R. A. Fiato

Rate-structure studies of the carbonylation and decarbonylation of substituted metal carbonyl complexes☆

Abstract The rate of CO insertion for the following complexes have been determined: RCH 2 Mn(CO) 5 where R  cyclohexyl, hydrogen, phenyl, methoxy, and carboxyl; RCH 2 Fe(CO) 4 − where R  cyclohexyl, n-octyl, n-heptyl, and phenyl. It appears that a Taft σϱ correlation can be established for this reaction. Rate data for the decarbonylation reaction of an analogous series of substituted manganese carbonyl complexes (RCH 2 COMn(CO) 5 ) was also obtained. As in the case of the CO insertion reaction, the rates increase as the Taft σ for RCH 2 decreases. The linear free energy relationships (LFER) generated in this study have been used to predict the relative probability of several reaction steps that have been postulated for the conversion of carbon monoxide and hydrogen into ethylene glycol.

Carbon monoxide hydrogenation, preparation and characterization of model compounds

Abstract Polynuclear rhodium carbonyl complexes are present during the rhodium catalyzed conversion of carbon monoxide and hydrogen to alcohols. High pressure f.t.-i.r. analyses of reaction solutions containing [Rh17(CO)32-(S)2]3− suggest a catalyst manifold composed, almost exclusively, of that cluster. A related complex, [Rh17(CO)32−n(S)2(CHO)n](3 + n)−, has been prepared. The reactions of LiBH(C2H5)3 and LiBD(C2H5)3 with Os3(CO)12, Ru3-(CO)12, Ir4(CO)12, and Rh4(CO)12 have been studied by i.r., 1H and 2H n.m.r. and 13C n.m.r. With the exception of the rhodium containing system, results suggest the formation of formaldehyde and methanol in these reactions, as well as the existence of previously unreported polynuclear transition metal formyl complexes. Formyl complexes have been implicated as key intermediates in the manganese or cobalt catalyzed conversion of carbon monoxide and hydrogen to methanol. Mass spectral studies suggest that the reaction of acetic [13C] formic anhydride with sodium pentacarbonylmanganate, to give 13CO substituted pentacarbonylmanganese hydride, proceeds via formation of a short-lived neutral formyl complex, (CO)5Mn−13CHO.

Formyl complexes of transition metal carbonyl clusters : II. Spectroscopic study by 2H NMR of the synthesis of [Ir4(CO)12-x(CHO)x]x−, [OS3(CO)11(CHO)]− and [Ru3(CO)11(CHO)]− (x = 1,2)☆

Abstract The reactions of LiHB(C2H5)3 and LiDB(C2H5)3 with Re2(CO)10, Ir4(CO)12, Os3(CO)12, Ru3(CO)12 and Rh4(CO)12 have been studied by 1H, 2H and 13C NMR techniques. Results suggest the formation of formaldehyde and methanol in these systems, as well as the existence of previously unreported formyl complexes. A 2H isotope effect is noted in the apparent increase in stability of cluster formyl complexes.

Metal formyl complexes. Hydride transfer to group VIII transition metal carbonyl clusters

Abstract The reaction of LiBH(C 2 H 5 ) 3 with Os 3 (CO) 12 or Ir 4 (CO) 12 leads to the formation of spectroscopically detectable formyl complexes. In the latter case, the complex is smoothly converted to [Ir 4 (CO) 11 H] − , an expected decompositioFn complex of the corresponding polynuclear formyl complex, [Ir 4 (CO) 11 CHO] − .

Rhodium Carbonyl Clusters with Encapsulated Main-Group Atom(s). Structures and Reactivity

Homogeneous catalysis by transition metal clusters is attracting increasing attention, (1,3) as well as the modeling of some heterogeneous catalysts by these complexes. (4) Cluster catalysis in homogeneous systems has been reported for some technologically relevant reactions such as hydr formylat ion, (5) water-shift, (6) oxidation (7) and Fisher-Tropsch. (8) In addition, rhodium carbonyl clusters are present during the catalytic synthesis of alcohols from carbon monoxide and hydrogen.(9)

Metal formyl complexes. The reaction of sodium pentacarbonylmanganate with acetic[13C]formic anhydride

The reaction of acetic [13C]formic anhydride with sodiumpentacarbonylmanganate proceeds rapidly at 0°C to give 13CO substituted pentacarbonylmanganese hydride as the predominant product. The results are consistent with the formation of a short-lived neutral formyl complex, (CO)5Mn13CHO.