Ring Formation and Expansion

Tetrafluoroethylene reacts with Fe(CO)3(butadiene) by a two-step oxidative addition process to give (43). The reaction of the rhodium(i) complex Rh(acac)(cod) with hexafluorobut-2-yne results both in trimer-ization of this alkyne, and either its insertion into a y-bonded acetyl-acetonate intermediate or a concerted addition to the acetylacetonate ring, to produce (44), RhCl3,3H20 reacts with 2-methylallyl alcohol, in the presence of 4-methylpyridine (pic), probably via two insertion reactions, to 

The reaction of (48) with an excess of hexafluoroacetone in ether gives either (49) or (50). The mechanism of this insertion and ring-expansion reaction may involve oxidative addition of the hexafluoroacetone to (48) to give the platinum(iv) intermediate (51). A similar mechanism probably 

The mechanism for the conversion of the perfluorocyclobutenyl group on platinum in (56) to a furyl group (57) may involve attack of water at the perfluorocyclobutenyl-carbon bonded to the platinum, conversion into an 

The converse reaction, of attack of carbon monoxide at, for instance, co-ordinated azide, is also observed. Thus carbonylation of Pt(NCO)-(N3)(PPh3)a in ethanol gives some Pt(NCO)2(PPh8)a, and Mof/t -CsHs)-(N3)(CO)(PPh3 2 reacts with carbon monoxide when irradiated to give 

Reactions whose mechanism involves nucleophilic attack at carbonyl-C rather than at metal centres compounds arranged by Periodic Table order of metals 

---

These reactions can also be adapted to carbocyclic ring formation and expansion. ch3 ch3... 

---