97921-19-2Relevant academic research and scientific papers
New nickel-containing homogeneous hydrogenation catalysts structures of [Ni(o-MeO-dpppol)Cl2] and [Ni(dcpe)Cl2]
Angulo, Ingrid M.,Bouwman, Elisabeth,Van Gorkum, Remy,Lok, Sandra M.,Lutz, Martin,Spek, Anthony L.
, p. 97 - 106 (2008/10/08)
The didentate phosphane ligands 1,3-bis(di(ortho-methoxyphenyl)phosphanyl)-2-propanol (o-MeO-dpppol) and 1,2bis(dicyclohexylphosphanyl)ethane (dcpe) have been used in a study towards catalytic hydrogenation using homogeneous nickel catalysts. The nickel halide complexes [Ni(o-MeO-dpppol)X2] and [Ni(dcpe)X2] (X = Cl, Br or I) have been synthesized and were characterized using electronic absorption and IR spectroscopy. The structures of the complexes [Ni(o-MeO-dpppol)Cl2] and [Ni(dcpe)Cl2] have been determined by X-ray crystallography. The nickel ions in these complexes are in (distorted) square-planar geometries with NiP2Cl2 chromophores. The synthesized halide complexes and in situ mixtures of nickel acetate and the ligands were tested on catalytic activity in homogeneous hydrogenation. The ligand dcpe yields very active catalysts; turnover numbers up to 3000 in 1 h have been obtained. Generally, it appeared that the catalytic activities are higher in methanol than in methanol/dichloromethane mixtures. It was found that the catalytic activities observed for complexes containing the ligand o-MeO-dpppol are less reproducible than those of catalysts with the ligand dcpe. This lower reproducibility is probably related to the fact that the former ligand is more readily oxidized.
Synthesis and single-crystal X-ray study of the mononuclear η2-benzyne (dehydrobenzene) nickel(0) complex Ni(η2-C6H4)((C6H 11)2PCH2CH2P(C6H 11)2). Insertion reactions with simple molecules and X-ray crystal structure of the ...
Bennett, Martin A.,Hambley, Trevor W.,Roberts, Nicholas K.,Robertson, Glen B.
, p. 1992 - 2000 (2008/10/08)
Full title: Synthesis and single-crystal X-ray study of the mononuclear η2-benzyne (dehydrobenzene) nickel(0) complex Ni(η2-C6H4)((C6H 11)2PCH2CH2P(C6H 11)2). Insertion reactions with simple molecules and X-ray crystal structure of the nickelaindan complex Ni(CH2CH2C6H4-o)((C 6H11)2PCH2CH2P(C 6H11)2). Sodium amalgam reduction of NiCl(C6H4Br-2)(Cy2PCH2CH 2PCy2)·0.5THF (6) (Cy = cyclohexyl, C6H11) gives a mononuclear nickel(0) complex, Ni(η2-C6H4)(Cy2PCH 2CH2PCy2) (3), which has been characterized by microanalysis, by mass, infrared, and NMR (1H, 13C, 31P) spectroscopy, and by single-crystal X-ray structural analysis. Crystals of 3 are orthorhombic, space group Pbca, with a = 16.068 (1) A?, b = 17.189 (1) A?, c = 22.358 (1) A?, and Z = 8. The structure was solved by heavy-atom methods and refined by least-squares methods to R = 0.035 and Rw = 0.055 for 4203 independent reflections. The molecule consists of a central nickel atom coordinated by a symmetric η2-benzyne ligand [Ni-C(1) = 1.870 (4) A?, Ni-C(2) = 1.868 (4) A?], the coordination geometry being close to trigonal planar. The coordinated C-C bond length of 1.332 (6) A? is significantly larger than those observed in alkyne complexes of zerovalent nickel and platinum. The remaining C-C bonds of the six-membered ring are almost equal in length (average 1.385 A?), consistent with a delocalized aromatic structure for the benzyne ligand. Complex 3 reacts with iodine and methyl iodide at room temperature to give, respectively, the 2-iodophenyl and o-tolyl complexes NiI(C6H4Y-2)(Cy2PCH2CH 2PCy2) (Y = I (7), Me (8)). Carbon dioxide, ethylene, and dimethyl acetylenedicarboxylate insert into the nickel-benzyne bond of 3 to give the nickelacycles Ni(C6H4COO)(Cy2PCH2CH 2PCy2) (10), Ni(CH2CH2C6H4-o)(Cy 2PCH2CH2PCy2) (11), and Ni(C(CO2Me)=C(CO2Me)C6H4-o)(Cy 2PCH2CH2PCy2) (12), respectively, whereas diphenylacetylene displaces benzyne to give Ni(PhC≡CPh)(Cy2PCH2CH2PCy2) (13). Crystals of 11 are monoclinic, space group P21/n, with a = 15.792 (6) A?, b = 17.471 (6) A?, c = 12.104 (4) A?, β = 104.09 (2)°, and Z = 4. The structure was solved and refined as for 3 to R = 0.070 and Rw = 0.071 for 2379 independent reflections. The nickel atom is coordinated in an approximately planar arrangement by the bidentate di(tertiary phosphine) and by two carbon atoms of a five-membered, half-chair-shaped chelate ring, the Ni-C(aryl) and Ni-C(alkyl) bond lengths being 1.951 (12) and 1.988 (12) A?, respectively.
