In-plane and Out-of-plane Motion of Benzene Trapped in a Cd(py)2{Ag(CN)2}2 Host as Studied by Deuterium NMR

2H-NMR powder patterns of the deuterated benzene molecule trapped in a Cd(py)2{Ag(CN)2}2 host were measured in the temperature range of 123-403 K in order to obtain information about motional behavior of the guest benzene molecule undergoing an in-plane motion combined with an out-of-plane motion. The activation energy for the in-plane motion, which is a 60° jump among neighboring sites on the benzene ring, was derived to be 18.2(5) kJ mol-1 from the line-shape simulation of the 2H-NMR powder patterns. The jump frequency of the out-of-plane motion, which is a reorientation of the benzene ring between two sites separated with a 57.8° azimuthal angle, was in a fast motion region even at 123 K and the activation energy of the two-site jump is very low compared with that of the in-plane motion.     

Orientation of guest benzene molecules in Hofmann-type and related clathrates by molecular mechanics calculation

Molecular mechanics calculations were carried out to interpret the observed orientational angle of the benzene molecule enclathrated in the Hofmann-type M(NH₃)₂Ni(CN)₄·2 C₆H₆ (M = Mn, Ni, Cu, and Cd), Hofmann-en-type Cd(en)Ni(CN)₄·2 C₆H₆ (en = NH₂CH₂CH₂NH₂), and Hofmannmea-type(2) Cd(mea)Ni(CN)₄·2 C₆H₆ (mea = NH₂CH₂CH₂OH) clathrates using the van der Waals potential functions in Molecular Mechanics Version 2. The angle is most influenced by the guest-to-guest contact in the interlayer space between the two-dimensionalcatena-[metal(II) tetra--cyanonickelate(II)] networks for the Hofmann-type series. The discrepancy between the calculated and the observed angles in each crystal structure was at largest 3.5°; the structures of Cd(NH₃)₂Ni(CN)₄·2 C₆H₆ and Cd(en)Ni(CN)₄·2 C₆H₆ have been revised using new data collected by counter-methods.     

Thermoanalytical investigation of the guest-release process in aromatic-guest clathrates of three-dimensional metal complex hosts

The guest-release process was investigated in terms of the activation energy evaluated by thermogravimetry for the en-Td-type clathratescatena--[catena--(ethylenediamine)cadmium(II) tetra--cyanocadmate(II) or -mercurate(II)]-benzene(1/2), -benzene-d ₆(1/2), and -pyrrole(1/2), the Hofmannen-type clathratescatena-[catena--(ethylenediamine)cadmium(II) tetra--cyanonickelate(Il)]-benzene (1/2) and -pyrrole(1/2), the Hofmann-pn-type clathratecatena-[catena--(dl- orl-propylenediamine (cadmium(II) tetra--cyanonickelate(II)]-pyrrole(2/3), and the pn-Td-type clathratescatena-[catena--(dl-propylenediamine) or -(l-propylenediamine)cadmium(II) tetra--cyanocadmate(II)]-benzene(2/3). Values of the activation energy are correlated with the structural change in the metal complex host accompanied by the release of the guest molecules. The crystal structure ofcatena-[ethylenediaminecadmium tetra--cyanonickelate(II)], the residual host of the Hofmann-en-type, has been analyzed to elucidate the correlation.     

Accommodation of an aliphatic guest molecule in hofmann-diaminooctane-type host. A model structure of a pillared intercalation compound

catena-[catena--(1,8-Diaminooctane)cadmium(II) tetra--cyanonickelate(II)]-(1-hexanol)(1/1) has been prepared as the first example of an aliphatic guest clathrate of the Hofmann-type and analogous metal complex hosts. The clathrate crystallizes in the monoclinic space groupP2/m,a=11.470(2),b=7.782(1), andc=6.945(1) Å, =105.29(1)°,Z=1;R=0.043 for 1865 reflections. The structure presents a model of pillared intercalation compounds formed between layers of metal complex sheets pillared by ,-ambidentaten-alkaneskeletal ligands andn-alkyl derivative guests. Supplementary Data relating to this article are deposited with the British Library as supplementary publication SUP 82069 (16 pages).     

Past,present and future of the clathrate inclusion compounds built of cyanometallate hosts

One-, two- and three-dimensional CN-bridged metal complex structures made up of building blocks such as linear [Ag(CN)₂]^–, square planar [Ni(CN)₄]^2– or tetrahedral [Cd(CN)₄]^2–, and of the complementary ligands such as ammonia, water, unidentate amine, bidentate a,w- diaminoalkane, etc., are reviewed with an emphasis on their behaviour as hosts to afford clathrate inclusion compounds with guest molecules and as self-assemblies to form supramolecular structures with or without guests. The historical background is explained for Prussian blue and Hofmann's benzene clathrate based on their single crystal structure determinations. The strategies the author and coworkers have been applying to develop varieties of clathrate inclusion compounds from the Hofmann-type are demonstrated with the features observed for the developed structures determined by single crystal X-ray diffraction methods.Abbreviations for Ligands and Guests mma NMeH₂ - dma NMe₂H - tma NMe₃ - mea NH₂(CH₂)₂OH - en NH₂(CH₂)₂NH₂ - pn NH₂CHMeCH₂NH₂ - tn NH₂(CH₂)₃NH₂ - dabtn NH₂(CH₂)₄NH₂ - daptn NH₂(CH₂)₅NH₂ - dahxn NH₂(CH₂)₆NH₂ - dahpn NH₂(CH₂)₇NH₂ - daotn NH₂(CH₂)₈NH₂ - danon NH₂(CH₂)₉NH₂ - dadcn NH₂(CH₂)₁₀NH₂ - mtn NMeH(CH₂)₃NH₂ - dmtn NMe₂(CH₂)₃NH₂ - detn NEt₂(CH₂)₃NH₂ - temtn NMe₂(CH₂)₃NMe₂ - dien NH₂(CH₂)₂NH(CH₂)₂NH₂ - pXdam p-C₆H₄(NH₂CH₂)₂ - rnXdam m-C₆H₄(NH₂CH₂)₂ - py C₅H₅N pyridine - ampy NH₂C₅H₄N aminopyridine - Clpy CIC₅H₄N chloropyridine - Mepy MeC₅H₄N methylpyridine - dmpy Me₂C₅H₃N dimethylpyridine - bpy NC₅H₄C₅H₄N bipyridine - quin C₇H₉N quinoline - iquin iso-C₇H₉N isoquinoline - qxln C₈H₆N₂ quinoxaline - Pe C₅H₁₁-pentyl imH: C₃N₂H₄ imidazole - pyrz N(CHCH)₂N pyrazine - Mequin MeC₇H₈N methylquinoline - bppn C₁₃H₁₄N₂ 1,3-bis(4-pyridyl)propane - bpb C₁₄H₈N₂ 1,4-bis(4-pyridyl)butadiyne - N-Meim C₃N₂H₃Me N-methylimidazole - 2-MeimH C₃N₂H₃Me 2-methylimidazole - dmf HOCNMe₂ dimethylformamide - hmta C₆H₁₂N₄ hexamethylenetetramine - o-phen C₁₂H₈N₂ 1,10-phenanthroline - den HN(CH₂CH₂)₂NH piperazine - morph HN(CH₂CH₂)₂O morpholine - ten N(CH₂CH₂)₃N 1,4-diazabicyclo[2.2.2]octane - ameden NH₂(CH₂)₂N(CH₂CH₂)₂NH N-(2-aminoethyl)piperazine Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Recent developments in the chemistry of hofmann-type and the analogous clathrates

Based on the structural features of Hofmann-type clathraces M(NH₃)₂M'(CN)₄ · 2G (M = a divalent metal in six-coordination, M' = a divalent metal in square-planar coordination, G = a small aromatic guest molecule), several series of the analogous clathrates have been derived by appropriate replacements of the host moieties. These clathrates are designated with a general formula Cd (diam)M'(CN)₄ ·$\text{n}$G where diam refers to diammine, an ambident diamine or monoethanolamine (mea), or a pair of unidencate mea's, M'(CN)₄ is a square-planar or a tetrahedral tetracyanometallate(II), and G is a small aromatic guest molecule. The number of guest molecules, $\text{n}$, varies stepwise from 2 through $\text{3}\text{2}$ to 1 depending on the bulkiness of diam ligand which builds up the host structure. Their structural features are discussed on the two- and three-dimensional networks of the metal complex hosts. The historical background is also reviewed briefly.     

Calorimetric and thermogravimetric study of competitive clathration in theβ-[Ni(NCS)2(4-McPy)4] host

The stoichiometry of mixed guest clathrates of [Ni(NCS)₂(4-methylpyridine)₄] (host) with methanol/4-methylpyridine and acetone/4-methylpyridine as well as the enthalpies of clathration and the thermokinetic course of the processes were investigated. Two different mechanisms of molecular inclusion are proposed: (I) simple competition for the same type of absorption sites with two methanol molecules substituting one of 4-methylpyridine in the solid inclusion compound; and (II) competitive absorption for two types of absorption sites of acetone and 4-methylpyridine. Partial molar enthalpies of clathration of the individual guests are derived and discussed. The thermokinetic course of the processes is also given. The analytical thermogravimetric procedure is described and the solid products of thermal decomposition of the clathrates and of the host complex were identified by using X-ray powder diffractometry.Presented at the International Seminar on Inclusion Compounds, Jaszowiec, Poland, 24–26 September 1987.