Mixed sandwich complexes

When the reaction is carried out in the presence of NaCsHs the purple mixed sandwich complex (83) is obtained ... 

The five-membered heterocycle Et2C2B2Mc2S reacts with 17 -CpM fragments (M = Ni, Co) from [Tj -CpNi(CO)2]2 and i) -CpCo(CO)2 to form mixed sandwich complexes of the type rj -CpM(Et2C2B2MeS) , whereas Ni(CO>4 yields the bis(di-hydrothiadiborol) complex. The (Et2C2B2Me2S)Ni(CO)2 is formed in the first step. 

On treatment with T1C1, alkali metal boratabenzenes afford the corresponding T1 compounds (51). The lower reactivity of these can be essential for some syntheses. Some of the rare cationic borabenzene complexes 35-37 could be made using thallium boratabenzenes as reagents. Similarly, (C4Me4)Co(CO)2I yielded the mixed sandwich complexes 38 and 39 in excellent yields (71). 

Consequently, in Figures 5-11 are shown the appropriate Tanabe-Sugano type diagrams for dx systems (x = 2 — 8) in pseudo-axial, CmV, symmetry, the parameters DtjDs = 0.55 and C/B = 4.0 being adopted throughout. As indicated above this parameteri-sation is most appropriate for the metallocenes, for which the d-d spectra are now considered in more detail. Thereafter a brief survey is made of the limited data relating to bis-arene species, and to various mixed sandwich complexes. 

In principle it should be possible to determine the anisotropy of the paramagnetic susceptibility for some systems of pseudo-axial symmetry, but apart from the citation (74) of a private communication regarding the ferricenium cation, no experimental data are available for metal sandwich complexes. Such measurements should however be possible for at least some metallocenes and mixed sandwich complexes since these are found to crystallise in either a monoclinic (Fe(Cp)2 (6)) or orthorhombic (Ru(Cp)2, (Cp)V(Ch),... 

Interestingly, the structural parameters for the individual pz and porphyrin subunits of the mixed sandwich complex are indistinguishable. Selected bond lengths and angles for sandwich compounds (29), the heteroleptic system (30), and the homoporphyrin analogue are listed in Table VI (33). 

The organometallic chemistry of the first-row transition metals generally starts with the binary metal carbonyl organometallic complexes. Noncarbonyl organometallic complexes starting with other easily accessible binary compounds provide entries to a broader spectrum of complexes. In this context, we describe the synthesis of the mixed sandwich complex (tj5-pentamethylcyclopentadienyl) ( j5-cyclopentadienyl) iron as an example of the synthetic utility of the solution-stable derivative (>j5-pentamethyl-cyclopentadienyl) (2,4-pentanedionate) iron. 

Mixed-sandwich complexes with cyclodextrins, 12, 787 iridium cyclopentadienyl complexes, 7, 368 with nickel, synthesis and reactivity, 8, 160 with vanadium, 5, 47... 

Mixed-sandwich complexes could be synthesized by adding cyclopentadie-nide ion to the reaction mixture (38, 48). 

Synthetic routes leading to two series of (COT)lanthanide(III) scorpio-nate mixed sandwich complexes were reported. The early lanthanide derivatives (COT)Ln(Tp) and (COT)Ln(TpMe2) (Ln = Ce, Pr, Nd, Sm) were obtained by reacting the dimeric halide precursors [(COT)Ln(p-Cl)(THF)]2 with KTp or KTpMe2. For small lanthanide ions (COT)Ln(Tp) (Ln = Er,... 

Rh(f 5-Gp )(10S3)](PF6)2-2CH3NO2 Cp = Mes-cyclopentadienyl mixed sandwich complex 2005JOM(690)629... 

C2B9H9R2]2Cr and [(3)-l,7-C2B9Hii]2Cr. If the reaction is carried ont in the presence of CsHs", one obtains the nentral mixed-sandwich complexes (jj -C5H5)Cr[(3)-... 

Cyclooctatetraenyl lanthanide(III) halides of the type [(COT)Ln(/x-Cl)(THF)2]2 (Figure 77a) are the most important precursors for the preparation of other half-sandwich (see Half-sandwich Complexes) and mixed sandwich complexes with cyclooctatetraenyl ligands. These complexes are readily accessible by reacting anhydrons lanthanide trichlorides with K2[C0T] in a molar ratio of 1 1. The compounds consist of centrosyimnetric, chloro-bridged dimers with... 

The solution behavior of these mixed sandwich complexes was studied by H and 13C H) NMR techniques. Due to the Cs symmetry or lower of these mixed complexes the expected number of resonances should be 2 (Q) or 4 (lower symmetry). In Table 2 the H and i3C H) NMR pyrrolyl resonances are indicated. All mixed sandwich complexes... 

By 1957, a variety of both 7r-cyclopentadienyl and arene-metal complexes was known, and it was interesting to determine whether mixed-sandwich complexes containing both of these ligands around the same could be produced. Two early examples of such complexes are given below ... 

A variety of organometallic, ir complexes are now known, in which both TT-cyclopentadienyl and ir-cycloheptatrienyl ligands are bonded simultaneously to the same transition metal, providing a series of unique mixed sandwich complexes. The first of these, x-cyclopentadienyl-x-cyclo-heptatrienyl-vanadium (XXXI), was described by King and Stone (153)... 

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