Synthesis and reactivity of metal .alpha.-hydroxyalkyl complexes; generation of (CO)5MCH(C6H5)OH (M = Mn, Re)

Ring Closure of Alkoxycarbonyl(tetracarbonyl)pyruvoyliron Complexes into Metallalactones Induced by Nucleophilic Attack of Carbanions

“…The coordination polyhedron at the metal center is a distorted octahedron built of three terminal carbonyl ligands, an alkoxycarbonyl, and the chelating carbonylated ligand. As observed for neutral metallalactones [7,10,12,13] and for five-membered iron metallacycles, [17] the bite angle of the chelate C(7)-Fe-C (6) [18] Therefore, its opposite angle on the metal [C(1)-Fe-C(2)] displays a larger value than that expected for an octahedral geometry with values close to 90°. The Fe-terminal carbonyl distances [1.79(1)-1.90(1) Å] are similar to those in the homologous trifunctionalized iron monoanion [9] or to the neutral complex [(CO) 4 Fe(CO 2 tBu) 2 ] [18] but are longer than the Fe- (8) 114.0(9) 112.1(9) 112.5(8) O7-C7-C8 115.0 (9) 117 (1) 118 (1) 117(1) O8-C8-C7 107.6 (8) 108.6(9) 110(1) 110 (1) CϵO distance observed in a monofunctionalized iron anion.…”

“…In this paper, hydride was reported to attack the β carbonyl of a ligand of [(CO) 5 Mn{C(O)C(O)C 6 H 5 )}] to afford an anionic metallalactone by cyclization of the phenylglyoxyl with a terminal carbonyl. [12] These results prompted us to perform the cyclization of 1 with anionic nucleophiles (RO -, RS -, or R 2 P -). [13] These reactions, as they only afford two isomers of the anionic trifunctionalized metallalactone 3 (Scheme 1, c), also suggested that the formation of the metallalactonic ring could indeed proceed by addition to a terminal carbonyl rather than to the alkoxycarbonyl ligand.…”

Thermal properties and reactions towards nucleophiles of an iron complex displaying an acetyl and a pyruvoyl ligands

“…The formation of 3 in very low yield by reaction of the neutral lactones 2 with CH 3 O À suggested the mechanism 2b as the most probable pathway of the reaction. This assumption was reinforced by the description, in the literature, of an hydride induced cyclisation of a phenylglyoxyl ligand on a terminal carbonyl of a manganese complex [9]. To confirm the possible formation of a metallalactone ring by addition of the pyruvoyl ligand on a terminal carbonyl, it seemed appropriate to perform the reaction on (pyruvoyl)(carbonyl)iron complexes which did not display ligands with labile groups.…”

Manganese Alkyls and Hydrides

“…Attempts to prepare a-hydroxyalkyl manganese compounds such as (38) via the path shown in Scheme 6 resulted in the formation of MnH(CO) 5 and benzaldehyde. 59 Thus, at least in this case and probably generally, the metal hydride to a-hydroxyalkyl metal equilibrium is observed to lie in the direction of the metal hydride plus aldehyde. However, when the aldehyde was appended in a phosphine ligand, chela tion stabilized the a-hydroxyalkyl complex (39) (Scheme 7).…”

“…61 Enough thermodynamic driving force for the insertion of CO is apparently generated by the strong Si-0 bond in (58) to form its threemembered ring, as shown in Equation (21). 83 Subsequent removal of the silyl group by chromatography on wet silica gel reveals that the equilibrium between (59) and (60) lies towards the open-chain acyl. …”