കോഓർഡിനേഷൻ ജോമെട്രി

രസതന്ത്രത്തിലെയും അതുമായി ബന്ധമുള്ള പലതരം സോളിഡ് സ്റ്റേറ്റ് രസതന്ത്ര/ഭൗതികശാസ്ത്രമേഖലകളിൽ ഉപയോഗിക്കുന്ന ഒരു പദമാണ് കോഓർഡിനേഷൻ ജോമെട്രി (coordination geometry).
തന്മാത്രകൾ

ഒരു ആറ്റത്തിന്റെ കോഓർഡിനേഷൻ ജോമെട്രി എന്നുപറഞ്ഞാൽ അതിന്റെ മധ്യത്തിലുള്ള ഒരു ആറ്റത്തിനുചുറ്റുമായി ബാക്കിയുള്ള ആറ്റങ്ങൾ ഏതുവിധത്തിൽ ക്രമീകരിച്ചിരിക്കുന്നു എന്നതാണ്. T

അജൈവ കോഓർഡിനേഷൻ കോമ്പ്ലക്സുകൾ
In the field of inorganic coordination complexes it is the geometrical pattern formed by the atoms in the ligands that are bonded to the central atom in a molecule or a coordination complex. The geometrical arrangement will vary according to the number and type of ligands bonded to the metal centre, and to the coordination preference of the central atom, typically a metal in a coordination complex. The number of atoms bonded, (i.e. the number of σ-bonds between central atom and ligands) is termed the coordination number.
The geometrical pattern can be described as a polyhedron where the vertices of the polyhedron are the centres of the coordinating atoms in the ligands.

The coordination preference of a metal often varies with its oxidation state. The number of coordination bonds (coordination number) can vary from two as high as 20 in Th(η5-C5H5)4.

One of the most common coordination geometries is octahedral, where six ligands are coordinated to the metal in a symmetrical distribution, leading to the formation of an octahedron if lines were drawn between the ligands. Other common coordination geometries are tetrahedral and square planar.

Crystal field theory may be used to explain the relative stabilities of transition metal compounds of different coordination geometry, as well as the presence or absence of paramagnetism, whereas VSEPR may be used for complexes of main group element to predict geometry.

ക്രിസ്റ്റലോഗ്രാഫിയിലെ ഉപയോഗം
In a crystal structure the coordination geometry of an atom is the geometrical pattern of coordinating atoms where the definition of coordinating atoms depends on the bonding model used. For example, in the rock salt ionic structure each sodium atom has six near neighbour chloride ions in an octahedral geometry and each chloride has similarly six near neighbour sodium ions in an octahedral geometry. In metals with the body centred cubic (bcc) structure each atom has eight nearest neighbours in a cubic geometry. In metals with the face centred cubic (fcc) structure each atom has twelve nearest neighbours in a cuboctahedral geometry.

കോഓർഡിനേഷൻ ജോമെട്രികളുടെ പട്ടിക
A table of the coordination geometries encountered is shown below with examples of their occurrence in  complexes found as discrete units in compounds and coordination spheres around atoms in crystals (where there is no discrete complex).

കോഓർഡിനേഷൻ അക്കം  ജോമെട്രി  ഡിസ്‌ക്രീറ്റ് (ഫൈനൈറ്റ്) കോമ്പ്ലക്സുകളുടെ ഉദാഹരണങ്ങൾ  ക്രിസ്റ്റലുകളിലെ ഉദാഹരണങ്ങൾ 2 linear 100pxAg(CN)2− in KAg(CN)2 Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications Ag in silver cyanide,Au in AuI 3 trigonal planar100pxHgI3−O in TiO2 rutile structure4tetrahedral100pxCoCl42−Zn and S in zinc sulfide, Si in  silicon dioxide4 square planar100pxAgF4−CuO5 trigonal bipyramidal100pxSnCl5−5 square pyramidal100pxInCl52− in (NEt4)2InCl56 octahedral 100pxFe(H2O)62+Na and Cl in NaCl6 trigonal prismatic100pxMo(SCHCHS)3As in NiAs, Mo in MoS27pentagonal bipyramidal100pxZrF73−  in (NH4)3ZrF7Pa in PaCl57 face capped octahedral100px[HoIII(PhCOCHCOPh)3(H2O)]Crystal and molecular structure of the heptacoordinate complex tris(diphenylpropanedionato)aquoholmium, Ho(PhCOCHCOPh)3.H2O, Zalkin A., Templeton D.H., Karraker D.G,  Inorganic chemistry, 1969, 8, 12,2680 - 2684; La in A-La2O37 trigonal prismatic, square face monocapped100pxTaF72− in K2TaF78 cubic Caesium chloride, calcium fluoride8 square antiprismatic100pxTaF83− in Na3TaF8 Zr(H2O)84+ aqua complexThorium(IV) iodide8 dodecahedral (note: whilst this is the term generally used, the correct term is "bisdisphenoid" or "snub disphenoid" as this polyhedron is a deltahedron)100pxMo(CN)84− in K4[Mo(CN)8].2H2OZr in K2ZrF68 hexagonal bipyramidal100pxN in Li3N8 octahedral, trans-bicappedNi in nickel arsenide, NiAs; 6 As neighbours  + 2 Ni cappingDavid G. Pettifor, Bonding and Structure of Molecules and Solids, 1995, Oxford University Press,8 trigonal prismatic, triangular face bicappedCa in CaFe2O48trigonal prismatic, square face bicappedPuBr39tricapped trigonal prismatic, (three rectangular faces capped)100px[ReH9]2− in potassium nonahydridorhenateTh(H2O)94+ aqua complexSrCl2.6H2O, Th in RbTh3F139  monocapped square antiprismatic100px[Th(tropolonate)4(H2O)]La in LaTe210 bicapped square antiprismaticTh(C2O4)42− 11Th in [ThIV(NO3)4(H2O)3] (NO3− is bidentate) 12 icosahedron100pxTh in Th(NO3)62− ion in Mg[Th(NO3)6].8H2O 12 cuboctahedron100pxZrIV(η3−(BH4)4)atoms in fcc metals e.g. Ca12 anticuboctahedron (triangular orthobicupola)100pxatoms in hcp metals e.g. Sc 14 bicapped hexagonal antiprismaticU(BH4)4

അജൈവ സംയുക്തങ്ങളിലെ നാമകരണം
IUPAC have introduced the polyhedral symbol as part of their IUPAC nomenclature of inorganic chemistry 2005 recommendations to describe the geometry around an atom in a compound.NOMENCLATURE OF INORGANIC CHEMISTRY IUPAC Recommendations 2005 ed. N. G. Connelly et al. RSC Publishing  http://www.chem.qmul.ac.uk/iupac/bioinorg/
IUCr have proposed a symbol which is shown as a superscript in square brackets in the chemical formula. For example, CaF2 would be Ca[8cb]F2[4t], where [8cb] means cubic coordination  and [4t] means tetrahedral. The equivalent symbols in IUPAC are CU−8 and T−4 respectively. 
The IUPAC symbol is applicable to complexes and molecules whereas the IUCr proposal applies to crystalline solids.

ഇവയും കാണുക

Molecular geometry
VSEPR
Ligand field theory
Cis effect
Addition to pi ligands

അവലംബം

Category:Molecular physics
Category:Chemical bonding
Category:Coordination chemistry
Category:Inorganic chemistry