Allyls homoleptic

Allyl Complexes. Allyl complexes of uranium are known and are usually stabilized by cyclopentadienyl ligands. AEyl complexes can be accessed via the interaction of a uranium halide and an allyl grignard reagent. This synthetic method was utilized to obtain a rare example of a "naked" homoleptic allyl complex, U(T -C2H )4 [12701 -96-17, which decomposes at 0°C. Other examples, which are more stable than the homoleptic allyl complex have been synthesized, ie, U(allyl)2(OR)2 (R = alkyl), U(allyl)2X (X = halide), and U(allyl)(bipy)2. 

For Th and U the homoleptic allyls (or 2-methylallyls), which are unstable above 0°C, may be prepared by the reaction... 

Molybdenum(II) and molybdenum(III) form an extensive array of multiply bonded dimers, which contain Mo-Mo quadruple and triple bonds respectively. Much of the organometallic chemistry of this class of compound has come principally from the work of one research group. Homoleptic compounds suchas [Mo2Me8]" , [Mo() -allyl)4], which contains bridging and terminal allyl ligands (see Bridging Ligand), are readily synthesized from [Mo2(OAc)4]... 

Allylmagnesium halide and lithio reagents are available from allyl halides by lithiation and Mg reaction techniques. These active reagents combine with binary or complex transition-metal halides to form transition-metal-allyl complexes, including both homoleptic and ligand-substituted tj -allyl complexes with substituted and unsubstituted allyl groups. 

The allylmagnesium halide in ether is slowly added to a suspension or solution of the metal halide at 0°C or lower. Addition at low T improves yields and is essential for the synthesis of thermally unstable, homoleptic allyl complexes. The complexes are isolated by evaporation of the reaction mixture and extraction into an aromatic or alkane solvent. Purification is effected by crystallization or sublimation. When stable allyl compounds are prepared, an aqueous wash of the reaction mixture can be used to remove Mg salts and xs RMgX or -Li reagent the crude products can then be isolated from the resultant organic layer. 

Homoleptic allyl complexes and their derivatives are prepared by reacting allylmag-nesium chloride with metal halides . 

Carbonyl- and phosphine-substituted Rh and Ir allyls are synthesized by the reaction of an allylmagnesium halide with a metal halide precursor. Substituted derivatives are more stable than the homoleptic allyls and can be made at RT or 0 C. Examples are listed in Table 3. 

In the first edition of Scorpionates, a very limited number of Ni compounds has been described. Some of them continued to attract attention, as for example the homoleptic derivatives [Ni(Tp)2], [Ni(Tp )2], and [Ni(pzTp)2],470,471 for which in 2003 De Alwis and Schultz have reported electrochemical, magnetic, and spectroscopic properties,47whereas no other papers have been published on [Ni(Tp)(r]3-allyl)]472 and [NiX(R)(Tpx)PR3] complexes.473... 

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