Addition of CF3C02H to a CHzClz solution of N ( C H~C H , )~+ ( C O ) S W C H ( O C H~) C~H~-(5) at -78 OC produces a red solution of ( C O ) S W C H C~H~ (4), which was characterized by low-temperature ' H N M R and by reaction with P(n-Bu3) to give (C0)5WCH [ P (~-B U )~] C~H~ (6). Thermal decomposition of 4 at -56 OC occurs with a half-life of 24 min. The reaction of 4 with alkenes occurs rapidly at -78 " C to give phenylcyclopropanes; no metathesis-like products were observed. The relative reactivity of alkenes toward 4 was in theorder CH>=C(CH3)2 > CH2=CHCH3 >> CHz=CHl, indicating that the reaction involved electrophilic attack of the carbene complex on the alkene. The stereochemistry of cyclopropane formation could not be explained in terms of formation of the most stable intermediate metallacyclobutane. The stereochemistry of cyclopropane formation is explained in terms of transition state 25 which involved formation of a bond from the carbene carbon atom of 4 to the less substituted end of an alkene and interaction of the positively polarized, more substituted end of the alkene with the ipso carbon atom of the phenyl group of 4

No abstract

Photolysis of (C0)5WCOR-leads to loss of CO and formation of (C0)5WR-. Reaction of RLi with (C0)5WBr-also gives (C0)5WR-species. Reaction of (C0)5WR-with HCI leads to protonation of the carbon-metal bond and formation of RH. Treatment of (C0)5WR-with CO or with P(C&s)3 leads to carbonyl insertion products when R = CH3 or C6H5 but not when R = cH2csI-I~.

CDCl3) 6 7.57 (m, 15 H, ph3P+-), 6.97 (m, 5 H. CsH5). 3.62 (d Of t, 1 H, h p -~