Green, crystalline Cp3U =CHPMe3 has been synthesized by the reaction of Cp3UCl with Li[CHJ2PMe, or CHI = PMe3. Its crystal structure has been d e t d n e d by single crystal X-ray diffraction. The short U=CH bond distance, 2274(8)A, and large U-C-P angle, 143.5(5)", indicate uranium-carbon multiple bond character. The '4"C'H) coupling constants within the CH group between uranium and phosphorus in Cp3U = CHPMe, (95 Hz), Cp3U=CHPMePh (100 Hz), and Cp3U=CHPPhtMe (1 13 Hz) are surprisingly small, but no agostic interaction UCHP can be derived from the structural data.Several years ago we reported" the synthesis of Cp,U = CHPMePh? and Cp,U =CHPMe2Ph, C p = qS-C5H<. Based on the structure of Cp3U =CHPMe2Ph, which contains the shortest known uranium-carbon bond and a large U -C -P angle, we postulated these were the first compounds to contain f-element-carbon multiple bond^^.^'. This assignment was further supported by EHMO calculations4'. As part of an ongoing effort to characterize the chemistry5' and the nature6." of actinide-ligand bonding we have now prepared Cp,U =CHPMe3, which is the simplest Cp,U = CHPMeRR' compound, and have found that the "C-H coupling constants for the alpha CH group in the compounds of this series are small. To search for a structural reason for these low values we determined the crystal structure of Cp3U =CHPMe3.
Results and Discussion
action (1)CplUCl + LiCH2CH2PMe2 -+ Cp,U=CHPMe, + LiCl (1) using the same procedure originally developed for Cp,U = CHPMe,Ph and Cp,U = CHPMePh,''. It can also be prepared by the direct reaction of H2C=PMe3 with Cp,U=CHPMe3 can be obtained in good yield by reCp,UCl:Cp3U=CHPMe3 is an air and moisture sensitive, pyrophoric green solid which is soluble in T H F and aromatic solvents, but virtually insoluble in aliphatic hydrocarbons.