Bis(pyrene)metal complexes of vanadium, niobium and titanium: isolable homoleptic pyrene complexes of transition metals

Reduction of VCl3(THF)3 (THF is tetra­hydro­furan) and NbCl4(THF)2 by alkali metal pyrene radical anion salts in THF affords the paramagnetic sandwich complexes bis­[(1,2,3,3a,10a,10b-η)-pyrene]vanadium(0), [V(C16H10)2], and bis­[(1,2,3,3a,10a,10b-η)-pyrene]niobium(0), [Nb(C16H10)2]. Treat­ment of tris­(naphthalene)­titanate(2−) with pyrene provides the isoelectronic titanium species, isolated as an (18-crown-6)potassium salt, namely catena-poly[[(18-crown-6)potassium]-μ-[(1,2-η:1,2,3,3a,10a,10b-η)-pyrene]-titanate(−I)-μ-[(1,2,3,3a,10a,10b-η:6,7-η)-pyrene]], {[K(C12H24O6)][Ti(C16H10)2]}n. The first two compounds have very similar packing, with neighboring mol­ecules arranged orthogonally to one another, such that aromatic donor–acceptor inter­actions are likely responsible for the specific arrangement. The asymmetric unit contains a half-occupancy metal center η6-coordinated to one pyrene ligand, with the full M(pyrene)2 mol­ecule generated by a crystallographic inversion center. In the titanium compound, the cations and anions are in alternating contact throughout the crystal structure, in one-dimensional chains along the [101] direction. As in the other two compounds, the asymmetric unit contains a half-occupancy Ti atom η6-coordinated to one pyrene ligand. Additionally, the asymmetric unit contains one half of an (18-crown-6)potassium cation, located on a crystallographic inversion center coincident with the K atom. The full formula units are generated by those inversion centers. In all three structures, the pyrene ligands are eclipsed and sandwich the metals in one of two inversion-related sites. These species are of inter­est as the first isolable homoleptic pyrene transition metal complexes to be described in the scientific literature.