Configurational preferences of two 1,2-diamine adducts of bis(1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)cobalt(II)
作者:Leandros C. Tzavellas、Chris Tsiamis、Constantin A. Kavounis、Christine J. Cardin
DOI:10.1016/s0020-1693(97)05503-5
日期:1997.9
The preparation, the IR and ligand field spectra and the structures of the mixed-ligand addition compounds [(N,N-dimethyl-1,2-diamino-ethane)bis( 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)cobalt], [Co(thtf)(2)me(2)en], and [(N,N,N',N'-tetramethyl-1,2-diamino-ethane)bis( 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)colbalt(II)], [Co(thtf)(2)me(4)en], are reported. The structures were determined by single crystal X-ray diffraction analysis (monoclinic, space group P2(1)/c, Z=4 with a=10.708(6), b=19.531(6), c=13.352(6) Angstrom, beta = 111.64(10)degrees, R-1 = 0.0642 and R-w(2) = 0.1719 for [Co(thtf)(2)(me(2)en)] and a = 12.033(6), b = 15.565(6), c = 15.339(6) Angstrom, beta = 92.57(6)degrees, R-1 = 0.0612 and R-w(2)=0.1504 for [Co(thtf)(2)me(4)en]). The structures are distorted octahedral and the shortest cobalt-cobalt separation distances are 5.388(2) Angstrom in [Co(thtf)(2)me(2)en] and 8.675(3) Angstrom in [Co(thtf)(2)me(4)en]. In both compounds the diamine molecules attain the gauche conformation. The U(Z,Z) conformation of the beta-dione leads to a semi-chair conformation of the beta-dionato chelate rings. The relative orientation of the groups attached to the beta-dionato moiety depends on the extent of stereoelectronic effects the N-substitution of the diamine entails. In [Co(thtf)(2)me(2)en] the intraligand distance separating the trifluoromethyl carbon atoms is 5.281(18) Angstrom while in [Co(thtf)(2)me(2)en] it increases to 8.338(9) Angstrom. The cobalt-cobalt separation distance, the orientation of the chelate rings and the extent of N-substitution seem to affect hydrogen bonding. While in [Co(thtf)(2)me(2)en] inter- and intraligand hydrogen bonding is implicated, it is totally absent in [Co(thtf)(2)me(4)en].