Anions transition metal

The initial step of the reaction with tin(II) chloride reduces the highly oxidized metal in the transition metal anions to low valency cations these are capable of forming stable colored complexes with thiocyanate. 

Salt Elimination-. Reaction of a Transition Metal Anion with a Silicon... 

The transition metal-group IV metal bond can be formed both by attack of a transition metal anion at a group IVg halide and by attack of an alkali metal derivative of the group IV element at a suitable transition metal complex. 

Transition metal anions have widely been used in the synthesis of the first row transition metal derivatives of group IV metals however only in one case does the reaction take place with chlorosilanes... 

Other transition metal anions fail in giving the expected compounds . Germanium halides react more easily but are useless for the preparation of optically active compounds. Indeed, optically active bromo-germanes are not known, and chlorogermanes rapidly racemize in ether or tetrahydrofuran. ... 

This process may be regarded as the reverse and the complement of the preceding reaction. It has mainly been utilized where transition metal anions are not available (e.g. in Ti, Ni and Cu group). 

Transition metal acyls are often synthesized by acylation of a transition metal anion (24). Also, transition metal acyls (sometimes transient) can be... 

The bicyclic isomers 109 are clearly formed by electrocyclic ring closure of their initially formed monocyclic valence isomers and not from the nucleophilic attack of the transition metal anion on traces of 52 in equilibrium with OFCOT, as shown by the low-temperature reaction of [Fe(f/5-C5H5)-(CO)2] . At -78°C, the l9F NMR spectrum of the crude reaction mixture indicates exclusive formation of the monocyclic complex 108b, but on warming the solution to room temperature the resonances of the bicyclic valence isomer 109b grow in (184). 

At least in one example the phenylthio substituent has also been used as a leaving group in the reaction of transition metal anions and cyclopolysilanes73. Thus, SigMen[Fe(CO)2Cp] is formed in excellent yields by the reaction of SigMenSPh with Na[Fe(CO)2Cp] without any detectable side-products due to transmetallation reactions (equation 34). The method very likely will gain increasing importance in the future. 

The first successful syntheses utilizing trifluoromethyl iodide in transition metal chemistry were reported by Stone and his students. Stone reasoned that if CF3I would not react with transition metal anions to form trifluoromethyl derivatives [see Eq. (3)] then perhaps compounds containing perfluoroalkyl substituents could be generated by the oxidative addition of perfluoroalkyl halides to low valent transition metal substrates (9,10). The first reported trifluoromethyl-substi-tuted transition metal complex prepared by this route is shown in Eq. (4) (41). 

The most important synthetic routes continue to be (1) the elimination of an alkali halide between the salt of a transition-metal anion and a silicon halide, and (2) oxidative addition and addition-elimination reactions. The present position regarding the scope and limitations of these and other routes is outlined in this section. 

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.,... 

Reference has already been made in Section II,A,3 to the harmful effects of polar solvents, in particular tetrahydrofuran, in the preparation of silicon-transition-metal compounds from a silicon halide and a transition-metal anion (61, 137, 138, 300, 305, 306, 310, 331, 337). Frequently, silicon-oxygen rather than silicon-metal compounds result, e.g. (138, 306, 336),... 

More recently, Peer and Lagowski (75) presented spectroscopic and electrochemical evidence for the existence of Au- ions in liquid ammonia. This is the only example of a transition metal anion in any solvent. In a simple yet elegant technique, the solutions of auride ion, Au, could be prepared by the dissolution of metallic gold in ammonia... 

Fig. 1. Examples of the synthesis of heteronuclear gold cluster complexes by the reaction of Au(PPh3)Cl with transition metal anions.

Replacement of the Au(PR3)C1 molecule by the AuC12 anion in reactions with transition metal anions gives rise to linear trinuclear Au-M-Au heterometallic complexes, as in the reactions (234)... 

Synthesis from transition metal anions and germyl halides. 1244... 

Salt-elimination reactions between transition metal anions and tin... 

TABLE 10. Recent tin metal compounds prepared from transition metal anions and organotin halides... 

King and Braitsch prepared a number of halomethyl complexes of transition metals by reacting the appropriate transition metal anion with diha-lomethanes according to Eq. (4) (33). CH2C1I was used to prepare the chloromethyl derivatives of [MCH2X] directly. Since the C—I bond is weaker than the C—Cl bond, the C—I bond is preferentially cleaved in most cases. This method is a good synthetic route to the chloromethyl complexes of Mo, W, and Mn, but not for those of Fe. 

The iodide complexes, [CpMo(CO)3 (CH2)3I ] [M = Mo (96) or W (97)], were originally prepared by Winter and co-workers (162). Both 96 and 97 react with excess iodide to form [CpMfCOJjIfCOfCH CHj ]. Winter and co-workers found that transition metal anions may induce similar cyclization reactions. Hence, reaction of excess Na[CpMo(CO)3] with Br(CH2)3Br yields 89, which reacts with further Na[CpMo(CO)3] to form an intermediate anionic acyl complex, which in turn undergoes elimination of Br- to form the carbene ligand in a manner similar to that... 

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