Functionalization of Complexed N(2)O in Bis(pentamethylcyclopentadienyl) Systems of Zirconium and Titanium

[Image: see text] Methyl triflate reacts with the metastable azoxymetallacyclopentene complex Cp*(2)Zr(N(O)NCPhCPh), generated in situ from nitrous oxide insertion into the Zr–C bond of Cp*(2)Zr(η(2)-PhCCPh) at −78 °C, to afford the salt [Cp*(2)Zr(N(O)N(Me)CPhCPh)][O(3)SCF(3)] (1) in 48% isolated yield. A single-crystal X-ray structure of 1 features a planar azoxymetallacycle with methyl alkylation taking place only at the β-nitrogen position of the former Zr(N(O)NCPhCPh) scaffold. In addition to 1, the methoxy-triflato complex Cp*(2)Zr(OMe)(O(3)SCF(3)) (2) was also isolated from the reaction mixture in 26% yield and fully characterized, including its independent synthesis from the alkylation of Cp*(2)Zr=O(NC(5)H(5)) with MeO(3)SCF(3). Complex 2 could also be observed, spectroscopically, from the thermolysis of 1 (80 °C, 2 days). In contrast to Cp*(2)Zr(N(O)NPhCCPh), the more stable titanium N(2)O-inserted analogue, Cp*(2)Ti(N(O)NCPhCPh), reacts with MeO(3)SCF(3) to afford a 1:1 mixture of regioisomeric salts, [Cp*(2)Ti(N(O)N(Me)CPhCPh)][O(3)SCF(3)] (3) and [Cp*(2)Ti(N(OMe)NCPhCPh)][O(3)SCF(3)] (4), in a combined 65% isolated yield. Single-crystal X-ray diffraction studies of a cocrystal of 3 and 4 show a 1:1 mixture of azoxymetallacyle salts resulting from methyl alkylation at both the β-nitrogen and the β-oxygen of the former Ti(N(O)NCPhCPh ring. As opposed to alkylation reactions, the one-electron reduction of Cp*(2)Ti(N(O)NCPhCPh) with KC(8), followed by encapsulation with the cryptand 2,2,2-Kryptofix, resulted in the isolation of the discrete radical anion [K(2,2,2-Kryptofix)][Cp*(2)Ti(N(O)NCPhCPh)] (5) in 68% yield. Complex 5 was studied by single-crystal X-ray diffraction, and its solution X-band EPR spectrum suggested a nonbonding σ-type wedge hybrid orbital on titanium, d(z(2))/d(x(2)–y(2)), houses the unpaired electron, without perturbing the azoxymetallacycle core in Cp*(2)Ti(N(O)NCPhCPh). Theoretical studies of Ti and the Zr analogue are also presented and discussed.