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Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

ABSTRACT: [Ar'SnCo]2 (1, Ar' = C6H3-2,6{C6H3-2,6- iPr2}2), a rare metal-metal bonded cobalt-tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar'Sn(?-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2Sn2 core with strong metal-metal bonds between tin and cobalt and a weaker tin-tin interaction. Reaction of 1 with white phosphorus afforded [Ar'2Sn2Co2P4] (2), the first molecular cluster compound containing phosphorus, cobalt and tin.

SUBMITTER: Hoidn CM

PROVIDER: S-EPMC6194648 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature

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Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

Hoidn Christian M CM Rödl Christian C McCrea-Hendrick Madison L ML Block Theresa T Pöttgen Rainer R Ehlers Andreas W AW Power Philip P PP Wolf Robert R

Journal of the American Chemical Society 20181005 41

[Ar'SnCo]2 (1, Ar' = C6H3-2,6{C6H3-2,6- iPr2}2), a rare metal-metal bonded cobalt-tin cluster with low-coordinate tin atoms, was prepared by the reaction of [K(thf)0.2][Co(1,5-cod)2] (cod = 1,5-cyclooctadiene) with [Ar'Sn(μ-Cl)]2. This reaction illustrates a promising synthetic strategy to access uncommon metal clusters. The structure of 1 features a rhomboidal Co2S ...[more]

PMID: 30269488

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Project description:Neutral {CpFeII(CO)2[SnII(Pc•3-)]} {Cp is cyclopentadienyl (1, 2) or Cp* is pentamethylcyclopentadienyl (3); Pc: phthalocyanine}, {Cp*FeII(CO)2[SnII(Nc•3-)]} (4, Nc: naphthalocyanine), and {CpFeII(CO)2[SnII(TPP•3-)]} (5, TPP: tetraphenylporphyrin) complexes in which CpFeII(CO)2 fragments (Cp: Cp or Cp*) are coordinated to SnII(macrocycle•3-) have been obtained. The product complexes were obtained at the reaction of charge transfer from CpFeI(CO)2 (Cp: Cp or Cp*) to [SnII(macrocycle2-)] to form the diamagnetic FeII and paramagnetic radical trianionic macrocycles. As a result, these formally neutral complexes contain S = 1/2 spins delocalized over the macrocycles. This provides alternation of the C-Nimine or C-Cmeso bonds in the macrocycles, the appearance of new bands in the near-infrared spectra of the complexes, and blue shift of both Soret and Q-bands. The {CpFeII(CO)2SnII(macrocycle•3-)} units (Cp: Cp or Cp*, macrocycle: Pc or Nc) form closely packed π-stacking dimers in 1 and 3 or one-dimensional chains in 2 and 4 with effective π-π interaction between the macrocycles. Such packing allows strong antiferromagnetic coupling between S = 1/2 spins. Magnetic interaction can be described well by the Heisenberg model for the isolated dimers in 1 and 3 with exchange interaction J/k B = -78 and -85 K, respectively. Magnetic behavior of 2 and 4 is described well by the model that includes contributions from an antiferromagnetically coupled S = 1/2 dimer (J intra) and a Heisenberg S = 1/2 chain with alternating antiferromagnetic spin exchange between the neighbors (J inter). Compound 2 demonstrates large intradimer interaction of J intra/k B = -54 K and essentially weaker interdimer exchange interactions of J inter/k B = -6 K, whereas compound 4 shows strong magnetic coupling of spins within the dimers (J intra/k B = -170 K) as well as between the dimers (J inter/k B = -40 K). Compound {CpFeII(CO)2[SnII(TPP•3-)]} (5) shows no π-π interactions between the porphyrin macrocycles, and magnetic coupling is weak in this case (Weiss temperature is -5 K). Preparation of a similar complex with indium(III) chloride phthalocyanine yields {CpFe(CO)2[In(Pc2-)]} (6). In this complex, indium(III) atoms are reduced instead of the phthalocyanine macrocycles that explains electron paramagnetic resonance silence of 6 in the 4-295 K range.

Project description:To address the challenge of selectivity toward single products in Cu-catalyzed electrochemical CO2 reduction, one strategy is to incorporate a second metal with the goal of tuning catalytic activity via synergy effects. In particular, catalysts based on Cu modified with post-transition metals (Sn or In) are known to reduce CO2 selectively to either CO or HCOO- depending on their composition. However, it remains unclear exactly which factors induce this switch in reaction pathways and whether these two related bimetal combinations follow similar general structure-activity trends. To investigate these questions systematically, Cu-In and Cu-Sn bimetallic catalysts were synthesized across a range of composition ratios and studied in detail. Compositional and morphological control was achieved via a simple electrochemical synthesis approach. A combination of operando and quasi-in situ spectroscopic techniques, including X-ray photoelectron, X-ray absorption, and Raman spectroscopy, was used to observe the dynamic behaviors of the catalysts' surface structure, composition, speciation, and local environment during CO2 electrolysis. The two systems exhibited similar selectivity dependency on their surface composition. Cu-rich catalysts produce mainly CO, while Cu-poor catalysts were found to mainly produce HCOO-. Despite these similarities, the speciation of Sn and In at the surface differed from each other and was found to be strongly dependent on the applied potential and the catalyst composition. For Cu-rich compositions optimized for CO production (Cu85In15 and Cu85Sn15), indium was present predominantly in the reduced metallic form (In0), whereas tin mainly existed as an oxidized species (Sn2/4+). Meanwhile, for the HCOO--selective compositions (Cu25In75 and Cu40Sn60), the indium exclusively exhibited In0 regardless of the applied potential, while the tin was reduced to metallic (Sn0) only at the most negative applied potential, which corresponds to the best HCOO- selectivity. Furthermore, while Cu40Sn60 enhances HCOO- selectivity by inhibiting H2 evolution, Cu25In75 improves the HCOO- selectivity at the expense of CO production. Due to these differences, we contend that identical mechanisms cannot be used to explain the behavior of these two bimetallic systems (Cu-In and Cu-Sn). Operando surface-enhanced Raman spectroscopy measurements provide direct evidence of the local alkalization and its impact on the dynamic transformation of oxidized Cu surface species (Cu2O/CuO) into a mixture of Cu(OH)2 and basic Cu carbonates [Cux(OH)y(CO3)y] rather than metallic Cu under CO2 electrolysis. This study provides unique insights into the origin of the switch in selectivity between CO and HCOO- pathways at Cu bimetallic catalysts and the nature of surface-active sites and key intermediates for both pathways.

Dataset Information

Synthesis of a Cyclic Co2Sn2 Cluster Using a Co- Synthon.

Publications

Synthesis of a Cyclic Co<sub>2</sub>Sn<sub>2</sub> Cluster Using a Co<sup>-</sup> Synthon.

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