Electron-rich siloxane--platinum complexes--synthesis, structures, and reactivity

New platinasiloxanes were synthesized and their reactivity was studied. Oxidative addition of [(HSi[Me.sub.2]).sub.2]O to Pt[(P[Et.sub.3]).sub.3] led to dehydrogenation and quantitative formation of the four-membered platinacyclosiloxane [[(P[Et.sub.3]).sub.2]Pt([(Si[Me.sub.2]).sub.2]O)] which was characterized by X-ray diffraction. This complex was stable towards non-polar substrates and aerobic conditions, but reacted readily with electrophiles and Lewis acids. Reaction with MeI resulted in ring opening, while MeOTf gave an oxonium complex, with retention of the platinacycle structure. A complex resulting from B[F.sub.3] coordination to the ring oxygen atom was also obtained. An unprecedented open-chain diplatinasiloxane containing the Pt-Si-O-Si-O-Si-Pt fragment was formed by oxidative addition of H-Si[Me.sub.2]-O-Si[Me.sub.2]-O-Si[Me.sub.2]-H to Pt(P[Et.sub.3]).sub.3] and it was characterized by X-ray diffraction. Key words: cyclosiloxane, metallacycle, platinum silyl, Lewis base, oxidative addition. On a realise la synthese de nouveaux platinasiloxanes et on en a etudie la reactivite. L'addition oxydante du [(HSi[Me.sub.2]).sub.2]O] a du Pt[(P[Et.sub.3]).sub.3] conduit a une deshydrogenation et a la formation quantitative du platinacyclosiloxane a quatre chainons [[(P[Et.sub.3]).sub.2]Pt([(Si[Me.sub.2]).sub.2]O)] qui a ete caracterise par diffraction des rayons X. Ce complexe est stable vis-a-vis des substrats non polaires et des conditions aerobiques, mais il reagit facilement avec les electrophiles et les acides de Lewis. Sa reaction avec du MeI conduit a une ouverture de cycle, alors que sa reaction avec du MeOTf conduit a la formation d'un complexe d'oxonium, avec retention de la structure platinacyclique. Un complexe resultant de la coordination du B[F.sub.3] a l'atome d'oxygene du cycle a aussi ete obtenu. L'addition oxydante de H-Si[Me.sub.2]-O-Si[Me.sub.2]-O-Si[Me.sub.2]H a du Pt[(P[Et.sub.3]).sub.3] conduit d'un diplatinasiloxane a chaine ouverte contenant le fragment Pt-Si-O-Si-O-Si-Pt inconnu jusqu' a maintenant et qui a ete caracterise par diffraction des rayons X. Mots cles : cyclosiloxane, metallacyclique, silyle platine, base de Lewis, addition oxydante. [Traduit par la Redaction]