作者:Laura R. Groom、Adam F. Russell、Andrew D. Schwarz、Philip Mountford
DOI:10.1021/om4011752
日期:2014.2.24
We report the first reactivity study of a transition-metal benzimidamido complex, namely Cp*TiPhC((NPr)-Pr-i)(2)}NC(Ar-F5)(NOBu)-Bu-t} (5, Ar-F5 = C6F5). Reaction with CO2 and (BuNCO)-Bu-t gave the cycloaddition products Cp*Ti[PhC((NPr)-Pr-i)(2)}OC(O)N(C(ArNOBu)-N-F5-Bu-t)} and Cp*Ti[PhC((NPr)-Pr-i)(2)}OC((NBu)-Bu-t)N(CAr-F5}(NOBu)-Bu-t)} (10), respectively, whereas with CS2 slow extrusion of ArFcCN from 5 occurred to ultimately form Cp*TiPhC((NPr)-Pr-i)(2)}SC(S)N((OBu)-Bu-t)}. Reaction of 5 with ArC(O)H (Ar = Ph, 4-C6H4Me, 4-(C6H4Bu)-Bu-t, 4-C6H4OMe, 4-C6H4NMe2, 4-C6H4CF3) also gave the isolable metallacyclic complexes Cp*TiPhC(NiPr)(2)}[N(CAr-F5}(NOBu)-Bu-t)C(Ar)(H)O} (13) via reversible [2 + 2] cycloaddition reactions. In contrast, reaction with HC(O)NMe2 formed Me2NNC(Ar-F5)(NOBu)-Bu-t}H (16) within 1 h at room temperature. Upon heating, 10 and 13 also underwent retrocyclization, forming the organic products (BuNCNC)-Bu-t(Ar-F5)(NOBu)-Bu-t and ArCNC(Ar-F5)(NOBu)-Bu-t}H (14), respectively. Selected examples of 14 and 16 were studied by DFT and UV visible spectroscopy. Addition of isonitriles (BuNC)-Bu-t and XyINC (Xyl = 2,6-C6H3Me2) to Cp*TiPhC(NiPr)(2)}NC(Ar)(NOBu)-Bu-t} (Ar = Ar-F5 (5), 2,6-C6H3F2 (Ar-F2)) afforded the sigma adducts Cp*TiPhC((NPO2)-P-i}NC(Ar)(NOBu)-Bu-t}(CNR) (Ar = ArF5, R = Bu-t, Xyl (19); Ar = Ar-F2, R = Xyl). Subsequently, 19 formed Cp*TiPhC((NPr)-Pr-i)(2)}NC((NOBu)-Bu-t)C6F4N(Xyl)C}(F) (20) via C-F bond activation. Reaction of 5 with 2 equiv of B(Ar-F5)3 gave Cp*TiPhC((NPr)-Pr-i)(2)}ON(BAr-F5}(3))C(Ar-F5)N(H)(BAr-F5}}(3))} with elimination of 2-methylpropene.