如何有效的利用组会资源.ppt

Possible Solution Structure of Zirconocene-1-aza-1,3-diene Complex ? The ring flipping is fast at the NMR time scale and the average A/A’ and B/B’ resonances has been observed ? The equilibrium mixture of A/A’ and B/B’ is established but one pair is highly populated ? There is a high kinetic barrier for A/A’?B/B’ interconversion and one of the two pairs is kinetically formed during the synthesis VT NMR of 2a (–60°C-70°C) showed no difference DFT Calculation The equilibrium mixture of A/A’ and B/B’ is established but one pair is highly populated Reactivity of Zirconocene-1-aza-1,3-diene Complex 4a (R = H, 87%) 4b (R = OCH3, 88%) 5a (R = H, 91%) 5b (R = OCH3, 90%) 5a Zr-N1: 2.17 ?; Zr-O1: 1.96 ? Cp1Cp2: 52.9° Reactivity of Zirconocene-1-aza-1,3-diene Complex Kinetic Study of Ketone Insertion into Zr-C Bond of Zirconocene-1-aza-1,3-diene Complex Kinetic Study of Ketone Insertion into Zr-C Bond of Zirconocene-1-aza-1,3-diene Complex Disappearance of zirconacycle 2a as a function of time in toluene-d8 at 60oC [2a] = 1.40х10-2M [2a] = 3.00х10-2M [2a] = 3.80х10-2M [2a] = 4.60х10-2M Under pseudo-first-order conditions the disappearance of 2a follows exponential decay. Plots of kobs as a funcation of PhCOPh concentration in toluene-d8 at 60oC k(M-1s-1) 2a 1.3 х 10-3 3a 4.6 х 10-4 2b 3.0 х 10-4 3b 1.7 х 10-4 The ansa-bridged Cp systems are more reactive than the bisCp systems: insertion rates for 2a and 2b are about 2.8 and 1.8 times faster than 3a and 3b, respectively. An electron-rich aryl group on N disfavors ketone insertion: insertion rates for 2a and 3a are about 4.3 and 2.7 times faster than 2b and 3b, respectively. 2a 3b 3a 2b k(M-1s-1) 75oC 4.0 х 10-3 70oC 2.4 х 10-3 60oC 1.3 х 10-3 55oC 8.8 х 10-4 ?H≠ = 66.6 KJ/mol ?S≠ = -101.3 J/mol?K The negative entropy change is consistent with a transition state that brings the zirconium complex and the ketone together prior to insertion Eyring Plot for the reaction between 2a and PhCOPh in toluene-d8 Kinetic Study of