Electrophilic addition reactions of the Lewis acids B(C6F5)2R [R = C6F5, Ph, H or Cl] with the metallocene hydrides [M(η-C5H5)2H2] (M = Mo or W), [Re(η-C5H5)2H] and [Ta(η-C5H5)2H3]

The syntheses of the new compounds [W(η-C5H5)(η-C5H4{B(C6F5)2R})H3], where R = (C6F5) 1, Ph 2, H 3 or Cl 4, [Mo(η-C5H5)2(H)(η1-HB(C6F5)3)] 5, [Mo(η-C5H5)2(H)(η1-H2B(C6F5)2)] 6, [Mo(η-C5H4Me)2(H)(η1-HB(C6F5)3)] 7, [Re(η-C5H5)(η-C5H4B(C6F5)3)H2]·0.5C6H5Me 8, [Ta(η-C5H5)2(H)2(η1-HB(C6F5)3)] 9 and [Re(η-C5H5)(η-C5H4{B(C6F5)2})(C6F5)] 10 are described. The crystal structures of compounds 4 and 10 have been determined. Initial electrophilic addition of the Lewis acid B(C6F5)3 occurs either by exo-addition to a carbon of a η-cyclopentadienyl ring with formation of an exo-{(C6F5)3B}C5H5, or by formation of an M–μ-H–B two-electron three-centre bond.