The Crystal and Molecular Structure of the Trinuclear Complex Bis[(μ-S)-α,α′-{(2-mercapto-5-methylbenzene-1,3-diyl)di(methylidyne)di(azino)}bis(cyclohexane-methanol)ato(3-)]tripalladium(II), L₂Pd₃. A New Coordination Mode for the Robson-Type Ligand L^3-

Abstract

The crystal and molecular structure of the trinuclear complex L₂Pd₃ has been determined by single-crystal X-ray diffraction techniques at room temperatures, 20°C. The quinquedentate binucleating ligand, L^3-, is formally the trianion α,α′-[(2-mercapto-5-methylbenzene-1,3-diyl )di(methylidyne)di(azino)]bis(cyclohexaemethano)ato(3-). Crystals of L₂Pd₃ are triclinic, PI, with a 11.896(1), b 13.4103(7), c 17.451(3) Å , α 75.66(1), β 79.93(1) and γ88.99(1)º, Z 2.

The structure was solved by the normal Fourier methods and refined by a least-squares procedure which gave final R and R, values of 0.046 and 0.049 respectively for the 7769 statistically significant reflections. The approximately square-planar coordination environments of the palladium centres give rise to a boat-shaped arrangement in which an approximate, non-crystallographic, twofold axis normal to the plane of the central metal is evident. The notable feature of the structure lies in the novel coordination mode adopted by the binucleating ligand. With respect to the binuclear complexes of this ligand, an electronic reorganization has occurred in one of the sidearms of both ligands which enables the formation of the pair of hydrazine bridges and also causes two of the terminal oxygen groups to become non-coordinating.