| Popis: |
Alkenyldiphenylphosphines, CH 2 CH(CH 2 ) n PPh 2 (alkP; n =1-4), react with c is-(pip) 2 W(CO) 4 (pip=piperidine) to afford cis -(pip)(alkP)W(CO) 4 complexes in which alkP is coordinated through P. Two of these complexes ( n =2, 3) react via chelate ring closure either photochemically or thermally to afford, in high yield, (ηn 3 -alkP)W(CO) 4 products in which alkP functions as a chelating ligand; for the other two ( n =1, 4), such products were observed in solution but could not be isolated. In contrast to observations for other complexes containing both phosphine and olefin functionalities, olefin bond migration was not observed to take place. This observation is attributed the ‘direction’ of the syntheses, which, for olefin bond migration to take place requires initial coordination of the alkP ligands through CC rather than through P. The influence of the nature of the chelate ring backbone on the outcome of such reactions is also discussed. |
