Main group elements halogens

In order to prepare hydrolytically stable polythionyiphosphazenes the perchlo-rinated polymers were reacted with nucleophiles to substitute the hydrolytically sensitive main group-element halogen bonds [2]. This type of post-polymerization structural modification is well-established in polyphosphazene chemistry [2,8]. Thus, aryloxide nucleophiles or primary amines were used to substitute the polymers leading to poly(aryloxythionylphosphazenes) 24 and poly(amino-thionylphosphazenes) 25 respectively [35,37] ... 

Boranes also form derivatives ia which main group elements occupy a bridging position between two boron atoms, rather than a polyhedral vertex. An extensively studied system is -R MB Hg, where R = H, CH, C2H3, halogen, and M = Si, Ge, Sn, Pb (185). The stmcture of l-Br- J.-[(CH3)3Si]-B3H2... 

Derivatives of the boranes include not only simple substituted compounds in which H has been replaced by halogen, OH, alkyl or aryl groups, etc., but also the much more diverse and numerous class of compounds in which one or more B atom in the cluster is replaced by another main-group element such as C, P or S, or by a wide range of metal atoms or coordinated metal groups. These will be considered in later sections. 

Some of the columns of main group elements have long been designated by common names (e.g., the halogens) names for others have been suggested, and some have been used more frequently in recent years ... 

The photodetachment threshold values for Ga, As, and Pb (0.30(15), 0.81(3), and 1.10(5) eV, respectively) were determined by an older photodetachment technique [30]. The PES values for Ga, 0.43(3), and As, 0.814(8), are more precise, but are supported by the PD values [31, 32]. The PES value for Pb, 0.364(8), is significantly lower than the PD value, 1.10(5) eV. The photodetachment values for the majority of the other main group elements have also been confirmed by photoelectron spectroscopy. The values for the halogens have been determined by most methods photodetachment thresholds, photoabsorption, ion pair photodissociation, relative and absolute surface ionization methods, and the Born Haber cycle. Values for H, Li, C, F, Cl, Cu, Ge, Br, Nb, Ag, Sn, I, W, Re, Au, and Pb have also been determined by relative and absolute surface ionization methods, as shown in Table 8.2. 

---