Block Transition Metals

The d-block transition metals, which form a group of elements ten-wide and four-deep in the Periodic Table associated with filling of the five d orbitals, represent the classical metals of coordination chemistry and the ones on which there is significant and continuing focus. In particular, the lighter and usually more abundant or accessible elements of the first row of the d block are the centre of most attention. Whereas stable oxidation states of p-block elements correspond dominantly to empty or filled valence shells, the d-block elements characteristically exhibit stable oxidation states where the nd shell remains partly filled it is this behaviour that plays an overarching role in the chemical and physical properties of this family of elements, as covered in earlier chapters. 

Examples of metal-metal bonded complexes of the second and third row d-block elements molybdenum and tungsten. The Mo—Mo bond is quite short, and this is an example of a compound with a multiple metal-metal bond other examples display single metal-metal bonds. 

---

Green MLH, Green JC (In preparation) Systematic chemistry of covalent compounds of the d-block transition metals Seddon EA, Seddon KR (1984) The chemistry of ruthenium, Elsevier, Amsterdam... 

Quaternary chalcogenides of the type A Ln M X, containing three metal elements from different blocks of the Periodic Table (A is an alkali or alkaline earth metal, Ln is an /-block lanthanide or scandium, M is a p-block main group or a r/-block transition metal, and X is S or Se) are also known [65]. 

Chen YK, Chu A, Cook J, Green MLH, Harris PJF, Heesom R, Humphries M, Sloan J, Tsang SC, Turner JFC (1997) Synthesis of carbon nanotubes containing metal oxides and metals of the d-block and f-block transition metals and related studies. J. Mater. Chem. 7 545-549. 

The variety of stoichiometries that one comes across in the case of lanthanide complexes is much more than what one usually encounters in the case of cf-block transition metal complexes. This is due to the wider range of coordination numbers that are possible for the lanthanides. The stoichiometry of a lanthanide complex depends on the size of the metal ion, the size of the ligand, the nature of the anion and the synthetic procedure used. 

The d block transition metals are metals with an incomplete d subshell in at least one of their ions. We consider the first row of the transition metals as being from scandium to zinc and the second row from yttrium to cadmium. Platinum and gold are in the third row. Most of the common metals in everyday use are transition metals. 

Metallic hydrides are formed by reaction of the lanthanide and actinide metals and certain of the d-block transition metals with variable amounts of hydrogen. These hydrides have the general formula MHX, where the x subscript represents... 

As in the SETFICS and TALSPEAK processes, the DIAMEX-SANEX/HDEHP process involves selectively back-extracting the trivalent actinides by a hydrophilic polyamino-carboxylate complexing agent, HEDTA, in a citric acid buffered solution (pH 3). However, the combination of HDEHP and DMDOHEMA at high acidity promotes the coextraction of some block transition metals, such as Pd(II), Fe(III), Zr(IV), and Mo(VI), which must be dealt with by specific stripping steps (as described on Figure 3.26) that increase the total volume of the output streams ... 

The interfering block transition metals, Mo and Pd, are stripped prior to the TPEs by a citrate solution at pH 3. 

Transition Metals Groups 3-10, d block Transition metals are famous for the colored salts and colored solutions they form. Many gems contain numerous transition metals. It is hard to predict the charge of a transition metal ion because the transition metals have multiple oxidation states. One transition metal, Hg, exists as a liquid at room temperature. 

Quite recently oxonium compounds of d-block transition metals and also closely related complexes of the lanthanides were isolated for the first time. In general, the solvent is aHF, and a strong Lewis acid, preferably AsFs, is added to the solution or suspension of an appropriate metal compound. Water may be introduced in various ways, e.g. using hydrated starting material, dissolution of metal oxides or even through the addition of H-.OAsFg. Some examples of reactions leading to new oxonium fluorometallates are collected in Table 4. 

Methanol is currently the largest volume carbonylation product and is made by passing syngas (CO -f H2 Section 4.1.2) over a solid Cu-Zn oxide catalyst. Most of the other carbonylation reactions are catalyzed by the later c -block transition metals, often under homogeneous conditions in solution. This is despite a public perception that the use of heavy metals (such as the complexes of the 4d and 5d transition metals) is generally undesirable. However their extremely effective catalytic properties now make their use mandatory in many... 

Question 1.1 Using the information you have been given in Section 1.2, draw up a table comparing (in three columns) the characteristic features of the s-block metals (use group 1 as typical) and the d-block transition metals. 

One area which demonstrates the contrast between the lanthanides and the d-block transition metals is the absence of stable carbonyls. Co-condensation of the vapours of several metals (Pr, Nd, Eu, Gd, Ho, Yb) with CO in argon matrices at 4 K leads to compounds identified as [Ln(CO) t] (x = 1—6) from their IR spectra. They decompose on warming above 40 K. 

Question 6.15 Why do stable binary carbonyls of these metals not exist (Consider what d-block transition metals need to do to form stable carbonyls that the lanthanides cannot do.)... 

Equations (14-17) summarize the different counting rales as applied to om generalized d-block transition metal complex [MXaL6] +, where N is the Group number, and n is the d" configuration. 

Group designations are traditionally given on the periodic table for the ri-block transition metals (Fig. 20.1). However, these designations do not relate as directly to the chemical behavior of these, elements as do the designations for the representative elements (the A groups), so we will not use them. 

As is clear from the introductory discussion, most, if not all, of the d-block transition metals are expected to participate in reactions that are related to those discussed here. In addition to the Co-based methodology mentioned earlier, some related reactions of Pd and are known. Also related are the cyclization reactions of metal-carbene complexes containing Cr, Mo, W and other transition metals with alkynes and alkenes and a recently reported Nb- or Ta-promoted diyne-alkyne cyclization reaction, which appears to be closely related to a number of previously developed alkyne cyclotrimerization reactions, such as those catalyzed by Co. Investigations of reactions involving other transition metals may prove to be important especially from the viewpoint of developing asymmetric and catalytic procedures. 

The abundances in the Earth s crust of both the d-block transition metals and the f-block inner transition metals vary considerably, as shown in Table 1.2. Iron is the most common of the transition metals (6.30% by mass of the crustal rocks) and this reflects the high yield of iron from element synthesis reactions in stellar supernovae. Titanium (0.66%) and manganese (0.11%) are also quite abundant, but some of the heavier... 

Di-terf-butylphosphido (t-Bu2P) complexes of the d-block transition metals have been synthesized in order to study the steric effects of phosphido... 

Alkyl rheniumpentacarbonyl species are known to be reluctant to undergo alkyl migration reactions (43)-, third row i/-block transition metals (i.e., 5d) are usually less inclined to undergo alkyl migration than the 3d... 

The d-block transition metals and f-block inner transition metals are more similar across a period than are the s-block and p-block elements. 

It appears that the activation of C-C bonds in unstrained alkanes by a d-block transition metal complex may require initial C-H bond activation to... 

Perspective Homogeneous d-block transition metal catalysts Challenges in and requirements for molecular modeling of catalysts and catalytic reactions 168... 

---