Hofmann-type clathrate

Hofmann- and Werner-Type Inclusion Compounds. There is a wide range of clathrates having as the host component inorganic coordination compounds represented by the general formulae M(NH3)2 M (CN)4 and M" X2Y4. The first formula is typical of Hofmann-type clathrates... 

The chemistry of inclusion compounds also looks back on a lively history There are many events of significance in the area of inclusion chemistry till the middle of the twentieth century including the discovery of new inclusion compounds and hosts (Fig. 1), among them the graphite intercalates, the P-quinol and cyclodextrin inclusion compounds, the Hofmann-type clathrates as well as the inclusion compounds of tri-o-thymotide, Dianin s compound, the choleic acids, of phenols, of urea and others specified in comprehensive monographs... 

A number of compounds with chemical compositions that are similar to that of the original Hofmann-type clathrates were reported. However, as usual for other inclusion compounds, similarity in composition does not necessarily co relate with similarity of structure. For example, in the [Cd(pn)Ni(CN)4] G series with aliphatic guests, the host structure is entirely different from the Hofmann-pn-type pyrrole clathrate [Cd(pn)Ni(CN)4]. (3/ 2)C4H5N. Two subseries of structures were observed for the channel cavities, one being a snake-like extension similar to chat observed for the urea-host inclusion... 

Concepts in Crystal Engineering, p. 319 Crystal Engineering with Hydrogen Bonds, p. 357 Crystal Structure Prediction, p. 371 Cfystalline Microporous Silicas, p. 380 Dye Inclusion Crystals, p. 497 Hofmann-Type Clathrates, p. 645 Mineralomimetic Structures, p. 868 Molecular Squares, Boxes, and Cubes, p. 909 Organic Zeolites, p. 996 Soft/Smart Materials, p. 1302... 

Chemical Topology, p. 229 Concepts in Crystal Engineering, p. 2 9 Crystalline Microporous Silicas, p. 380 Hofmann-Type Clathrates, p. 645 Interpenetration, p. 135... 

Hofmann-type clathrates Werner clathrates clathrate hydrates inclusion compounds of urea, thiourea, and selenourea cyclodextrins calixarenes gossypol hexa-hosts hydroquinone phenol and Dianin s compounds graphite intercalates natural and pillared clays and others. Such studies contributed to the birth of supramolecular chemistry, with relevance to a new understanding of the world of materials that was emphasized with a Nobel Prize. 

Nishikiori. S. Ratcliffe, C.I. Ripmeester, J.A. " Cd NMR studies of Hofmann type clathrates and related compounds ... 

Figure 2 Crystal structure for one Hofmann-type clathrate. (a) Single 2D periodic layer outlining the square planar Ni(CN)4 and the octahedral Fe(CN)4(NH3)2. (b) Benzene guest molecules (highlighted in orange) are enclathrated by the 2D layers. Fe (red), Ni (green), C (gray), and N (blue).

Hofmann-type clathrates have the general chemical formula M(NH3)2M (CN)4 2G, usually abbreviated as M-M -G [61]. M (Ni, Fe, Co, Cd) is a six-coordinated and M (Ni, Pt, Pd) is a four-coordinated divalent metal ion. The guest molecule is mostly an aromatic molecule (benzene, aniline, pyrrole). 

Abstract. The infrared spectra of M(4,4 -bipyridyl)Ni(CN)t complexes (M = Ni or Cd) and their dioxane, benzene, toluene, aniline and V,V-dimethylaniline clathrates are reported. Additional information regarding the structure of the host lattice is obtained from the Raman spectra of the M=Cd complex. It is shown that the structure of the host lattice consists of infinite polymeric layers of M-Ni(CN)i analogous to those of Hofmann type clathrates that have tetragonal symmetry. Bidentate 4,4 -bipyridyl molecules form bridges between the metal atoms M in the adjacent M-Ni(CN)4 oo layers. It is found that the 4,4 -bipyridyl molecules are centrosymmetric in this structure. 

The vibrational wavenumbers of the Ni(CN)4 group vibrations of the M-Ni-bipy complexes and M-Ni-bipy-G clathrates [G=Toluene, aniline or JV,A -dimethyl-aniline] are given in Table I. The v(CN) and 6(NiCN) vibrational wave-numbers are found to be similar to those of Hofmann type clathrates [6] and the pyridine [7] complex, showing that the M-Ni(CN)4 layers have been preserved. Since we observed only one v(CN) (E ) band in the IR spectrum and the other two v(CN) (4ig and 5i ) bands in the Raman spectrum of the Cd-Ni-bipy complex, we propose a square planar environment around the tetracyanonickelate ion. 

Fig. 1 A view of Hofmann-type benzene clathrate [M(NH3)2-MXCN)4]-2C6H6 diamminemetalM(II) (right upper) and tetracyanometallateM (n) (right lower) as building blocks of the host.

So-called Werner clathrates are another prominent series of clathrate compounds formed between a metal complex host and an aromatic guest molecule. The name Werner originates from A. Werner, who established the coordination theory of metal complex compounds. The host of the series has a general formula [M(NCS)2(4-Mepy)4], and in fact, the series is obtained conceptually by replacement of C N and NH3 in the Hofmann-type host by SCN and 4-Mepy (4-methylpyridine), respectively. This was done in order to increase the inclusion capability for bulkier substituted aromatic molecules, in particular, those related to the petroleum industry. 

Kitazawa, T. Sato. Y. Gomi. Y. Takahashi. M. Takeda, M. Crystal structure and Mdssbauer spectra of Hofmann-type pyrrole clathrate, Fe(NH3)2Ni(CN)4 2C4H5N. Mol. Cryst. Liq. Cryst. Sci. Technol. Sect A 1996,286.431-436. 

While Wemer complexes are based on discrete coordination complexes, another type of coordination compound with a distinctive extension into 2D layers through utilization of ditopic bidentate ligands was developed and first reported by K. A. Hofmann in 1897, Ni(NH3)2Ni(CN)4 2(C6H6). Hofmann-type compounds also exhibit inclusion properties of suitably sized guest molecules. Iwamoto and coworkers prepared a number of derivatives of Hofmann clathrates (Figure 2). 

THREE-DIMENSIONAL METAL COMPLEX HOSTS BUILT OF a, a)-(LONG-CARBON-CHAIN)-DIAMINOALKANE LIGAND BRIDGING TWO-DIMENSIONAL CYANOMETAL COMPLEX NETWORK HOFMANN-DIAMINOALKANE-TYPE CLATHRATES... 

We have been developing systematically the chemistry of Hofmann-type and related clathrate compounds. Several modifications of the metal complex host structures have been derived from that of the Hofmann-type by replacing the ammine ligands by amines or diamines, and/or the square-planar tetracyanometallate by tetrahedral one [1]. However, their structures were substantially similar to that of the Hofmann-type the volume of cavity was barely large enough to accommodate such small aromatic molecule as those enclathrated in the Hofmann-type host. 

Recently three-dimensional metal complex hosts have been developed from the two-dimensional Hofmann type host lattices, M(NH3)2Ni(CN)4, by replacing the ammonia groups by bidentate ligands, with the aim of enlarging the range of guest molecules which can be accommodated in the host lattices [1-5]. In a previous study Mathey et al. reported the preparation of the Ni(4,4 -bipyridyl)Ni(CN)4 host lattice and its benzene, xylene, naphthalene and anthracene clathrates [5]. We have extended this study and prepared M(4,4 -bipyridyl)Ni(CN)4-2G (M = Ni or Cd G = dioxane, toluene, aniline or iV,AT-dimethylaniline) clathrates for the first time. In this study an IR spectroscopic study of the M(4,4 -bipy)Ni(CN)4 -MG compounds (where M = Ni or Cd, G = dioxane, benzene, toluene, aniline or iV,AT-dimethylaniline, n=0-2) (abbreviated henceforth as M-Ni-bipy-G) are reported. Additional information is obtained from the laser-Raman spectrum of the Cd-Ni-bipy complex. We also recorded the powder X-ray diffraction patterns of the M-Ni-bipy complexes. 

Iwamoto, T., S-I. Nishikiori and T. Hasegawa - Hofmann diaminoalkane-type clathrates Iwamoto. T. - See Lipkowski, J. 

Classifying particles, in filtration, 11 326 Class I hybrids, 13 536, 543, 544 Class II hybrids, 13 536, 543 Clastogenesis, 25 206 Clathrate hydrates, 14 170—171 Clathrate receptor chemistry, 16 797 Clathrates, 12 374 14 159, 170-182 formation of, 10 633-635 26 869 Hofmann- and Werner-type, 14 171-172 phenol-type, 14 180 tri-o-thymotide, 14 179 Claus catalysts... 

The host metal complex has the three-dimensional structure consisting of the two-dimensionally extended cyanometal complex sheets and of the 1,4-diaminobutane ligands bridging adjacent sheets at the respective Cd atoms in the sheets. The Cd atoms are alternately linked with the square-planar Ni(CN)i moieties at the N-ends at each Cd-N junction the metal complex network bends to give a wavy structure of the sheet similar to those observed for Hofmann-mea-type pyrrole clathrate [14] and Hofmann-dma-type ones [8,9]. 1,4-Diaminobutane takes a trans-cis conformation of its N(3)-C(3)-C(4)-C(5)-C(6)-N(4) skeleton on the mirror plane at y=l/4 except the C(5) which is distributed statistically at both sides of the mirror plane the positions of hydrogen atoms attached to C(4) and C(6) atoms have been calculated in relation to both the... 

During the research work on these clathrate compounds we discovered a rare case of conversion from an apparently more stable coordination complex to a less stable clathrate compound for the Hofmann-dahxn-type series. The -toluidine compound obtained under the experimental conditions similar to those for the - and the m -toluidine clathrates was not a clathrate but a coordination complex [Cd( -CH3C6Hi NH2) 2 (dahxn)][Ni(CN)if], which turned to a clathrate Cd(dahxn)Ni(CN)... 

Another notable fact is the accommodation of an aliphatic guest molecule in the Hofmann-daotn-type host (daotn = 1,8-diaminooctane).. After screening more than thirty kinds of aliphatic molecules against the Hofmann-diam-type hosts, the Hofmann-daotn-type n -hexanol clathrate was obtained. The guest is accommodated with the orientation of the aliphatic chain parallel to the all-trans daotn bridge in the host. The structure can be seen as a model of pillared intercalation compound for which few single crystal data have been available. 

A phase transition probably to a superlattice structure has been observed for Hofmann-dahxn-type -toluidine clathrate at 200 K. Above this temperature the atomic temperature factors of the guest molecule increase steeply to suggest that the librational motion of the guest molecule is excited thermally. The details of the phase transition is still unknown, although it should be related to motion of the guest molecule. 

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