Palladium Catalyzed Alternating Cooligomerization of Ethylene and Carbon Monoxide to Unsaturated Ketones

Keim, Wilhelm; Maas, Heiko; Mecking, Stefan

doi:10.1515/znb-1995-0318

Cited by 54 publications

(32 citation statements)

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“…Endowed with soft and hard donor groups, phosphorus–oxygen and phosphorus–nitrogen based ligands represent the most studied class of functional phosphanes and many such examples have been presented in the previous section. The oxygen functional groups associated with the phosphorus donor come from alcohol, ether, ketone, ester, amide, and phosphane oxide or phosphonate groups 1, 2, 26, 27, 43, 78, 90–94. Although these various functions will impart significant changes in the coordination properties and hemilability of the corresponding P,O ligands, it is generally observed that phosphorus–oxygen ligands are the most weakly chelating type of ligand.…”

Section: Hemilabile Ligandsmentioning

confidence: 99%

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

Braunstein

Naud

2001

Angew. Chem. Int. Ed.

951

618

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Ligand design is becoming an increasingly important part of the synthetic activity in chemistry. This is of course because of the subtle control that ligands exert on the metal center to which they are coordinated. Ligands which contain significantly different chemical functionalities, such as hard and soft donors, are often called hybrid ligands and find increasing use in molecular chemistry. Although the interplay between electronic and steric properties has long been recognized as essential in determining the chemical or physical properties of a complex, predictions remain very difficult, not only because of the considerable diversity encountered within the Periodic Table—different metal centers will behave differently towards the same ligand and different ligands can completely modify the chemistry of a given metal—but also because of the small energy differences involved. New systems may—even through serendipity—allow the emergence of useful concepts that can gain general acceptance and help design molecular structures orientated towards a given property. The concept of ligand hemilability, which finds numerous illustrations with hybrid ligands, has gained increased acceptance and been found to be very useful in explaining the properties of metal complexes and in designing new systems for molecular activation, homogeneous catalysis, functional materials, or small‐molecule sensing. In the field of homogeneous enantioselective catalysis, in which steric and/or electronic control of a metal‐mediated process must occur in such a way that one stereoisomer is preferentially formed, ligands containing one or more chiral oxazoline units have been found to be very valuable for a wide range of metal‐catalyzed reactions. The incorporation of oxazoline moieties in multifunctional ligands of increasing complexity makes such ligands good candidates to display hemilabile properties, which until recently, had not been documented in oxazoline chemistry. Herein, we briefly recall the definition and scope of hemilabile ligands, present the main classes of ligands containing one or more oxazoline moieties, with an emphasis on hybrid ligands, and finally explain why the combination of these two facets of ligand design appears particularly promising.

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Section: Hemilabile Ligandsmentioning

confidence: 99%

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

Braunstein

Naud

2001

Angew. Chem. Int. Ed.

951

618

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“…Figs. 2 and 6 display the different arrangements of oxygens in free L and in the complexes, being on the opposite sides of an ideal plane C(1 I), C(12), C(5), C (6) in the former and on the same side in the complexes. Although this comparison shows the great flexibility of the ligand, the coordination to Pd might induce a strain in the propane-and butane-dioloxy bridges, as appears from the increased bond angles at oxygens (up to 123"), compared with the value observed i n free L2 (Table 6).…”

Section: Synthesis and Characterisation Of Complexes 1 Andmentioning

confidence: 99%

New atropisomeric bidentate nitrogen-donor compounds as potential stereocontrollers in mild CO–styrene copolymerisation catalysed by palladium(II) salts

Milani¹,

Alessio²,

Mestroni³

et al. 1996

J. Chem. Soc., Dalton Trans.

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Two new atropisomeric bidentate nitrogen-donor chelating ligands, namely ( -)-(S,S)-3,3'-( 1,2dimethylethylenedioxy)-2,2'-bipyridine L' and ( + )-(R)-3,3'-( 1 -methylethylenedioxy)-2,2'-bipyridine L2, have been synthesised and characterised. The crystal structure of L2 confirmed its atropisomeric nature, the dihedral angle between the planes containing the pyridine rings being 50.1( 1)". The interaction of the new compounds, with palladium(r1) salts led to the corresponding monochelated palladium complexes, [PdL'(O,CCF,),] 1 and [PdL2(02CCF,),] 2, the crystal structures of which have been determined. Both complexes crystallised with two independent molecules in the unit cell. In the two molecules of 1 the ligand L' is in the same conformation; while for 2 the two independent molecules correspond to two different atropisomers. The co-ordination geometry around palladium is square planar in all the molecules. In the two independent molecules of 1 and 2 the dihedral angle between the pyridine rings is considerably smaller than that observed in free L2. The complexes are very active catalyst precursors in CO-styrene copolymerisation under mild reaction conditions (Pco = 1 atm, 30 "C). The inhibiting role of carbon monoxide is evidenced. A low asymmetric induction was observed together with short isotactic sequences in the copolymer chain.

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“…[1,2,3] Their interest in catalysis arises from the easy decoordination of the weak donor centre without the displacement of the ligand, which should confer a better stability to the reaction intermediates. Mixed ligands containing phosphorus along with oxygen, nitrogen or sulphur donor atoms have specifically been designed for use in catalytic reactions such as hydrogenation, [4,5,6] oligomerisation, [7] and hydroformylation of olefins. [8] Pyrazole-derived molecules are good candidates for the preparation of interesting N,NЈ or N,P mixed ligands, owing to their ease of synthesis and the possibility of electronic and steric modulation of their properties.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of a New Potentially Hemilabile Ligand: 1-[2-(Diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole, and Comparison of Its Bonding Properties with the Related 1-[2-(Ethylamino)ethyl]-3,5-dimethylpyrazole Ligand toward RhI

Esquius

Pons

Yáñez

et al. 2002

Eur. J. Inorg. Chem.

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Palladium Catalyzed Alternating Cooligomerization of Ethylene and Carbon Monoxide to Unsaturated Ketones

Cited by 54 publications

References 0 publications

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

Hemilability of Hybrid Ligands and the Coordination Chemistry of Oxazoline-Based Systems

New atropisomeric bidentate nitrogen-donor compounds as potential stereocontrollers in mild CO–styrene copolymerisation catalysed by palladium(II) salts

Synthesis of a New Potentially Hemilabile Ligand: 1-[2-(Diphenylphosphanyl)ethyl]-3,5-dimethylpyrazole, and Comparison of Its Bonding Properties with the Related 1-[2-(Ethylamino)ethyl]-3,5-dimethylpyrazole Ligand toward RhI

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