Toxicity of organometallic compounds: Correlation analysis via substituent constants

Organometallic compounds have many uses in industry, agriculture and in research laboratories, and their toxicity being an environmental hazard. Nevertheless, the influence of the substituents bound to the central atom M on the toxicity and other biological properties BP is poorly understood. In this work, the literature data on substituent influence on the toxicity (the lethal doses LD50 and LDL0) of mercury, boron, silicon, germanium, tin, lead, phosphorus, arsenic, and platinum compounds (27 series) have been analyzed, using the correlation analysis. Such BP as antitumour, fungicidal, and insecticidal activities as well as mutagenicity (4 series) have been considered for comparison. Generally the BP were first established to depend not only on the inductive, resonance, and steric effects but also on the polarizability of substituents which can be characterized by the σα constants. The polarizability effect owes its existence to the appearance of an excess charge on M atom as a result of donor–acceptor interaction organometallic molecule-biological target. The presence or absence of certain effects are governed by the type of series. In most cases the influence of the substituents on BP can be realistically explained only if the polarizability effect is taken into consideration. The knowledge of substituent effects permits a better understanding of factors influencing biological activity of organometallics.