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1. Formal Nickelate(−I) Complexes Supported by Group 13 Ions

   https://doi.org/10.1002/anie.201803356  

   Vollmer, Matthew V. ; Xie, Jing ; Cammarota, Ryan C. ; Young, Jr., Victor G. ; Bill, Eckhard ; Gagliardi, Laura ; Lu, Connie C. ( May 2018 , Angewandte Chemie International Edition)

   Formal nickelate(−I) complexes bearing Group 13 metalloligands (M=Al and Ga) were isolated. These 17 e⁻complexes were synthesized by one‐electron reduction of the corresponding Ni⁰→M^IIIprecursors, and were investigated by single‐crystal X‐ray diffraction, EPR spectroscopy, and quantum chemical calculations. Collectively, the experimental and computational data support: 1) the strengthening of the Ni−M bond upon one‐electron reduction, and 2) the delocalization of the unpaired spin across the Ni and M atoms. An intriguing electronic configuration is revealed where three valence electrons occupy two σ‐type bonding interactions: Ni(3d)²→M and σ‐(Ni−M)¹. The latter is an unusual Ni−M σ‐bonding molecular orbital that comprises primarily the Ni 4p_zand M np_z/ns atomic orbitals.

    

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2. Formal Nickelate(−I) Complexes Supported by Group 13 Ions

   https://doi.org/10.1002/ange.201803356  

   Vollmer, Matthew V. ; Xie, Jing ; Cammarota, Ryan C. ; Young, Jr., Victor G. ; Bill, Eckhard ; Gagliardi, Laura ; Lu, Connie C. ( May 2018 , Angewandte Chemie)

   Formal nickelate(−I) complexes bearing Group 13 metalloligands (M=Al and Ga) were isolated. These 17 e⁻complexes were synthesized by one‐electron reduction of the corresponding Ni⁰→M^IIIprecursors, and were investigated by single‐crystal X‐ray diffraction, EPR spectroscopy, and quantum chemical calculations. Collectively, the experimental and computational data support: 1) the strengthening of the Ni−M bond upon one‐electron reduction, and 2) the delocalization of the unpaired spin across the Ni and M atoms. An intriguing electronic configuration is revealed where three valence electrons occupy two σ‐type bonding interactions: Ni(3d)²→M and σ‐(Ni−M)¹. The latter is an unusual Ni−M σ‐bonding molecular orbital that comprises primarily the Ni 4p_zand M np_z/ns atomic orbitals.

    

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3. Thermodynamic and kinetic studies of H 2 and N 2 binding to bimetallic nickel-group 13 complexes and neutron structure of a Ni(η 2 -H 2 ) adduct

   https://doi.org/10.1039/C9SC02018G  

   Cammarota, Ryan C. ; Xie, Jing ; Burgess, Samantha A. ; Vollmer, Matthew V. ; Vogiatzis, Konstantinos D. ; Ye, Jingyun ; Linehan, John C. ; Appel, Aaron M. ; Hoffmann, Christina ; Wang, Xiaoping ; et al ( July 2019 , Chemical Science)

   Understanding H 2 binding and activation is important in the context of designing transition metal catalysts for many processes, including hydrogenation and the interconversion of H 2 with protons and electrons. This work reports the first thermodynamic and kinetic H 2 binding studies for an isostructural series of first-row metal complexes: NiML, where M = Al ( 1 ), Ga ( 2 ), and In ( 3 ), and L = [N( o -(NCH 2 P i Pr 2 )C 6 H 4 ) 3 ] 3− . Thermodynamic free energies (Δ G °) and free energies of activation (Δ G ‡ ) for binding equilibria were obtained via variable-temperature 31 P NMR studies and lineshape analysis. The supporting metal exerts a large influence on the thermodynamic favorability of both H 2 and N 2 binding to Ni, with Δ G ° values for H 2 binding found to span nearly the entire range of previous reports. The non-classical H 2 adduct, (η 2 -H 2 )NiInL ( 3 -H 2 ), was structurally characterized by single-crystal neutron diffraction—the first such study for a Ni(η 2 -H 2 ) complex or any d 10 M(η 2 -H 2 ) complex. UV-Vis studies and TD-DFT calculations identified specific electronic structure perturbations of the supporting metal which poise NiML complexes for small-molecule binding. ETS-NOCV calculations indicate that H 2 binding primarily occurs via H–H σ-donation to the Ni 4p z -based LUMO, which is proposed to become energetically accessible as the Ni(0)→M( iii ) dative interaction increases for the larger M( iii ) ions. Linear free-energy relationships are discussed, with the activation barrier for H 2 binding (Δ G ‡ ) found to decrease proportionally for more thermodynamically favorable equilibria. The Δ G ° values for H 2 and N 2 binding to NiML complexes were also found to be more exergonic for the larger M( iii ) ions. 

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4. Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-dithione and isoindoline-1,3-dithione ligands

   https://doi.org/10.1107/S2056989020009676  

   Wheaton, Amelia M. ; Guzei, Ilia A. ; Berry, John F. ( August 2020 , Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-dithione (SNS), isoindoline-1,3-dithione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis[(acetonitrile-κ N )(6-sulfanylidenepiperidin-2-one-κ S )copper(I)], [Cu 2 I 2 (CH 3 CN) 2 (C 5 H 7 NOS) 2 ] ( I ), bis(acetonitrile-κ N )tetra-μ 3 -iodido-bis(6-sulfanylidenepiperidin-2-one-κ S )- tetrahedro -tetracopper(I), [Cu 4 I 4 (CH 3 CN) 4 (C 5 H 7 NOS) 4 ] ( II ), catena -poly[[(μ-6-sulfanylidenepiperidin-2-one-κ 2 O : S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NOS)] n ( III ), poly[[(piperidine-2,6-dithione-κ S )copper(I)]-μ 3 -iodido], [CuI(C 5 H 7 NS 2 )] n ( IV ), and poly[[(μ-isoindoline-1,3-dithione-κ 2 S : S )copper(I)]-μ 3 -iodido], [CuI(C 8 H 5 NS 2 )] n ( V ). Compounds I and II crystallize as discrete dimeric and tetrameric complexes, whereas III , IV , and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexagonal [Cu 3 I 3 ] structure that is not supported by bridging ligands. Structures I , II , and IV display weak to moderately strong Cu...Cu cuprophilic interactions [Cu...Cu internuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding interactions between the N—H of the ligand and the μ 2 and μ 3 -I − atoms. Structure III contains classical N–H...O interactions between the SNO ligands that connect the molecules in a three-dimensional framework. Complex V features π–π stacking interactions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV , there were three partially occupied solvent molecules of dichloromethane and one partially occupied molecule of acetonitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015). Acta Cryst . C 71 , 9–18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent molecules. The given chemical formula and other crystal data do not take into account the solvent molecules. 

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5. Ligand and Linkage Isomers of Bis(ethylthiocarbamato) Copper Complexes with Cyclic C 6 H 8 Backbone Substituents: Synthesis, Characterization, and Antiproliferation Activity

   https://doi.org/10.1002/ejic.202300447  

   Bajaj, Kritika ; Andres, Sarah A. ; Hofsommer, Dillon T. ; Chekwube Michael, Okolocha ; Mashuta, Mark S. ; Bates, Paula J. ; Buchanan, Robert M. ; Grapperhaus, Craig A. ( September 2023 , European Journal of Inorganic Chemistry)

   A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3‐methylpentyl (H₂L²) and cyclohexyl (H₂L³) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL^2a/3ahave two imino N and two S donors resulting in three five‐member chelate rings (555 isomers). The kinetic isomers CuL^2b/3bhave one imino and one hydrazino N donor and two S donors resulting in four‐, six‐, and five‐member rings (465 isomers). The 555 isomers have more accessible Cu^II/Ipotentials (E_1/2=−811/−768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E_1/2=−923/‐854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR‐90) using the MTT assay. CuL^2awas potent (^A549EC₅₀=0.080 μM) and selective (^IMR‐90EC₅₀/^A549EC₅₀=25) for A549. Its linkage isomer CuL^2bhad equivalent A549 activity, but lower selectivity (^IMR‐90EC₅₀/^A549EC₅₀=12.5). The isomers CuL^3aand CuL^3bwere less potent with^A549EC₅₀ values of 1.9 and 0.19 M and less selective with^IMR‐90EC₅₀/^A549EC₅₀ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity.

    

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