Syntheses of Molybdenum Adamantylimido and t-Butylimido Alkylidene Chloride Complexes Using HCI and Diphenylmethylphosphine.

Reactions between Mo(N-t-Bu)2(CH2-t-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 Z-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-t-butylterphenoxide) maximize when OAr is OHMT or OHIPT. Mo(N-t-Bu)(CH-t-Bu)(PPh2Me)Cl2 is essentially inactive for the reaction between cyclooctene and Z-1,2-dichloroethylene. X-ray structural studies were carried out on Mo(NAd)(CHCMe2Ph)(PPh2Me)Cl2, Mo(N-t-Bu)(CH-t-Bu)(PPh2Me)(OHMT)Cl, Mo(NAd)(CHCMe2Ph)(Cl)(OHTBT)(PMe3), and [Mo(NAd)(CHCMe2Ph)(PMe3)(Cl)]2(μ-O), the product of the reaction between Mo(NAd)(CHCMe2Ph)(Cl)(OHTBT)(PMe3) and 0.5 equiv of water.