Alkylation 1,3-diketone metal complexes

Simple a-diimines are hydrolytically unstable, but can be stabilized as metal complexes by virtue of the formation of stable five-membered chelate rings.68 69 a-Diketones and glyoxal undergo metal template reactions with amines to yield complexes of multidentate ligands such as (34),70 (35)71 and (36).72>73 In the last case, the metal exerts its stabilizing influence on the a-diimine partner in an equilibrium process (Scheme 5). The same phenomenon occurs with amino alcohols74 75 in addition to amino thiols. The thiolate complexes (37) can be converted to macrocyclic complexes by alkylation in a kinetic template reaction (Scheme 5).76 77... 

The (3-diketonate chelate complexes are very stable and exhibit properties which are rather typical of aromatic systems. Many of their reactions such as halogenation, alkylation and acylation can be compared with those of the P-diketonate anions associated with alkali metal cations. However, complexes of transition and other metals add to the stability of the system, so that quite vigorous reaction conditions can be employed. In most of the work carried out on P-diketonate chelates, the modified ligand has not been removed from the metal ion, but this can usually be effected if desired. 

Metal aUcoxides and alkyls are useful starting materials, particularly for the preparation of some unsolvated P-diketones that require anhydrous conditions (see Section 3.3). Addition of /3-diketonate ligands to metal alkoxides has also been used to produce heteroleptic metal complexes that are less reactive than the homoleptic metal alkoxides this simplifies the use of such complexes in chemical vapor deposition applications. ... 

Derivatives of Sn , Ti Cr , V , Cu, Sm are well-known as reductants [108, 109]. In particular, Kagan s reagent Sml2 reduces acyl chlorides to diketones, aldehydes, and ketones to pinacols in aptotic media and to alcohols in protic media [110], It has also been applied to many other organic reactions [110], Cr salts have been extensively used to reduce alkyl- and aryl halides [109]. These reduced metal complexes have been known as reductants of transition metal ions since Taube s pioneering work [108, 109]. 

The volatile metal-containing precursors which satisfy the ALD criteria fall into four main categories (i) halides, (ii) y0-diketonate complexes, (iii) alkoxides, and (iv) true organometallics, viz. metal alkyls and cyclopentadienyl-type compounds (Fig. 3). Also amido complexes have recently gained attention as possible ALD precursors. Occasionally other compounds have been used as ALD precursors for thin films, for instance, metal nitrates, carboxy-lates and isocyanates [17,18]. 

In some cases, alkoxide displacements at a metal center proceed sequentially and at different rates so that, if redistribution processes do not intervene, mixed diketonates can be obtained by adjusting the ratios of reactants.190,191 Recently, bimetallic / -diketonates of the type M2(diketonate)2(OR)4 (M = Mo, W R = alkyl) have been prepared from diketones and M2(OR)6. X-Ray studies show that one diketonate is attached to each metal atom so that unbridged M=M units are retained although rapid rotation about this multiple bond can occur.192 Diketonate complexes with metal-metal multiple bonds are rather uncommon, one other example being C2v CK-Mo2(Me-COCHCOMe), (02 CMe)2.193... 

Alkoxides and aryloxides have been intensively studied because of their interest, especially for Ba, as precursors to oxide materials having desirable electronic properties this development was stimulated by the discovery of superconducting materials such as YBajG CVx. The same interest applies to other volatile complexes like /3-diketonates. The alkyl or aryl oxides (also siloxides) are readily obtained by a variety of methods, notably (a) direct interaction of the metals with ROH in THF, toluene saturated with NH3,22 or other ether solvents (b) the interaction of... 

Asymmetric AUylation. Asymmetric allylation of p-diketones using the palladium analog of (1) has been described. Higher enantioselectivity can be achieved in this case using ferrocenylamines with a modified alkyl side chain. For synthetically useful ferrocenylamine complexes of other metals, see (R)-N-[2-(N,N-Dimethylamino)ethyl]-N-methyl-l-[(S)-l, 2-bis-(diphenylphosphino)ferrocenyl]ethylamine. 

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