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

The ruthenium and iron dicarbonyl complexes Ru(MeP(CH2CH2PMe2)2)(CO)2 (1), Ru(MeP(CH2CH2CH2PMe2)2)(CO)2 (2) and Fe(MeP(CH2CH2CH2PMe2)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(CH2CH2PMe2)2)(CO)2]I (5a) and mer,cis-[RuMe(MeP(CH2CH2PMe2)2)(CO)2]I (5b), mer,trans-[MMe(MeP(CH2CH2CH2PMe2)2)(CO)2]I (6a (M=Ru); 7a (M=Fe)) and mer,cis-[MMe(MeP(CH2CH2CH2PMe2)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(CH2CH2CH2PMe2)2)(CO)2]I (6a) undergoes CO insertion to the acetyl complex mer, trans-[Ru(COMe)(MeP(CH2CH2CH2PMe2)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.