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1. 10 ⁶ -fold faster C–H bond hydroxylation by a Co ^III,IV ₂ (µ-O) ₂ complex [via a Co ^III ₂ (µ-O)(µ-OH) intermediate] versus its Fe ^III Fe ^IV analog

   https://doi.org/10.1073/pnas.2307950120  

   Li, Yan; Abelson, Chase; Que, Lawrence; Wang, Dong (December 2023, Proceedings of the National Academy of Sciences)

   The hydroxylation of C–H bonds can be carried out by the high-valent Co^III,IV₂(µ-O)₂complex2asupported by the tetradentate tris(2-pyridylmethyl)amine ligand via a Co^III₂(µ-O)(µ-OH) intermediate (3a). Complex3acan be independently generated either by H-atom transfer (HAT) in the reaction of2awith phenols as the H-atom donor or protonation of its conjugate base, the Co^III₂(µ-O)₂complex1a. Resonance Raman spectra of these three complexes reveal oxygen-isotope-sensitive vibrations at 560 to 590 cm⁻¹associated with the symmetric Co–O–Co stretching mode of the Co₂O₂diamond core. Together with a Co•••Co distance of 2.78(2) Å previously identified for1aand2aby Extended X-ray Absorption Fine Structure (EXAFS) analysis, these results provide solid evidence for their “diamond core” structural assignments. The independent generation of3aallows us to investigate HAT reactions of2awith phenols in detail, measure the redox potential and pK_aof the system, and calculate the O–H bond strength (D_O–H) of3ato shed light on the C–H bond activation reactivity of2a. Complex3ais found to be able to transfer its hydroxyl ligand onto the trityl radical to form the hydroxylated product, representing a direct experimental observation of such a reaction by a dinuclear cobalt complex. Surprisingly, reactivity comparisons reveal2ato be 10⁶-fold more reactive in oxidizing hydrocarbon C–H bonds than corresponding Fe^III,IV₂(µ-O)₂and Mn^III,IV₂(µ-O)₂analogs, an unexpected outcome that raises the prospects for using Co^III,IV₂(µ-O)₂species to oxidize alkane C–H bonds. 

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2. Molecules that Turn Themselves Inside‐Out: Tuning in / out Equilibria and Homeomorphic Isomerization in Macrobicyclic Dibridgehead Diphosphines P((CH ₂ ) _n ) ₃ P Newly Accessible by Earth‐Abundant‐Metal Templates

   https://doi.org/10.1002/chem.202302200  

   Zarcone, Samuel R; Bhuvanesh, Nattamai; Gladysz, John A (December 2023, Chemistry – A European Journal)

   Photolyses of trans- Fe(CO)3(P((CH2)n)3P (n = 10 (a), 12 (b), 14 (c),16 (d), 18 (e)) in the presence of PMe3 provide the first economical and scalable route to macrobicyclic dibridgehead diphosphines P((CH2)n)3P (1). These are isolated as mixtures of in,in/out,out isomers that equilibrate with degenerate in,out/out,in isomers at 150 °C via pyramidal inversion at phosphorus. For the entire series, VT 31P NMR data establish or bound Keq rates, and activation parameters for a variety of phenomena, many of which involve homeomorphic isomerizations, topological processes by which certain molecules can turn themselve sinside out. This provides the first detailed mapping of such trends in homologous series of aliphatic bicyclic compounds XE((CH2)n)3EX with any type of bridgehead. Isomeric diborane adducts 1 a,d·2BH3 are also characterized. Crystal structures of out,out-1 a and in,in-1 a·2BH3 aid isomer assignments and reveal unusual cage conformations. 

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3. Macrobicyclic Dibridgehead Di(trialkyl)pnictogens E((CH ₂ ) _n ) ₃ E (E/ n = As/10, As/12, As/14, Sb/14) and Their Cage-like Metal Complexes: Syntheses, Structures, and Homeomorphic Isomerizations

   https://doi.org/10.1021/acs.organomet.4c00120  

   Zarcone, Samuel R; Verardi, Peter J; Chu, Gong M; Bhuvanesh, Nattamai; Gladysz, John A (June 2024, Organometallics)

   Photolyses of trans-Fe(CO)3(As((CH2)n)3As) (n =a, 10; b, 12; c, 14) in the presence of PMe3, or reactions of trans-[Fe(CO)2(NO)(As((CH2)n)3As)]+ BF4− and n-Bu4N+ Cl−, affordthe air stable title complexes As((CH2)n)3As (8a−c) in 79−34%yields. With 8a, the in, in and out, out isomers are separable andeach is crystallographically characterized. With 8b,c, the isomersrapidly interconvert by homeomorphic isomerization, but eachcrystallizes (contrathermodynamically) as an out, out isomer.Reactions of 8c with H2O2 or 8b with BH3 give 8c·2O or 8b·2BH3,respectively (85−94%). Reactions of 8c with MCl2 (M = Pt, Pd,Ni), Rh(CO)(Cl), and Fe(CO)3 sources afford the correspondingcage-like complexes trans-MLn(As((CH2)14)3As) (86−51%). Thecrystal structures of 8c·2O and the PtCl2 and PdCl2 adducts are determined and compared to those of 8a−c and diphosphorusanalogs. The corresponding distibine Sb((CH2)14)3Sb is analogously prepared, but precursors necessary for the bismuth analogcould not be accessed due to the diminished BiR3 Lewis basicity 

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4. Electronic structure of (MePh ₃ P) ₂ [Ni ^II (bdtCl ₂ ) ₂ ]·2(CH ₃ ) ₂ SO and (MePh ₃ P)[Ni ^III (bdtCl ₂ ) ₂ ] (bdtCl ₂ = 3,6-dichlorobenzene-1,2-dithiolate)

   https://doi.org/10.1107/S2052520621011495  

   Adamko Koziskova, Julia; Chen, Yu-Sheng; Grass, Su-Yin; Chuang, Yu-Chun; Hsu, I-Jui; Wang, Yu; Lutz, Martin; Volkov, Anatoliy; Herich, Peter; Vénosová, Barbora; et al (December 2021, Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials)

   High-resolution X-ray diffraction experiments, theoretical calculations and atom-specific X-ray absorption experiments were used to investigate two nickel complexes, (MePh 3 P) 2 [Ni II (bdtCl 2 ) 2 ]·2(CH 3 ) 2 SO [complex (1)] and (MePh 3 P)[Ni III (bdtCl 2 ) 2 ] [complex (2)]. Combining the techniques of nickel K - and sulfur K -edge X-ray absorption spectroscopy with high-resolution X-ray charge density modeling, together with theoretical calculations, the actual oxidation states of the central Ni atoms in these two complexes are investigated. Ni ions in two complexes are clearly in different oxidation states: the Ni ion of complex (1) is formally Ni II ; that of complex (2) should be formally Ni III , yet it is best described as a combination of Ni 2+ and Ni 3+ , due to the involvement of the non-innocent ligand in the Ni— L bond. A detailed description of Ni—S bond character (σ,π) is presented. 

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5. Electronic Structure of trans‐ [V ^II Cl ₂ (E(CH ₃ ) ₂ CH ₂ CH ₂ E(CH ₃ ) ₂ ) ₂ ], E=N, P

   https://doi.org/10.1002/ejic.202400395  

   Jafari, Mehrafshan G; Zolnhofer, Eva M; Fehn, Dominik; Heinemann, Frank W; Opalade, Adedamola A; Carroll, Patrick J; Meyer, Karsten; Krzystek, J; Ozarowski, Andrew; Mindiola, Daniel J; et al (November 2024, European Journal of Inorganic Chemistry)

   Abstract Coordination complexes of general formulatrans‐[MX₂(R₂ECH₂CH₂ER₂)₂] (M^II=Ti, V, Cr, Mn; E=N or P; R=alkyl or aryl) are a cornerstone of coordination and organometallic chemistry. We investigate the electronic properties of two such complexes,trans‐[VCl₂(tmeda)₂] andtrans‐[VCl₂(dmpe)₂], which thus representtrans‐[MX₂(R₂ECH₂CH₂ER₂)₂] where M=V, X=Cl, R=Me and E=N (tmeda) and P (dmpe). These V^IIcomplexes haveS=3/2 ground states, as expected for octahedral d³. Their tetragonal distortion leads to zero‐field splitting (zfs) that is modest in magnitude (D≈0.3 cm⁻¹) relative to analogousS=1 Ti^IIand Cr^IIcomplexes. This parameter was determined from conventional EPR spectroscopy, but more effectively from high‐frequency and ‐field EPR (HFEPR) that determined the sign ofDas negative for the diamine complex, but positive for the diphosphine, which information had not been known for anytrans‐[VX₂(R₂ECH₂CH₂ER₂)₂] systems. The ligand‐field parameters oftrans‐[VCl₂(tmeda)₂] andtrans‐[VCl₂(dmpe)₂] are obtained using both classical theory andab initioquantum chemical theory. The results shed light not only on the electronic structure of V^IIin this environment, but also on differences between N and P donor ligands, a key comparison in coordination chemistry. 

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