Synthesis and properties of organometallic Pt-II and Pt-IV complexes with acyclic selenoether and telluroether ligands and selenoether macrocycles

The first series of planar dimethyl(selenoether)Pt-II complexes, [PtMe2L] [L=MeSe(CH2)(n)SeMe (n=2 or 3), o-C6H4(CH2SeMe)(2), [8]aneSe(2) (1,5-diselenacyclooctane), or [16]aneSe(4) (1, 5,9,13 -tetraselenacyclohexadecane),, have been obtained by treatment of [PtMe2(SMe2)(2)] with L in Et2O solution and characterised by VT H-1, C-13{H-1}, Se-77{H-1} and Pt-195{H-1} NMR spectroscopy, electrospray MS and microanalysis. The corresponding dimethyl(telluroether)Pt-II complexes do not form under similar reaction conditions. The distorted octahedral [PtMe3I(L)] [L=o-C6H4(CH2SeMe)(2), [8]aneSe2, [16]aneSe(4) or MeC(CH2SeMe)(3)] form as stable complexes in good yield from reaction of PtMe3I with L in refluxing CHCl3 and have been characterised similarly. These all show bidentate selenoether coordination, with fast pyramidal inversion occurring at room temperature. The distorted octahedral coordination environment at Pt-IV is also confirmed from a crystal structure of [PtMe3I{o-C6H4(CH2SeMe)(2)}]. Rare examples of (telluroether)Pt-IV complexes, [PtMe3I(o-C6H4(CH2-TeMe)(2)}] and the dinuclear [Me3Pt(mu(2)-I)(2)(mu(2)-MeTeCH2-TeMe)PtMe3], have also been prepared and characterised similarly (and also by Te-125{H-1} NMR spectroscopy). The [8]aneSe(2) and [16]aneSe(4) species are the first examples of alkyl Pt-II or Pt-IV complexes with (macro)cyclic selenoether coordination. Halide abstraction (TIPF6) from [PtMe3I(kappa(2)-[16]aneSe(4))] affords [PtMe3(kappa(3)-[16]aneSe(4))]PF6; a rare example of a cationic Pt-IV selenoether. The (diselenoether)Pt-II complexes undergo oxidative addition of MeI to yield the corresponding Pt-IV species [PtMe3I(diselenoether)]