Access to Alkynylpalladium(IV) and -Platinum(IV) Species, Including Triorgano(diphosphine)metal(IV) Complexes and the Structural Study of an Alkynyl(pincer)platinum(IV) Complex, Pt(O2CArF)I(CCSiMe3)(NCN) (ArF ) 4-CF3C6H4, NCN ) [2,6-(dimethylaminomethyl)phenyl-N,C,N]-)

Abstract

New classes of alkynylplatinum(IV) complexes are described, and the first examples of alkynylpalladium(IV) complexes have been detected, including a triorganopalladium(IV) diphosphine complex. Alkynyliodine(III) triflate reagents IPh(CCR²)(OTf) (R² = SiMe3 , Ph) are able to transfer alkynyl groups to diorganoplatinum(II) and “pincer” complexes Pt(O2CAr)(NCN) (NCN = [2,6-(dimethylaminomethyl)- phenyl-N,C,N]-, (Ar = Ph, 4-trifluoromethylphenyl (ArF)); on addition of iodide ion, complexes with new alkynylplatinum(IV) kernels may be isolated: PtIMe2(CCR²)(bpy) (1, 2, 3a) (bpy) 2,2`-bipyridine), PtI(C4H8)(CCSiMe3)(bpy)(4a), PtIPh2(CCSiMe3)(But2 bpy)(5a), and PtI(O2CAr)(CCR)(NCN) [Ar = Ph (14, 15), ArF (16, 17)]. For the reagent PtMe2(dmpe) [dmpe = 1,2-bis(dimethylphosphino)ethane], the unstable complexes PtIMe2(CCR²)(dmpe)(6a, 8a) are detected prior to reductive elimination of ethane and isolation of PtI(C=CR²)(dmpe) (7, 9). Isomerism is exhibited by the octahedral fac-PtIVR2(CCR2) complexes, where complexes 1 and 2 form as a mixture of complexes with the alkynyl group opposite the bidentate ligand and cis to the iodo ligand (1a-6a, 8a), and cis to the bidentate ligand and trans to the iodo ligand (1b, 2b), complexes 3a-5a, 6a, and 8a having R groups mutually cis. An X-ray structural analysis for 16 shows distorted octahedral geometry about the metal with the iodo ligand trans to the carbon donor of the mer-pincer ligand. Studies of the reactivity of related palladium(II) substrates at low temperature allow detection of the pincer complex Pd(O2CPh)(OTf)(CCSiMe3)(NCN)(19) and PdIMe2(CCSiMe3)(dmpe)(18) as a model for frequently proposed “PdIVXR3P2” species in catalytic and stoichiometric reactions.