Cyclopentadienyl complexes, heteroleptic

A stabilized heteroleptic germanium cyclopentadienyl complex was obtained which has an extremely long (2.369(1) A) Ge-Cl bond and an 2-bound Cp ring (Equation (238)).309... 

C5H4(SiMe3)]2Y(OfBu)2Li(thf)2+Y[N(SiMe3)2]3 Scheme 17. Ligand redistribution in a heteroleptic cyclopentadienyl complex... 

Two equiv. of 6,6-di(cyclopropyl)fulvene react at 60 °C over a period of a week with Ca[N(SiMe3)2]2-(THF)2 bis in THF to yield the metallocene 170. The heteroleptic amido complex 171 is detected as an intermediate with 111 and 13C 1H NMR spectroscopy. A 1 1 reaction of the calcium amide and 170 also produces 171 in solution, an equilibrium involving these three derivatives exists (Equation (30)). The calcocene 170 crystallizes at — 20 °C from THF as colorless cuboids. The metal center is surrounded by the four ligands in a distorted tetrahedral manner, and the cyclopentadienyl group and the propylidene fragment are coplanar with each other.393... 

Hydrocarbonyl compounds, lanthanide complexes, 4, 4 ( -Hydrocarbyl)bis(zirconocene), preparation, 4, 906 Hydrocarbyl-bridged cyclopentadienyl-amido complexes, with Zr(IV), 4, 864 Hydrocarbyl complexes bis-Cp Ti hydrocarbyls reactions, 4, 551 structure and properties, 4, 551 synthesis, 4, 542 cobalt with rf-ligands, 7, 51 cobalt with rf-ligands, 7, 56 cobalt with ]4-ligands, 7, 59 cobalt with rf-ligands, 7, 71 heteroleptic types, 4, 192 homoleptic types, 4, 192 into magnetic metal nanoparticles via ligand stabilization, 12, 87 via polymer stabilization, 12, 87 into noble metal nanoparticles... 

As can be seen from Scheme III, lanthanide halides are suitable precursors for the synthesis of homoleptic derivatives such as silylamides [114], cyclopen-tadienyls [115] and aryloxides [116]. Such organometallies can be readily obtained in a pure form by sublimating them from the reaction mixture. They themselves are important precursors in organometallic transformations (vide infra). Heteroleptic complexes of the type CpxLn(halide)y (x + y = 2,3) are important synthetic precursors with respect to formation of various Ln-X bonds via simple metathesis reactions [2-29]. Fig. 4 indicates the lanthanide element bonds which are involved in these ubiquitous heteroleptic cyclopentadienyl systems. 

A few classic heteroleptic complexes were sythesized involving additional lanthanide iodide [146], cyclopentadienyl [147,149], amide [141], alkoxide... 

The other isolable molecular compoimds of uncommon divalent rare earths have been imtil now mostly organometallic complexes featuring cyclopentadienyl ligands or cyclopentadienyl "equivalents" such as pyrazolylborates. The vast majority of characterised compounds contain Tm", the less reactive of the uncommon divalent rare earths (which unfortunately is also the most expensive). Many other stable compounds seem within reach, given that a good steric protection is achieved, such as for instance amides or alkoxides. Also, it may be possible to synthesise more heteroleptic complexes such as LR°I with an open coordination sphere, which could lead to a very rich new chemistry. A pending question finally involves the possibility of finding yet other complexes of rare earths in new divalent states (for instance Y " "). 

In addition to the heterobinuclear complexes Ph3PAuM(CO)Y (M = Co, Mn, V), heteroleptic cyclopentadienyl carbonyl complexes Ph3PAuM(Cp)(CO).Y can be used... 

The vanadium group element homoleptic compounds with uM —C bonds are relatively thermally unstable and very sensitive to oxidizing agents and water. They also have the tendency to expand the coordination number as a result of R" or Lewis base (amine, phosphine, etc.) addition. Heteroleptic complexes possessing cyclopentadienyl, halogen, 0x0, acetylacetonate, etc., ligands are usually more thermally stable than homoleptic complexes such as MR4. 

Fieser ME, Bates JE, ZiUerJW, Furche F, Evans WJ. Dinitrogen reduction via photochemical activation of heteroleptic tris(cyclopentadienyl) rare-earth complexes. 

Figure 4.63. Molecular structures of commonly used CVD precursor classes. Shown are (a) metal p-diketonate (acetylacetonate, acac) complex to grow a metal oxide film (H2 as the coreactant gas yields a metal film) (b) a heteroleptic (more than one type of ligand bound to the metal) p-diketonate complex to yield a Cu film the ancillary ligand helps prevent oligomerization, enhancing volatility (c) various types of complexes to deposit metalhc, oxide, nitride, or oxynitride films (depending on coreactant gas(es) used - respective ligands are p-ketoiminato, P-diketiminato, amidinato, and guanidinato (d) a metal azolato complex commonly used to deposit lanthanide metal films metal cyclopentadienyl (cp) complexes, (e), and dialkylamido complexes, (f), are often used to deposit a variety of metallic or compound thin films.

To prepare heteroleptic tricyclopentadienides the displacement of chlorine in LnCl3 by cyclopentadienyl rings with different substituents are carried out in a stepwise manner. This way has been employed specifically to synthesize a series of complexes with cyclopentadienyl rings bonded by an etiher group -CH2CH2OCH2CH2- [98]. These reactions can be conducted without isolation of intermediate monochloride ... 

All compounds of the Ln(ER)3 type (Table IX. 1) are insoluble in common organic solvents that proves, evidently, their associative nature. Heteroleptic complexes [(Me3Si)2N]3. Ln(SR)j, as well as the cyclopentadienyl derivatives dissolve in THE, aromatic hydrocarbons. In the series of [(Me5C5)2Yb]2( X-E) (E=0,S,Se,Te) the solubility increases from the oxide to the telluride which is very soluble in hexane. 

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