- Rational synthesis and mutual conversion of Bis-N-heterocyclic diphosphanes and secondary N-heterocyclic phosphanes
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Symmetrical N-heterocyclic 1,1′,3,3′-tetrahydro-2,2′-bi- 1,3,2-diazaphospholes and 2,2′-bi-1,3,2-diazaphospholidines are prepared by time-saving, sequential "one-pot" syntheses starting from 1,4-diazabutadienes or N-alkyl or N-aryl-substituted ethane-1,2-
- Puntigam, Oliver,Foerster, Daniela,Giffin, Nick A.,Burck, Sebastian,Bender, Johannes,Ehret, Fabian,Hendsbee, Arthur D.,Nieger, Martin,Masuda, Jason D.,Gudat, Dietrich
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p. 2041 - 2050
(2013/05/22)
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- Controlled acrylate insertion regioselectivity in diazaphospholidine- sulfonato palladium(II) complexes
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Diazaphospholidine-sulfonato Pd(II) complexes [{κ2-P,O-(N- Ar2C2H4N2P)C6H 4SO3}PdMe(L)] 1-L (L = dmso, pyridine, lutidine, or μ-LiCl(solvent); 1a: Ar = Ph, 1b: Ar = 2-MeC6H4, 1c: Ar = 2-MeOC6H4, 1d: Ar = 2,4,6-Me3C 6H2, 1e: Ar = 2,6-iPr2C6H 3, 1f: Ar = 2,6-(p-tolyl)2C6H3) were prepared and structurally characterized. The regioselectivity of methyl acrylate (MA) insertion into the Pd-Me bond is entirely inverted from >93% 1,2-insertion for bulky substituents (1d-f, yielding the insertion products [(PO)Pd{κ2-C,O-CH2CHMeC(O)OMe], 12) to the usual electronically controlled 2,1-insertion (>95%) for the less bulky Ar = Ph (1a, yielding the insertion product [(PO)Pd{κ2-C,O- CHEtC(O)OMe], 11, and β-H elimination product methyl crotonate). DFT studies underline that this is due to a more favorable insertion transition state (2,1- favored by 12 kJ mol-1 over 1,2- for 1a) vs destabilization of the 2,1-insertion transition state in 1d,e. By contrast, MA insertion into the novel isolated and structurally characterized hydride and deuteride complexes [{κ2-P,O-(N-Ar2C 2H4N2P)C6H4SO 3}PdR(lutidine)] (Ar = 2,6-iPr2C6H3; 9e: R = H, 10e: R = D) occurs 2,1-selectively. This is due to the insertion occurring from the isomer with the P-donor and the olefin in trans arrangement, rather than the insertion into the alkyl from the cis isomer in which the olefin is in proximity to the bulky diazaphospholidine. 1a-f are precursors to active catalysts for ethylene polymerization to highly linear polyethylene with M n up to 35 000 g mol-1. In copolymerization experiments, norbornene was incorporated in up to 6.1 mol % into the polyethylene backbone.
- Wucher, Philipp,Roesle, Philipp,Falivene, Laura,Cavallo, Luigi,Caporaso, Lucia,Goettker-Schnetmann, Inigo,Mecking, Stefan
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p. 8505 - 8515
(2013/02/23)
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- Structure-Analytical Investigations of P-Substituted 1,3,2- Diazaphospholidines
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2-Diphenylphosphanyl-1,3,2-diazaphospholidines were prepared via metathesis from 2-chloro-1,3,2-diazaphospholidines and LiPPh2. For some of the products, symmetrisation to tetraphenyldiphosphane and 2,2′-bis-1,3,2- diazaphospholidinyls was observed. Most of the derivatives were characterised by single-crystal X-ray diffraction, which showed that all compounds studied feature elongated exocyclic P-Cl or P-P-bonds, respectively. The extent of this bond lengthening is in the P-phosphanyl-substituted species similar and in the P-chloro-derivatives less pronounced than in corresponding CC-unsaturated 1,3,2-diazaphospholenes. Structure correlation involving comparison of exocyclic P-X and endocyclic P-N distances suggests that n(N)/σ(P-X) hyperconjugation contributes strongly to the bond lengthening and induces a perceptible weakening of the P-P bonds in 2-diphenylphosphanyl-1,3,2- diazaphospholidines, which should render these compounds interesting substrates for P-P bond activation reactions. Copyright
- Puntigam, Oliver,Hajdok, Imre,Nieger, Martin,Niemeyer, Mark,Strobel, Sabine,Gudat, Dietrich
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p. 988 - 994
(2011/09/12)
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- N-Heterocyclic phosphenium cations: Syntheses and cycloaddition reactions
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A series of trifluoromethanesulfonate (OTf) salts of N-heterocyclic phospheniums (NHP) bearing phenyl (1a), para-methoxyphenyl (1b), 2,6-diisopropylphenyl (1c) and mesityl (1d) substituents is reported. The compounds 1b-d are made by a modification to a literature procedure that improves the overall yields for 1c and 1d by 15 and 23%, respectively. Two unwanted side-products in the synthesis of 1d, the diammonium salt, [(2,6-iPr-C6H3)N(H)2CH2CH 2N(H)2(2,6-iPr-C6H3)]Cl2 (4) and the bisphosphine (2,6-iPr-C6H3)N(PCl 2)CH2CH2N(PCl2)(2,6-iPr-C 6H3) (5), are crystallographically characterized, as is the intermediate cyclic chlorophosphine, C1PN(4-OMe-C6H 4)CH2CH2N(4-OMe-C6H4) (3b). The phenyl-substituted NHP 1a is fully characterized, including by X-ray crystallography, for the first time; this compound contains a short P-O contact of 2.1850(14) A Cycloaddition reactions of 1a-d with 2,3-dimethyl-1,3- butadiene give the expected spirocyclic phospholeniums, 7,8-dimethyl-1,4-diaryl- 1,4-diaza-5-phopshoniaspiro[4.4]non-7-ene, as their OTf salts (6a-d), while reactions with N,N′-dimesityl-1,4-diaza-1,3-butadiene give, except in the case of 1c, which is too bulky to react, the aza analogues, 1,4-dimesityl-6,9- diaryl-1,4,6,9-tetraaza-5-phosphoniaspiro[4.4]non-2-ene (7a, 7b and 7d). The sterically congested 7d is in thermal equilibrium with 1d and free diazadiene, and undergoes a substitution reaction with 2,3-dimethyl-1,3-butadiene to give 6d.
- Caputo, Christine A.,Price, Jacquelyn T.,Jennings, Michael C.,McDonald, Robert,Jones, Nathan D.
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p. 3461 - 3469
(2008/09/21)
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- Modular diamino- and dioxophosphine oxides and chlorides as ligands for transition-metal-catalyzed C-C and C-N couplings with aryl chlorides
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(Chemical Equation Presented) Air-stable diamino- and dioxophosphine oxides were used as ligands in palladium-catalyzed Suzuki reactions of aryl chlorides. Additionally, a diaminophosphine chloride was applied to palladium- and nickel-catalyzed C-C and C-N bond-forming reactions.
- Ackermann, Lutz,Born, Robert
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p. 2444 - 2447
(2007/10/03)
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