Acknowledgments. The authors thank the National Science Foundation for a grant in partial support of this work, and the National Institutes of Health for a Predoctoral Fellowship to S. WT They are indebted to Dr. Paul von R. Schleyer for crucial advice early in this work, and to Miss Carol Gross and Mr. Gary Krejcarek for carrying out several large-scale syntheses of pentachlorocyclopropane. ... Stephen W. Tobey and Robert West Contribution from the ...