The ¹²⁵Te NMR spectrum of [Me₄N][TeF₇] (298K in MeCN) consists of a binomial octet (J = 2876 Hz), while the ¹⁹F NMR spectrum exhibits a singlet with two (superimposed over the singlet), very low intensity doublets (J = 2876 and 2385 Hz respectively). Rationalize these observations. [Data: see Table 16.1; 19F, 100%, I =1/2.]

Table 16.1

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Property Atomic number, Z Ground state electronic configuration Enthalpy of atomization, A,H°(298 K)/kJ mol-¹ 249: Melting point, mp/K Boiling point, bp/K Standard enthalpy of fusion, AfusH" (mp)/kJ mol First ionization energy, IE₁/kJ mol-¹ AEAH1 (298 K)/kJ mol™¹** AEAH2(298 K)/kJ mol-¹** Covalent radius, cov/pm Ionic radius, 'ion for X² /pm Pauling electronegativity, XP 3.4 NMR active nuclei (% abundance, nuclear spin) 0 (0.04, 1=) ³S (0.76,1=3) "Se (7.6,1=1) ¹2³ Te (0.9,1 =3) 125 Te (7.0, 1 =) 8 [He]2s²2p¹ 54 90 0.44 1314 -141 +798 73 S 140 16 [Ne]3s²3p* 277 388 718 1.72 999.6 -201 +640 103 184 Se 2.6 34 227 [Ar]3d¹04s²4p [Kr]4d¹⁰5x²5p² 494 958 6.69 941.0 -195 117 Te 198 2.6 52 197 725 1263* 17.49 869.3 - 190 135 211 2.1 Po 84 [Xe]4f3%5d06s*6p* 146 527 1235 812.1 -183 2.0