Bimetallic Cr,Ru alkenyl carbene derivatives: Synthesis from organometallic prop-2-yn-1-ols and stereochemical aspects

The reaction of RuCl2(PMe3)(eta 6-C6Me6) 1 with HC=C-CHOH-(2-MeO-C6H4) 2 and NaPF6 in methanol led to the trans-alkenylcarbene complex [LnRu=C(OMe)CH=CH(2-MeO-C6H4)]PF6 3 (LnRu = Ru(Cl)(PMe3)(eta(6)-C6Me6)) with the s-cis conformation of the carbene ligand. The activation by 1 of the racemic and of the (S,S) stereoisomer of the organometallic alcohol HC=CCOH(eta(6)-(2Me-C6H4)Cr(CO)(3) 4 afforded the same two diastereoisomers [LnRu=C(OMe)CH=CH(eta(6)-(2-Me-C6H4)Cr(CO)(3)]PF6 5a/b with low stereoselectivity in the ratio 55:45 (80%) and in the s-cis conformation. By contrast, the activation of HC=CCOH(Me)(eta(6)-C6H5)Cr(CO)(3) 8 by 1 led to two diastereoisomers [LnRu=C(OMe)CH=CMe(eta(6)-C6H5)Cr(CO)(3)]PF6 9a/b (64:34) with the s-trans conformation of the organometallic carbene ligand.