.eta.5-Cyclohexadienyltricarbonylchromium(0) complexes from addition of carbon nucleophiles to .eta.6-benzenetricarbonylchromium(0). Formation, chemical and spectroscopic features, and x-ray diffraction analysis

Abstract

The addition of reactive carbanions to a6-benzenetricarbonyIchromium(0) produced ~'-(6-alkylcyclohexadienyl)tricarbonylchromium(0) anion complexes, as the lithium salts. Reaction with a variety of oxidizing agents (iodine, cerium(lV), oxygen) removes the hydrogen from C-6 and detaches the C r ( C 0 ) 3 unit, to produce a substituted arene. Reaction with electrophiles (potential hydride acceptors) leads to cleavage of the carbon-carbon bond at C-6 with regeneration of qh-benzenetricarbonylchroniium(0). Solution spectral ( ' H N MR, IR) data are consistent with a n g'-cyclohexadienyl structure. X-ray diffraction analysis on the crystalline adduct of qh-benzenetricarbonyIchromium(0) and 2-lithio-l,3-dithane defines the mode of addition (exo), the deformation (38.6') of C-6 from the plane of carbons 1-5 in the cyclohexadienyl ligand. and the preferred conformation of the C r ( C 0 ) 3 unit.

Addition of Carbon Nucleophiles to Tricarbonylchromium Complexes of 1,2‐Dihydrocyclobutabenzene, Indane, 1,2,3,4‐Tetrahydronaphtbalene and ortho‐Xylene

“…1/10 kcal. As observed [29] and predicted by EHMO calculations [30], there is a strong preference for the Cr(CO), moiety to adopt a conformation in which a CO ligand eclipses the C-atom bearing the nucleophile. c) Finally a method developed by Weber et al in which the interaction energy between an incoming nucleophile (H-) and the complex is mapped over the molecular surface [31] was applied.…”

“…1 kcal/mol higher in energy as a result of interaction with the aliphatic substituents: b ) The attack of a nucleophile on an [Cr(arene)(CO),] complex will lead to an 7 5-cyclohexadienyl complex [29]. Calculations were carried out on the relative stabilities of the qS-cyclohexadienyl complexes formed by attack of a hydride ion on complexes 1 and 4 using a geometry based on the crystal structure of the 1,3-dithiane adduct of [Cr(benzene)(CO),] [29]. The results showed no difference between 1 and 4, with attack at the p-position being slightly more favorable in both cases by ca.…”

Nucleophilic addition to di- and poly-iron arene complex cations

“…anions to organometallic complexes has led to novel routes to Addition of carbanions, hydrides, phosphorus and nitrogen the functionalization of aroma-tic compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). It is well known that the complexation of a metal moiety, such as (C0)3Cr, (CO),Mn+, ( c~H~) F~~+ , Or CpFe+ to an aromatic system activates the arene ring towards nucleophilic addition reactions .…”

Quantum Chemical Investigation of the Structure and Reactivity of Indole Derivatives of Tricarbonylchromium(0)

“…anion [24], in order to take account of the interactions between C(7) and the dienyl. An eclipsed conformation of the tripod has been chosen, as suggested by X-ray structural investigations on related adducts .…”