User:Praseodymium-141/Organopraseodymium chemistry

Organopraseodymium chemistry is the field of chemistry that studies compounds with a praseodymium-to-carbon bond. These compounds are very similar to those of the other lanthanides, as they all share an inability to undergo π backbonding. They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric. The coordination chemistry of praseodymium is largely that of the large, electropositive Pr3+ ion, and is thus largely similar to those of the other early lanthanides La3+, Ce3+, and Nd3+. For instance, like lanthanum, cerium, and neodymium, praseodymium nitrate forms both the 4:3 and 1:1 complexes with 18-crown-6, whereas the middle lanthanides from promethium to gadolinium can only form the 4:3 complex and the later lanthanides from terbium to lutetium cannot successfully coordinate to all the ligands. Such praseodymium complexes have high but uncertain coordination numbers and poorly defined stereochemistry, with exceptions resulting from exceptionally bulky ligands such as the tricoordinate [Pr{N(SiMe3)2}3]. There are also a few mixed oxides and fluorides involving praseodymium(IV), but it does not have an appreciable coordination chemistry in this oxidation state like its neighbour cerium. However, the first example of a molecular complex of praseodymium(IV) has recently been reported. Like the other organolanthanide compounds, properties of organopraseodymium compounds include:
 * Organopraseodymium compounds are very air- and water-sensitive and pyrophoric.
 * Chemistry in the 0 oxidation state is far more limited. In fact, their electropositive nature makes their organometallic compounds more likely to be ionic.
 * Organopraseodymium compounds form no stable carbonyls at room temperature; organopraseodymium carbonyl compounds have been observed only in argon matrices, and decompose when heated to 40 K.

σ-Bonded complexes
Metal-carbon σ bonds are found in alkyls of praeodymium such as [PrMe6]3− and Pr[CH(SiMe3)2]3.

π-Bonded complexes
Cyclopentadienyl complexes, are known for praseodymium. It can be produced by the following reaction scheme:
 * 3 Na[Cp] + PrCl3 → Pr[Cp]3 + 3 NaCl

These compounds are of limited use and academic interest.