| Abstract
| - The199Hg shielding anisotropy and asymmetry parametersΔσ and η have been determined from the solid-state199Hg MAS NMR spectra of several mercury(II)thiocyanate complexes and related compounds. The effects ofchanges in the mercury coordination number, distortions of thecoordination environment, and secondary bonding interactions on theshielding parameters are interpreted in terms of variations in thelocal paramagneticcontribution.
- The solid-state 199Hg MAS NMR spectra of[Hg(SCN)2], [Hg(SeCN)2],M[Hg(SCN)3],M2[Hg(SCN)4] (M = K,Cs), and K2[Hg3(NCO)8]have been measured, and the (monoclinic) crystal structure of[Hg(SeCN)2] has beendetermined to assist in the interpretation of the NMR data. Theasymmetric unit of Hg(SeCN)2 contains onemolecule at an inversion center which shows linear Se−Hg−Se bonding(Hg−Se = 2.4738(10) Å, Se−Hg−Se= 180°, Hg−Se−C = 97.5(3)°). Secondary Hg---Seand Hg---N contacts are 3.4246(9) and 2.835(12)Å,respectively; this arrangement differs from that inHg(SCN)2 where there are no secondary Hg---S contacts.Aredetermination of the monoclinic crystal structure ofK[Hg(SCN)3] is also reported, revealing substantialdifferencesfrom the earlier work. Spinning sideband analysis has been used todetermine the 199Hg shielding anisotropyandasymmetry parameters Δσ and η from the solid-state199Hg MAS NMR spectra. The effects of changes inthemercury coordination number and of distortion of the coordinationenvironment on the shielding parameters areinterpreted in terms of changes in the local paramagnetic contribution.The same method is employed to assessthe effects of secondary bonding on shielding, and it is shown that thesubstantial differences between the valuesfor Hg(SCN)2 and Hg(SeCN)2 can beattributed to these effects. The ν(HgS) modes have beenassigned in theIR and Raman spectra of the thiocyanate complexes, and the correlationbetween the wavenumbers and splittingsof these bands and the 199Hg shielding parameters isdiscussed.
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