Synthesis of [W(η5-C5H5)2H(L)] and [W(η5-C5H5)2L2] 2+ cations (L = NCMe, NCPh, C4H8O or CNBut). Crystal and molecular structures of [W(η5-C5H5)2H(C4 H8O)][CF3SO3] and [W(η5-C5H5)2(NCMe)2 ][CF3SO3]2

The cationic hydride complexes [W(η-C 5 H 5 ) 2 H(L)][CF 3 SO 3 ] [L = NCMe, NCPh, tetrahydrofuran (thf) or CNBu t ] have been synthesized by reaction of [W(η-C 5 H 5 ) 2 H 2 ] and methyl trifluoromethanesulfonate in the presence of the σ-donor ligand L. Kinetic measurements on ligand-substitution reactions in CD 3 CN solution indicate that L is labile in solution; [W(η-C 5 H 5 ) 2 H(L)] + cations have half-lives of 315(10), 122(6) and 6.68(5) h (L = NCMe, NCPh or thf respectively) at 44 °C. The activation energy E a for tetrahydrofuran substitution in [W(η-C 5 H 5 ) 2 H(thf)] + is 132 ± 1 kJ mol -1 . An X-ray crystallographic determination of the structure of [W(η-C 5 H 5 ) 2 H(thf)][CF 3 SO 3 ] demonstrates that the tetrahydrofuran ligand is oriented ‘in-plane’ with the centroid–W–centroid plane, indicating that the thf acts as a simple σ-donor ligand. Reaction of [W(η-C 5 H 5 ) 2 H 2 ] with an excess of CF 3 SO 3 Me yields the dicationic tungstenocene complex [W(η-C 5 H 5 ) 2 (NCMe) 2 ][CF 3 SO 3 ] 2 as demonstrated by IR and NMR spectroscopy and X-ray crystallography.