Cobalt compounds phosphine derivatives

Further, the 5.5-membered ring is formed by the insertion of an olefin to a tf-allyl cobalt compound. The structure of the phosphine derivative is determined by X-ray diffraction studies [36]. 

We have mentioned that the structural parameters of C2H4 bridged compounds can vary over a wide range. Whereas most examples reported do not have metal-metal bonds, there is one conspicuous exception. Theopold and Bergman succeeded in synthesizing the propane-1,3-d iyl cobalt derivative 125 from the radical anion [(t) ,-C5H5)Co(/z-CO)12 and 1,3-dibromopropane (98, 295) in 40 5 yield. This compound is best described as a dimetallacyclopentane, and its chemistry (thermolysis and reaction with CO and phosphines Scheme 34) supports this view. Formation of cyclopropane (100°C or I2/25°C) is probably the most remarkable feature of this cyclic system. Simple C—C bond formation has never been observed before in ligand-induced or thermal reactions of either mono- or binuclear cyclopentadienylcobalt complexes. The architectural details of... 

The most studied reaction involves the replacement of carbonyl groups by tertiary phosphines. This proceeds most readily in the case of cobalt derivatives, manganese compounds must usually be heated, and iron compounds require irradiation (except in the case of entry 13). 

Reaction of FeCo2(CO)9S with a series of phosphines (31, 133) and isocyanides (126) yielded mono-, di-, and trisubstituted derivatives, Eqs. (77) and (78). 57Fe-Mossbauer spectra of the phosphine-substituted derivatives indicated that substitution at cobalt occurs prior to substitution at iron (31). Unfortunately, no crystallographic evidence has been obtained for any of these derivatives, and the precise stereochemistry has not been resolved, even with the aid of l3C-NMR spectra (9). The problem is compounded with the isocyanide ligands since several isomers of the trisubstituted derivatives are formed. 

Apart from the compounds already mentioned, vanadium, manganese, and cobalt chlorides, tetra-alkoxy derivatives of titanium, acetylacetonates of V, Cr, Mo, Mn, and Ni, Cp derivatives of Zr and Nb, and triphenyl phosphine complexes of Ti and Fe were found to be active. Later lanthanide complexes were included in the list of dinitrogen-reducing systems, the most effective being compounds of samarium and yttrium. 

The phosphine combines with cobalt(II) dihalides to give the 5-coordinate derivatives, LXXVIII, but these do not undergo ionization in organic solvents. Rhodium (III) trihalides give normal 6-coordinate compounds, LXXIX, whereas sodium hexachloroiridate(IV), Na2lrCl6,... 

Mixed phosphite ester-phosphine coordinated acylcobalt carbonyl derivatives have also been prepared. Methyl(triphenylphosphine)cobalt tricarbonyl, which cannot be produced by a simple ligand replacement reaction, can be obtained by another method. Hieber and Lindner (21) found that bis(triphenylphosphine)dicobalt hexacarbonyl reacts with sodium amalgam to form sodium(triphenylphosphine)cobalt tricarbonyl and that this compound reacted with methyl iodide to form methyl-(triphenylphosphine)cobalt tricarbonyl. 

The mercury compound Hg[Co(CO)4]2 appears to be the most stable of these metal cobalt tetracarbonyl derivatives, especially with respect to air oxidation. It reacts with the phosphines R3P (R = phenyl, cyclohexyl, or ethyl) at room temperature to form the yellow, sparingly soluble solids Hg[Co(CO)3PR3]2 26). The phenyl derivative may also be obtained from Na[Co(CO)3P(C6Hs)3] and an appropriate mercury derivative. Treatment of Hg[Co(CO)4]2 with pyridine liberates free mercury to form the salt [Co(py)d[Co(CO)4]2(26)... 

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