Complexes Written with Prof. Jack R Norton

Vinyl Complexes (Written with Prof. Jack R. Norton) 

Vinyl complexes are typically prepared by the same methods used to prepare aryl complexes. Vinyl mercury compounds, like aryl mercury compoimds, are easily prepared (by the mercuration of acetylenes), and are therefore useful for the preparation of vinyl transition metal complexes by transmetallation. The use of vinyl lithium reagents has permitted the s rnthesis of homoleptic vinyl complexes by transmetallation (Equation 3.35). Reactive low-valent transition metal complexes also form vinyl complexes by the oxidative addition of vinyl halides with retention of stereochemistry about the double bond (Equation 3.36). Vinyl complexes have also been formed by the insertion of alkynes into transition metal hydride bonds (Equation 3.37), by sequential electrophilic and nucleophilic addition to alkynyl ligands (Equation 3.38), and by the addition of nucleophiles to alkyne complexes (Equation 3.39). The insertion of alkynes into transition metal alkyl complexes is presented in Chapter 9 and, when rearrangements are slower than insertion, occurs by s)m addition. In contrast, nucleophilic attack on coordinated alkynes, presented in Chapter 11, generates products from anti addition. 

Recent calculations suggest that the M-C bonds in vinyl complexes have approximately the same strength as those in aryl complexes. However, the Ir-vinyl bond in Cp Ir(PMe3) (vinyhy for which the Ir-vinyl BDE is 71 kcal/mol, is 11 kcal/mol weaker dian die Ir-C bond in Cp Ir(PMe3)Ph2, for which the Ir-Ph BDE is 82 kcal/mol.  

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