7 Li, 31 P, and 1 H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh 3 ), Fluorenyllithium, and Li[N(SiMe 3 ) 2 ] amongst Other Salts

7 Li, 31 P, and 1 H variable‐temperature pulsed gradient spin‐echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium ( 2 ) and fluorenyllithium ( 9 ), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2‐lithio‐1,3‐dithiane ( 13 ) and lithium hexamethyldisilazane (LiHMDS 16 ), low‐temperature data show that the ions remain together. For the dithio anion 13 , a mononuclear species has been established, whereas for the lithium amide 16 , the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7 Li PGSE data show that all three salts can be described as well‐separated ions at ambient temperature. The solid state structure of trityllithium ( 2 ) is described and reveals a solvent‐separated ion pair formed by a [Li(thf) 4 ] + ion and a bare triphenylmethide anion.