Rhenium complex compounds

Schiff bases provide useful mixed donor sets. The carbonyl function of the most frequently used ligands is derived from either 1,3-dicarbonyl compounds or salicylaldehyde. Favourable combinations involve O-, N- and S-donor atoms. A range of technetium and rhenium complexes exist with bi-, tri-, tetra- and pentadentate ligands. The geometry of these complexes depends on the number and type of coordinating atoms as well as on the chain length between the donor atoms in the SchifF-base ligands. 

The silane o-complexes 11 have been intensively studied as discussed above and in Refs. 2, 4, and 12-14. No examples of such complexes are known for technetium, whereas the related rhenium complex [Re(H)(SiR3)(CO)2Cp] has been concluded to be classical on the grounds of a long-estimated Si-H distance of 2.2 A. Schubert favors a classical description of the latter compound, whereas Kubas noted that this distance may correspond to a stretched a-complex on the verge of oxidative... 

An unusual synthesis of a rhenium(VI) nitrido complex has been observed with the ligand reaction of the rhenium(V) precursor [ReNCl2(PPh3)2] with 2,4,6-tri-isopropylbenzenethiolate, tipt, which gave the green rhenium(VI) complex [ReN(tipt)4], when the reaction mixture was exposed to air, whereas the pale orange rhenium(V) compound [ReN(tipt)4] was obtained in an inert atmosphere. ... 

By far, the largest number of structurally characterized rhenium complexes contain the metal in the oxidation state +5 . This can be attributed to the high stability of the rhenium(V) oxo, nitrido, and imido cores with a great variety of ligand systems, but is doubtlessly also related to the fact that rhenium complexes are frequently used as nonradioactive model compounds for the development of technetium radiopharmaceuticals. The dominance of 0 , and NR ligands can be... 

Compared with the huge number of oxo complexes only a few rhenium(V) compound with terminal sulfldo complexes are known. The square-pyramidal complex anion [ReS(S4)2] was first isolated in pure form in 1986 by a reaction of Rc207 with (Ph4P)Br and ammonium polysulfide in acetonitrile and the structure of the Ph4P+ salt has been elucidated. Later, the same complex anion was prepared from starting materials such as [Re2Cl8] , perrhenate, ... 

---