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The Structure of Potassium and Tetramethylammonium Salts of the Cyclic Organohydroborate Anion [H 2 BC 8 H 14 ] – with Different Solvent Ligands
Author(s) -
Chen Xuenian,
Liu Shengming,
Du Bin,
Meyers Edward A.,
Shore Sheldon G.
Publication year - 2007
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200700836
Subject(s) - chemistry , crystallography , solvent , potassium , boron , hydrogen , tetramethylammonium , toluene , crystal structure , inorganic chemistry , ion , coordination number , organic chemistry
Abstract Solvated potassium salts of the 9‐BBN hydroborate anion have been prepared and their structures have been determined by single‐crystal X‐ray diffraction analyses. A tetrameric complex {LK[(μ‐H) 2 BC 8 H 14 ]} 4 is formed when L is toluene, MeTHF, toluene/THF, THF/Et 2 O mixtures. The basic framework consists of a distorted K 4 B 4 cube in which potassium and boron are at alternate corners of the cube linked by bridging hydrogen atoms and α‐C–H hydrogen atoms from the 9‐BBN hydroborate that appear to form agostic interactions with potassium. There are two types of bridging hydrogen atoms: one is connected to three potassium atoms and one boron atom in a μ 4 ‐coordination arrangement, and the other one is connected to two potassium atoms and one boron atom in a μ 3 ‐coordination arrangement. There are four μ 4 ‐hydrogen arrangements in the structure. They are located inside of the K 4 B 4 cube. The four μ 3 ‐hydrogen arrangements are located outside of the distorted K 4 B 4 cube. The coordination number of potassium is 8 with the three μ 4 ‐, two μ 3 ‐bridging hydrogen atoms, two α‐C–H hydrogen atoms, and one oxygen atom of the solvent, L (there is a weak π‐η 6 interaction when the solvent is toluene). On the other hand, in the chelating solvent DME, a dimeric structure is formed in which the inner part is planar with potassium and boron located at alternate corners. The potassium is connected to four μ 3 ‐bridging hydrogen atoms, two apparent agostic α‐C–H bonding hydrogen atoms, and four oxygen atoms of two DME molecules. Its coordination number is 10 including the agostic interactions. The structure of the uncoordinated [H 2 BC 8 H 14 ] – anion is observed in the tetramethylammonium salt. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)