J-block elements

With the more electropositive metals such as the lanthanides,31 the dissolution of their chlorides into alcohols results only in the formation of solvates such as LaCl3 SPr OH.31 For most of the early J-block elements, only partial replacement of halide ligands occurs on alcoholysis (equations 5 and... 

Ammonia is very soluble in water because the NH, molecules can form hydrogen bonds to H20 molecules. Ammonia is a weak Branstcd base in water it is also a reasonably strong Lewis base, particularly toward J-block elements. For example, it reacts with Cu2+(aq) ions to give a deep blue complex (Fig. 15.4) ... 

Coordination numbers of the constiment atoms are not always helpful for differentiating bonding t)q)es either. The two most common coordination geometries observed in the covalent compounds of p-block and J-block elements are tetrahedral and octahedral coordination, respectively. These happen to be the same coordination numbers around the interstitial sites in the close-packed stmctures of many metaUic elements and ionic compounds. 

One other approach for the activation of alkane C-H bonds is to choose a metal that forms a strong metal-to-carbon bond. Main group and early J-block elements (e.g., AIR3, TaRs, etc.) as well as lanthanide and actinide alkyls fall into this category. 

Note the distinction between a transition and J-block element. Elements in groups 3-12 inclusive are collectively called J-block elements, but by the lUPAC rulings, a transition metal is an element, an atom of which possesses an incomplete fi -shell or which gives rise to a cation with an incomplete fi -shell. Thus, elements in group 12 are not classed as transition elements. Collective names for some of the groups of elements in the periodic table are given in Table 1.4. 

S—F bonds. Other examples of hypervalent species of the j-block elements are PF5, POCI3, AsFg and [SeClg]. The... 

The values of Vetai listed in Table 5.2 refer to 12-coordi-nate metal centres since not all metals actually adopt structures with 12-coordinate atoms, some values of Vetai have been estimated. The need for a consistent set of data is obvious if one is to make meaningful comparisons within a periodic sequence of elements. Values of Vetai (Table 5.2) increase down each of groups 1, 2, 13 and 14. In each of the triads of the J-block elements, Vetai generally increases on going from the hrst to second row element, but there is little change on going from the second to third row metal. This latter observation is due to the presence of a filled 4/ level, and the so-called lanthanoid contraction (see Sections 22.3 and 24.3). 

Examples of coordination complexes include those involving rf-block metal ions (e.g. [Co(NH3)6], 6.12) and species with a central j-block element (e.g. [BF4] , 6.13, and H3B-THF, 6.14) (THF = tetrahydrofuran) although 6.14 is unstable with respect to hydrolysis in aqueous solution. Equations 6.59-6.61 show the formation of these coordination complexes. 

Figure 20.27 shows a plot of experimental lattice energy data for metal(II) chlorides of first row J-block elements. In each salt, the metal ion is high-spin and lies in an octahedral environment in the solid state. The double hump in Figure 20.27 is reminiscent of that in Figure 20.26, albeit with respect to a reference line which shows a general increase in lattice energy as the period is crossed. Similar plots can be obtained for species such as MF2, MF3 and [MFg], but for each series, only limited data are available and complete trends cannot be studied. 

Most complex chemistry of the actinides is in aqueous solution. However, a number of neutral complexes and complexes between halides and neutral donor ligands such as Ph3PO or Me2SO are known. There are very few complexes formed by n acid ligands, providing a notable contrast to the J-block elements for example, there is no evidence for the bonding of NO or alkenes. However, uranium carbonyls have been trapped in matrixes at4°K.16a... 

The VSEPR model works best for simple halides of the j-block elements, but may also be applied to species with other substituents. However, the model does not take steric factors (i.e. the relative sizes of substituents) into account. 

One of the characteristic features of metal(loid) alkoxides is their ability to exchange alkoxo groups with alcohols, and this has been widely exploited for the synthesis of new homo- and heteroleptic alkoxide derivatives of various s-, d-, f-, and j)-block elements... 

In general, when a J-block element becomes an ion, it loses electrons first from the ns subsheU and then from the (n — l)d subshell. 

The hydrides of /j-block elements represent the best documented set of experimental stretching force constants. The previous strategy yields the surprising result that, as for homonuclear interactions, the effective critical stretch Ad is a function of only bond order. In the first linear region, = 1.3, the value Ad = 0.115, with bond orders as identified in Table 11, predicts the following force constants ... 

Note A transition element has a partially filled i/-subshell either as the element or in any commonly occurring oxidation state. Thus, Zn, Cd, and Hg with completely filled (i-subshells are not transition elements. The n- l)d electrons of the J-block elements are considered to be valence electrons. Groups 1, 2, and 13-18 are alternatively labeled with Roman numerals I-VIII, which correspond to the number of valence electrons in the element. 

Which of the following is a J-block element (Select all that apply.)... 

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