The Reactivity of Ditetrelenes Towards Organophosphorus Oxides
Abstract
The reactivity of tetramesityldisilene 4 and tetramesityldigermene 5 towards organophosphorus oxides was explored in this thesis. The reaction of dialkyl and diarylphosphine oxides and phosphites with ditetrelenes 4 and 5 resulted in a 1,3-addition to form diorganodisilyl and digermyl phosphinites 27, 28, 31, 32 and disilyl phosphites 35 and 36. The 1,3-addition resulted in a mild two electron reduction of the P(V) centre of the phosphine oxide and phosphite to a P(III) centre in the products, without the use of heat or a catalyst. The reaction of organophosphorus oxides provides another example of a main group oxide that can be activated by ditetrelenes 4 and 5 in addition to nitro and sulfonyl containing compounds, CO and CO2.
The mechanism for the reaction of diorganophosphorus oxides and phosphites with ditetrelenes 4 and 5 was investigated through deuterium labelling studies and KIE experiments. The mechanism for the formation of disilyl and digermyl phosphinites and phosphites was determined to proceed through a nucleophilic addition. An exchange phenomenon between the OP(pentyl)2 moiety of 32 and an OPPh2 group from diphenylphosphine oxide was discovered and insights into the mechanism of this exchange were obtained.