Inorganic Chemistry (2) Prepared by Dr. Hoda El-Ghamry Lecturer of Inorganic Chemistry Faculty of Science-Chemistry Department Tanta University

Coordination number and stereochemistry of complexes The coordination no. shown by metals in complexes are 2-9, the most common are 4 & 6 Coordination number 2 The complexes having CN =2 are linear since this geometry provides the minimum ligand repulsion Cu+, Ag+, Au+ and in some cases Ag2+ form such complexes Example: Cu(CN)2-, Cu(NH3) 2+, Hg(CN)2 , [CuCl2] -

Coordination number 3 The possible geometries exhibited by the CN =3 is Equilateral triangular in which the ligands are arranged at the corners of slightly distorted equilateral triangle with the metal ion at its center Example: [Hgl3] - Coordination number 4 Two possible geometries exhibited by complexes with CN =4 Tetrahedral Square planar

tetrahedral geometry Example: ZnCl42-, Cu(CN) 42-, Cu(X) 4-, FeCl4- square planar geometry Example: [Cu(en)2]2+, Ni(CN) 42-, [Cu(NH 3) 4 ]2+, PtCl42-

Complexes with CN = 5 imay be trigonal bipyramidal or square pyramidal Coordination number 5 Complexes with CN = 5 imay be trigonal bipyramidal or square pyramidal trigonal bipyramidal geometry Example: SnCl5- , [Fe(CO)5], CuCl53- Square pyramidal geometry Example: vanadyl acetyl acetone [VO(acac)2]

Coordination number 6 This is the most common C.N formed by transition metal complexes. The possible geometries exhibited by the CN =6 are Hexagonal planar , trigonal prismatic and octahedral

Nomenclature of coordination compounds Classification of coordination compounds Cationic complexes [CrIII(H2O)4 Cl2]+ Anionic complexes [FeII(CN)6 ]4- Ionic complexes [PtII(Py)4]2+ [PtIICl4]2- Neutral complexes [CoIII(NO2)3 (NH3)3]0 For naming all the types of complexes mentioned above, the following rules are followed: For cationic, anionic and ionic complexes, the positively charged ion is written at first followed by the negatively charged ion Example: [CrIII(NH3)6 ] (NO3)3 Hexaamine chromium (III) nitrate K2[PtIVCl6]2- Potassium hexachloro platinate (IV)

2) For Naming the complex cation or anion, the ligands are named at first and the central metal is named last Order of naming ligands If there are two or more different types of ligands, the order of naming such ligands is: negative ligands, neutral ligands and finally positive ligands. ii) Naming of negative ligands: If the anion name ends in –ide, -ite or ate, the final –e is replaced by O SO32- Sulphite → sulphito SO42- Sulphate → sulphato S2- Sulphide → sulphido NO3- Nitrate → Nitrato Exceptions: F- (Fluoro), Cl- (Chloro), CN- (Cyano), O-2 (oxo), OH- (hydroxo), O22 - (peroxo) iii) The names of neutral ligands are not systematic Special names are used for some ligands H2O → (aqua), NH3 →(ammine), CO → (carbonyl), NO → (nitrosyl)

iv) Positively charged ligands If the cation name ends in –in , we add -ium Example: NH2-NH3+ Hydrazin→hydrazinium v) The prefix di, tri, tetra, penta and hexa are used to indicate the number of ligands vi) When the name of the ligands include a number (e.g. ethylene diamine, dipyridyl, triphenyl ohosphine) the prefixes bis-, tris, tetrakis, pentakis and hexakis are used instead of di, tri, tetra, penta and hexa and in this case the name of the ligand is placed between brackets. Example: [CoIII(en)2 Cl2] Cl dichloro bis (ethylene diamine) cobalt (III) chloride.

vii) For anionic complexes, the suffix ate is attached to the name of the metal. Example: [CrIII(NH3)6 ] (NO3)3 Hexaamine chromium (III) nitrate K2[PtIVCl6]2- Potassium hexachloro platinate (IV) viii) In order to indicate the oxidation state of the metal center, the name of the metal ion is followed by the roman numbers I, II, III which is added between brackets . For negative oxidation state, the negative sign is added before the roman number. Example: [PtIVCl6]2- hexachloro platinate (IV) [Co(CO)4]- tetracarbonyl cobaltate(-I) [Ni(CN)4] 4- tetracyano nickelate (0)

Complexes of ambidentate ligand Ambidentate ligands named by 2 ways: 1- by special names M-NO2 Nitro NO2- M-ON=O Nitrito M-CN Cyano CN- M-NC Isocyano M-SCN Thiocyanato NCS- M-NCS Isothiocyanato 2- The symbol of the element coordinated with the metal ion is written after the name of the ligand Example: [PtIV(SCN)6] 4- hexathiocyanato-S- platinate(IV) [PtIV(NCS)6] 4- hexathiocyanato-N- platinate(IV)

Bridging polynuclear complexes The complexes having two or more metal atoms are called polynuclear complexes. In these complexes, the bridging group is indicated in the complex formula, separately. The Greek letter µ should be repeated before the the name of different bridging ligand Example: µ- hydroxo-bis{penta amine chromium (III)} chloride µ- amido- µ- hydroxo octa amine dicobalt(III) ion

Metal to metal bonding In complexes having metal to metal bonding, the prefix bi- is added before the name of the metals forming a metal to metal bond Example: Dichloro octakis( methyl amine) bi-platinum (II) chloride