The First Example of Linkage-Isomeric Ketene Metal Complexes

Abstract

Dedicated to Professor Otto J. Scherer on the occasion of his 65th birthdayIn the course of investigations on the reactivity of carbenerhodium complexes trans-[RhCl( CR' 2 )(L) 2 ] (R' aryl; L PR 3 , AsR 3 , SbR 3 ) we recently observed [1] that these compounds react smoothly with olefins, CO, and isocyanides by C ± C coupling. While the reaction of 1 with ethene affords besides 2 exclusively 1.1-diphenylpropene (and not 1.1diphenylcyclopropane), treatment of 1 with CO forms the carbonyl complex 3 and diphenylketene (Scheme 1). [1,2] Since it is known from the work by the groups of Herrmann, Cutler, Roper, and others that reactions of both metal carbonyls with diazoalkanes and of metal carbenes with CO under pressure lead to ketene complexes, [3] we were inter-Scheme 1. L PiPr 3 .

Oxygen Transfer from Chromyl Chloride to Alkynes and Allene – IR-Spectroscopic Identification of η1-Ketene and Cyclopropanone Complexes of O=CrCl2

“…tial energy surface (triplet state structures of C 1 symmetry Scheme 2. [15] In order to permit assignment of the coordination mode of the ketene ligand in into the base line (not shown in Figure 1). Upper trace: Difference between the IR spectrum (1800Ϫ350 cm Ϫ1 ) of CrO 2 Cl 2 isolated in an argon matrix doped with 5 mol-% acetylene at 7 K and the spectrum recorded of the same matrix after photolysis at 411 nm for 20 min.…”

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

“…61 An XRD study of single crystals of 11 grown from slow evaporation of liquid butane confirmed the inferred η 2 -CO ketene assignment (Figure 4), with comparable O1-C31 (1.2799(12) Å) and C31-C32 (1.3536(14) Å) distances. 87-89 η 2 -CC ketene adducts are known, [90][91][92] but the O-bound form is often thermodynamically favored. 90 Contrasting the structure of 9, 25 As in the structure of above, the central arene is engaged in η 6 coordination to Mo, consistent with the more reduced Mo center formed on C-C coupling.…”

“…87-89 η 2 -CC ketene adducts are known, [90][91][92] but the O-bound form is often thermodynamically favored. 90 Contrasting the structure of 9, 25 As in the structure of above, the central arene is engaged in η 6 coordination to Mo, consistent with the more reduced Mo center formed on C-C coupling. 7, Mo1-C31 2.1629(10), Mo1-Carene (ave.) 2.2599(9), O1-C31 1.2799 (12), C31-C32 1.3536(14), ∠O1-C31-C32 132.32(9).…”

An Iridium Difluoroketene Complex: Synthesis and Isolation

“…An unusually short CO bond of 1.11(1) Å for 5 compared to other iridium and rhodium η 2 ‐(C,C)‐bound ketene complexes suggests that back‐donation from the metal center to the ketene does not elongate the CO bond 15. 17 However, shorter IrC and CC bonds were also measured, which indicate that the difluoroketene binds more closely than diphenyl‐ or phenylketene to iridium 18…”