Trigonal-Bipyramidal Copper(II) Complexes with Symmetric and Unsymmetric Tripodal Tetramine Ligands

The syntheses of the aliphatic tripodal tetramine ligands N(CH 2 CH 2 CH 2 NH 2 ) 3 ( 1 ), N[(CH 2 CH 2 CH 2 NH 2 ) 2 (CH 2 CH 2 NH 2 )] ( 2 ), and N[(CH 2 CH 2 CH 2 NH 2 )(CH 2 CH 2 NH 2 ) 2 ] ( 3 ) are reported. The tripodal N 4 -ligands 1 − 3 react with Cu(OH) 2 in water to give blue copper(II) complexes. Addition of NH 4 PF 6 to such solutions yields complexes of the type [Cu(N 4 )(NH 3 ](PF 6 ) 2 [ 4; N 4 = 1, 4a; N 4 = 2, 4b; N 4 = 3, 4c ]. The molecular structures of complexes 4a − c have been determined by X-ray diffraction. All three complexes can be crystallized from water. Selected crystallographic details are as follows 4a [ 4b ] { 4c }: formula C 9 H 27 CuF 12 N 5 P 2 [C 8 H 25 CuF 12 N 5 P 2 ] {C 7 H 23 CuF 12 N 5 P 2 }, M = 558.82 [544.79] {530.76} amu, monoclinic [monoclinic] {orthorhombic}, P 2 1 / c [ C 2/ c ] { P 2 1 2 1 2}, a = 8.9519(14) [30.181(6)] {15.075(5)} Å, b = 16.803(3) [8.914(3)] {12.2939(14)} Å, c = 13.834(2) [14.253(4)] {10.064(2)} Å, α = 90.0 [90.0] {90.0}°, β = 94.183(12) [93.76(2)] {90.0}°, γ = 90.0 [90.0] {90.0}°, V = 2075.3(10) [3826(3)] {1865.2(12)} Å 3, Z = 4 [8] {4}, R = 5.10 [3.42] {4.32}%, R w = 6.67 [5.12] {5.23}% for 2480 [2137] {1533} absorption corrected structure factors F o 2 ≥ 3σ(F o 2 ) and 262 [255] {245} refined parameters. The complex dications in 4a − c exhibit a trigonal-bipyramidal geometry with the tertiary nitrogen of the tripodal ligand and the ammonia nitrogen in the axial positions. Complexes with the unsymmetric ligands 2 and 3 possess both five and six membered chelate rings. Depending on the ligand, the size of the cavity for the ammonia ligand increases from 4a to 4c . This leads to a shortening of the Cu−NH 3 bond length with the shortest bond of this type observed for 4c .