Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization

Dana Vuzman, Elena Poverenov, Linda J W Shimon, Yael Diskin-Posner, David Milstein

Research output: Contribution to journalArticle

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Abstract

The synthesis and reactivity of new Pt(II) complexes, including anionic d8 complexes, based on the electron-rich, hemilabile PNN-type pincer ligand C5H3N-2-(CH2PtBu 2)(CH2NEt2) are described. Formation of these complexes involves dearomatization/aromatization processes of the ligand. The chloride complex [(PNN)PtCl]+Cl- (1) was prepared and reacted with the base tBuOK to give the deprotonated, neutral chloride complex (PNN*)PtCl (2) (PNN* = C5H 3N-2-(CHPtBu2)(CH2NEt2)). Reaction of 2 with nBuLi gave the corresponding neutral hydride complex (PNN*)PtH (3), which was readily protonated by triflic acid to give the cationic hydride complex [(PNN)PtH]+OTf- (4). Unexpectedly, reaction of complex 2 with 1 equiv of RLi resulted in opening of the chelate ring, to give the corresponding anionic, dearomatized complexes Li+[(PNN*)Pt(Cl)(R)]- (R = methyl, 5; phenyl, 6). Notably, these complexes are relatively stable although they bear no stabilizing π acceptors that can lower the electron density at the metal center. Complexes 5 and 6 readily undergo protonation by HCl to form the corresponding neutral, aromatic complexes (PNN)Pt(Cl)(R) (R = methyl, 7; phenyl, 8), in which the hemilabile amine "arm" remains decoordinated and does not undergo protonation. Minor amounts of the dearomatized chloride complex 2 are also formed as a result of elimination of RH. Reaction of complexes 5 and 6 with water results in selective protonation-aromatization to give the corresponding complexes 7 and 8.

Original languageEnglish
Pages (from-to)2627-2634
Number of pages8
JournalOrganometallics
Volume27
Issue number11
DOIs
Publication statusPublished - Jun 9 2008

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Protonation
Platinum
Aromatization
Chlorides
platinum
reactivity
chlorides
Ligands
Hydrides
ligands
hydrides
Electrons
electrons
bears
chelates
Amines
Carrier concentration
elimination
amines
Metals

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization. / Vuzman, Dana; Poverenov, Elena; Shimon, Linda J W; Diskin-Posner, Yael; Milstein, David.

In: Organometallics, Vol. 27, No. 11, 09.06.2008, p. 2627-2634.

Research output: Contribution to journalArticle

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title = "Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization",
abstract = "The synthesis and reactivity of new Pt(II) complexes, including anionic d8 complexes, based on the electron-rich, hemilabile PNN-type pincer ligand C5H3N-2-(CH2PtBu 2)(CH2NEt2) are described. Formation of these complexes involves dearomatization/aromatization processes of the ligand. The chloride complex [(PNN)PtCl]+Cl- (1) was prepared and reacted with the base tBuOK to give the deprotonated, neutral chloride complex (PNN*)PtCl (2) (PNN* = C5H 3N-2-(CHPtBu2)(CH2NEt2)). Reaction of 2 with nBuLi gave the corresponding neutral hydride complex (PNN*)PtH (3), which was readily protonated by triflic acid to give the cationic hydride complex [(PNN)PtH]+OTf- (4). Unexpectedly, reaction of complex 2 with 1 equiv of RLi resulted in opening of the chelate ring, to give the corresponding anionic, dearomatized complexes Li+[(PNN*)Pt(Cl)(R)]- (R = methyl, 5; phenyl, 6). Notably, these complexes are relatively stable although they bear no stabilizing π acceptors that can lower the electron density at the metal center. Complexes 5 and 6 readily undergo protonation by HCl to form the corresponding neutral, aromatic complexes (PNN)Pt(Cl)(R) (R = methyl, 7; phenyl, 8), in which the hemilabile amine {"}arm{"} remains decoordinated and does not undergo protonation. Minor amounts of the dearomatized chloride complex 2 are also formed as a result of elimination of RH. Reaction of complexes 5 and 6 with water results in selective protonation-aromatization to give the corresponding complexes 7 and 8.",
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T1 - Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization

AU - Vuzman, Dana

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AU - Diskin-Posner, Yael

AU - Milstein, David

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N2 - The synthesis and reactivity of new Pt(II) complexes, including anionic d8 complexes, based on the electron-rich, hemilabile PNN-type pincer ligand C5H3N-2-(CH2PtBu 2)(CH2NEt2) are described. Formation of these complexes involves dearomatization/aromatization processes of the ligand. The chloride complex [(PNN)PtCl]+Cl- (1) was prepared and reacted with the base tBuOK to give the deprotonated, neutral chloride complex (PNN*)PtCl (2) (PNN* = C5H 3N-2-(CHPtBu2)(CH2NEt2)). Reaction of 2 with nBuLi gave the corresponding neutral hydride complex (PNN*)PtH (3), which was readily protonated by triflic acid to give the cationic hydride complex [(PNN)PtH]+OTf- (4). Unexpectedly, reaction of complex 2 with 1 equiv of RLi resulted in opening of the chelate ring, to give the corresponding anionic, dearomatized complexes Li+[(PNN*)Pt(Cl)(R)]- (R = methyl, 5; phenyl, 6). Notably, these complexes are relatively stable although they bear no stabilizing π acceptors that can lower the electron density at the metal center. Complexes 5 and 6 readily undergo protonation by HCl to form the corresponding neutral, aromatic complexes (PNN)Pt(Cl)(R) (R = methyl, 7; phenyl, 8), in which the hemilabile amine "arm" remains decoordinated and does not undergo protonation. Minor amounts of the dearomatized chloride complex 2 are also formed as a result of elimination of RH. Reaction of complexes 5 and 6 with water results in selective protonation-aromatization to give the corresponding complexes 7 and 8.

AB - The synthesis and reactivity of new Pt(II) complexes, including anionic d8 complexes, based on the electron-rich, hemilabile PNN-type pincer ligand C5H3N-2-(CH2PtBu 2)(CH2NEt2) are described. Formation of these complexes involves dearomatization/aromatization processes of the ligand. The chloride complex [(PNN)PtCl]+Cl- (1) was prepared and reacted with the base tBuOK to give the deprotonated, neutral chloride complex (PNN*)PtCl (2) (PNN* = C5H 3N-2-(CHPtBu2)(CH2NEt2)). Reaction of 2 with nBuLi gave the corresponding neutral hydride complex (PNN*)PtH (3), which was readily protonated by triflic acid to give the cationic hydride complex [(PNN)PtH]+OTf- (4). Unexpectedly, reaction of complex 2 with 1 equiv of RLi resulted in opening of the chelate ring, to give the corresponding anionic, dearomatized complexes Li+[(PNN*)Pt(Cl)(R)]- (R = methyl, 5; phenyl, 6). Notably, these complexes are relatively stable although they bear no stabilizing π acceptors that can lower the electron density at the metal center. Complexes 5 and 6 readily undergo protonation by HCl to form the corresponding neutral, aromatic complexes (PNN)Pt(Cl)(R) (R = methyl, 7; phenyl, 8), in which the hemilabile amine "arm" remains decoordinated and does not undergo protonation. Minor amounts of the dearomatized chloride complex 2 are also formed as a result of elimination of RH. Reaction of complexes 5 and 6 with water results in selective protonation-aromatization to give the corresponding complexes 7 and 8.

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