Acetylene and phenylacetylene reacts with carbonylchloro[4-methyl-6-((R-imino)methyl)phenolato-C,O]bis(triphenylphosphine)ruthenium(II), Ru(RL 1 )(PPh 3 ) 2 (CO)Cl (3), affording the inserted product carbonylchloro[2-vinyl-4-methyl-6-((R-imino)methyl)phenolato-C,O]bis-(triphenylphosphine)ruthenium(II), Ru(RL 2 ,X)(PPh 3 ) 2 (CO)Cl ( 4), in virtually quantitative yield. The X-ray structures of 4b (R ) X ) Ph) and 4g (R ) Et, X ) H) have revealed the presence of distorted-octahedral RuC 2 P 2 ClO coordination spheres. In the conversion 3 f 4, the Ru(C,O) chelate ring expands from four-membered to six-membered. The insertion of phenylacetylene is regiospecific, and a reaction model implicating initial Ru-O cleavage and steric control is proposed. The Ru-O bond in 4 is significantly shorter (by ∼0.14 Å) and stronger than that in 3. This is reflected in the lowering of the ruthenium(III)ruthenium(II) reduction potential by ∼200 mV. The uncoordinated Schiff base moiety in 4 is present in the hydrogen-bonded iminium-phenolato zwitterionic form, as revealed by the N‚‚‚O distance as well as by IR and NMR data.

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The insertion of HOCH2C⋮CH (ha) into the Ru−C bond of RuII(RL1)(PPh3)2(CO)Cl, 1, has afforded RuII(RL3)(PPh3)2(CO)Cl, 3, which has been structurally characterized. Insertion rates in CH2Cl2−MeOH for ha as well as for PhC⋮CH (pa), which inserts similarly into 1 affording RuII(RL2)(PPh3)2(CO)Cl, 2, are proportional to the product of the concentrations of alkyne and methanol. The insertion rate of ha is nearly 5 times faster than that of pa, and for a given alkyne the rate increases as R becomes more electron-withdrawing (OMe < Me < Cl). A reaction model implicating the adduct 1·MeOH, which binds and activates the alkyne via displacement of MeOH, is proposed.

The Schiff mono bases of 2,6-diformyl-4-methylphenol, 1, react with RhCl 3 ‚3H 2 O and PPh 3 in ethanol, affording dichloro[4-methyl-6-((arylimino)methyl)phenolato-C 1 ,O]bis(triphenylphosphine)rhodium(III), Rh(XL sb )(PPh 3 ) 2 Cl 2 (5; X ) H, Me, OMe, Cl). Organometallics of the type (carboxylato)[4-methyl-6-formylphenolato-C 1 ,O]bis(triphenylphosphine)rhodium(III), Rh(L al )(PPh 3 ) 2 (RCO 2 ) (6; R ) H, Me, Et, Ph), have been synthesized by oxidative addition of 1 to RhCl(PPh 3 ) 3 in the presence of dilute RCO 2 H in ethanol. Replacement of RCO 2 H by dilute HNO 3 has afforded the nitrate analogue Rh(L al )(PPh 3 ) 2 (NO 3 ) (7). Species of type 5 are susceptible to aldiminium f aldehyde hydrolysis in a dichloromethane-acetone-water mixture with concomitant chloride dissociation, furnishing Rh(L al )(PPh 3 ) 2 Cl (8a), from which the N-bonded nitrite Rh(L al )(PPh 3 ) 2 (NO 2 ) (8b) has been generated metathetically. The four types of species 5-8 are interconvertible, and a possible reaction pathway involving pentacoordinate intermediates is proposed. The X-ray structures of Rh(MeL sb )(PPh 3 ) 2 Cl 2 (5b; bis(dichloromethane) adduct), Rh(L al )(PPh 3 ) 2 (MeCO 2 ) (6b), Rh(L al )(PPh 3 ) 2 (NO 3 ) (7), and Rh-(L al )(PPh 3 ) 2 (NO 2 ) (8b) have been determined. Among these, 5b, 6b, and 7 are pseudooctahedralsthe bonds trans to the acyl function being longer by 0.2-0.4 Å compared to those trans to phenolato oxygen. Complex 8b is square pyramidal, there being no ligand trans to the acyl function. In 5b iminium-phenolato (N‚‚‚O, 2.66(1) Å) and in the remaining species aldehyde-phenolato (C‚‚‚O, 2.86(1) Å) hydrogen bonding is present. Internal charge balance is crucial for the stability of the present organometallics.