Stepwise Synthesis of Siloxane‐Substituted Oligophosphanes P n [O( i Pr 2 Si) 2 ] 2 ( n = 2, 4)

The synthesis of siloxane‐bridged P 2 and P 4 compounds can be achieved through metalation of primary or cyclic diphosphanylsiloxane compounds and subsequent oxidative coupling using C 2 H 4 Br 2 as reagent. Starting from the cyclic diphosphanylsiloxane [O( i Pr 2 Si) 2 PH] 2 , the reaction with the silazanides of the earth alkaline metals leads to the metalated compounds [M(DME) 2 {O( i Pr 2 Si) 2 P} 2 ] ( 1 : M = Ca, 2 : M = Sr, 3 : M = Ba). Subsequent oxidation yields the bicyclic species P 2 [O( i Pr 2 Si) 2 ] 2 ( 4 ). In an analogous reaction sequence with the primary diphosphanylsiloxane O( i Pr 2 Si) 2 PH 2 the cyclic diphosphane O( i Pr 2 SiPH) 2 ( 5 ) could be obtained and was successfully used for the same reaction pathway, leading to the corresponding metalated compound 6 . Further oxidative coupling resulted in an intermolecular P–P bond formation, yielding the cage compound P 4 [O( i Pr 2 Si) 2 ] 2 ( 7 ).