Regiospecificity in reactions of alkynes and phosphines with the phosphido-bridged iron-cobalt complex [(OC)4Fe(μ-PPh2)Co(CO)3]

Jason D. King, Martin J. Mays, Chi Yu Mo, Paul R. Raithby, Moira A. Rennie, Gregory A. Solan, Trushar Adatia, Gráinne Conole

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Abstract

The iron-cobalt phosphido-bridged complex [(OC)4Fe(μ-PPh2)Co(CO)3] (1) can be prepared conveniently and in good yield from the reaction of [Co2(μ-PPh2)2(CO)6] with [Fe(CO)5]. A study of the reactivity of 1 towards symmetrical and unsymmetrical alkynes, R1CCR2 (R1=R2=CO2Me, Ph; R1=H, R2=Ph), has been undertaken. In all cases, five-membered ferracycle-containing products of the type [(OC)3Fe{μ-PPh2C(O)CR1CR 2}Co(CO)3] (R1=R2=CO2Me (2a), Ph (2c); R1=H, R2=Ph (2b)), are initially obtained in which a molecule of CO and a molecule of R1CCR2 have been inserted regiospecifically into a Co-P bond in 1. Decarbonylation of 2a occurs during its preparation or in low yield on its thermolysis to give the four-membered ferracyclic species [(OC)3Fe{μ-PPh2C(CO2Me)C(CO 2Me)}Co(CO)3] (3a). Similar thermolysis of 2b results not only in the related decarbonylation product [(OC)3Fe(μ-PPh2CHCPh)Co(CO)3] (3b), but additionally in three other products all in low yield, namely the regioisomer of 3b, [(OC)3Fe(μ-PPh2CPhCH)Co(CO)3] (4b), the aldehyde-substituted complex [(OC)3Fe{μ-PPh2C(CHO)CPh}Co(CO)3] (5b) and the five-membered ferracycle-containing species [(OC)3Fe{μ-PPh2CHCPhC(O)}Co(CO)3] (6b). Treatment of 2a and 2b with PPhMe2 and P(OMe)3 results in substitution of an iron-bound carbonyl group to give, respectively, [(PhMe2P)(OC)2Fe{μ-PPh2C(O)C(CO 2Me)C(CO2Me)}(μ-CO)Co(CO)2] (7a) and [{(MeO)3P}(OC)2Fe{μ-PPh 2C(O)CHCPh}(μ-CO)Co(CO)2] (7b) in high yield. In contrast, substitution of a cobalt-bound carbonyl is achieved on reaction of 3a with PPhMe2 or PPh2H to give [(OC)3Fe{μ-PPh2C(CO2Me)C(CO 2Me)}Co(CO)2(L)] (L=PPhMe2 (8a), PPh2H (9a)). Thermolysis of the secondary phosphine-substituted complex 9a results in phosphorus-hydrogen bond cleavage to give [(OC)3Fe{μ-PPh2C(CO2Me)CH(CO 2Me)}(μ-PPh2)Co(CO)2] (10a). Single-crystal X-ray diffraction studies have been performed on complexes 7b, 8a and 10a.

Original languageEnglish
Pages (from-to)271-283
Number of pages13
JournalJournal of Organometallic Chemistry
Volume601
Issue number2
DOIs
Publication statusPublished - 28 Apr 2000

Keywords

  • Alkyne
  • Cobalt
  • Dinuclear
  • Iron
  • Phosphido
  • Phosphine

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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