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1、Silver and Gold Trinuclear Complexes Based on 3-Substituted or 3,5-Disubstituted Pyrazolato Ligands. X-Ray Crystal Structure of cyclo- Tris?-3,5-bis(4-phenoxyphenyl)-1H-pyrazolato-? ?N1:? ?N2trigold Dichloromethane (Au(?-pzpp2)3CH2Cl2)by M. Carmen Torralbaa), Paloma Ovejeroa), M. Jose Mayorala), Mer
2、cedes Cano*a), Jose A. Campoa), Jose V. Herasa), Elena Pinillaa)b), and M. Rosario Torresb)a) Departamento de Qumica Inorga nica I, Facultad de Ciencias Qumicas, Universidad Complutense,E-28040 Madrid (e-mail: mmcanoquim.ucm.es) b) Laboratorio de Difraccio n de Rayos-X, Facultad de Ciencias Qumicas,
3、 Universidad Complutense,E-28040 MadridTen new silver and gold trimeric complexes of the type M3(?-pz?)3 (M?Au, Ag), where pz? indicate pyrazolato ligands derived from mesogenic 3,5-disubstituted 1H-pyrazoles HpzR2or non-mesogenic 3- substituted 1H-pyrazoles HpzR(R?C6H4OCnH2n?1), were synthesized an
4、d characterized. The gold and silver complexes 7, 8, 10, and 11 containing symmetric pyrazolato ligands as bridging groups (pzR2; R?C6H4OCnH2n?1, n?4 (pzbp2) and 8 (pzop2) exhibited a trigonal symmetric structure. The same results were obtained for the related silver derivatives 1618 with 3-substitu
5、ted pyrazolato ligands (pzR; R?C6H4OCnH2n?1, n?4 (pzbp), 12 (pzddp), and 18 (pzodp). By contrast the 3-substituted pyrazolato-gold compounds 1315 adopted an asymmetric molecular structure related to the position of the substituents on the trinuclear core. The thermal behavior of these complexes was
6、investigated by differential scanning calorimetry and polarized-light microscopy. The mesomorphism of the parent 3,5-disubstituted pyrazoles is avoided in their corresponding trinuclear complexes 7, 8, 10, and 11. However, the metal derivatives 14 and 17 containing the asymmetric 3-4- (dodecyloxy)ph
7、enylpyrazolato ligand were found to have liquid-crystal properties. These compounds exhibited monotropic behavior with columnar mesophases that could be related to the disc-like shape of the molecular core and the appropriate length of the alkyloxy chain. For comparative purposes, the X-ray structur
8、e of the related gold complex Au3(?-pzpp2)3 (9) having phenoxyphenyl substituents at the 3- and 5-positions of the pyrazolato ligand is also described. The molecular structure is formed by a non-planar (Au?N?N)3core, containing three Au-atoms bridged by three pyrazolato ligands. The molecular packin
9、g is described as a columnar organization, the shortest Au Au distance being 4.639(1) between consecutive trimers.1. Introduction. Exobidentate N,N?-coordination of pyrazolato ligands has been extensively used on coordination oligomers and polymers 15. Typical pyrazolato- silver or-gold(I) derivativ
10、es have commonly been found as dimers or trimers 126 8, the latter being proposed to have a cyclic structure 12918 compatible with the sp2-hybridized N-atoms of the pyrazolato ring, the usual sp-hybridization of the metal center, and the requirements of a nine-membered planar ring. Other values of o
11、ligomerization have also been established for related complexes. Thus, a cyclic hexanuclear structure has been described for Au6(?-pzPh2)6 (pzPh2?3,5-diphenylpyr- azolato) 919, while bulky ligands such as 3,5-di(t-butyl)pyrazolato or the asymmetric 3-ethyl-4,5-dimethyl-pyrazolato have given rise to
12、cyclic tetramers 10. The latter structure has also been found for Ag4(?-pz4-i-C3F7)4 (pz4-i-C3F7?4-(hepta- fluoroisopropyl)pyrazolato) 3.? ? ? Vol. 87 (2004)250Despite the fact that some of these pyrazolato complexes were synthesized a long time ago, little structural characterization is available.
13、To the best of our knowledge, the X-ray structures of only some pyrazolato-gold trimers 91114, one pyrazolato- silver trimer 9 and one pyrazolato-gold hexamer 919 have been reported. From these results, we observed that the nine-membered metallocyclic core of the trimetallic species was planar or sl
14、ightly deviating from planarity depending on the substituents on the pyrazolato ligand. Besides, it was also interesting to note that the trimeric gold and silver derivatives containing 3,5-diphenylpyrazolato exhibited very different structures, i.e., while the former was highly symmetric, the silve
15、r analogue presented a strong deviation from idealized geometry 9. Recently it has been established that trigonal planar molecules with D3hsymmetry are specially prone to develop non-centrosymmetric packings, and they can be used as octupolar molecules with nonlinear optical (NLO) properties 2022. T
16、herefore, the study of new trinuclear pyrazolato-metal complexes opens new vistas for designing the required trigonal molecules. In addition, some trimetallic pyrazolato-gold(I) complexes of the type Au3(?-pz)3 have been shown to have liquid-crystal (LC) properties exhibiting columnar mesophases 121323. Most of them carry from 12 to 18 side chains in the molecular periphery (4 to 6 for eac
