Koshala Sarveswaran

Stepwise formation of an acetylide-bridged mixed-metal triangular dicobalt–iron cluster from [(OC)4Fe(PPh2CCPh)]

Abstract Reaction of [(OC) 4 Fe(η 1 -PPh 2 CCPh)] ( 1 ) with [Co 2 (CO) 8 ] at room temperature affords the heterotrimetallic complex [(OC) 4 Fe(μ-η 1 :η 2 -PPh 2 CCPh)Co 2 (CO) 6 ] ( 2 ), in which the alkynic moiety in 1 is bound to a Co 2 (CO) 6 unit. Both the mono- and di-substituted complexes, [(OC) 4 Fe(μ-η 1 :η 2 -PPh 2 CCPh)Co 2 (CO) 5 {P(OMe) 3 }] ( 3 ) and [(OC) 4 Fe(μ-η 1 :η 2 -PPh 2 CCPh)Co 2 (CO) 4 {P(OMe) 3 } 2 ] ( 4 ), are obtained on reaction of 2 with an excess of trimethylphosphite at elevated temperature; in both cases CO-substitution takes place solely at the cobalt centres. Thermolysis of 3 results in phosphorus-carbon bond cleavage and iron-cobalt bond formation to yield the mixed-metal 48-electron triangular cluster [FeCo 2 (CO) 6 {μ 3 -η 2 -(⊥)-CCPh}{P(OMe) 3 }(μ-PPh 2 )] ( 5 ), in which a phenylacetylide ligand perpendicularly-bridges one of the iron-cobalt edges and a phosphido group bridges the cobalt-cobalt edge. Substitution of a cobalt carbonyl ligand occurs on reaction of 5 with triphenylphosphine to give [FeCo 2 (CO) 5 {μ 3 -η 2 -(⊥)-CCPh}{P(OMe) 3 }(PPh 3 )(μ-PPh 2 )] ( 6 ). Single crystal X-ray diffraction studies have been performed on 2 and 6 .

Reactions of the mixed-metal alkyne-bridged complexes [(η5-C5H5)(OC)2M{μ-C2(CO2Me)2}Co(CO)3] (M=Mo or W) with Ph2PCCtBu

Abstract Reaction of the mixed-metal alkyne-bridged complexes [(η5-C5H5)(OC)2M{μ-C2(CO2Me)2}Co(CO)3] (M=Mo or W) with Ph2PCCtBu in refluxing toluene gives the complexes [(η5-C5H5)(OC)2M{μ-tBuCCC(CO2Me)C(CO2Me)PPh2}Co(CO)2], [(η5-C5H5)(OC)2M{μ-C2(CO2Me)2}Co(CO)2(Ph2PCCtBu)] (MMo or W) and [(η5-C5H5)(OC)W{μ-C(CO2Me)C(CO2Me)CCtBu}(μ-PPh2)Co(CO)2]. The structures of the two complexes, [(η5-C5H5)(OC)2Mo{μ-tBuCCC(CO2Me)C(CO2Me)PPh2}Co(CO)2] and [(η5-C5H5)(OC)W{μ-C(CO2Me)C(CO2Me)CCtBu}(μ-PPh2)Co(CO)2], have been determined by X-ray analysis. Possible reaction pathways for the formation of the new complexes are proposed and discussed.

Formation of carbene and cyclopentadienyl ligands from phenylacetylene via oligomerisation and C C bond scission at a mixed-metal W-Co centre

The 1,2,4-triphenylcyclopentadienyl ligand and the CHR carbene ligand, bound respectively to the Co and W atoms in [(η5-C5H5)W{μ-CBut CC(CO2Me)C(CO2Me)CH}(μ-PPh 2)Co(η5-C5Ph3H2 )], are derived from the oligomerisation and cleavage of three molecules of phenylacetylene in the reaction of [(OC)(η5-C5H5)W{μ-C(CO2 Me)CC(CC- But)(OMe)O}(μ-PPh2)Co(CO)2] with this acetylene.