Syntheses of Molybdenum Adamantylimido and <i>t</i>-Butylimido Alkylidene Chloride Complexes Using HCl and Diphenylmethylphosphine

Abstract

Reactions between Mo(N-<i>t</i>-Bu)₂(CH₂-<i>t</i>-Bu)₂ or Mo(NAdamantyl)₂(CH₂CMe₂Ph)₂ and 3 equiv of HCl in the presence of 1 equiv of PPh₂Me yield Mo(NR)(CHR')(PPh₂Me)Cl₂ complexes, from which Mo(NR)(CHR')(PPh₂Me)(OAr)Cl complexes (OAr = a 2,6-terphenoxide) can be prepared. The Mo(NR)(CHR')(PPh₂Me)(OAr)Cl complexes were evaluated as cross-metathesis catalysts between cyclooctene and <i>Z</i>-1,2-dichloroethylene. The efficiencies of the test reaction for complexes in which OAr = OTPP, OHMT, OHIPT, or OHTBT (where OTPP is 2,3,5,6-tetraphenylphenoxide, OHMT is hexamethylterphenoxide, OHIPT is hexaisopropylterphenoxide, and OHTBT is hexa-<i>t-</i>butylterphenoxide) maximize when OAr is OHMT or OHIPT. Mo(N-<i>t</i>-Bu)(CH-<i>t</i>-Bu)(PPh₂Me)Cl₂ is essentially inactive for the reaction between cyclooctene and <i>Z</i>-1,2-dichloroethylene. X-ray structural studies were carried out on Mo(NAd)(CHCMe₂Ph)(PPh₂Me)Cl₂, Mo(N-<i>t</i>-Bu)(CH-<i>t</i>-Bu)(PPh₂Me)(OHMT)Cl, Mo(NAd)(CHCMe₂Ph)(Cl)(OHTBT)(PMe₃), and [Mo(NAd)(CHCMe₂Ph)(PMe₃)(Cl)]₂(<i>μ</i>-O), the product of the reaction between Mo(NAd)(CHCMe₂Ph)(Cl)(OHTBT)(PMe₃) and 0.5 equiv of water.