REACTIONS OF SOME GROUP 15 LIGANDS WITH [(ETA-5-INDENYL)FE(CO)3]BF4

[(eta5-Indenyl)Fe(CO)3]BF4 (I) undergoes facile monocarbonyl substitution at room temperature in acetone by monophosphines, monophosphites and MPh3 (M = As, Sb, Bi) ligands (L) to form [(eta5-Indenyl)Fe(CO)2L]BF4. Ditertiary phosphines, PPh2(CH2)n PPh2 (n = 1, 2, 4, 6, 8) and both the arsines, AsPh2(CH2)2AsPh2 and AsMe2(CH2)5AsMe2 react similarly to form monosubstituted complexes e.g. [(eta5-Indenyl)Fe(CO)2(eta1-PPh2(CH2)nPPh2)]BF4 and dimeric complexes, e.g. [{(eta5-Indenyl)Fe(CO)2}2-mu-PPh2(CH2)nPPh2)][BF4]2 Prolonged refluxing of I with these ligands gives the chelates, e.g. [(eta5-Indenyl)Fe(CO)(eta2-PPh2(CH2)nPPh2)]BF4. The enhanced reactivity of the [(eta5-Indenyl)Fe(CO)3]+ cation over that of [(eta5-C5H5)Fe(CO)3]+ in solvents such as acetone may be attributed to the ''indenyl'' effect, i.e. ring slippage from eta5 to eta3. However, no evidence was obtained for intermediates such as [(eta3-C9H7)Fe(CO)3(acetone)]+, and so the effect must operate solely in the transition state of the reaction.