Of transition elements

The periodic table also contains horizontal periods of elements, each period beginning with an element with an outermost electron in a previously empty quantum level and ending with a noble gas. Periods 1, 2 and 3 are called short periods, the remaining are long periods Periods 4 and 5 containing a series of transition elements whilst 6 and 7 contain both a transition and a rare earth senes,... 

Trialkyl- and triarylarsine sulfides have been prepared by several different methods. The reaction of sulfur with a tertiary arsine, with or without a solvent, gives the sulfides in almost quantitative yields. Another method involves the reaction of hydrogen sulfide with a tertiary arsine oxide, hydroxyhahde, or dihaloarsorane. X-ray diffraction studies of triphenylarsine sulfide [3937-40-4], C gH AsS, show the arsenic to be tetrahedral the arsenic—sulfur bond is a tme double bond (137). Triphenylarsine sulfide and trimethylarsine sulfide [38859-90-4], C H AsS, form a number of coordination compounds with salts of transition elements (138,139). Both trialkyl- and triarylarsine selenides have been reported. The trialkyl compounds have been prepared by refluxing trialkylarsines with selenium powder (140). The preparation of triphenylarsine selenide [65374-39-2], C gH AsSe, from dichlorotriphenylarsorane and hydrogen selenide has been reported (141), but other workers could not dupHcate this work (140). 

Speciahst Periodical Reports," io Inorganic Chemisty of Transition Elements, Vols. 1—4, The Chemical Society, London, UK, 1969 to date. 

Fig. 2.23. MNN Auger series in the second series of transition elements [2.129].

Alkali metal acetylides M2C2, MCCH and MCCR can readily be prepared by passing C2H2 or C2HR into solutions of the alkali metal in liquid NH3, and these can be used to synthesize a wide range of transition-element... 

This is the most common coordination number for complexes of transition elements. It can be seen by inspection that, for compounds of the type (Ma4b2), the three symmetrical structures (Fig. 19.6) can give rise to 3, 3 and 2 isomers respectively. Exactly the same is true for compounds of the type [Mayby]. In order to determine the stereochemistry of 6-coordinate complexes very many examples of such compounds were prepared, particularly with M = Cr and Co , and in no case was more than 2 isomers found. This, of course, was only negative evidence for the octahedral structure, though the... 

Because of the differing focus of interest in these elements their chemistries have not developed in parallel and the data on which strict comparisons might be based are not always available. Nevertheless many of the similarities and contrasts expected in the chemistry of transition elements are evident in this triad. The relative stabilities of different oxidation states in aqueous, acidic solutions are summarized in Table 24.2 and Fig. 24.1. 

The total lanthanide contraction is of a similar magnitude to the expansion found in passing from the first to the second transition series, and which might therefore have been expected to occur also in passing from second to third. The interpolation of the lanthanides in fact almost exactly cancels this anticipated increase with the result, noted in preceding chapters, that in each group of transition elements the second and third members have very similar sizes and properties. 

The OrganometaUic chemistry of lanthanides is far less extensive than that of transition elements... 

Fig. 2.28 Solubilities of the first row of transition elements in five liquid metals. (To avoid overlap of points, the graphs have been set at different positions on the solubility axis)...

The most striking feature of the contrasts shown in Table 23-II is that the seventh-row elements display the multiplicity of oxidation states characteristic of transition elements rather than the drab chemistry of the +3 rare earth ions. Whereas Ce+3(aq) can be oxidized to Ce+4(aq) only with an extremely strong oxidizing agent, Th+Yaq) is the stable ion found in thorium salts and Th+3(aq) is unknown. In a similar... 

Supported oxide catalysts were discovered at the same time (8-5) as the two-component Ziegler-Natta catalysts (6, 7) in the early 1950 s. The publications on other types of one-component catalysts [supported organo-metallic compounds of transition elements (8, 9, 9a) and titanium dichloride (10) ] appeared quite recently. 

The catalysts formed by the support of organometallic compounds of transition elements are also of great interest for nonpolymerization reactions. Generally speaking, these catalysts can be used in three various states (a) in the initial state, (b) after reduction, and (c) after oxidation... 

Crystal chemistry of the chalcogenides and pnictides of transition elements. F. Hulliger, Struct. Bonding (Berlin), 1968,4, 83-229 (532). 

Table II. Observed Magnetic Moments of Atoms of Transition Elements in Crystals1).

The Niccolite Structure. The substances which crystallize with the niccolite structure (B8) are compounds of transition elements with S, Se, Te, As, Sb, Bi, or Sn. The physical properties of the substances indicate that the crystals are not ionic, and this is substantiated by the lack of agreement with the structural rules for ionic crystals. Thus each metal atom is surrounded by an octahedron of non-metal atoms but these octahedra share faces, and the edges of the shared faces are longer than other edges (rather than shorter, as in ionic crystals). Hence we conclude that the bonds are covalent, with probably some metallic character also. 

Only two compounds, W2S7CI8 (362) and W4S9CI6 (97) are mentioned in the older literature, their true nature being uncertain. The existence of the other compounds in Table XV seems to be well established. All of them were reported by the same group, and, with few exceptions, it remains the only work (57, 58, 131). This example illustrates that the lack of information on chalcogenide halides, especially of transition elements, has its main origin in the lack of systematic investigations. 

J. Bauer, Proc. Hth Int. Conf. Solid Compounds of Transition Elements, Extended Abstracts P2A1, Vienna, April 1985. 

W. Steurer, P. Rogl, H. Nowotny, paper presented at the Vlth International Conference on Solid Compounds of Transition Elements, Stuttgart, June 12-16, 1979. 

P. Rogl, K. Hiebl, M. J. Sienko, paper presented at the Proceedings of the 7th International Conference on Solid Compouruls of Transition Elements, Grenoble, June 21-26, II, A4. 

The solubility of transition elements in o-rh boron is low. The purity of a-rh boron prepared by thermal decomposition of BI3 is high, although that of -rh prepared from the same reactants is low. Crystallization of a-rh boron from a Pt melt requires pure chemicals. The solubility of transition and inner transition elements in -tetragonal boron is not known, but that in j8-rh boron is deseribed in 6.7.2.5.2 and 6.7.2.5.3. 

The materials for solid solutions of transition elements in j3-rh boron are prepared by arc melting the component elements or by solid-state diffusion of the metal into /3-rhombohedral (/3-rh) boron. Compositions as determined by erystal structure and electron microprobe analyses together with the unit cell dimensions are given in Table 1. The volume of the unit cell (V ) increases when the solid solution is formed. As illustrated in Fig. 1, V increases nearly linearly with metal content for the solid solution of Cu in /3-rh boron. In addition to the elements listed in Table 1, the expansion of the unit cell exceeds 7.0 X 10 pm for saturated solid solutions " of Ti, V, (2o, Ni, As, Se and Hf in /3-rh boron, whereas the increase is smaller for the remaining elements. The solubility of these elements does not exceed a few tenths at %. The microhardness of the solid solution increases with V . Boron is a brittle material, indicating the accommodation of transition-element atoms in the -rh boron structure is associated with an increase in the cohesion energy of the solid. 

Other single-crystal x-ray diffraction studies of transition element dopants in jS-rh boron are based on the results of a refinement of the /3-rh boron structure that establishes the occurrence of four new low-occupancy (3.7, 6.6, 6.8 and 8.5%) B positions in addition to the earlier known ones. The dopant elements studied, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Hf and Ta, do not enter B positions in the framework, but they enter the Al, A2, D and E positions. In some cases the doping elements have been studied at several concentrations for each element and for different cooling rates. The percentage occupancies of certain positions are eorrelated with the atomie sizes of the dopants. The bond distances between the polyhedra are shorter than those within the polyhedra. The mechanism of doping for some cases is denoted displacive, rather than interstitial or substitutional, because of competing interactions between the six different partially occupied B positions and dopant atoms. 

Mullay JJ (1987) Estimation of Atomic and Group Electronegativities. 66 1-25 Muller A, Baran E), Carter RO (1976) Vibrational Spectra of Oxo-, Thio-, and Selenometallates of Transition Elements in the Solid State. 26 81-139 Muller A, Diemann E, Jorgensen CK (1973) Electronic Spectra of Tetrahedral Oxo, Thio and Seleno Complexes. Formed by Elements of the Beginning of the Transition Groups. 14 23-47... 

We note that the valence orbitals of metal atoms order in energy as AE>Ln>M. The d-levels of transition elements (M) range the lowest, and are therefore most sensitive for reduction, or to form a stable binary metal nitride. This may also explain the virtual absence of d-element compounds with 16 (valence) electron species, such as [N=N=N] , [N=C=N] , [N=B=N] T [C=C=CfT or [C=B=C] T at least through high-temperature syntheses. 

Reaction of Organometallic Complexes with Particles of Transition Elements The Stepwise Hydrogenolysis... 

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