Mono- and bis-[2-(P,P-dimethylphosphanyl)ethyl]tetramethylcyclopentadienyl zirconium(IV) complexes: Synthesis and structural studies in crystalline state and in solutions

Synthetic routines for a new ligand C₅Me₄CH₂CH₂PMe₂ (2b) in forms of its Li- (2b-Li), Na- (2b-Na) salts and in the CH-form (2b-H), as well as for silanes Me₃Si-C₅H₄CH₂CH₂PMe₂ (3a) and Me₃Si-C₅Me₄CH₂CH₂PMe₂ (3b) have been developed. On the basis of it, new half-sandwich [η⁵:η¹-κP-C₅H₄CH₂CH₂PMe₂]ZrCl₃ (4a), [η⁵:η¹-κP-C₅Me₄CH₂CH₂PMe₂]ZrCl₃ (4b) and sandwich [η⁵-C₅Me₄CH₂CH₂PMe₂]₂ZrCl₂ (5), [η⁵-C₅Me₄CH₂CH₂PMe₂][η⁵-C₅Me₅]ZrCl₃ (6) complexes of Zr(IV) have been prepared and characterized. Along with them, the first example of X-ray structurally characterized dinuclear Zr(IV) complex incorporating both sandwich (6) and half-sandwich (4b) moieties linked one to another by means of Zr ← P coordination bond 7, has been described. Formation of an analogously organized trinuclear complex 8, built from one sandwich fragment of 5 and two half-sandwich fragments of 4b was proved by NMR spectroscopy methods. Molecular structures of half-sandwich complexes in their solvent-free dimeric forms (4a and 4b) and as 1:1 adducts with THF (4a-THF and 4b-THF) along with those of dinuclear complex 7 have been established by X-ray diffraction analyses. The dynamic behavior for di- and trinuclear complexes 7 and 8, due to the intermolecular dissociation-coordination of the Me₂P-groups in THF-d₈ solutions has been studied by variable-temperature NMR spectroscopy.