Uranium cyclopentadienyl complexes

An unusual electron-poor cyclopentadienyl complex (C5H4PPh2, BH3)2U(BH4)2 was reported [424]. It was shown that 31P NMR spectra of borane adducts of diphenylphosphidocyclopentadienyl-uranium complexes and corresponding molybdenum heterobimetallics are very similar. This strongly suggests that such boranes... 

The tris(cyclopentadienyl)uranium(m) complexes Cp"3U and (GsMe4H)3U were prepared by synthetic routes that involve the reduction of the appropriate tetravalent uranium metallocene precursors with potassium metal and NaCioHg, respectively (Scheme 14). The molecular structure of (CsMe4H)3U shows a perfectly trigonal structure with a threefold axis (all Cp (centroid)-U-Cp (centroid) angles equal to 120°).46... 

The closest analogues of the d-block metallocenes, for the f-block elements that have been examined by P.E.S., are the tris- and tetra-cyclopentadienyl complexes, M(r7-C5H5)3 and M(t -C5H5)4. For uranium the tris cyclopentadienyl retains a donor ligand in the vapour phase and has been measured as U(i7-C5H5)3 THF. 

X-ray analysis of complex 7 showed that two of the metal-chloride bonds are shorter than the other two Th(l) - Cl(l) = 2.770(2)A, Th(l) - Cl(2) = 2.661(2)A, Th (1) - Cl(3) = 2.950(2)A, and Th(l) - Cl(4) = 2.918(2)A. The longer Th-Cl distances are those belonging to the chlorine atoms encountered in the threefold bridging positions and connected to the lithium atoms. The other two chlorine atoms are coordinated only to one lithium atom. All the Th-Cl distances are longer than those observed for terminal Th-Cl distances (Th-Cl = 2.601 A for Cp2 ThCl2 or 2.65A for Cp2 Th(Cl)Me). Ansa-chelating bis(cyclopentadienyl) complexes of uranium have been prepared as presented in Scheme 1. Bums et al. have described an efficient high yield procedure for the required U(1V) complexes [44]. 

The preparation of two cyclo-octatetraene-gold complexes, (ct)AuCl and (cot)-AU2CI4, has been reported. The structures of biscyclo-octatetraenyl complexes of titanium, vanadium, thallium, and uranium, were deduced from their i.r. spectra. Protonation of (p-cyclo-octatetraene) (p-cyclopentadienyl) complexes has been studied. For the ruthenium and osmium complexes protonation occurs on the eight-membered ring to give CgH moiety co-ordinated to the metal atom via both an T -alkyl and an olefin-metal bond. For the cobalt and rhodium complexes a bicyclic cation (287) is produced which undergoes isomerization to the monocyclic (288). ... 

Cyclopentadienyl complexes of the trivalent uranium can be prepared most commonly from UCI3 (eqs. 53-54) or, and this... 

TABLE 21. Different examples of so far investigated [101,102,111] bis- and tris-cyclopentadienyl uranium(IV) complexes (C5H R )UL( w) involving atoms... 

Ring-substituted tris(cyclopentadienyl)uranium(iv) complexes can be straightforwardly prepared from ring-substituted cyclopentadienylating reagents. Some examples are illustrated below [71, 72] ... 

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