Chemistry of Rh(I) complexes based on mesogenic 3,5-disubstituted pyrazole ligands. X-ray crystal structures of 3,5-di(4-n-butoxyphenyl)pyrazole (Hpzbp2) and [Rh(μ-pzR2)(CO)2]2 (R=C6H4OCnH2n+1, n=10, 12) compounds. Part II

Four new 3,5-disubstituted pyrazoles HpzR2 containing long-chain 4-n-alkyloxyphenyl substituents [R=C6H4OCnH2n+1; n=4 (1), 6 (2), 12 (5), 14 (6)] have been prepared and characterised. All of them showed mesomorphic behaviour, the stability and the range of the mesophases increasing with the length of the chain on the pyrazole. The X-ray structure of Hpzbp2 (1) showed a highly linear molecular shape. Related results were deduced for the remained HpzR2 and the structural consequences agree with the observed mesomorphic properties. The mesogenic pyrazoles HpzR2 (1–6) were used as ligands towards [RhCl(CO)2] and [Rh(CO)2] fragments. [RhCl(CO)2(HpzR2)] complexes (7–12) showed some physical properties dependant on the long-chained pyrazoles, and related to different molecular arrays in the solid state. In all cases these compounds evolved to [Rh(μ-pzR2)(CO)2]2 in solution. The pyrazolate Rh(I) complexes [Rh(μ-pzR2)(CO)2]2 (13–18) had the usual boat conformation, as deduced by the crystal structure of two of these derivatives [n=10 (16), 12 (17)]. The packing arrangement has both layer and columnar characteristics. No mesophases have been detected for any of the Rh(I) complexes.