Group 2 amido complexes

The C-coordinated thiazolium complexes are the result of the proton-induced cyclization reactions (980M513). Thus, complex 1 on protonation with tetrafiuoroboric acid yields the C-coordinated thiazolium structure 2. In turn, the nitrile complex 3 under these conditions is transformed to the thiazolium cationic species 4. Protonation of the amido complex 5 with tetrafiuoroboric acid also results in a cyclization but it proceeds differently. The amino group of the CONH2 moiety is lost and BF3-framework is coordinated via the carbonyl oxygen in an overall neutral complex 6. 

The inner-sphere mechanism is restricted to those complexes containing at least one ligand which can bridge between two metal centers. The commonest examples of such ligands are the halides, hydroxy or oxo groups, amido groups, thiocyanate... 

Nin-amido complexes such as (117) react with small electrophiles by insertion either in the Ni—N bond (e.g., with C02 to form (118)) or in the N—11 bond. With unsubstituted aryl groups (Ar = Ar = Ph), both a monomeric complex (117) or a dimeric species (119) is formed, depending on the amount of PMe3 added. Using bulky borylamide ligands, an almost linear, two-coordinate Nin complex could be obtained and structurally characterized.467 The N—Ni—N angle in (120) is 167.9°. 

Two equiv. of 6,6-di(cyclopropyl)fulvene react at 60 °C over a period of a week with Ca[N(SiMe3)2]2-(THF)2 bis in THF to yield the metallocene 170. The heteroleptic amido complex 171 is detected as an intermediate with 111 and 13C 1H NMR spectroscopy. A 1 1 reaction of the calcium amide and 170 also produces 171 in solution, an equilibrium involving these three derivatives exists (Equation (30)). The calcocene 170 crystallizes at — 20 °C from THF as colorless cuboids. The metal center is surrounded by the four ligands in a distorted tetrahedral manner, and the cyclopentadienyl group and the propylidene fragment are coplanar with each other.393... 

Noyori and coworkers reported well-defined ruthenium(II) catalyst systems of the type RuH( 76-arene)(NH2CHPhCHPhNTs) for the asymmetric transfer hydrogenation of ketones and imines [94]. These also act via an outer-sphere hydride transfer mechanism shown in Scheme 3.12. The hydride transfer from ruthenium and proton transfer from the amino group to the C=0 bond of a ketone or C=N bond of an imine produces the alcohol or amine product, respectively. The amido complex that is produced is unreactive to H2 (except at high pressures), but readily reacts with iPrOH or formate to regenerate the hydride catalyst. 

Magnesium amides can form a wide range of mixed metal amido complexes with alkali metal ions (M2[Mg(NH2)4]) (M = K, Rb or Cs).These contain tetrahedral Mg-centered [Mg(NH2)4] ions connected in three-dimensional networks by coordination of the amido groups to the group 1 metal ions. The most common hetero metal is lithium and lithium amido magnesiates are readily accessible by the addition of a lithium amide to a magnesium amide. 

Table 10 gives a listing of methyleneamido complexes. The listing includes several bis(methylene-amido) complexes and representatives from most of the metals in the transition series with the exception of complexes from the copper group. 

Ligand deprotonation may result in some interesting ambiguities in oxidation state, which ultimately allow us to consider new patterns of reactivity. We begin by considering the iron(m) complex of a macrocyclic amine 5.18. Deprotonation of the amino group in the complex gives an iron(m)-amido complex 5.19 (Fig. 5-34). 

Amidocarbonylation aldehydes, 11, 512 enamides, 11, 514 overview, 11, 511-555 Amido complexes with bis-Cp titanium, 4, 579 Group 4, surface chemistry on oxides, 12, 515 Group 5, surface chemistry on oxides, 12, 524 with molybdenum mono-Cp, 5, 556 with mono-Cp titanium(IV) alkane elimination, 4, 446 amine elimination, 4, 442 characteristics, 4, 413 via dehalosilylation reactions, 4, 448 HCL elimination, 4, 446 metathesis reactions, 4, 438 miscellaneous reactions, 4, 448 properties, 4, 437... 

The extensive chemistry of amido complexes, and, more particularly, of alkylamido complexes, reveals that the planar form is almost invariably found, along with bridging amides (221). Much attention has been paid to the synthesis of metal amido complexes of early transition metals, lanthanides and actinides. The amido group, particularly where it is bulky, confers unusual low coordination numbers on the metals and can also produce materials with considerable kinetic stability toward attack by nucleophiles (42, 67). However, the relevance of this extensive and fascinating chemistry to nitrogen fixation is somewhat problematic. 

As regards propylene polymerisation in the presence of methylaluminoxane-activated catalysts based on the monocyclopentadienyl (Me4Cp, Ind, Flu) amido complexes of group 4 metals, it is known that catalysts of this type can in some instances give isotactic [153], syndiotactic [154] and atactic [155] polypropylenes. 

R = alkyl, aryl) undergoes insertion reactions with C02, COS, CS2, and CSe2 to form carbamate complexes and reacts with alcohols to form alkoxide complexes. The structural motif of the amido complexes is highly dependent on the steric bulk of the R group. When R = phenyl, the complex is... 

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