The Infrared Spectra of Some Thiocyanatocobalt Ammines

Abstract

Vol. 81 the dissociative path is probably very rapid even in alkaline solution a t 0" and, further, that a bimolecular path is expected to be important because of the possibility of forming a transition state by attachment of an ethylenediamine molecule in an axial position. Thus, bimolecular exchange may occur through rapid formation and dissociation of the tris complex, in spite of its low thermodynamic stability constant . I 3 Bjerrum and Nielsen suggested that the third ethylenediamine molecule in the tris complex is monodentate and that copper(I1) has coordination number 5 in the complex. Although such a structure may be involved as an initial step in the reaction, it cannot be the only form of the tris complex. If proton exchange results reported in this paper are indeed explained by the biinolecular exchange of ethylenediamine, it is necessary that the ethylenediamine ligands be equivalent in soiiie intermediate or transition state, (13) J. Rjerrum and R J. Xielsen, Acto Chem. Scand., 2, 297 (1948). most probably one having nearly octahedral symmetry. It should be noted that the bimolecular exchange rate constant expressed in terms of ethylenediamine exchange is because there are four exchangeable protons in each ethylenediamine molecule.The observed activation energy, 4.5 kcal./mole, is abnormally low for unimolecular (or pseudo-unimolecular) dissociation of a transition metalethylenediamine chelate. However, it is quite reasonable for an "associative" reaction Cu(en)2(H20)2++ + en + Cu(en)s++ + 2H20 If that reaction involves the rate-determining step in proton exchange, the ensuing "dissociation" Cu(en)d*+ 4-2H20 ---t Cu(en)z(H?0)2++ + en (15) iiiust be rapid, in spite of an anticipated high activation energy, because of a large entropy of activation..Ivs~rv, TEXAS kenf =i ka'/4 (13)

Thermal treatment of a modified alkoxide gel precursor for the preparation of the YBa2Cu4O8 superconductor

“…3a) contain typical absorptions of alkyl- 1 H20, NH3 gas (968 and 932 cm- [10,11]) and a considerable amount of CO2 (3750-3600 cm -1, 2400-2300 cm -1 [12] and 618-721 cm -1 [13]) are detected as well. This mass loss is mainly attributed to the evaporation of the solvent butoxyethanol which explains the observed alkyl, alkohol and ether absorptions.…”

Preparation and Properties of trans-[CoCl2(tmd>)2]Cl, and trans- and cis-[Co(NCS)2(tmd)2]NO3 (tmd: Tetramethylenediamine)

“…The infrared spectra of the CN stretching region has been applied to distinguish the geometrical isomers of [Co(NCS) 2 (en) 2 ]Cl Á H 2 O, i.e., the trans isomer exhibits one band at 2136 cm À1 , while the cis one has two bands at 2122 and 2110 cm À1 [15]. The infrared and Raman spectra of isomers 1 and 2 in the solid state are shown in Fig.…”

Variations with bond types of the yields for deuterium-atom abstraction by 2.8-ev. tritium atoms

“…Much less extensive work has established that the abstraction of deuterium from C-D by tritium atoms from nuclear recoil fits readily into a pattern of variation quite similar to that found for C-H. [1][2][3][4] (11) C. C. Chou and F. S . Much less extensive work has established that the abstraction of deuterium from C-D by tritium atoms from nuclear recoil fits readily into a pattern of variation quite similar to that found for C-H. [1][2][3][4] (11) C. C. Chou and F. S .…”

“…[1][2][3][4] Subsequent experiments T* + R H --f HT + R (1) have confirmed the general concept of substantial variations in HT yield with C-H bond type, while demonstrating that the bond dissociation energy correlation must be modified in some cases by allowances for the internal excitation of the residual radical, R.5*6 Explanations of two general types have been offered to account for the observed sensitivity of HT yield to the nature of the C-H bond, differing most critically in their estimates of the kinetic energy of the reacting tritium atom. [1][2][3][4] Subsequent experiments T* + R H --f HT + R (1) have confirmed the general concept of substantial variations in HT yield with C-H bond type, while demonstrating that the bond dissociation energy correlation must be modified in some cases by allowances for the internal excitation of the residual radical, R.5*6 Explanations of two general types have been offered to account for the observed sensitivity of HT yield to the nature of the C-H bond, differing most critically in their estimates of the kinetic energy of the reacting tritium atom.…”