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1. Platinum( ii ) alkyl complexes of chelating dibridgehead diphosphines P((CH ₂ ) _n ) ₃ P ( n = 14, 18, 22); facile cis / trans isomerizations interconverting gyroscope and parachute like adducts

   https://doi.org/10.1039/D1DT02321G  

   Zhu, Yun; Ehnbom, Andreas; Fiedler, Tobias; Shu, Yi; Bhuvanesh, Nattamai; Hall, Michael B.; Gladysz, John A. (September 2021, Dalton Transactions)

   The gyroscope like dichloride complexes trans -Pt(Cl) 2 (P((CH 2 ) n ) 3 P) ( trans -2; n = c, 14; e, 18; g, 22) and MeLi (2 equiv.) react to yield the parachute like dimethyl complexes cis -Pt(Me) 2 (P((CH 2 ) n ) 3 P) ( cis -4c,e,g, 70–91%). HCl (1 equiv.) and cis -4c react to give cis -Pt(Cl)(Me)(P((CH 2 ) 14 ) 3 P) ( cis -5c, 83%), which upon stirring with silica gel or crystallization affords trans -5c (89%). Similar reactions of HCl and cis -4e,g give cis / trans -5e,g mixtures that upon stirring with silica gel yield trans -5e,g. A parallel sequence with trans -2c/EtLi gives cis -Pt(Et) 2 (P((CH 2 ) 14 ) 3 P) ( cis -6c, 85%) but subsequent reaction with HCl affords trans -Pt(Cl)(Et)(P((CH 2 ) 14 ) 3 P) ( trans -7c, 45%) directly. When previously reported cis -Pt(Ph) 2 (P((CH 2 ) 14 ) 3 P) is treated with HCl (1 equiv.), cis - and trans -Pt(Cl)(Ph)(P((CH 2 ) 14 ) 3 P) are isolated (44%, 29%), with the former converting to the latter at 100 °C. Reactions of trans -5c and LiBr or NaI afford the halide complexes trans -Pt(X)(Me)(P((CH 2 ) 14 ) 3 P) ( trans -9c, 88%; trans -10c, 87%). Thermolyses and DFT calculations that include acyclic model compounds establish trans > cis stabilities for all except the dialkyl complexes, for which energies can be closely spaced. The σ donor strengths of the non-phosphine ligands are assigned key roles in the trends. The crystal structures of cis -4c, trans -5c, trans -7c, and trans -10c are determined and analyzed together with the computed structures. 

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2. Substituent Effect on the Circularly Polarized Luminescence of C ₁ ‐Symmetric Carbene‐Copper(I) Complexes

   https://doi.org/10.1002/cptc.202100068  

   Braker, Erin_E; Mukthar, Nishya_F_M; Schley, Nathan_D; Ung, Gaël (June 2021, ChemPhotoChem)

   Abstract The substituent effect on the magnitude of the circularly polarized luminescence (CPL) of^MentCAAC‐Cu‐X (X=F, Cl, Br, I, BH₄, B₃H₈; CAAC=cyclic (alkyl)(amino)carbenes) complexes is experimentally investigated. This study examines seven pairs of enantiomeric complexes with small anionic substituents (halides, borohydrides, hydride). The complexes are fully characterized, including single crystal X‐ray diffraction studies, and chiroptical measurements show that small covalent anions induce a larger CPL magnitude. These results demonstrate that the magnitude of the CPL can be manipulated without making any modifications to the chiral ligand. 

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3. Activator-free single-component Co( i )-catalysts for regio- and enantioselective heterodimerization and hydroacylation reactions of 1,3-dienes. New reduction procedures for synthesis of [L]Co( i )-complexes and comparison to in situ generated catalysts

   https://doi.org/10.1039/d2dt01484j  

   Parsutkar, Mahesh M.; Moore, Curtis E.; RajanBabu, T. V. (June 2022, Dalton Transactions)

   Warren Piers (Ed.)

   Although cobalt( i ) bis-phosphine complexes have been implicated in many selective C–C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt( i )-bis-phosphine complexes and their use in Co( i )-catalyzed reactions. We find that easily prepared ( in situ generated or isolated) bis-phosphine and (2,6- N -aryliminoethyl)pyridine (PDI) cobalt( ii ) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li 3 N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt( i ) complex crystallizes as a phosphine-bridged species [(P∼P)(X)Co I [μ-(P∼P)]Co I (X)(P∼P)] or a halide-bridged species [(P∼P)Co I [μ-(X)] 2 Co I (P∼P)]. Because the side-products are innocuous, these methods can be used for the in situ generation of catalytically competent Co( i ) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P∼P)Co I -η 4 -diene] + X − or [(P∼P)Co I -η 6 -arene] + X − complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented. 

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4. In silico screening of P , N -ligands facilitates optimization of Au( iii )-mediated S -arylation

   https://doi.org/10.1039/D4SC05920D  

   Treacy, Joseph W; Tilden, James_A R; Chao, Elaine Y; Fu, Zihuan; Spokoyny, Alexander M; Houk, K N; Maynard, Heather D (February 2025, Chemical Science)

   In silicoexamination of 13P,N-ligated Au(iii) OACs determined the key mechanistic factors governing Au(iii)-mediatedS-arylation. Three complexes were synthesized which exhibited bimolecular coordination rate constants as high as 20 200 M⁻¹s⁻¹. 

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5. Bridging DNA contacts allow Dps from E. coli to condense DNA

   https://doi.org/10.1093/nar/gkae223  

   Shahu, Sneha; Vtyurina, Natalia; Das, Moumita; Meyer, Anne S.; Ganji, Mahipal; Abbondanzieri, Elio A. (April 2024, Nucleic Acids Research)

   Abstract The DNA-binding protein from starved cells (Dps) plays a crucial role in maintaining bacterial cell viability during periods of stress. Dps is a nucleoid-associated protein that interacts with DNA to create biomolecular condensates in live bacteria. Purified Dps protein can also rapidly form large complexes when combined with DNA in vitro. However, the mechanism that allows these complexes to nucleate on DNA remains unclear. Here, we examine how DNA topology influences the formation of Dps–DNA complexes. We find that DNA supercoils offer the most preferred template for the nucleation of condensed Dps structures. More generally, bridging contacts between different regions of DNA can facilitate the nucleation of condensed Dps structures. In contrast, Dps shows little affinity for stretched linear DNA before it is relaxed. Once DNA is condensed, Dps forms a stable complex that can form inter-strand contacts with nearby DNA, even without free Dps present in solution. Taken together, our results establish the important role played by bridging contacts between DNA strands in nucleating and stabilizing Dps complexes. 

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