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1. Magnetic anisotropy and slow magnetic relaxation processes of cobalt( ii )-pseudohalide complexes

   https://doi.org/10.1039/C9DT00644C  

   Cui, Hui-Hui; Zhang, Yi-Quan; Chen, Xue-Tai; Wang, Zhenxing; Xue, Zi-Ling (January 2019, Dalton Transactions)

   Three mononuclear six-coordinate Co( ii )-pseudohalide complexes [Co(L)X 2 ] with two N-donor pseudohalido coligands occupying the cis -positions (X = NCS − ( 1 ), NCSe − ( 2 ) or N(CN) 2 − ( 3 )), and a five-coordinate complex [Co(L)(NCO)][B(C 6 H 5 ) 4 ] ( 4 ) [L = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (12-TMC)] have been prepared and structurally characterized. Easy-plane magnetic anisotropy for 1–3 and easy-axis anisotropy for 4 were revealed via the analyses of the direct-current magnetic data, high-frequency and -field EPR (HFEPR) spectra and ab initio theoretical calculations. They display slow magnetic relaxations under an external applied dc field. Typically, two slow relaxation processes were found in 1 and 2 while only one relaxation process occurs in 3 and 4 . The Raman-like mechanism is found to be dominant in the studied temperature range in 1 . For 2–4 , the Raman process is dominant in the low temperature region, while the Orbach mechanism dominates in the high temperature range. 

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2. Magnetic anisotropy in square pyramidal cobalt( ii ) complexes supported by a tetraazo macrocyclic ligand

   https://doi.org/10.1039/D0DT01954B  

   Cui, Hui-Hui; Ding, Man-Man; Zhang, Xiu-Du; Lv, Wei; Zhang, Yi-Quan; Chen, Xue-Tai; Wang, Zhenxing; Ouyang, Zhong-Wen; Xue, Zi-Ling (November 2020, Dalton Transactions)

   null (Ed.)

   Two five-coordinate mononuclear Co( ii ) complexes [Co(12-TMC)X][B(C 6 H 5 ) 4 ] (L = 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (12-TMC), X = Cl − ( 1 ), Br − ( 2 )) have been studied by X-ray single crystallography, magnetic measurements, high-frequency and -field EPR (HF-EPR) spectroscopy and theoretical calculations. Both complexes have a distorted square pyramidal geometry with the Co( ii ) ion lying above the basal plane constrained by the rigid tetradentate macrocyclic ligand. In contrast to the reported five-coordinate Co( ii ) complex [Co(12-TMC)(NCO)][B(C 6 H 5 ) 4 ] ( 3 ) exhibiting easy-axis anisotropy, an easy-plane magnetic anisotropy was found for 1 and 2 via the analyses of the direct-current magnetic data and HF-EPR spectroscopy. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements demonstrated that complexes 1 and 2 show slow magnetic relaxation at an applied dc field. Ab initio calculations were performed to reveal the impact of the terminal ligands on the nature of the magnetic anisotropies of this series of five-coordinate Co( ii ) complexes. 

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3. Visible light induced formation of a tungsten hydride complex

   https://doi.org/10.1039/d2dt03675d  

   Isaacs, Diane P.; Gruninger, Cole T.; Huang, Tao; Jordan, Aldo M.; Nicholas, Genique; Chen, Chun-Hsing; ter Horst, Marc A.; Dempsey, Jillian L. (March 2023, Dalton Transactions)

   When irradiated with blue light in the presence of a Lewis base (L), [CpW(CO) 3 ] 2 undergoes metal–metal bond cleavage followed by a disproportionation reaction to form [CpW(CO) 3 L] + and [CpW(CO) 3 ] − . Here, we show that in the presence of pyridinium tetrafluoroborate, [CpW(CO) 3 ] − reacts further to form a metal hydride complex CpW(CO) 3 H. The rection was monitored through in situ photo 1 H NMR spectroscopy experiments and the mechanism of light-driven hydride formation was investigated by determining quantum yields of formation. Quantum yields of formation of CpW(CO) 3 H correlate with I −1/2 (I = photon flux on our sample tube), indicating that the net disproportionation of [CpW(CO) 3 ] 2 to form the hydride precursor [CpW(CO) 3 ] − occurs primarily through a radical chain mechanism. 

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4. Accessing Reactive Metal Hydrides through Designed Heterometallic Bridges

   https://doi.org/10.1055/a-2264-9040  

   Gonzalez, Fernando; De_Leon, Edgardo; Shoshani, Manar M (February 2024, Synlett)

   Abstract A methodology to access reactive hydride moieties is highly desirable, yet limited. Multimetallic hydride fragments are notable for their heightened reactivity and catalysis, but deliberate access to these species is lacking. In this highlight, we discuss recent developments by our group in the design of a new heterometallic complex that invokes an architecture designed to provide modular access to reactive hydride moieties by leveraging metal hydrides in combination with pendent donors to a model heterotrimetallic Ni–(Al–H)2 complex. An amplification of insertion-based reactivity has been examined in the hydrofunctionalization of quinolines, and our complex substantially outperformed the parent aluminum hydride LAlH (L = ligand). A potential rationale for the dramatically increased reactivity, and a further examination of these motifs and methodology in catalysis are also discussed. 1. Introduction 2. Heterometallic Hydride Design and Characterization 3. Amplification in Catalysis 4. Summary and Outlook 

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5. Electrochemical C–H bond activation via cationic iridium hydride pincer complexes

   https://doi.org/10.1039/C9SC03076J  

   Lindley, Brian M.; Walden, Andrew G.; Brasacchio, Ann Marie; Casuras, Andrea; Lease, Nicholas; Chen, Chun-Hsing; Goldman, Alan S.; Miller, Alexander J. (January 2019, Chemical Science)

   A C–H bond activation strategy based on electrochemical activation of a metal hydride is introduced. Electrochemical oxidation of ( tBu4 PCP)IrH 4 ( tBu4 PCP is [1,3-( t Bu 2 PCH 2 )-C 6 H 3 ] − ) in the presence of pyridine derivatives generates cationic Ir hydride complexes of the type [( tBu4 PCP)IrH(L)] + (where L = pyridine, 2,6-lutidine, or 2-phenylpyridine). Facile deprotonation of [( tBu4 PCP)IrH(2,6-lutidine)] + with the phosphazene base tert -butylimino-tris(pyrrolidino)phosphorane, t BuP 1 (pyrr), results in selective C–H activation of 1,2-difluorobenzene (1,2-DFB) solvent to generate ( tBu4 PCP)Ir(H)(2,3-C 6 F 2 H 3 ). The overall electrochemical C–H activation reaction proceeds at room temperature without need for chemical activation by a sacrificial alkene hydrogen acceptor. This rare example of undirected electrochemical C–H activation holds promise for the development of future catalytic processes. 

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