New Complexes of Divalent Thulium with Substituted Phospholyl and Cyclopentadienyl Ligands

In order to try to stabilise the Tm II ion with phospholyl ligands lacking methyl groups at the 3 and 4 positions, the following ligand precursors were prepared: sodium 2,5‐di‐ tert ‐butylphospholyl [Na(Htp)] ( 3 ) and sodium 2,5‐bis(trimethylsilyl)phospholyl [Na(Hsp)] ( 8 ). Because of its similar steric bulk, we also decided to use sodium di‐ tert ‐butylcyclopentadienyl [NaCp tt ] ( 9 ) as a ligand precursor. Compound 3 was obtained by sodium cleavage of the P–P bond of 2,5,2′,5′‐tetra‐ tert‐ butyl‐1,1′‐diphosphole ( 2 ). Halogen‐lithium exchange in 1,4‐diiodo‐1,4‐bis(trimethylsilyl)buta‐1,3‐diene ( 4 ) followed by reaction with PhPCl 2 afforded 1‐phenyl‐2,5‐bis(trimethylsilyl)phosphole ( 5 ). Treatment of 5 with lithium metal followed by oxidative treatment with iodine gave 2,5,2′,5′‐tetrakis(trimethylsilyl)‐1,1′‐diphosphole ( 7 ) which could be transformed into 8 by treatment with sodium. Treatment of 3 , 8 and 9 with [TmI 2 (THF) 3 ] in diethylether yielded three new organothulium( II ) complexes [Tm(Htp) 2 (THF)] ( 10 ), [Tm(Hsp) 2 (THF)] ( 11 ) and [Tm(Cp tt ) 2 (THF)] ( 12 ), respectively, which could be isolated pure as crystalline solids in low to moderate yields. Complexes 10 , 11 and 12 were studied by X‐ray crystallography and their structures compared with those of two previously described complexes, [Tm(Cp′′) 2 (THF)] 1 [Cp = 1,3‐bis(trimethylsilyl)cyclopentadienyl] and [Tm(Dtp) 2 (THF)] ( 13 ) (Dtp = 3,4‐dimethyl‐2,5‐di‐ tert ‐butylphospholyl). Although the phospholyl ligands may be slightly more bulky than their cyclopentadienyl counterparts, the structures of 1 , 10 , 11 and 12 are remarkably similar and are substantially different from that of the more bulky 13 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)