Crystal structure Substitution derivatives

Cinellu, M.A., Zucca, A., Stoccoro, S., Minghetti, G., Manassero, M. and Sansoni, M. (1995) Synthesis and characterization of gold(III) adducts and cyclometallated derivatives with 2-substituted pyridines. Crystal structure of [Au NC5H4(CMe2C6H4)-2 Cl2]. Journal of the Chemical Society, Dalton Transactions, (17), 2865. 

Zhu, Z., Cameron, B.R. and Skerlj, R.T. (2003) Cycloauration of substituted 2-phenoxypyridine derivatives and X-ray crystal structure of gold, dichloro[2-[[5-[(cyclopentylamino)carbonyl]-2-pyridinyl- N]oxy]phenyl- C]-, (SP-4-3)-. Journal of Organometallic Chemistry, 677, 57. 

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

This magnetic behavior is very sensitive to the chemical structure of the spin carrier and to the crystal packing. For instance, for the para-nitro substituted derivative, Nit(p-NO )Ph, which crystallizes in four different phases, the p phase only orders ferromagnetically (Tc = 0.6 K) [8,9], Moreover, attaching the nitro group in the meta-, rather than the / ara-position of the phenyl, leads to an antiferromagnetic compound [2],... 

Silver(I) complexes are known with the tris(pyrazolyl)borate [HB(pz)3] and the methyl, phenyl, bromo, or trifluoromethyl-substituted derivatives. The structure of the silver tri(pyrazolyl)borato species has been a puzzle since it was first reported.385,386 It was suggested that the structure could be oligomeric, but recently the crystal structure of the compound [Ag HB(3,5-Me2pz)3 ]2 shows that it has a dimeric structure387 where the silver(I) centers are tricoordinated by a bidentate arm of one ligand and a monodentate arm of the other ligand (29). The related complexes [Ag HB(4-Brpz)3 ]2, [Ag HB(4-Mepz)3 ]2, [Ag HB(3,5-Me2pz)3 ]2, [Ag HB(3-Mepz)3 ] , [Ag B(pz)4 ], and... 

In contrast to 1, the related pure host 7 may be obtained in crystalline form 68). The crystal structure of 7 is built via helical chains of alternating intra- and inter-molecular H-bonding through the carboxyl functions. This structure supplies the information that the carboxyl groups are therefore already positioned in an appropriate way to facilitate analogous H-bonding in the known inclusions of 7. As discussed later (Sect. 4.2.2), these are exclusively salt-type associates and as such, intimately interact with the carboxyl groups. Hence one may infer that displacement of the carboxyl functions from position 2 in 1 to position 8 in 7 reduces the ability of inclusion formation. Similar reasons such as the solid-solubility differences observed in the classical naphthalene/chloronaphthalene systems (alpha- vs. beta-substituted derivatives, cf. Ref. 28 may also be applied here. 

Though molecules l and 7 are closely connected in structure, they have totally different host properties, i.e. 1 readily forms inclusion compounds with a wide variety of guests (see Sect. 3.2.2) while 7 does not. For example, crystals of the pure host could be obtained from dimethylformamide, a solvent which is tightly held by /. Reasons for the different behavior of 1 and 7 have already been mentioned when the crystal structure of the free host 7 was discussed (Sect. 4.1). However, the ability of 7 to form a crystalline associate is increased, if a solvent with the property of a base is present, e.g. pyridine and substituted derivatives of pyridine (see Table 14)80). 

The effect of structural variation on crystal structure was studied for 12 phenyl-substituted derivatives of 6-amino-2-phenylsulfonylimino-l,2-dihydropyridine [37], The title compound contains both hydrogen bond donor and acceptor sites, and the... 

Over the past decade a number of new covalently bonded TTF/ferrocene adducts have been reported [77, 78]. The crystal structure of the l,l -bis(l,3-dithiole-2-ylidine)-substituted ferrocene derivative has been published [77]. In this complex, ferrocene has essentially been incorporated as a molecular spacer between the two l,3-dithole-2-ylidene rings forming a stretched TTF molecule. This adduct, and its methyl-substituted derivative, have been combined with TCNQ to form charge-transfer complexes with room temperature powder conductivities of 0.2 S cm-1. Similar diferrocenyl complexes have been prepared with bis (dithiolene) metal complexes [79, 80]. 

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 molecular structures of 39c,e in the crystals show that the B-B and B-C distances of the C2B3 frameworks are considerably shorter than those of boron-amino-substituted derivatives [56], which are described as bicyclo-organoboranes. 

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