The compounds trans-[Ni(333-tet)(mu-N3)]n(ClO4)n (1) and cis-[Ni(333-tet)(mu-N3)]n(PF6)n(2) in which 333-tet is the tetraamine N,N’-bis(3-aminopropyl)-1,3-propanediamine have been synthesized and characterized. 1 crystallizes in the triclinic system, space group P1BAR, with fw = 388.50, a = 8.765(1) angstrom, b = 8.976(1) angstrom, c = 11.995(2) angstrom, alpha = 106.65(1)degrees, beta = 110.06(1)degrees, gamma = 91.11(1)degrees, V = 842.0(2) angstrom3, Z = 2, R = 0.047, and R(w) = 0.130. The nickel atom is placed in an octahedral environment with the bridging azido groups in a trans arrangement. Two kinds of alternating centrosymmetric azido bridges, both coordinated in end-to-end fashion, are present in the chain, for which the Ni-N bond distance and Ni-N-N bond angle are 2.077(3) angstrom, 142.4(3)degrees and 2.204(3) angstrom, 123.6(2)degrees, respectively, giving an unusual alternating system. 2 crystallizes in the orthorhombic system, space group P2(1)2(1)2(1), with fw = 434.03, a = 15.7 36(3) angstrom, b = 13.607(3) angstrom, c = 8.182(2) A, v = 1751.9(7) angstrom3, Z = 4, R = 0.062, and R(w) = 0.154. The nickel atom is placed in an octahedral environment with the end-to-end azido bridges in an unprecedented cis arrangement. Magnetic measurements show a strong antiferromagnetic coupling for 1, where J = -80.7 cm-1, alpha = 0.46, and g = 2.40, and lower coupling for 2, where J = -18.5 cm-1 and g = 2.29. The magnetic behavior of both compounds has been correlated with the bond parameters.