Oxidative addition capability of triphosphine iron and ruthenium complexes with methyl iodide

Abstract

The ruthenium and iron dicarbonyl complexes Ru(MeP(CH 2CH 2PMe 2) 2)(CO) 2 ( 1), Ru(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2 ( 2) and Fe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2 ( 3) bearing strong donor tridentate phosphine ligands were prepared and fully characterised. The structures of the complexes have been established by X-ray diffraction studies. Oxidative addition of MeI to 1– 3 proceeds instantaneously at room temperature and affords the corresponding octahedral cationic complexes fac, cis-[RuMe(MeP(CH 2CH 2PMe 2) 2)(CO) 2]I ( 5a) and mer, cis-[RuMe(MeP(CH 2CH 2PMe 2) 2)(CO) 2]I ( 5b), mer, trans-[MMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6a (M=Ru); 7a (M=Fe)) and mer, cis-[MMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6b (M=Ru); 7b (M=Fe)), respectively. The triphosphine preferentially adopts a facial arrangement in the case of the ethylene bridged tridentate ligand ( 5a) and a meridional arrangement in the case of the trimethylene bridged ligand ( 6a– 7b). mer, cis-[RuMe(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 6a) undergoes CO insertion to the acetyl complex mer, trans-[Ru(COMe)(MeP(CH 2CH 2CH 2PMe 2) 2)(CO) 2]I ( 8). Attempts to produce a ketene complex from the deprotonation of 8 were not successful. The acetyl protons in 8 show very low acidity and no reaction occurred when the complex was reacted with bases such as DBU, BEMP (2-tert-Butylimino-2-diethylamino-1,3-dimethyl-perhydro-1,3,2-diazaphosphorine) or LDA.