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• 67506-89-2 bis(pentamethylcyclopentadienyl)dichlorouranium(IV) 
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Relevant academic research and scientific papers

Reactivity of tuck-in and tuck-over uranium metallocene complexes

The reactivity of the uranium tuck-in and tuck-over cyclopentadienyl moieties {[ν5:ν1-C5Me4CH 2]U}2+ and {U[μ- ν5:ν1- C5Me4CH2]U}6+, respectively, has been investigated by examining the reactivity of (C5Me 5)U[μ- ν5:ν1:ν1-C 5Me3(CH2)2](μ-H) 2U(C5Me5)2, 1, and (C 5Me5)(ν5:ν1-C 5Me4CH2)(hpp)U [(hpp)- = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato], 2, with hydrogen, silyl halide, sulfide, amine, and hydrocarbon reagents. The reactivity of 2, which has a single tuck-in reactive site, provides valuable comparisons with that of 1, where the presence of two hydride ligands as well as both tuck-in and tuck-over moieties leads to products in which multiple transformations have occurred. Both 1 and 2 react with H2 to form hydrides, namely, the [(C 5Me5)2UH2]2/[(C 5Me5)2UH]2 equilibrium mixture and (C5Me5)2(hpp)UH, 3, respectively. Attempts to make a simple chloride derivative of 1 with Me3SiCl yielded a new tethered metallocene, (C5Me5)ClU(ν5-C 5Me4CH2SiMe2CH2-κC) , 4, which formally results from a silylmethyl C-H bond activation as well as insertion of the silyl group into the U-CH2 tuck-in linkage. The trivalent chloride [(C5Me5)2UCl]3, 5, is the byproduct of this reaction. This sequence of reactions is probably not initiated by the tuck-in functionality, since 2 does not react with Me 3SiCl under comparable conditions. Hydride complex 3 reacts readily with Me3SiCl to form (C5Me5) 2(hpp)UCl, but (C5Me5)2(hpp)UMe, 6, requires 100 °C to form the chloride. Complex 1 also displays complicated reactivity with HC=CPh, whereas 2 and 3 react with this substrate to form (C5Me5)2(hpp)U(C=CPh), 7, in high yield. Complex 1 converts PhSSPh cleanly to (C5Me5) 2U(SPh)2, 8, in a reaction that involves S-S cleavage and C-H bond formation. Complex 1 reacts with a 1:1 mixture of PhSSPh and p-tolylSS-p-tolyl to form a 1:2:1 mixture of (C5Me5) 2U(SPh)2, 8, (C5Me5) 2U(SPh)(S-p-tolyl), 9, and (C5Me5) 2U(S-p-tolyl)2, 10, but the mechanistic implications are compromised by exchange of 8 with 10 to make 9. PhSH, a possible intermediate in a δ-bond metathesis reaction pathway for the 1/PhSSPh reaction, reacts with 1 to form 8. Complex 2 forms a δ-bond metathesis product, (C 5Me4CH2SPh)(C5Me5)(hpp) U(SPh), 11, from PhSSPh that contains a new peralkylated cyclopentadienyl ligand. The reaction of 2 and PhSH forms (C5Me5) 2(hpp)U(SPh), 12. Complexes 1 and 2 react similarly with PhNH 2 to generate amide products (C5Me5) 2U(NHPh)2, 13, and (C5Me5) 2(hpp)U(NHPh), 14, respectively. No reactions were observed between complex 1 or 2 and methane, benzene, or toluene, but 1 and 2 react with CuI to form (C5Me5)2UI2, 15, and (C 5Me5)2(hpp)UI, 16, respectively, in which the CH2 tuck components have been converted to methyl groups.