Saturated and unsaturated nickelalactones with N-heterocyclic carbene ligands: Synthesis and structures

Acrylates from Alkenes and CO2, the Stuff That Dreams Are Made of

“…In a systematic study of the oxidative coupling of ethylene and CO 2 with Ni(COD) 2 as a Ni(0)-precursor and bidentate phosphines bearing either phenyl-or tert-butyl substituents at the phosphorus atoms and differing in the length of the carbon bridge -CH 2 (CH 2 ) n -in the ligand backbone (n ¼ 0-2), we observed the following trends ( Fig. 3A): (1) Sterically, nondemanding bidentate ligands as bis(diphenylphosphino) methane (dppm) or certain monodentate ligands form aggregated complexes (e.g., dimers, trimers), as already discussed by Langer and Walther et al, [40][41][42][43][44] and (2) the higher homologues of dppm, such as 1,2-bis (diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp), rapidly form the corresponding known tetracoordinate Ni(0) species Ni(dppe) 2 45 and Ni(dppp) 2 instead of the expected lactones [Ni ((CH 2 ) 2 CO 2 )(dppe)] and [Ni((CH 2 ) 2 CO 2 )(dppp)]. 46 This does not at all mean that those ligands do not form catalytically active species (as has been shown later), but for our first systematic studies they turned out to be "difficult" for the mentioned reasons.…”

Nickel N-heterocyclic carbene complexes and their utility in homogeneous catalysis

“…The other examples of the oxidation method include the (151), [54] (155−157), [58] (161) [73] and (162) [75] complexes ( Figure 13). …”

“…Lastly, the complexes (149−150), [64] (152), [76] (153), [66] (154), [77] (158−159) [78] and (160) [73] were synthesized by the Fourth method (Scheme 16) from other Ni(II)−NHC complexes by the treatment with suitable reagents namely, AgOTf, TlSCPh 3 , oxygen, 2,6-lutidine, KPF 6 , HCl and K(acac) (Scheme 16 and Figure 14). …”

Nickelacyclic Carboxylates with Pyridine‐Based Ligand Sets – From Mononuclear Complexes to Supramolecular Architectures by Hydrogen Bonding

“…[14] By utilizing these complexes it was possible to greatly enhance the ligand pool available for stabilizing nickelacyclic carboxylates. Besides N-heterocyclic carbenes [15] and 1,2-diiminoethane derivatives, [16] monodentate phosphane li-gands can be introduced in nickelacyclic carboxylates, resulting in the ligand-driven self-assembly to oligomeric derivatives by formation of Ni-O-C=O-Ni or Ni-O-Ni bridges. [17] These interesting results encouraged us to undertake further investigations in the field of supramolecular organometallic chemistry.…”