Mixed Ligand Carbonyls

Mononuclear Mixed Ligand Carbonyls. The numerous and varied references which form this section will be mentioned and discussed in Periodic Table order. 

Reaction of Mo(7r-C5H5)X(CO)g with phosphorus bases normally results in loss of carbon monoxide, but when the entering group is PBu 2Ph or PBu 3 then carbon monoxide or cyclopentadienyl groups are displaced in a ratio dependent on solvent and temperature. Loss of carbon monoxide is dissociative in mechanism here. Dissociative loss, rather than the associative loss often found for M(7t-C5H5)(CO)2 compounds, can be attributed to the steric crowding around the molybdenum in the present compound.  

The mechanism of the photolytic reaction of Mn(7r-C5H5)(CO)3 with TT-interacting ligands such as indene or maleic anhydride depends on the solvent, in that in THF there appears to be a solvated intermediate Mn(7T-C6H6)(CO)2(THF), whereas in the poorer solvents n-hexane or benzene the intermediate is simply Mn(7r-C5H5)(CO)2.  

The solvent also plays a significant role in the reaction of [Fe(77-C5Hg)(CO)2]2 with iodine. In chloroform there is evidence for ionic intermediates [Fe(ir-C6H5)(CO)2]2l X there is no evidence for such an intermediate in the poorer solvent n-hexane. The product, however, is the same in both solvents—again as in the above Mn example. Rates of carbon monoxide substitution by phosphites in the closely related monomer 

Fe(7T-C5H6)X(CO)2 depend on neither nature nor concentration of the incoming ligand, which indicate a dissociative mechanism. The large, positive value of the activation entropy supports this conclusion. Displacement of carbon monoxide by a Group V base L from Co(NO)(CO)3 and from Co(NO)(CO)2L follows a two-term rate law of the form  

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Most transition metals form complexes known as carbonyls with carbon monoxide as ligands. Examples include Fe(CO)s, Fe2(CO)9, Cr(CO)6, and Rh6(CO)i6, in all of which the metal is ostensibly in the oxidation state of zero, and many mixed-ligand carbonyls such as Mn(CO)sI, CH3Mn(CO)s, and (C6H6)Mo(CO)3 are known. Such compounds have an organiclike chemistry, being essentially covalent (see Section 8.2 and Chapter 18), and the simple carbonyls such as Ni(CO)4 are volatile liquids that can be purified by fractional distillation. Of all these, however, only Ni(CO)4 (bp 43 °C) forms rapidly (and reversibly) from the elemental metal and CO gas... 

The halides participate as terminal and bridge ligands and can be included in inner and external spheres of this kind of complex. A few examples of compounds with such terminal ligands are the boron ammines [BX3 NH3], [BX2(NH3)2]X, BX(NH3)3]X2, and [B(NH3)4]X3 (X = F, Cl, Br, I). Halides form part of many mixed-ligand carbonyl complexes, for example, Fe(CO)4I2 and polyhalide anions with various elements [4], In this respect, the structure of the anion [Re2Clx]2 provides important information the Re — Re bond is present and the chlorine atoms have a bridge function [4]. 

Ruthenium, Os, Rh, Ir, Pd and Pt carbonyls, including hydrido, halogeno and mixed-ligand carbonyls, have been reviewed . Reviews also have appeared on ruthenium carbonyl halides and on carbonyl derivatives of Ti, Zr and Hf . 

Binuclear Mixed Ligand Carbonyls. Substitution in Co2(CO)6(alkyne) compounds follows the two-term rate law set out in the previous section, and proceeds by parallel dissociative and associative pathways. ... 

Mixed-ligand Carbonyls.—Further studies of the chelation reaction [(LL)M(C0)5]--------------------------[(LL)M(CO)4j + CO... 

Mixed-ligand Carbonyls.—Groups VI and VII. Continuing kinetic studies of the... 

Mixed Ligand Carbonyls.—Group VI. Photolysis of [Cr(CO)4(nbd)] in the presence of PPha gives /ra j-[Cr(CO)3PPh3(nbd)] with a quantum yield of 0.105. Kinetic data can be explained by Scheme 3 in which the primary photolysis product, which... 

Mixed Ligand Carbonyls.—General. Solvent and structural effects on reactivities of metal carbonyl halides towards carbon monoxide replacement have been probed for manganese, iron, and ruthenium compounds. The compounds were MnX(CO>5, where X == Br or I, RuX(CO)2(/i -C6H6), where X = Cl or Br, and FeX(CO)2(/i -C3H5), where X = Br or I. The displacing nucleophiles were triphenylphosphine or triphenyl phosphite the solvents were n-octane, xylene, di-n-butyl ether, or nitrobenzene. Kinetic parameters for some of these reactions, with some earlier values for related systems for comparison, are listed in Table 1. The main conclusion... 

The verification of the 18-electron rule for a mixed ligand carbonyl complex (r7 -C5H5)Fe(CO)2Cl can be carried out as follows ... 

Substitution of nickel, palladium, and platinum complexes forms part of a recent review on the kinetics of reactions of these compounds. A review up to 1971 on the chemistry of Co cyanides contains references relevant to Sections 2 [Mixed-ligand Carbonyls displacement of CO], 3, and 4 of this chapter. ... 

Mixed-ligand Carbonyls.—Grow/ VI. The kinetics of the reactions of [(P-en)Mo(CO)4] [(P-en) = ethylenediphosphine, H2PC2H4PH2] with... 

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