- Synthesis, Characterization, and Catalytic Reactivity of {CoNO}8PCP Pincer Complexes
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The reaction of coordinatively unsaturated Co(II) PCP pincer complexes with nitric oxide leads to the formation of new, air-stable, diamagnetic mono nitrosyl compounds. The synthesis and characterization of five- and four-coordinate Co(III) and Co(I) nitrosyl pincer complexes based on three different ligand scaffolds is described. Passing NO through a solution of [Co(PCPNMe-iPr)Cl], [Co(PCPO-iPr)Cl] or [Co(PCPCH2-iPr)Br] led to the formation of the low-spin complex [Co(PCP-iPr)(NO)X] with a strongly bent NO ligand. Treatment of the latter species with (X = Cl, Br) AgBF4 led to chloride abstraction and formation of cationic square-planar Co(I) complexes of the type [Co(PCP-iPr)(NO)]+ featuring a linear NO group. This reaction could be viewed as a formal two electron reduction of the metal center by the NO radical from Co(III) to Co(I), if NO is counted as NO+. Hence, these systems can be described as {CoNO}8 according to the Enemark-Feltham convention. X-ray structures, spectroscopic and electrochemical data of all nitrosyl complexes are presented. Preliminary studies show that [Co(PCPNMe-iPr)(NO)]+ catalyzes efficiently the reductive hydroboration of nitriles with pinacolborane (HBpin) forming an intermediate {CoNO}8 hydride species.
- Pecak, Jan,Eder, Wolfgang,St?ger, Berthold,Realista, Sara,Martinho, Paulo N.,Calhorda, Maria José,Linert, Wolfgang,Kirchner, Karl
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p. 2594 - 2601
(2020/06/22)
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- Old Concepts, New Application – Additive-Free Hydrogenation of Nitriles Catalyzed by an Air Stable Alkyl Mn(I) Complex
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An efficient additive-free manganese-catalyzed hydrogenation of nitriles to primary amines with molecular hydrogen is described. The pre-catalyst, a well-defined bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dpre)(CO)3(CH3)] (dpre=1,2-bis(di-n-propylphosphino)ethane), undergoes CO migratory insertion into the manganese-alkyl bond to form acyl complexes which upon hydrogenolysis yields the active coordinatively unsaturated Mn(I) hydride catalyst [Mn(dpre)(CO)2(H)]. A range of aromatic and aliphatic nitriles were efficiently and selectively converted into primary amines in good to excellent yields. The hydrogenation of nitriles proceeds at 100 °C with a catalyst loading of 2 mol % and a hydrogen pressure of 50 bar. Mechanistic insights are provided by means of DFT calculations. (Figure presented.).
- Weber, Stefan,Veiros, Luis F.,Kirchner, Karl
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supporting information
p. 5412 - 5420
(2019/11/13)
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- Reusable Nickel Nanoparticles-Catalyzed Reductive Amination for Selective Synthesis of Primary Amines
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The preparation of nickel nanoparticles as efficient reductive amination catalysts by pyrolysis of in situ generated Ni-tartaric acid complex on silica is presented. The resulting stable and reusable Ni-nanocatalyst enables the synthesis of functionalized and structurally diverse primary benzylic, heterocyclic and aliphatic amines starting from inexpensive and readily available carbonyl compounds and ammonia in presence of molecular hydrogen. Applying this Ni-based amination protocol, -NH2 moiety can be introduced in structurally complex compounds, for example, steroid derivatives and pharmaceuticals.
- Murugesan, Kathiravan,Beller, Matthias,Jagadeesh, Rajenahally V.
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supporting information
p. 5064 - 5068
(2019/03/19)
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- Hydrogenation of Nitriles and Ketones Catalyzed by an Air-Stable Bisphosphine Mn(I) Complex
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Efficient hydrogenations of nitriles and ketones with molecular hydrogen catalyzed by a well-defined bench-stable bisphosphine Mn(I) complex are described. These reactions are environmentally benign and atomically economic, implementing an inexpensive, earth-abundant nonprecious metal catalyst. A range of aromatic and aliphatic nitriles and ketones were efficiently converted into primary amines and alcohols, respectively, in good to excellent yields. The hydrogenation of nitriles proceeds at 100 °C with catalyst loading of 2 mol % and 20 mol % base (t-BuOK), while the hydrogenation of ketones takes place already at 50 °C, with a catalyst loading of 1 mol % and 5 mol % of base. In both cases, a hydrogen pressure of 50 bar was applied.
- Weber, Stefan,St?ger, Berthold,Kirchner, Karl
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supporting information
p. 7212 - 7215
(2018/11/25)
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- Boron-Catalyzed Silylative Reduction of Nitriles in Accessing Primary Amines and Imines
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Silylative reduction of nitriles was studied under transition metal-free conditions by using B(C6F5)3 as a catalyst with hydrosilanes as a reductant. Alkyl and (hetero)aryl nitriles were efficiently converted to primary amines or imines under mild conditions. The choice of silanes was found to determine the selectivity: while a full reduction of nitriles was highly facile, the use of sterically bulky silanes allowed for the partial reduction leading to N-silylimines.
- Gandhamsetty, Narasimhulu,Jeong, Jinseong,Park, Juhyeon,Park, Sehoon,Chang, Sukbok
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p. 7281 - 7287
(2015/07/28)
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