Intramolecular carbon-hydrogen bond activation of benzyl ligands by metalated cyclopentadienyl derivatives of permethylhafnocene. Molecular structure of (.eta.5-C5Me5)(.eta.5,.eta.1-C5Me4CH2)HfCH2C6H5 and the mechanism of rearrangement to its hafnabenzocyclobutene tautomer [cyclic] (.eta.5-C5Me5)2Hf(o-CH2C6H4)

A comparative study of the reactivity of Zr(IV), Hf(IV) and Th(IV) metallocene complexes: Thorium is not a Group IV metal after all

“…The selected metrical parameters for complex 16 compare well with those reported for the two other structurally characterized hafnium phenyl compounds, [N(SiMe 2 CH 2 PMe 2 ) 2 ]Hf(Ph)( 4 -C 4 H 6 ) (Hf-C ipso = 2.290(6)Å, C-C ipso -C = 112.7(6) • ) [26a] and [NBu 4 ][Hf(C 6 Cl 5 ) 3 Cl 2 ] (Hf-C ipso = 2.259 (13) Compound 17 also possesses a distorted tetrahedral coordination environment about the hafnium center with the two benzyl ligands situated in the metallocene wedge. The Hf(1)-C(11) (2.291(7)Å) and Hf(1)-C(18) (2.294(7)Å) bond lengths fall within the range typically observed for a hafniumbenzyl linkage (2.214(7)-2.374(9)Å) [24,27]. For example, the tris(benzyl) complexes, (C 5 H 5 B-CH 2 Ph)Hf(CH 2 Ph) 3 and (C 5 Me 5 )Hf(CH 2 Ph) 3 , have Hf CH 2 bond distances of 2.234 (3) (3), and 2.282(6)Å [24], respectively.…”

Experimental and Computational Studies of Ruthenium(II)-Catalyzed Addition of Arene C−H Bonds to Olefins

“…73 DFT studies suggest that the C-H activation steps of the catalytic cycles do not proceed through a Ru(IV) oxidative addition intermediate, and the Tp ligand may deter processes that lead to seven-coordinate Ru(IV) systems. 61 As previously discussed, 64,76,77 for C-H activations that proceed without an oxidative addition intermediate a distinction can be made between σ-bond metathesis and electrophilic aromatic substitution. The calculated transition state for benzene C-H activation by {(Tab)Ru(CO)(CH 3 )} reveals that the hydrogen atom undergoing transfer to the methyl ligand is out of the aromatic plane (Figure 6).…”

A Crystallizable f‐Element Tuck‐In Complex: The Tuck‐in Tuck‐over Uranium Metallocene [(C5Me5)U{μ‐η5:η1:η1‐C5Me3(CH2)2}(μ‐H)2U(C5Me5)2]

“…[1][2][3][4] Although C 5 Me 5 À is more resistant to attack on the C À H bond, its methyl groups can be metalated with some highly reactive metal species. [5][6][7][8][9][10] Since these CÀH activated ligands arise from extremes in reactivity, they have been involved in unprecedented reactions. For example, the homogeneous CÀ H activation of methane was first discovered with [{(C 5 Me 5 ) 2 LuMe} n ] [5] based on a mechanism involving the "tucked-in" [6] complex "[(C 5 Me 5 ){C 5 Me 4 (CH 2 )}Lu]".…”

“…Tuck-in complexes have been crystallographically characterized with transition metals. [7,9,10,12] For example, in the {(C 5 Me 5 ) 2 TiH} system, [(C 5 Me 5 )Ti{h 5 :h 1 -C 5 Me 4 (CH 2 )}] (1) could be isolated. [7] However, in these transition-metal tuckin compounds, low-oxidation-state tetramethylfulvalene resonance structures can contribute to the stability of the complexes.…”