title: Functionalization of Complexed N2O in Bis(pentamethylcyclopentadienyl) Systems of Zirconium and Titanium.
abstract: Methyl triflate reacts with the metastable azoxymetallacyclopentene complex Cp*2Zr(N(O)NCPhCPh), generatedin situfrom nitrous oxide insertion into the Zr-C bond of Cp*2Zr(η2-PhCCPh) at -78 °C, to afford the salt [Cp*2Zr(N(O)N(Me)CPhCPh)][O3SCF3] (1) in 48% isolated yield. A single-crystal X-ray structure of1features a planar azoxymetallacycle with methyl alkylation taking place only at the β-nitrogen position of the former Zr(N(O)NCPhCPh) scaffold. In addition to1, the methoxy-triflato complex Cp*2Zr(OMe)(O3SCF3) (2) was also isolated from the reaction mixture in 26% yield and fully characterized, including its independent synthesis from the alkylation of Cp*2Zr=O(NC5H5) with MeO3SCF3. Complex2could also be observed, spectroscopically, from the thermolysis of1(80 °C, 2 days). In contrast to Cp*2Zr(N(O)NPhCCPh), the more stable titanium N2O-inserted analogue, Cp*2Ti(N(O)NCPhCPh), reacts with MeO3SCF3to afford a 1:1 mixture of regioisomeric salts, [Cp*2Ti(N(O)N(Me)CPhCPh)][O3SCF3] (3) and [Cp*2Ti(N(OMe)NCPhCPh)][O3SCF3] (4), in a combined 65% isolated yield. Single-crystal X-ray diffraction studies of a cocrystal of3and4show 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*2Ti(N(O)NCPhCPh) with KC8, 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*2Ti(N(O)NCPhCPh)] (5) in 68% yield. Complex5was 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(z2)/d(x2-y2), houses the unpaired electron, without perturbing the azoxymetallacycle core in Cp*2Ti(N(O)NCPhCPh). Theoretical studies of Ti and the Zr analogue are also presented and discussed.
authors: Searle Chemistry Laboratory, Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States.
authors: Daniel J
authors: DJ
authors: Mindiola
authors: Searle Chemistry Laboratory, Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States.
authors: Lori A
authors: LA
authors: Watson
authors: Searle Chemistry Laboratory, Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States.
authors: Karsten
authors: K
authors: Meyer
authors: Searle Chemistry Laboratory, Department of Chemistry, The University of Chicago , Chicago, Illinois 60637, United States.
authors: Gregory L
authors: GL
authors: Hillhouse