Conversion of alkynes and nitriles into organo and organonitrogenated species at group VI and VII dinitrogen-binding metal centers. Synthesis of some vinylidene and alkynyl complexes of rhenium

摘要

The reactions of phenylacetylene and other alkynes HC≡CCH2OH, HC≡C(CH2)2OH, HC≡CCH2CMe2CH2COCH3, HC≡CSiMe3andMeC≡CSiMe3, in the presence of acetonitrile or benzonitrile, with the following complexes have been investigated usually at room temperature:trans-Mo(N2)2L4 (L=PMe2Ph),cis-Mo(N2)2(PMePh2)4,cis-W(N2)2L4,trans-ReCl(N2)L4,mer-ReCl(N2)(PPh3)L′3 {L′=P(OMe)3}, ReCl2(N2COPh)L′3 and (η5-MeC5H4)Mn(CO)2(NCMe). Cyclic trimerization was the main reaction detected for phenylacetylene (except for the Mn complex), although dimers, products of hydrogenation and species derived from alkyne/nitrile coupling were also formed in smaller amounts; for the Mo- or W-systems, the total yields were below ca. 40 relative to the metal, but the Re-systems exhibited a modest catalytic activity. The other alkynes underwent, also in low yields, mainly dimerization, cyclic or linear trimerization, apart from, to a smaller extent, coupling reactions with the nitriles or hydrogenation. The alkynyl complexes ReCl(C≡CPh) {P(O) (OMe)2}(PPh3)L′2 and ReCl(C≡CPh) {P(O)(OMe)2}(NCMe)2L′ were prepared by reaction ofmer-ReCl(N2)(PPh3)L′3 withPhC≡CH, in the absence and in the presence of NCMe, respectively, whereas the benzonitrile/dinitrogen complex ReCl(N2)(CNPh)L′3 was obtained either by reaction of that N2-complex with NCPhor by the reaction of ReCl2(N2COPh)L′3 with NCPhin the presence of NaOMe. The vinylidene compoundtrans-Re(CNMe)(C=CHPh)(dppe)2BF4 (dppe=Ph2PCH2CH2PPh2) was formed by reaction oftrans-ReCl(CNMe)(dppe)2 withPhC≡CH, in the presence of TlBF4, which did not lead to the formation of detectable amounts of