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

The reductive reactivity of a Ln(II) ion with a nontraditional 4fn5d1 electron configuration has been investigated by studying reactions of the {GdII(N(SiMe3)2)3]}- anion with a variety of reagents that survey the many reaction pathways available to this ion. The chemistry of both [K(18-c-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. CS2 reacts with the crown salt [K(18-c-6)2][Gd(NR2)3] (1) to generate the bimetallic (CS3)2- complex {[K(18-c-6)](µ3-CS3-κS,κ2S',S'')Gd(NR2)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 CS2 with the crypt salt [K(crypt)][Gd(NR2)3] (2) is [K(crypt)]{(R2N)2Gd[SCS(CH2)Si(Me2)N(SiMe3)-κN,κS]}, which has a CS2 unit inserted into a cyclometalated amide ligand. Complexes 1 and 2 reductively couple pyridine to form bridging dipyridyl moieties, (NC5H4-C5H4N)2-, that generate bimetallic complexes differing only in the countercation, {[K(18-c-6)(C5H5N)2]}2{[(R2N)3Gd]2[µ-(NC5H4-C5H4N)2]} and [K(crypt)]2{[(R2N)3Gd]2[µ-(NC5H4-C5H4N)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)][(R2N)3Gd(η1-ONC5H6Me4)] and [K(crypt)][(R2N)3Gd(η1-ONC5H6Me4)], respectively. The first example of a bimetallic coordination complex containing a Bi-Gd bond, [K(crypt)][(R2N)3Gd(BiPh2)], was obtained by treating 2 with BiPh3.