Organochromium π-complexes—VI. The preparation of Cp′(η3-allyl)2Cr compounds and their reactions with donor ligands

(η4-s-cis-1,3-Butadiene)tetracarbonylchromium(0)

“…In the structure of the title complex the Cr-C distances to the terminal carbon atoms of the s-cis-1,3-butadiene ligand are longer compared to the respective distances to the central carbon atoms of the diene ligand. A similar trend to longer Cr-C distances for the terminal carbon atoms was found for example for the s-cis-1,3-butadiene chromium(1) complex [CrCp*(C 4 H 6 )(CO)] (Betz et al 1993). As known from a few other chromium(0) complexes of s-cis-1,3-butadiene and related coordination compounds (Pavkovic & Zaluzec, 1989;Betz et al 1993;Wang et al 1990;Konietzny et al 2010)…”

“…For experimental and theoretical data for the title compound, see: Fischler et al (1976); Kotzian et al (1982); Kreiter & Ö zkar (1978); Okamoto et al (1991); von Ragué Schleyer et al (2000). For related chromium complexes, see: Pavkovic & Zaluzec (1989), Betz et al (1993), Wang et al (1990), Konietzny et al (2010). For related s-cis-butadiene complexes, see: Reiss (2010), Reiss & Konietzny (2002).…”

Accessibility of 17-Electron Structures for Cyclopentadienylchromium(III) Compounds. 2. Cyanide Derivatives with 15- and 17-Electron Configurations

“…The only previously reported example of a half-sandwich 17-electron Cr(III) complex, i.e. CpCr(η 3 -C 3 H 5 ) 2 , has a reported magnetic moment of 1.8 μ B …”

“…7,8 The only known 17-electron half-sandwich Cr(III) system is the bis(allyl) compound CpCr(η 3 -allyl) 2 , which thermally decomposes, however, above 0 °C. 2,9 Recent attempts in this laboratory at using the chelate effect of bidentate phosphine ligands have only resulted in the formation of CpCrX 2 (η 1 -L-L) (X ) Cl, CH 3 ; L-L ) dmpe, dppe, dmpm) complexes with one coordinated and one dangling P donor and a 15-electron configuration, the alternative 17-electron CpCrX 2 (η 2 -L-L) structure not being present in spectroscopically observable concentrations at equilibrium. 10 The different behaviors of Cr(III) and Mo(III) have been attributed to the greater cost of pairing electrons in the smaller 3d orbitals of Cr(III) and to the smaller energy gain associated with the formation of a new Cr-L bond, whereas differences in steric requirements around Cr 3+ and Mo 3+ do not appear to play a major role.…”

“…The only known 17-electron half-sandwich Cr(III) system is the bis(allyl) compound CpCr(η 3 -allyl) 2 , which thermally decomposes, however, above 0 °C. , Recent attempts in this laboratory at using the chelate effect of bidentate phosphine ligands have only resulted in the formation of CpCrX 2 (η 1 -L-L) (X = Cl, CH 3 ; L-L = dmpe, dppe, dmpm) complexes with one coordinated and one dangling P donor and a 15-electron configuration, the alternative 17-electron CpCrX 2 (η 2 -L-L) structure not being present in spectroscopically observable concentrations at equilibrium …”