The Tl-F and Tl-Tl bonding in alpha-TlF and beta-TlF have been studied
from Tl-203,Tl-205 and F-19 NMR powder data. The off-ionic part of th
e Tl-Tl and Tl-F interactions is characterized by indirect spin-spin c
oupling Tl-203-Tl-205, Tl-205-F-19 and thallium and fluorine nuclear m
agnetic shielding tensors. It is shown that structure distortions of a
lpha-TlF and beta-TlF are connected with a thallium 6s(2) inert pair a
ctivation and with a Tl-Tl interaction of previously unnoted type.