Pnictogen anions

The most widespread complexes of cyclic pnictogen anions are those containing the planar six 71-electron ligand cyclo-Ps (isovalent with [CsHs] ). The potassium salt of this anion is obtained in solution by the reaction of red phosphorus with KPH2 in boiling DMF " this reagent can be used for the direct synthesis of tj -Ps complexes of metal carbonyls [eqns (11.2a) (M = Cr, Mo, W) and (11.2b)]. " An intriguing example of... 

The nucleophilic carbene (112) has been shown to react with pnicogen pentafluorides (113a-c) to form adducts (114ac) with octahedral geometry at P (P N = 1.898 A), As (As-N = 1.999 A) and Sb (Sb-N = 2.175 A). The structures are therefore those of internal zwitterions with an imidazolium cation and a pnictogen anion. The strong nature of the bonds to the carbene... 

Solid-state assemblies containing binary group 15/16 anions of the heavier pnictogens are also extremely well known, including the naturally occurring... 

Binary Anions and Cations. The heavy pnictogens in combination with chalcogens form a large variety of anions.Although many of these binary species form oligomers or polymers with layered or framework structures, there are a number of examples of discrete anions with cyclic structures that are formed with large counterions such as tetralkylammonium or tetraarylphosphonium... 

Discrete molecules of dimeric (TMEDA)sodium tetraethylarsolide in the solid state are found with the sodium atoms bound in an 77 -manner to one arsolide anion and having an Na-As c-bond to the other. Furthermore, the coordination sphere of the sodium atom contains a bidentate TMEDA molecule. The molecular structure resembles the structure of the homologous phospholide. The heavier 2,3,4,5-tetraethylstibolide 11b (M = Na) shows a totally different arrangement of the ions in the solid state. A chain structure is formed due the larger pnictogen atom. Besides the 77 -coordination of the stibolide ligands, discrete Na-Sb bonds are also observed <20040M3417>. 

The lowest oxidation state, -3, having a ns np electron configuration, is found in transition metal complexes of ligand-free Pn anions. When a single Pn ion is attached to a metal, they are collectively referred to as pnictido ligands and form terminal metal-pnictogen triple bonds, which are known for all group 15 elements except bismuth. ... 

The loss of an electron at a pnictogen atom may be compensated by two different bonding mechanisms. In the case of a phosphorus derivative (Pn = P M = Al), the electronic balance is accomplished by intramolecular backbonding from the neighboring nitrogen atoms. On the other hand, the antimony and bismuth derivatives (Pn = Sb, Bi M = Al) involve the inter-molecular coordination of a chlorine atom of the AICI4 anion with the unsaturated pnictogen atom. 

---