‘Survival Of The Weakest’

The “Survival of the Weakest” article was of great interest, as was the journal article that led to it (C&EN, April 5, page 7; Nat. Chem., DOI: 10.1038/nchem.614).

The principle of survival of the weakest—improved catalysis from the most unstable catalytic intermediate—may explain certain unusual results in homogeneous platinum-catalyzed hydrosilylations, where the catalytic intermediate “ligands” are different platinum-bonded silyl groups. For example, the competitive reaction between triethylsilane and trichlorosilane for methallyl chloride is clearly won by triethylsilane at abnormally high rate, yield, and selectivity (U.S. Patent 4,614,812 or its foreign equivalents, Examples 8,9, plus related reactions).

The noncompetitive triethylsilane/methallyl chloride reaction is very slow. Since the trichlorosilyl-platinum bond is generally regarded to be stronger than other Pt–Si bonds (J. Chem. Soc. A 1970, 881), this reaction may be another example of survival of the weakest, where the selection process is the competitive reaction. In fact, the competitive reactivity order for methylchlorosilanes toward methallyl chloride is dimethylchlorosilane > methyldichlorosilane > trichlorosilane, which is the opposite of the Pt–Si bond strength order.

Curtis L. Schilling Jr.
Marietta, Ohio