Ansa-metallocenes with B-N and B-P linkages:: the importance of N-H•••F-C hydrogen bonding in pentafluorophenyl boron compounds

The reaction of Cp'(Cp(B))ZrCl(2) [Cp(B) = eta(5)-C(5)H(4)B(C(6)F(5))(2)] with LiNHCMe(3) gave Cp'(Cp(B))(mu-NHCMe(3))ZrCl, with a constrained-geometry type Cp-B-N chelate ligand. The (19)F-NMR spectrum of the zirconium complexes, as well as that of the titanium analogue, reveals C-F(...)H-N hydrogen bonding to one of the ortho-F atoms of a C(6)F(5) ring, strong enough to persist in solution at room temperature. The reaction of Cp'(Cp(B))TiCl(2) With LiPPh(2) affords the Cp-B-P chelate complex Cp'(Cp(B))(p-PPh(2))TiCl, the first example of a crystallographically characterised Ti(IV) phosphido compound. A (19)F-NMR study of a number of adducts of B(C(6)F(5))(3) with prim- and sec-amines demonstrates the importance of intramolecular hydrogen bonding to C(6)F(5) in this class of compounds, while there are no such interactions in B(C(6)F(5))(3)(PHR(2)) (R = Cy, Ph). The crystal structures of Cp'(Cp(B))(mu-PPh(2))TiCl, B(C(6)F(5))(3)(NHMe(2)) and B(C(6)F(5))(3)(PHCy(2)) are reported. (C) 2003 Elsevier Science B.V. All rights reserved.