Group homonuclear

The electron affinities of the main group homonuclear diatomic anions have been measured by PES. A few experimental values for the transition metal dimers are also available. The electron affinities of all the 3d homonuclear diatomic molecules have been calculated using density functional methods [1-4], Only the AEa of I2, 2.524 eV C2, 3.27 Si2, 2.2o S2, 1.67 F2, 3.0g Cl2, 2.4s Br2, 2.5, and 02, 1.07 have been measured by more than one method [1-3]. CURES-EC calculations confirm these to within 0.1 eV. Positive excited states Ea have been measured for 02, C2, and I2 and are inferred for other X2 [5-8]. Just as in the case of the atomic Ea, the trends in the Periodic Table can support the assignments of AEa for the other elements. 

TABLE A1.2 Main Group Homonuclear Diatomic Molecules (in eV) ... 

In a coupled spin system, the number of observed lines in a spectrum does not match the number of independent z magnetizations and, fiirthennore, the spectra depend on the flip angle of the pulse used to observe them. Because of the complicated spectroscopy of homonuclear coupled spins, it is only recently that selective inversions in simple coupled spin systems [23] have been studied. This means that slow chemical exchange can be studied using proton spectra without the requirement of single characteristic peaks, such as methyl groups. 

Figure 4.11j), for example, and all homonuclear diatomic molecules belong to this point group. 

The remainder of this chapter covers reactions by which homonuclear bonds between the group-IIIB elements are formed and includes a few examples of heteronuclear bonds, e.g., B—Al and Ga—In in compounds of these elements. 

Hertwig, R. H., Koch, W., 1995, On the Accuracy of Density Functionals and Their Basis Set Dependence An Extensive Study on the Main Group Element Homonuclear Diatomic Molecules Li2 to Br2 , J. Comput. Chem, 16, 576. 

H. G. v. Schnering, Homonuclear bonds with main group elements. Angew. Chem. Int. Ed. 20 (1981) 33. 

II. Homonuclear Multiple Bonding Involving the Heavier Main Group 3... 

HOMONUCLEAR MULTIPLE BONDING INVOLVING THE HEAVIER MAIN GROUP 3 ELEMENTS... 

The first-row homonuclear diatomic molecules A2 of main-group elements (A = B, C, N, O, F) exhibit a well-known diversity of ground-state multiplicities, bond lengths, and bond energies. Calculated potential-energy curves for low-lying singlet and triplet states of these species are pictured in Fig. 3.27 and summarized in Table 3.13 (with comparison experimental values). Because these homonuclear... 

In Table II are listed the neutral homonuclear carbonyls of the Group VIII metals that have been identified to date. Although palladium and platinum do not have any stable neutral carbonyls, a large... 

M R 3 compounds of group 13 elements yielded mixed-valence compounds of the general type RM-M R 3,321 which are valence isomers of M2R4 (Section 3.07.4.1). To date, several homonuclear and heteronuclear species have been synthesized and structurally characterized and their stability was investigated by computational calculations (Table 2).322 322a 323... 

The use of bulky organic groups permitted the isolation of several thermally stable compounds containing double bonds between arsenic, antimony, or bismuth.8 9 56 Examples of homonuclear dimetal compounds, that is, diarsenes,... 

Bare group 13 metal vertices (e.g., Ga, In, Tl) provide, as noted above, only one skeletal electron each to polyhedral cluster structures. Thus it is not surprising that the bare metal cluster ions Enz (E = group 13 element) found in homonuclear alkali-metal/group 13 intermetallic phases [86-89] (mainly for In and Tl) have charges less negative than the — (n + 2) (i.e., z [Pg.21]

One of the first published cluster compounds of the heavier group 13 elements was the closo-dodecaaluminate K2[Ali2iBui2] 54 (Figure 2.3-10) [79], which possesses an almost undistorted icosahedron of 12 aluminum atoms with short Al-Al distances (268-270 pm). Up until today, it remained the only homonuclear cluster compound of the elements aluminum to indium which, with respect to structure and cluster electron count, is completely analogous to any boronhydride (see Chapters 1.1.2, 1.1.3, 1.1.5.2, and 2.1.5.6) (in this case doso-[Bi2H12]2 ). Compound 54 was formed in small quantities by the reaction of di(isobutyl)aluminum chloride with potassium and was isolated as dark red crystals (Figure 2.3-10). 

Homonuclear clusters of the heavier elements of the third main-group aluminum, gallium, indium and thallium having direct element-element interactions form a fascinating new class of compounds. As discussed in the previous Chapter 2.3, in some cases their structures resemble those known with the lightest element of that group, boron, while in other cases novel, metal-rich compounds were obtained which do not have any analogue in boron chemistry. 

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