Alkyls bulky, special stability

The nomenclature of the RP is not consequent. The RP most often used contains octyl (RP C8) or octadecyl (RP C18) groups. There is no differentiation even when two methyl groups are introduced additionally with the silane (as with monofunctional silanes) or only one (difunctional) or none (trifunctional silane). Some manufacturer use silanes with bulky side groups (e.g., isopropyl groups) to improve the hydrolytic stability of the bonded phases, but here also, only the longest alkyl group is used in nomenclature. RP C8 and RP C18 are the work horses in HPLC. Shorter chains (RP4) are used in protein separations, and special selectivity can be obtained with bonded phenyl, cyano, amino or fluoro groups. 

Introduction of bulky ligands is a general way to stabilize organometal-lic complexes. They slow associative decomposition pathways, including reaction with the solvent or with another molecule of the complex, that are specially important for 16e metals. For example, square planar Ni(II) alkyls are vulnerable to attack along the z direction perpendicular to the square plane. The di-o-tolyl complex 3.15, in which this... 

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