Studies of the Mechanism of Carbon Oxygen Bond Formation in a Polyoxoanion-Supported Oxairidacyclobutane Complex
The goal of this research has been to understand the C-O bond formation mechanism of the oxametallacyclobutane complex, ((C$\sb8$H$\sb $O)Ir($\kappa\sp3$O-P$\sb3$O$\sb9$)) ((n-C$\sb4$H$\sb9)\sb4$N) $\sb2$ (2). The reaction of ((C$\sb8$H$\sb $)Ir($\kappa\sp3$O-P$\sb3$O$\sb9$)) ((n-C$\sb4$H$\sb9)\sb4$N) $\sb2$ (1) with cyanoolefins was carried out in order to synthesize bidentate (P$\sb3$O$\sb9)\sp{3-}$ complexes, ((C$\sb8$H$\sb $)Ir($\kappa\sp2$O-P$\sb3$O$\sb9$)(cyanoolefin)) ((n-$\rm C\sb4H\sb9)\sb4N\rbrack\sb{2}$. The $\sp{31}$P chemical shifts observed for these complexes were then used to assign the $\sp{31}$P NMR shifts observed for an intermediate in the formation of 2 by O$\sb2$ oxidation of 1. The reaction of ((C$\sb8$H$\sb $)Ir($\kappa\sp3$O-P$\sb3$O$\sb9$)) ((n-C$\sb4$H$\sb9)\sb4$N) $\sb2$ with O$\sb2$ has been further investigated to study the conversion of the previously observed intermediate to complex 2. Compound ((C$\sb8$H$\sb $)Ir($\kappa\sp3$O-P$\sb3$O$\sb9$)) ((n-C$\sb4$H$\sb9)\sb4$N) $\sb2$ reacted with allyl iodide to form a $\sigma$-allyl complex, ((C$\sb8$H$\sb $)Ir($\kappa\sp3$O-P$\sb3$O$\sb9)(\eta\sp1$-C$\sb3$H$\sb5$)) ((n-C$\sb4$H$\sb9)\sb4$N). This reaction was performed to examine the equilibrium between tridentate trimetaphosphate coordination and bidentate coordination, when both modes are allowed by the 18-electron rule. Finally, a unique reversible conversion of the oxametallacyclobutane complex 2 to the aquo olefin complex ((C$\sb8$H$\sb $)Ir(OH$\sb2)(\kappa\sp3$O-P$\sb3$O$\sb9$)) (3) is reported. The investigation of the interconversion pathway leads to the observation and characterization of two intermediates and offers a clearer view of the mechanism by which complex 2 is formed.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign