The molecular structures of a homologous series of palladium(I1) porphyrin, chlorin, and isobacteriochlorin complexes were determined by X-ray diffraction. The porphyrin compound (2,3,7,8,12,13,17,18-octaethylpo hyrinato)palladium(II), Pd(OEP), crystallizes in the triclinic space group PT (2 = 1) with unit cell dimensions a = 7.809 (5)3, b = 9.934 (4) A, c = 10.429 (3) A, a = 91.05 (2)O, @ = 98.07 (4)O, y = 1 1 1.05 (4)O, and V = 745.4 (5) A3. The structure has been refined to R = 0.057 on F, on the basis of 3437 reflections with F,Z > 0. Pd(0EP) has a crystallographically imposed inversion center. The chlorin compound (truns-2,3-dihydr~2,3,7,8,12,13,17,18-octaethylporphyrinato)palladium(II), t-Pd(OEC), crystallizes in the orthorhombic s ace group Pnab (2 = 4) with unit cell dimensions u = 8.969 (3) A, b = 15.867 (5) A, c = 22.1 17 (7) A, and V = 3147.5 (3.0)13. The structure has been refined to R = 0.0358 on F, on the basis of 1671 reflections with I > 1.96a(I). Pd(0EC) has a crystallographically imposed 2-fold axis passing through the unique pyrroline nitrogen atom, the palladium atom, and the pyrrole nitrogen which is across the macrocycle from the pyrroline ring. The isobacteriochlorin compound (rct-2,3,7,8-tetrahydro-2,3,7,8,12,13,17,18-octaethylporphyrinato)palladium(II), trt-Pd(OEiBC), crystallizes in the monoclinic space group Ell n (2 = 4) with unit cell dimensions a = 12.540 (4) A, b = 12.745 (3) A, c = 20.557 (6) A, @ = 92.24 (2)O, and V = 3283 (1.5) k3. The structure has been refined to R = 0.056 on F, on the basis of 4005 reflections with F,2 > 347:). 1981, 20, 21 1. (b) Johansen, J. E.; Piermattie, V.; Angst, C.; Diener, E.; Kratky, C.; Eschenmoser, A. Angew. Chem., In?. Ed. Engl. 1981, 20, 261. (c) Kratky, C.; Waditschatka, R.; Angst, C.; Johansen, J. E.; Plaquevent, J. C.; Schreiber, J.; Eschenmoser, A. Helu. Chim. ACIQ 1985, 68, 1312. (d) Waditschatka, R.; Kratky, C.; Jaun, B.; Heinzer, J.; Eschenmoser, A.