Dinuclear zwitterionic silver(i) and gold(i) complexes bearing 2,2-acetate-bridged bisimidazolylidene ligands

Bruno Dominelli; Gerri M. Roberts; Christian Jandl; Pauline J. Fischer; Robert M. Reich; Alexander Pöthig; João D.G. Correia; Fritz E. Kühn

doi:10.1039/c9dt03035b

Dinuclear zwitterionic silver(i) and gold(i) complexes bearing 2,2-acetate-bridged bisimidazolylidene ligands

Bruno Dominelli, Gerri M. Roberts, Christian Jandl, Pauline J. Fischer, Robert M. Reich, Alexander Pöthig, João D.G. Correia, Fritz E. Kühn

Associate Professorship of Molecular Catalysis

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12 Scopus citations

Abstract

Four novel dinuclear Ag(i) and Au(i) NHC complexes bearing two 2,2-acetate-bridged bisimidazolylidene ligands (R = Me and iPr) of zwitterionic and metallacyclic forms are reported. The functionalized methylene bridge of the ligands leads to water soluble complexes, which have been characterized by NMR and IR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of L_a-H₂-PF₆, Ag₂(L_a)₂, Ag₂(L_b)₂ and Au₂(L_a)₂. Dimerization processes caused by hydrogen bonding or Ag(i)-carboxylate interactions in the solid state were observed for L_a-H₂-PF₆ and Ag₂(L_a)₂. DOSY NMR experiments confirmed that both bisimidazolium salts appear as dimers in aqueous solutions, in contrast to the corresponding monomeric Ag(i) and Au(i) complexes. Both gold(i) complexes form syn- and anti-isomers analogous to the reference coinage metal-based complexes. Protonation studies of the syn-isomer gold(i) complex Au₂(L_a)₂ were successful, whereas post-modification esterification or amidation reactions were not feasible. Additionally, decarboxylation reactions (thermally induced Krapcho- or oxidative Hunsdiecker-type) of the bisimidazolium salts were observed. Thus, the proximity of the carboxyl moiety to imidazolium/imidazolylidene rings seems to negatively affect stability and reactivity.

Original language	English
Pages (from-to)	14036-14043
Number of pages	8
Journal	Dalton Transactions
Volume	48
Issue number	37
DOIs	https://doi.org/10.1039/c9dt03035b
State	Published - 2019

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title = "Dinuclear zwitterionic silver(i) and gold(i) complexes bearing 2,2-acetate-bridged bisimidazolylidene ligands",

abstract = "Four novel dinuclear Ag(i) and Au(i) NHC complexes bearing two 2,2-acetate-bridged bisimidazolylidene ligands (R = Me and iPr) of zwitterionic and metallacyclic forms are reported. The functionalized methylene bridge of the ligands leads to water soluble complexes, which have been characterized by NMR and IR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of La-H2-PF6, Ag2(La)2, Ag2(Lb)2 and Au2(La)2. Dimerization processes caused by hydrogen bonding or Ag(i)-carboxylate interactions in the solid state were observed for La-H2-PF6 and Ag2(La)2. DOSY NMR experiments confirmed that both bisimidazolium salts appear as dimers in aqueous solutions, in contrast to the corresponding monomeric Ag(i) and Au(i) complexes. Both gold(i) complexes form syn- and anti-isomers analogous to the reference coinage metal-based complexes. Protonation studies of the syn-isomer gold(i) complex Au2(La)2 were successful, whereas post-modification esterification or amidation reactions were not feasible. Additionally, decarboxylation reactions (thermally induced Krapcho- or oxidative Hunsdiecker-type) of the bisimidazolium salts were observed. Thus, the proximity of the carboxyl moiety to imidazolium/imidazolylidene rings seems to negatively affect stability and reactivity.",

author = "Bruno Dominelli and Roberts, {Gerri M.} and Christian Jandl and Fischer, {Pauline J.} and Reich, {Robert M.} and Alexander P{\"o}thig and Correia, {Jo{\~a}o D.G.} and K{\"u}hn, {Fritz E.}",

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year = "2019",

doi = "10.1039/c9dt03035b",

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AU - Dominelli, Bruno

AU - Roberts, Gerri M.

AU - Jandl, Christian

AU - Fischer, Pauline J.

AU - Reich, Robert M.

AU - Pöthig, Alexander

AU - Correia, João D.G.

AU - Kühn, Fritz E.

PY - 2019

Y1 - 2019

N2 - Four novel dinuclear Ag(i) and Au(i) NHC complexes bearing two 2,2-acetate-bridged bisimidazolylidene ligands (R = Me and iPr) of zwitterionic and metallacyclic forms are reported. The functionalized methylene bridge of the ligands leads to water soluble complexes, which have been characterized by NMR and IR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of La-H2-PF6, Ag2(La)2, Ag2(Lb)2 and Au2(La)2. Dimerization processes caused by hydrogen bonding or Ag(i)-carboxylate interactions in the solid state were observed for La-H2-PF6 and Ag2(La)2. DOSY NMR experiments confirmed that both bisimidazolium salts appear as dimers in aqueous solutions, in contrast to the corresponding monomeric Ag(i) and Au(i) complexes. Both gold(i) complexes form syn- and anti-isomers analogous to the reference coinage metal-based complexes. Protonation studies of the syn-isomer gold(i) complex Au2(La)2 were successful, whereas post-modification esterification or amidation reactions were not feasible. Additionally, decarboxylation reactions (thermally induced Krapcho- or oxidative Hunsdiecker-type) of the bisimidazolium salts were observed. Thus, the proximity of the carboxyl moiety to imidazolium/imidazolylidene rings seems to negatively affect stability and reactivity.

AB - Four novel dinuclear Ag(i) and Au(i) NHC complexes bearing two 2,2-acetate-bridged bisimidazolylidene ligands (R = Me and iPr) of zwitterionic and metallacyclic forms are reported. The functionalized methylene bridge of the ligands leads to water soluble complexes, which have been characterized by NMR and IR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of La-H2-PF6, Ag2(La)2, Ag2(Lb)2 and Au2(La)2. Dimerization processes caused by hydrogen bonding or Ag(i)-carboxylate interactions in the solid state were observed for La-H2-PF6 and Ag2(La)2. DOSY NMR experiments confirmed that both bisimidazolium salts appear as dimers in aqueous solutions, in contrast to the corresponding monomeric Ag(i) and Au(i) complexes. Both gold(i) complexes form syn- and anti-isomers analogous to the reference coinage metal-based complexes. Protonation studies of the syn-isomer gold(i) complex Au2(La)2 were successful, whereas post-modification esterification or amidation reactions were not feasible. Additionally, decarboxylation reactions (thermally induced Krapcho- or oxidative Hunsdiecker-type) of the bisimidazolium salts were observed. Thus, the proximity of the carboxyl moiety to imidazolium/imidazolylidene rings seems to negatively affect stability and reactivity.

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AN - SCOPUS:85072589196

SN - 1477-9226

VL - 48

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JO - Dalton Transactions

JF - Dalton Transactions

IS - 37

ER -

Dinuclear zwitterionic silver(i) and gold(i) complexes bearing 2,2-acetate-bridged bisimidazolylidene ligands

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