Transition metals bonded compounds

This has been one of the useful methods for the preparation of transition metal complexes. Organoantimony and -bismuth anions have also been utilized for the preparation. Several transition metal bonded compounds with vanadium and copper as the transition metal are shown in equations 145 and 146 . ... 

Nucleophilic displacement of halides of transition metal bonded compounds by organic nucleophiles... 

B. Main Group Metal-Transition Metal Bonded Compounds. . 117... 

MOMEC is a force field for describing transition metal coordination compounds. It was originally parameterized to use four valence terms, but not an electrostatic term. The metal-ligand interactions consist of a bond-stretch term only. The coordination sphere is maintained by nonbond interactions between ligands. MOMEC generally works reasonably well for octahedrally coordinated compounds. 

Synthesis, reactivity, and structure of transition metal boryl compounds, derivatives of B,N- and B,0-heterocycles with B—M bond 98CRV2685. 

Chemical reactions of metal-metal bonded compounds of the transition elements. M. H. Chisholm and I. P. Rothwell, Prog. Inorg. Chem., 1982, 29,1-72 (238). 

The mutual influence of ligands in transition metal coordination compounds with multiple metal-ligand bonds. E. M. Shustorovich, M. A. Porai-Koshits and Y. A. Buslaev, Coord. Chem. Rev., 1975,17,1-98 (345). 

Chemical and stereochemical properties of compounds with silicon- or germanium-transition metal bonds. E. Colomer and R. J. P. Corriu, Top. Curr. Chem., 1981, 96, 79-107 (68). 

Bond angles in transition-metal tricarbonyl compounds A test of the theory of hybrid bond orbitals ... 

Pauling, L. Structure of Transition-Metal Cluster Compounds Use of an Additional Orbital Resulting from the f,g Character of spd Bond Orbitals Proc. Natl. Acad. Sci. (USA) 1977, 74, 5235-5238. 

Group-IIIB-Transition- or-Inner Transition-Metal Bonds 6.5.3. Formation from Other Group-IIIB Compounds 6.S.3.4. by Reaction with Metal Halides... 

Anionic complexes also can be prepared from (THT)Au(C6F5) which reacts with carbonyl anions in CH2CI2 to give compounds with Au to transition-metal bonds ... 

Compounds containing transition metals bonded to main-group elements, such as Hg and Sn, react with Au derivatives to form metal-metal bonds with the elimination of R3MCI ... 

Compounds containing group-lIB-transition-metal bonds arc characterized for almost every transition metal. Although there are more derivatives containing Hg than Zn or Cd, there is no difficulty in producing analogous compounds of each of these metals. No compound is known in which Zn, Cd or Hg is bonded to either lanthanide or aetinidc elements. 

Compounds containing both Hg—X and Hg-transition-metal bonds can rearrange ... 

Indeed, these reactions proceed at 25 °C in ethanol-aqueous media in the absence of transition metal catalysts. The ease with which P-H bonds in primary phosphines can be converted to P-C bonds, as shown in Schemes 9 and 10, demonstrates the importance of primary phosphines in the design and development of novel organophosphorus compounds. In particular, functionalized hydroxymethyl phosphines have become ubiquitous in the development of water-soluble transition metal/organometallic compounds for potential applications in biphasic aqueous-organic catalysis and also in transition metal based pharmaceutical development [53-62]. Extensive investigations on the coordination chemistry of hydroxymethyl phosphines have demonstrated unique stereospe-cific and kinetic propensity of this class of water-soluble phosphines [53-62]. Representative examples outlined in Fig. 4, depict bidentate and multidentate coordination modes and the unique kinetic propensity to stabilize various oxidation states of metal centers, such as Re( V), Rh(III), Pt(II) and Au(I), in aqueous media [53 - 62]. Therefore, the importance of functionalized primary phosphines in the development of multidentate water-soluble phosphines cannot be overemphasized. 

No new silicon-transition metal bonds are formed in these reactions, although new compounds containing such bonds are produced. Details are in Section II,C,l-3. 

It has been noted (Section II,B,1) that reactions between transition metal carbonyl anions and silicon halides often fail to produce species containing silicon-transition metal bonds, and that such failure has been ascribed to nucleophilic attack by carbonyl oxygen. It is therefore interesting that compounds containing Si—O—C—transition metal linkages have recently been isolated from such reactions [Eqs. (105) (R = Me, Ph) 183) and (106)... 

Colomer, E., and Corriu, R. J. P. Chemical and Stereochemical Properties of Compounds with Silicon or Germanium-Transition Metal Bonds, 96, 79-110 (1981). 

Although there are a lot of publications on the chemistry of technetium [2-4] and transition-metal clusters [1,5-8], the chemistry of technetium clusters was insufficiently studied until the early eighties [1,2]. Nevertheless, the available scanty data on the compounds with Tc-Tc bonds inspired hope that interesting results would be obtained in the chemistry of technetium in general, in radiochemistry, and in the chemistry of transition-metal cluster compounds. The anticipated results were actually obtained [9-15] and the conclusion was drawn that technetium had a number of anomalous cluster-forming properties [9]. This review looks at the detailed studies of these properties and their interpretation in terms of electronic structure theory. 

The cis-trans isomerization of alkenyl ligands in transition metal alkenyl compounds is proposed to occur via zwitterionic carbene intermediates.46 According to this, the low contribution of the form b to the metal-dienyl bond in Os (Z)-CH=CHC(Me)=CH2 K1-0C(0)Me (C0)2(P,Pr3)2 could explain why this compound does not evolve into its (if )-isomer. 

All compounds described in this report have been well characterized by means of IR and NMR spectroscopy. Most valuable is the coupling constant J(WSi) which, as has been demonstrated for J(WP) [17], can be correlated with the s-electron density of the main group element transition metal bond (e. g. J(WSi) = 44.7 Hz (21i), 71.1 Hz (22b)). Related studies concerning metallo-silanols and siloxanes with other metals of groups 6 and 8 are in progress. 

Attempts to synthesize transition metal alkyl compounds have been continuous since 1952 when Herman and Nelson (1) reported the preparation of the compound C H6>Ti(OPri)3 in which the phenyl group was sigma bonded to the metal. This led to the synthesis by Piper and Wilkinson (2) of (jr-Cpd)2 Ti (CH3)2 in 1956 and a large number of compounds of titanium with a wide variety of ligands such as ir-Cpd, CO, pyridine, halogen, etc., all of which were inactive for polymerization. An important development was the synthesis of methyl titanium halides by Beerman and Bestian (3) and Ti(CH3)4 by Berthold and Groh (4). These compounds show weak activity for ethylene polymerization but are unstable at temperatures above — 70°C. At these temperatures polymerizations are difficult and irreproduceable and consequently the polymerization behavior of these compounds has been studied very little. In 1963 Wilke (5) described a new class of transition metal alkyl compounds—x-allyl complexes,... 

The results of polymerizing ethylene using varying sigma-bonded transition metal alkyl compounds are summarized in Table VII. It is evident that none of the catalysts are very active and are comparable with the simple allyl compounds listed in Table I. 

Some of the vinyl monomers polymerized by transition metal benzyl compounds are listed in Table IX. In this table R represents the rate of polymerization in moles per liter per second M sec-1), [M]0 the initial monomer concentration in moles per liter (M) and [C]0 the initial concentration of catalyst in the same units. The ratio i2/[M]0[C]0 gives a measure of the reactivity of the system which is approximately independent of the concentration of catalyst and monomer. It will be observed that the substitution in the benzyl group is able to affect the polymerization rate significantly, but the groups that increase the polymerization rate toward ethylene have the opposite effect where styrene is concerned. It would also appear that titanium complexes are more active than zirconium. The results with styrene and p-bromostyrene suggests that substituents in the monomer, which increase the electronegative character of the double bond, reduces the polymerization rate. The order of reactivity of various olefinically unsaturated compounds is approximately as follows ... 

Transition metal alkyl compounds react with the -OH groups on the surface of silica in a manner similar to that described for the silanol [reaction (13)] and as with the latter more than one type of bonding is possible. Silica dried at 200°C reacts with Zr(allyl)4 to give two molecules of propene per metal atom and utilizing in the course of this process two -OH groups per metal atom. The chemistry of the process is accurately described by the equation... 

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