Syntheses of Molybdenum Adamantylimido and t‑Butylimido Alkylidene Chloride Complexes Using HCl 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.