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1. Bis(catecholato-κ ² O , O ′)bis(dimethyl sulfoxide-κ O )titanium(IV)

   https://doi.org/10.1107/S2056989022002638  

   Hewage, Nisansala; Mastriano, Carolyn; Brückner, Christian; Zeller, Matthias (April 2022, Acta Crystallographica Section E Crystallographic Communications)

   Bis(benzene-1,2-diolato-κ 2 O , O ′)bis(dimethyl sulfoxide-κ O )titanium(IV), [Ti(C 6 H 4 O 2 ) 2 (C 2 H 6 OS) 2 ], crystallizes with two crystallographically independent molecules in the space group P 2 1 / c emulating orthorhombic Pbca symmetry (β = 90.0445 (9)°]. The two molecules are related by pseudo-glide symmetry, broken by modulation of each one catecholate and dimethyl sulfoxide (DMSO) ligand. Twinning by pseudomerohedry was observed [twin ratio 0.5499 (7):0.4401 (7)]. Complex 3 was obtained by heating of diprotonated titanium tris-catecholate precursor 2 H in DMSO, by formal displacement of a catechol molecule by two DMSO molecules. Complex 3 is just the second heteroleptic, mono-nuclear, neutral bis-catecholate complex with TiO 6 metal coordination, the only other one being its bis-DMF analogue 6 . The two molecules of 3 exhibit a distorted octahedral geometry. The geometry and distortions from ideal symmetry of 3 are discussed and compared to 6 and to cationic tris-catecholate titanium complexes. 

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2. Mono- and bimetallic pentacoordinate silicon complexes of a chelating bis(catecholimine) ligand

   https://doi.org/10.1039/C9DT02475A  

   Do, Thomas H.; Brown, Seth N. (July 2019, Dalton Transactions)

   Schiff base condensation of 4,5-diamino-9,9-dimethylxanthene with 4,6-di- tert -butylcatechol-3-carboxaldehyde affords the bis(catecholimine) ligand XbicH 4 , which can bind metals in both a square bis(catecholate) upper pocket and a pentagonal N 2 O 3 lower pocket. Metalation with PhSiCl 3 results in [(XbicH 2 )SiPh][HCl 2 ], where the silicon adopts a five-coordinate, square pyramidal geometry in the upper pocket and the lower pocket binds to two protons on the imine nitrogens. Deprotonation of the imines with LiO t Bu, NaN[SiMe 3 ] 2 , or AgOAc results in binding of the univalent metal ion in the lower pocket, where it adopts an unusual pentagonal monopyramidal geometry in the solid state. The complexes show irreversible electrochemistry, with oxidations taking place at relatively high potentials. 

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3. Lewis base-complexed magnesium dithiolenes

   https://doi.org/10.1039/C9CC03427G  

   Wang, Yuzhong; Maxi, Nirva A.; Xie, Yaoming; Wei, Pingrong; Schaefer, Henry F.; Robinson, Gregory H. (July 2019, Chemical Communications)

   The first magnesium-based dithiolene, 2 , was prepared by reaction of the lithium dithiolene radical, 1˙ , with 2-mesitylmagnesium bromide. Reaction of 2 with N-heterocyclic carbenes (in toluene) gave a carbene-stabilized magnesium monodithiolene complex, 3 . Complex 3 , in turn, is readily converted to a THF-solvated magnesium bis-dithiolene dianion, 4 , via partial hydrolysis in polar solvents ( i.e. , THF/CH 3 CN). Compounds 2 , 3 and 4 have been spectroscopically and structurally characterized and probed by DFT computations. 

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4. Long-lived photoluminescence from an eight-coordinate zirconium( iv ) complex with four 2-(2′-pyridyl)pyrrolide ligands

   https://doi.org/10.1039/D2CC04912K  

   Leary, Dylan C.; Martinez, Jordan C.; Akhmedov, Novruz G.; Petersen, Jeffrey L.; Milsmann, Carsten (October 2022, Chemical Communications)

   The photoluminescent eight-coordinate zirconium complex Zr( H PMP H ) 4 supported by four monoanionic 2-(2′-pyridine)pyrrolide ligands was synthesized. This molecule shows dual emission via fluorescence and phosphorescence with an overall quantum efficiency of 4% at room temperature in solution. The phosphorescence lifetime is dependent on concentration, indicating excimer formation at higher concentrations, and reaches almost 800 μs at high dilution. 

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5. 1,2-Addition and cycloaddition reactions of niobium bis(imido) and oxo imido complexes

   https://doi.org/10.1039/D0SC03489D  

   Fostvedt, Jade I.; Grant, Lauren N.; Kriegel, Benjamin M.; Obenhuber, Andreas H.; Lohrey, Trevor D.; Bergman, Robert G.; Arnold, John (November 2020, Chemical Science)

   null (Ed.)

   The bis(imido) complexes (BDI)Nb(N t Bu) 2 and (BDI)Nb(N t Bu)(NAr) (BDI = N , N ′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate; Ar = 2,6-diisopropylphenyl) were shown to engage in 1,2-addition and [2 + 2] cycloaddition reactions with a wide variety of substrates. Reaction of the bis(imido) complexes with dihydrogen, silanes, and boranes yielded hydrido-amido-imido complexes via 1,2-addition across Nb-imido π-bonds; some of these complexes were shown to further react via insertion of carbon dioxide to give formate-amido-imido products. Similarly, reaction of (BDI)Nb(N t Bu) 2 with tert -butylacetylene yielded an acetylide-amido-imido complex. In contrast to these results, many related mono(imido) Nb BDI complexes do not exhibit 1,2-addition reactivity, suggesting that π-loading plays an important role in activating the Nb–N π-bonds toward addition. The same bis(imido) complexes were also shown to engage in [2 + 2] cycloaddition reactions with oxygen- and sulfur-containing heteroallenes to give carbamate- and thiocarbamate-imido complexes: some of these complexes readily dimerized to give bis-μ-sulfido, bis-μ-iminodicarboxylate, and bis-μ-carbonate complexes. The mononuclear carbamate imido complex (BDI)Nb(NAr)(N( t Bu)CO 2 ) ( 12 ) could be induced to eject tert -butylisocyanate to generate a four-coordinate terminal oxo imido intermediate, which could be trapped as the five-coordinate pyridine or DMAP adduct. The DMAP adducted oxo imido complex (BDI)NbO(NAr)(DMAP) ( 16 ) was shown to engage in 1,2-addition of silanes across the Nb-oxo π-bond; this represents a new reaction pathway in group 5 chemistry. 

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