[2+2]-Cycloaddukte PH-funktioneller Phosphenium-Komplexe mit Alkylisothiocyanaten: Darstellung von C5R5(OC)2 (R=H, Me; M=Mo, W; R′=Me, Et, t-Bu) und Reaktion unter Beanspruchung der PH-Funktion

Abstract The phosphenium complex C 5 Me 5 (OC) 2 WP(H) t -Bu ( 2c ) reacts with the alkylisothiocyanates RNCS (R=Me, Et, t -Bu) ( 3a – c ) via [2+2]-cycloaddition to form the PH-functionalized phosphametallacycles C 5 Me 5 (OC) 2 W–P(H)(t-Bu)–C(NR)–S (R=Me, Et, t -Bu) ( 4a – c ). In the case of the Cp-substituted phosphenium complexes Cp(OC) 2 MP(H) t -Bu (M=Mo, W) ( 2a , b ) additional insertion of the isothiocyanate into the PH bond occurs yielding the cycloadducts Cp(OC) 2 M–P[C(S)NHR](t-Bu)–C(NR)–S (M=Mo, W; R=Me, Et, t -Bu) ( 5a – c ) with high diastereoselectivity. The analogous C 5 Me 5 -substituted compounds C 5 Me 5 (OC) 2 W–P[C(S)N(H)R](t-Bu)–C(NR)–S (R=Me, t -Bu) ( 5d , e ) are only obtained by treatment of 2c with a large excess of 3a , c . Insertion is realized as a separate step for 4c and EtNCS ( 3b ) leading to the formation of isomeric C 5 Me 5 (OC) 2 W–P[C(S)N(H)R 1 ](t-Bu)–C(NR 2 )–S [R 1 =Et, R 2 = t -Bu ( 6a ); R 1 = t -Bu, R 2 =Et ( 6b )]. The structure of 5d is characterized by X-ray diffraction analysis.