Ru(CO)4(PMe2Ph) catalyzed carbonylation of Ru(CH3)I(CO)2(iPr-DAB) and Ru(CH3)I(CO)2(iPr-Pyca) complexes. X-ray structure of [Ru(CH3)(CO)2[(2-methoxyethyl)Pyca]][OTf]

Article abstract of DOI:10.1021/om00020a046

The synthesis and characterization of complexes Ru(R)X(CO)₂(R′-Pyca) (R = CH₃ and X = I (2); R = C(O)CH₃ and X = I (3); R = CH₃ and X = OTf = SO₃CF₃ (4); R = C(O)CH₃ and X = OTf (5); R¹-Pyca = 2-R¹-pyridinecarbaldimine; and R′ = isopropyl (b), methoxyethyl (c), or isopropoxypropyl (d)), respectively, will be presented. The X-ray structure determination of the yellow crystals of [Ru(CH₃)(CO)₂(CH₃OCH₂CH ₂-PyCa)][OTf] (4c) has been carried out. Crystal data for 4c: monoclinic, space group P2₁/c with a = 8.5008(4) ?, b = 12.3281(8) ?, c = 18.412(1) ?, β = 101.118(6)°, V = 1893.4(2) ?³, Z = 4. The Ru(CO)₄(PMe₂Ph) (13) catalyzed CO insertion in the methyl-ruthenium bond of Ru(CH₃)X(CO)₂(iPr-DAB) (X = I (2a); X = OTf (4a); X = Cl (6a); DAB = 1,4-diaza-1,3-butadiene) and Ru(CH₃)X(CO)₂(iPr-Pyca) (X - I (2b); X = OTf (4b)) has been studied by use of labeled Ru(¹³CO)₄(PMe₂Ph) (13) and by reaction in the absence or presence of additional ligand PPh₃ and CO. For the neutral complexes 2a, 6a, and 2b the key intermediate for the CO insertion catalyzed by 13 is most probably of the type [Ru(CH₃)X(CO)(α-diimine)Ru(CO)₃(PMe ₂Ph)(μ-CO)₂] (X1), which is, however, not observed during the reaction. By ¹³CO labeling experiments it has clearly been demonstrated that binuclear species are involved in this reaction. Complex Ru(CO)₄(PMe₂Ph) (13) decomposes in CDCl₃ at 45°C under N₂ and under a CO atmosphere (1 and 8 atm) within 3 h to form Ru₂(CO)₄(PMe₂Ph)₂(μ-Cl) ₂ (15), which can further react with PPh₃ to Ru₂(CO)₄(PMe₂Ph)₂(PPh ₃)₂(μ-Cl)₂ (16). Suprisingly, 13 is stable under high CO pressure in the presence of 2a, 6a, and 2b in CDCl₃ at 45°C for several hours, most probably as a result of a faster reaction of Ru(CO)₄(PMe₂Ph) (13) or most likely [Ru(CO)₃(PMe₂Ph)] with 2a, 6a, or 2b than with CDCl₃, which prohibits decomposition.