An important parameter for the calculating of rate constants
or
for process enhancement, both for sciences and engineering, is the
knowledge of gas concentrations of gas–liquid systems. We introduce
the method SelPULCON for the determination of gas concentrations in
liquids for NMR active substances (e.g., hydrogen) by means of NMR
spectroscopy. This method is based on the “principle of reciprocity”
and correlates the absolute signal intensity of the sample with that
of an external reference. As a selective excitation is applied, this
method is independent of whether the solvent is deuterated or not.
In this way one can measure the gas concentration in almost all solutions
and utilize all of the advantages of the NMR spectroscopy (e.g., for
in situ or OPERANDO investigations). To demonstrate this method, we
determined the hydrogen saturation concentrations in eight organic
solvents at 25 °C and 0.101 MPa total pressure, for example,
in dichloromethane (c = 1.51 mmol·dm–3, b = 1.15 mmol·kg–1) and
in 2,2,2-trifluoroethanol (c = 3.28 mmol·dm–3, b = 2.39 mmol·kg–1).
Catalytic dehydrocoupling of H3B·NMe2H using the in situ system Cp2Zr(Cl)(µ-Me3SiC3SiMe3)Zr(Cl)Cp2 (1)/MeLi was studied as a model for previously reported dehydropolymerisation of H3B·NMeH2. NMR and UV-Vis spectroscopic monitoring of the precatalyst...
Different types of cationic Rh complexes bearing the Synphos ligand were characterized by NMR and X‐ray analysis for the first time. This set of compounds includes diolefin rhodium precursors [Rh(Synphos)(cod)]BF4 and [Rh(Synphos)(nbd)]BF4, solvate complexes [Rh(Synphos)(MeOH)2]BF4, [Rh(Synphos)(acetone)2]BF4 as well as the toluene complex [Rh(Synphos)(toluene)]BF4, trinuclear complexes [Rh3(Synphos)3(μ3‐OH)2]BF4 and [Rh3(Synphos)3(μ3‐Cl)2]BF4 and arene‐bridged dimer [Rh2(Synphos)2](BF4)2.
The stepwise in situ formation of neutral μ 2 -chloro-bridged dinuclear (diphosphine)rhodium complexes of the type [{Rh(PP)(μ 2 -Cl)} 2 ] (PP = chelating diphosphine) following the reaction of [{Rh(COD)(μ 2 -Cl)} 2 ] (COD = cyclooctadiene) with the ligands BINAP, SegPhos, DM-SegPhos and DiFluorPhos was investigated quantitatively by stopped-flow UV/Vis spectroscopy at 25.0°C. The second-order rate constants of each step of the consecutive reactions were determined. The investigations were hindered by an unexpected equilibrium [a]
Cationic rhodium(I) diphosphine complexes, referred to as Schrock-Osborn catalysts, are privileged homogeneous catalysts with a wide range of catalytic applications. The coordination of solvent molecules can have a significant influence...
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