41.R. Steudel, “Liquid Sulfur,” in R. Steudel (Ed.), Elemental Sulfur and Sulfur-Rich Compounds I, Topics in Current Chemistry 230, Springer, 81–116 (2003).
42.J. I. Lunine and D. J. Stevenson, “Physics and Chemistry of Sulfur Lakes on Io,” Icarus 64(3), 345–367 (1985).
43.M. Y. Zolotov and B. Fegley Jr., “Volcanic Origin of Disulfur Monoxide (S2O) on Io,” Icarus 133(2), 293–297 (1998).
44.R. J. Gillespie et al., “Polyatomic Cations of Sulfur. I. Preparation and Properties of and ” Inorg. Chem. 10(7), 1327–1332 (1971).
45.A. Böck et al., “Selenocysteine: The 21st Amino Acid,” Mol. Microbiol. 5(3), 515–520 (1991).
46.M. Sarquis and C. D. Mickey, “Selenium, Part 1: Its Chemistry and Occurrence,” J. Chem. Educ. 57(12), 886–889 (1980).
47.S. E. Ramadan et al., “Incorporation of Tellurium into Amino Acids and Proteins in a Tellurium-Tolerant Fungi,” Biol. Trace Element Res. 20(3), 225–232 (1989).
48.K. Satheeshkumar et al., “Reactivity of Selenocystine and Tellurocystine: Structure and Antioxidant Activity of the Derivatives,” Chem. Eur. J. 24(66), 17513–17522 (2018).
49.E. H. Wiebenga, E. E. Havinga, and K. H. Boswijk, “Structures of Interhalogen Compounds and Polyhalides,” Adv. Inorg. Chem. Radiochem. 3, 133–169 (1961).
50.L. S. Bartell, “A Structural Chemist’s Entanglement with Gillespie’s Theories of Molecular Geometry,” Coordination Chem. Rev. 197(1), 37–49 (2000).
51.S. S. Nabiev, V. B. Sokolov, and B. B. Cahivanov, “Structure of Simple and Complex Noble Gas Fluorides,” Crystallogr. Rep. 56(5), 774–791 (2011).
52.W. Henderson, Tutorial Chemistry Texts, 3: Main Group Chemistry, Royal Society of Chemistry, Cambridge, 154 (2000).
53.H.-J. Frohn and S. Jakobs, “The Pentafluorophenylxenon(II) Cation: [C6F5Xe]+; the First Stable System with a Xenon–Carbon Bond,” J. Chem. Soc. Chem. Commun. 625–627 (1989).
54.H.-J. Frohn, T. Schroer, and G. Henkel, “C6F5XeCl and [(C6F5Xe)2Cl][AsF6]: The First Isolated and Unambiguously Characterized Xenon(II) Chlorine Compounds,” Angew. Chem. Int. Ed. 38(17), 2554–2556 (1999).
55.S. Seidel and K. Seppelt, “Xenon as a Complex Ligand: The Tetra Xenono Gold(II) Cation in ,” Science 290(5489), 117–118 (2000).
56.G. J. Schrobilgen, “The Fluoro(hydrocyano)krypton(II) Cation [HC≡N–Kr–F]+; the First Example of a Krypton–Nitrogen Bond,” J. Chem. Soc. Chem. Commun. 863–865 (1988).
57.L. Khriachtchev et al. “A Stable Argon Compound,” Nature 406, 874–876 (2000).
58.S. Riedel and M. Kaupp, “The Highest Oxidation States of the Transition Metal Elements,” Coordination Chem. Rev. 253(5–6), 606–624 (2009).
59.J. Šima, “Structure-Related Melting Points and Boiling Points of Inorganic Compounds,” Found. Chem. 18, 67–79 (2016).
60.G. E. Rogers, “A Visually Attractive ‘Interconnected Network of Ideas’ for Organizing the Teaching and Learning of Descriptive Inorganic Chemistry,” J. Chem. Educ. 91, 216–224 (2014).
Chapter 8
Patterns among the Transition Metals
In this chapter, we will deconstruct the monolithic block of transition metals. Traditionally, classification has been by Group, but there are far richer patterns and trends to be found. By using chemical criteria for assignment, a hybrid approach to categorizing and clustering transition metals offers many advantages. Nevertheless, ambiguities arise as to the assignments that we choose.
The first task is to define the transition metals, which is not quite as obvious as it may seem. The main group elements are always identified as the members of Groups 1 to 2, and 13 to 18; that is, the s-block and p-block elements. In addition, about half of textbook sources include Group 12 as main group elements [1]. One might justifiably conclude by deduction that Groups 3 to 11, or Groups 3 to 12, would be the transition metals. As with much of inorganic chemistry, it is not that simple.
What Is a Transition Metal?
The terms “d-block metal” and “transition metal” are not synonymous. Identifying a “transition metal” is not simply a question of location in the Periodic Table, but also one of chemical behavior. A definition common among inorganic chemists is a transition metal is an element that has at least one simple ion with an incomplete outer set of d electrons.
Exclusion of Group 3
Using the criterion earlier, the Group 3 metals are excluded as their common chemistry is all based on the d0 3+ ion, Sc3+ and Y3+. In fact, the chemistry of these two metals more closely resembles that of the lanthanoids. Patterns among the Group 3 elements, therefore, will be discussed in Chapter 12. Of note, the classic series by Sneed and Brasted, Comprehensive Inorganic Chemistry, combined scandium and yttrium with the lanthanoids [2].
Exclusion of Group 12
The Group 12 metals are also excluded. For them, the predominant ions, Zn2+, Cd2+, and Hg2+ have d10 configurations. The isolation of d8 mercury(IV) fluoride, HgF4, at very low temperatures [3], initially provoked the claim that mercury should be redesignated as a transition metal. As ever more exotic and fragile species are identified [4], there is the potential for a never-ending expansion of claimed members of the transition metal series.
However, such an eventuality can be avoided by using a definition of:
A transition metal is an element that has at least one simple ion with an incomplete outer set of d electrons, which is stable under ambient conditions.
Here, this definition will be utilized, though it will be shown that there can be considered one exception to the rule. Before doing so, it is appropriate to review the previous categorizations of transition metals.
Exclusion of Honorary Transition Metals
A new term entering the vocabulary of inorganic chemistry is that of honorary d elements [5] or honorary transition metals [6]. These terms have been devised to describe organometallic compounds of Group 1 or Group 2 elements that, it is claimed, are using their inner d-orbitals in bonding. Such compounds have been identified by computational studies and/or by synthesis under extremely low temperatures. As such, they are excluded by the earlier definition from study here.
Previous Classifications of Transition Metals
One of the modern authoritative works on inorganic chemistry, Greenwood and Earnshaw’s Chemistry of the Elements [7] treats each of the transition metal groups as individual entities, devoting a chapter to Group 4, one to Group 5, and so on (Figure 8.1).
The species that seem to be Group-specific are the simple carbonyls [8]. The pattern is shown in Table 8.1.
Another common approach is adopted in Advanced Inorganic Chemistry (Cotton, Wilkinson,
