Neutral Homoleptic Compounds

Yb(CHR2)2(OEt2)2 + DMPE---------- Yb(CHR2)2(DMPE) + 2EtzO 

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Complexes of the type [LiLif] [LnCCHaSiMes)if] with L = THE or Et20 or with L2 = tmed are formed in the reaction of LiCH2SiMe3 with either the neutral, homoleptic compound Ln(CH2SiMe3)3 or with LnCls (62,122) ... 

The majority of these contain CO ligands. The neutral homoleptic carbonyls have not been isolated, but anionic M(CO)6 as well as highly reduced M(CO) species are known. The original synthesis of the -1 species required elevated temperatures and high pressure but recently two simple, atmospheric pressure methods have been developed. They involve reduction of pentahalides in pyridine with Zn/Mg or in dimethoxyethane with sodium naphthalenide under an atmosphere of CO. These yellow salts contain discrete M(CO)6 anions. The facile syntheses of the octahedral hexacarbonyl anions allowed systematic exploration of the previously difficult to access area of low-valent complexes of Nb and Ta. Since M(CO)s are rather inert towards displacement of CO the substitution products of general formula M(CO)6- L have to be obtained by other routes, for example, by reduction of MX(CO)6- L compounds. The monosubstituted derivatives are conveniently prepared via the following method87 ... 

During the Manhattan project, a wide range of compounds was screened in the search for volatile uranium compounds that could be used for separation of isotopes of uranium, since UFe was not an easy compound to handle. The leading organometallic chemist of the day, Henry Gilman, investigated the synthesis of simple alkyls and aryls, concluding that such compounds did not exist, or at least were unstable. Even today, just one neutral homoleptic... 

The most stable carbonyl for ruthenium is the trimeric tetracarbonyl Ru3(CO)i2 (1), with Ru(CO)5 (2) and Ru2(CO)9 (3) being much less stable. Compounds (2) and (3) are prepared from Ru3(CO)i2 and revert to it on standing or irradiation. No neutral homoleptic see Homoleptic Compound) mthenium carbonyl of higher nuclearity, in particular no analog of Os6(CO)i8, is known. 

Neutral and cationic homoleptic (see Homoleptic Compound) tnngsten-isocyanide complexes W(CNR)6 and [W(CNR)y] + (R = alkyl, aryl) are known, and W(CO)e (CNR) (n=l-3) complexes may be prepared from W(CO)6 and excess isocyanide in the presence of catalytic amounts of C0CI2 or PdO. Iso-cyanides are isoelecfronic with CO and also insert into the W-R bonds of alkyl complexes (see Alkyl Complexes). For instance, the alkyl-nitrosyl complexes Cp W(NO)(X)(CH2Bfr) (X = NHBfr, OBfr) react with CNBu to afford -iminoacyl complexes, and the isocyanide complexes, Cp W(CO)2(Me)(CNR) (10, R = alkyl), rearrange to afford either -iminoacyl Cp W(CO)2( -MeCNR)(ll) or ij -l-azaallyl Cp W(CO)2( -CH2CHNR) (12) derivatives, depending upon the reaction conditions (equation 4). ... 

Again, the coordination at lithium is distorted tetrahedral. The neutral homoleptic phosphinomethyl aluminium compounds Al[C(PMe2)2Xl3 (X = PM62 or SiMej) synthesised according to... 

Potentially coordinatively unsaturated dithiolene-metal complexes are rare,298-306 and 1 1 dithiolene-transition-metal complexes with no other ligands are, to our knowledge, unprecedented.307 The neutral complex [PdS2C2(COOMe)2]6,308 is homoleptic containing one dithiolene unit for each palladium atom and no other ligands. Electrochemical reduction of the compound depicted in Figue 21 proceeds in four reversible steps. 

Additional bonds are thus donor bonds, and to accept electron pairs from neutral and anionic ligands, zinc uses the two remaining 4p orbitals to form sp2 and sp3 hybrids. In the absence of steric effects, discrete, homoleptic, anionic tri- and tetraorganozinc compounds (zincates) have almost always ideal trigonal-planar and tetrahedral geometries, respectively. 

Since the discovery of hexacarbonylvanadium(O) and hexacarbonylvanadate( 1-) by Calderazzo and co-workers in 1959 and 1960, these substances have been key precursors to a variety of vanadium compounds, including inorganic noncarbonyl species, organovanadium complexes," and other vanadium carbonyls. Neutral V(CO)6 is of special interest in that it is the only isolable 17-electron homoleptic metal carbonyl and exhibits fascinating chemical properties that are often reminiscent of iodine and classic pseudohalogens. ... 

These are metal compounds that have 3 to 9 hydrogen atoms which may be neutral, cationic, or anionic. They usually have tertiary phosphines or 7 -C5H5 as ligands but some homoleptic species are known. Some examples are given in Table 2-8. 

The controlled chemical oxidation of the Ti(m) aryl compound [Li(THF)4][Ti(G6Cl5)4] with [N(4-Br-C6H4)4][SbCl6] in GH2C12 at 0°C gives the homoleptic Ti(iv) neutral species Ti(C6Cls)4, the molecular structure of which has been determined by X-ray diffraction (Figure 4).207... 

Compounds included in this chapter are the homoleptic amides and imides of empirical formula M(NRR ) and M(NR) , where R, R = H, alkyl, aryl or trialkylsilyl, and the mixed amido-imido compounds of formula M(NRR ) (NR). Brief mention is given to certain compounds of formula L M(NRR ) or L M(NR) , where L represents a group of ligands, neutral or anionic, which also share the coordination sphere of the metal, when the chemistry of the M—N bond is of particular note. Metal-containing compounds derived from halogen azides are not discussed. 

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