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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Paper

J. Chem. Soc., Dalton Trans., 1992, 2663 - 2665, DOI: 10.1039/DT9920002663

Synthesis of 1,1-bis(pyrazol-1-ylmethyl)ethene and the structure of a trimethylplatinum(IV) derivative containing an eight-membered chelate ring

Allan J. Canty, R. Thomas Honeyman, Brian W. Skelton and Allan H. White

The bidentate pyrazole-donor ligand 1,1-bis(pyrazol-1-ylmethyl)ethene, [(pz)CH2]2CCH2, may be synthesized in high yield on reaction of the readily obtained potassium pyrazolide with commercially available (ClCH2)2CCH2. Reaction of the ligand with [{PtMe2(SEt2)}2], followed by addition of iodomethane, gives the platinum(IV) complex fac-[PtIMe3{[(pz)CH2]2CCH2-N,N}]. Proton NMR and X-ray structural studies show that the eight-membered chelate ring PtNNC3NN adopts a configuration in which the pyrazole rings are in different environments, forming angles of 26.0(3) and 38.2(3)° with the PtC2N2 mean plane. Thus, the four methylene protons are also in different environments, as are the PtMe groups trans to pyrazole groups. The eight-membered chelate ring is fluxional, undergoing inversion with G 15 kcal mol–1( 63 kJ mol–1) at 10 °C.