19457-84-2Relevant academic research and scientific papers
Reduktive Aktivierung des Metallaheterocyclobutadienkomplexes Fe(CO)3
Faessler, Th.,Huttner, G.,Guenauer, D.,Fiedler, S.,Eber, B.
, p. 409 - 428 (2007/10/02)
The compound Fe(CO)3 (1a) may be described as an Fe(Co)3 derivative of a 1,2-ferrathiacyclobutadiene ligand.The CO groups of 1a, which are very difficult to substitute by thermal activation. are readily exchanged when compared with P(OMe)3, by reductive electrocatalysis.Reductive initiation of substitution is also possible by the reduction of 1a with Na/Hg or t-BuLi.The mechanism of the reductively-initiated formation of the products 1b and 1c, in which one or two carbonyl groups, respectively, of 1a are replaced by P(OMe)3 as well as the formation of a monosubstituted derivative of 1a, in which an axial CO group of the heterometallacyclobutadiene ligand is replaced by tBuP(OMe)2 (1d) is discussed with respect to electrochemical, spectroscopic and structural data. tBuLi can activate 1a not only by single electron transfer: the addition of tBu- at the sulfur center of 1a leads to an anionic CI-insertion product, which,by subsequent alkylation, may be trapped as Fe(CO)34-(CO)3(t-Bu)> (2b).Insertion of CO in 1a is also initiated by Na/Hg reduction; oxidative work up with I2 gives Fe(CO)34-(CO)3>(3).Thermal activation readily decarbonylates 3 to give 1a.The individual results are consistently described in a common reaction scheme.The structures of 1d, 2 and 3 have been determined by X-ray diffraction studies.
Reactivity of Fe(CO)4(H)MPh3 (M = Si, Ge) and mechanism of substitution by two-electron-donor ligands: Implications for the mechanism of hydrosilylation of olefins catalyzed by Fe(CO)5
Bellachioma, Gianfranco,Cardaci, Giuseppe,Colomer, Ernest,Corriu, Robert J. P.,Vioux, André
, p. 519 - 525 (2008/10/08)
cis-Fe(CO)4(H)MPh3 (M = Si, Ge) complexes undergo carbonyl displacement with nucleophilic ligands (phosphines, phosphites) to give Fe(CO)3(H)(L)MPh3. With M = Si the geometry of these complexes depends on the nature of the solvent; in nucleophilic solvents the mer-OC-6-43 isomer is formed, while in nonnucleophilic solvents the mer-OC-6-23 isomer is obtained (the cis positions of H and Si are retained). These two isomers undergo concerted reductive elimination of silane with PPh3. The mer-OC-6-43 isomer reacts 183 ± 19 times faster than the mer-OC-6-23 isomer in toluene at 26.0°C, giving the same 16-electron intermediate; the calculated equilibrium constant for the interconversion of OC-6-43 and OC-6-23 is 823 ± 192 at 26.0°C in toluene. Owing to the strong acidity of Fe(CO)4(H)MPh3 (pKa estimated as 3CN) and of Fe(CO)3(H)(PPh3)MPh3 (pKa estimated as ≤8.94 in CH3CN), reaction with basic two-electron-donor ligands [P(alkyl)3, P(cycloalkyl)3, NR3] leads to the formation of the anionic trigonal-bipyramidal complexes [Fe(CO)4MPh3]- and [Fe(CO)3(L)MPh3]-. cis-Fe(CO)4(H)SiPh3 reacts with isoprene to give [Fe(CO)4SiPh3]2; this reaction is not observed with Fe(CO)3(H)(L)SiPh3. The versatile reactivity of these complexes sheds some light on the mechanism of hydrosilylation of olefins and conjugated dienes. Under thermal conditions previous coordination of the olefin to the metal in this reaction seems to be excluded.
