Piano stool compounds

Organometallic half-sandwich piano stool compounds Cp M and/or (arene)M as building blocks for supramolecular chemistry (reprinted with permission from reference " ). 

A number of cyclopentadienyl-ffee amidoAn -cyclooctatetraene complexes have been reported. Sattelberger s group found that [An(cot)Cl2(thf)2] with 2Na[N(SiMe3)2] in toluene yielded the crystalline [An(cot) N(SiMe3)2 2], which for An = Th was X-ray-characterised as a four-legged piano stool , with the Th- -Centroid distance of 2.04 A, each amido ligand having one short Th- - -C contact (3.15 or 3.04 A). The compounds [U(cot)-... 

Compounds of the type [MoXCp(NO)2] (Cp = rj5 - C5H5 or Tj5-C5Me5) and [MoX(Rpzb)(NO)2] are also known (Rpzb- = anion tris(2-pyrazolyl)(R)borate)18,22 and are monomeric in solution, the Cp derivatives having the three-legged piano stool structure (see 5).18,19... 

In a few cases, the stereochemistry of adducts has been elucidated from their vibrational and NMR spectra. The arrangement in compound (IV) has already been displayed, the product of the reaction in entry 30 is known to be (V) (223) [and this is confirmed by an X-ray study of the GeMe3 analog (202)], while the product in entry 33 is (VI) (229). The adduct Ph3SiMnH(CO)2(Cp) (entry 4) adopts a piano-stool... 

The ruthenium compound in entry 11 has a piano-stool structure (LXIII), and hindered rotation about the Ru-aromatic ring bond may... 

A family of molecular rotors (e.g., compound 4 in Fig. 17.4 a) has been designed to perform rotation under electrochemical stimulation.59 60 The molecules have a piano-stool structure with a stator meant to be grafted on an oxide surface and a rotor bearing redox-active groups, so that addressing the molecule with nanoelectrodes would trigger rotation (Fig. 17.4 b). To avoid intramolecular electron transfer between two electroactive units, which would compete with rotation, insulating... 

Bonding in sandwich compounds such as ferrocene arises through interaction of the delocalised p MOs of the ring with orbitals of the metal, and cannot be treated in a localised fashion. As in alkenes, both donor and acceptor interactions are involved. Other ligands such as CO can be present, as in the piano-stool structure 5 or the metal-metal bonded dimer 6. 

As has been described, the parent monocarbollide-metal carbonyl piano-stool species 2-(CO)n-closo-2,1 -MCB,0II n] are now known for all of the metals M = Mo (12), W (13), Re (14), Fe (11), Ru (6), Os (8), and Ni (18). Evidence also exists for a dicarbonyl-platinum analogue of compound 18,20 and as mentioned earlier, the manganese analogue of 14 has also briefly been reported.3a A notable absence from this list, however, is any representative of the Group 9 metals. The carbonyl nitrosyl-cobalt complex 21 is very closely related to the hitherto unknown dicarbonyl-cobalt dianion [2,2-(CO)2-< 7<9.v<9-2,1 -CoCB10H 11]2 and this species remains an attractive synthetic target. 

The neodymium compound [( -C6H5Me)Nd N(C6F5)2 3] has a -bonded toluene molecule with a distorted piano-stool geometry. 

Simple cyclooctatetraenediyls [M(C8H8)] (M = Eu, Yb) can be made by reaction of cyclooctatetraenewith solutions ofthe metal in liquid ammonia. Another route to [M(CsH8)] (Sm, Yb) is the reaction of the metals with cyclooctatetraene using iodine as catalyst. These compounds are not monomers, but the Lewis base adduct [M(C8H8)(py)3] has a piano-stool structure. 

This compound has a piano-stool-type structure (Figure 13.17). 

There are very few examples of MOFs that have organometallic complexes as metalloligands, or so-called organometalloligands . However, Sweigart and co-workers (139-144) studied a number of such compounds. Their organo-metalloligand of choice was the piano stool complex [(Tj -benzoquinone)Mn (CO)3] , or /i-QMTC (Fig. 33). The C=0 moieties of the quinones can associate to secondary metal centers to form supramolecular networks with a rich diversity of... 

---