The Chemistry of Transition Metals

Let s begin by surveying some of the key physical and chemical properties of the transition-metal elements and interpreting trends in those properties using the quantum theory of atomic structure developed in Chapter 5. We focus initially on the fourth-period elements, also called the first transition series (those from scandium through zinc in which the 3d shell is progressively filled). Then we discuss the periodic trends in the melting points and atomic radii of the second and third transition series elements. 

TABLE 8.1 Properties of the Fourth-Period Transition Elements 

FIGURE 8.1 Variation of atomic radii through the fourth-, fifth-, and sixth-period transition-metal elements. Symbols shown are for the fourth-period elements. 

FIGURE 8.2 Variation of melting points through the three periods of transition-metal elements. 

FIGURE 8.3 Enthalpies of hydration of Ions, defined as AW (M (aq)) - AW (M +(g)). The crystal field stabilization energy (discussed In Section 8.5) preferentially stabilizes certain Ions, lowering from a line representing a linear change with Increasing atomic number (red line) to the experimental (blue) line. 

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R. H. Crabtree The Organometallic Chemistry of the Transition Metals, Wiley, New York, 1988, 440 pp. 

Section 20.1 deals with the processes by which these metals are obtained from their principal ores. Section 20.2 describes the reactions of the alkali and alkaline earth metals, particularly those with hydrogen, oxygen, and water. Section 20.3 considers the redox chemistry of the transition metals, their cations (e.g., Fe2+, Fe3+), and their oxoanions (e.g., Cr042-). ... 

For a review of these complexes and their role in this reaction, see Crabtree, R.H. The Organometallic Chemistry of the Transition Metals Wiley NY, 1988, p. 244. 

A species that bonds to a metal cation to form a complex is known as a ligand. Any species that has a lone pair of electrons has the potential to be a ligand, but in this section, we confine our description to a few of the most common ligands ammonia, compounds derived from ammonia, cyanide, and halides. We describe additional examples in Chapter 20 which addresses the chemistry of the transition metals. 

The chemistry of the transition metals is determined in part by their atomic ionization energies. Metals of the 3d and 4d series show a gradual increase in ionization energy with atomic number (Z), whereas the trend for the 5d series is more pronounced (Figure 20-3). First ionization energies for transition metals in the 3d and 4d series are between 650 and 750 kJ/mol, somewhat higher than the values for Group 2 alkaline earth metals but lower than the typical values for nonmetals in the p block. 

Crabtree RH (2005) The organometaUic chemistry of the transition metals. Wiley, New... 

The metal complexes discussed thus far bear little resemblance to the vast majority of common transition-metal complexes. Transition-metal chemistry is dominated by octahedral, square-planar, and tetrahedral coordination geometries, mixed ligand sets, and adherence to the 18-electron rule. The following three sections introduce donor-acceptor interactions that, although not unique to bonding in the d block, make the chemistry of the transition metals so distinctive. 

Clearly then, in glasses coloured by metal ions, the co-ordination chemistry of the transition metal ion has a major influence on the colour. The other major influence is the oxidation state of the metal ion, since variable valency is another characteristic of the transition metals. All other things being equal, for example, iron in the Fe11 form will give a pale blue colour, whereas Fem gives... 

Crabtree, R. H. The organometallic chemistry of the transition metals, third edition, John Wiley Sons (2001)... 

The aim of this Specialist Periodical Report is to cover in a comprehensive way the chemistry of the transition metals including the lanthanides and actinides. It includes published data on the metal carbonyls but does not necessarily include results concerned with organometallic complexes or spectroscopic data which are published elsewhere. 

The chemistry of the transition metals including chromium(III) with these ligands has been the subject of a recent and extensive review,788 with references to the early literature. The close relationship between the catechol (180), semiquinone (181) and quinone (182) complexes may be appreciated by considering the redox equation below (equation 44). 789 The formal reduction potentials for the chromium(III) complexes (183-186 equation 45) are +0.03, -0.47 and -0.89 V (vs. SCE in acetonitrile) respectively. 

In Ihis chapter the theories developed previously will be used 10 help correlate the important facts of the chemistry of groups 1—12 Much of the chemistry of these elements, in particular the transition metals, has already been included in the chapters on coordination chemistry (Chapters II, 12, and 13). More will be discussed in the chapters on organometaJlic chemistry (Chapter 15), clusters (Chapter 16), and the descriptive biological chemistry of the transition metals (Chapter 19). The present chapter will concentrate on the trends within the series (Sc to Zn, Y to Cd, Lu to Hg, La to Lu, and Ac to Lr), the differences between groups (Ti — Zr - Hf Cu — Ag - Au), and the stable oxidation stales of the various metals. 

H It is often helpful to view the descriptive chemistry of the transition metals from different perspectives in a comparative Study. For a thorough review of transition metal chemistry in an clomcnl-by-clcment approach, sec Cotton. F. A. Wilkinson. C. Advanced Inorgomt Chemistry.5 h cd. Wiley New York. I9H8, or Grecnwnud. N. N. Eamshaw. A. Chemistry of the Elements. Pcrgamon Oxford. 1984. 

One generalization of the descriptive chemistry of the transition metals is that the heavier congeners (eg. Mo, W) more readily show the highest oxidation state than does the lightest congener (e, Cr). Discuss this in terms of ionization energies. 

Ochiai. E.-l. General Prittci/rles of Biothemisuy of ihe Elements Plenum New York. 1987 pp 217-221. Crabtree. R. H. The Orgimomelattu. Chemistry of the Transition Metals Wiley New York. 1988 pp 388-393. 

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