Structural and spectroscopic correlations in cadmium(II) halide complexes of 2,2-dimetylpropane-1,3-diamine

Compounds of formula Cd(dmpd)2X2 (dmpd = 2,2-dimethylpropane-1,3-diamine; X = Cl, Br, I) were prepared and investigated by means of structural and spectroscopic (IR and Raman) measurements. The Cd(dmpd)2I2compound crystallizes in the monoclinic P2,/c space group, with two formula units in a cell of dimensions a = 6.235 (5) k,b = 18.462 (9) Å, c = 8.294 (5) Å, and β = 93.37 (6)°, with R = 0.039 and Rw = 0.044. The structure consists of discrete [Cd(dmpd)2I2] monomeric units, where the Cd atom is surrounded by four nitrogen atoms of two in-plane chelating dmpd molecules and by two iodine atoms asymmetrically coordinated in axial positions. The Cd(dmpd)2Br2 compound crystallizes in the triclinic Pi space group, with Z = 3 and a cell of dimensions a = 12.713 (2) Å, b = 16.592 (2) Å, c = 6.281 (3) Å, α = 91.22 (2)°, β = 96.67 (2)°, and γ = 78.72 (3)°, with R = 0.031 and Rw = 0.036. The structure consists of 1:1 molecular packing of Cd(dmpd)2Br2 monomeric and [Cd(dmpd)2Br2]2 dimeric units. In the monomer the Cd atom is octahedrally coordinated by four in-plane nitrogen atoms of two chelating dmpd molecules and by two bromine atoms in axial positions. The dimer consists of a pair of octahedrally coordinated Cd atoms, related by an inversion center, connected in a 12-membered metallacycle by two ambidentate dmpd molecules. The octahedral arrangement of each Cd atom in the dimer is completed by an in-plane chelating dmpd and by two bromine atoms, axially coordinated. The Cd(dmpd)2Cl2 compound is isomorphous with the bromine derivative, with unit cell dimensions a = 12.714 (3) Å, b = 16.228 (3) Å, c = 6.087 (5) Å, α = 91.61 (3)°, β = 96.02 (3)°, and γ = 77.76 (4)°. The CdN stretching vibrations are discussed and assigned in the light of the known structures.