Aqueous Organometallics with Pressurized Gases

Several olefin complexes of the Ru(II) aquo ion [45-47] and of the other Ru complexes [48, 49] have been synthesized and characterized in the ring-opening metathesis polymerization (ROMP cf. Section 6.13) or olefm isomerization reactions. The simplest olefin complex of Ru was also observed, isolated, and characterized under ethylene pressure [50]. A H2170-enriched aqueous solution of [Ru(HzO)6]2+ was pressurized with ethylene and mixed. The reaction (Eq. 9) was followed by 3H, 13C, and 170 NMR spectroscopy. 

After 6 h the 170 NMR spectra showed the complete loss of resonance at —192 ppm due to the hexaaqua Ru(II). At the same time new signals appeared corresponding to [ Ru(CH2=CH2)(H20) (H20) ]2+. After 18 h of mixing the NMR spectra show the substitution of a second water molecule (Eq. 10). 

Aqueous solutions of ruthenium clusters [Ru3(C0)12 (P m-C6H4S03Na 3)J, where x = 1, 2 or 3 and [H4Ru4(C0)n(P m-C6H4S03Na 3)], as catalyst precursors, were used in the hydrogenation of non-activated alkenes [61], Each cluster displays catalytic activity under moderate conditions (60 bar H2 pressure, T = 333 K) with turnovers up to 500. 

Ligand substitution on M(CO)5L complexes, where M = Mo or W and L = P(m-C6H4S03Na)3 or PPh3, were studied under 3.4 MPa CO pressure in water and a water-THF (1 1) mixture [58], The reactions (Eq. 11) were followed in situ by infrared spectroscopy in a reactor cell [59] between 388 and 423 K. 

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