Reduction of
4,4,12,12-tetramethyl-5,8,11-triazapentadecane-2,14-dione diperchlorate by
sodium borohydride yields as the major product one
isomer of 4,4-dimethyl-7-(5,5,7-trimethyl-1,2-diazepam 1-yl)-5-azaheptan-2-ol, pyaz. The coordination compounds [M(pyaz)]
(ClO4), and [Ni(pyaz)(NCS)] CNS (M = NiII,
CuII) were prepared, the latter being assigned five-coordinate
structures. The structure of singlet ground state [Ni(pyaz)]
(ClO4)2 was determined by X-ray diffraction [space group
P212121, Z 4, a 1450.8(2), b 1522.2(1),
c 1048.5(1) pm, R 0.0675, Rw 0.0768 for 2461 reflections]. The compound
has a square-planar coordination arrangement, with the three nitrogen and the
oxygen donor atoms of the pyaz ligand approximately
coplanar [Ni-O 190.0(6) pm; Ni-N 192.8(6), 189.2(6), 189.2(6) pm in sequence
N(5) of chain, N(l), N(4) of diazepane]. The diazepane ring adopts a boat conformation. One side of the
nickel(II) coordination plane is sterically crowded
by the presence of two axial methyl substituents. The ligand has two
non-equivalent chiral centres (C(14) of the diazepane ring and C(2) of the amine alcohol chain), both
present in the R configuration in the crystal studied. The three nitrogen
atoms, which became chiral centres upon coordination,
are present in the S configuration for two diazepane
nitrogen atoms and in the R configuration for the 5-aza chain nitrogen.
The Solvent Effect on Composition and Dimensionality of Mercury(II) Complexes with Picolinic Acid
