Reductive Reactivity of the 4f⁷5d¹ Gd(II) Ion in {Gd^II[N(SiMe₃)₂]₃}⁻: Structural Characterization of Products of Coupling, Bond Cleavage, Insertion, and Radical Reactions

Abstract

The reductive reactivity of a Ln(II) ion with a nontraditional 4f n 5d 1 electron configuration has been investigated by studying reactions of the {Gd II (N(SiMe 3 ) 2 ) 3 ]} − anion with a variety of reagents that survey the many reaction pathways available to this ion. The chemistry of both [K(18c-6) 2 ] + and [K(crypt)] + salts (18-c-6 = 18-crown-6; crypt = 2.2.2-cryptand) was examined to study the effect of the countercation. CS 2 reacts with the crown salt [K(18-c-6) 2 ][Gd(NR 2 ) 3 ] (1) to generate the bimetallic (CS 3 ) 2− complex {[K(18-c-6)](μ 3 -CS 3 -κS,κ 2 S′,S′′)Gd(NR 2 ) 2 ]} 2 , which contains two trithiocarbonate dianions that bridge Gd(III) centers and a potassium ion coordinated by 18-c-6. In contrast, the only crystalline product isolated from the reaction of CS 2 with the crypt saltwhich has a CS 2 unit inserted into a cyclometalated amide ligand. Complexes 1 and 2 reductively couple pyridine to form bridging dipyridyl moieties, (NC 5 H 4 -C 5 H 4 N) 2− , that generate bimetallic complexes differing only in the countercation, {[K(18-c-6)(C 5 H 5 N) 2 ]} 2 {[(R 2 N) 3 Gd] 2 [μ-(NC 5 H 4 -C 5 H 4 N) 2 ]} and [K(crypt)] 2 {[(R 2 N) 3 Gd] 2 [μ-(NC 5 H 4 -C 5 H 4 N) 2 ]}. Complexes 1 and 2 also show similar reactivity with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) to form the (TEMPO) − complexes [K(18-c-6)][(R 2 N) 3 Gd(η 1 -ONC 5 H 6 Me 4 )] and [K(crypt)][(R 2 N) 3 Gd(η 1 -ONC 5 H 6 Me 4 )], respectively. The first example of a bimetallic coordination complex containing a Bi− Gd bond, [K(crypt)][(R 2 N) 3 Gd(BiPh 2 )], was obtained by treating 2 with BiPh 3 .

Reductive C–O Cleavage of Ethereal Solvents and 18-Crown-6 in Ln(NR2)3/KC8Reactions (R = SiMe3)

“…The X-ray crystal structure shows a methyl group of an (NR 2 ) 1– ligand oriented toward the potassium in the crown in the side opposite the coordinated oxetane. This type of structure has been observed before with the [K­(18-c-6)] 1+ cation. − …”

“…In this case, the complex crystallized as an extended structure in which the [K­(18-c-6)] 1+ cation has a methyl group of a Me 3 Si unit on one side and a methylene of a (SiMe 2 CH 2 ) moiety on the other side. There is precedence in the structural chemistry of the [K­(18-c-6)] 1+ cation, showing that it can form extended structures with silylmethyl groups oriented toward the potassium. − In the (2,2,6,6-tetramethylpiperidin-1-yl)­oxyl complex, {[(18-c-6)­K]­[(μ-Me 3 Si)­(Me 3 Si)­N] 2 [Gd­(NR 2 )­(η 1 -ONC 5 H 6 Me 4 )]} n , trimethylsilyl groups are oriented to both sides of the {[(18-c-6)­K] 1+ cation …”

Charge Makes a Difference: Molecular Ionic Bismuth Compounds

“…The Li−Bi distances in 4 are identical to the Li−Sb distances in the lighter homolog, suggesting relatively strong Li⋅⋅⋅Bi interactions in this complex [160] . The compound [K(crypt)][BiPh 2 ] (crypt=2.2.2‐cryptand) has been obtained serendipitously in single‐crystalline form and shows a two‐coordinate bismuth atom [161] …”

“…[160] The compound [K(crypt)]-[BiPh 2 ] (crypt = 2.2.2-cryptand) has been obtained serendipitously in single-crystalline form and shows a two-coordinate bismuth atom. [161] Scheme 10. Calculated molecular structures of clusters [La@Sn 7 Bi 7 ] 4À (a) and [La@Sn 4 Bi 9 ] 4À (b) upon geometry optimization using DFT methods, and illustration of representative localized molecular orbitals (LMOs).…”

A DFT perspective on organometallic lanthanide chemistry

“…The biggest surprise was that, in an appropriate ligand environment, 4f n 5d 1 orbital occupation may become feasible in the so-called unconventional Ln 2+ ions. The 5d orbitals in these ions have greater spatial extent and overlap significantly with ligand orbitals, thus presenting new opportunities for coordination chemistry 6,[10][11][12] and enabling unique chemical reactivity [13][14][15][16] and magnetic properties. [17][18][19][20] We discuss examples of structures, molecular properties, and reactivities of low-valent lanthanide complexes in the following.…”