Volume 34, Issue 1

This is a review of publications concerning the results of X-ray analysis of single crystals and spectrochemical characteristics of metal complexes containing polyoxo-carbocyclic compounds with one or more neighboring oxo-groups. The features of lattice characteristics and coordination modes, depending on the nature of the organic dianion, are shown here. The squarate anions, C4O42-${{\rm{C}}_{\rm{4}}}{\rm{O}}_{\rm{4}}^{{\rm{2 - }}}$ are predominantly involved in monodentate bridging coordination, and the derivatives containing five or six C-atoms in the cycle (croconate and rhodizonate anions) usually form bidentate chelating bridged modes. The stabilization of the crystal lattices of the metal complexes is due to the formation of hydrogen bonds and π-π stackings, which produce self-assembled three-dimensional (3D) structures with cavities and intercalation of some small molecules. The strong interlayer interactions lead to appearance of specific conductometric and magnetic properties, which together with their high thermal stabilities, make the oxocarbon complexes new and perspective materials for electronics and related areas.

This review covers over 260 examples of dimeric organoplatinum complexes. Platinum is predominantly found in the oxidation states +2 and +4, but with some examples of 0, +1, +2.5, +3, and of mixed-valence as well. A number of coordination state geometries are observed, of which the most common is essentially square-planar at Pt(II), a distorted octahedral at Pt(IV), and some examples of trigonal planar and trigonal bipyramidal as well. The most common ligands are methyl (Me), carbonyl and PX 3 . The shortest Pt-Pt bond distance is 245.1(1) pm. The mean Pt-Pt bond distance increases in the order: 261.1 pm [Pt(2.5)-Pt(2.5)]<261.3 pm [Pt(III)-Pt(III)]<262.4 pm [Pt(I)-Pt(I)]<270.3 pm [Ot(II)-Pt(II)]<277.2 pm [Pt(0)-Pt(0)]<282.6 pm [Pt(II)-Pt(II)]. The Pt…Pt no-bonding distances are: Pt(II)…Pt(II), 3.008–17.959 pm; Pt(IV)…Pt(IV), 327.5–768.0 pm; Pt(II)-Pt(0), 378.6 pm and Pt(II)…Pt(IV), 389 pm. There are several relationships pointed out between the Pt-Pt distances, Pt-X-Pt bridge angles and covalent radii of coordinated atoms. Several examples contain two crystallographically independent molecules within the same crystal, differing mostly by degree of distortion, which are examples of distortion isomerism.