Syntheses of Pyrazolato‐ and Formamidinato‐lanthanoid(III) Diiodides from <i>in Situ</i> Generated lanthanoid(III) Pseudo‐Grignard Reagents

Abstract Trivalent lanthanoid pseudo‐Grignard reagents Ph p Ln III I (3‐p) (P=1 or 2; Ln=La, Ce, Nd, Er and Lu) are readily prepared by the oxidation of lanthanoid metals with iodobenzene at 25 °C, following pre‐activation of the metal with 1 drop Hg in tetrahydrofuran (thf) or acetonitrile (CH 3 CN) and brief sonication. The protolysis of Ph p Ln III I (3‐p) with 3,5‐diphenylpyrazole (Ph 2 pzH) yields pyrazolato complexes [Ln(Ph 2 pz)I 2 (thf) n ] (n=4: Ln=La 1 , Ce 2 , Nd 3 ; n=3: Ln=Er 4 , Lu 5 ). Interestingly, for Er, a competing complex [ErPh(Ph 2 pz)I(thf) 3 ]⋅thf ( 4 a ) was obtained along with the expected [Er(Ph 2 pz)I 2 (thf) 3 ] ( 4 ). In contrast, in CH 3 CN, [Ln(Ph 2 pz) 3 (CH 3 CN) 3 ]⋅2CH 3 CN (Ln=Nd 6 , Gd 7 ) complexes were obtained through Schlenk equilibrium redistribution. Reactions with bulky N,N′ ‐bis(2,6‐di‐ iso propylphenyl)formamidine (DippFormH) and N,N’ –bis(2,6‐dimethylphenyl)formamidine (XylFormH) produced the Ln (III) complexes, [Ln(DippForm)I 2 (thf) 3 ]⋅nthf (n=1, Ln=Nd 8 ; n=0.5, Ln=Er 9 ) and [Ln(XylForm)I 2 (thf) 3 ]⋅thf (Ln=Nd 10 , Er 11 ). All the complexes isolated in this study are monomeric; 4 – 5 and 8 – 11 are seven coordinate, complexes 1 – 3 are eight coordinate with one η 2 ‐N‐donor ligand and two trans iodine ligands, and complexes 6 – 7 are nine coordinate, featuring three η 2 ‐Ph 2 pz ligands, and three CH 3 CN ligands.