Compounds Containing Another Metal Atom

5 Compounds Containing Another Metal Atom. - The cage complex [Mg8(THFFO)8] (THFFO = 2-tetrahydrofuroxide) has been utilised as an alkene polymerisation catalyst. This has been reacted with AlMes and the product [Al3Mg(ii3-0)(THFFO)3(Me)6].C6H5Me has been isolated.  

The reaction of equimolar quantities of 1,8-bistrimethylstannylnaphthalene and GaCb in toluene yields a stannogallacycle (34) namely bis()i-l,8-naph-thalenediyl)(p-chloride)methyltin(IV)chlorogallium(III). This has a folded 

A number of adduct-stabilised Group 13 metal-transition metal carbonyl complexes have been characterised. These incorporate Fe-Ga, Fe-In, W-Al, Cr-Al and Cr-Ga bonds. Structures of two examples [(CO)4Fe-Ga(I)(tmpda)] (36) and [(CO)5W-Al(BuO(tmpda)] (37) are given. 

The synthesis, structure and bonding of the first aluminium(I) and gallium(I) complexes of phosphine-substituted transition metal centres have been published. These have terminal coordinated Cp E ligands (E = Al, Ga or In). Reaction of [(dcpe)Pt(H)(CH2Bu )] [dcpe = bis(dicyclohexylphosphino)ethane] with Cp E yields the tetrahedrally coordinated complexes [(dcpe)Pt(AlCp )2] (38) and [(dcpe)Pt(GaCp )2]. Quantum chemical calculations suggest rather weak Pt-E bonds for both complexes. 

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Another important case of near-degeneracy occurs in compounds containing transition metal atoms. There are two reasons for strong configurational mixing in such molecules. First, the chemical bonds are often weak, leading to a substantial occupation of the anti-bonding orbital. The second reason is... 

Secondly, we have tried to keep our examples simple, although hinting at the existence of some points of a greater complexity. Thus, in recent years there has been enormous study of compounds containing many metal atoms, linked directly to each other, linked indirectly through ligands, or both. So wide has this field become that there is real discussion about whether or not compounds with perhaps 40 or 50 metal atoms or more, directly bonded one to another, should be treated as fragments of a metal as much as chemical molecules. Metal clusters will be the subject of Chapter 15 and metals in Chapter 17. 

The word cluster in this section will refer to complexes of cobalt containing three or more metals for which there is, moreover, evidence for the existence of metal-metal bonds in the complex. In addition, for such compounds to be reported in this section, the otganometallic nature of the cluster (the direct interaction between one of the cobalt atoms and at least one carbon atom) must be present. In fact, purely inorganic cobalt clusters became more numerous until recently. Some examples will be described at the end of this section however, these compounds will not be coveted in any comprehensive fashion. Polynuclear clusters, which contain other metal atoms associated to cobalt, are the subjects of another chapter of this work. 

Compounds (iv)-(vi) in the second row in Fig. 15 contain a CO ligand of which the carbon atom is terminally bonded to a metal atom or bridging two or three metal atoms, and the oxygen atom is further bonded to another metal atom M. ... 

Bismuthides. Many intermetaUic compounds of bismuth with alkafl metals and alkaline earth metals have the expected formulas M Bi and M Bi, respectively. These compounds ate not saltlike but have high coordination numbers, interatomic distances similar to those found in metals, and metallic electrical conductivities. They dissolve to some extent in molten salts (eg, NaCl—Nal) to form solutions that have been interpreted from cryoscopic data as containing some Bi . Both the alkafl and alkaline earth metals form another series of alloylike bismuth compounds that become superconducting at low temperatures (Table 1). The MBi compounds are particularly noteworthy as having extremely short bond distances between the alkafl metal atoms. 

Other types of bonding include donation by Ligand TT-orbitals, as in the classical Zeiss s salt ion [Pt( 7 -CH2=CH2)Cl3] [12275-00-2] and sandwich compounds such as ferrocene. Another type is the delta (5) bond, as in the Re2Clg ion, which consists of two ReCl squares with the Re—Re bonding and echpsed chlorides. The Re—Re 5 bond makes the system quadmply bonded and holds the chlorides in sterically crowded conditions. Numerous other coordination compounds contain two or more metal atoms having metal—metal bonds (11). 

Like graphite, C60 can be transformed into diamond, but the process requires less stringent conditions. It has also been found that Cso becomes a superconductor at low temperature. Another interesting characteristic of Cso is that when it is prepared in the presence of certain metals, the Cso cage can enclose a metal atom. In some cases, other materials can be enclosed within the C60 cage in a "shrink wrapped" manner to form "complexes" that are described as endohedral. It has also been possible to prepare metal complexes of Cso that contain metal-carbon bonds. A compound of this type is (C6H5P)2PtC60. 

In these phases, the unit cell (superstructure cell, super-cell) contains along the oaxis n pseudo-cells of T atoms and m interpenetrating pseudo-cells of X atoms. These phases (Nowotny phases) have been called chimney-ladder phases because they contain rows of atoms X (the ladder ), with variable interatomic spacing from one compound to another, which are inserted into channels ( chimneys ) in the T array. The T metals in all of the superstructures form a (3-Sn-like array (see Chapter 7) with the number of T metal atoms in the formula of the compound corresponding to the number of (3-Sn-like pseudo-cells stacked in the c direction of the super-cell. The arrangement of the atoms in these phases can be compared to that found in the structure of TiSi2. 

The use of chlorate or perchlorate oxidizers (KCIO 3> KC10 , etc.) is one way to introduce chlorine atoms into the pyrotechnic flame. Another method is to incorporate a chlorine-rich organic compound into the mixture. Table 7.8 lists some of the chlorine donors commonly used in pyrotechnic mixtures. A dramatic increase in color quality can be achieved by the addition of a small percentage of one of these materials into a mixture. Shimizu recommends the addition of 2-3% organic chlorine donor into compositions that don t contain a metallic fuel, and the addition of 10-15% chlorine donor into the high temperature mixtures containing metallic fuels [11]. 

Clearly, U is the biggest number in the cycle and is the main driving force for the formation of ionic compounds. Nevertheless, the other factors can tip the balance one way or another. For example, AHSub is particularly large for the transition metals niobium, tantalum, molybdenum, tungsten, and rhenium, with the result that, in their lower oxidation states, they do not form simple ionic compounds such as ReCl3 but rather form compounds that contain clusters of bonded metal atoms (in this example, Re3 clusters are involved, so the formula is better written ResClg). 

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