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Reaction of RhMe3(triphos) (triphos = MeC(CH2PPh2)3) with CO generates acetone and RhMe(CO)(triphos), which reacts with further CO to give Rh[C(O)Me](CO)(triphos). The structure of RhMe(CO)(triphos) shows one strained P-Rh-P bond angle between equatorial ligands (90.80 (5)°) in a trigonal bipyramid, together with intramolecular steric effects that cause a small equatorial CO-Rh-axial(CH3) C/C angle of 79.09 (25)°. The acetyl and methyl complexes react with H2 at 25°C to produce acetaldehyde and methane, respectively, together with RhH(CO)(triphos). Reaction of CO with RhH3(triphos) is even faster than with RhMe3(triphos) to give H2 and RhH(CO)(triphos), together with a CO hydrogenation product. These results show that these clean stoichiometric conversions, as well as a variety of isotopic exchange reactions of the Rh(I) and Rh(III) compounds with D2 and 13CO, occur by preequilibrium dissociation of one arm of the triphos ligand at 25°C. One such species, Rh[C(O)Me](CO)2(η2-triphos), is directly detectable and reveals the mechanism of exchange of Rh[C(O)Me](13CO)(triphos) with 12CO. The coordination of CO to Rh(H)3(η2-triphos) is proposed to generate a dihydrogen complex, thus accounting for the CO-induced elimination of H2. As suggested by these individual reactions, RhH(CO)(triphos) is a catalyst for olefin hydroformylation. The high n:iso selectivity mimics that of RhH(CO)(PPh3)3 in the presence of a large amount of added PPh3, a beneficial consequence of the chelate effect.

Treatment of the complex [Rh(CO)2(triphos)]PF6 (triphos = MeC(CH2PPh2)3) with the ligands L (L = PMe3, PMe2Ph, PEt3, P(n-Bu)3, P(OMe)3, t-BuNC) resulted in the formation of complexes of the type [Rh(CO)L(triphos)]PF6. The analogous complexes of PPh3, ethylene, and propylene could not be prepared in this way but were synthesized by displacing molecular hydrogen from the complex [RhH2(CO)(trip-hos)]PF6, prepared by the photochemical oxidative addition of H2 to [Rh(CO)2(triphos)]PF6. The σ-bonded organorhodium(I) complexes RhR(CO)(triphos) (R = Me, Ph) were prepared by treating RhCl(CO)(triphos) with the appropriate alkyllithium reagent, and these compounds in turn were found to react readily with CO to form the acyl complexes Rh(RCO)(CO)(triphos). Addition of anhydrous HCl to the complex RhCl(CO)(triphos) resulted in the formation of a mixture of RhHCl2(CO)(triphos) and RhCl3(triphos), while addition of excess chlorine, bromine, or iodine to [Rh(CO)2(triphos)]PF6 resulted in the formation of the rhodium(III) complexes [RhX2(triphos)]PF6 (X = Cl, Br, I). These reacted in turn with methyllithium to form RhMe3(triphos), and with a variety of neutral ligands L to form the series [RhX2L(triphos)]PF6.

The syntheses of (8, triphos=CH3C(CH2PPh2)3) and the related compound (triphos-I=EtC(CH2PPh2)3) are described, and the X-ray crystal structure of the latter is reported.The crystals are monoclinic space group P21/a, a 15.985(6), b 19.683(7), c 11.900(4) Angstroem, β 103,73(6) degree, Z=4.The structure was solved by the heavy atom method and refined by full-matrix leastsquares to the conventional R factor value of 0.057 for 2649 observed reflections.The metal atom is octahedrally coordinated by three phophorus atoms and by three hydrogen atoms, each trans to one phosphorus.Complex 8 has been shown to react with CO to give (2).Compound 2 reacts with CH2=CHCO2Me to give only the branched insertion product .The complex has been re-investigated and was obtained in a single isomeric form which has been assigned a five-coordinate structure.The five-coordinate compounds (X=Br and I) are also described.