The formation and transformation of metallacycles constaining phosphorus or sulfur on molybdenum- or tungsten-cobalt mixed-metal backbones

摘要

The new heterobimetallic complexes of general formula [{(R′S)Ph_2P}(OC)_2Co{μ-C_2(CO_2Me)_2}M(#eta#~5-L)(CO)_2] 1[L = C_5H_5 or C_5Me_5; M = Mo or W; R′= hydrocarbyl]undergo thermally induced phosphorus-sulfur bond breaking reactions. By variation of the nature of the R′substituent, the cyclopentadienyl group or the Group 6 metal centre in 1, bimetallic complexes incorporating bridging four-membered metallacycles of the type M-P-C=C or M-S-C=C (where M = Co, Mo or W), are accessible. While [{PhS)Ph_2P}(OC)_2Co{μ-C_2(CO_2 Me)_2}Mo(#eta~5-C_5H_5)(CO)_2] 1a gives as the sole product the phosphorus-containing molybdenacyclic species [(OC)(#eta#~5-C_5H_5)Mo{μ-PPh_2C(CO_2Me)-C(CO_2Me}(μ-SPh)Co(CO)_2] 2a, the corresponding reaction of [{(R250L銼)Ph_2P}(OC)_2Co{μ-C_2(CO_2Me)_2}Mo(#eta#~5-C_5H_5)-(CO)_2](R′= Bu~(II) 1b; Bu~t 1c), results in the formation of both [(OC)(#eta#~5-C_5H_5)Mo{μ-PPh_2C(CO_2Me)C(CO_2Me)}-(μ-SR′)Co(CO)_2](R′= Bu~n 2b; Bu~t 2c) and [(OC)_2Co{μ-SR′C(CO_2Me)C(CO_2Me}(μ-PPh_2)Mo(#eta#~5-C_5H_5)(CO)](R′= Bu~n 3b; Bu~t 3c). The latter sulfur-containing cobaltacyclic species (3c) has been shown to isomerise to the phosphorus-containing molybdenacylic species 2c on further heating. Conversely, employment of the pentamethylcyclopentadienyl complex [{(PhS)Ph_2P}(OC)_2Co{μ-C_2(CO_2Me)_2}Mo(#eta#~5-C_5Me_5)(CO)_2] 1b gives three species, [(OC)(#eta#~5-C_5Me_5)Mo{μ-PPh_2C(CO_2Me)C(CO_2Me)}(μ-SPh)Co(Co)_2] 2d and [(OC)_2Co{μ-SPhC(CO_2Me)C(CO_2Me)C(CO_2Me)}-(μ-PPh_2)Mo(#eta#~5-C_5Me_5)(CO)] 3d, which are, respectively, analogues of 2a-3c and 3b, 3c, and in addition the phosphorus-containing cobaltacyclic species [(OC)_2Co{μ-PPh_2C(CO_2Me)C(CO_2Me)}(μ-SPh)Mo(#eta#~5-C_5Me_5)(CO)] 4d. Thermolysis of [{(Bu~nS)Ph_2P}(OC)_2Co{μ-C_2(CO_2Me)_2}W(#eta#~5-C_5H_5)(CO)_2] 1e, in which a tungsten centre has been introduced in place of the molybdenum in 1b, affords only sulfur-containing metallacyclic products, which incorporate either the cobalt centre as in [(OC)_2Co{μ-SBu~nC(CO_2Me)C(CO_2Me)}(μ-PPh_2)W(#eta#~5-C_5H_5)(CO)] 3e or the tungsten centre as in [(OC)(#eta#~5-C_5H_5)W{μ-SBu~nC(CO_2Me)C(CO_2Me)}(μ-PPh_2)CO(CO)_2] 5e. The 'flyover' complex [(OC)(#eta#~5-C_5H_5)W{μ-C(CO_2Me)CHC(OMe)O}(μ-SPh)Co(CO){PPh_2(SPh)}] 6 was the only product obtained from the reaction of [(OC)(#eta#~5-C_5H_5)W{μ-C_2(CO_2Me)_2}W(#eta#~5-C_5H_5)(CO)_2] with Ph_2P(SPh). Single crystal X-ray diffraction studies have been performed on complexes 1d, 2b, 3c′[the P(OMe)_3-substituted derivative of 3c], 5e and 6.