Ligand isomerism in Pt(II) complexes – structural aspects

This review has focused on ligand isomers in Pt(II) complexes. There are a variety of inner coordination spheres about the platinum(II) atom (PtN4, PtN2Cl2, PtP2Cl2, PtPNC2, PtPNCl2, PtP2CBr, PtP2CS), build up by mono- and bidentate ligands. The bidentate ligands create a variety of metallocyclic rings. The L–Pt–L bite angle (mean values) open in the sequence: 73.1° (PNP) < 78.7° (NC2C) < 80.4° (NC2N) < 86.4° (PC2P) < 86.7° (PNNP) < 93.0° (CC3S). There are three types of isomers: ligand, mixed – (ligand + distortion), and mixed – (ligand + cis-trans), isomers, which are rarity.

Stereoisomers of platinum dimeric and oligomeric coordination complexes

The coordination chemistry of platinum covers a huge field as shown by a recent survey covering the structural parameter of almost 460 dimeric to oligomeric examples. Approximately 10% of these complexes exist as isomers and are summarized in this review. Included are distortion (87%) and cis-trans (13%) isomers. These are discussed in terms of the coordination about the platinum atom, and correlations are drawn among donor atom, bond distance, and interbond angles. Distortion isomers, differing by a degree of distortion in Pt-L and Pt-Pt distances and L-Pt-L angles, and some also by crystal classes, are the most common. Distortion isomers are also spread over a wider range of oxidation states of platinum [0, +1, +2 (most common), +3, +4, and even nonintegral (+2.14 and +2.375)] than cis-trans isomers (+2 and +3 only). Surprisingly, distortion isomerism is more common than the better-known cis-trans isomerism in the chemistry of platinum.

Platinum organometallic complexes: classification and analysis of crystallographic and structural data of tri- and oligomeric complexes

This review covers almost 100 organoplatinum complexes: trimers (40 examples), tetramers (40 examples), pentamers (4 examples), hexamers (5 examples), nona- and oligomers (8 examples). Platinum is predominantly found in the oxidation states +2 and +4. A number of coordination geometries are observed, the most common being essentially square planar, especially with Pt(II), and distorted octahedral, especially with Pt(IV). The most common ligands are methyl, carbonyl, PX3 and bis(diphenylphosphine)methane. Relationships between the Pt-Pt distances, Pt-X-Pt bridge angles, Pt-L bond distances and covalent radii of coordinated atoms are discussed. The mean Pt-Pt bond distance elongates in the order of nuclearity: 269.0 pm (trimers)<270.5 pm (tetramers)<271.5 pm (dimers)<278.0 pm (oligomers). A comprehensive brief discussion on over 1600 organoplatinum complexes and over 2500 platinum coordination complexes is given. These complexes prefer to crystallize in monoclinic (53%) and triclinic (27%) crystal classes. About l0% of these 4100 plus complexes exist as isomers. It is observed that these isomers are more often stereoisomers than structural isomers and that distortion isomerism is surprisingly more common than the better known cis-trans isomerism, especially in the chemistry of Pt(II) complexes.

Crystallographic and structural characterization of heterometallic platinum compounds part IV: heterotetranuclear clusters

This review includes over two hundred heterotetranuclear platinum clusters. The clusters are of the compositions Pt3M, Pt3M2, PtM3, Pt′2MM′, PtM2M′ and PtMM′M”. There are twenty five different M atoms (transition and non-transition) as a partner(s) of platinum. The four metal atoms are found in a tetrahedral, planar-rhombohedral, butterfly, spited-triangular, cubane, eight — and oligo-membered rings and a unique structures. There is wide variety of the ligands from uni to- undecadentate, with the most common P and C donor sites. The shortest Pt-M (transition) versus Pt-M (non-transition) bond distances are 2.4833(8)Å (M=Pd) vs. 2.4365(5)Å (Ge). Several relationships between the various structural parameters were found and are discussed.

Platinum organometallic compounds: classification and analysis of crystallographic and structural data of monomeric five and higher coordinated

Four hundred and twenty monomeric organoplatinum compounds, in which platinum atoms are five- and higher coordinated, are analyzed. The platinum atoms are found in the oxidation states +2, +3 and +4. The Pt(II) compounds by far prevail. There are wide varieties of the inner coordination spheres about the platinum centers. The Pt(II) compounds are five-coordinated (trigonal bipyramidal and square pyramidal), six-coordinated (different degrees of distortion), seven-coordinated (pentagonal bipyramidal, piano stool) and sandwiched (PtC10). The Pt(III) compound is square-planar. The Pt(IV) compounds are six- and eight-coordinated. There are several relationships between the Pt-L bond distances, covalent radii of the coordinated atom/ligand, and metallocycles, which are discussed. The trans-effect plays an important role in the inner coordination spheres about the Pt centers, especially on the Pt-L bond distances.

Crystallographic and structural characterization of heterometallic platinum compounds. Part II. Heterobinuclear Pt compounds with Pt⋯M (M = transition or lantanide metal) > 3.0 Å

This review covers almost two hundred and twenty heterobinuclear platinum compounds in which Pt⋯M separation is over 3.0 Å. The M is a transition metal (Cu, Ag, Au, Ti, V, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni and Pd). There is an example of a lanthanide, Yb and a actinide, U. The Pt atom has oxidation numbers 0, +2 and +4. The Pt coordination geometries include trigonal planar Pt(0); square planar Pt(II); trigonal bipyramidal, and pseudo octahedral Pt(IV), with the most frequent being square planar. The most common ligands for Pt are P and C donor atoms, as well as a chlorine atom. The Pt — Ag distance of 3.002(1) Å is the shortest found in this series. There are examples which contain two crystallographically independent molecules, which differ mostly by degree of distortion and even one unique example, which contains eight such molecules. These are examples of distortion isomerism. Factors affecting bond lengths and angles are discussed and some ambiguities in coordination polyhedral are outlined.