Ethene insertion into a palladium–acetyl bond: crystal structure of [Pd(CH₂CH₂COMe)(NC₅H₄CO₂Me-2)(PPh₃)]BF₄, a novel reaction intermediate from the insertion process

Abstract

From the catalytic conversion of CO and ethene to polyketone with [Pd(Me)(NCSH4C02Me-2)-(PPh3)]BF4 1, the reaction of ethene with [Pd(COMe)(NC5H4CO2Me-2)-(PPh3)]BF4 2 yields a rare example of an isolable product from the insertion of an unstrained alkene into a Pd-acyl bond, and the crystal structure of [Pd(CH2CH2COMe)-(NCSH4C02Me-2)(PPh3)]BF4 3 showing a novel square-pyramidal intermediate with a weakly interacting oxygen in the apical position.

Stepwise Ethene and/or Methyl Acrylate/CO Insertions into the Pd−C Bond of Cationic Palladium(II) Complexes Stabilized by a (P,O) Chelate

“…[1±3, 9±13] However, owing to difficulties encountered in the isolation of intermediates, detailed investigations on the early stages of the chain-growth process have been carried out mainly with strained alkenes and to date only one structural report on ethene ± CO coupling has been published. [14] Furthermore, there is considerable interest in the copolymerization of olefins with polar monomers, such as methyl acrylate. However, despite recent achievements, [15] the need to increase the percentage of functional groups in the final copolymers remains.…”

“…Related metallacycles have been isolated upon insertion of propene, [2,10] styrene, [2,27,28] and cyclic mono- [11, 24, 29±33] and diolefins [2, 11, 12, 18, 31±35] into palladium ± acyl bonds. For ethene, however, there are few precedents, [3,9,14,35] and 3 represents the first complex of this type containing a P,O ligand. Many such heterobidentate P,O ligands play key roles in homogeneous catalysis, including the nickel-catalyzed ethene oligomerization to linear a-olefins in which minor changes are known to have considerable chemical consequences.…”

“…[36,37] The structure of 3 was unambiguously determined by X-ray diffraction ( Figure 1) and is only the second ethene ± acyl coupling product to be so characterized. [14] Even with other olefins, very little structural data is available. [11,38] (2) ) is longer than in related norbornene ± CO coupling products (2.016(5) ± 2.033 (5) ).…”

Insertion of CO and Strained Olefins into Organometallic (Ferrocenylmethyl)phosphane Palladium Complexes

“…[22] Apart from the absence of vinyl protons, similar spectroscopic features were found for complex 8 obtained after NBE insertion into 6. The reaction of 6 with unstrained olefins, such as ethylene or styrene, was also briefly investigated, leading to decomposition products (ethylene), [23] whereas insertion of styrene did not occur at all.…”

Enantioselective Dicarbonylation of Styrene to Isotactic Poly[1‐oxo‐2‐phenylpropane‐1,3‐diyl] with phosphinodihydrooxazole‐palladium(ii) complexes: Model studies for enantioface selection preliminary communication

“…In addition to systems containing monodentate ligands [3], palladium complexes, modified by C,-symmetric ligands [4] using ethene or norbornene as the olefin substrate, were usually the subject of these investigations. C,-Symmetric ligands have not been studied to such an extent [4c] [5], but revealed useful for recognizing the migration of the alkyl group in the step corresponding to the acyl formation [6]. Only two studies have been published on the insertion reaction of prochiral olefins, namely 4-(tert-butyl)styrene [7] and propene [8]; in particular, the latter approached the problem of enantioface selection during the copolymerization process using a chelate C,-ligand.…”