Studies on werner clathrates. Part 131. Selective criteria in werner clathrates. Six crystal structures with bis(isothiocyanato)tetra(4-vinylpyridine)nickel(II) as host |
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| Authors: | Laurence Lavelle Luigi R Nassimbeni |
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| Institution: | (1) Department of Physical Chemistry, University of Cape Town, 7700 Rondebosch, South Africa;(2) Present address: Department of Chemistry, Princeton University, 08544 Princeton, New Jersey, USA |
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| Abstract: | This paper addresses the general question: what are the significant guest properties selected by this host when interacting with guest molecules in the liquid phase, resulting in cocrystallization of the host and guest? In particular, to what extent do π electrons in a guest molecule effect its potential as a guest? Werner clathrates of the host Ni(NCS)2(4-ViPy)4] with mixtures of tetrahydrofuran (THF) and cyclic hydrocarbons as guests have been synthesised and their structures elucidated. Clathrate (1): Ni(NCS)2(4-ViPy)4](1.78 THF)(0.22 cyclohexane), crystallizes in the orthorhombic space groupP bcn a=9.976(6),b=20.630(25),c=19.861 (4) Å,V=4087Å3,Z=4,R=0.087 for 1461 reflections; (2): Ni(NCS)2(4-ViPy)4](1.76 THF)(0.24 cyclohexene),P bcn ,a=9.987(7),b=20.614(4),c=19.898(4)Å,V=4096Å3,Z=4,R=0.084 for 1304 reflections; (3): Ni(NCS)2(4-ViPy)4](0.48 THF)(0.52 1,3-cyclohexadiene), tetragonalI41/a,a=16.898(3),b=16.898(3),c=26.463(6)Å,V=7556Å3,Z=8,R=0.120 for 1698 reflections; (4): Ni(NCS)2(4-ViPy)4](0.36 THF)(1.04 1,4-cyclohexadiene),I41/a,a=16.986(4),b=16.986(4),c=25.896(15)Å,V=7472Å3,Z=8,R=0.103 for 2025 reflections; (5): Ni(NCS)2(4-ViPy)4](0.35 THF)(1.05 benzene),I41/a,a=17.102(10),b=17.102(10),c=25.498(8)Å,V=7458Å3,Z=8,R=0.118 for 2200 reflections; (6): Ni(NCS)2(4-ViPy)4](3 benzene), triclinicP1,a=10.432(24),b=11.155(9),c=21.581(7)Å, α=78.70(5), β=82.60(7), γ=74.09(13)°,V=2361Å3,Z=2,R=0.078 for 3427 reflections. Host-guest ratios and, for mixtures of guests, guest1/guest2 ratios, were elucidated by density and NMR. We show that the conformational freedom of the substituted pyridines is not the primary reason for the clathrating ability of Werner hosts. All six structures show no host-guest interaction at the level of van der Waals interactions. As non-bonding interactions are not observed between the host and guest, this study shows that the above host's selectivity by enclathration of particular guest molecules cannot be accounted for by solid state structural analysis. |
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| Keywords: | Werner clathrate nickel octahedral complex tetrahydrofuran crystal structure NMR molecular recognition hydrocarbon |
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