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

Photolyses of -Fe(CO)(As((CH) )As) ( = , 10; , 12; , 14) in the presence of PMe, or reactions of -[Fe(CO)(NO)(As((CH) )As)] BF and -BuN Cl, afford the air stable title complexes As((CH) )As (-) in 79-34% yields. With , the , and , isomers are separable and each is crystallographically characterized. With ,, the isomers rapidly interconvert by homeomorphic isomerization, but each crystallizes (contrathermodynamically) as an , isomer.

Platinum Elimination from Bis(triethylsilylpolyynyl) Complexes (n-BuC(CHPPh))Pt((C≡C)SiEt) (n=2, 3) and Macrocycles Comprised of Four LPt Corners and Four C≡CC≡CC≡C Linkers; An Approach to Cyclo[24]carbon.

The overarching goal of this study is to effect the elimination of platinum from adducts with cis -C≡C-Pt-C≡C- linkages, thereby generating novel conjugated polyynes. Thus, the bis(hexatriynyl) complex trans-(p-tolP)Pt((C≡C)H) is treated with 1,3-diphosphines RC(CHPPh) to generate (RC(CHPPh))Pt((C≡C)H) (14; R=c, n-Bu; e, p-tolCH). These condense with the diiodide complexes RC(CHPPh)PtI (9 a,c) in the presence of CuI (cat.

A Caged Neutral 17-Valence-Electron Iron(I) Radical [Fe(CO)(Cl)(P((CH))P)]: Synthetic, Structural, Spectroscopic, Redox, and Computational Studies.

UV irradiation of yellow CHCl solutions of -Fe(CO)(P((CH))P) () and PMe (10 equiv) gives, in addition to the previously reported dibridgehead diphosphine P((CH))P (46%), a green paramagnetic complex that crystallography shows to be the trigonal-bipyramidal iron(I) radical -[Fe(CO)(Cl)(P((CH))P)] (; 31% after workup). This is a rare example of an isolable species of the formula [Fe(CO)(L)(X)] ( = 0-3, L = two-electron-donor ligand; X = one-electron-donor ligand). Analogous precursors with longer P(CH)P segments ( = 12, 14, 16, 18) give only the demetalated diphosphines, and a rationale is proposed.

Reactions of Platinum Terminal Polyynyl Complexes -(CF)(-tolP)Pt(C≡C)H ( = 2-4) and -BuLi, Generation of Functional Equivalents of Pt(C≡C)Li Species, and Derivatization with Organic and Inorganic Electrophiles.

Reactions of the title complexes and -BuLi (1.5 equiv, -45 °C) afford functional equivalents of the deprotonated species -(CF)(-tolP)Pt(C≡C)Li ( = 2-4), as assayed by subsequent additions of MeI or MeSiCl to give -(CF)(-tolP)Pt(C≡C)Me (66-52%) or -(CF)(-tolP)Pt(C≡C)SiMe (63-49%). However, P NMR data suggest more complicated mechanistic scenarios, and small amounts of the hydride complex -(CF)(-tolP)PtH (independently synthesized from the chloride complex, AgClO, and NaBH) are detected in most cases.

Building Blocks for Molecular Polygons Based on Platinum Vertices and Polyynediyl Edges.

Reactions of ClP(CH)PCl and -MgBrCHX (X = /OMe, /OBu, /Bu, /SiMe) give the diphosphines (-XCH)P(CH)P(-CHX) (-; 47-66%). Additions of , to (COD)PtCl yield (CH(CHP(-CHX)))PtCl (,; 62-88%), which upon reaction with butadiyne (2 equiv; HNEt/cat. CuI) give (CH(CHP(-CHX)))Pt((C≡C)H) (,; 34-76%).

Syntheses, homeomorphic and configurational isomerizations, and structures of macrocyclic aliphatic dibridgehead diphosphines; molecules that turn themselves inside out.

The diphosphine complexes - or -[upper bond 1 start]PtCl(P((CH) )P[upper bond 1 end]) ( = b/12, c/14, d/16, e/18) are demetalated by MC[triple bond, length as m-dash]X nucleophiles to give the title compounds (P((CH) ))P (3b-e, 91-71%). These "empty cages" react with PdCl or PtCl sources to afford -[upper bond 1 start]MCl(P((CH) )P[upper bond 1 end]). Low temperature P NMR spectra of 3b and c show two rapidly equilibrating species (3b, 86 : 14; 3c, 97 : 3), assigned based upon computational data to , (major) and , isomers.

Shortwave Infrared Fluorofluorophores for Multicolor In Vivo Imaging.

Developing chemical tools to detect and influence biological processes is a cornerstone of chemical biology. Here we combine two tools which rely on orthogonality- perfluorocarbons and multiplexed shortwave infrared (SWIR) fluorescence imaging- to visualize nanoemulsions in real time in living mice. Drawing inspiration from fluorous and SWIR fluorophore development, we prepared two SWIR-emissive, fluorous-soluble chromenylium polymethine dyes.

Rethinking premedical education.

The world needs more physicians. Increasing their numbers alone won't solve the many problems associated with improving health care. But it doesn't help to have a dearth of doctors, who were generally in short supply before COVID-19 struck.

A new supramolecular bonding motif involving NH bonds of ammonium salts and macrocycles derived from platinum corners and butadiynediyl linkers.

CuI catalyzes reactions of -(RC(CHPPh))Pt(CCCCH) and -(RC(CHPPh))PtI in secondary amine solvents HNR' to give the title adducts [(RC(CHPPh))Pt(CCCC)]·(HNR'I) (R/R'/ = Me/Et/1, Me/((CHCH)O)/3, Et/Et/1, Et/CHCHCH/1; 92-42%). Crystal structures of these or closely related species establish folded Pt cores containing ammonium cation guests, with NH/ and NCH/CC hydrogen bonding. DOSY NMR experiments show that the host/guest relationship can be maintained in solution.

Square-Planar and Octahedral Gyroscope-Like Metal Complexes Consisting of Dipolar Rotators Encased in Dibridgehead Di(triaryl)phosphine Stators: Syntheses, Structures, Dynamic Properties, and Reactivity.

For a variety of purposes, it is of interest to embed metals in cagelike -spanning di(triaryl)phosphine ligands. Toward this end, a combination of P(-CHO(CH)CH═CH) [; = 4 (), 5 (), 6 (), and 7 ()], [Rh(COD)(μ-Cl)], and CO gives square-planar -Rh(CO)(Cl)[P(-CHO(CH)CH═CH)] (-). Reactions of - with Grubbs' catalyst (first generation) and then H (catalyst PtO) yield the title compounds -Rh(CO)(Cl)[P(-CHO(CH)O--CH)P] ( = 2 + 2, -; 26-41% from -).

Mechanism of Coupling of Methylidene to Ethylene Ligands in Dimetallic Assemblies; Computational Investigation of a Model for a Key Step in Catalytic C Chemistry.

Methylidene complexes often couple to ethylene complexes, but the mechanistic insight is scant. The path by which two cations [(η-CH)Re(NO)(PPh)(═CH)] () transform (CHCl/acetonitrile) to [(η-CH)Re(NO)(PPh)(HC═CH)] () and [(η-CH)Re(NO)(PPh)(NCCH)] is studied by density functional theory. Experiments provide a number of constraints such as the second-order rate in ; no prior ligand dissociation/exchange; a faster reaction of ()- with ()- than with ()- ("enantiomer self-recognition").

Tracking Energy Transfer across a Platinum Center.

Rigid, conjugated alkyne bridges serve as important components in various transition-metal complexes used for energy conversion, charge separation, sensing, and molecular electronics. Alkyne stretching modes have potential for modulating charge separation in donor-bridge-acceptor compounds. Understanding the rules of energy relaxation and energy transfer across the metal center in such compounds can help optimize their electron transfer switching properties.

A surprise landing on the of macrocyclic dibridgehead diorganoarsines: syntheses, structures, and reactivities.

Reactions of -[Fe(CO)(NO)(As((CH))As)] BF ( = 10, 12, 14) and BuN Cl afford the title compounds As((CH))As, which upon reaction ( = 14) with MCl (M = Pt, Ni), Rh(CO)(Cl), and Fe(CO) sources reconstitute cage like complexes -ML(As((CH))As). Reactions with HO and BH give the corresponding arsine oxides and boranes. Crystal structures of metal-free species reveal , isomers, but cage complex formation is proposed to entail homeomorphic isomerization to , isomers with directed lone pairs.

Syntheses, rearrangements, and structural analyses of unsaturated nitrogen donor ligands derived from diphenyldiazomethane and the chiral rhenium Lewis acid [(η-CH)Re(NO)(PPh)].

Diphenyldiazomethane and a labile chlorobenzene complex of [(η-CH)Re(NO)(PPh)] BF react to give the η adduct [(η-CH)Re(NO)(PPh)(NNCPh)] BF (73%). When this is conducted in the presence of copper powder, a 3-phenyl-1-indazole complex derived from carbon-hydrogen bond activation, [(η-CH)Re(NO)(PPh)(NC(Ph)CCHCHCHCHCNH)] BF, is obtained (65%). Subsequent reaction with NaOCH gives indazolyl complex (η-CH)Re(NO)(PPh)(NCCHCHCHCHCC(Ph)N) (85%), derived from NH deprotonation and a 1,2-rhenium shift.

Platinum(II) alkyl complexes of chelating dibridgehead diphosphines P((CH))P ( = 14, 18, 22); facile / isomerizations interconverting gyroscope and parachute like adducts.

The gyroscope like dichloride complexes -Pt(Cl)(P((CH))P) (-2; = c, 14; e, 18; g, 22) and MeLi (2 equiv.) react to yield the parachute like dimethyl complexes -Pt(Me)(P((CH))P) (-4c,e,g, 70-91%). HCl (1 equiv.

Syntheses, Structures, Reactivities, and Basicities of Quinolinyl and Isoquinolinyl Complexes of an Electron Rich Chiral Rhenium Fragment and Their Electrophilic Addition Products.

Reactions of Li [(η -C H )Re(NO)(PPh )] with 2- and 4-chloroquinoline or 1-chloroisoquinoline give the corresponding σ quinolinyl and isoquinolinyl complexes 3, 6, and 8. With 3 and 8 there is further protonation to yield HCl adducts, but additions of KH give the free bases. Treatment of 3 with HBF ⋅OEt or H(OEt ) BAr gives the quinolinium salts [(η -C H )Re(NO)(PPh )(C(NH)C(CH) C(CH)(CH))] X (3-H X ; X =BF /BAr , 94-98 %).

Macrocyclic Complexes Derived from Four cis-L Pt Corners and Four Butadiynediyl Linkers; Syntheses, Electronic Structures, and Square versus Skew Rhombus Geometries.

The dialkyl malonate derived 1,3-diphosphines R C(CH PPh ) (R=a, Me; b, Et; c, n-Bu; d, n-Dec; e, Bn; f, p-tolCH ) are combined with (p-tol P) PtCl or trans-(p-tol P) Pt((C≡C) H) to give the chelates cis-(R C(CH PPh ) )PtCl (2 a-f, 94-69 %) or cis-(R C(CH PPh ) )Pt((C≡C) H) (3 a-f, 97-54 %). Complexes 3 a-d are also available from 2 a-d and excess 1,3-butadiyne in the presence of CuI (cat.) and excess HNEt (87-65 %).

Gyroscopes and the Chemical Literature, 2002-2020: Approaches to a Nascent Family of Molecular Devices.

Research directed toward the goal of molecular gyroscopes since the coverage of a previous review (2002) is described. Such species are a subclass of molecular rotors, which are comprised of rotators and stators. Major categories include (1) systems in which a rotator is embedded in a cage-like stator reminiscent of mechanical toy gyroscopes and (2) molecules that have been engineered to crystallize with parallel rotators and voids or other features that enable the rotator to rotate in the solid state (amphidynamic crystals).

Toward Frameworks with Multiple Aligned and Interactive Fe(CO) Rotators: Syntheses and Structures of Diiron Complexes Linked by Two -Diaxial α,ω-Diphosphine Ligands ArP(CH)PAr.

Reactions of (η-benzylideneacetone)Fe(CO) and the α,ω-diphosphines ArP(CH)PAr afford the trigonal bipyramidal diiron tetraphosphorus complexes ,-(CO)Fe[ArP(CH)PAr]Fe(CO) (/Ar = 3/Ph , 4/Ph , 4/-tol ; 56-19%). Crystal structures establish essentially parallel P-Fe-P axes, iron-iron distances of 5.894(9)-5.

Launching Werner Complexes into the Modern Era of Catalytic Enantioselective Organic Synthesis.

Reactions catalyzed by transition metal complexes almost always entail binding of one or more reactants to the metal center, and nearly every corner of the "chiral pool" has been picked over in efforts to develop enantioselective catalysts. As reported by Alfred Werner in 1911-1912, salts of the formally -symmetric [Co(en)] trication (en = ethylenediamine) were among the first chiral inorganic compounds to be resolved into enantiomers. These air- and water-stable complexes are substitution-inert, so for 100 years they languished without application in organic synthesis.

Λ-[Co((,)-dpen)] 2IB(CF): A Second Generation Air- and Water-Stable Chiral Solvating Agent for Chirality Sensing (dpen = NHCHPhCHPhNH).

When CDCl solutions of chiral racemic molecules containing moderately Lewis basic functional groups are treated with the chiral solvating agent (CSA) Λ-[Co((,)-dpen)] 2IB(CF) (Λ-(,)- 2IB(CF)), baseline-resolved NMR signals are observed for the enantiomers (29 diverse analytes). Only 0.62-100 mol % loadings are required (avg 14.