The copper(I) and copper(II) complexes with the nitrogen donor ligands bis[(1-methylbenzimidazol-2-yl)methyl]amine (1-BB), bis[2-(1-methylbenzimidazol-2-yl)ethyl]amine0 (2-BB), N-acetyl-2-BB (AcBB), and tris[2-(1-methylbenzimidazol-2-yl)ethyl]nitromethane (TB) have been studied as models for copper nitrite reductase. The copper(II) complexes form adducts with nitrite and azide that have been isolated and characterized. The Cu(II)(1-BB) and Cu(Il)-AcBB complexes are basically four-coordinated with weak axial interaction by solvent or counterion molecules, whereas the Cu(II)-(2-BB) and Cu(II)-TB complexes prefer to assume five-coordinate structures. A series of solid state structures of Cu(LI)-(1-BB) and -(2-BB) complexes have been determined. [Cu(1-BB)(DMSO-O)(2)](ClO4)(2) : triclinic, P (1) over bar (No. 2), a = 9.400(1) Angstrom, b = 10.494(2) Angstrom, c = 16.760(2) Angstrom, alpha = 96.67(1)degrees, beta = 97.10(1)degrees, gamma = 108.45(1)degrees, V = 1534.8(5) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 3 sigma(I)] = 4438, number of refined parameters = 388, R = 0.058. [Cu(1-BB)(DMSO-O)(2)](BF4)(2) : triclinic, P (1) over bar (No. 2), a = 9.304(5) Angstrom, b = 10.428(4) Angstrom, c = 16.834(8) Angstrom, alpha = 96.85(3)degrees, beta = 97.25(3)degrees, gamma = 108.21(2)degrees, V = 1517(1) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 3388, number of refined parameters = 397, R = 0.075. [Cu(1-BB)(DMSO-O>(NO2)](ClO4) : triclinic, P (1) over bar (No. 2), a = 7.533(2) Angstrom, b = 8.936(1) Angstrom, c = 19.168(2) Angstrom, alpha = 97.66(1)degrees, beta = 98.62(1)degrees, gamma = 101.06(1)degrees, V = 1234.4(7) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 3426, number of refined parameters = 325, R = 0.081. [Cu(2-BB)(MeOH)(ClO4)](ClO4) : triclinic, P (1) over bar (No. 2), a = 8.493(3) Angstrom, b = 10.846(7) Angstrom, c = 14.484(5) Angstrom, alpha = 93.71(4)degrees, beta = 103.13(3)degrees, gamma = 100.61(4)degrees, V = 1270(1) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 2612, number of refined parameters = 352, R = 0.073. [Cu(2-BB)(N-3)](ClO4> : monoclinic, P2(1)/n (No. 14), a = 12.024(3) Angstrom, b = 12.588(5) Angstrom, c = 15.408(2) Angstrom, beta = 101,90(2)degrees, V = 2282(1) Angstrom(3), Z = 4, number of unique data [I greater than or equal to 2 sigma(I)] 2620, number of refined parameters = 311, R = 0.075. [Cu(2-BB)(NO2)](ClO4)(MeCN) : triclinic, P (1) over bar (No. 2), a = 7.402(2) Angstrom, b = 12.500(1) Angstrom, c = 14.660(2) Angstrom, alpha = 68.14(1)degrees, beta = 88.02(2)degrees, gamma = 78.61(1)degrees, V = 1233.0(4) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 2088, number of refined parameters = 319, R = 0.070. In all the complexes the 1-BB or 2-BB ligands coordinate the Cu(II) cations through their three donor atoms. : triclinic, P (1) over bar (No. 2), a = 9.400(1) Angstrom, b = 10.494(2) Angstrom, c = 16.760(2) Angstrom, alpha = 96.67(1)degrees, beta = 97.10(1)degrees, gamma = 108.45(1)degrees, V = 1534.8(5) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 3 sigma(I)] = 4438, number of refined parameters = 388, R = 0.058. [Cu(1-BB)(DMSO-O)(2)](BF4)(2) : triclinic, P (1) over bar (No. 2), a = 9.304(5) Angstrom, b = 10.428(4) Angstrom, c = 16.834(8) Angstrom, alpha = 96.85(3)degrees, beta = 97.25(3)degrees, gamma = 108.21(2)degrees, V = 1517(1) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 3388, number of refined parameters = 397, R = 0.075. [Cu(1-BB)(DMSO-O>(NO2)](ClO4) : triclinic, P (1) over bar (No. 2), a = 7.533(2) Angstrom, b = 8.936(1) Angstrom, c = 19.168(2) Angstrom, alpha = 97.66(1)degrees, beta = 98.62(1)degrees, gamma = 101.06(1)degrees, V = 1234.4(7) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 3426, number of refined parameters = 325, R = 0.081. [Cu(2-BB)(MeOH)(ClO4)](ClO4) : triclinic, P (1) over bar (No. 2), a = 8.493(3) Angstrom, b = 10.846(7) Angstrom, c = 14.484(5) Angstrom, alpha = 93.71(4)degrees, beta = 103.13(3)degrees, gamma = 100.61(4)degrees, V = 1270(1) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 2612, number of refined parameters = 352, R = 0.073. [Cu(2-BB)(N-3)](ClO4> : monoclinic, P2(1)/n (No. 14), a = 12.024(3) Angstrom, b = 12.588(5) Angstrom, c = 15.408(2) Angstrom, beta = 101,90(2)degrees, V = 2282(1) Angstrom(3), Z = 4, number of unique data [I greater than or equal to 2 sigma(I)] 2620, number of refined parameters = 311, R = 0.075. [Cu(2-BB)(NO2)](ClO4)(MeCN) : triclinic, P (1) over bar (No. 2), a = 7.402(2) Angstrom, b = 12.500(1) Angstrom, c = 14.660(2) Angstrom, alpha = 68.14(1)degrees, beta = 88.02(2)degrees, gamma = 78.61(1)degrees, V = 1233.0(4) Angstrom(3), Z = 2, number of unique data [I greater than or equal to 2 sigma(I)] = 2088, number of refined parameters = 319, R = 0.070. In all the complexes the 1-BB or 2-BB ligands coordinate the Cu(II) cations through their three donor atoms.