The syntheses and first crystal structures of molecular examples of the Fe-III-CN-Cu-II bridge and their heme and Cu(II) precursors and related Cu(II) complexes are reported. The bridged species were sought as analogues to the binuclear site of cyanide-inactivated cytochrome c oxidase. Reaction of Cu(II) triflate with tripodal Me(6)tren in acetone gave [Cu(Me(6)tren)(OSO2CF3)](+) (1), which was readily converted to [Cu(Me(6)tren)(MeCN)](2+) (2). Compounds [1](CF3SO3)/[2](CF3SO3)(2) were found in monoclinic space group P2(1)/c with a = 11.214(4)/11.385-(7) Angstrom, b = 13.103(5)/17.069(9) Angstrom, c = 16.251(7)/13.988(6) Angstrom, beta = 94.16(3)(alpha)/90.56(4)degrees, and Z = 4/4. A similar reaction with tren in acetonitrile produced [Cu(tren)(MeCN)](2+). [Cu(Me(6)tren)(OH2)](2+) (4) with 1 equiv of KCN in methanol formed [Cu(Me(6)tren)(CN)](+) (6). Compounds [3](CF3SO3)2/[6](ClO4) crystallized in trigonal space group R3c with a = 8.038(1)/10.003(3) Angstrom, c = 55.31(2)/32.70(1) Angstrom, and Z = 6/6. Complexes 1-3 and 6 have trigonal bipyramidal (TBP) stereochemistry with unidentate ligands in axial positions. Reaction of 4 in acetonitrile with 1/2 equiv of KCN afforded binuclear [(Cu(Me(6)tren))(2)(CN)](3+) (5), which as [5](ClO4)(3).3MeNO(2) occurred in triclinic space group P (1) over bar with a = 9.562(2) Angstrom, b = 13.327(3) Angstrom, c = 20.775(6) Angstrom, alpha = 85.32(2)degrees, beta = 78.68(2)degrees, gamma = 70.86(2)degrees, and Z = 2. The complex contains two TBP halves connected by the disordered linear Cu-II-CN-Cu-II bridge in axial positions. Copper(lI) triflate with Me(5)dien in acetone afforded [Cu(Me(5)dien)(OSO2-CF3)(2)] (7) while reaction of [Cu(OH2)(6)](2+) With tridentate Me(5)dien in acetonitrile gave [Cu(Me(5)dien)(MeCN)(2)](2+) (8). The compounds 7/[8](BF4)(2) were found in monoclinic space groups Cc/(P2(1)/n) with a = 13.412(8)/8.568(6) Angstrom, b = 10.729(4)/14.800(7) Angstrom, c = 14.876(8)/17.42(1) Angstrom, beta = 109.11(4)/90.98(6)degrees, and Z = 4/4. These complexes exhibit distorted tetragonal planar (TP) structures. Complex 7 with 1 equiv of KCN in methanol/acetonitrile formed [Cu(Me(5)dien)(CN)](n+)(n) (9), which as [9](CF3SO3) crystallized in orthorhombic space group Pnma with a = 7.631(2) Angstrom, b = 10.991(2) Angstrom, c = 20.876(4) Angstrom, and Z = 4. TP 9 is polymerized through cyanide bridges in equatorial positions.[Fe(OEP)]O-2 was converted to [Fe(OEP)(CN)L] (L = py (10), 1-MeIm (11)) by treatment with Me(3)SiCN and L in dichloromethane. Compound 11 was found in P (1) over bar with a = 10.032(4) Angstrom, b = 13.306(5) Angstrom, c = 17.695(7) Angstrom, alpha = 75.97(3)degrees, beta = 86.64(3)degrees, gamma = 73.53(3)degrees, and Z = 2. Reaction of 10 or 11 with 4 in acetone afforded the bridged assemblies [L(OEP)Fe-CN-Cu(Me(6)tren)](2+) (L = py (13), 1-MeIm(14)), while a similar reaction of 10 and 7 yielded [(py)(OEP)Fe-CN-Cu(Me(5)dien)(OSO2CF3)](+) (15). The compounds [13]-(SbF6)(2). Me(2)CO/[15](CF3SO3) crystallize in P (1) over bar with a = 13.833(3)/11.941(2) Angstrom, b = 16.552(4)/13.576(3) Angstrom, c = 31.532(6)/19.280(5) Angstrom, alpha = 94.90(2)/84.08(2)degrees, beta = 94.66(2)/80.38(2)degrees, gamma = 112.52(2)/70.60(2)degrees, and Z = 4/2. Both 13 and 15 possess the desired, nearly linear Fe-III-CN-Cu-II bridge which links a heme to a Cu fragment; their stereochemistries are only slightly altered from those of the precursor complexes. The bridge occupies an axial position in 13 and an equatorial position in 15. The doubly bridged assembly {[Cu(Me(6)tren)]Fe-2(OEP)-(CN)(2)]}(3+) (16) was prepared by the reaction of [Fe(OEP)(OClO3)] with 2 equiv of 6 in acetone. The compound [16](SbF6)(3) occurred in orthorhombic space group Pbcn with a = 13.093(4) Angstrom, b = 28.964(8) Angstrom, c = 21.243(4) Angstrom, and Z = 4. The bridge unit Cu-II-NC-Fe-III-CN-Cu-II shows small departures from linearity. Metric data of precursor and related complexes are considered and compared with dimensions of bridge units in 13 and 15, and the structural systematics of the Fe-III-CN-Cu-II bridge unit are summarized. Cyanide stretching frequencies for terminal and bridged units are collected and compared. For assemblies containing the Fe-III-CN-Cu-II bridge in the solid and solution phases, nu(CN) = 2174-2183 cm(-1), whereas for the enzymes nu(CN) = 2146-2151 cm(-1). Possible reasons for the higher frequencies of the synthetic bridges are considered. Both the bridged assemblies and the binuclear center for the cyanide-inhibited enzymes are exchange-coupled to afford an integer spin state, leading to the conclusion that a bridge is formed in the enzymes but may differ in structure from that established in 13 and 15. (1-MeIm = 1-methylimidazole, Me(5)dien = 1,1,4,7,7-pentamethyldiethylenetriamine, Me(6)tren = 2,2’,2"-tris(dimethylaminoethyl)amine, OEP = octaethylporphyrinate(2-), py = pyridine, tren = tris(2-aminoethyl)amine).y?