Trogler and F. Basolo for sending us a preprint of their paper3* prior to publication, the National Science Foundation for financial support, and the United States-France (NSF-CNRS) cooperative program for an award of a fellowship to CA Registry No. q5-MeCpMn(C0)2(4-MeOpy)+, 89727-37-7; q5- MeCpMn(CO),(4-NO2py)+, 89727-38-8; q5-MeCpMn(C0),(4-Mepy)+, 89727-44-6; q5-MeCpMn(C0)2(py)+, 89727-45-7; q5-MeCpMn(C0),- (4-CH3COpy)', ...