Nucleophilic de-coordination and electrophilic regeneration of "hemilabile" pincer-type complexes: Formation of anionic dialkyl, diaryl, and dihydride PtII complexes bearing no stabilizing π-acceptors

Elena Poverenov, Mark Gandelman, Linda J W Shimon, Haim Rozenberg, Yehoshoa Ben-David, David Milstein

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Abstract

Novel anionic dialkyl, diaryl, and dihydride platinum(II) complexes based on the new πlong-armπ hemilabile PCN-type ligand C6H 4[CH2P(tBu)2](CH2) 2N(CH3)2 with the general formula Li + [Pt(PCN)(R)2]- (R = Me (4), Ph (6) and H (9)) were prepared by reaction of [Pt(PCN)(R)] complexes (obtained from the corresponding chlorides) with an equivalent of RLi, as a result of the opening of the chelate ring. Alkylating agents based on other metals produce less stable products. These anionic d8 complexes are thermally stable although they bear no stabilizing π acceptors. They were characterized by 1H, 31P{1H}, 13C, and 7Li NMR spectroscopy; complex 9 was also characterized by single crystal X-ray crystallography, showing that the Li + ion is coordinated to the nitrogen atom of the open amine arm and to the hydride ligand (trans to the P atom) of a neighboring molecule (H-Li = 2.15 Å), resulting in a dimeric structure. Complexes 4 and 9 exhibit high nucleophilic reactivity, upon which the pincer complex is regenerated. Reaction of 4 with water, methyl iodide, and iodobenzene resulted in the neutral complex [Pt(PCN)(CH3)] (3) and methane, ethane, or toluene, respectively. Labeling studies indicate that the reaction proceeds by direct electrophilic attack on the metal center, rather than attack on the alkyl ligand. The anionic dihydride complex 9 reacted with water and methyl iodide to yield [Pt(PCN)(H)] (8) and H2 or methane, respectively.

Original languageEnglish
Pages (from-to)4673-4684
Number of pages12
JournalChemistry - A European Journal
Volume10
Issue number19
DOIs
Publication statusPublished - Oct 4 2004

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Keywords

  • Hemilabile complexes
  • Hydrides
  • N,P ligands
  • Pincer ligands
  • Platinum

ASJC Scopus subject areas

  • Chemistry(all)

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