Pentamethylcyclopentadienylrhodium complexes with the pyridazine ligand. Molecular structure of [{Rh(C5Me5)}2(µ-Cl)2(µ-pydz)][ClO4]2·H2O (pydz = pyridazine)

Abstract

The preparation and characterization of the new mononuclear complexes [Rh(C₅Me₅)Cl₂(pydz)], [Rh(C₅Me₅)Cl(pydz)₂][X], and [Rh(C₅Me₅)(acac)(pydz)][X](pydz = pyridazine, X = BF₄ or ClO₄, acac = acetylacetonate) are reported. The mononuclear complex [Rh(C₅Me₅)Cl₂(pydz)] reacts with the solvated species [Rh(C₅Me₅)L₃][X]₂(L = acetone) to form [{Rh(C₅Me₅)}₂(µ-Cl)₂(µ-pydz)][X]₂. The structure of the latter complex (X = ClO₄) has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P2₁/n with Z= 4 in a unit cell of dimensions a= 22.2761(9), b= 7.940 7(1), c= 19.359 5(8)Å, and β= 109.824(3)°. The structure was solved by Patterson analysis and refined by full-matrix least-squares methods to R= 0.047 for 3 970 observed reflections. The cation consists of two Rh(C₅Me₅) moieties triply bridged by two chlorine atoms and a pyridazine group. The latter co-ordinates in an exo-bidentate manner through the two nitrogen atoms. The two rhodium atoms are separated by 3.397(1)Å. Attempts to isolate homovalent double-bridged complexes of general formula [Rh₂(C₅Me₅)₂Cl₂(pydz)₂]²⁺ or mixed-valence rhodium(III)-rhodium(I) complexes of formulae [(C₅Me₅)ClRh(µ-Cl)(µ-pydz)Rh(tfb)]⁺ or [(C₅Me₅)ClRh(µ-pydz)₂Rh(tfb)]²⁺(tfb = 5,6,7,8-tetrafluoro-1,4-dihydro-1,4-ethenonaphthalene) have been unsuccessful.