Two new Cu(II)-based structures containing alternating chains and their magnetic properties are reported. Reaction of CuBr₂ and 2-aminopyridine in methanol yielded [(2-aminopyridine)μ-Br(μ-OMe)Cu]_n (1) which crystallizes in the triclinic space group P-1. Cu(II) ions are linked alternately by bibromide and bi-methoxide bridges into chains parallel to the a-axis. Reaction of copper perchlorate hexahydrate with 4-pyridone and pyrazine in methanol yielded [(μ-pz)(μ-κ-O-4-pyridone)₂(μ-OH)₂Cu₂]_n(ClO₄)_2n (2). The Cu(II) ions are alternately linked by bihydroxide and bi-κ-O-4-pyridone species parallel to the a-axis. Those chains are further linked by bridging pyrazine molecules ∼ parallel to the b-axis, with the pyrazine molecules and bi-hydroxide bridges alternating. The net effect is a rectangular lattice where each side of the rectangle is an alternating chain. The layers are separated by perchlorate ions. Both compounds are diamagnetic at room temperature.

The compounds catena-[diaquadichloridocopper(II)] bis(4-bromo-2-pyridone) (1) and catena-[bis(5-bromo-2-pyridone)dichloridocopper(II)] (2) have been prepared and characterized crystallographically. Both show bichloride bridged chains of Cu(II) ions with coordinated water molecules in the axial sites for 1 and coordinated 5-bromo-2-pyridone molecules in the axial sites for 2. 1 incorporates two 4-bromo-2-pyridone molecules co-crystallized in the lattice. Variable temperature magnetic susceptibility measurements for 1 indicate the presence of weak antiferromagnetic interactions [J/k_B = −7.06(5) K] similar to copper(II) chloride dihydrate, but without that compound’s significant inter-chain interactions and Néel transition.

Reaction of 2-amino-5-iodo­pyridine (5IAP) with concentrated HBr at room temperature yielded 2-amino-5-iodo­pyridinium bromide, C₅H₆IN₂⁺·Br⁻ or (5IAPH)Br. The complex formed pale-yellow crystals, which exhibit significant hydrogen bonding between the amino and pyridinium N—H donors and bromide ion acceptors. Halogen bonding is also observed. Similarly, reaction of 5IAP with cobalt(II) chloride in mixed HCl/HBr in 1-propanol yielded 2-amino-5-iodo­pyridinium (2-amino-5-iodo­pyridine-κN¹)bromido/chlorido­(0.51/2.48)cobalt(II), (C₅H₆IN₂)[CoBr_0.51Cl_2.48(C₅H₅IN₂)] or (5-IAPH)[(5IAP)CoCl_2.48Br_0.51], as blue block-shaped crystals. Two of the three halide positions exhibit mixed occupancy [Cl/Br = 0.797 (5):0.203 (5) and 0.689 (6):0.311 (6)], while the third position is occupied solely by a chloride ion. Extensive hydrogen and halogen bonding is observed.

Four new copper(II) compounds with an inorganic, adamantane-like core have been prepared and structurally characterized: [(2-aminopyridine)₄(μ₂-Br)₆Cu₄(μ₄-O)].(2-aminopyridinium) bromide monohydrate (1), the open cage structure (2-aminopyridinium) [(2-aminopyridine)₄(μ₂-Cl)₅(Cl)₂Cu₄(μ₄-O)] (2), bis(2-amino-5-methylpyridinium) [(2-amino-5-methylpyridine)₂(μ₂-Cl)₆(Cl)₂Cu₄(μ₄-O)] (3) and the co-crystal [(2-amino-5-fluoropyridine)₄(μ-Cl)₆Cu₄(μ₄-O)]₂ [(2-amino-5-fluoropyridine)₄Cu₂Cl₄] (4). All four include additional components in the lattice ranging from a non-coordinated ancillary ligand (1) to a co-crystallization with a distinct coordination complex (4). The compounds crystallize as: 1, triclinic, P-1; 2, monoclinic, P2₁/c; 3, monoclinic, P2₁/c; 4, triclinic, P-1. Analysis of the geometric parameters within the adamantoid cores of the compounds indicates significant structural resilience as parameters are little changed by the presence of additional components in the lattice. Breaking of the central core by coordination of an additional chloride ion in 2 significantly affects the geometry about those two Cu(II) ions but has little effect on other parts of the core.

Methods are lacking that can prepare deuterium-enriched building blocks, in the full range of deuterium substitution patterns at the isotopic purity levels demanded by pharmaceutical use. To that end, this work explores the regio- and stereoselective deuteration of tetrahydropyridine (THP), which is an attractive target for study due to the wide prevalence of piperidines in drugs. A series of d₀–d₈ tetrahydropyridine isotopomers were synthesized by the stepwise treatment of a tungsten-complexed pyridinium salt with H⁻/D⁻ and H⁺/D⁺. The resulting decomplexed THP isotopomers and isotopologues were analyzed via molecular rotational resonance (MRR) spectroscopy, a highly sensitive technique that distinguishes isotopomers and isotopologues by their unique moments of inertia. In order to demonstrate the medicinal relevance of this approach, eight unique deuterated isotopologues of erythro-methylphenidate were also prepared.

Five new copper(II) complexes of substituted quinoxaline ligands have been prepared and characterized via single crystal X-ray diffraction, including [Cu(5-Mequinox)₂(NO₃)₂] (2), [Cu(5-Mequinox)(NO₃)(H₂O)(μ-1,3-NO₃)]_n (3), the chloride salt (5-MequinoxH)₂[Cu₃Cl₈] (4), the complex [Cu(6-Mequinox)₂(NO₃)₂] (5) and [(2-carboxylato-3-methylquinox)(2-hydroxymethyl-3-methylquinox)nitratocopper(II)]. CH₃CN (6) [quinox = quinoxaline; 5-Mequinox = 5-methylquinoxaline; 6-Mequinox = 6-methylquinoxaline]. None of the complexes produced diazine bridged chain structures (as seen in [(quinox)Cu(NO₃)₂]_n (1)), although 3 forms chains via a bridging nitrate ion. Crystal packing is controlled primarily through hydrogen bonding and π-stacking of nitrate ions. The temperature dependent magnetic susceptibility data of the parent compound [(quinox)Cu(NO₃)₂]_n are also reported and discussed.

Main-group element-mediated C–H activation remains experimentally challenging, and the development of clear concepts and design principles have been limited by the increased reactivity of relevant complexes, especially for the heavier elements. Herein, we report that the stibenium ion [(pyCDC)Sb][NTf2]3 (1) (pyCDC = bis-pyridyl carbodicarbene; NTf2 = bis(trifluoromethanesulfonyl)imide) reacts with acetonitrile in the presence of the base 2,6-di-tert­-butylpyridine to enable C(sp3)–H bond breaking to generate the stiba-methylene nitrile complex [(pyCDC)Sb(CH2CN)][NTf2]2 (2). Kinetic analyses were performed to elucidate the rate dependence for all the substrates involved in the reaction. Computational studies suggest that C–H activation proceeds via a mechanism in which acetonitrile first coordinates to the Sb center through the nitrogen atom in a κ1 fashion, thereby weakening the C–H bond which can then be deprotonated by base in solution. Further, we show that 1 reacts with terminal alkynes in the presence of 2,6-di-tert­-butylpyridine to enable C(sp)–H bond breaking to form stiba-alkynyl adducts of the type [(pyCDC)Sb(CCR)][NTf2]2 (3a-f). Compound 1 shows excellent specificity for the activation of the terminal C(sp)–H bond even across alkynes with diverse functionality. The resulting stiba-methylene nitrile and stiba-alkynyl adducts react with elemental iodine (I2) to produce iodoacetonitrile and iodoalkynes, while regenerating an Sb trication.