Comparison of free and metal coordinated 1,4-disubstituted-1,4-diaza-1,3-butadienes : Crystal and molecular structures of 1,4-dicyclohexyl-1,4-diaza-1,3-butadiene and trans-[dichloro(triphenylphosphine)(1,4-di-tert-butyl- 1,4-diaza-1,3-butadiene)palladium(II)] |
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Authors: | Jan Keijsper Henk Van Der Poel Louis H. Polm Gerard Van Koten Kees Vrieze Paul F.A.B. Seignette Ronald Varenhorst Caspar Stam |
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Affiliation: | Anorganisch Chemisch Laboratorium, J. H. Van ''t Hoff Instituut, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands;Laboratorium voor Kristallografie, J. H. Van ''t Hoff Instituut, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands |
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Abstract: | The crystal and molecular structures of c-Hex-DAB (c-hexyl-NC(H)C(H)N-c-hexyl; DAB = 1,4-diaza-1,3-butadiene) and of trans-[PdCl2(PPh3)(t-Bu-DAB)] are reported. Crystals of c-Hex-DAB are monoclinic with space group C2/c and cell constants: a = 24.70(1), b = 4.660(2), c = 12.268(3)Å, β = 107.66(4)°, Z = 4. The molecule has a flat E-s-trans-E structure with bond lengths of 1.258(3)Å for the CN double bond and 1.457(3)Å for the central CC′ bond. These bond lengths and the NC-C′ angle of 120.8(2)° indicate that the C- and N-atoms are purely sp2-hybridized and that there is little or no conjugation within the central DAB skeleton. Crystals of trans-[PdCl2(PPh3)(t-Bu-DAB)] are triclinic with space group P-1 and cell constants: a = 17.122(3), b = 18.279(3), c = 10.008(5)Å, α = 96.77(2), β = 95.29(3), γ = 109.79(2). Z = 4. The t-Bu-DAB ligand is coordinated to the metal via one lone pair only. In this 2e; σ-N coordination mode the E-s-trans-E conformation of the free DAB-ligand is still present and the bonding distances within the DAB-ligand are hardly affected. [CN: 1.261(10)Å; CC′: 1.479(10)Å (mean).] The PdN-, NC- and central CC′-bond lengths are compared with those found in other metal -R-DAB complexes. |
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Keywords: | Author to whom correspondence should be addressed. |
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