Cyclopentadienyls crystal structures

The structure of the metallocene cation energy minimised with the Car-Parrinello method agrees well with the experimentally obtained crystal structures of related complexes. Typical features of the structure as obtained from X-ray diffraction on crystals of very similar neutral complexes (e.g., the dichlorides), such as small differences in distances between C atoms within a cyclopentadienyl (Cp) ring, as well as differences in distances between the C atoms of the Cp ring and the Zr atom, were revealed from the simulations. 

Reagent 7 is easily prepared from commercially available diacetone-D-glucose and trichloro(cyclopentadienyl)titanium35 (Section 1.3.3.3.8.1.). The monomeric structure of reagent 7 was confirmed by an X-ray crystal structure analysis1 7. Complex 9 is obtained36 analogously from (7 .7 )-tartaric acid derived (R,7 )-2,3-CMsopropylidene-l,l,4,4-tetraphenyl-1,2,3,4-butanetetrol. 

Berndt, A. F. Marsh, R. E. (1962) The crystal structure of cyclopentadienyl manganese tricarbonyl, C5H5Mn(CO)3, Acta Crystallogr. 16,118-123. 

The crystal structure of a mono(cyclopentadienyl)zirconium complex containing a novel Me2Si-linked bis(amidinate) ligand was reported (Scheme 203). In this compound the central Zr atom is octahedrally coordinated with the bis(amidi-nate) acting as a tridentate ligand. ... 

The crystal structure of [Cu(Me2dtc)2] shows that it possesses a center of S3rmmetry, with the copper octahedrally co-ordinated to six S atoms, two Cu-S bonds being longer than the other four (424). Choi and Wasson (425) showed that there is only Cu-S bonding in [Cu(acdc)2] (acdc = 2-amino-l-cyclopentadienyl-l-dithiocarboxylate). 

Both dialkynylated cymantrenes 16 and 17 have the same symmetry and similar NMR spectra, so that the ultimate structure elucidation had to rest upon X-ray crystallography. It was reasoned that the dialkynylcymantrene with the smaller /(H,H) coupling of the cyclopentadienyl protons should be 17, an interpretation reinforced [23 a] by the result of the single-crystal structure. 

The crystal structures of P-hydrogen and P-cyclopentadienyl NHPs are likewise distinguished by the presence of elongated P-H and P-C bonds. Based on support... 

Monomeric carbene complexes with 1 1 stoichiometry have now been isolated from the reaction of 4 (R = Bu, adamantyl or 2,4,6-trimethylphenyl R = H) with lithium l,2,4-tris(trimethylsilyl)cyclo-pentadienide (72). The crystal structure of one such complex (R = Bu) revealed that there is a single cr-interaction between the lithium and the carbene center (Li-C(carbene) 1.90 A) with the cyclopentadienyl ring coordinated in an if-fashion to the lithium center. A novel hyper-valent antimonide complex has also been reported (73). Thus, the nucleophilic addition of 4 (R = Mes R = Cl) to Sb(CF3)3 resulted in the isolation of the 1 1 complex with a pseudo-trigonal bipyramidal geometry at the antimony center. 

Vinylboronates are generally less reactive than vinylzirconocenes towards various electrophiles and hence selective reactions of the latter should be possible. It was found that selective cleavage of the carbon—zirconium bond in 45 by N-halosuccinimides provides (a-haloalkenyl)boronic esters 53 in excellent chemical yields and with complete re-gioselectivity (Scheme 7.17) [54], An X-ray crystal structure determination of 45 confirmed the configuration of the four-coordinate Zr complex, with two cyclopentadienyl rings, Cl, and C(sp2) as the four ligands (Fig. 7.5) [54,126]. 

Figure 7.8. Crystal structure of the novel zirconacyclopentadiene complex, 8,8-bis(cyclopentadienyl)-7,9-bis-(trimethylstannyl)-8-zirconabicyclo[4.3.0]nona-l (9),6(7)-die ne 109. Adapted by the authors.

Another complex involving the formation of a cyclopentadienyl unit is obtained from the interaction of ethyl or propyl acetylene with Fe3(CO)i2 117). The products contain the complexes Fe3(CO)7(HC2R)4 (R = Et, re-Pr), and the crystal structure of the ethyl derivative indicates the presence of the substituted 1,2,3-triethylcyclopentadienyl group bonded to one iron center with an ethylallyl group cr- and n-bonded to the three metal centers. The formation of adducts of this type must involve the fission of the C=C bond of the acetylene. 

The crystal structure of the bromide complex of [78] has been elucidated and clearly shows bromide anions hydrogen-bonded to the amide N—H groups and, interestingly, also to the cyclopentadienyl hydrogen atoms (Fig. 40). 

The X-ray determination of crystal structure of tetracyclopentadienyl-hafnium has established that the molecule should be represented as [(7r-Cp)2-Hf(Cp)2], and thus resembles the titanium rather than the zirconium analogue. Both [(7i-Cp)2Hf(Cp)2] and [(it-Cp)2Zr(Cp)] exchange nonequivalent cyclopentadienyl rings very easily such that, even at — 150°C, only one sharp line is observed in the H n.m.r. spectrum. ... 

A cyclopentadienylmagnesium bromide containing a heteroatom-functionalized substituent at the cyclopentadienyl group has also been structurally characterized. When l-[2-(dimethylamino)ethyl]-2,3,4,5-tetramethylcyclopentadienylmagnesium bromide is recrystallized from dichloromethane, dimeric [(Mc2N(CH2)2)Me4C5MgBr]2 (206) (Figure 88) is obtained. Its X-ray crystal-structure determination reveals a structure in the solid state... 

In a similar way Cp(Me)Mg(OEt2) is capable of deprotonating iV,Ai -bis(2,4,6-tri-methylphenyl)(ierr-butyl)amidine to form the corresponding cyclopentadienylmagnesium amidinate complex (226) (equation 17). An X-ray crystal-structure determination of 226, of which the structure is shown schematically (equation 17), showed that this compound also exists as a monomer in the solid state. Like in 225 the cyclopentadienyl group is /7 -bonded to magnesium while the amidinate anion is Ai,A -chelate bonded with almost equal Mg—N bond distances [Mg-N 2.090(2) and 2.097(2) A]. Furthermore, an additional... 

The cyclopentadienyl /3-diketiminate 249 and its 4-terf-butylpyridine adduct 250 have been prepared and structurally characterized (equation 19). An X-ray crystal-structure determination of 249 showed that the cyclopentadienyl group is /j -bonded to magnesium. On the basis of the observed bonding parameters of magnesium with the -diketiminate skeleton [Mg-N 2.006(2) and 2.021(2) A, Mg-C 2.729(3) and 2.826(3) A and Mg-C 2.689(3) A] this bonding is described in terms of a jr-interaction. However, in 250 the /3-diketiminate is iV,iV -chelate bonded to magnesium. 

Early and late transition metal combinations were explored by Casey [71] and many others. Reaction of the bis(phosphinomethyl) complex Cp2Zr(CH2PPh2)2 (Cp = cyclopentadienyl) on Rh(H)(PPhj)4 gave the bimetallic hydride Cp2Zr (CH2PPh2)2Rh(H)(PPh3) (30), the crystal structure of which was determined [72],... 

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