Abstract The overarching goal of this study is to effect the elimination of platinum from adducts withcis–C≡C−Pt−C≡C‐ linkages, thereby generating novel conjugated polyynes. Thus, the bis(hexatriynyl) complextrans‐(p‐tol3P)2Pt((C≡C)3H)2is treated with 1,3‐diphosphines R2C(CH2PPh2)2to generate (R2C(CH2PPh2)2)2Pt((C≡C)3H)2(14; R=c,n‐Bu;e,p‐tolCH2). These condense with the diiodide complexes R2C(CH2PPh2)2PtI2(9 a,c) in the presence of CuI (cat.) and excess HNEt2to give the title macrocycles [(R2C(CH2PPh2)2)Pt(C≡C)3]4(16 c,e) as adducts of the byproduct [H2NEt2]+I−(30–66 %). DOSY NMR experiments establish that this association is maintained in solution, but NaOAc removes the ammonium salt. The bis(triethylsilylpolyynyl) complexes (n‐Bu2C(CH2PPh2)2)Pt((C≡C)nSiEt3)2(n=2, 3) are synthesized analogously to14 c. They react with I2at rt to give mainly the diiodide complex9 cand the coupling product Et3Si(C≡CC≡C)nSiEt3. The possibility of competing reactions giving IC≡C species is investigated. Analogous reactions of the Pt4C24macrocycle16 calso give9 c, but no sp13C NMR signals or mass spectrometric Cxz+ions (x=24–100) could be detected. It is proposed that some cyclo[24]carbon is generated, but then rapidly converts to other forms of elemental carbon. No cyclotetracosane (C24H48) is detected when this sequence is carried out in the presence of PtO2and H2.
more »
« less
N -[6-(Dimethylamino)-9-phenyl-3 H -telluroxanthen-3-ylidene]- N -methylmethanaminium hexafluorophosphate monoclinic polymorph
The title compound C23H23N2Te+·PF6−, is a monoclinic polymorph of the previously reported triclinic structure [Calitreeet al.(2007).Organometallics,26, 6248–6257]. In the crystal, parallel offset π–π stacking [shortest centroid–centroid separation = 3.9620 (9) Å] and ionic interactions help to establish the packing.
more »
« less
- Award ID(s):
- 2003932
- PAR ID:
- 10515339
- Publisher / Repository:
- IUCr
- Date Published:
- Journal Name:
- IUCrData
- Volume:
- 6
- Issue:
- 6
- ISSN:
- 2414-3146
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The rotational barrier about the CN carbamate bond ofN‐(4‐hydroxybutyl)‐N‐(2,2,2‐trifluoroethyl)tert‐butyl carbamate1was determined by variable temperature (VT)13C and19F NMR spectroscopy. The −CH2CF3 appendage reports on rotational isomerism and allows for the observation of separate signals for the E‐ and Z‐ensembles at low temperature. The activation barrier for E/Z‐isomerization was quantified using Eyring‐Polanyi theory which requires the measurements of the maximum difference in Larmor frequency Δνmax and the convergence temperature Tc. Both Δνmax and Tc were interpolated by analyzing sigmoidal functions fitted to data describing signal separation and the quality of the superposition of the E‐ and Z‐signals, respectively. Methods for generating the quality‐of‐fit parameters for Lorentzian line shape analysis are discussed. Our best experimental value for the rotational barrier ΔGc≠(1)=15.65±0.13 kcal/mol is compared to results of a higher level ab initio study of the modelN‐ethyl‐N‐(2,2,2‐trifluoroethyl) methyl carbamate.more » « less
-
Bis(triphenylsulfonium) tetrachloridomanganate(II), (C18H15S)2[MnCl4] (I), triphenylsulfonium tetrachloridoferrate(III), (C18H15S)[FeCl4] (II), and bis(triphenylsulfonium) tetrachloridocobaltate(II), (C18H15S)2[CoCl4] (III), crystallize in the monoclinic space groupsP21/n[(I) and (III)] andP21/c[(II)]. Compounds (I) and (III) each contain two crystallographically independent triphenylsulfonium (TPS+) cations in the asymmetric unit, whereas (II) has one. In all three compounds, the sulfonium centers adopt distorted trigonal–pyramidal geometries, with S—C bond lengths falling roughly in the 1.78–1.79 Å range and C—S—C angles observed at about 101 to 106°. The [MCl4]n−anions (M= Mn2+, Fe3+, Co2+;n= 2,1,2) adopt slightly distorted tetrahedral geometries, withM—Cl bond lengths in the 2.19–2.38 Å range and Cl—M—Cl angles of approximately 104–113°. Hirshfeld surface analyses shows that H...H and H...C contacts dominate the TPS+cation environments, whereas H...Cl and shortM—S interactions link each [MCl4]n−anion to the surrounding cations. In (I) and (III), inversion-centered π–π stacking further consolidates the crystal packing, while in (II) no π–π interactions are observed.more » « less
-
Abstract Photolyses oftrans‐Fe(CO)3(P((CH2)n)3P) (n=10 (a), 12 (b), 14 (c), 16 (d), 18 (e)) in the presence of PMe3provide the first economical and scalable route to macrobicyclic dibridgehead diphosphines P((CH2)n)3P (1). These are isolated as mixtures ofin,in/out,outisomers that equilibrate with degeneratein,out/out,inisomers at 150 °C via pyramidal inversion at phosphorus. For the entire series, VT31P NMR data establish or boundKeq, rates, and activation parameters for a variety of phenomena, many of which involve homeomorphic isomerizations, topological processes by which certain molecules can turn themselves inside out (e. g.,in,in⇌out,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 adducts1 a,d ⋅ 2BH3are also characterized. Crystal structures ofout,out‐1 aandin,in‐1 a ⋅ 2BH3aid isomer assignments and reveal unusual cage conformations.more » « less
-
Abstract Reactions oftrans‐(C6F5)(p‐tol3P)2Pt(C≡C)nSiEt3(PtC2nSi;n=5, 7, 9) and excessPtClin the presence of wetn‐Bu4N+F−(to effect protodesilylation) under Sonogashira‐type conditions (CuCl, base, other additives) afford the title compoundsPtC10Pt,PtC14Pt, andPtC18Ptin 42–32 % yields. A four‐fold substitution of the phosphine ligands inPtC10Ptby PEt3affordsPt'C10Pt’(78 %), and a Sonogashira reaction ofPt'C2HandPt'ClaffordsPt'C2Pt’(68 %). The analogous reaction withPtC2SiandPtClis unsuccessful, presumably for steric reasons. The crystal structures ofPtC10Pt,PtC14Pt,Pt'C10Pt′, andPt'C2Pt’exhibit a number of interesting trends and features. Certain sp chain extension reactions that lead to or employ the precursorsPtC10Si,PtC12Si,PtC14Si, andPtC18Sisometimes give byproducts derived from C2loss, and possible origins are discussed. Related phenomena have been reported by others in the course of synthesizing extended conjugated polyynes.more » « less
An official website of the United States government

