SUBSTITUTION EFFECTS AT BRIDGING VINYL LIGANDS - MOLECULAR-STRUCTURES OF [OS3H(CH=CHR)(CO)10] WHERE R = OET OR FERROCENYL

The two related compounds [Os3H(μ,η2-trans-CHCHR)(CO)10] (R = OEt or ferrocenyl C5H4FeC5H5, Fc), have been prepared, the first by insertion of ethyl ethynyl ether (CHCOEt) into [Os3H2(CO)10] and the second by oxidative addition of ethynylferrocene (CH2 = CHFc) to [Os3(CO)10(MeCN)2] respectively. Spectroscopically both compounds are similar to known related compounds with alkyl- or aryl-substituted vinyl ligands. A single-crystal X-ray structural study of each was made in an attempt to detect any structural effects of π-donation by the substituents at the vinyl group, such as was observed for [Os3H(CHCHNEt2)(CO)10]. The latter compound has been shown to have a zwitterionic structure with an alkylidene bridge between two osmium atoms rather than the normal μ,η2-vinyl mode of bondiong. The two compounds studied here have essentially normal μ,η2-vinyl bridges, but with some distortion towards the alkylidene bonding type, more pronounced for R = OEt. © 1990.