Amido complexes group 2 metals

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... 

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. 

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. 

Functionalized tertiary aryl phosphines play an important role in transition metal coordination chemistry. These compounds have been used as ligands in synthesis, catalysis, mechanistic studies, and in the study of coordination compounds as structural models. In this contribution the syntheses of two new types of these ligands, tertiary aryl phosphines functionalized by an amide group, are detailed. The published coordination chemistry of these compounds includes the study of intramolecular N—H oxidative addition, the synthesis of chelates stabilized amido complexes, and the preparation of complexes with both ftve- and six-membered chelate rings. ... 

Potentially pentadentate and trianionic asymmetrical N203 SBs containing a hard amido donor atom have recently been prepared.141 The presence of the amido donor group stabilizes high-oxidation-state metal complexes. This ligand can twist to give a helical complex with Mnm. 

The ruthenium-catalyzed reduction of polar bonds using H gas, rather than a sacrificial reductant such as isopropanol, is an atom-economical reaction that has been thoroughly explored. A key discovery by our laboratory was that neutral, stmctur-ally characterized metal-amido complexes such as 11 (Scheme 7) could cleave H heterolytically to yield the fran -dihydride complex 12, and that these are crucial intermediates during catalysis.R - Once the H-N-Ru-H moiety is in place, proton and hydride can then be transferred to the substrate. Having methyl groups instead of hydrogens on carbons alpha to the amido group (beta to the ruthenium) in this case and in the case of 1 (Scheme 4) was important to allow the isolation of an amido... 

Scheme 4 Synthesis of bis (ureate) chloro, alkyl, or amido complexes of group 4 metals. DME= 1,2-dimethoxyethane...

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