Cobalt tetrakis anion

The organic solvent should feature a low solubility in water and a high dielectric constant. Numerous studies have been reported for liquid-liquid junctions involving DCE [43,62,70,71,73], nitrobenzene [67,68,74,75], and nitrophenyloctylether (NPOE) [56]. Various hydrophobic electrolytes have been employed in these solvents. Tetraphenylarsonium (TPAs+) [[71,75,76], bis-triphenylphosphoranylidene (BTPPA+) [43,50], and hydrophobic tetra-arylammonium [77,78] are among the cations used in the organic phase. The choice for anions has been mostly restricted to borate derivatives, tetraphenylborate (TPB ) [70,79,80], tetrakis(4-chlorophenyl)borate (TPBCH) [43,81,82], and tetrakis(penta-fluoro)phenylborate (TPFB ) [49,83], as well as dicarbollyl-cobaltate [75]. 

The reduction of tetrakis-(4-iV-methylpyridyl)porphinecobalt(iii) by Ru(NH3)6 has been studied as a function of pH and added anions it was found that the rate was influenced most when NCS or N3 ions are bonded directly to the cobalt site. ... 

The CoNMR spectra of the tetrahedral [Co(PF3)4] and [Co(CO)4] anions have been recorded (191) and values obtained for the V( Co- P) (1222 25 Hz) and V( Co- C) (287 13 Hz) coupling constants. Approximate values for the cr-bond order were calculated and together with shift data suggested that bonding to the ligand tt orbitals is more important in the carbonylate ion than bonding to the phosphorus 3d orbitals of the tetrakis(trifluorophosphine)cobaltate, and that the cobalt-phosphorus u-bond order apparently is greater than the cobalt-carbon c7-bond order (191). 

Because A is small, low-spin tetrahedral complexes are rare. The first such complex of a first row transition metal, tetrakis(l-norbomyl)cobalt (1-norbomyl is an organic ligand, C7H11), containing a low-spin Co(IV) center, was reported in 1986 (Figure 10.27). The corresponding anionic Co(III) ([Co(l-nor)4] ) and cationic d Co(V) ([Co(l-nor)4] ) low-spin tetrahedral complexes were also prepared. Another organometallic complex, lr(Mes)4 (Mes = 2,4,6-trimethylphenyl), is approximately tetrahedral and features a low spin d Ir(lV) center. " ... 

R. Hammer and H.F. Klein, The tetrakis(triphosphine)cobalt anion. 

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