Metal Carbonyls Cations

Lupinetti, A.J., Jonas, V., Thiel, W., Strauss, S.H. and Frenking, G. (1999) Trends in Molecular Geometries and Bond Strengths of the Homoleptic d Metal Carbonyl Cations [M(CO)J ... 

These observations illustrate that there are two transformations open to metallocarboxylic acid intermediates reversible loss of OH" accompanied by oxygen exchange, and metal-hydride formation with expulsion of C02. Our entry into this area of chemistry was in 1975 when extensive studies of oxygen lability in metal carbonyl cations were initiated (10). These... 

Figure 2. Synthesis of starting metal carbonyl cations...

Alkenes and Alkynes. A series of metal carbonyl cations, such as [Au(CO)n]+,287,288 [c-Pd( i-CO)2]2+,289 [Rh(CO)4]+,290 and [(Pt(CO)3)2]2+,291 was found to induce the formation of carboxylic acids from alkenes and CO in the presence of H2SO4 under mild conditions. A novel water-soluble Pd catalyst292 and Pd complexes of calixarene-based phosphine ligands293 showed high activity in the regioselective carboxylation of vinyl arenes to yield 2-arylpropionic acids or... 

With the exception of 46 and 47 [Eqs. (12) and (13), the other neutral formyls in Table II have been prepared by hydride attack on metal carbonyl cation precursors. The most extensively studied of these have been (i7-C5H5)Re(NO)(CO)(CHO) (38) and (T7-C5H5)Re(NO)(PPh3)(CHO) (39). The former was reported approximately simultaneously by Casey (56), Gladysz (57), and Graham (5Conditions employed for its preparation are summarized in Eq. (10). Formyl 38 can be obtained as a solid, but the... 

Formyl transfers" involving neutral formyl complexes, such as shown in Eq. (22), have recently been reported (68). By precipitation of the metal carbonyl cation by-product, quite pure solutions of kinetically labile neutral formyl complexes may be obtained. 

Metal Atom Synthesis of Organometallic Compounds, IS, 53 Metal Carbonyl Cations, 8, 117... 

CATIONS OF GROUP 6-12 ELEMENTS 4.5.1. Homoleptic Metal Carbonyl Cations... 

Versatile synthetic routes are available to prepare metal carbonyl cations in superacidic media. The most successful methods include reductive carbonylation of metal fluorosulfates or fluorides [Eqs. (4.237)1003 and (4.238)1004]-1002 1005 This... 

The use of a Lewis acid to promote the abstraction of a halide anion from a metal halide complex, in the presence of a neutral ligand, has been widely employed to produce both substituted and totally unsubstituted metal carbonyl cations. The halide acceptor most generally used is aluminum trichloride, but other Lewis acids have been employed, as indicated below. The requirements for the halide acceptor include that the anion product should be sufficiently large to stabilize the salt formed (15). 

The replacement of ligands of a metal carbonyl cation, either carbon monoxide or another ligand, serves as a valuable route to substituted cationic metal carbonyls. 

The Group VI metals would not be expected to form binary metal carbonyl cations, but they do form some substituted cations with nitrogen and phosphorus ligands. The paramagnetic monomeric and dimeric chromium pentacarbonyl iodides react in liquid ammonia with iodide expulsion. 

The Group VII metals form stable, diamagnetic binary metal carbonyl cations from their pentacarbonyl halides. 

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