Reactions of a Cyclopentadienyl–Amidinate Titanium Benzimidamido Complex

We report the first reactivity study of a transition-metal benzimidamido complex, namely Cp*Ti{PhC(N i Pr) 2 }{NC(Ar F 5 )NO t Bu} ( 5, Ar F 5 = C 6 F 5 ). Reaction with CO 2 and t BuNCO gave the cycloaddition products Cp*Ti{PhC(N i Pr) 2 }{OC(O)N(C{Ar F 5 }NO t Bu)} and Cp*Ti{PhC(N i Pr) 2 }{OC(N t Bu)N(C{Ar F 5 }NO t Bu)} ( 10 ), respectively, whereas with CS 2 slow extrusion of Ar F 5 CN from 5 occurred to ultimately form Cp*Ti{PhC(N i Pr) 2 }{SC(S)N(O t Bu)}. Reaction of 5 with ArC(O)H (Ar = Ph, 4-C 6 H 4 Me, 4-C 6 H 4 t Bu, 4-C 6 H 4 OMe, 4-C 6 H 4 NMe 2, 4-C 6 H 4 CF 3 ) also gave the isolable metallacyclic complexes Cp*Ti{PhC(N i Pr) 2 }{N(C{Ar F 5 }NO t Bu)C(Ar)(H)O} ( 13 ) via reversible [2 + 2] cycloaddition reactions. In contrast, reaction with HC(O)NMe 2 formed Me 2 N{NC(Ar F 5 )NO t Bu}H ( 16 ) within 1 h at room temperature. Upon heating, 10 and 13 also underwent retrocyclization, forming the organic products t BuNCNC(Ar F 5 )NO t Bu and ArC{NC(Ar F 5 )NO t Bu}H ( 14 ), respectively. Selected examples of 14 and 16 were studied by DFT and UV–visible spectroscopy. Addition of isonitriles t BuNC and XylNC (Xyl = 2,6-C 6 H 3 Me 2 ) to Cp*Ti{PhC(N i Pr) 2 }{NC(Ar)NO t Bu} (Ar = Ar F 5 ( 5 ), 2,6-C 6 H 3 F 2 (Ar F 2 )) afforded the σ adducts Cp*Ti{PhC(N i Pr) 2 }{NC(Ar)NO t Bu}(CNR) (Ar = Ar F 5, R = t Bu, Xyl ( 19 ); Ar = Ar F 2, R = Xyl). Subsequently, 19 formed Cp*Ti{PhC(N i Pr) 2 }{NC(NO t Bu)C 6 F 4 N(Xyl)C}(F) ( 20 ) via C–F bond activation. Reaction of 5 with 2 equiv of B(Ar F 5 ) 3 gave Cp*Ti{PhC(N i Pr) 2 }{ON(B{Ar F 5 } 3 )C(Ar F 5 )N(H)(B{Ar F 5 } 3 )} with elimination of 2-methylpropene.