Preparation, and complexes with nickel(II) and copper(II), of a diazepane amine alcohol. The structure of [4,4-dimethyl-7-(5,5,7-trimethyl-1,4-diazepan-1-yl)-5-azaheptan-2-ol]nickel(II) perchlorate

Abstract

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 = Ni^II, Cu^II) 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, R_w 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.