The reactivity of metal-metal and metal-carbon multiple bonds with 1,3-dipoles.

Abstract

The reactivity of metal-metal and metal-carbon multiple bonds with various 1,3-dipoles was investigated. A review of the literature of reactions of metal-metal and metal-carbon multiple bonds with 1,3-dipoles is presented as an introduction. The reaction of Cp$\sp*\sb2$Mo$\sb2$(CO)$\sb4$ with ethyldiazoacetate affords a $\mu$-$\eta\sp2$ diazoalkane adduct, Cp$\sp*\sb2$Mo$\sb2$(CO)$\sb4$(N$\sb2$CHCO$\sb2$Et) (2), in which the terminal nitrogen is bonded to both Mo atoms and the central nitrogen bonded to only one. The M$\equiv$M in Cp$\sb2$W$\sb2$(CO)$\sb4$ reacts with 3-aryl-2,2-dimethyl-2H-azirine to afford the terminal vinylimido complex Cp(CO)$\sb3$W-W(NC(Ar)=CMe$\sb2$)(CO)Cp (6), in which one CO ligand is semibridging to the tungsten atom containing the terminal vinylimido ligand, while Cp$\sp*\sb2$Mo$\sb2$(CO)$\sb4$ reacts with the azirine to form a terminal vinylimido complex, Cp$\sp*\sb2$Mo$\sb2$(CO)$\sb2$($\mu$-CO)$\sb2$(NC(Ar)=CMe$\sb2$) (8) containing two bridging CO ligands. The reaction of the azirine with Cp$\sb2$Mo$\sb2$(CO)$\sb4$ produces a mixture of the terminal vinylimido complex and a bridging vinylimido complex based on spectroscopic data. The W$\equiv$W triple bond in W$\sb2$(O-t-Bu)$\sb6$ reacts with two equivalents of the azirine to give W$\sb2$(O-t-Bu)$\sb6$(NC(Ar)=CMe$\sb2$)$\sb2$. The M=C double bonds in (CO)$\sb5$W=C(OMe)Ph and (Cp(CO)$\sb2$Fe=C(OMe)Me) BF$\sb4$ react with the azirine to produce the N-vinylimidate complexes (CO)$\sb5$WN(=C(OMe)Ph)C(Ar)=CMe$\sb2$ (13) and (Cp(CO)$\sb2$FeN(=C(OMe)Me)-C(Ar)=CMe$\sb2$) BF$\sb4$, respectively, from the insertion of the vinylimido group into the M=C bond. $\sp1$H and $\sp{13}$C-NMR are reported for all compounds. The crystal structures of Cp$\sp\*\sb2$Mo$\sb2$(CO)$\sb4$(N$\sb2$CHCO$\sb2$Et) (2), Cp$\sb2$W$\sb2$(CO)$\sb4$(NC(Ar)=CMe$\sb2$) (6), Cp$\sp\*\sb2$Mo$\sb2$(CO)$\sb2$($\mu$-CO)$\sb2$(NC(Ar)=CMe$\sb2$) (8), and (CO)$\sb5$WN(=C(OMe)Ph)C(Ar)=CMe$\sb2$ (13) were determined. From the results obtained in this study and the literature survey, it is postulated that in reactions of metal-metal and metal-carbon multiple bonds with 1,3-dipoles, 1,3-cycloaddition will occur only when the dipolarophile is electron rich enough to close the cycloadduct after the initial addition of the most nucleophilic end of the 1,3-dipole. In a preliminary investigation of the synthesis of organometallic polymer precursors, the functionalized alkyne complexes Cp$\sb2$Mo$\sb2$(CO)$\sb4$($\mu$,$\eta\sp2$-C$\sb2$(CH$\sb2$OR)$\sb2$) (R = H, CH$\sb3$) and Cp$\sb2$Mo$\sb2$(CO)$\sb4$($\mu$,$\eta\sp2$-PhC-CC$\equiv$CPh) were formed from the reaction of Cp$\sb2$Mo$\sb2$(CO)$\sb4$ and the appropriate alkyne.