TY - JOUR
T1 - Alkyne-phosphinoalkyne coupling reactions on mixed-metal tungsten-cobalt centres; P-C(alkyne) bond cleavage versus P-C(alkyne) bond preservation
AU - Davies, J. E.
AU - Mays, M. J.
AU - Raithby, P. R.
AU - Sarveswaran, K.
AU - Solan, G. A.
PY - 2001
Y1 - 2001
N2 - Reactions of the alkyne-bridged tungsten-cobalt complexes [(η5-C5H5)(OC)2W(μ- R1CCR2)Co(CO)3](R1 = R2 = CO2Me 1a; R1 = H, R2 = But 1b) with Ph2PC≡CPh in refluxing toluene result in two different reaction pathways. On reaction with 1a three products are isolated namely, [(η5-C5H5)(OC)2W{μ- C2(CO2Me)2}Co(CO)3- (PPh2C≡CPh)] 2, the result of substitution of a cobalt carbonyl ligand by a phosphorus-bound molecule of Ph2PC≡CPh, [(η5-C5H5)(OC)2W{μ- PhCCC(CO2Me)=C(CO2Me)PPh2} Co(CO)2] 3 and [(η5-C5H5)(OC)W- {μ-C(CO2Me)=C(C=CPh)C(OMe)O}(μ-PPh2) Co(CO)2] 4, in which phosphorus-carbon(alkyne) bond cleavage of the phosphinoalkyne has ocurred along with phosphorus-carbon bond formation (3) and/or carbon-carbon bond formation (3 and 4). In contrast, reaction of 1b (with Ph2PC≡CPh affords two products, [(η5-C5H5)(OC)W-{μ-CBut CHCPhC(PPh2)}Co(CO)2] 5 and [(η5-C5H5)(OC)2W{μ- CButCHC(PPh2)CPh}Co(CO)2] 6, in which the bridging alkyne has coupled with an intact molecule of the phosphinoalkyne Ph2PCα≡CβPh at either its β- or α-carbon atoms, respectively. However, on reaction of 1b with the tert-butyl-substituted phosphinoalkyne, Ph2PC≡CBut, regiospecific coupling and oxidation of the phosphino moiety occur to give [(η5-C5H5)(OC)W-{μ-CBut= CHCBut=C(PPh2O)}Co(CO)2] 8, as the sole product. The reactivity of 6 towards diiron nonacarbonyl has been explored and found to afford the trimetallic complex [(η5-C5H5)(OC)2W{μ- CButCHC(PPh2Fe(CO)4)-CPh}Co(CO)2] 7 in good yield. Single crystal X-ray diffraction studies have been performed on 4, 6, 7 and 8 and possible reaction pathways for the formation of the new complexes are proposed and discussed.
AB - Reactions of the alkyne-bridged tungsten-cobalt complexes [(η5-C5H5)(OC)2W(μ- R1CCR2)Co(CO)3](R1 = R2 = CO2Me 1a; R1 = H, R2 = But 1b) with Ph2PC≡CPh in refluxing toluene result in two different reaction pathways. On reaction with 1a three products are isolated namely, [(η5-C5H5)(OC)2W{μ- C2(CO2Me)2}Co(CO)3- (PPh2C≡CPh)] 2, the result of substitution of a cobalt carbonyl ligand by a phosphorus-bound molecule of Ph2PC≡CPh, [(η5-C5H5)(OC)2W{μ- PhCCC(CO2Me)=C(CO2Me)PPh2} Co(CO)2] 3 and [(η5-C5H5)(OC)W- {μ-C(CO2Me)=C(C=CPh)C(OMe)O}(μ-PPh2) Co(CO)2] 4, in which phosphorus-carbon(alkyne) bond cleavage of the phosphinoalkyne has ocurred along with phosphorus-carbon bond formation (3) and/or carbon-carbon bond formation (3 and 4). In contrast, reaction of 1b (with Ph2PC≡CPh affords two products, [(η5-C5H5)(OC)W-{μ-CBut CHCPhC(PPh2)}Co(CO)2] 5 and [(η5-C5H5)(OC)2W{μ- CButCHC(PPh2)CPh}Co(CO)2] 6, in which the bridging alkyne has coupled with an intact molecule of the phosphinoalkyne Ph2PCα≡CβPh at either its β- or α-carbon atoms, respectively. However, on reaction of 1b with the tert-butyl-substituted phosphinoalkyne, Ph2PC≡CBut, regiospecific coupling and oxidation of the phosphino moiety occur to give [(η5-C5H5)(OC)W-{μ-CBut= CHCBut=C(PPh2O)}Co(CO)2] 8, as the sole product. The reactivity of 6 towards diiron nonacarbonyl has been explored and found to afford the trimetallic complex [(η5-C5H5)(OC)2W{μ- CButCHC(PPh2Fe(CO)4)-CPh}Co(CO)2] 7 in good yield. Single crystal X-ray diffraction studies have been performed on 4, 6, 7 and 8 and possible reaction pathways for the formation of the new complexes are proposed and discussed.
UR - http://www.scopus.com/inward/record.url?scp=0034743860&partnerID=8YFLogxK
U2 - 10.1039/b009396n
DO - 10.1039/b009396n
M3 - Article
AN - SCOPUS:0034743860
SN - 1470-479X
SP - 1269
EP - 1277
JO - Journal of the Chemical Society, Dalton Transactions
JF - Journal of the Chemical Society, Dalton Transactions
IS - 8
ER -