Synthesis and characterization of the bis-cyclometalating ligand 3,3′,5,5′-tetrakis[(dimethylamino)methyl]biphenyl and its use in the preparation of bimetallic M(II), M(IV) (M = Pt, Pd), and mixed-valence Pt(II)-Pt(IV) complexes via a dilithio-derivative. Crystal structure of the Pd dimer

María Cristina Lagunas, Robert A. Gossage, Anthony L. Spek, Gerard Van Koten*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

92 Citations (Scopus)

Abstract

The potentially bis-cyclometalating ligand 3,3′,5,5′-tetrakis[(dimethylamino)methyl]-biphenyl, was prepared from 3,5-(Me2NCH2)2C6H3Br in a one-pot synthesis involving lithium-halogen exchange, transmetalation, and reductive-elimination reactions. This ligand undergoes selective dilithiation in the 4 and 4′ positions of the biphenyl group to form [Li2{2,6-(Me2NCH2)2C 6H2}2]n, which is a versatile precursor to bimetallic complexes via a double transmetalation reaction. The syntheses and characterization of the new homobinuclear Pt(II) and Pd(II) compounds, [(MeCN)Pt{2,6-(Me2NCH2)2C6H 2}-]2(CF3SO3)2 and [ClPd{2,6-(Me2NCH2)2C6H 2}-]2, is reported in addition to a novel synthetic route to the complex [ClPt{2,6-(Me2NCH2)2C6H 2}-]2. The solid-state structure of Pd dimer was determined by single-crystal X-ray diffraction. Oxidative addition of Cl2 to the latter Pt compound produced the bis-platinum(IV) complex [Cl3Pt{2,6-(Me2NCH2)2C 6H2}-]2, which reacts with 2 equiv of Ag(O3SCF3) in MeCN solution to form [(MeCN)Cl2Pt{2,6-(Me2-NCH2)2C 6H2}-]2(CF3SO3) 2. This complex could also be obtained directly by reaction of the former PtII dimer with 2 equiv of Cl2IPh. 1H NMR spectroscopic studies show that mixtures of the PtII and PtIV dimers in acetonitrile solution are in equilibrium with a mixed-valence (PtII,PtIV) species [(MeCN)PtII{2,6-(Me2NCH2)2C 6H2-C6H2(CH2NMe 2)-2,6}PtIVCl2(NCMe)](CF3-SO 3)2, which, however, could not be isolated in pure form. The reaction of the PtII dimer with ≤ 1 equiv of Cl2IPh also gave a PtIV dimer, along with unreacted starting material and the mixed-valence complex. A reversible double C-C bond formation has been achieved by reaction of the PtII dimer with excess of methyl iodide. This procedure yields the bis(arenonium) species [IPtII{2,6-(Me2NCH2)2-1-MeC 6H2}-]2(CF3SO3) 2 in which both the Me groups derived from I-Me bond cleavage are bound to the Cipso of the aryl rings. The mono-(arenonium) compound [IPtII{2,6-(Me2NCH2)2-1-MeC 6H2-C6H2(CH2NMe 2)2-2′,6′}PtII](CF 3SO3)2 has been identified as an intermediate in this reaction by 1H NMR spectroscopy.

Original languageEnglish
Pages (from-to)731-741
Number of pages11
JournalOrganometallics
Volume17
Issue number4
Publication statusPublished - 16 Feb 1998
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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