Synthesis and Structure of Sn₁₄Cl₆(CH₂SiMe₃)₁₂: Toward Nanoclusters of 4-Coordinate α-Sn

Abstract

Orange crystals of a Sn cluster have been isolated in up to 22% yield from a reaction between MeSiCHSnCl, SnCl, and LiAlH. The structure determined by single crystal X-ray diffraction shows three unique Sn atoms in a 6:6:2 ratio, with all Sn atoms 4-coordinate, similar to the tetrahedral bonding in elemental gray Sn. The solid state Sn MAS NMR spectrum shows the three types of distinct Sn atoms in the expected 3:3:1 intensity ratio with respective chemical shifts of 87.9, -66.6, and -607.1 ppm relative to MeSn. The chemical shift of the two Sn atoms without ligands (bonded only to Sn), at -607.1 ppm, is the most upfield, and is the closest to the chemical shift, reported here, of bulk gray tin (-910 ppm). First-principles density functional theory calculations of the chemical shielding tensors corroborate this assignment. While the core coordination is distorted from the ideal tetrahedral arrangement in the diamond structure of gray tin, this Sn cluster, as the largest reported cluster with all 4-coordinate Sn, represents a major incremental step toward being able to prepare atomically precise nanoparticles of gray tin.

Halides of the Heavier Group 14 Homologues Germanium, Tin, and Lead—A Journey through Unusual Compounds and Oxidation States

“… Reaction pathways and molecular structures of the cluster compounds a) [(Me 3 Si) 2 CHGe] 6 , b) [Ge 8 (Et 2 C 6 H 3 ) 8 ], c) [ t Bu 8 Ge 8 Br 2 ], d) [Sn 14 Cl 6 (CH 2 SiMe 3 ) 12 ] . The hydrogen atoms are omitted for clarity.…”

“…To prepare SnX 4 (X=Cl, Br,I ), halogen gas is passed over elementalt in at different temperatures, whereas SnF 4 can be obtained by treating SnCl 4 with water-free HF.I nt he molecular structures,t he 2 CHGe] 6 , [11] b) [Ge 8 (Et 2 C 6 H 3 ) 8 ], [12] c) [tBu 8 Ge 8 Br 2 ], [16] d) [Sn 14 Cl 6 (CH 2 SiMe 3 ) 12 ]. [19] The hydrogen atoms are omitted for clarity. SnX 4 molecules possess nearly perfect tetrahedral symmetry.…”

“…Recently,P urdy and coworkers presented the compound [Sn 14 Cl 6 (CH 2 SiMe 3 ) 12 ] ( Figure 1d), which they obtained by the reduction of the mixture of tin tetrachloride and Me 3 SiCH 2 SnCl 3 with LiAlH 4 .W ithin [Sn 14 Cl 6 (CH 2 SiMe 3 ) 12 ]a ll tin atoms are tetra-coordinated, but do not resemble the structure of gray tin with ad iamondl attice. [19]…”

Optical Absorption of Atomically-Precise Sn14 Nanoclusters: The Antagonistic Interplay of Ligand Stabilization, Molecular Symmetry, and Solvatochromism

“…Sophisticated preparation methods now allow the synthesis of ligand-stabilized metal and semiconductor clusters of defined sizes. , By investigating isolated clusters of the same size in the gas phase it is thus possible to determine the influence of ligand stabilization on the geometric and electronic properties of the clusters. Purdy and co-workers recently reported the synthesis of a tin nanocluster with the composition Sn 14 Cl 6 (CH 2 SiMe 3 ) 12 , which contains only 4-fold-coordinated tin atoms (Figure ) and is different from low-valent and predominantly metallic-bonded Sn 14 substructures found as enneahedra in Zintl phases . This bears similarities to the elementary gray α-tin, although the geometric arrangement of the atoms in the cluster differs from that of the diamond structure of gray α-tin.…”

“…Comparison of the ligand-stabilized Sn 14 cluster 1a and its locally-optimized Sn 14 fragment 1c in S 6 symmetry with the global minimum structure 1b found in gas-phase experiments in the C s symmetry. Sn atoms are shown in gray, Cl atoms in blue, Si atoms in orange, C atoms in black, and H atoms in red.…”