Reaktionen und Derivate der Hexacarbonyle des Chroms und Molybdäns'. Le chrome carbonyle et sa préparation par les organomagnésiens. Its vapor pressure is relatively high for a metal complex, 1 mmHg (130 Pa) at 36 ☌). nickel carbonyl and iron carbonyl), chromium hexacarbonyl is toxic and thought to be carcinogenic. In common with many of the other homoleptic metal carbonyls (e.g.

In reactions, potassium perrhenate(VII) is reduced and carbonylated by the chromium reagents and undergoes Cp ligand-transfer to afford CpRh(CO) 3 complex derivatives. This complex is distinctive because it exists in measurable equilibrium with the monometallic Cr(I) radical CpCr(CO) 3.Ī unique double ligand-transfer reaction was reported with using chromium trichloride and chromium hexacarbonyl. Oxidation of this salt affords cyclopentadienylchromium tricarbonyl dimer (Cp 2Cr 2(CO) 6). Treatment of chromium hexacarbonyl with sodium cyclopentadienide gives NaCr(CO) 3(C 5H 5). These anionic species in turn react with alkylating agents such as Me 3O + to form (OC) 5Cr=C(OMe)R to give Fischer carbene complexes: Cyclopentadienyl derivatives One example is (benzene)chromium tricarbonyl.Īlkyl and aryl organolithium reagents (RLi) add to Cr(CO) 6 to give anionic acyl complexes.

These species are typically yellow solids. The products are ' piano stool complexes'. The reactions are especially favorable for electron-rich arenes:Ĭr(CO) 6 + C 6H 5R → Cr(CO) 3(C 6H 5R) + 3 CO Heating a solution of Cr(CO) 6 in an aromatic solvent results in replacement of three CO ligands. Norbornadiene was dimerized photochemically in the presence of Cr(CO) 6, similarly to other metal complexes like Fe(CO) 6, Ni(CO) 4, and Co(CO) 8NO. UV-irradiation of frozen solutions of chromium hexacarbonyl affords a variety of labile adducts, including labile but complexes with some noble gases. Often the THF complex is generated and used in situ. When heated or UV-irradiated in tetrahydrofuran (THF) solution, Cr(CO) 6 converts to Cr(CO) 5(THF) with loss of one CO ligand. Reactions and applications Photochemical reactions Pentacarbonyl derivatives According to one of the most recent studies, the ground state configuration of Cr(CO) 6 turns out (2t 2g) 6(9 t 1u) 0(2t 2u) 0.

On one hand, there has been continuous efforts to calculate the electronic structures (including HOMO and LUMO) as well as its molecular geometry on the chromium hexacarbonyl compound with various approaches. The crystallographic studies on this compound have discovered the Cr–C and C–O distances of 1.916 and 1.171 Å, respectively. On the right, an empty pi-antibonding orbital on CO overlaps with a filled d-orbital on the metal. On the left, a filled sigma-orbital on CO overlaps with an empty d-orbital on the metal. Orbital interactions in a chromium-CO complex. The bonding between d 6 chromium metal and neutral carbonyl ligands is described by the Dewar-Chatt-Duncanson model.It involves donation of electrons in HOMO of CO to empty d orbitals of the Cr metals while back-bonding from other d orbitals to the pi* orbital of the ligands reinforces the interactions synergistically. The formula conforms to the 18-electron rule and the complex adopts octahedral geometry with six carbonyl ligands. In chromium hexacarbonyl, the oxidation state for chromium is assigned as zero, because Cr-C bonding electrons come from the C atom and are still assigned to C in the hypothetical ionic bond which determines the oxidation states. Using specially produced chromium metal]] will react with CO gas to give Cr(CO)6 directly, although the method is not used commercially.Įlectronic structure and bonding CrCl 3 → Reductant CO Cr ( CO ) 6 Įarly work on methods included controbutions from luminaries such as Walter Hieber, his student Ernst Otto Fischer, and Giulio Natta. As described in a 2023 survey of methods 'most cost-effective routes for the synthesis of group 6 hexacarbonyls are based on the reduction of the metal chlorides (CrCl 3, MoCl 5 or WCl 6) with magnesium, zinc or aluminium powders. Like many metal carbonyls, Cr(CO) 6 is generally prepared by 'reductive carbonylation', which involves reduction of a metal halide with under an atmosphere of carbon monoxide. It is a white, air-stable solid with a high vapor pressure. It is homoleptic complex, which means that all the ligands are identical. Chromium hexacarbonyl (IUPAC name: hexacarbonylchromium) is a chromium(0) organometallic compound with the formula Cr(CO) 6.

Cr 6 to cr 3