Stereochemistry of racemic hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-dienenickel(II) thiocyanate,C16H32N4Ni(SCN)2 · H2O |
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Authors: | F. Hanic D. Mikloš |
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Affiliation: | (1) Institute of Inorganic Chemistry of the Slovak Academy of Sciences, Dúbravská cesta, Bratislava, Czechoslovakia |
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Abstract: | The diamagnetictrans-diene thiocyanate salt of the macrocyclic hexamethyl-1,4,8,11-tetraazacyclotetradecadienenickel(II) complex crystallizes in the triclinic system with unit cell dimensions:a = 7·334(4),b = 8·808(6),c = 21·04(2) Å; = 63·7(0·9), = 103·8(1·4), = 110·2(1·3) °; space groupP¯1;Z = 2. The positions of all 62 atoms of the formula unit C16H32N4Ni(SCN)2.H2O have been determined and refined by least-squares methods toR= 0·071 for 3536 X-ray diffractometric reflections. The optical activity of the two amine groups yields a racemic isomer. The only local symmetry element of the macrocyclic complex is the twofold rotation axis with the N-H bonds oriented on the same side of the approximate ligand plane. Both the C(CH3)2 and the imine groups are in atrans-configuration in the ring. The space group ensures that the crystal is a racemate, containing equal numbers of both enantiomers. One of the (SCN)– groups is at a distance Ni-S 3·28 Å, the other one is 4·65 Å. No rotational disorder of the CH3 groups has been observed. The three C-H bonds of the CH3 groups are in approximately antiprismatic orientations with respect to the three -bonds in the case of bonding to a C(sp3) atom. The average of the C(sp3)-C(sp2) bond lengths is 1·53 Å, and the mean value for the C(sp3)-C(sp2) bonds is 1·50 Å, with 3 = 0·03 to 0·04 Å. The distances N(sp2)-C(sp3) 1·47 Å and 1·48 Å are significantly longer than the bond lengths N(sp2)=C(sp2) of 1·28 and 1·30 Å. |
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