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

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The reaction of Cp′(Cp B)ZrCl 2 [Cp B=η 5-C 5H 4B(C 6F 5) 2] with LiNHCMe 3 gave Cp′(Cp B)(μ-NHCMe 3)ZrCl, with a constrained-geometry type CpBN chelate ligand. The 19F-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 6F 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)(μ-PPh 2)TiCl, the first example of a crystallographically characterised Ti(IV) phosphido compound. A 19F-NMR study of a number of adducts of B(C 6F 5) 3 with prim- and sec-amines demonstrates the importance of intramolecular hydrogen bonding to C 6F 5 in this class of compounds, while there are no such interactions in B(C 6F 5) 3(PHR 2) (R=Cy, Ph). The crystal structures of Cp′(Cp B)(μ-PPh 2)TiCl, B(C 6F 5) 3(NHMe 2) and B(C 6F 5) 3(PHCy 2) are reported.