Preparation transition metal carbonyl anions

For many of these compounds the method of preparation is to react an MX2 compound with a hydrido complex or a transition metal carbonylate anion, as in the following reactions ... 

Transition metal carbonyl anions having charges of 1- through 4- are known. Originally such anions were prepared by the reaction of neutral metal carbonyls with bases, for example,13... 

Since power ultrasound is capable of generating extremely high pressures and temperatures within microbubbles in a liquid medium the possibility arises that sonochemistry might replace conventional (and expensive) high pressure reactors. Power ultrasound has been found to dramatically reduce the temperatures and pressures required for the preparation of early transition metal carbonyl anions from the direct reaction of the corresponding metal chlorides with carbon monoxide (Scheme 10.6) [18]. In this particular case the yield of V(CO)6 (35%) can be obtained at 4.4 atmos pressure and 10°C whereas conventional methodology requires 200 atmos and 160°C. 

Suslick has made an extensive study of the sonochemistry of Fe(CO)5 which he has used as a probe to explore the chemical effects of high intensity ultrasound. Suslick and Johnson [280] have also shown that sonication greatly facilitates the preparation of early transition metal carbonyl anions. Hence, sonication of vanadium trichloride and sodium sand in THF solution gave a 35 % yield of NaV(CO)g under 4.4 atmospheres of carbon monoxide at 10 °(i. The equivalent thermal reaction requires the reaction to be caried out at 160 °C under 200 atmospheres of carbon monoxide. That is, the temperatures and pressures produced by cavitation are comparable to the bomb conditions normally required for the preparation of these compounds [281]. Suslick s review [3] presents further evidence in support of this original observation however, no further details of this work have appeared to date. 

Anions of transition-metal carbonyls are prepared by reducing the carbonyl and react with derivatives of group-IIB metals to yield mono-, di- and even trisubstituted derivatives ... 

Although a variety of new preparative routes has been developed in recent years (for reviews see refs 1 -10), the transformation of the metal-carbonyl carbon bond of a metal-carbonyl complex into a metal-carbene carbon bond is still the most useful and versatile method for preparing transition-metal carbene complexes. The addition of a carbanion to the carbon atom of a carbonyl ligand yields an anionic acyl complex that subsequently can be reacted with an electrophile to give a neutral carbene complex. Thus, the syntheses of anionic acyl and neutral carbene complexes are closely related, for almost all the carbene complexes considered in this section acyl complexes are precursors, although most have not been isolated and characterized. The syntheses of acyl complexes via CO insertion (for reviews see refs. 11, 12) or by reaction of metal carbonyl anions with acyl halides is outside the scope of this section. 

Heterobimetallic complexes have recently attracted considerable attention in light of the promise of enhanced reactivity as a result of the cooperativity between adjacent, but electronically different, metal centers. A large number of these bimetallic compounds have been synthesized by the reactions of organometallic halides with anionic metal carbonyls. Here, we describe an extension of this route to the synthesis of hydride rich. Os—Zr and Os—Rh complexes by the reaction of organometallic halides with a metal poly hydride anion. These preparations demonstrate the synthetic utility of transition metal polyhydride anions. 

Hieber and his school have carried out a systematic investigation of the transition metal carhonyl anions and derivative hydrides 169), and have synthesized many carbonyl anion and hydride clusters, particularly of the first row transition metals. The preparations of these clusters were all based on the reduction of a carbonyl compound. More recently a number of heteronuclear carbonyl anion and hydride clusters have been produced by condensation reactions. 

This is a special volume of Inorganic Syntheses that focuses on complexes that are likely to be useful as starting materials for the preparations of new transition metal coordination and organometallic compounds. There are chapters on complexes with weakly coordinated and therefore easily displaced ligands, low-valent complexes that undergo oxidative-addition reactions, substituted metal carbonyl complexes, nucleophilic metal carbonyl anions, transition metal clusters, a variety of cyclopentadienyl complexes, lanthanide and actinide complexes, and a range of other useful ligands and complexes. 

Preparation by Reduction of Carbonyl Compounds.- Reductions of carbonyl compounds have been reported using diphenylstibine, anionic Group 6 transition-metal carbonyl hydrides (chromium and... 

Metal carbonyls have been known for over 70 years. Within the last 35 years derivatives of the anions of the metal carbonyls have been synthesized. Within the last 10 years various derivatives of the metal carbonyl anions have acquired significance as intermediates in the preparation of interesting organometallic derivatives of the transition metals. In this chapter applications of anions derived from the metal carbonyls and the substituted metal carbonyls in syntheses of unusual organometallic derivatives of transition metals and the chemistry of the organometallic derivatives thus synthesized will be discussed. 

Anionic complexes also can be prepared from (THT)Au(C6F5) which reacts with carbonyl anions in CH2CI2 to give compounds with Au to transition-metal bonds ... 

Boron-bonded p -borazine complexes of transition metals have been prepared by two different approaches (a) nucleophilic substitution of B,fi, fi"-trichloro-borazine with an anionic metal carbonyl reagent and (b) oxidative addition of a B-Br bond of 5,5, B"-tribromoborazine to a zerovalent group 10 complex (see examples in Scheme 9.2). 

Because transition-metal anions can be prepared conveniently in tetrahydrofuran solution, this cyclic ether was often used in earlier attempts to prepare silicon-metal compounds. It is now generally realized, however, that tetrahydrofuran can frustrate these attempts in two ways. First, it promotes electrophilic attack by the silicon compound on oxygen atoms of coordinated carbonyl groups this leads to the formation of products with Si-0 bonds (54, 138, 262, 300, 306, 310, 336,337), e.g.,... 

An interesting new development in aromatic phosphole chemistry has been the preparation and subsequent study of the electrophilic substitution reactions of transition-metal complexes of phospholyl anions, e.g. the phosphaferrocenes (165), which are obtained by the reaction of the appropriate P-phenylphosphole with transition-metal cyclopentadienyls or carbonyls, - and which undergo acetylation at... 

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