Main group derivatives

In summary, the Lewis-like model seems to predict the composition, qualitative molecular shape, and general forms of hybrids and bond functions accurately for a wide variety of main-group derivatives of transition metals. The sd-hybridization and duodectet-rule concepts for d-block elements therefore appear to offer an extended zeroth-order Lewis-like model of covalent bonding that spans main-group and transition-metal chemistry in a satisfactorily unified manner. 

Exo-Bonded Substituents and Other Main Group Derivatives of the 9 Ions. 80... 

Most of the bare main group derivatives of the E9 ions were prepared several years ago by Rudolph and Corbett, whereas the exo-bonded compounds were... 

Table 5 Main group derivatives and exo-bonded derivatives of Group 14 Zintl ions ...

Metallaboranes and metallacarboranes can be classified structurally by a procedure similar to that for boranes and their main group derivatives.30 In this scheme, the valence electron count of the metal-containing fragment is first determined and then compared with the requirements of the 18-electron rule. This fragment can then be considered equivalent to a BH fragment needing the same number of electrons to satisfy the octet rule. For example, a 15-electron fragment... 

Several main group derivatives of boratabenzene have been synthesized through reaction of boratabenzene salts with the appropriate metal halides. For example, treatment of [CsFlsBMelLi with group 14 electrophiles MesEX (E = Si, Ge, Sn, Pb) led to -bonded compounds (139) that are fluxional in solution. In contrast, reaction with divalent group 14 halides ECI2 led to bent-sandwich structures such as the -bonded complex (140). ... 

A most unusual main group derivative is a phosphorous(V) derivative which is probably the least metallic of the metallo species. The structure of the dihydroxo derivative, [P(TPP)(0H)2]0H , has been determined. The average P-Np bond distance is 1.891(19) A and the average axial P-O(OH) is 1.59(7) A. In order to accommodate the very small P cation, the porphyrin core is exceedingly S ruffled with deviations of the meso carbon atoms of 0.80 from the mean plane. 

Compounds containing reactive C-H bonds have been shown to undergo cross coupling in the presence of catalyst and base witliout initial foimation and isolation of a main-group derivative. One classic version of this coupling is the reaction of an aryl halide with... 

Variants at the C-9 substituent can be divided into 3 main groups, derivatives at the C-13 keto function, derivatives at the C-14 hydroxy group and compounds with an inverted configuration at C-9. The only known compounds of the latter type are 7,9-diepimers and these have already been discussed. Before considering the other 2 groups, there are 2 compounds which do not fit into either group, these are the acid (96) formed by periodate oxidation of adriamycin and the... 

An X-ray diffraction study of pentaphenylphosphorus reveals a slightly distorted trigonal bipyramidal structure P—1.987 A P—1.8 50 A, Cgx—P—Cg, 176.9 A. Pentaphenylarsenic is isomorphous, indicating a similar structure. The antimony compound, however, is one of the very few Main Group derivatives to have square pyramidal geometry, both in the solid state and in solution in dichloromethane. The p-tolyl derivative, (T-MeC H lgSb, is trigonal... 

M[N(SiR3)2] can then be purified—for the main group derivatives (for application in the synthesis of alkoxides, see Zn (Goel, 1990), Cd (Boulmaaz, 1992), Pb (Matched, 1990 Papiemik, 1989), Bi (Massiani, 1990 Goel, 1990))—by sublimation direct from the reaction mixture, after removal of the Et20 in vacuum, and—for the early transition metal con tounds (Cr(II), Mn(ll) (Horvath, 1979)), after the removal of ether—by the extraction from the residue with pentane or hexanes, separating LiCl by decantation. It should be mentioned that this approach is hardly practically applicable for the synthesis of the derivatives of late transition metals such as Co, Ni or Cu because of poor stability of their amide derivatives (Bryndza, 1988). 

The only main group derivatives in which NMR appears to have played a role in structure determination are the CF3BF3- anion 54) and in the fluoroalkyl derivatives of tin 64). For CF3BF3, the spectrum revealed coupling... 

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