 4-hydroxycoumarin monohydrate, but only a single v (C=O) band at ～ 1655 cm^?1 was observed. Anhydrous 4-hydroxycoumarin has v (C=O) bands at ～ 1700 cm^?1 and a shoulder at ～ 1670 cm^?1. The strong band at 1660 cm^?1 in the spectrum of 4-hydroxycommarin anion in dimethylsulfoxide solution is due to a delocalized v (O = C = O) vibration, whereas the band at 1555 cm^?1 has partial v (C=C) character and involves C(3) but not C(2), supporting a fully delocalized char structure for the anion. No evidence for the existence of the 2-hydroxychromone tautomer was found, except in the case of anhydrous 4-hydroxycoumarin in the solid state.     

Structure Determination of an AgI‐Mediated Cytosine–Cytosine Base Pair within DNA Duplex in Solution with 1H/15N/109Ag NMR Spectroscopy

The structure of an Ag^I‐mediated cytosine–cytosine base pair, C–Ag^I–C, was determined with NMR spectroscopy in solution. The observation of 1‐bond ¹⁵N‐¹⁰⁹Ag J‐coupling (¹J(¹⁵N,¹⁰⁹Ag): 83 and 84 Hz) recorded within the C–Ag^I–C base pair evidenced the N3–Ag^I–N3 linkage in C–Ag^I–C. The triplet resonances of the N4 atoms in C–Ag^I–C demonstrated that each exocyclic N4 atom exists as an amino group (?NH₂), and any isomerization and/or N4–Ag^I bonding can be excluded. The 3D structure of Ag^I–DNA complex determined with NOEs was classified as a B‐form conformation with a notable propeller twist of C–Ag^I–C (?18.3±3.0°). The ¹⁰⁹Ag NMR chemical shift of C‐Ag^I‐C was recorded for cytidine/Ag^I complex (δ(¹⁰⁹Ag): 442 ppm) to completed full NMR characterization of the metal linkage. The structural interpretation of NMR data with quantum mechanical calculations corroborated the structure of the C–Ag^I–C base pair.     

Vicinal 13C?13C spin–spin coupling constants of 1-butanols. Conformational and substituent effects

A series of (>90% isotopic purity) ¹³C-labeled aliphatic alcohols of the general structure C? C? C? ¹³C? OH were synthesized and studied by ¹³C n.m.r. to obtain all ¹³C? ¹³C couplings involving the labeled carbon. The ²J(CC) values were small (<0.5 Hz) and contrast with the large (up to 2.7 Hz) ²J(CC) values obtained in a previous study for 2-butanols. The ³J(CC) values, however, were strikingly similar in the two classes of compounds with respect both to magnitude and to conformational dependency. Thus, the effect of the hydroxyl substituent on ³J(CC) values is small.     

Substituent effects on nuclear spin–spin carbon–carbon coupling constants in derivatives of acetylene

¹J(¹³C?¹³C) nuclear spin–spin coupling constants in derivatives of acetylene have been measured from natural abundance ¹³C NMR spectra and in one case (triethylsilyllithiumacetylene) from the ¹³C NMR spectrum of a ¹³C-enriched sample. It has been found that the magnitude of J(C?C) depends on the electronegativity of the substituents at the triple bond. The equation ¹J(¹³C?¹³C) = 43.38 E_x + 17.33 has been derived for one particular series of the compounds Alk₃SiC?CX, where X denotes Li, R₃Sn, R₃Si, R₃C, I, Br or Cl. The ¹J(C?C) values found in this work cover a range from 56.8 Hz (in Et₃SiC?Li) to 216.0 Hz (in PhC?CCI). However, the ¹J(C?C) vs E_x equation combined with the Egli–von Philipsborn relationship allows the calculation of the coupling constants in Li₂C₂ (32 Hz) and in F₂C₂ (356 Hz). These are probably the lowest and the highest values, respectively, which can be attained for ¹J(CC) across a triple bond. The unusually large changes of the ¹J(C?C) values are explained in terms of substituent effects followed by a re-hybridization of the carbons involved in the triple bond. INDO FPT calculations performed for two series of acetylene derivatives, with substituents varied along the first row of the Periodic Table, corroborate the conclusions drawn from the experimental data.     

Carbon-13 nuclear magnetic resonance spectra of exo- and endo-2-norbornyltrimethyl-stannanes: Corrected assignments

The ¹³C NMR spectra of pure exo-2-norbornyltrimethylstannane and a mixture of the exo- and endo-isomers have been recorded. ¹H–¹³C polarization transfer spectra have been obtained and require the previously reported assignments for C-3 and C-4 in the exo-isomer to be reversed. The reported assignments for the endo-isomer are correct. The new assignment for C-4-exo [with J(¹¹⁹Sn,¹³C) vic=12 Hz, instead of the previously assigned J(vic)=23 Hz], has a very minor effect on the nature of the Karplus curve [for ³J(¹¹⁹Sn,¹³C)] generated previously.     

Determination of 13C concentration in biological materials using infrared absorption method

Tracer experiments on the transfer of carbon from culture solution to Daphnia magna through phytoplankton have been carried out using ¹³C and infrared absorption method. The purpose of this experiment is to investigate the experimental systems for the use of ¹³C in aquatic system. Daphnia magna was cultured in a 100 ml of solution containing phytoplankton and 20 mg of NaH¹³CO₃ for 24 hours in the light and dark conditions (2000 lux, 14 hour light and 10 hours dark at 25 C). The concentration of ¹³C in Daphnia magna under light condition was about 2.0% (atom% excess), while in the dark condition ¹³C tracer was not detected. The concentration of ¹³C in phytoplankton under light condition was around 20%. It was suggested that ¹³C added as carbonate in the culture solution was photosynthetically assimilated by phytoplankton and then transferred to Daphnia magna. Using this system, the effect of UV-B exposure on the ¹³C uptake of Daphnia magna has been examined. The UV-B intensity was 95 mW/cm² and exposure time was 15, 30, and 60 minutes. The concentration of ¹³C in Daphnia magna decreased with increasing exposure time. The Daphnia magna exposed to UV-B for 15 minutes intakes phytoplankton as much as control, while 30 minutes and 60 minutes exposures were lower than control. The lower concentrations of ¹³C observed in Daphnia magna were due to less intake of phytoplankton caused by the UV-B exposure.     

High-Resolution Solid-State NMR Characterization of Morphology in Annealed Polylactic Acid

Single-pulse ¹³C NMR spectra and spin-lattice relaxation times T₁(¹H), detected indirectly via ¹³C carbons, and T₁(¹³C) were measured at 31°C for virgin pelletized and annealed polylactic acid (PLA) samples using the magic-angle spinning technique. The structural relaxation resulting in more regular crystals with narrower conformation distribution and increase in the lamellae thickness and crystallinity brought about by annealing at 100°C was deduced from the narrowing of the ¹³C NMR lines and proton spin-lattice relaxation times T₁(¹H). The spin-lattice relaxation times T₁(¹³C) related to the respective carbons of the α-polymorph of PLA are also discussed in the study.     

C and N stable isotope variation in urine and milk of cattle depending on the diet

The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The δ ¹³C values of milk and urine were dependent on different feeding regimes based on C₃ or C₄ plants. The δ ¹³C values are more negative under grass feeding than under maize feeding. The δ ¹³C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed milk and urine samples are enriched in ¹³C relative to the feed, whereas under maize feeding the ¹³C/¹²C ratio of urine is in the same range and milk is depleted in ¹³C relative to the diet. The difference between the ¹⁵N/¹⁴N ratios for the two feeding regimes is less pronounced than the ¹³C/¹²C ratios. The δ ¹⁵N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences between the two feeding regimes.     

Membrane permeation continuous‐flow isotope ratio mass spectrometry for on‐line carbon isotope ratio determination

Gaseous membrane permeation (MP) technologies have been combined with continuous‐flow isotope ratio mass spectrometry for on‐line δ¹³C measurements. The experimental setup of membrane permeation‐gas chromatography/combustion/isotope ratio mass spectrometry (MP‐GC/C/IRMS) quantitatively traps gas streams in membrane permeation experiments under steady‐state conditions and performs on‐line gas transfer into a GC/C/IRMS system. A commercial polydimethylsiloxane (PDMS) membrane sheet was used for the experiments. Laboratory tests using CO₂ demonstrate that the whole process does not fractionate the C isotopes of CO₂. Moreover, the δ¹³C values of CO₂ permeated on‐line give the same isotopic results as off‐line static dual‐inlet IRMS δ¹³C measurements. Formaldehyde generated from aqueous formaldehyde solutions has also been used as the feed gas for permeation experiments and on‐line δ¹³C determination. The feed‐formaldehyde δ¹³C value was pre‐determined by sampling the headspace of the thermostated aqueous formaldehyde solution. Comparison of the results obtained by headspace with those from direct aqueous formaldehyde injection confirms that the headspace sampling does not generate isotopic fractionation, but the permeated formaldehyde analyzed on‐line yields a ¹³C enrichment relative to the feed δ¹³C value, the isotopic fractionation being 1.0026 ± 0.0003. The δ¹³C values have been normalized using an adapted two‐point isotopic calibration for δ¹³C values ranging from ?42 to ?10‰. The MP‐GC/C/IRMS system allows the δ¹³C determination of formaldehyde without chemical derivatization or additional analytical imprecision. Copyright © 2009 John Wiley & Sons, Ltd.     

Reconstructing bulk isotope ratios from compound‐specific isotope ratios

Carbon isotope analysis by bulk elemental analysis coupled with isotope ratio mass spectrometry has been the mainstay of δ¹³C analyses both at natural abundance and in tracer studies. More recently, compound‐specific isotope analysis (CSIA) has become established, whereby organic constituents are separated online by gas or liquid chromatography before oxidation and analysis of CO₂ for constituent δ¹³C. Theoretically, there should be concordance between bulk δ¹³C measurements and carbon‐weighted δ¹³C measurements of carbon‐containing constituents. To test the concordance between the bulk and CSIA, fish oil was chosen because the majority of carbon in fish oil is in the triacylglycerol form and ～95% of this carbon is amenable to CSIA in the form of fatty acids. Bulk isotope analysis was carried out on aliquots of oil extracted from 55 fish samples and δ¹³C values were obtained. Free fatty acids (FFAs) were produced from the oil samples by saponification and derivatised to fatty acid methyl esters (FAMEs) for CSIA by gas chromatography/combustion/isotope ratio mass spectrometry. A known amount of an internal standard (C15:0 FAME) was added to allow analyte quantitation. This internal standard was also isotopically calibrated in both its FFA (δ¹³C = ?34.30‰) and FAME (δ¹³C = ?34.94‰) form. This allowed reporting of FFA δ¹³C from measured FAME δ¹³C values. The bulk δ¹³C was reconstructed from CSIA data based on each FFA δ¹³C and the relative amount of CO₂ produced by each analyte. The measured bulk mean δ¹³C (SD) was ?23.75‰ (1.57‰) compared with the reconstructed bulk mean δ¹³C of ?23.76 (1.44‰) from CSIA and was not significantly different. Further analysis of the data by the Bland‐Altman method did not show particular bias in the data relative to the magnitude of the measurement. Good agreement between the methods was observed with the mean difference between methods (range) of 0.01‰ (?1.50 to 1.30). Copyright © 2010 John Wiley & Sons, Ltd.     

Light Energy Collection in a Porphyrin–Imide–Corrole Ensemble

An assembly consisting of three units, that is, a meso‐substituted corrole ( C3 ), 1,8 naphthaleneimide ( NIE ), and a Zn porphyrin ( ZnP ), has been synthesized. NIE is connected to C3 through a 1,3‐phenylene bridge and to the ZnP unit through a direct C? C bond. The convergent synthetic strategy includes the preparation of a trans‐A₂B‐corrole possessing the imide unit, followed by Sonogashira coupling with a meso‐substituted A₃B‐porphyrin. The photophysical processes in the resulting triad ZnP-NIE-C3 are examined and compared with those of the corresponding C3-NIE dyad and the constituent reference models C3 , NIE , and ZnP . Excitation of the NIE unit in C3-NIE leads to a fast energy transfer of 98 % efficiency to C3 with a rate k_en=7.5×10¹⁰ s^?1, whereas excitation of the corrole unit leads to a reactivity of the excited state identical to that of the model C3 , with a deactivation rate to the ground state k=2.5×10⁸ s^?1. Energy transfer to C3 and to ZnP moieties follows excitation of NIE in the triad ZnP-NIE-C3 . The rates are k_en=7.5×10¹⁰ s^?1 and k_en=2.5×10¹⁰ s^?1 for the sensitization of the C3 and ZnP unit, respectively. The light energy transferred from NIE to Zn porphyrin unit is ultimately funneled to the corrole component, which is the final recipient of the excitation energy absorbed by the different components of the array. The latter process occurs with a rate k_en=3.4×10⁹ s^?1 and 89 % efficiency. Energy transfer processes take place in all cases by a Förster (dipole–dipole) mechanism. The theory predicts quite satisfactorily the rate for the ZnP/C3 couple, where components are separated by about 23 Å, but results in calculated rates that are one to two orders of magnitude higher for the couples NIE/ZnP (D/A) and NIE/C3, which are separated by distances of about 14 and 10 Å, respectively.     

Analysing the isotopic life history of the alpine ungulates Capra ibex and Rupicapra rupicapra rupicapra through their horns

The horn of ungulate grazers offers a valuable isotopic record of their diet and environment. However, there have been no reports of the spatio‐temporal variation of the isotopic composition of horns. We investigated patterns of carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition along and perpendicular to the horn axis in Capra ibex and Rupicapra rupicapra rupicapra to assess the effects of animal age, within‐year (seasonal) and inter‐annual variation, natural contamination and sampling position on horn isotope composition. Horns of male C. ibex (n = 23) and R. r. rupicapra (n = 1) were sampled longitudinally on the front (only R. r. rupicapra) and back side and on the surface and sub‐surface. The sides of the R. r. rupicapra horn did not differ in δ¹³C. In both species, the horn surface had a 0.15‰ lower δ¹³C and a higher carbon‐to‐nitrogen (C/N) ratio than the sub‐surface. Washing the horn with water and organic solvents removed material that caused these differences. With age, the δ¹⁵N of C. ibex horns increased (+0.1‰ year^?1), C/N ratio increased, and ¹³C discrimination relative to atmospheric CO₂ (¹³Δ) increased slightly (+0.03‰ year^?1). Geostatistical analysis of one C. ibex horn revealed systematic patterns of inter‐annual and seasonal ¹³C changes, but ¹⁵N changed only seasonally. The work demonstrates that isotopic signals in horns are influenced by natural contamination (δ¹³C), age effects (¹³Δ and δ¹⁵N), and seasonal (δ¹³C and δ¹⁵N) and inter‐annual variation (δ¹³C). The methods presented allow us to distinguish between these effects and thus allow the use of horns as isotopic archives of the ecology of these species and their habitat. Copyright © 2009 John Wiley & Sons, Ltd.     

Carboxy Group as a Remote and Selective Chelating Group for C−H Activation of Arenes

The first example of carboxy group assisted, remote‐selective C(sp²)?H activation with a Pd^II catalyst has been developed and proceeds through a possible κ² coordination of the carboxy group, thus suppressing the ortho‐C?H activation through κ¹ coordination. Besides meta‐C?H olefination, direct meta‐arylation of hydrocinnamic acid derivatives with low‐cost aryl iodides has been achieved for the first time. These findings may motivate the exploration of novel reactivities of the carboxy assisted C?H activation reactions with intriguing selectivities.     

Surface oxidation process of a diamond‐like carbon film analyzed by difference X‐ray photoelectron spectroscopy

Difference X‐ray photoelectron spectroscopy (D‐XPS) revealed the surface oxidation process of a diamond‐like carbon (DLC) film. Evaluation of surface functional groups on DLC solely by the C 1s spectrum is difficult because the spectrum is broad and has a secondary asymmetric lineshape. D‐XPS clarified the subtle but critical changes at the DLC surface caused by wet oxidation. The hydroxyl (C―OH) group was dominant at the oxidized surface. Further oxidized carbonyl (C?O) and carboxyl (including carboxylate) (COO) groups were also obtained; however, the oxidation of C?O to COO was suppressed to some extent because the reaction required C―C bond cleavage. Wet oxidation cleaved the aliphatic hydrogenated and non‐hydrogenated sp² carbon bonds (C―H sp² and C―C sp²) to create a pair of C―OH and hydrogenated sp³ carbon (C―H sp³) bonds. The reaction yield for C―H sp² was superior at the surface, suggesting that the DLC film was hydrogen rich at the surface. Oxidation of aromatic sp² rings or polycyclic aromatic hydrocarbons such as nanographite to phenols did not occur because of their resonance stabilization with electron delocalization. Non‐hydrogenated sp³ carbon (C―C sp³) bonds were not affected by oxidation, suggesting that these bonds are chemically inert. Copyright © 2014 John Wiley & Sons, Ltd.     

1H and 13C NMR studies on 1,3,2-dioxarsolanes

The ¹H and ¹³C NMR spectra of a series of 1,3,2-dioxarsolanes have been obtained at 2.1 T and some at 9.4 T. The chemical shifts and spin-spin coupling constants have been obtained from complete spectral analyses of the ¹H and proton-coupled ¹³C spectra. The spectral data are interpreted on the basis of two rapidly interconverting half-chair conformers with a pseudoaxial substituent at arsenic. Unique assignment of syn/anti or cis/trans geometries have been made from ¹H or ¹³C NMR spectroscopy alone. The syn and trans isomers of the 4-methyl- and 4,5-dimethyl-1,3,2-dioxarsolanes, respectively, appear to be conformationally biased towards the forms with pseudoequatorial methyl groups. The general trends in the geminal and vicinal ¹H? ¹H and ¹³C? ¹H coupling constants are interpreted in terms of stereospecific, electronegativity and lone-pair effects of the oxygen heteroatoms and conformational factors. The NMR data on the 1,3,2-dioxarsolanes are discussed with reference to related 1,3-dithoxa- and 1,3-dithia- five-membered rings with As, P, S or C at the 2-position.     

Enzymatic Incorporation of a Coumarin–Guanine Base Pair

Previous expansions beyond nature's preferred base‐pairing interactions have utilized either nonpolar shape‐fitting interactions or classical hydrogen bonding. Reported here is a hybrid of these systems. By replacing a single N?H with C?H at a Watson–Crick interface, the design space for new drug candidates and fluorescent nucleobase analogues is dramatically expanded, as demonstrated here by the new, highly fluorescent deoxycytidine mimic 3‐glycosyl‐5‐fluoro‐7‐methoxy‐coumarin‐2′‐deoxyribose (d C ^C ). dGTP is selectively incorporated across from a template d C ^C during enzymatic DNA synthesis. Likewise, d C ^C is selectively incorporated across from a template guanine when d C ^C is provided as the triphosphate d C ^C TP . DNA polymerase I (Klenow fragment) exhibited about a 10‐fold higher affinity for d C ^C TP than dCTP, allowing selective incorporation of d C ^C in direct competition experiments. These results demonstrate that a single C?H can replace N?H at a Watson–Crick‐type interface with preservation of functional selectivity and enhanced activity.     

Functional carbo‐Butadienes: Nonaromatic Conjugation Effects through a 14‐Carbon, 24‐π‐Electron Backbone

A systematic study of carbo‐butadiene motifs not embedded in an aromatic carbo‐benzene ring is described. Dibutatrienylacetylene (DBA) targets R¹?C(R)?C?C?C(Ph)?C≡C?C(Ph)?C?C?C(R)?R² are devised, in which R is C≡CSiiPr₃ and R¹ and R² are R, H, or 4‐X‐C₆H₄, with the latter including three known representatives (X: H, NMe₂, or NH₂). The synthesis method is based on the SnCl₂‐mediated reduction of pentaynediols prepared by early or late divergent strategies; the latter allows access to a OMe–NO₂ push–pull diaryl‐DBA. If R¹ and R² are H, an over‐reduced dialkynylbutatriene (DAB) with two allenyl caps was isolated instead of the unsubstituted DBA. If R¹=R²=R, the tetraalkynyl‐DBA target was obtained, along with an over‐reduced DBA product with a 12‐membered 1,2‐alkylidene‐1H₂,2H₂‐carbo‐cyclobutadiene ring. X‐ray crystallography shows that all of the acyclic DBAs adopt a planar trans–transoid–trans configuration. The maximum UV/Vis absorption wavelength is found to vary consistently with the overall π‐conjugation extent and, more intriguingly, with the π‐donor character of the aryl X substituents, which varies consistently with the first (reversible) reduction potential and first (irreversible) oxidation peak, as determined by voltammetry.     

Stereospecificity of 1H, 13C and 15N shielding constants in the isomers of methylglyoxal bisdimethylhydrazone: problem with configurational assignment based on 1H chemical shifts

In the ¹³C NMR spectra of methylglyoxal bisdimethylhydrazone, the ¹³C‐5 signal is shifted to higher frequencies, while the ¹³C‐6 signal is shifted to lower frequencies on going from the EE to ZE isomer following the trend found previously. Surprisingly, the ¹H‐6 chemical shift and ¹J(C‐6,H‐6) coupling constant are noticeably larger in the ZE isomer than in the EE isomer, although the configuration around the –CH═N– bond does not change. This paradox can be rationalized by the C–H?N intramolecular hydrogen bond in the ZE isomer, which is found from the quantum‐chemical calculations including Bader's quantum theory of atoms in molecules analysis. This hydrogen bond results in the increase of δ(¹H‐6) and ¹J(C‐6,H‐6) parameters. The effect of the C–H?N hydrogen bond on the ¹H shielding and one‐bond ¹³C–¹H coupling complicates the configurational assignment of the considered compound because of these spectral parameters. The ¹H, ¹³C and ¹⁵N chemical shifts of the 2‐ and 8‐(CH₃)₂N groups attached to the –C(CH₃)═N– and –CH═N– moieties, respectively, reveal pronounced difference. The ab initio calculations show that the 8‐(CH₃)₂N group conjugate effectively with the π‐framework, and the 2‐(CH₃)₂N group twisted out from the plane of the backbone and loses conjugation. As a result, the degree of charge transfer from the N‐2– and N‐8– nitrogen lone pairs to the π‐framework varies, which affects the ¹H, ¹³C and ¹⁵N shieldings. Copyright © 2012 John Wiley & Sons, Ltd.     

Nickel-Catalyzed C−I-Selective C(sp2)−C(sp3) Cross-Electrophile Coupling of Bromo(iodo)arenes with Alkyl Bromides

Despite several methodologies established for C(sp²)−I selective C(sp²)−C(sp³) bond formations, achieving arene-flanked quaternary carbons by cross-coupling of tertiary alkyl precursors with bromo(iodo)arenes in a C(sp²)−I selective manner is rare. Here we report a general Ni-catalyzed C(sp²)−I selective cross-electrophile coupling (XEC) reaction, in which, beyond 3° alkyl bromides (for constructing arene-flanked quaternary carbons), 2° and 1° alkyl bromides are also demonstrated to be viable coupling partners. Moreover, this mild XEC displays excellent C(sp²)−I selectivity and functional group compatibility. The practicality of this XEC is demonstrated in simplifying the routes to several medicinally relevant and synthetically challenging compounds. Extensive experiments show that the terpyridine-ligated Ni^I halide can exclusively activate alkyl bromides, forming a Ni^I−alkyl complex through a Zn reduction. Attendant density functional theory (DFT) calculations reveal two different pathways for the oxidative addition of the Ni^I−alkyl complex to the C(sp²)−I bond of bromo(iodo)arenes, explaining both the high C(sp²)−I selectivity and generality of our XEC.