Synthesis and reactions of a zirconium naphthalene complex bearing a tetraanionic C-capped triaryloxide ligand

Treatment of [(O₃C)Zr(thf)₃] (1; [O₃C]^4- = [(3,5-^tBu₂-2-OC₆H₂)₃C]^4-) with 2 equiv. of potassium naphthalenide in DME produced [{K(dme)}₂(O₃C)Zr(C₁₀H₈)] (2), in which the [(O₃C)Zr] fragment is η⁴-bound to one ring of the naphthalene ligand. Complex 2 underwent facile exchange with free naphthalene, and addition of anthracene into a solution of 2 resulted in clean formation of an anthracene complex [{K₂(dme)₃}(O₃C)Zr(C₁₄H₁₀)] (3). The reaction of 2 with an excess of Me₃SiN₃ involves generation of an imide intermediate via extrusion of N₂ and Si-N bond cleavage, and an amide complex [{K(thf)₂}(O₃C)Zr{N(SiMe₃)₂}(thf)] (4) was isolated. Analogously, treatment of 2 with mesityl azide (MesN₃) followed by addition of Me₃SiN₃ afforded [{K(thf)₂}(O₃C)Zr{N(Mes)(SiMe₃)}(thf)] (5). Hydrogenation of 2 provided a hydride-bridged dizirconium complex [{K(thf)₂}₃{(O₃C)Zr}₂(μ-H)₃] (6) along with tetralin. The solid-state structures of 2, 4, and 5 were established by single-crystal X-ray diffraction studies.