Polyoxometalate-Catalyzed Insertion of Oxygen from O_2 into Tin-Alkyl Bonds

摘要

The polyoxometalate H_5PV_2Mo_(10)O_(40) mediates the insertion of an oxygen atom from H_5PV_2Mo_(10)O_(40) into the tin-carbon bond of n-Bu_4Sn through its activation by electron transfer to yield 1-butanol and (n-Bu_3Sn)_2O. The reaction is initiated by electron transfer from n-Bu_4Sn to H_5PV_2Mo_(10)O_(40) to yield the ion pair n-Bu_4Sn~(·+)-H_5PV~(Ⅳ)V~ⅤMo_(10)O_(40). The H_5PV_2Mo_(10)O_(40) moiety was identified by UV-vis and EPR. DFT calculations show that n-Bu_4Sn~(·+)-H_5PV~(Ⅳ)V~ⅤMo_(10)O_(40) is relatively unstable and forms more stable Bu~+ and Bu_3Sn~+ cations coordinated to the polyoxometalate, which were also identified by ESI-MS. Products are released at higher temperatures. In the presence of molecular oxygen as the terminal oxidant the reaction is catalytic.