Carbonylmetallates

Fig. 60. Mixcd-melal chi.sleis from carbonylmetalate anions and dppm-slabili/cd Iriansiular clns-ters M = Pd. Pt, M = Mot i/ACjHs). W(()Tc,Hs). Mn(CO), . Co(CO). M" = MolCOld if-CsHstl. (WtCObti/ CsHs) . IMntCOtq. (CotCOtal, X = Cl. 1.

Carbocations as electron acceptors in aromatic EDA complexes 192 Bis(arene)iron(II) complexes with arene and ferrocene donors 198 Carbonylmetallate anions as electron donors in charge-transfer salts 204 Aromatic EDA complexes with osmium tetroxide 219... 

CARBONYLMETALLATE ANIONS AS ELECTRON DONORS TN CHARGE-TRANSFER SALTS... 

Isolation and the spectral characterization of charge-transfer salts of carbonylmetallates... 

The charge-transfer salts of carbonylmetallates are thus distinguished from the iodide salts in the breadth of photochemistry that obtains upon exposure to visible light. For example, the continuous irradiation of the... 

Thermal annihilation of carbonylmetallate anions by carbonylmetal cations... 

Nowadays we look with other eyes at organometallic compounds the family of which has expanded enormously. Some members of this family are soluble in water due to their ionic nature the legions of anionic carbonylmetallates (e.g. [Ni(CN)(CO)3] ) and cationic bisphosphine Rh-chelate complexes (e.g. [Rh(BDPP)(COD)] ) just come to mind. Others obtain their solubility in water from the well soluble ligands they contain these can be ionic (sulfonate, carboxylate, phosphonate, ammonium, phosphonium etc. derivatives) or neutral, such as the ligands with polyoxyethylene chains or with a modified urotropin structure. 

The carbonylmetallate anions are extremely useful organometallic reagents, particularly for the syntheses of heteropolymetallic clusters.3,4,7 However, they have rarely been isolated in the solid state and their solutions are obtained either by reduction of their dimers or by reaction of NaCsHs with the parent metal carbonyls,2 and immediately used. The first method is not very economical since the dimers are usually themselves obtained from the metallate anions. The second method has been improved as detailed below to allow the easy isolation of the pure Na[M(CO)3(//s-CsH5)] (M = Cr, Mo, W) solids as DME solvates.4 The nonsolvated Na[M(CO)3(f/5-C5H5)] salts can... 

The trinuclear complex trans-Pt[Mo(CO)3( /5-C5H5)]2(PhCN)2 is prepared by the reaction of two equivalents of sodium carbonylmetallate with the square planar platinum(II) complex PtCl2(PhCN)2.3 Both cis and trans isomers afford the trans trinuclear chain complex. The lability of the benzonitrile ligand in the latter can be used advantageously for cluster synthesis this will be described in the next section. 

Alkylation reactions of [Re(CO)4]3 have provided the first alkyl derivatives of carbonylmetallates(3 —). Although the reactions of alkylating agents with Na3[Mn(CO)4] are not yet well understood, treatment of a solution of Na3[Re(CO)4] in HMPA with two equivalents of methyl tosylate gave the first dialkyl derivative of a carbonyl trianion, as a thermally stable sodium salt. Addition of this solution to aqueous [Ph4E]Cl (E = P or As) caused nearly quantitative precipitation of product as shown in Eq. (11). High... 

Approximately 25 years after Mond and co-workers had prepared the first carbonyl of cobalt, Co2(CO)8 (78), Hieber obtained HCo(CO)4 by the acidification of salts containing [Co(CO)4] (79), one of the first established carbonylmetallates (80). In 1941, Behrens, a student of Hieber, initiated his important and extensive investigations on the reduction of metal carbonyls and their derivatives by alkali and alkaline earth metals in liquid ammonia (81). At this time he established that various salts of [Co(CO)4]-, including Na[Co(CO)4] and K[Co(CO)4], could be obtained from the neutralization of HCo(CO)4 or the reduction of Cd[Co(CO)4]2 by sodium or potassium in liquid ammonia (4). On the basis of Behrens pioneering studies, we were... 

Of the homoleptic carbonylmetallates(l -) we have attempted to reduce, [Co(CO)4] appears to be the most difficult. Although the sodium salts of [M(CO)6] (M = V, Nb, and Ta) were quickly reduced in liquid ammonia by sodium metal to provide the corresponding trianions, [M(CO)5]3 (vide supra), it seems unlikely that we have ever effected complete reduction of Na[Co(CO)4] to Na3[Co(CO)3]. Even after 2 days of refluxing (at — 33°C) anhydrous ammonia solutions of Na[Co(CO)4] with excess Na, considerable amounts of the tetracarbonylcobaltate(l —) remained. Low yields of a heterogeneous-appearing brown to olive-brown insoluble solid were isolated this solid has been shown to contain Na3[Co(CO)3] (vide infra). As in the case of [Re(CO)s], we found that solutions of potassium in liquid ammonia were far more effective at reducing [Co(CO)4]-. However, unlike [Re(CO)s], [Rh(CO)4], or [Ir(CO)4] (vide infra), there was no evidence that [Co(CO)4] was reduced by sodium or potassium metal in hexa-methylphosphoric triamide. We observed that excess sodium naphthalenide slowly (over a period of 40-50 hr at room temperature) converted Na[Co(CO)4] in THF to an impure and insoluble brown powder that contained Na3[Co(CO)3], but this synthesis appeared to be of little or no utility. 

Of the known carbonylmetallates(3—), those of rhodium and iridium have received by far the least attention. However, unlike Na3[Co(CO)3], solutions of Na3[Rh(CO)3] and Na3[Ir(CO)3] have been prepared by reduction of the corresponding Na[M(CO)4] in HMPA in accord with Eq. (29). 

The reaction of a carbonylmetalate with a neutral metal carbonyl has been labeled a redox condensation by Chini et al. (40, 41) and has been as widely used as a pyrolysis reaction for synthesizing mixed-metal clusters. Carbonylmetalates usually react rapidly with most neutral carbonyls, even under very mild conditions. A large number of mixed-metal hydride clusters have been formed via this type of reaction, primarily because the initial products are anionic clusters that in many cases may be protonated to yield the neutral hydride derivative. 

The reaction of carbonylmetalates with monomeric and dimeric carbonyls has yielded many mixed-metal clusters, as illustrated by the reactions shown in Eqs. (28) (15), (29) (87), (30 (88), and (31) (88). 

The reaction of carbonylmetalates with trinuclear clusters provides, in many cases, a convenient synthesis of tetranuclear clusters. This reaction was first explored by Knight and Mays (105, 106), who allowed [Mn(CO)5] and [Re(CO)5] to react with trimeric clusters of the iron triad. A summary of the products that they obtained on using Os3(CO)12 as the starting trimer is shown in Scheme 3. Of particular mechanistic... 

Carbonylmetalates will displace a halide from a metal halide complex to yield a metal-metal bonded species, Eq. (39). With di- and polyhalide... 

Reaction of a metal halide complex with a carbonylmetalate... 

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