Resumo

ARAUJO, Maria Helena; HITCHCOCK, Peter B.; NIXON, John F.  e  VARGAS, Maria D.. Synthesis and Structural Characterization of [Ir₄(m-CO)(CO)₇{m4-h^3-Ph₂PC(H)C(Ph)PCBu^t}(m-PPh_2)]: Alkyne-Phosphaalkyne Coupling and Formation of a Novel 2-phosphabutadienylphosphine Ligand. J. Braz. Chem. Soc. [online]. 1998, vol.9, n.6, pp. 563-570. ISSN 0103-5053.  http://dx.doi.org/10.1590/S0103-50531998000600008.

Reaction of [Ir₄(m-H)(CO)₉(Ph₂PCºCPh)(m-PPh₂)] 1 with PºCBu^t in CH₂Cl₂, at 35 °C, for 4 h yields the novel compound [Ir₄(m-CO)(CO)₇{m₄-h³-Ph₂PC(H)C(Ph)PCBu^t}(m-PPh₂)] 2, which contains the 2-phosphabutadienylphosphine chain. Compound 2 is also formed upon thermolysis of [Ir₄(CO)₁₀(Ph₂PCºCPh)(PPh₂H)] 3 in the presence of PºCBu^t in thf, at 40 °C, for 48 h. Small amounts of [Ir₄(m-CO)(CO)₇(m₃-h²-HCCPh)(m-PPh₂)₂] 4 are always obtained from both reactions, because of the competing rates of the transformations of 1 and 3 into 4 and of their reactions with PºCBu^t. Compound 2 was characterized by analytical and spectroscopic studies such as FAB ms, ¹H^{, 31}P, ¹³C, 2D ³¹P-¹H HETCOR, nOe difference and DEPT NMR experiments, which led to its formulation and established the coupling between the coordinated Ph₂PCºCPh and PºCBu^t and the migration of the hydride to the Ca of the Ph₂PCºCPh ligand. However, it was impossible to establish unambiguously if cleavage of the P-C_sp bond of the Ph₂PCºCPh ligand had occurred and the mode of interaction of the organophosphorus chain. An X-ray diffraction study of compound 2 established a butterfly arrangement of iridium atoms with the new ligand interacting with the metal framework via four s bonds and the PPh₂ phosphorus lone pair.

Palavras-chave : iridium cluster; phosphaalkyne; alkyne; coupling reaction.