Dimers that Contain Unbridged W(IV)/W(IV) Double Bonds

Compounds that contain an unbridged W W bond can be prepared through bimolecular decomposition of various imido alkylidene complexes. One type of W W species is [W(NR)(CH 2 -t-Bu)(OR‘)] 2 (R = 2,6-dimethylphenyl (Ar‘) or 2,6-diisopropylphenyl (Ar); R‘ = pentafluorophenyl or hexafluoroisopropyl), which is found in both heterochiral and homochiral forms. The other type is [W(NR)(OR‘) 2 ] 2 (R‘ = trifluoro- tert -butyl or hexafluoro- tert -butyl). All species contain an unbridged W(IV)/W(IV) double bond with a W W bond distance of 2.4−2.5 Å, a 90° angle between the imido ligands and the W W bond, and an anti relationship of the imido ligands. There is no indication that W W bonds are broken spontaneously; for example, heterochiral and homochiral [W(NR)(CH 2 -t-Bu)(OR‘)] 2 species do not interconvert.