An official website of the United States government
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
A Nontemplated Route to Macrocyclic Dibridgehead Diphosphorus Compounds: Crystallographic Characterization of a “Crossed‐Chain” Variant of in / out Stereoisomers
Abstract Reactions of (O=)PH(OCH2CH3)2and BrMg(CH2)mCH=CH2(4.9–3.2 equiv;m=4 (a), 5 (b), 6 (c)) give the dialkylphosphine oxides (O=)PH[(CH2)mCH=CH2]2(2 a–c; 77–81 % after workup), which are treated with NaH and then α,ω‐dibromides Br(CH2)nBr (0.49–0.32 equiv;n=8 (a′), 10 (b′), 12 (c′), 14 (d′)) to yield the bis(trialkylphosphine oxides) [H2C=CH(CH2)m]2P(=O)(CH2)n(O=)P[(CH2)mCH=CH2]2(3 ab′,3 bc′,3 cd′,3 ca′; 79–84 %). Reactions of3 bc′and3 ca′with Grubbs’ first‐generation catalyst and then H2/PtO2afford the dibridgehead diphosphine dioxides(4 bc′,4 ca′; 14–19 %,n′=2m+2);31P NMR spectra show two stereoisomeric species (ca. 70:30). Crystal structures of two isomers of the latter are obtained,out,out‐4 ca′and a conformer ofin,out‐4 ca′that features crossed chains, such that the (O=)P vectors appearout,out. Whereas4 bc′resists crystallization, a byproduct derived from an alternative metathesis mode, (CH2)12P(=O)(CH2)12(O=)P(CH2)12, as well as3 ab′and3 bc′, are structurally characterized. The efficiencies of other routes to dibridgehead diphosphorus compounds are compared.
more »
« less
- PAR ID:
- 10067338
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – An Asian Journal
- Volume:
- 13
- Issue:
- 18
- ISSN:
- 1861-4728
- Format(s):
- Medium: X Size: p. 2632-2640
- Size(s):
- p. 2632-2640
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Two routes to the title compounds are evaluated. First, a ca. 0.01 M CH 2 Cl 2 solution of H 3 B·P((CH 2 ) 6 CH=CH 2 ) 3 ( 1 ·BH 3 ) is treated with 5 mol % of Grubbs' first generation catalyst (0 °C to reflux), followed by H 2 (5 bar) and Wilkinson's catalyst (55 °C). Column chromatography affords H 3 B·P( n- C 8 H 17 ) 3 (1%), H 3 B· P ((CH 2 ) 13 C H 2 )( n -C 8 H 17 ) (8%; see text for tie bars that indicate additional phosphorus–carbon linkages, which are coded in the abstract with italics), H 3 B· P ((CH 2 ) 13 C H 2 )((CH 2 ) 14 ) P ((CH 2 ) 13 C H 2 )·BH 3 ( 6 ·2BH 3 , 10%), in,out -H 3 B·P((CH 2 ) 14 ) 3 P·BH 3 ( in,out - 2 ·2BH 3 , 4%) and the stereoisomer ( in,in / out,out )- 2 ·2BH 3 (2%). Four of these structures are verified by independent syntheses. Second, 1,14-tetradecanedioic acid is converted (reduction, bromination, Arbuzov reaction, LiAlH 4 ) to H 2 P((CH 2 ) 14 )PH 2 ( 10 ; 76% overall yield). The reaction with H 3 B·SMe 2 gives 10 ·2BH 3 , which is treated with n -BuLi (4.4 equiv) and Br(CH 2 ) 6 CH=CH 2 (4.0 equiv) to afford the tetraalkenyl precursor (H 2 C=CH(CH 2 ) 6 ) 2 (H 3 B)P((CH 2 ) 14 )P(BH 3 )((CH 2 ) 6 CH=CH 2 ) 2 ( 11 ·2BH 3 ; 18%). Alternative approaches to 11 ·2BH 3 (e.g., via 11 ) were unsuccessful. An analogous metathesis/hydrogenation/chromatography sequence with 11 ·2BH 3 (0.0010 M in CH 2 Cl 2 ) gives 6 ·2BH 3 (5%), in,out - 2 ·2BH 3 (6%), and ( in,in / out,out )- 2 ·2BH 3 (7%). Despite the doubled yield of 2 ·2BH 3 , the longer synthesis of 11 ·2BH 3 vs 1 ·BH 3 renders the two routes a toss-up; neither compares favorably with precious metal templated syntheses.more » « less
-
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
-
ABSTRACT This work investigates effects of poly(γ‐butyrolactone) (PγBL) with different initiation and termination chain ends on five types of materials properties, including thermal stability, thermal transitions, thermal recyclability, hydrolytic degradation, and dynamic mechanical behavior. Four different chain‐end‐capped polymers with similar molecular weights, BnO‐[C(=O)(CH2)3O]n‐R, R = C(=O)Me, C(=O)CH=CH2, C(=O)Ph, and SiMe2CMe3, along with a series of uncapped polymers R′O‐[C(=O)(CH2)3O]n‐H (R′ = Bn, Ph2CHCH2) withMnranging from low (4.95 kg mol−1) to high (83.2 kg mol−1), have been synthesized. The termination chain end R showed a large effect on polymer decomposition temperature and hydrolytic degradation, relative to H. Overall, for those properties sensitive to the chain ends, chain‐end capping renders R‐protected linear PγBL behaving much like cyclic PγBL. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2018,56, 2271–2279more » « less
-
Abstract The dialkyl malonate derived 1,3‐diphosphines R2C(CH2PPh2)2(R=a, Me;b, Et;c,n‐Bu;d,n‐Dec;e, Bn;f,p‐tolCH2) are combined with (p‐tol3P)2PtCl2ortrans‐(p‐tol3P)2Pt((C≡C)2H)2to give the chelatescis‐(R2C(CH2PPh2)2)PtCl2(2 a–f, 94–69 %) orcis‐(R2C(CH2PPh2)2)Pt((C≡C)2H)2(3 a–f, 97–54 %). Complexes3 a–dare also available from2 a–dand excess 1,3‐butadiyne in the presence of CuI (cat.) and excess HNEt2(87–65 %). Under similar conditions,2and3react to give the title compounds [(R2C(CH2PPh2)2)[Pt(C≡C)2]4(4 a–f; 89–14 % (64 % avg)), from which ammonium salts such as the co‐product [H2NEt2]+Cl−are challenging to remove. Crystal structures of4 a,bshow skew rhombus as opposed to square Pt4geometries. The NMR and IR properties of4 a–fare similar to those of mono‐ or diplatinum model compounds. However, cyclic voltammetry gives only irreversible oxidations. As compared to mono‐platinum or Pt(C≡C)2Pt species, the UV‐visible spectra show much more intense and red‐shifted bands. Time dependent DFT calculations define the transitions and principal orbitals involved. Electrostatic potential surface maps reveal strongly negative Pt4C16cores that likely facilitate ammonium cation binding. Analogous electronic properties of Pt3C12and Pt5C20homologs and selected equilibria are explored computationally.more » « less
