Investigating Metal Size Effects in the Ln₂(μ-η²:η²-N₂) Reduction System: Reductive Reactivity with Complexes of the Largest and Smallest Trivalent Lanthanide Ions, La³⁺and Lu³⁺

Abstract

Metal size effects in reductive chemistry using [(C(5)Me(4)H)(2)Ln(THF)](2)(mu-eta(2):eta(2)-N(2)) complexes have been evaluated using the extremes in ionic radii of the lanthanide series, Ln = La, 1, and Lu, 2. Comparisons have been made using 1,3,5,7-cyclooctatetraene, phenazine, carbon dioxide, and anthracene as substrates. Complexes 1 and 2 react similarly with 1,3,5,7-cyclooctatetraene to form (C(5)Me(4)H)(3)Ln and (C(5)Me(4)H)Ln(C(8)H(8))(THF)(x) (Ln = La, x = 2, or Lu, x = 0) in a reaction analogous to the reduction of this substrate with divalent (C(5)Me(5))(2)Sm. Complexes 1 and 2 differ in their reactions with phenazine in that 1 forms at least three products, including [(C(5)Me(4)H)(2)La](mu-eta(4):eta(2)-C(12)H(8)N(2))[La(THF)(C(5)Me(4)H)(2)], 3, and (C(5)Me(4)H)(3)La, whereas 2 forms a single product, [(C(5)Me(4)H)(2)Lu](2)(mu-eta(3):eta(3)-C(12)H(8)N(2)), 4, in quantitative yield. Complexes 3 and 4 are similar to the product obtained from the reaction of (C(5)Me(5))(2)Sm and phenazine, [(C(5)Me(5))(2)Sm](2)(mu-eta(3):eta(3)-C(12)H(8)N(2)), since all three complexes contain a reduced phenazine dianion, but the phenazine ligand displays structural variations depending on the size of the metal. With CO(2), complex 1 forms multiple products, but 2 reacts cleanly to form the reductively coupled oxalate complex, [(C(5)Me(4)H)(2)Lu](2)(mu-eta(2):eta(2)-C(2)O(4)), 5, in high yield. With anthracene, 1 forms a complex product mixture from which only (C(5)Me(4)H)(3)La(THF), 9, characterized by X-ray crystallography, could be identified. In contrast, 2 is unreactive toward anthracene even upon heating to 75 degrees C after 24 h.

Advances in f element reductive reactivity as a paradigm for expanding lanthanide and actinide science and technology

“…As shown in Scheme 11 [114], the trivalent lanthanum complex, [(C 5 Me 5 ) 2 (THF)La] 2 ( -Á 2 :Á 2 -N 2 ), reduces anthracene to make a (C 14 H 10 ) 2− complex analogous to that obtained previously with (C 5 Me 5 ) 2 Sm [70]. Carbon dioxide can be reductively coupled to form an oxalate as shown in Scheme 12 by an analogous tetramethylcyclopentadienyl lutetium complex, [(C 5 Me 4 H) 2 (THF)Lu] 2 ( -Á 2 :Á 2 -N 2 ) [115].…”

Small Molecule Activation by Uranium Tris(aryloxides): Experimental and Computational Studies of Binding of N2, Coupling of CO, and Deoxygenation Insertion of CO2under Ambient Conditions

“…as well as the formation of oxalate from two molecules of CO 2 by a Lu N 2 complex 68. Thus it is of interest to identify potential CO 2 chemistry with these simple tris(ligand) systems.…”

Dinitrogen and Related Chemistry of the Lanthanides: A Review of the Reductive Capture of Dinitrogen, As Well As Mono- and Di-aza Containing Ligand Chemistry of Relevance to Known and Postulated Metal Mediated Dinitrogen Derivatives

“…Hetero-/multinuclear Lanthanide complexes such as these macrocyclic examples suggest that bimetallic complex formation and additional external electron sources greatly widen the range of reduced dinitrogen species that can be obtained for metals that do not have widely accessible oxidation states. Lanthanide mediated dinitrogen reduction utilising an external electron source has since been reported for the entire lanthanide series excepting Eu and Yb [43,44,45,46,47]. The lanthanide centre in each case was supported by bis(trimethylsilyl)amide ligands as shown for the Gd example shown in Figure 4.…”

“…Organolanthanide complexes containing a dinitrogen moiety are limited primarily to those of anionic (N 2 ) n- , n = 2, 3, 4, species from dinitrogen reduction, as discussed above [34,35,36,37,38,39,40,41,42,43,44,45,46,47], and reduced azobenzene compounds, (RNNR) n- , n = 1, 2, which relate to the diazenido and hydrazido species proposed in the Chatt cycle. The first organolanthanide azo complex, [{(C 5 Me 5 )Sm} 2 (μ-η 1 :η 1 -N 2 Ph 2 )], ( X ), contained two samarium(III) centres, bridged by a dianionic trans -azobenzene moiety, which exhibited lengthening in the N-C(phenyl) bonds of the azobenzene unit without lengthening (and inferred reduction) of the N=N bond (1.25(1) Å).…”