Generation and EPR Spectroscopy of the First Silenyl Radicals, R₂C=Si^.−R: Experiment and Theory

Abstract

The first two persistent silenyl radicals (R 2 C=SiCÀR), with ah alf-life (t 1/2 )o fa bout 30 min, were generated and characterized by electron paramagnetic resonance (EPR) spectroscopy. The large hyperfine coupling constants (hfccs) (a( 29 Si a ) = 137.5-148.0 G) indicate that the unpaired electron has substantial scharacter.D FT calculations,w hich are in good agreement with the experimentally observed hfccs, predict as trongly bent structure (]C=SiÀR = 134.7-140.78 8).In contrast, the analogous vinyl radical, R 2 C = CC À R(t 1/2 % 3h), exhibits asmall hfcc (a( 13 C a ) = 26.6 G) and has anearly linear geometry (]C = C À R = 168.78 8).