The five-coordinate complex OsHCl(CO)(PiPr3)2 (1) reacts with KOH in methanol to give the hydroxo derivative OsH(OH)(CO)(PiPr3)2 (2). Treatment of 2 with 1 equiv of dimethyl acetylenedicarboxylate which is the result of the trans addition of the OH bond of 2 to the carbon−carbon triple bond of the alkyne. The structure of 3 was determined by an X-ray investigation. The geometry of the complex can be rationalized as a distorted octahedron with the two phosphorus atoms of the triisopropylphosphine ligands occupying apical positions. The equatorial plane is formed by the hydride, the carbonyl group, and the κ2-O-donor ligand, which has a bite angle of 84.17(7)°. Complex 2 also reacts with methyl acrylate, methyl vinyl ketone, and allyl alcohol. Reaction with methyl acrylate leads to OsH(OH)(CO)(η2-CH2CHCO2CH3)(PiPr3)2 (4). The structure of 4 was also determined by an X-ray investigation. The coordination geometry around the osmium atom can be rationalized as derived from a highly distorted octahedron with the phosphorus atoms of the triisopropylphosphine ligands occupying pseudo-trans positions (P−Os−P = 144.29(3)°) at opposite sides of an ideal coordination plane defined by the carbonyl ligand, disposed trans to the hydroxo group and the hydrido ligand disposed trans to the olefin. In solution, complex 4 releases the olefin to regenerate 2 and methyl acrylate. The thermodynamic magnitudes involved in the equilibrium were determined in toluene-d 8 by 31P{1H} NMR spectroscopy. The values obtained were ΔH° = 17.0 ± 0.5 kcal mol-1 and ΔS° = 54.0 ± 1.2 cal K-1 mol-1. In the presence of methyl vinyl ketone complex 2 and water whereas in the presence of allyl alcohol the loss of water affords OsH(CH2CH3)(CO)2(PiPr3)2 (6). Under a carbon dioxide atmosphere complex 2 gives the bicarbonato derivative OsH(κ2-O2COH)(CO)(PiPr3)2 (7), which, by carbonylation, affords OsH{κ1-OC(O)OH}(CO)2(PiPr3)2 (8). Complex 2 also reacts with phenyl isocyanate to give the carbamato derivative OsH(κ2-O2CNHPh)(CO)(PiPr3)2 (9). The reactions of 2 with Lewis bases that are not bulky such as CO, P(OMe)3, and tBuNC afford the six-coordinate hydrido−hydroxo compounds OsH(OH)(CO)L(PiPr3)2 (L = CO (10), P(OMe)3 (11), tBuNC (12)).

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The synthesis and characterization of optically active phosphinooxazoline complexes (R Rh and S Rh)-[(η5-C5Me5)RhCl(PN)][A] (PN = (4S)-2-(2-diphenylphosphino)phenyl)-4-isopropyl-1,3-oxazoline (PN(iPr)), A = SbF6 (1a,1a‘), A = BF4 (1b,1b‘); PN = (4S)-2-(2-diphenylphosphino)phenyl)-4-methyl-1,3-oxazoline (PN(Me)), A = SbF6 (2a,2a‘), A = BF4 (2b,2b‘); PN = (3aS,8aR)-2-(2-diphenylphosphino)phenyl)-3a,8a-dihydroindane[1,2-d]oxazole] (PN(Ind)), A = SbF6 (3a,3a‘)), (S Rh and R Rh)-[(η5-C5Me5)RhI(PN(Me))][SbF6] (4a,4a‘) and (R Ir and S Ir)-[(η5-C5Me5)IrCl(PN)][A] (PN = PN(iPr), A = SbF6 (5a,5a‘), A = BF4 (5b,5b‘); PN = PN(Me), A = SbF6 (6a,6a‘), A = BF4 (6b,6b‘); PN = PN(Ind), A = SbF6 (7a,7a‘)), and the solvate complexes (S Rh and R Rh)-[(η5-C5Me5)Rh(PN)S][SbF6]2 (PN = PN(iPr) (8a,8a‘), PN(Me) (9a,9a‘), PN(Ind) (10a,10a‘); S = H2O, Me2CO) and (S Ir and R Ir)-[(η5-C5Me5)Ir(PN)S][A]2 (PN = PN(iPr), A = SbF6 (11a‘), A = BF4 (11b‘); PN = PN(Me), A = SbF6 (12a‘), A = BF4 (12b‘); PN = PN(Ind), A = SbF6 (13a,13a‘)) are reported. The crystal structures of the (R Rh)-1a, (S Rh)-1a‘, (R Rh)-2a, (S Rh)-2a‘, (R Rh)-2b, (R Rh)-3a, (S Rh)-4a, (R Ir)-5b, (R Ir)-6a, (S Ir)-6a‘, and (R Rh)-9a‘ epimers were determined by X-ray diffractometric methods. All the complexes show the chiral metal center in a pseudo-octahedral environment, being bonded to an η5-C5Me5 ring, to the nitrogen and phosphorus atoms of the phosphinooxazoline ligand in a chelate fashion, and to a terminal chlorine (1a, 1a‘, 2a, 2a‘, 2b, 3a, 5b, 6a, 6a‘) or iodine (4a), or to the oxygen of an acetone molecule (9a‘). Two conformations of the M−P−C−C−C−N metallacycle have been found in the crystals:  the 5S4 (unprimed complexes and 2a‘) and the 1S2 (primed complexes and 2a) screw-boat conformations. In solution, complexes 2, 4, 6, 8a‘, 9, 10, 12, and 13 exist as a mixture of conformers, most probably arising from the interconversion of the 1S2 and 5S4 conformations. This process was studied by 1H and 31P NMR spectroscopy. Dichloromethane solutions of the solvate complexes [(η5-C5Me5)M(PN)S][SbF6]2 are active catalysts for the Diels−Alder reaction between methacrolein and cyclopentadiene. The reaction occurs rapidly at room temperature with good exo:endo ratio (from 81:19 to 95:5) and moderate enantioselectivity (up to 67% (Rh compounds), 65% (Ir compounds)).

The five-coordinate complexes MHCl(CO)(PiPr3)2 (M = Os (1), Ru (2)) react with NaSH to give the unsaturated hydrido−metallothiol derivatives MH(SH)(CO)(PiPr3)2 (M = Os (3), Ru (4)). Complexes 3 and 4 react with CO to afford the cis-dicarbonyl compounds MH(SH)(CO)2(PiPr3)2 (M = Os (5), Ru (6)). Similarly, the reaction of 3 with P(OMe)3 leads to OsH(SH)(CO){P(OMe)3}(PiPr3)2 (7). Treatment of 3 with 1 equiv of acetylenedicarboxylic methyl ester which is the result of the trans addition of the S−H bond of 3 to the carbon−carbon triple bond of the alkyne. The structure of 8 was determined by X-ray investigation. The geometry of the complex can be rationalized as a distorted octahedron with the two phosphorus atoms of the triisopropylphosphine ligands occupying apical positions. The equatorial plane is formed by the bidentate ligand, which acts with a bite angle of 89.49(12)°, the hydrido ligand trans-disposed to the oxygen atom, and the carbonyl group trans-disposed to the sulfur atom. Acetylenedicarboxylic methyl ester also reacts with 4 by insertion of the carbon−carbon triple bond into the S−H bond. However, in the resulting monothio-β-diketonato the hydrido ligand lies trans to the sulfur atom. In solution, complex 9 isomerizes into 10, containing the hydrido ligand trans-disposed to the oxygen atom of the chelate group. The stereochemistry of 10 was corroborated by X-ray investigation. The geometry of 10 is the same as that of 8, and the structural parameters of both molecules are statistically identical. Phenylacetylene and methylpropiolate, in contrast to acetylenedicarboxylic methyl ester, react with 3 and 4 by insertion of the carbon−carbon triple bonds into the M−H bonds to give the unsaturated alkenyl−metallothiol complexes M{(E)-CHCHPh}(SH)(CO)(PiPr3)2 (M = Os (11), Ru (12)) and Ru{(E)-CHCHCO2CH3}(SH)(CO)(PiPr3)2 (13).