Synthesis and electrophile-induced disproportionation of the neutral formyl triphenylphosphinenitrosyl-.eta.-cyclopentadienylrhenium formyl ((.eta.-C5H5)Re(NO)(PPh3)(CHO))

Declining domestic crude oil reserves have prompted a renewed interest in the chemistry of CO/H/sub 2/ gas mixtures (''synthesis gas''), which are readily available from coal and can be transformed by metal catalysts into a variety of organic molecules normally derived from petroleum. In particular, work in numerous laboratories is being directed at the development of milder and/or selective CO reduction catalysts and the delineation of CO reduction mechanisms. The authors have attempted to systematically synthesize homogeneous transition-metal complexes containing uncommon single-carbon ligand types (-CHO, =CHOH, -CH/sub 2/OH, /sup 4/-C, =CH, =CH/sub 2/, etc.) which are considered to be plausible intermediates in CO reduction. By study of their basic chemistry, we have sought to gain insight into possible catalyst reaction pathways. Catalyst-bound formyls are believed to be initial intermediates in the conversion of CO/H/sub 2/ gas mixtures to oxygen-containing organic productsThe objective was to prepare a crystalline, analytically pure nuetral formyl complex whose physical and chemical properties could be subjected to unambiguous definition. In this paper, they describe (a) the attainment of this goal in the synthesis of the neutral formyl (e -C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(CHO), (b) remarkable low-temperature transformations of (e -C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)-(CHO) which result in formylmore » ligand disproportionation, and (c) independence syntheses of several intermediates in these disproportionations. These include ((e -C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(CH/sub 2/))/sup +/ and ((e -C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(CHOH))/sup +/ salts, which are the first isolable electrophilic methylidene and hydroxy methylidene complexes, respectively. As noted above, -CH/sub 2/ and -CHOH ligands may also be important intermediates in catalytic CO reduction.« less