Über Cyclopentadienyl‐metall‐carbonyl‐wasserstoffe des Chroms, Molybdäns und Wolframs

Abstract

In Bestätigung des Bildungsgesetzes der Mono‐cyclopentadienyl‐metall‐carbonyle gelang die Darstellung von leicht flüchtigem, diamagnetischem, gelbem (C5H5)Cr(CO)3H. Homologes (C5H5)Mo(CO)3H und (C5H5)W(CO)3H schließen sich ihm an. Alle drei Hydride sind schwache, in wässerigen Alkalien lösliche Säuren, diejenigen des Cr und Mo neigen zur H‐Abspaltung unter Dimerisierung der verbleibenden Radikale. (C5H5)W(CO)3H läßt sich mit Diazomethan zu stabilem, leicht flüchtigem, orangem (C5H5)W(CO)3CH3 umsetzen.

Das Radikal Cp(CO)3Cr in Lösung/The Radical Cp(CO)3Cr in Solution

“…Dies wurde schon bei seinen ersten Untersuchungen durch E. 0. Fischer et al [1][2][3] mit der Vermutung in Zusammenhang gebracht, daß es die monomeren Radikale 2 bildet. Indirekte Hinweise auf diese Radikale ergaben sich aus dem Massenspektrum [4] und weiteren Umsetzungen [5] von 1.…”

Supported cyclopentadienylmetal carbonyl complexes

“…Similar spectra, resembling those of CsHsM(COhH derivatives, are obtained for the corresponding chromium and molybdenum compounds (Table 1). The molybdenum derivative is formed by substitution of !\,10(CO)6 faster than the derivatives of the other two metals and a molybdenum content of 4.5% (4.7 mmol Mo per g of polymer or about one cyclopentadienylmolybdenum unit per 20 styryl units) is obtained afteI only 4 h. An increased reactivity of MO(CO)6 in comparison to Cr(CO)6 and W(CO)6 has been observed by Fischer et ale [3] in related substitution reactions with CsHs-. The polymersupported metal compounds were further characterized by thermoanalytical studies.…”

“…Group VI transition metal tricarbonyl species are introduced to a polymer network by treatment of polystyrylmethylenecyclopentadienyl * anion, [2] (PS)-CHz--CsH;-, containing about 1.5 mmol CsH'; per g of polymer, with chromium, molybdenum or tungsten hexacarbonyl, in dimethyl formamide at 130°C [3], subsequent removal of excess hexacarbonyl, and acidification with acetic acid.…”

Alkali and Alkaline Earth Metal Complexes Ligated by an Ethynyl Substituted Cyclopentadienyl Ligand

“…They have been used for the synthesis of countless cyclopentadienyl complexes. Potassium cyclopentadienyl (KCp) was first reported by J. Thiele, who reacted potassium and cyclopentadiene in benzene [1], while the analogous sodium cyclopentadienyl (NaCp) was discovered approximately 50 years later by the groups of E. O. Fischer [2,3] and K. Ziegler [4]. The alkali metal cyclopentadienyls are generally available either by deprotonation of cyclopentadiene with an alkali metal base such as M{N(SiMe 3 ) 2 }, MH, MOtBu, MOH or the alkali metal itself [5,6].…”

“…Furthermore, other derivatives of cyclopentadienyl are easily accessible and increase the versatility of the cyclopentadienyl ligand [10][11][12]. For this reason, we became aware of the ligand trimethysilylethynyltetramethylcyclopentadiene CpMe 4 (C≡CSiMe 3 )H. CpMe 4 (C≡CSiMe 3 ) − has been used before in group 8 chemistry. The postmodification of η 5 -CpMe 4 (C≡CSiMe 3 ) − metal complexes may include access to metal acetylides [13,14], metal alkyne complexes [15,16], Sonogashira couplings [17][18][19], click reactions [20,21] and cyclizations [22][23][24].…”