Homoleptic aryl complexes

Examples of silver(l) alkyl and alkenyl (including aryl) complexes have been known from as early as 1941 6-9 however, the number of examples is fairly limited with respect to that of the heavier congeners, copper(l) and gold(l). Such a phenomenon can readily be attributed to the relatively low stability of this class of complexes, both photochemically and thermally. Simple homoleptic alkyl and alkenyl complexes of silver(i) are known to be very unstable under ambient temperature and light, and successful isolation of this class is fairly limited and mainly confined to those involving perfluoroorganics.10 The structures and the metal-carbon bond-dissociation energies for... 

Homoleptic germylenes, preparation and properties, 3, 773 Homoleptic lanthanide(II) alkyl compounds, properties, 4, 4 Homoleptic manganese aryl complexes, preparation, 5, 816 Homoleptic manganese isonitrilates, preparation, 5, 773—774 Homoleptic molybdenum complexes, preparation and characteristics, 5, 514... 

The efficiency of functionalized cyclopentadienyl complexes is meanwhile well established [78,191-202]. Because cyclopentadienyl ligands still dominate the field of organolanthanide chemistry, a selection of the functionalized ligands utilized is depicted in Fig. 11. In the field of aryl complexes, which represented the first well-characterized homoleptic derivatives [203], multiple functionalization has already been started [204]. 

M. M. Olmstead, P. Power, and S. C. Shoner, Isolation and X-Ray Crystal Structures of Homoleptic, Transition-Metal Aryl Complexes [(LiEt20)4VPh5] and [(LiEt20)3CrPh5], Organomeiallics 1, 1380-1385 (1988). 

The best characterized homoleptic aryls are [Li(OEt2)]4[FePh4]124 and [Li(OEt2)]2[Fe(naphthalenide)4] as well as (mes)Fe(ju.-mes)2Fe(mes)125 and many of its derivatives (Section 17-E-9). The Fe° complex [Li(OEt2)]4[FePh4] has remarkable activity toward dinitrogen and is synthesized by reaction of FeCl3 and 10 equivalents of phenyl lithium in diethyl ether ... 

Osmium forms a wide variety of alkyl and aryl complexes including homoleptic alkyl and aryl complexes and many complexes with ancillary carbonyl (see Carbonyl Complexes of the Transition Metals), cyclopentadienyl (see Cyclopenta-dienyl), arene (see Arene Complexes), and alkene ligands (see Alkene Complexes). It forms stronger bonds to carbon and other ligands than do the lighter elements of the triad. Because of this, most reactions of alkyl and aryl osmium complexes are slower than the reactions of the corresponding ruthenium complexes. However, because osmium is more stable in higher oxidation states, the oxidative addition (see Oxidative Addition) of C-H bonds is favored for osmium complexes. The rate of oxidative addition reactions decreases in the order Os > Ru Fe. 

While inorganic complexes of osmium in oxidation states +4 through +8 have been known for many years, the study of high-valent alkyl and aryl complexes of osmium is much more recent. The organometallic complexes include homoleptic see Homoleptic Compound) alkyls and aryls, oxo alkyls and aryls, nitrido/imido alkyls and aryls, and cyclopentadienyl see Cyclopentadienyl) alkyls and aryls. The majority of these are complexes of osmium(VI). 

Over the years the homoleptic see Homoleptic Compound) alkyl and aryl complexes were one of the major challenges in organolanthanide chemistry. The simplest organometallic... 

Homoleptic aryl-lanthanides are less studied then alkyl complexes. After the first lanthanide aryl complex [Li(THF)4][Lu(C6H3-2,6-Me2)4], neutral triphenyllantha-nides Ph3Ln(THF)3 (Ln = Er, Tm, Yb) were synthesized in THF by reaction of metallic lanthanides with Ph2Hg or... 

Homoleptic alkyl and aryl complexes of vanadium(IV) can in principle be synthesized from VCI4. However their thermal instability of makes them difficult to isolate. In some cases, the use of lithium alkyls and alkyl Grignards leads to reduction from V(IV) to V(III). Interestingly, [V(l-norbornyl)4], prepared from VCI4 and Li(l-norbornyl), is relatively stable up to 100 °C and is only moderately air sensitive [30]. The most air/ thermally stable complex of this class is [V(Mes)4], which was isolated in nearly quantitative yield by air oxidation of Li[V(Mes)4] [31]. 

The Homoleptic Alkyl and Aryl Complexes and the Related Compounds... 

Some difficulty was originally encountered in preparing homoleptic cr-bonded alkyl or aryl complexes of the actinoids, but (as for the lanthanoids. Section 24.8) use of the chelate TMED (Me2NCH2CH2NMe2) was the key to stabilizing the Li+ salt of [ThMey] (equation 24.42 and Figure 24.7a). Similarly, hexaalkyls of type Li2UR -7TMED have been isolated. 

Vinyl complexes are typically prepared by the same methods used to prepare aryl complexes. Vinyl mercury compounds, like aryl mercury compoimds, are easily prepared (by the mercuration of acetylenes), and are therefore useful for the preparation of vinyl transition metal complexes by transmetallation. The use of vinyl lithium reagents has permitted the s rnthesis of homoleptic vinyl complexes by transmetallation (Equation 3.35). Reactive low-valent transition metal complexes also form vinyl complexes by the oxidative addition of vinyl halides with retention of stereochemistry about the double bond (Equation 3.36). Vinyl complexes have also been formed by the insertion of alkynes into transition metal hydride bonds (Equation 3.37), by sequential electrophilic and nucleophilic addition to alkynyl ligands (Equation 3.38), and by the addition of nucleophiles to alkyne complexes (Equation 3.39). The insertion of alkynes into transition metal alkyl complexes is presented in Chapter 9 and, when rearrangements are slower than insertion, occurs by s)m addition. In contrast, nucleophilic attack on coordinated alkynes, presented in Chapter 11, generates products from anti addition. 

Homoleptic lithium complexes [Li NNE 2]Cl (E = 0, S), containing Juc-coordinating NNE-donor hgands prepared from bis(3,5-dimethylpyrazol-l-yl)methanewith BuLi and alkyl- or aryl-containing isocyanates or isothiocyanates, have been used to synthesize a series of scandium and yttrium complexes. ... 

Scheme 21 Homoleptic Metal Allcyl and Aryl Complexes by Transmetalationl ...

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