Triple-decker sandwich

Figure 27.13 The triple-decker sandwich cation, [Ni2(>j -C5H5)3]+. Note that the C5H5 rings are neither staggered nor eclipsed , and the nickel atoms are closer to the outer than to the central ring.

Figure 80 The structure of the triple-decker sandwich complex (CsPryBatCOTJBafCsPr s) 153.

Bocian, Lindsey and co-workers studied sandwich complex nanocapacitors comprised of porphyrin and phthalocyanine ligands separated by lanthanide metals [133]. A triple-decker sandwich of phthalocyanine-Eu-phthalocyanine-Eu-porphy-rin, with two phenylethynyl linker wires from the porphyrin, potentially has up to nine accessible oxidation states (—4 to +4). SAMs of monomers, dimers, trimers, and oligomers of this sandwich, anchored at one or both ends by thioacetyl groups, gave charge densities up to 10 10 mol cm-2, electron-transfer rates up to 105 electrons s-1, and charge-dissipation half-lives in the 10-50 s range. 

Mononuclear and Dinuclear Complexes of C4B Rings (Double-Decker and Triple-Decker Sandwiches)... 

Dinuclear C4B complexes (triple-decker sandwiches and dimers)... 

RR R"C3B2Me2)Ni](RR R"C3B2Me2) Ni(RR R"C3B2Me2) Theoretical studies Molecular and electronic structure calculations Triple-decker sandwiches S, EXAFS, thermogravimetry, differential calorimetry, electrical conductivity 44... 

C3B2 Ring Triple-decker Sandwiches and Dimers... 

Species functionalized at boron, such as 50-53, have also been prepared from the corresponding MC2B4 closo clusters via the removal of the apex BH unit (decapitation) with I M Kl)A.54 57 The same approach has been employed to link CoC2B3 units to benzene or other arenes 5 As shown in the following subsection, di- and trinuclear complexes such as 53 and 54 are easily converted to multi-triple-decker sandwich systems. 

Triple-decker sandwiches that are capped at one or both ends by C2B3 rings are important synthons for the construction of larger stacks via coordination to metal ions (see the following subsection), and many of these have been synthesized and their reactivity investigated.75,78 Bent triple-deckers such as 6879,80 that resemble bent metallocene complexes have been prepared, structurally characterized, and shown to be amenable to the introduction of halo- and organosubsitutuents at boron.80... 

Triple-decker sandwiches of type 69 containing central metal-metal linkages have been synthesized.76... 

Serendipitous insertion of CsHs- into the metallaborane Cp 2Cr2B4Fl8 gave the triple-decker sandwich 122 in low yield.140 This compound can be described as an eight-vertex Cr2C2B4 c/ara-metallacarborane cluster, and its preparation is notable as one of the few examples of metallacarborane synthesis from a metallaborane precursor (rather than by the usual metal insertion into a carborane), an approach first demonstrated by Grimes and co-workers in the 1970s.34,141,141a... 

Phosphoratabenzene complexes of the type LM[H2Me2C4PB-N(CFIMe2)2] (L = (CO)3Mn or Cp Ru) have been prepared by Ashe et at.152 Double- and triple-decker sandwiches 133-135 were obtained by Siebert and co-workers from the reaction of the diborole complex 33 (Section 3.01.3.2) with elemental phosphorus.36 The structures of these complexes have not yet been confirmed crystallographically, and the proposed triple-decker 135 has been seen only in the mass spectrum of 134. 

The cyclo-P3 unit can also behave as a three electron bridging ligand (45) to give a variety of homo and heterometallic triple-decker sandwich complexes which are treated in a recent review (100). 

The only complex containing a complete cyclopentadienyl ring sandwiched between 2 metal atoms that has been the subject of an X-ray crystallographic study is the triple-decker sandwich compound... 

Fio. 26. The triple-decker sandwich structure of cation [(CsHslNilCsHg)-Ni(C5H5)]+ (66, 176). 

A typical structure of these so called triple-decker sandwich complexes is that of the complex [(p3)Ni -(j)3-P3) Ni(p3)](BPh4)2-2.5Me2CO (73). In each complex the trihapto P3 (or trihapto As3) groups form a bridge between the two Ni(p3) residues.292 Each nickel atom is thus six-coordinated by three phosphorus atoms from the ligand p3 and by three phosphorus atoms from the cyclo-P3 (or arsenic atoms from the cyclo-As ), which acts as a three-electron-donor ligand. 

Dicobalt octacarbonyl, in Pauson—Khand reaction homogeneous catalysis, 11, 340 metal-coupled promoters, 11, 339 non-oxidative promoter-assisted, 11, 338 oxidative promoter-assisted, 11, 337 physical promoters, 11, 339 solid-supported promoters, 11, 339 Dicobalt triple-decker sandwiches, preparation, 3, 14 (+)-Dictamnol, via [5+2]-cycloadditions, 10, 613-614 Dicyclohexylborane, for alkene hydroboration, 9, 150... 

Following the preparation of 4.79, a number of other cyclic mercury crown compounds have been synthesised, which do exhibit halide complexation behaviour. Compound 4.80, forms a 1 1 polymer with bromide in the solid state in which the Hr anions perch above the Hg3 plane. The Hg—Br distances of 3.07-3.39A are considerably longer than normal Hg—Br covalent bonds (about 2.54A).61 The compound also binds SCN- with similarly long bonds as shown in Figure 4.34.60 The analogous chloride complex has a 3 2 stoichiometry suggesting a triple-decker sandwich of type [4.80 Cl 4.80 Cl 4.80]2. ... 

In the case of "simple sandwich complexes the X-ray diffraction studies have shown that the M-PCtriphos), M-P(cyclo) and P-(cyclo)-P[cyclo) distances reveal effects of both the increase in the principal quantum number and the "lantanide contraction". For "triple decker sandwich complexes the li-li distances increase whereas the P[cyclo)-P(cyclo) distances decrease with increasing number of valence electrons. 

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