The Synthesis and Dynamic Structures of Multinuclear Complexes of Large Porphyrinoids Expanded by Phenylene and Thienylene Spacers

1,3‐Bis(2‐pyrryl)benzene was used to prepare dibenziamethyrin, in which two pyrrole units of [24]amethyrin(1.0.0.1.0.0) are replaced by benzene. 1,4‐Bis(2‐pyrryl)benzene, 2,5‐bis(2‐pyrryl)thiophene, and 4,4′‐bis(2‐pyrryl)biphenyl were also used in place of 2,2′‐bipyrrole to give expanded analogues of [24]rosarin(1.0.1.0.1.0) and [32]octaphyrin(1.0.1.0.1.0.1.0). These large porphyrinoids can incorporate multiple metal units of Rh(CO) 2 and Pd(π‐allyl) with considerable deviation of the metal atoms from the dipyrrin planes, evidenced by X‐ray crystallography. The coordinated Rh(CO) 2 group shuttled between both sides of the macrocycle; the rate was dependent on the spacer, ring size, and number of metal atoms. Variable temperature 1 H NMR spectroscopy showed that the tris‐rhodium complexes of the expanded rosarins with 1,4‐phenylene or 2,5‐thienylene spacers adopt a C 3 v ‐symmetric form and a C s ‐symmetric form as a result of the Rh(CO) 2 groups hopping through the macrocycle cavity. The C 3 v ‐symmetric form has a greater dipole moment and, therefore, is favored in solvents of greater polarity. The Rh(CO) 2 groups in the tris‐rhodium complex of the expanded rosarin with 4,4′‐biphenylene spacers hop so fast that an averaged spectral pattern ( D 3 h ) was seen in the 1 H NMR spectrum, even at −60 °C. Expanded octaphyrins with 1,4‐phenylene and 2,5‐thienylene spacers bind four Rh(CO) 2 groups outside the macrocycle cavity to form a D 2 d ‐symmetric saddle‐shaped structure that did not show any dynamic behavior on the NMR timescale, even at 80 °C. This tetranuclear complex is one of the largest porphyrinoid metal complexes characterized by X‐ray crystallography to date.