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Published on: March 19, 2020
Tetra-ethyl-ammonium (2,2'-bipyridine)tetra-cyanidocobaltate(III) sesquihydrate acetonitrile solvate
Abstract:
The title complex, (C(8)H(20)N)[Co(CN)(4)(C(10)H(8)N(2))]·CH(3)CN·1.5H(2)O, consists of tetra-ethyl ammonium cations, mononuclear [Co(III)bpy(CN)(4)](-) anions and uncoordinated water and acetonitrile mol-ecules. The Co(III) atom is six-coordinated by two 2,2'-bipyridine (bpy) N atoms and four cyanide C atoms in a distorted octa-hedral geometry. The acute bite angle of the chelating bpy [82.28 (8)°] is the main factor accounting for this distortion. In addition, the tetra-ethyl-ammonium cation is significantly disordered [occupancy ratio 0.611 (3):0.389 (3)]. The presence of water mol-ecules, one of which is disordered over two positions about an inversion center, results in the formation of a network of O-H⋯N hydrogen bonds involving the cyanide N atoms.
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Acidity of 1-Alkynes
The acidic strength of hydrocarbons follows the order: Alkynes > Alkenes > Alkanes. The strength of an acid is commonly expressed in units of pKa — the lower the pKa, the stronger the acid. Among the hydrocarbons, terminal alkynes have lower pKa values and are, therefore, more acidic. For example, the pKa values for ethane, ethene, and acetylene are 51, 44, and 25, respectively, as shown here.
Coordination Compounds and Nomenclature

