The metal-catalyzed reduction of CO by H2 can lead to methane, methanol, and higher alkanes and alcohols.'-3 In view of the ready availability of CO/H2 gas mixtures from coal, these transformations are likely to be of increasing economic importance. To organic chemists, these reactions constitute the primordial steps in solving the classically posed problem of total synthesis from "earth, fire, and water". The initially formed intermediate in CO reduction is believed to be a metal-bound formyl. 2,4 We report herein the preparation of a new series of reactive anionic metal formyl complexes from Li(C2H5)3BH and metal carbonyl acyls, L,M(CO)(COR), and the formation of alcohols upon their decomposition. Trialkylborohydrides and related hydride donors have been previously reported by ourselves, ' Casey,6 and Winted to yield anionic metal formyl complexes when reacted with simple metal carbonyls or phosphine substituted derivatives. This study establishes the more widespread applicability of this technique, and suggests a kinetic preference for hydride attack at coordinated carbon monoxide over metal-bound acyl groups. To -50ยฐC THF solutions of the manganese, iron and molybdenum carbonyl acyls depicted in Table I were added 1.2 equiv Li(C2H5)3BH. New 'H nmr signals were detected in the 6 12.40-13.10 range and ascribed to products 1-S These chemical shift values have been previously established as characteristic cf anionic metal for-my1 complexes, 5-7 and in the case of l-8 are extremely temper--ature dependent. Yields were measured relative 1,2,4,5-tetrachlorobenzene internal standard. The fOrmy complexes l-8 are all unstable at room temperature,and although repeated isola--tion attempts failed,ir spectra were obtained for l_, 2, and 5 _. All exhibit medium intensity for-my1 vczo absorptions , and the manganese complexes are cis geometrical isomers (THF, cm -l: 1: 2050 (w), 1949 (s), 1933 (s), 1884 (m), 1588 (w,br); 2: 2055 (m), 1962 (s), 1929 (s), l;f3 (w), 1604 (m); 5: 1932 (s), 1555 (m)). Under optimized experimental conditions, only broad C nmr-resonances barely above baseline could be tentative, THF/C6D6, -4O"C), although nances were routinely detected. obtained for metal-bound carbons (5: ca. 297, 293, 221 ppm, -broadened arene, cyclopentadienyl, and alkyl carbon reso-319