Syntheses and properties of nickel(I) and nickel(II) complexes of a series of macrocyclic N4 ligands: Crystal structures of C-RSSR-[NiIHTIM](ClO4), C-RSSR-[NiIIHTIM](ClO4)2, C-RRSS-[NiIIHTIM](ClO4)2, and [NiIITIM](ClO4) ...

David J. Szalda, Etsuko Fujita, Ralf Sanzenbacher, Helmut Paulus, Horst Elias

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Abstract

Full title: Syntheses and properties of nickel(I) and nickel(II) complexes of a series of macrocyclic N4 ligands: Crystal structures of C-RSSR-[NiIHTIM](ClO4), C-RSSR-[NiIIHTIM](ClO4)2, C-RRSS-[NiIIHTIM](ClO4)2, and [NiIITIM](ClO4)2 (HTIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradecane, TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene). Two isomers of the square-planar nickel(II) complex of 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradecane (HTIM) were prepared from the nickel(II) complex of 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,-10-tetraene (TIM) by NaBH4 reduction in aqueous solution. The properties of Ni(II) complexes, Ni(I) complexes, and Ni(I)-CO complexes with a series of 14-membered macrocyclic N4 ligands were studied by means of UV-vis, NMR, and IR spectroscopy. The CO binding constants range from 1.3 × 102 to 2.8 × 105 M-1 at 25°C in acetonitrile. The crystal structures of C-RSSR-[NiIHTIM]ClO4 (1), C-RSSR-[NiIIHTIM](ClO4)2 (2), C-RRSS-[NiIIHTIM] (ClO4)2 (3) and [NiIITIM](ClO4)2 (4) have been determined from single-crystal X-ray diffraction data collected by using Mo Kα radiation. Crystallographic data are as follows: (1) trigonal space group R3 with a = 11.971(3) Å, α = 107.46(2)° , V = 1410.3(5) Å3, Z = 3; (2) triclinic space group P1 with a = 8.503(2) Å, b = 8.438(2) Å, c = 8.028(2) Å, α = 102.63(1)°, β = 104.81(1)°, γ= 101.76(1)°, V = 522.4(4) Å3, Z = 1; (3) monoclinic space group P21/c with a = 8.307(4) Å, b = 12.521(6) Å, c = 10.587(6) Å, β = 103.66(2)°, V = 1070(2) Å3, Z = 2; (4) orthorhombic space group Pnma with a = 13.189(2) Å, b = 11.672(2) Å, c = 13.757(3) Å, V = 2118(1) Å3, Z = 4. All complexes have square-planar geometry and the stereochemistry of the four coordinating N atoms in complexes (1), (2), and (3) is Trans III. Although the two sets of Ni-N distances of 2.083(3) and 2.053(3) Å for the Ni(I) complex, (1), are much longer than those of 1.969(1) and 1.948(2) Å for the corresponding Ni(II) complex, (2), distortion of the macrocycle core was not observed upon the reduction of the metal center. The structural changes associated with the reduction of Ni(II) to Ni(I) in square-planar complexes can be classified in three ways: (1) expansion of Ni-N distances; (2) distortion of nickel core; (3) both expansion and distortion.

Original languageEnglish
Pages (from-to)5855-5863
Number of pages9
JournalInorganic Chemistry
Volume33
Issue number25
Publication statusPublished - 1994

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ASJC Scopus subject areas

  • Inorganic Chemistry

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