Evidence for enhanced reactivity in the photofragmentation of the bridged dinuclear system Me 2Si[η 5-C 5H 4Fe(CO) 2(η 1-CH 2C 6H 5)] 2

Abstract

Experimental evidence that the dinuclear complex Me 2Si[η 5-C 5H 4Fe(CO) 2-(η 1-CH 2C 6H 5)] 2 shows enhanced reactivity over its mononuclear analogy η 5-C 5H 5Fe(CO) 2(η 1-CH 2C 6H 5 in photogragmentation to produce bibenzyl and FeFe bonded product is presented. Information from a series of competition and crossover experiments indicate that two factors are involved in the enhancement: (1) the ability to photochemically produce a 16-electron unsaturated benzyl unit in close proximity to a saturated partner, and (2) the inability of the FeFe bonded species 4 to quench free benzyl radicals in solution. Chemical reaction of Me 2Si[η 5-C 5H 4Fe(CO) 2(η 1-CH 2C 6H 5)] 2 with Me 3NO produces bibenzyl and establishes that loss of CO is the initial step in the fragmentation reaction. In addition, trapping experiments with 9,10-dihydroanthracene show that bibenzyl is formed from free benzyl radical; BBased on these results an overall mechanism is proposed.