New η-allyl η-cyclopentadienylcobalt cations

Abstract

[Co(R-η-C3H4)(η-C5H5)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt3 to the iodo-complex (R  H) gives [Co(η-C3H5)(η-C5H5)(PEt3)]+. The reactions of [Co(R-η-C3H4)(η-C5H5))I] (R  H or 2-Me) with AgBF4 give solutions containing the coordinatively unsaturated species [Co(R-η-C3H4)(η-C5H5)+. The presence of traces of water leads to the formation of [Co(R-ηC3H4)-(η-C5H5)(H2O)]+. The addition of monodentate ligands L  PEt3 PPh3, AsPh3, SbPh3, CNCH3 and bidentate ligands LL  Ph2PCH2CH2PPh2(dppe) and o-C6H4(AsMe2)2(diars), gives, respectively mononuclear [Co(2-Me-ηC3H4)-(η-C5H5)L]+ and binuclear ligand-bridged [(2-Me-ηC3H4)(η-C5H5)CoLLCo(2-Me-ηC3H4)(η-C5H5))]2+ complexes. Crystals of [Co(2-Me-ηC3H4)(η-C5H5)-(H2O)]+[BF4]- are monoclinic, space group P21/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H2O molecule in a staggered conformation with respect to the 2-Me group.