Coordination chemistry of alkali metal dimesityl-thio- and dimesityl-selenophosphinites [(L)2A-EPMes2]2 (A = Li, Na, K; E = S, Se; L = THF, THP) and [(18C6)K-SPMes2].

The reactions of dimesitylphosphane oxide Mes₂P(O)H with Lawessons reagent and dimesitylphoshane with selenium yield Mes₂P(E)H with E = S (1a) and E = Se (1b), respectively, with moderate yields. Metalation of dimesitylphosphane sulfide 1a with n-butyllithium, sodium hydride or potassium hydride in THF allows the isolation of dinuclear dimesityl-thiophosphinites of the type [(thf)₂A-S-PMes₂]₂ [A = Li (4), Na (5), K (2a)] with central four-membered A₂S₂ rings. The weaker base THP leads to the very similar aggregate [(thp)₂K-S-PMes₂]₂ (3a) as has also been observed for the homologous potassium dimesityl-selenophosphinites of the type [(L)₂K-Se-PMes₂]₂ [L = thf (2b), thp (3b)]. Addition of 18-crown-6 ether leads to deaggregation and expectedly to formation of mononuclear [(18C6)K-S-PMes₂] (6). Moderate yields have been obtained due to dismutation reactions that yield the corresponding phosphinates AE₂PMes₂ and phosphanides APMes₂, a degradation process which has been observed earlier also for Li-O-PMes₂. This side reaction hampers the application of these thio- and selenophosphinites as catalysts in the addition of phosphane sulfides and selenides across alkynes. [ABSTRACT FROM AUTHOR]