Cobalt complexes trans effect

Britovsek GJP, Gibson VC, Kimberley BS, Mastroiarmi S, Redshaw C, Solan GA, White AJP, Williams DJ (2001) Bis(imino)pytidyl iron and cobalt complexes the effect of nitrogen substituents on ethylene oligomerization and polymerization. J Chem Soc Dalton Trans 2001(10) 1639-1644... 

Similarity with cobalt is also apparent in the affinity of Rh and iH for ammonia and amines. The kinetic inertness of the ammines of Rh has led to the use of several of them in studies of the trans effect (p. 1163) in octahedral complexes, while the ammines of Ir are so stable as to withstand boiling in aqueous alkali. Stable complexes such as [M(C204)3], [M(acac)3] and [M(CN)5] are formed by all three metals. Force constants obtained from the infrared spectra of the hexacyano complexes indicate that the M--C bond strength increases in the order Co < Rh < [r. Like cobalt, rhodium too forms bridged superoxides such as the blue, paramagnetic, fCl(py)4Rh-02-Rh(py)4Cll produced by aerial oxidation of aqueous ethanolic solutions of RhCL and pyridine.In fact it seems likely that many of the species produced by oxidation of aqueous solutions of Rh and presumed to contain the metal in higher oxidation states, are actually superoxides of Rh . ... 

H. W. Quinn and J. H. Tsai Cis and Trans Effects in Cobalt(Ill) Complexes... 

Thiocarbamate (tc, RHNCSO-) is a monodentate ambidentate ligand, and both oxygen- and sulfur-bonded forms are known for the simple pentaamminecobalt(III) complexes. These undergo redox reactions with chromium(II) ion in water via attack at the remote O or S atom of the S- and O-bound isomers respectively, with a structural trans effect suggested to direct the facile electron transfer in the former.1045 A cobalt-promoted synthesis utilizing the residual nucleophilicity of the coordinated hydroxide in [Co(NH3)5(OH)]2+ in reaction with MeNCS in (MeO)3PO solvent leads to the O-bonded monothiocarbamate, which isomerizes by an intramolecular mechanism to the S-bound isomer in water.1046... 

Cis and Trans Effects in Cobalt(III) Complexes J. M. Pratt and R. 0. Thorp... 

Electronic effects become apparent in the M—NCS/M—SCN linkage switches observed in a series of Pd11 (iso)thiocyanate complexes. Ligands positioned trans to the pseudohalide and that are suited to accept electron density from the metal into empty orbitals (backbonding) stabilize the Pd—NCS linkage isomer. However, this rationale is contradicted by the trend in Co—(NCS) bonding in a series of cobalt complexes (see ref. 204b for a review). 

CIS AND TRANS EFFECTS IN COBALT(lIl) COMPLEXES B. Infrared Spectra... 

Formation constants for other cobalt (III) complexes are very sparse. Data relevant to cis and trans effects are listed in Table VIII. Formation constants for Y/Z = HgO/HO" are the most common because of the ease of determination. Fortunately, they are very sensitive to the nature of the other ligands in the complex and can be used to study the effect of the trans ligand X (Table VTII, part A) and the cis ligands L ... 

---