Conversion of a bridging methylene ligand to a ketenylidene moiety. Synthesis and reactivity of carbomethoxymethylidynenonacarbonyldihydrotriosmium

Carbidocarbonyl clusters of iron

“…1979) that the reaction between alcohols (and amines) with Fe4C(CO)13 may proceed via a ketenylideneintermediate Fe4(CO)12: C: CO. Although there is no direct evidence for this, the reactions of H2Os3(CO) 10CCO and Co3(CO)9-CCO+ with alcohols to give H30 s3(C 0 )12C *C 02R (Sievert al. 1982) and Co3(CO)9C C 0 2R (Seyferth et al 1974) provide support for this route.…”

Synthesis and asymmetric reactivity of enantiomerically pure cyclopentadienylmetal complexes derived from the chiral pool

“…A more specific goal was to gain access to structures in which the chiral framework either was relatively bulky or was annelated to the fivemembered ring, thus providing a perhaps advantageous more encumbered and/or rigid asymmetric environment to the metal. As a convenient test for their utility, applications in enantioselective titanocene-catalyzed hydro-genations7 were envisaged, in addition to the novel exploitation of (?j5-cyclopentadienyl)cobalt complexes as mediators of similarly selective carbon-carbon bond formations in [2 + 2 + 2] cycloaddition reactions of alkynes to other unsaturated moieties.8 Toward these ends, we describe herein the efficient syntheses of 3 (three steps, 36% yield from phenylmenthone), 4 (five steps, 37% yield from camphor), and 5 [one step, 31% yield from threitol bis (4-methylbenzenesulfonate) ]. Metalation of these ligands led to chiral titanocene dichloride and (i75-cyclopentadienyl)dicarbonylcobalt complexes whose activity in enantioselective transformations was tested.…”

“…Results and Discussion Synthesis of 3. On the basis of the report that cyclopentadienes 1 and 2 were accessible by introducing the (5) For a preliminary report, see: Halterman, R. L; Vollhardt, K. P. C. Tetrahedron Lett. 1986Lett.…”

“…At 0 °C 10 (0.990 g, 3.00 mmol) in THF (10 mL) was introduced dropwise into the reaction solution. This mixture was stirred at this temperature for 30 min and for 12 h at room temperature and then heated at reflux for 2 h. Acidic (HC1) aqueous workup yielded a yellow oil (0.947 g) that was purified by flash chromatography (hexanes) to provide 3 as a colorless oil (0.386 g, 45.9%) as a mixture of cyclopentadiene double-bond isomers: IR (thin film) 3060, 2952, 2915,1603,1497,1456,1370,1034,900,765,702 cm-1; MS, m/z (relative intensity) 280 (M+, 7), 154 (8), 119 (100), 105 (14), 91 (59), 79 (25), 67 (14); NMR (250 MHz, CDClg) 7.05-7.40 (m, 5 H), 6.38 (br s, 0.3 H), 6.34 (br s, 0.6 ), 6.19 (br s, 1.4 ), 5.91 (br s, 0.7 H), 2.79 (br s, 1.4 H), 2.35-2.75 (m, 1.6 ), 1.86 (m, 1 ), 1.35-1.75 (m, 4 ), 1.30 (m, 1 ), 1.27 (s, 3 ), 1.16 (s, 3 ), 0.90-1.15 (m, 2 ), 0.86 (d, J = 6.4 Hz, 3 H). Anal.…”

[PPN][Fe3(CO)9(C⋮CH)] and [Fe3(CO)9(C⋮COTi(THF)4Cl)] from the Reaction of Low-Valent Titanium with [Fe3(CO)9(CCO)]2-

“…Reaction of the McMurry Reagent. Reaction of the low-valent titanium compound with Ru 3 (CO) 12 , [PPN] 2 [Ru 3 (CO) 9 (CCO)], [PPN] 2 [Os 3 (CO) 9 (CCO)], and [PPN] 2 [Ru 6 (CO) 16 C] leads to the formation of the known hydride compounds [H 4 Ru 4 (CO) 12 ], [H 2 Ru 3 (CO) 9 (CCO)], [H 2 Os 3 (CO) 9 (CCO)], and [H 2 Ru 6 (CO) 16 C], respectively, presumably through H abstraction from the solvent or from adventitious water. Apparently, the basic nature of these clusters leads to the formation of hydrides.…”