Metal carbonyls, reaction with

The bluish white, hard, yet ductile, metal is inert to all acids and highly non-abrasive. Used for heavy-duty parts in electrical contacts and spinning jets. Reflectors are prepared from the mirror-smooth surfaces (e.g. head mirrors in medicine). Thin coatings provide a corrosion-resistant protective layer, for example, for jewelry, watches, and spectacle frames. The metal is a constituent of three-way catalysts. Rhodium complexes are used with great success in carbonylations (reactions with CO) and oxidations (nitric acid) in industry. Platinum-rhodium alloys are suitable thermocouples. 

Of course, even in low temperature solutions, unstable compounds may not be very long-lived. Modern fast-scanning FT-IR interferometers can produce high signal-to-noise spectra in a single scan. This means that metal carbonyl compounds with half-lives as short as 2 seconds can be easily detected using an unmodified interferometer (28,29). With improved interferometers, we anticipate that such studies will soon be extended to compounds with lifetimes —100 mseconds. However, detection of shorter lived species, such as reaction intermediates, requires much faster and more sensitive techniques. 

The reactivity of these metal hydride-metal carbonyl reactions can be correlated with the nature of the reactants in a manner consistent with the proposed mechanism nucleophilic attack by hydride on coordinated CO. Thus reactions involving the highly nucleophilic group IV hydride, Cp gZrHg, are much faster than those of group V metal hydrides. On the other hand, the relatively electrophilic neutral binary metal carbonyls all react with Cp2NbH under mild conditions (20-50° C), whereas more electron-rich complexes such as cyclopentadienylmetal carbonyls (Cp2NbH(C0), CpV(CO) ) or anionic carbonyls (V(CO)g ) show no reaction under these conditions. 

Successive reactions of metal carbonyl monoanions with EX3 can lead to structure types III through VIII in Scheme 1, although these compounds may also be obtained from other, less obvious routes. Further options include replacing the X units with alkyl or aryl functions, which is usually achieved by starting with EX3 xRx. 

The phase-transfer catalysed reaction of nickel tetracarbonyl with sodium hydroxide under carbon monoxide produces the nickel carbonyl dianions, Ni,(CO) 2- and Ni6(CO)162, which convert allyl chloride into a mixture of but-3-enoic and but-2-enoic acids [18]. However, in view of the high toxicity of the volatile nickel tetracarbonyl, the use of the nickel cyanide as a precursor for the carbonyl complexes is preferred. Pretreatment of the cyanide with carbon monoxide under basic conditions is thought to produce the tricarbonylnickel cyanide anion [19], as the active metal catalyst. Reaction with allyl halides, in a manner analogous to that outlined for the preparation of the arylacetic acids, produces the butenoic acids (Table 8.7). 

A,A-disubstituted derivatives 1-5. Amination of Group 1, 2, 11 and 12 organometallic compounds and a-metallated carbonyl compounds with these reagents takes place by a direct introduction of the R1R2N+ group to carbanions and enolates and for completion the reactions require only hydrolytic work-up (Scheme 3). 

Cationic mononuclear metal complexes, reaction with anionic carbonyl clusters, 30 155-158... 

Neutral metal complexes, reaction with carbonyl metallates, 30 152-155 Neutrons... 

Reactions with dioxygen generally afford the corresponding metal carbonyl derivatives, with loss of organic aldehyde or acid. This reaction can be expressed as an analog of multiple bond metathesis and corresponds to oxidation of vinylidene to CO [46]. Oxidation of OsHCl(=C=CHPh)(L)2 affords the styryl complex 0sC102( -CH=CHPh)(L)2 [243]. 

Carbonylation reactions with microwave irradiation have been investigated in connection with solid-state combinatorial chemistry.Since reactions requiring gaseous reagents cannot use microwave irradiation, metal carbonyl complexes, such as Mo(CO)6, Cr(CO)6, W(CO)6, and Co2(CO)8 have been employed as source of carbon monoxide. " Examples of aminocarbonylation performed with microwave irradiation are presented in Section 11.15.4.3 (vide supra). 

These were the first gold-metal-bonded complexes to be isolated and many examples are known.713 They are usually prepared by reaction of the appropriate metal carbonyl anion with a gold(I) complex [AuCIL], as in equation (77). Some typical examples are given in Table 13. 

Oligo- and polymethylene-bridged complexes can be prepared by reaction of metal carbonyl anions with w.w -dihaloalkanes. This method proved to be a simple entry to the iron series /j,-(CH2)j.][(t75-C5H5) Fe(CO)2]2 (x s 3) (283), but yielded quite different products in the case of Na[(T 5-C5H5)Mo(CO)3] (283) and Na[Mn(CO)s] (284). An alternative two-step synthesis of the iron compounds involves the preparation of the mononuclear w-haloalkyls LXM—(CH2)X—X, and a subsequent... 

Recently the unprecedented example of stereoselective C—Si bond activation in cu-silyl-substituted alkane nitriles by bare CQ+ cations has been reported by Hornung and coworkers72b. Very little is known of the gas-phase reactions of anionic metal complexes with silanes. In fact there seems to be only one such study which has been carried out by McDonald and coworkers73. In this work the reaction of the metal-carbonyl anions Fe(CO) (n = 2, 3) and Mn(CO) (n = 3, 4) with trimethylsilane and SiH have been examined. The reactions of Fe(CO)3 and Mn(CO)4 anions exclusively formed the corresponding adduct ions via an oxidative insertion into the Si—H bonds of the silanes. The 13- and 14-electron ions Fc(CO)2 and Mn(CO)3 were observed to form dehydrogenation products (CO) M(jj2 — CH2 = SiMe2) besides simple adduct formation with trimethylsilane. The reaction of these metal carbonyl anions with SiFLj afforded the dehydrogenation products (CO)2Fe(H)(SiII) and (CO)3Mn(II)(SiII). ... 

IV. Reactions of Metal Carbonyls and Metal Carbonyl Derivatives with... 

REACTIONS OF METAL CARBONYLS AND METAL CARBONYL DERIVATIVES WITH LIQUID AMMONIA... 

There is no doubt that most of the mono- and polynuclear metal carbonyls react with liquid NH3 via nonisolable carbonyl carbamoyl intermediate complexes in which the acid amide group —CONH2 is directly bound to the transition metal. For the reaction of Mn2(CO)10 with liquid NH3, we have been able to show that, at -78°C, quantitative formation of ciJ-Mn(CO)4(NH3)—CONH2 and HMn(CO)5 occurs (105) according to the following reaction ... 

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