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Octahedral cluster

January 01, 1970

Octahedral clusters are inorganic or organometallic cluster compounds composed of six metals in an octahedral array.[1] Many types of compounds are known, but all are synthetic.

Octahedral chalcogenide and halide clusters edit

These compounds are bound together by metal-metal bonding as well as two kinds of ligands. Ligands that span the faces or edges of the M6 core are labeled Li, for inner (innen in the original German description), and those ligands attached only to one metal are labeled outer, or La for ausser.[2] Typically, the outer ligands can be exchanged whereas the bridging ligands are more inert toward substitution.

Face-capped halide clusters edit

The premier example is of the class is Mo6Cl142−. This dianion is available as a variety of salts by treating the polymer molybdenum(II) chloride with sources of chloride, even hydrochloric acid. A related example is W6Cl142− anion, which is obtained by extraction of tungsten(II) chloride.

 
Structure of [M6Cl14]2− (M = Mo or W).

Chalcohalide clusters edit

A related class of octahedral clusters are of the type M6X8L6 where M is a metal usually of group 6 or group 7, X is a ligand and more specifically an inner ligand of the chalcohalide group such as chloride or sulfide and L is an "outer ligand." The metal atoms define the vertices of an octahedron. The overall point group symmetry is Oh. Each face of the octahedron is capped with a chalcohalide and eight such atoms are at the corners of a cube. For this reason this geometry is called a face capped octahedral cluster. Examples of this type of clusters are the Re6S8Cl64− anion.

Chevrel clusters edit

A well-studied class of solid-state compounds related to the chalcohalides are molybdenum clusters of the type AxMo6X8 with X sulfur or selenium and Ax an interstitial atom such as Pb. These materials, called Chevrel phases or Chevrel clusters, have been actively studied because they are type II superconductors with relatively high critical fields.[3] Such materials are prepared by high temperature (1100 °C) reactions of the chalcogen and Mo metal. Structurally related, soluble analogues have been prepared, e.g., Mo6S8(PEt3)6.[4]

Edge-Capped Halide Clusters edit

With metals in group 4 or 5 a so-called edge-capped octahedral clusters are more common. Twelve halides are located along the edge of the octahedron and six are terminal. Examples of this structure type are tungsten(III) chloride, Ta6Cl14(H2O)4,[5][6] Nb6F15, and Nb6F182−.[1]

 
Structure of edge-capped octahedral clusters such as Ta6Cl184−.[7]

Many of the early metal clusters can only be prepared when they incorporate interstitial atoms. One example is Zr6CCl12.[2]

Tin(II) clusters edit

Octahedral clusters of tin(II) have been observed in several solid state compounds. The reaction of tin(II) salts with an aqueous base leads to the formation of tin(II) oxyhydroxide (Sn6O4(OH)4), the structure of which comprises discrete Sn6O4(OH)4 clusters. In Sn6O4(OH)4 clusters, the six tin atoms form an octahedral array with alternate faces of the octahedron occupied by an oxide or hydroxide moiety, each bonded in a μ3-binding mode to three tin atoms.[8] Crystal structures have been reported for compounds with the formula Sn6O4(OR)4, where R is an alkoxide such as a methyl or ethyl group.[9][10]

Recently, it was demonstrated that anionic tin(II) clusters [Sn6O8]4- may form the close packed arrays as in the case of α-Sn6SiO8, which adopts the zinc blende structure, comprising a face-centred-cubic array of [Sn6O8]4- clusters with Si4+ occupying half of the tetrahedral holes.[11] A polymorph, β-Sn6SiO8, has been identified as a product of pewter corrosion in aqueous conditions, and is a structural analogue of wurtzite.[12]

Electron counting in octahedral halide and chalcogenide clusters edit

The species Mo6Cl142− feature Mo(II) (d4) centers. Six Mo(II) centers gives rise to a total of 24 valence electrons, or 2e/Mo-Mo vector. More electron-deficient derivatives such as Ta6Cl184− have fewer d-electrons. For example, the naked cluster Ta614+, the core of Ta6Cl184− would have 5(6) - 14 = 16 valence electrons. Fewer d-electrons result in weakened M-M bonding and the extended Ta---Ta distances accommodate doubly bridging halides.

Other classes of octahedral clusters edit

In the area of metal carbonyl clusters, a prototypical octahedral cluster is [Fe6C(CO)16]2−, which is obtained by heating iron pentacarbonyl with sodium. Some of the CO ligands are bridging and many are terminal. A carbide ligand resides at the center of the cluster. A variety of analogous compounds have been reported where some or all of the Fe centres are replaced by Ru, Mn and other metals.

Outside of carbonyl clusters, gold forms octahedral clusters.

 
The complex [Au6C(PPh3)6]2+, containing a carbon-gold core.

References edit

  1. ^ a b Eric J. Welch and Jeffrey R. Long Atomlike Building Units of Adjustable Character: Solid-State and Solution Routes to Manipulating Hexanuclear Transition Metal Chalcohalide Clusters in Progress in Inorganic Chemistry, Volume 54 Kenneth D. Karlin ISBN 0-471-72348-7 2005 Link
  2. ^ a b Arndt Simon "Metal clusters inside out" Phil. Trans. R. Soc. A 2010 vol. 368, 1285-1299. doi:10.1098/rsta.2009.0271
  3. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  4. ^ Saito, T. and Imoto, H., "Chalcogenide Cluster Complexes of Chromium, Molybdenum, Tungsten, and Rhenium", Bulletin Chemical Society of Japan, 1996, volume 69, pp. 2403-2417. doi:10.1246/bcsj.69.2403
  5. ^ Duraisamy, Thirumalai; Hay, Daniel N. T.; Messerle, Louis (2014). "Octahedral Hexatantalum Halide Clusters". Inorganic Syntheses: Volume 36. Vol. 36. pp. 1–8. doi:10.1002/9781118744994.ch1. ISBN 9781118744994.
  6. ^ Koknat, F. W.; Marko, D. J. "Tetradecachlorohexatantalum Octahydrate, Ta6Cl14.8H2O" Inorganic Syntheses, 2004, volume 34, pp. 187-191. ISBN 0-471-64750-0. (describes Na4Ta6Cl18)
  7. ^ Thaxton, C. B.; Jacobson, R. A. (1971). "The Crystal Structure of H2(Ta6Cl18)(H2O)6". Inorganic Chemistry. 10: 1460–1463. doi:10.1021/ic50101a029.
  8. ^ Abrahams, I.; Grimes, S. M.; Johnston, S. R.; Knowles, J. C. (1996-02-15). "Tin(II) Oxyhydroxide by X-ray Powder Diffraction". Acta Crystallographica Section C Crystal Structure Communications. 52 (2): 286–288. doi:10.1107/S0108270195012625.
  9. ^ Harrison, Philip G.; Haylett, Bernard J.; King, Trevor J. (1978). "X-Ray crystal structure of Sn6O4(OMe)4: an intermediate in the hydrolysis of tin(II) dimethoxide". Journal of the Chemical Society, Chemical Communications (3): 112–113. doi:10.1039/c39780000112. ISSN 0022-4936.
  10. ^ Suslova, E. V.; Turova, N. Ya.; Kessler, V. G.; Belokon’, A. I. (November 2007). "Electrosynthesis of tin(II) alkoxides". Russian Journal of Inorganic Chemistry. 52 (11): 1682–1686. doi:10.1134/S0036023607110083. ISSN 0036-0236. S2CID 93819431.
  11. ^ Parsons, Daniel S.; Savva, Savvaki N.; Tang, Wai Chi; Ingram, Andrew; Hriljac, Joseph A. (2019-12-16). "Sn 6 SiO 8 , a Tin(II) Silicate with a Zinc Blende Related Structure and High Thermal Stability". Inorganic Chemistry. 58 (24): 16313–16316. doi:10.1021/acs.inorgchem.9b02615. ISSN 0020-1669. PMID 31804067.
  12. ^ Locock, A. J.; Ramik, R. A.; Back, M. E. (2006-12-01). "THE STRUCTURES OF TWO NOVEL Sn2+ OXYSALTS FOUND WITH ROMARCHITE AND HYDROROMARCHITE AS CORROSION PRODUCTS OF PEWTER ARTIFACTS". The Canadian Mineralogist. 44 (6): 1457–1467. Bibcode:2006CaMin..44.1457L. doi:10.2113/gscanmin.44.6.1457. ISSN 0008-4476.

January 01, 1970
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Octahedral clusters are inorganic or organometallic cluster compounds composed of six metals in an octahedral array 1 Many types of compounds are known but all are synthetic Contents 1 Octahedral chalcogenide and halide clusters 1 1 Face capped halide clusters 1 2 Chalcohalide clusters 1 3 Chevrel clusters 1 4 Edge Capped Halide Clusters 1 5 Tin II clusters 2 Electron counting in octahedral halide and chalcogenide clusters 3 Other classes of octahedral clusters 4 ReferencesOctahedral chalcogenide and halide clusters editThese compounds are bound together by metal metal bonding as well as two kinds of ligands Ligands that span the faces or edges of the M6 core are labeled Li for inner innen in the original German description and those ligands attached only to one metal are labeled outer or La for ausser 2 Typically the outer ligands can be exchanged whereas the bridging ligands are more inert toward substitution Face capped halide clusters edit The premier example is of the class is Mo6Cl142 This dianion is available as a variety of salts by treating the polymer molybdenum II chloride with sources of chloride even hydrochloric acid A related example is W6Cl142 anion which is obtained by extraction of tungsten II chloride nbsp Structure of M6Cl14 2 M Mo or W Chalcohalide clusters edit A related class of octahedral clusters are of the type M6X8L6 where M is a metal usually of group 6 or group 7 X is a ligand and more specifically an inner ligand of the chalcohalide group such as chloride or sulfide and L is an outer ligand The metal atoms define the vertices of an octahedron The overall point group symmetry is Oh Each face of the octahedron is capped with a chalcohalide and eight such atoms are at the corners of a cube For this reason this geometry is called a face capped octahedral cluster Examples of this type of clusters are the Re6S8Cl64 anion Chevrel clusters edit A well studied class of solid state compounds related to the chalcohalides are molybdenum clusters of the type AxMo6X8 with X sulfur or selenium and Ax an interstitial atom such as Pb These materials called Chevrel phases or Chevrel clusters have been actively studied because they are type II superconductors with relatively high critical fields 3 Such materials are prepared by high temperature 1100 C reactions of the chalcogen and Mo metal Structurally related soluble analogues have been prepared e g Mo6S8 PEt3 6 4 Edge Capped Halide Clusters edit With metals in group 4 or 5 a so called edge capped octahedral clusters are more common Twelve halides are located along the edge of the octahedron and six are terminal Examples of this structure type are tungsten III chloride Ta6Cl14 H2O 4 5 6 Nb6F15 and Nb6F182 1 nbsp Structure of edge capped octahedral clusters such as Ta6Cl184 7 Many of the early metal clusters can only be prepared when they incorporate interstitial atoms One example is Zr6CCl12 2 Tin II clusters edit Octahedral clusters of tin II have been observed in several solid state compounds The reaction of tin II salts with an aqueous base leads to the formation of tin II oxyhydroxide Sn6O4 OH 4 the structure of which comprises discrete Sn6O4 OH 4 clusters In Sn6O4 OH 4 clusters the six tin atoms form an octahedral array with alternate faces of the octahedron occupied by an oxide or hydroxide moiety each bonded in a m3 binding mode to three tin atoms 8 Crystal structures have been reported for compounds with the formula Sn6O4 OR 4 where R is an alkoxide such as a methyl or ethyl group 9 10 Recently it was demonstrated that anionic tin II clusters Sn6O8 4 may form the close packed arrays as in the case of a Sn6SiO8 which adopts the zinc blende structure comprising a face centred cubic array of Sn6O8 4 clusters with Si4 occupying half of the tetrahedral holes 11 A polymorph b Sn6SiO8 has been identified as a product of pewter corrosion in aqueous conditions and is a structural analogue of wurtzite 12 Electron counting in octahedral halide and chalcogenide clusters editThe species Mo6Cl142 feature Mo II d4 centers Six Mo II centers gives rise to a total of 24 valence electrons or 2e Mo Mo vector More electron deficient derivatives such as Ta6Cl184 have fewer d electrons For example the naked cluster Ta614 the core of Ta6Cl184 would have 5 6 14 16 valence electrons Fewer d electrons result in weakened M M bonding and the extended Ta Ta distances accommodate doubly bridging halides Other classes of octahedral clusters editIn the area of metal carbonyl clusters a prototypical octahedral cluster is Fe6C CO 16 2 which is obtained by heating iron pentacarbonyl with sodium Some of the CO ligands are bridging and many are terminal A carbide ligand resides at the center of the cluster A variety of analogous compounds have been reported where some or all of the Fe centres are replaced by Ru Mn and other metals Outside of carbonyl clusters gold forms octahedral clusters nbsp The complex Au6C PPh3 6 2 containing a carbon gold core References edit a b Eric J Welch and Jeffrey R Long Atomlike Building Units of Adjustable Character Solid State and Solution Routes to Manipulating Hexanuclear Transition Metal Chalcohalide Clusters in Progress in Inorganic Chemistry Volume 54 Kenneth D Karlin ISBN 0 471 72348 7 2005 Link a b Arndt Simon Metal clusters inside out Phil Trans R Soc A 2010 vol 368 1285 1299 doi 10 1098 rsta 2009 0271 Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann ISBN 978 0 08 037941 8 Saito T and Imoto H Chalcogenide Cluster Complexes of Chromium Molybdenum Tungsten and Rhenium Bulletin Chemical Society of Japan 1996 volume 69 pp 2403 2417 doi 10 1246 bcsj 69 2403 Duraisamy Thirumalai Hay Daniel N T Messerle Louis 2014 Octahedral Hexatantalum Halide Clusters Inorganic Syntheses Volume 36 Vol 36 pp 1 8 doi 10 1002 9781118744994 ch1 ISBN 9781118744994 Koknat F W Marko D J Tetradecachlorohexatantalum Octahydrate Ta6Cl14 8H2O Inorganic Syntheses 2004 volume 34 pp 187 191 ISBN 0 471 64750 0 describes Na4Ta6Cl18 Thaxton C B Jacobson R A 1971 The Crystal Structure of H2 Ta6Cl18 H2O 6 Inorganic Chemistry 10 1460 1463 doi 10 1021 ic50101a029 Abrahams I Grimes S M Johnston S R Knowles J C 1996 02 15 Tin II Oxyhydroxide by X ray Powder Diffraction Acta Crystallographica Section C Crystal Structure Communications 52 2 286 288 doi 10 1107 S0108270195012625 Harrison Philip G Haylett Bernard J King Trevor J 1978 X Ray crystal structure of Sn6O4 OMe 4 an intermediate in the hydrolysis of tin II dimethoxide Journal of the Chemical Society Chemical Communications 3 112 113 doi 10 1039 c39780000112 ISSN 0022 4936 Suslova E V Turova N Ya Kessler V G Belokon A I November 2007 Electrosynthesis of tin II alkoxides Russian Journal of Inorganic Chemistry 52 11 1682 1686 doi 10 1134 S0036023607110083 ISSN 0036 0236 S2CID 93819431 Parsons Daniel S Savva Savvaki N Tang Wai Chi Ingram Andrew Hriljac Joseph A 2019 12 16 Sn 6 SiO 8 a Tin II Silicate with a Zinc Blende Related Structure and High Thermal Stability Inorganic Chemistry 58 24 16313 16316 doi 10 1021 acs inorgchem 9b02615 ISSN 0020 1669 PMID 31804067 Locock A J Ramik R A Back M E 2006 12 01 THE STRUCTURES OF TWO NOVEL Sn2 OXYSALTS FOUND WITH ROMARCHITE AND HYDROROMARCHITE AS CORROSION PRODUCTS OF PEWTER ARTIFACTS The Canadian Mineralogist 44 6 1457 1467 Bibcode 2006CaMin 44 1457L doi 10 2113 gscanmin 44 6 1457 ISSN 0008 4476 Retrieved from https en wikipedia org w index php title Octahedral cluster amp oldid 1224322352, wikipedia, wiki, book, books, library,

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