Transition Metals

Transition Metals - 1 TRANSITION METALS (The d Group...

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Unformatted text preview: 1 TRANSITION METALS (The d Group Elements) I. General. A. Electronic Structure and Oxidation States. 1. Elements in groups 3 through 12. a. Group 1 st Row Configuration Valence Configuration 3 21 Sc[Ar] 18 3d 1 4s 2 d 1 s 2 4 22 Ti[Ar] 18 3d 2 4s 2 d 2 s 2 5 23 V[Ar] 18 3d 3 4s 2 d 3 s 2 6 24 Cr[Ar] 18 3d 5 4s 1 d 5 s 1 7 25 Mn[Ar] 18 3d 5 4s 2 d 5 s 2 8 26 Fe[Ar] 18 3d 6 4s 2 d 6 s 2 9 27 Co[Ar] 18 3d 7 4s 2 d 7 s 2 10 28 Ni[Ar] 18 3d 8 4s 2 d 8 s 2 11 29 Cu[Ar] 18 3d 10 4s 1 d 10 s 1 12 30 Zn[Ar] 18 3d 10 4s 2 d 10 s 2 b. In forming cations, lose s 2 before losing d electrons. 27 Co 2+ [Ar] 18 3d 7, Co 3+ [Ar] 18 3d 6 , 28 Ni 2+ [Ar] 18 3d 8 , 24 Cr 2+ [Ar] 18 3d 4 . c. As more d electrons become involved in bonding, variable valences are found. (exceptions are the groups 3 and 12 metals) 2. Consider some compounds of iron. Compound Ox. State Compound Ox. State Fe(CO) 4 2 II Common + II Fe(bipy) 3 I Common + III Fe(CO) 5 0 FeO 4 4 + IV [Fe(H 2 O) 5 NO] 2+ +I FeO 4 3 + V (NO + ) FeO 4 2 + VI The oxidation state of Fe can vary from - 2 to +6 depending on the complex. 3. The oxidation states of the transition metals are functions of the complex in which the metal is involved. These complexes are called coordination compounds , the chemistry of the transition metals is the chemistry of coordination compounds. B. Coordination Compounds. 1. Lewis acid - base adducts in which the transition metal atom or ion acts as a Lewis acid. a. The Lewis bases are called ligands . b. Most ligands are anions or neutral molecules. The only common cationic ligand is the nitrosyl group (NO +). 2 c. Coordination Number = the number of bonds formed by the metal with the ligands. 2. In addition to bonds the metal and ligands can also participate in bonding. There are two types of metal - ligand bonding. a. bonds formed by the overlap of filled ligand orbitals with vacant metal orbitals. 1) Ligands such as OH , O 2 and F can participate in forward bonding. 2) These should stabilize high oxidation state compounds. Note that the high oxidation states of Fe were found in the iron oxides. b. bonds formed by the overlap of vacant ligand orbitals with filled metal orbitals. This type of bonding is called back bonding . Electron density transfer is in the opposite direction from that in bonding. 1) This is important in stabilizing low oxidation state complexes. 2) Examples of ligands that can undergo back bonding are: CO, NO +, PR 3 , olefins and polyolefins. Note in the table of Fe complexes the low oxidation state complexes were those with CO, NO + . C. Ligands (Lewis bases) 1. Monodentate ( most common )....
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This note was uploaded on 04/07/2008 for the course CHEM 1304 taught by Professor Prof.maguire during the Spring '08 term at SMU.

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Transition Metals - 1 TRANSITION METALS (The d Group...

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