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1. The reaction of alkyl hydropersulfides (RSSH, R = CH ₃ and ^t Bu) with H ₂ S in the gas phase and in aqueous solution

   https://doi.org/10.1039/C8CP05503C  

   Zhang, Linxing; Zhang, Xinhao; Wu, Yun-Dong; Xie, Yaoming; Fukuto, Jon M.; Schaefer, Henry F. (January 2019, Physical Chemistry Chemical Physics)

   The RSSH + H 2 S → RSH + HSSH reaction has been suggested by numerous labs to be important in H 2 S-mediated biological processes. Seven different mechanisms for this reaction (R = CH 3 , as a model) have been studied using the DFT methods (M06-2X and ωB97X-D) with the Dunning aug-cc-pV(T+d)Z basis sets. The reaction of CH 3 SSH with gas phase H 2 S has a very high energy barrier (>45 kcal mol −1 ), consistent with the available experimental observations. A series of substitution reactions R 1 –S–S–H + − S–R 2 (R 1 = Me, t Bu, Ad, R 2 = H, S–Me, S– t Bu, S–Ad) have been studied. The regioselectivity is largely affected by the steric bulkiness of R 1 , but is much less sensitive to R 2 . Thus, when R 1 is Me, all − S–R 2 favorably attack the internal S atom, leading to R 1 –S–S–R 2 . While for R 1 = t Bu, Ad, all − S–R 2 significantly prefer to attack the external S atom to form − S–S–R 2 . These results are in good agreement with the experimental observations. 

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2. Effect of R-site element on crystalline phase and thermal stability of Fe substituted Mn mullite-type oxides: R ₂ (Mn _1−x Fe _x ) ₄ O _10−δ (R = Y, Sm or Bi; x = 0, 0.5, 1)

   https://doi.org/10.1039/C7RA09699B  

   Thampy, Sampreetha; Ashburn, Nickolas; Martin, Thomas J.; Li, Chenzhe; Zheng, Yongping; Chan, Julia Y.; Cho, Kyeongjae; Hsu, Julia W. (January 2018, RSC Advances)

   Combining experimental and theoretical studies, we investigate the role of R-site (R = Y, Sm, Bi) element on the phase formation and thermal stability of R 2 (Mn 1−x Fe x ) 4 O 10−δ ( x = 0, 0.5, 1) mullite-type oxides. Our results show a distinct R-site dependent phase behavior for mullite-type oxides as Fe is substituted for Mn: 100% mullite-type phase was formed in (Y, Sm, Bi) 2 Mn 4 O 10 ; 55% and 18% of (Y, Sm) 2 Mn 2 Fe 2 O 10−δ was found when R = Y and Sm, respectively, for equal Fe and Mn molar concentrations in the reactants, whereas Bi formed 54% O10- and 42% O9-mixed mullite-type phases. Furthermore, when the reactants contain 100% Fe, no mullite-type phase was formed for R = Y and Sm, but a sub-group transition to Bi 2 Fe 4 O 9 O9-phase was found for R = Bi. Thermogravimetric analysis and density functional theory (DFT) calculation results show a decreasing thermal stability in O10-type structure with increasing Fe incorporation; for example, the decomposition temperature is 1142 K for Bi 2 Mn 2 Fe 2 O 10−δ vs. 1217 K for Bi 2 Mn 4 O 10 . On the other hand, Bi 2 Fe 4 O 9 O9-type structure is found to be thermally stable up to 1227 K. These findings are explained by electronic structure calculations: (1) as Fe concentration increases, Jahn–Teller distortion results in mid band-gap empty states from unstable Fe 4+ occupied octahedra, which is responsible for the decrease in O10 structure stability; (2) the directional sp orbital hybridization unique to Bi effectively stabilizes the mullite-type structure as Fe replaces Mn. 

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3. 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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4. Synthesis, structures, and reactivity of isomers of [RuCp*(1,4-(Me ₂ N) ₂ C ₆ H ₄ )] ₂

   https://doi.org/10.1039/D1DT02155A  

   Longhi, Elena; Risko, Chad; Bacsa, John; Khrustalev, Victor; Rigin, Sergei; Moudgil, Karttikay; Timofeeva, Tatiana V.; Marder, Seth R.; Barlow, Stephen (September 2021, Dalton Transactions)

   [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 {Cp* = η 5 -pentamethylcyclopentadienyl, R = Me, Et} have previously been found to be moderately air stable, yet highly reducing, with estimated D + /0.5D 2 (where D 2 and D + represent the dimer and the corresponding monomeric cation, respectively) redox potentials of ca. −2.0 V vs. FeCp 2 +/0 . These properties have led to their use as n-dopants for organic semiconductors. Use of arenes substituted with π-electron donors is anticipated to lead to even more strongly reducing dimers. [RuCp*(1-(Me 2 N)-3,5-Me 2 C 6 H 3 )] + PF 6 − and [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] + PF 6 − have been synthesized and electrochemically and crystallographically characterized; both exhibit D + /D potentials slightly more cathodic than [RuCp*(1,3,5-R 3 C 6 H 3 )] + . Reduction of [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] + PF 6 − using silica-supported sodium–potassium alloy leads to a mixture of isomers of [RuCp*(1,4-(Me 2 N) 2 C 6 H 4 )] 2 , two of which have been crystallographically characterized. One of these isomers has a similar molecular structure to [RuCp*(1,3,5-Et 3 C 6 H 3 )] 2 ; the central C–C bond is exo , exo , i.e. , on the opposite face of both six-membered rings from the metals. A D + /0.5D 2 potential of −2.4 V is estimated for this exo , exo dimer, more reducing than that of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 (−2.0 V). This isomer reacts much more rapidly with both air and electron acceptors than [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 due to a much more cathodic D 2 ˙ + /D 2 potential. The other isomer to be crystallographically characterized, along with a third isomer, are both dimerized in an exo , endo fashion, representing the first examples of such dimers. Density functional theory calculations and reactivity studies indicate that the central bonds of these two isomers are weaker than those of the exo , exo isomer, or of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 , leading to estimated D + /0.5D 2 potentials of −2.5 and −2.6 V vs. FeCp 2 +/0 . At the same time the D 2 ˙ + /D 2 potentials for the exo , endo dimers are anodically shifted relative to those of [RuCp*(1,3,5-R 3 C 6 H 3 )] 2 , resulting in much greater air stability than for the exo , exo isomer. 

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5. A Nonheme Mononuclear {FeNO} ⁷ Complex that Produces N ₂ O in the Absence of an Exogenous Reductant

   https://doi.org/10.1002/anie.202109062  

   Dey, Aniruddha; Gordon, Jesse_B; Albert, Therese; Sabuncu, Sinan; Siegler, Maxime_A; MacMillan, Samantha_N; Lancaster, Kyle_M; Moënne‐Loccoz, Pierre; Goldberg, David_P (August 2021, Angewandte Chemie International Edition)

   Abstract A new nonheme iron(II) complex, Fe^II(Me₃TACN)((OSi^Ph2)₂O) (1), is reported. Reaction of1with NO_(g)gives a stable mononitrosyl complex Fe(NO)(Me₃TACN)((OSi^Ph2)₂O) (2), which was characterized by Mössbauer (δ=0.52 mm s⁻¹, |ΔE_Q|=0.80 mm s⁻¹), EPR (S=3/2), resonance Raman (RR) and Fe K‐edge X‐ray absorption spectroscopies. The data show that2is an {FeNO}⁷complex with anS=3/2 spin ground state. The RR spectrum (λ_exc=458 nm) of2combined with isotopic labeling (¹⁵N,¹⁸O) reveals ν(N‐O)=1680 cm⁻¹, which is highly activated, and is a nearly identical match to that seen for the reactive mononitrosyl intermediate in the nonheme iron enzyme FDPnor (ν(NO)=1681 cm⁻¹). Complex2reacts rapidly with H₂O in THF to produce the N‐N coupled product N₂O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N₂O in the absence of an exogenous reductant. 

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