Synthesis and characterisation of 1-alkyl-2-imidazoline complexes of noble metals; crystal structure of trans-[PtCl2{N C(H)N(Et)CH2CH2}(PEt3)]

Authors:
  • BÇBekir Çetinkaya
    Bekir Çetinkaya
  • EÇEngin Çetinkaya
    Engin Çetinkaya
  • PHPeter B. Hitchcock
    Peter B. Hitchcock
  • MLMichael F. Lappert
    Michael F. Lappert
  • IÖIsmail Özdemir
    Ismail Özdemir
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Abstract
Treatment of a 1-alkyl-2-imidazoline N(R)(CH 2 ) 2 NCH with a µ-dichloro-dirhodium(I) or -diplatinum(II) complex [{Rh(µ-Cl)(cod)} 2 ] or [{Pt(µ-Cl)Cl(PEt 3 )} 2 ] gave the mononuclear 1-alkyl-2-imidazoline complex [RhCl{NC(H)N(R)CH 2 CH 2 }(cod)] (R = Et 1a or CH 2 Ph 1b) or trans-[PtCl 2 {NC(H)N(R)CH 2 CH 2 }(PEt 3 )] (R = Et 2a or CH 2 Ph 2b) (cod = cycloocta-1,5-diene). A single-crystal X-ray diffraction study of 2a revealed it to have a square-planar geometry about platinum, the imidazoline ring being coplanar with this plane, and a Pt–N distance of 2.088(11) Å; the Pt–P bond length of 2.231(4) Å indicates that the imidazoline ligand has a marginally stronger trans influence than analogues of its isomer such as CN(R)(CH 2 ) 2 NR. The rhodium complexes 1a and 1b have been shown to catalyse cyclopropanation of styrene and ethyl diazoacetate in high yields.