PHOTOCHEMICAL SUBSTITUTION-REACTIONS OF GROUP-6B METAL TETRACARBONYL NORBORNADIENE COMPLEXES WITH (CO)-C-13, KINETICS OF SUBSEQUENT THERMAL REARRANGEMENTS IN STEREOSPECIFICALLY LABELED SPECIES, AND RELATIONSHIP OF THESE RESULTS TO PHOTOINDUCED HYDROGENATION PROCESS
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Photochemical substitution reaction ( >2800 ) of M(CO)4(NBD) (M=Cr, Mo, W and NBD=norbornadiene) with 13 CO have been shown via infrared spectroscopy, coupled with 13C NMR, to occur with preferential loss of an axial CO ligand. Further rearrangement of the stereospecifically 13 CO labeled M(CO)4(NBD) species results upon thermal and/or photochemical activation. A mechanism for this rearrangement in the tungsten derivative has been proposed based on kinetic measurements (both for the rearrangement process and diolefin substitution with phosphines) which involves cleavage of one metal-olefin bond, followed by a Berry permutation. The results of thermal and photochemical hydrogenation of norbornadiene in the presence of group 6b hexacarbonyls are explained employing CO dissociation as well as metal-olefin bond cleavage. 1977, American Chemical Society. All rights reserved.