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

Abstract

A series of nickelacyclic carboxylates of the general formula [Ni(CH2CH2COO)(L2)] with p‐substituted pyridine ligands (2: L = 4‐picoline; 3: L = 4‐MeO2C‐C4H4N; 4: 4‐Me2N‐C4H4N) was synthesized and characterized by NMR spectroscopy. A correlation between the shift of the CH2 groups of the nickelacycle in the 1H NMR spectra and basicity of the used pyridine ligand was observed. Furthermore, amino‐substituted pyridine derivatives were used in ligand‐exchange reactions leading to supramolecular assemblies via H‐bond formation between the amino function and the carboxylate group. Depending on the ligand used, discrete dimers [5: L2 = (tBu)(Me)2Si‐aminomethylpyridine], chains [6: L2 = 2‐(aminomethyl)pyridine] or layers (7: L = 4‐H2N‐C4H4N) were observed. The molecular structures of all new compounds 2–7 were determined by X‐ray measurement.

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.…”

Nickelalactones with an allyl subunit – the effect of penta-coordination on structures and stability

“…This finding underlines that the derivatives under investigation are rather stable against protolysis in agreement with the results obtained for related derivatives of the type [(L) n Ni(CH 2 CH 2 COO)] which also form stable hydrogen bonds with alcohols 8c,15,17 and amines. 18 The molecular structure of 4•MeOH is shown in Fig. 4.…”

“…H atoms are omitted for clarity. Selected bond lengths (Å): Ni1-C3 2.215(5), Ni1-C4 2.031(5), Ni1-C5 1.991(5), Ni1-O1 2.106(3), Ni1-P1 2.0968(12), Ni1-N1 1.977(4), O1-C1 1.266(5), O2-C1 1.248(5), C1-C2 1.532(7), C2-C3 1.527(7), C3-C4 1.377(7), C3-C6 1.526(8), C4-C5 1.441(7), C4-C7 1.507(7); angles (°): P1-Ni1-N1 84.27(11), P1-Ni1-O1 122.47(10), P1-Ni1-C3 151.78(14), P1-Ni1-C4 115.58(15), P1-Ni1-C5 94.28(16), N1-Ni1-O1 92.90(14), N1-Ni1-C3 107.25(19), N1-Ni1-C4 129.19(19), N1-Ni1-C5 168.7(2), O1-Ni1-C3 84.41(16), O1-Ni1-C4 110.14(17), O1-Ni1-C5 97.29(18), C3-Ni1-C4 37.5(2), C3-Ni1-C5 69.3(2), C4-Ni1-C5 42.0(2), C3-C4-C5 116.7(5).…”

A Mechanistic Study of Ni‐catalyzed Carbon Dioxide Coupling with Ethylene towards the Manufacture of Acrylic Acid

“…[13] The oxidative coupling of CO 2 and ethylene catalyzed by homogeneous transition metal complexes of titanium, iron, nickel, rhodium, molybdenum, and tungsten shows promise for the development of green processes for production of acrylic acid. [14][15][16][17][18][19][20][21][22][23][24][25]…”