Magnesium alkyl complex

Tris(pyrazolyl)hydroborato magnesium alkyl derivatives [Tp ]MgR are readily prepared by the reactions of [M][Tp ] (M = K, Tl) with solutions of the appropriate dialkyl-magnesium [Eq. (3) 14-17]. The reaction is very general and a series of primary, secondary tertiary, vinyl, and phenyl derivatives have been obtained, as illustrated in Table 1. The magnesium alkyl complexes [Tp ]MgR are all white crystalline solids that are soluble... 

To this end, we have recently found that low-coordinate magnesium alkyl complexes can be stabilized by bulky A,A -diisopropylphenyl P-diketiminate ligands, and that these compounds initiate a rapid polymerization of MMA. The alkyl complexes are prepared either by reaction of the diketimine with dialkyl precursors such as MgMe or by treatment of RMgX (R = Me, i-Pr, t-Bu, Ph X = Cl, Br) with the lithium salt of the ligand (Scheme 23.15). ... 

SCHEME 23.15 Synthetic routes to P-diketiminate magnesium alkyl complexes. 

The absence of a reactirai between the magnesium alkyl complex and the heterocycles is noteworthy due to the precedent for the nucleophilic addition of calcium alkyls to pyridine and substituted pyridines. Catalytic dearomatization and hydrosilylation of these heterocycles employing magnesium hydrides and magnsium alkyls as precatalysts have yet to be reported. Under catalytic craiditions the observed decomposition of the magnesium intermediates at elevated temperatures may be responsible for the lack of catalytic turnover. 

Hydroboration of aldehydes and ketones by pinacolborane is aided by a pre-catalyst cycle involving a heteroleptic magnesium alkyl complex and the ketone. ... 

The detail of the structure of the polymerisation centre present in suppported Ziegler-Natta catalysts for a-olefin polymerisation has been the subject of much research effort (e.g./-/2) The catalyst consists of a solid catalyst MgC /TiC /electron donor and a co-catalyst, an aluminium alkyl complexed with an electron donor. Proposed mechanisms for the polymerisation involve a titanium species attached to magnesium chloride with the olefin coordinated to titanium. The detail of the site at which the titanium species is attached is an important area of study in understanding the mechanism of catalysis and several recent papers 10-12) have investigated the surface structure of magnesium chloride and the attachment of TiCl4, in particular the interaction of titanium species with the 100 and 110 planes of a and (3- magnesium chloride. 

Standard Nd-based catalysts comprise binary and ternary systems. Binary systems consist of Nd chloride and an aluminum alkyl or a magnesium alkyl compound. In ternary catalyst systems a halide free Nd-precursor such as a Nd-carboxylate is combined with an Al- or Mg-alkyl plus a halide donor. By the addition of halide donors to halide-free catalyst systems catalyst activities and cis- 1,4-contents are significantly increased. In quaternary catalyst systems a solubilizing agent for either the Nd-salt or for the halide donor is used in addition to the components used in ternary systems. There are even more complex catalyst systems which are described in the patent literature. These systems comprise up to eight different catalyst components. 

Grignard reagent solutions comprise a complex distribution of magnesium alkyl and aryl derivatives [I]. In its simplest form, the composition of a Grignard reagent solution is described by the well-known Schlenk equilibrium [Eq. (1) 2]. 

However, it is noteworthy that oxygen atom transfer to the magnesium alkyl derivative does not occur rapidly at room temperature. This is presumably one of the factors that is responsible for the observation that the reactions of [Tp ]MgR with O2 are selective in the formation of alkylperoxo complexes, rather than the alkoxo derivatives. It is likely that this is a consequence of the sterically encumbered nature of the magnesium centers in these complexes. 

Grignard reagents, which have magnesium-alkyl bonds, and alkyl complexes with alkali metals, such as methyllithium. The syntheses and reactions of these main group compounds are typically discussed in detail in organic chemistry texts. 

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