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The closo ‐[Sn 9 M(CO) 3 ] 4− Zintl Ion Clusters where M=Cr, Mo, W: Two Structural Isomers and Their Dynamic Behavior
Author(s) -
Kesanli Banu,
Fettinger James,
Eichhorn Bryan
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20011217)7:24<5277::aid-chem5277>3.0.co;2-c
Subject(s) - chemistry , mesitylene , crystallography , cycloheptatriene , ion , crystal structure , ethylenediamine , nuclear magnetic resonance spectroscopy , stereochemistry , toluene , inorganic chemistry , organic chemistry
The closo ‐[Sn 9 M(CO) 3 ] 4− ions where M=Cr ( 1 ), Mo ( 2 ), W ( 3 ) were prepared from [LM(CO) 3 ] precursors (L=mesitylene, cycloheptatriene), K 4 Sn 9 , and 2,2,2‐cryptand in ethylenediamine/toluene solvent mixtures. The [K(2,2,2‐cryptand)] + salts are very air and moisture sensitive and have been characterized by IR, 119 Sn, and 13 C NMR spectroscopy and single‐crystal X‐ray diffraction studies. Complexes 1 – 3 form bicapped square‐antiprismatic 10‐vertex 22‐electron closo structures in which the {M(CO) 3 } units occupy cluster vertices. For 1 and 2 , the clusters have C 4v symmetry in the solid state in which the {M(CO) 3 } fragments occupy capping positions with Sn 9 4− ions that are bound to the metal in an η 4 fashion. For 3 , the {M(CO) 3 } fragment occupies a position in the square plane with an η 5 ‐Sn 9 4− ion and C s point symmetry. For 1 – 3 , a dynamic equilibrium exists between the η 4 and η 5 structures yielding three 119 Sn NMR signals that reflect the three chemically distinct Sn environments of the higher symmetry C 4v structure. The 119 Sn NMR chemical shifts and coupling constants show solvent and temperature dependencies due to the equilibrium process. A triangular‐face rotation mechanism is proposed to describe the dynamic behavior.