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1. The electronic structure of a β-diketiminate manganese hydride dimer

   https://doi.org/10.1039/D0DT02842H  

   Oh, Changjin ; Siewe, Joëlle ; Nguyen, Thao T. ; Kawamura, Airi ; Flores, Marco ; Groy, Thomas L. ; Anderson, John S. ; Trovitch, Ryan J. ; Baik, Mu-Hyun ( October 2020 , Dalton Transactions)

   null (Ed.)

   The electronic structure of a dimeric manganese hydride catalyst supported by β-diketiminate ligands, [( 2,6-iPr2Ph BDI)Mn(μ-H)] 2 , was investigated with density functional theory. A triple bond between the manganese centres was anticipated from simple electron-counting rules; however, calculations revealed Mn–Mn Mayer bond orders of 0.21 and 0.27 for the ferromagnetically-coupled and antiferromagnetically-coupled extremes, respectively. In accordance with experimentally determined Heisenberg exchange coupling constants of −15 ± 0.1 cm −1 (SQUID) and −10.2 ± 0.7 cm −1 (EPR), the calculated J 0 value of −10.9 cm −1 confirmed that the ground state involves antiferromagnetic coupling between high spin Mn( ii )-d 5 centres. The effect of steric bulk on the bond order was examined via a model study with the least sterically-demanding version of the β-diketiminate ligand and was found to be negligible. Mixing between metal- and β-diketiminate-based orbitals was found to be responsible for the absence of a metal–metal multiple bond. The bridging hydrides give rise to a relatively close positioning of the metal centres, while bridging atoms possessing 2p orbitals result in longer Mn–Mn distances and more stable dimers. The synthesis and characterization of the bridging hydroxide variant, [( 2,6-iPr2Ph BDI)Mn(μ-OH)] 2 , provides experimental support for these assessments. 

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2. Dimetalloylene (M‐E‐M) Complexes of Heavier Main Group Elements Ge, Sn, Pb, Bi via Cleavage of E‐X Bonds (X=N(SiMe 3 ) 2 , O t Bu) with an Iridium Hydride

   https://doi.org/10.1002/chem.202301863  

   Saint‐Denis, Tyler G. ; Zhang, Bowen ; Settineri, Nicholas S. ; Handford, Rex C. ; Hall, Michael B. ; Tilley, T. Don ( July 2023 , Chemistry – A European Journal)

   Reactions of the Ir^Vhydride [^MeBDI^Dipp]IrH₄{BDI=(Dipp)NC(Me)CH(Me)CN(Dipp); Dipp=2,6‐iPr₂C₆H₃} with E[N(SiMe₃)₂]₂(E=Sn, Pb) afforded the unusual dimeric dimetallotetrylenes ([^MeBDI^Dipp]IrH)₂(μ₂‐E)₂in good yields. Moreover, ([^MeBDI^Dipp]IrH)₂(μ₂‐Ge)₂was formed in situ from thermal decomposition of [^MeBDI^Dipp]Ir(H)₂Ge[N(SiMe₃)₂]₂. These reactions are accompanied by liberation of HN(SiMe₃)₂and H₂through the apparent cleavage of an E−N(SiMe₃)₂bond by Ir−H. In a reversal of this process, ([^MeBDI^Dipp]IrH)₂(μ₂‐E)₂reacted with excess H₂to regenerate [^MeBDI^Dipp]IrH₄. Varying the concentrations of reactants led to formation of the trimeric ([^MeBDI^Dipp]IrH₂)₃(μ₂‐E)₃. The further scope of this synthetic route was investigated with group 15 amides, and ([^MeBDI^Dipp]IrH)₂(μ₂‐Bi)₂was prepared by the reaction of [^MeBDI^Dipp]IrH₄with Bi(NMe₂)₃or Bi(OtBu)₃to afford the first example of a “naked” two‐coordinate Bi atom bound exclusively to transition metals. A viable mechanism that accounts for the formation of these products is proposed. Computational investigations of the Ir₂E₂(E=Sn, Pb) compounds characterized them as open‐shell singlets with confined nonbonding lone pairs at the E centers. In contrast, Ir₂Bi₂is characterized as having a closed‐shell singlet ground state.

    

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3. σ or π? Bonding interactions in a series of rhenium metallotetrylenes

   https://doi.org/10.1039/D1DT00129A  

   Ouellette, Erik T. ; Carpentier, Ambre ; Joseph Brackbill, I. ; Lohrey, Trevor D. ; Douair, Iskander ; Maron, Laurent ; Bergman, Robert G. ; Arnold, John ( February 2021 , Dalton Transactions)

   null (Ed.)

   Salt metathesis reactions between a low-valent rhenium( i ) complex, Na[Re(η 5 -Cp)(BDI)] (BDI = N , N ′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate), and a series of amidinate-supported tetrylenes of the form ECl[PhC(N t Bu) 2 ] (E = Si, Ge, Sn) led to rhenium metallotetrylenes Re(E[PhC(N t Bu) 2 ])(η 5 -Cp)(BDI) (E = Si ( 1a ), Ge ( 2 ), Sn ( 4 )) with varying extents of Re–E multiple bonding. Whereas the rhenium–stannylene 4 adopts a σ-metallotetrylene arrangement featuring a Re–E single bond, the rhenium–silylene ( 1a ) and –germylene ( 2 ) both engage in π-interactions to form short Re–E multiple bonds. Temperature was found to play a crucial role in reactions between Na[Re(η 5 -Cp)(BDI)] and SiCl[PhC(N t Bu) 2 ], as manipulation of reaction conditions led to isolation of an unusual rhenium–silane, (BDI)Re(μ-η 5 :η 1 -C 5 H 4 )(SiH[PhC(N t Bu) 2 ]) ( 1b ) and a dinitrogen bridged rhenium–silylene, (η 5 -Cp)(BDI)Re(μ-N 2 )Si[PhC(N t Bu) 2 ] ( 1c ), in addition to 1a . Finally, the reaction of Na[Re(η 5 -Cp)(BDI)] with GeCl 2 ·dioxane led to a rare μ 2 -tetrelido complex, μ 2 -Ge[Re(η 5 -Cp)(BDI)] 2 ( 3 ). Bonding interactions within these complexes are discussed through the lens of various spectroscopic, structural, and computational investigations. 

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4. 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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5. Comparison of two Mn IV Mn IV -bis-μ-oxo complexes {[Mn IV (N 4 (6-Me-DPEN))] 2 (μ-O) 2 } 2+ and {[Mn IV (N 4 (6-Me-DPPN))] 2 (μ-O) 2 } 2+

   https://doi.org/10.1107/S2056989020004557  

   Coggins, Michael K. ; Downing, Alexandra N. ; Kaminsky, Werner ; Kovacs, Julie A. ( July 2020 , Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   The addition of tert -butyl hydroperoxide ( t BuOOH) to two structurally related Mn II complexes containing N,N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine (6-Me-DPEN) and N,N -bis(6-methyl-2-pyridylmethyl)propane-1,2-diamine (6-Me-DPPN) results in the formation of high-valent bis-oxo complexes, namely di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)ethane-1,2-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) dihydrate, [Mn(C 16 H 22 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2H 2 O or {[Mn IV (N 4 (6-Me-DPEN))] 2 ( μ -O) 2 }(2BPh 4 )(2H 2 O) ( 1 ) and di-μ-oxido-bis{[ N , N -bis(6-methyl-2-pyridylmethyl)propane-1,3-diamine]manganese(II)}( Mn — Mn ) bis(tetraphenylborate) diethyl ether disolvate, [Mn(C 17 H 24 N 4 ) 2 O 2 ](C 24 H 20 B) 2 ·2C 4 H 10 O or {[Mn IV (N 4 (6-MeDPPN))] 2 ( μ -O) 2 }(2BPh 4 )(2Et 2 O) ( 2 ). Complexes 1 and 2 both contain the `diamond core' motif found previously in a number of iron, copper, and manganese high-valent bis-oxo compounds. The flexibility in the propyl linker in the ligand scaffold of 2 , as compared to that of the ethyl linker in 1 , results in more elongated Mn—N bonds, as one would expect. The Mn—Mn distances and Mn—O bond lengths support an Mn IV oxidation state assignment for the Mn ions in both 1 and 2 . The angles around the Mn centers are consistent with the local pseudo-octahedral geometry. 

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