Synthesis and Reactivity of the Unusual Five-Coordinate Hydrido−Hydroxo Complex OsH(OH)(CO)(PiPr₃)₂

Citations Over TimeTop 10% of 1997 papers

Abstract

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 OH 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-CH2CHCO2CH3)(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-d8 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)).

Related Papers

• → Pd(0)-catalyzed selective [2 + 2 + 2] cycloaddition of dimethyl nona-2,7-diyne-1,9-dioate derivatives with dimethyl acetylenedicarboxylate(1999)43 cited
• → Influence of solvent and substituents on the reaction of N-alkylthioacetamides with dimethyl acetylenedicarboxylate: synthesis of functionalized thiophenes containing an exocyclic double bond(2013)16 cited
• → Further study on 1,3‐dialkylaminouracil with dimethyl acetylenedicarboxylate(1987)11 cited
• → Cycloadditions of indolizine-3-carbonitriles with dimethyl acetylenedicarboxylate: formation of [2.2.3]cyclazines and 1 : 2 adducts(1992)13 cited
• → Unexpected [2 + 2] cycloaddition between the PO group of P-(2,4,6-triisopropylphenyl) P-heterocycles and dimethyl acetylenedicarboxylate(1999)10 cited