Tl(I) complexes of cymantrene-based tris(1-pyrazolyl) borates: polymers and macrocycles

Cymantrene-based tris(1-pyrazolyl) borates have been synthesised from the reaction of CymBBr(2) and Cym'BBr2 with pyrazole (Hpz) in the presence of triethylamine [Cym: cymantrenyl; Cym': (methyl) cymantrenyl]. The Tl(I) salts CymB(pz)(3)Tl, 2a, and Cym'B(pz)(3)Tl, 2b, have been structurally characterised by X-ray crystallography. Similar to the corresponding complex FcB(pz)(3)Tl (Fc: ferrocenyl), CymB(pz)(3)Tl features a polymeric structure with bridging [B(pz)(3)] fragments in the solid state. Cym'B(pz)(3)Tl shows a related oligomeric structure. This time a macrocyclic tetramer rather than a linear chain is observed. To provide a ligand of high solubility in non-polar solvents, compound Cym'B(pz(4-R))(3)Tl, [R = CH2(C6H11)] 2d, has been synthesised, which shows a reduced symmetry at the organometallic moiety, together with (cyclohexyl) methyl substituents in the 4-positions of all pyrazolyl rings.