On the estimation of the field constant of 35Cl nuclear quadrupole resonance frequency in the series of [R1R2R3AsCl]+M− compounds

Abstract

The field constant of the NQR frequency of a chlorine atom ( 35 Cl) in a series of arsenic derivatives [R 1 R 2 R 3 AsCl] + M -was estimated from correlations. The field frequency is ∼41.5±3.5 Hz cm kV -1 , which is nearly twice as much as that in analogous phosphorus com pounds.It is known 1 that the field constant of the NQR fre quency dν/dE z of a chlorine atom (E z is the electrostatic field intensity along the axis of the A-Cl bond) is highly characteristic and is determined only by the nature and state of a partner atom. This parameter is independent of the nature and number of substituents in the molecule for the given type of the bond. The field constant character izes the polarizability of a resonance atom and enables one to estimate the easiness of the electron density redis tribution under the field effect. Previously, 2 the field con stants of NQR frequencies of a chlorine atom bound to the tetracoordinate phosphorus atom in a series of acid chlorides of oxygen, thio, and selenium acids of penta valent phosphorus and in ionic compounds of the [R 1 R 2 R 3 PCl] + M -type have been estimated using the correlations. The isoelectronic series R 1 R 2 P(O)Cl and R 1 R 2 R 3 SiCl were used as references for comparison. 2 It turned out that dν/dE z for compounds of the mentioned series changes as follows: P(O)Cl ≈ (RO)P(S)Cl > P(S)Cl > P(Se)Cl > PCl ion .The experimental data given in Table 1 and Fig. 1 made it possible to perform similar estimations for a series of chlorine derivatives of arsenic [R 1 R 2 R 3 AsCl] + M -. If the linear correlation ν As-Cl = ν 0 + kν A-Cl obeys, then its differentiation with respect to the electric field intensity E z gives a correlation of the type dν As-Cl /dE z = kdν A-Cl /dE z .(1)When the field constant dν A-Cl /dE z is known, then the desired field can easily be estimated using the k coeffi cient. We used similar dependences for the ionic forms of the arsenic derivatives [R 1 R 2 R 3 AsCl] + M -and an R 1 R 2 R 3 GeCl series (see Fig.