Reactions of Aryl Isocyanates with Hydridotriosmium Carbonyl Cluster Compounds

The reactions of aryl isocyanates with the cluster complexes H2Os3(CO)9L [I, L = CO; II, L = P(CH3)2C6H5] are described. The major products of the reaction of I with aryl isocyanates are complexes containing N-arylformamido ligands formed by the transfer of one hydride ligand to the carbon atom of the isocyanate molecule. An X-ray crystallographic analysis of the product (µ-H)(µ-p-CH3C6H4NCHO)Os3(CO)10 (III) was performed: space group Pi, a = 7.925 (2) Å, b = 11.705 (3) Å, c = 13.928 (4) Å, a = 66.71 (2)°, β = 80.17 (2)°, γ = 79.18 (2)°, Z = 2, Paki = 2.83 g/cm1 23. For 3902 reflections, R = 0.052 and Rw = 0.062. III contains an TV-p-tolylformamido ligand which is coordinated by its nitrogen and oxygen atoms across one edge of a triangular cluster of three osmium atoms. Reaction of III with dimethylphenylphosphine readily gives the monosubstitution product (µ-H)(µ-p-CH3C6H4NCHO)Os3(CO)9[P(CH3)2C6H5] (V). An X-ray crystallographic analysis of V was performed: space group PI, a = 10.690 (1) Å, b = 13.034 (2) Å, c = 13.200 (4) Å, a = 109.78 (2)°, β = 93.05 (2)°, y = 110.25 (2)°, Z = 2, = 2.28 g/cm3. For 3985 reflections, R = 0.047 and J?w = 0.061. V is similar to III except that it contains a dimethylphenylphosphine ligand coordinated in an equatorial position on the osmium atom coordinated to the oxygen atom of the bridging A-p-tolylformamido ligand. The major product of the reaction of II with p-tolyl isocyanate was an isomer of V which was characterized by spectroscopic and X-ray crystallographic methods as (µ-H)(µ-p-CH,C6H4NHCO)Os3(CO)9[P(CH3)2C6H5] (VI): space group P21/c, a = 12.210 (2) Å, b = 14.337 (4) Å, c = 17.739 (4) Å, β = 104.49 (2)°. For reflections, R = 0.034 and Rw = 0.032. VI contains an N-hydrido-N-p-tolylcarboxamido ligand which is coordinated by its carbon and oxygen atoms across an edge of a triangular cluster of osmium atoms. This product was evidently formed by transfer of a hydrogen atom from the cluster to the nitrogen atom of the isocyanate. A minor product (q-H)(µ-A-p-CH3C6H4NHCO)Os3(CO)10 (VII), which is similar to VI, was also isolated from the reaction of I with p-tolyl isocyanate. It was shown that III and VII cannot be interconverted under the reaction conditions. They are, thus, presumed to be formed by independent competing reactions. The changes in hydrogen transfer obtained when a carbonyl ligand is replaced with a dimethylphenylphosphine ligand are discussed.