Synthesis and structure of Cp ₃ UCHPMe ₃ : A compound with a UC multiple bond

Abstract

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.

Covalent Uranium Carbene Chemistry

“…[42] In 1988, this series was extended further by Gilje and Schmidbaur, with the reported preparation of [(Cp) 3 U = CHPMe 3 ] (3). [43] Complex 3 was reported to have a U-C distance of 2.293(2) Å , which is statistically indistinguishable from the U-C distance in 1. [39][40][41][42] The short U-C distances, together with the three-coordinate nature of the carbon center, allowed multiple bond character to be ascribed to the U=C bond and, in the years that followed the preparation of 1 and 2, a raft of reactivity studies were performed in order to assess the nature of the formal U=C double bond.…”

The Nature of the UC Double Bond: Pushing the Stability of High‐Oxidation‐State Uranium Carbenes to the Limit

“…However, sterically demanding PhCOtBu and Ph 2 CO ketones do not appear to react with 5, presumably for steric reasons. In contrast, less bulky and more reactive PhCHO reacts with 5 to give the alkene (DippNPPh 2 ) 2 C=C(H)Ph (12) in 65 % yield as yellow crystals (Scheme 2 and Figure 5 c), and this compound has been fully characterised. The uranium-containing by-product could not be identified, but it is likely that eliminated "UOCl 2 " undergoes ligand scrambling, oligomerisation and/ or disproportionation reactions.…”

“…, [14] [U-A C H T U N G T R E N N U N G (BIPM TMS )(Cl) 2 (I)] [14] and [(BIPM TMS )U(O)(Cl) 2 ], [16] provides a structurally related series of uranium carbenes to probe the nature of the U=C double bonds across a range of oxidation states of uranium. In addition, complex 9 repre-sents a link to mono-phosphanyl uranium carbenes [12] because the carbene ligand in 9 ligates with only one arm. Thus, we performed DFT calculations on 2, 5 and 9.…”

“…In contrast, complex 5 does not react with PhCOtBu and Ph 2 CO, which we attribute to steric blocking. However, complexes 5 and 6 react with PhCHO to afford (DippNPPh 2 ) 2 C=C(H)Ph (12). Complex 9 does not react with PhCOtBu, Ph 2 CO or PhCHO; this is attributed to steric blocking.…”

Actinide Organometallic Complexes with π‐Ligands

“…With the Cp ligands in the coordination sphere of au ranium atom it is possible to stabilise for example carbenec omplexes with M=Ci nteractions of 227 to 239 pm. [9] This compares to UÀCs ingle bond lengthsw hich are found to be longer in the range between 245 and 255 pm. [10] Due to conjugative effects the UÀCb ond lengths in complexes with terminal bound acetylene are found to be shorter in the range of 234 to 244 pm.…”