An N-heterocyclic carbene with a saturated backbone and spatially-defined steric impact

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Abstract

The synthesis and coordination chemistry of a saturated analogue of a 'bulky-yet-flexible' N-heterocyclic carbene (NHC) ligand are described. "SIPaul" is a 4,5-dihydroimidazol-2-ylidene ligand with unsymmetrical aryl N-substituents, and is one of the growing class of 'bulky-yet-flexible' NHCs that are sufficiently bulky to stabilise catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the metal centre. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume (%Vbur), while the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the
corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small.
Original languageEnglish
Number of pages9
JournalZeitschrift fur Anorganische und Allgemeine Chemie
Early online date11 Dec 2018
DOIs
Publication statusE-pub ahead of print - 11 Dec 2018

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Ligands
Iridium
Palladium
Nickel
Silver
Electronic properties
Catalysis
Copper
Metals
carbene
selenourea

Keywords

  • N-heterocyclic carbenes
  • coordination chemistry
  • organometallic chemistry

Cite this

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title = "An N-heterocyclic carbene with a saturated backbone and spatially-defined steric impact",
abstract = "The synthesis and coordination chemistry of a saturated analogue of a 'bulky-yet-flexible' N-heterocyclic carbene (NHC) ligand are described. {"}SIPaul{"} is a 4,5-dihydroimidazol-2-ylidene ligand with unsymmetrical aryl N-substituents, and is one of the growing class of 'bulky-yet-flexible' NHCs that are sufficiently bulky to stabilise catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the metal centre. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume ({\%}Vbur), while the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small.",
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author = "Gillian Laidlaw and Wood, {Susanna H.} and Kennedy, {Alan R.} and Nelson, {David J.}",
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T1 - An N-heterocyclic carbene with a saturated backbone and spatially-defined steric impact

AU - Laidlaw, Gillian

AU - Wood, Susanna H.

AU - Kennedy, Alan R.

AU - Nelson, David J.

PY - 2018/12/11

Y1 - 2018/12/11

N2 - The synthesis and coordination chemistry of a saturated analogue of a 'bulky-yet-flexible' N-heterocyclic carbene (NHC) ligand are described. "SIPaul" is a 4,5-dihydroimidazol-2-ylidene ligand with unsymmetrical aryl N-substituents, and is one of the growing class of 'bulky-yet-flexible' NHCs that are sufficiently bulky to stabilise catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the metal centre. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume (%Vbur), while the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small.

AB - The synthesis and coordination chemistry of a saturated analogue of a 'bulky-yet-flexible' N-heterocyclic carbene (NHC) ligand are described. "SIPaul" is a 4,5-dihydroimidazol-2-ylidene ligand with unsymmetrical aryl N-substituents, and is one of the growing class of 'bulky-yet-flexible' NHCs that are sufficiently bulky to stabilise catalytic intermediates, but sufficiently flexible that they do not inhibit productive chemistry at the metal centre. Here, the synthesis of SIPaul.HCl and its complexes with copper, silver, iridium, palladium, and nickel, and its selenourea, are reported. The steric impact of the ligand is quantified using percent buried volume (%Vbur), while the electronic properties are probed and quantified using the Tolman Electronic Parameter (TEP) and δSe of the corresponding selenourea. This work shows that despite the often very different performance of saturated versus unsaturated carbenes in catalysis, the effect of backbone saturation on measurable properties is very small.

KW - N-heterocyclic carbenes

KW - coordination chemistry

KW - organometallic chemistry

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