Cluster chemistry coordination polymers

SBU Secondary building unit in the context of coordination polymer network synthesis (reticular chemistry) refers to the geometry of metal coordination cluster fragments units as defined by the points of extension (such as the carboxylate C atoms in most carboxylate MOFs). 

Solvent free methods have been used extensively in supramolecular chemistry, coordination chemistry and the formation of transition metal clusters and polymers. Reactions range from very simple ligand substitution reactions for salts of labile metal ions to more complex procedures, some of which are outlined below. 

The use of metal-ligand coordination in preparing supramolecular assemblies represents one of the major themes of materials chemistry over recent years. Notable achievements have been made in both the assembly of discrete clusters in solution and extended coordination polymers in the solid state,including metal organic frameworks (MOFs). The assembly of coordination polymers on surfaces is far less studied and, it would appear, more synthetically challenging. However, some notable studies have been reported both at the solid-solution interface and under UHV conditions. 

Two kinds of salen-type Schiff-base ligands, conjugated and flexible, have been used in the synthesis of polynuclear lanthanide complexes and lanthanide coordination polymers Lanthanides Coordination Chemistry, Rare Earth Metal Cluster Complexes. The stoichiometry and structures of these complexes are dependent on the Schiff-base... 

Thus, the stmctural chemistry of reduced rare-earth metal cluster complexes may be described in a way similar to silicates—where [SiOJ tetrahe-dra share common vertices—or like (anti-)Werner complexes that are either monomers, oligomers, or developed into coordination polymers of various dimensionalities. 

The spacer units in 3.60 are assembled from polyphosphazenes that bear p-bromophc-noxy side groups via a lithiation reaction, and treatment with a diorganochlorophosphine to give 3.62. The chemistry is summarized in reaction sequence (45).107 Polymer 3.62 coordinates to a variety of metallo species,108 including osmium cluster compounds and cobalt carbonyl hydroformylation catalysts. When used as a polymeric hydroformylation catalyst, this latter species proved how stable the polyphosphazene backbone is under the drastic conditions often needed for these types of reactions. The weakest bonds in the molecule proved to be those between the phosphine phosphorus atoms and the aromatic spacer groups. 

Abstraction, reductive coupling, electron transfer, bond activation, oxidative addition, n-complexation, disproportionation and metal cluster formation are some of the reactions that occur when metal atoms interact with organic polymers and small molecules. Examples of these reactions are provided from the literature on the organometallic chemistry of free atoms and coordination-deficient molecules. Past uses of model compound studies to understand the early stages of chromium metallization on polyimide are critiqued. New evidence for reactions of chromium atoms with compounds related to polyimides is given. 

---