The Delta E(X) - Delta C-X substituent constant analysis is extended to several physicochemical properties of XCo(DH)(2) complexes (DH = dimethylgloximate), to the coordination and alkene-metal hydride insertion rates of substituted styrenes into Cp(2)NbH and Cp(2)*NbH, to the reactions of X(3)SiH with Cr(CO)(5), and to the reactions of X(3)SiCH = CH2 with carbenes. In addition to providing insights about the steric, pi-bonding and normal sigma-bond interactions influencing the physicochemical property, important generalizations result about the mechanism of substituent influences on the fundamental donor-acceptor interactions influencing this chemistry. In addition, the d(E) and d(C) parameters, the counterparts of rho in single scale treatments, permit one to select the best substituent to optimize the property.