Intermolecular Electron-Transfer Reactions Involving Hydrazines

The self-exchange electron-transfer (ET) rate constant k 22 for 1,2,3,4,5-pentamethylferrocene was determined by NMR line broadening to be 8.5(±0.8) × 10 6 M - 1 s - 1 (25 °C, CD 3 CN/0.09 M Et 4 NBF 4 ) and k 11 for the bis-N,N-bicyclic hydrazine, 9,9‘-bi-9-azabicyclo[3.3.1]nonane, to be 8.7(0.5) × 10 3 M - 1 s - 1 (25 °C, CH 2 Cl 2 ). These self-exchange rate constants are used to analyze cross reactions of these molecules with hydrazines, ferrocenes, and tetramethyl- p -phenylenediamine ( TMPD ) using Marcus theory. Cross-reaction rate constants for eight reactions are reported. Included are six cross-reactions between methylferrocenes and four cyclic hydrazines, one hydrazine, hydrazine−reaction, and the reduction of TMPD + by a cyclic hydrazine. These are the first cross-reaction rate constants reported for hydrazine−hydrazine and hydrazine− TMPD + ET reactions. The cross-reaction rate constants are used to test the application of Marcus theory to hydrazine ET reactions and to extract estimates of hydrazine self-exchange ET rate constants in systems for which direct measurement is presently impossible.