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Nickel(II) and Zinc(II) Dibenzoylmethanates: Molecular and Crystal Structure, Polymorphism, and Guest- or Temperature-Induced Oligomerization
Four forms of nickel(II) and two of zinc(II) dibenzoylmethanates have been isolated and characterized with powder and single-crystal X-ray diffraction analyses, differential scanning calorimetry, magnetic susceptibility measurements, and solid-state 13C cross-polarization/magic angle spinning NMR. N...
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Published in: | Inorganic chemistry 2001-03, Vol.40 (7), p.1626-1636 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
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Online Access: | Get full text |
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Summary: | Four forms of nickel(II) and two of zinc(II) dibenzoylmethanates have been isolated and characterized with powder and single-crystal X-ray diffraction analyses, differential scanning calorimetry, magnetic susceptibility measurements, and solid-state 13C cross-polarization/magic angle spinning NMR. Nickel dibenzoylmethanate, Ni(DBM)2 (DBM = PhCOCHCOPh-), forms three polymorphic forms (light-green, brown, and green) and a fourth clathrate form with guest benzene included. The light-green polymorph is metastable. Substituted benzenes induce recrystallization of the polymorph into a stable brown form (C30H22NiO4; a = 26.502(3) Å, b = 5.774(1) Å, c = 16.456(2) Å, β = 116.03(1)°; monoclinic, C2/c; Z = 4). Unlike the other forms, the brown form is diamagnetic and is comprised of monomers of the low-spin [Ni(DBM)2] complex. The Ni(II) is chelated by two DBM ligands in a square planar environment by four donor oxygen atoms. When heated, the brown form transforms to a green form which is stable above 202 °C (C90H66Ni3O12; a = 13.819(2) Å, b = 16.252(2) Å, c = 17.358(2) Å, β = 108.28(1)°; monoclinic, P21/n; Z = 2). This polymorph is formed by van der Waals packing of trimers [Ni3(DBM)6] containing linear Ni3 clusters with an Ni−Ni distance of 2.81 Å. The cluster is surrounded by six DBM ligands, providing a distorted octahedral environment about each Ni by six oxygen atoms. Benzene stabilizes the trimeric structure at room temperature, forming a [Ni3(DBM)6]·2(benzene) inclusion compound (Ni−Ni distance of 2.83 Å) with guest benzene molecules located in channels (C90H66Ni3O12 + 2(C6H6); a = 17.670(2) Å, b = 20.945(3) Å, c=11.209(2) Å, β = 102.57(1)°; monoclinic, P21/c; Z = 2). Zinc dibenzoylmethanate has been prepared in two polymorphic forms. The monomeric form contains [Zn(DBM)2] molecules with the zinc center in a distorted tetrahedral environment of four oxygens from the two chelated DBMs (C30H22O4Zn; a = 10.288(2) Å, b = 10.716(2) Å, c = 12.243(2) Å, α = 89.19(1)°, β = 75.39(1)°, γ = 64.18(1)°; triclinic, P 1̄; Z = 2). Another, dimeric form contains [Zn2(DBM)4] species, with two zinc atoms separated by a distance of 3.14 Å and each zinc coordinated by five oxygen atoms (C60H44O8Zn2; a = 25.792(3) Å, b = 7.274(1) Å, c = 24.307(2) Å, β = 90.58(1)°; monoclinic, C2/c; Z = 4). The polymorphic variety of the title complexes and the peculiarities of the Ni(II) and Zn(II) coordination environments are discussed in the context of using the complexes as precursors for new |
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ISSN: | 0020-1669 1520-510X |
DOI: | 10.1021/ic000981g |