Transition metal pyridine complexes

Many variants of pyridine are also known to coordinate to metal ions, such as the methylpyridines, quinolines, and more complex rings.

Trends in the M-N distances for complexes of the type [MCl2(py)4]2+ reveal an anticorrelation with d-electron count.

With respect to HSAB theory, it is intermediate softness, reflecting its small but significant properties as a pi-acceptor ligand.

Owing to the relatively wide C-N-C angle, the 2,6-hydrogen atoms interfere with the formation of [M(py)6]z complexes.

The tris(pyridine) trihalides, i.e., [MCl3(py)3] (M = Ti, Cr, Rh[19] Ir), are another large class of M-Cl-py complexes.

[27] Ni(ClO4)2(3-picoline)2 can be isolated in two isomers, yellow, diamagnetic square planar or blue, paramagnetic tetrahedral.

[30][27] The η6 coordination mode, as occurs in η6 benzene complexes, is observed only in sterically encumbered derivatives that block the nitrogen center.

Although transition metal pyridine complexes have few practical applications, they are widely used synthetic precursors.

Many are anhydrous, soluble in nonpolar solvents, and susceptible to alkylation by organolithium and Grignard reagents.