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

COURSE OBJECTIVES (AIMS): This course intends to introduce the students to d-block metal chemistry. Special emphasis will be given to the reactivity of metals and coordination numbers. The students will also learn basic theories related to coordination chemistry such as: valance bond theory, crystal field theory, molecular orbital theory, and ligand field theory. Electronic spectroscopy will be discussed along with reaction mechanisms for coordination compounds. Finally, students will be introduced to the basics of organometallic chemistry including the 18 - electron rule, types of organometallic compounds and heterogeneous catalysis.

COURSE DESCRIPTION: - Introduction to d-bolck elements, the reactivity of metals, electroneutrality principle, coordination numbers, geometries and isomerism of complexes. - Coordination compounds: valance bond theory, crystal field theory, molecular bond theory, ligand field theory, electronic spectra, magnetic properties, and ligand field stabilization energy. - Introduction to reaction mechanisms: ligand substitution and electron-transfer processes. - Introductory organometallic chemistry: common types of ligands, the 18- electron rule, metal carbonyls, types of organometallic compounds and reactions and heterogeneous catalysis.

Introduction to transition metals d-Block elements occupy the middle portion of the periodic table i.e. between s- and p-block elements. They include elements from groups 3 to 12. In these elements the outermost shell contains one or two electrons in their ns orbital but the last electron enters into the inner d-subshell i.e. (n-l) d orbital.

Ex 1: Copper, silver and gold are transition elements Definition of transition element: is an element which has partially field d or f orbials in its atomic state or one of its oxidation state. Ex 1: Copper, silver and gold are transition elements The electronic configurations of these elements are: 29Cu: [Ar]18 4s1 3d10 47Ag: [Kr]365s1 4d10 79Au: [Xe]54 4f146s1 5d10 These elements have 2+ and 3+ oxidation states in which d orbitals will be d8 and d9 which are partially field. Ex 2: Zinc, cadmium and mercury are not transition metals (why): The electronic configurations of these elements are: 30Zn: [Ar]18 4s2 3d10 48Cd: [Kr]36 5s2 4d10 80Hg: [Xe]54 4f14 6s2 5d10 These elements have only 2+ oxidation state in which d orbitals will be d10 which means completely field d orbitals.

General properties of transition metals Exhibit more than one oxidation state. -All of them are Metals - Conduct heat & electricity. -They form an extensive series of compounds known coordination compounds and organometallic compounds. -Transition metals exhibit interesting magnetic properties. - Many of their compounds are colored. - Most elements have incompletely filled d- or f-shell (interesting properties). -Form Alloys. - Form colored compounds. -Transition metals play important roles in biological systems and modern technology.

Coordination compounds Definition of some terms 1- Simple salts NaOH + HCl→NaCl + H2O 2- Molecular or addition compounds Double salts or lattice compounds the lattice compounds having the following properties -They exist as such in crystalline state -when dissolved in water, these dissociate into ions in the same way in which the individual components of the double salts do FeSO4.(NH4)2SO4.6H2O → Fe2+ (aq) +2NH4+(aq) + 2SO42- (aq) (Mohr's salt) +6H2O K2SO4.Al2(SO4)3. 24H2O →2K+(aq)+ 2Al3+ (aq)+ 4SO42 (aq) Potash alum +24H2O

Fe(CN)2 + 4KCN → K4[Fe(CN)6]→ 4K+ + Fe(CN)64- In aqueous solution, double salts give the test of all their constituent ions i.e. the individual components of double salts do not lose their identity ii) Coordination or complex compounds Fe(CN)2 + 4KCN → K4[Fe(CN)6]→ 4K+ + Fe(CN)64- In aqueous solution, the resulting compound, K4[Fe(CN)6], does not give the test for Fe2+ or CN- but give the test for K+ and ferrocyanide ion. -Coordination compounds contain - simple cation and complex anion…… K4[Fe(CN)6] or simple anion and complex cation….. [PtIV(NH3)4Br]Br3 or complex anion and complex cation… [CoIII(NH3)6][CrIII(C2O4)3]

[NiII(ÑH2-CH2-CH2-ÑH2)3]2+ ……… Coordination no is 6 Ligand Neutral molecules or ions (usually anions) which are attached with the central metal ion. The ligand is composed of a number of atoms, the one which is directly attached to the central metal ion is called donor atom. Coordination number (Ligancy) It is the total number of atoms of the ligands that can coordinate to the central metal ion. Numerically coordination number represents the total number of chemical bonds formed between the central metal ion and the donor atoms of the ligands . [FeIII(CN)6]3-……………. Coordination no is 6 [NiII(ÑH2-CH2-CH2-ÑH2)3]2+ ……… Coordination no is 6

Coordination sphere The central metal ion and the ligands that are directly attached to it are enclosed in a square bracket which Werner has called coordination sphere or first sphere attraction. The anion or cation being outside the bracket form the second sphere of attraction.

Classification of ligands 1- Classification based on donor and acceptor properties of the ligands i) Ligands having one (or more) lone pair (or pairs) of electrons a) Ligands which contains vacant π-type orbitals that can receive back donated π -electrons from the metal in low oxidation state b) Ligands which do not have vacant orbitals to receive back donated electrons from the metal . H2O , NH3 , halides ii) Ligands having no lone pair of electrons but have π-bonding electrons CH2=CH2

H2O , NH3 , CO(carbonyl), NO (nitrosyl), NS(thionitrosyl) 2- Classification based on the no. of donor atoms present in the ligands i) Monodentate or unidentate ligands a) Neutral monodentate ligands H2O , NH3 , CO(carbonyl), NO (nitrosyl), NS(thionitrosyl) b) negative monodentate ligands halogens ,CN- (cyano), OCN- (cyanato), SCN-(thiocyanato) c) positive monodentate ligands NO+ (nitrosylium), NH2-NH3+ (hydrazinium) ii) Polydentate or multidentate ligands Ligands with 2 donor atoms…………….bidentate ligands Ligands with 3 donor atoms…………….tridentate ligands Ligands with 4 donor atoms…………….tetradentate ligands Ligands with 5 donor atoms…………….pentadentate ligands Ligands with 6 donor atoms…………….hexadentate ligands

Bridging ligands Ambidentate ligands Monodentate ligands may have more than one free electron pairs and thus may simultaneously coordinate with two or more atoms i.e. the ligands forms 2 bonds with two metal atoms and thus acts as a bridge between the metal atoms. The resulting complex is called bridged complex. OH-, F-, Cl-, SO4- Ambidentate ligands Ligands having two or more donor atoms but only one donor atom is attached to the metal center at a given time M-NO2 Nitro NO2- M-ON=O Nitrito M-CN Cyano CN- M-NC Isocyano M-SCN Thiocyanato NCS- M-NCS Isothiocyanato

Bi-nuclear Bridged octahedral complex