t75-C5H5)W(NO)2(P(OPh)3)].12 There is little difference in the average W-N-0 bond angles between the 19-electron complex and the 18-electron [(773-C5H5)W(NO)2Cl]2 5°c omplex. However, there is much discussion in the literature20 about the influence of electron density on M-N-0 bond angles in metal nitrosyl complexes. The major difference in structure is the substantially larger N-W-N bond angle in this 19-electron complex compared to that in the 18-electron analogue.21 The differences between the 18-and 19-electron structures are readily interpreted in terms of a MO calculation by Hall and co-workers.22 These authors indicate that the 19th electron will occupy an orbital that has substantial 2ir(NO) character. Nevertheless, in the case of [Mo(NO)2L2Cl2], the other ligands such as Cl contribute to this MO. Two kinds of stereochemistry are observed for Mo(NO)2L2Cl2 complexes: m-dinitrosyl-cw-dichloro (L = MeCN, py) and ds-dinitrosyl-i/wu-dichloro (L2 = bpy). For the first type, the Mo-Cl bond is labilized in the 19-electron state; for the second type, the Mo-Cl bond is more stable in the 19-electron state. The key features of the chloride elimination are (i) the reduction of the [Mo(NO)2L2Cl2] complexes to their 19-electron anions and (ii) the rapid chloro ligand exchange of the paramagnetic intermediate. The multistep reduction produces trichloro and tetrachloro complexes, which are reducible at a more negative potential than the dichloro complexes. The multiple-step (22) Morris-Sherwood, B.
~ Perfluorobicyclobutylidene (3) readily forms cycloadducts with butadiene, cyclopentadiene, 6,6dimet hylfu lvene and furan, whereas perf1 uoro-3,4-dimethyl hex-2-ene (2) is unreactive under the same conditions. This marked difference in reactivity between (2) and (3) is attributed to angle strain in (3). Reaction of the alkene (3) with cyclohexa-I ,3-diene yields 1 H,l 'H-perfluorobicyclobutyl (9) and benzene, by hydrogen transfer. The alkene (3) undergoes an 'ene' reaction with propene. Epoxides of perfluorobicyclobutylidene (3) and perfluorobicyclopentylidene (1 1 ) have been prepared; they both show high thermal stability and the latter epoxide fragments in the presence of fluoride ion t o yield perfluorocyclopentene and perfluorocyclopentanone. Part 31, ref. 15.
Reactions of alkenes that are oligomers of tetrafluoroethene or hexafluorocyclobutene with sodium hypochlorite give epoxides which show remarkable overall stability. Ring-opening reactions, induced by fluoride ion, yield alkenes, ketones, and acid fluorides.
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