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Dinuclear rhodium(I) complexes, [Rh(4-Me-pf) (cod)]2 (1), [Rh(3,5-Me2-pf) (cod)]2 (2), [Rh(4-Me-pf) (nbd)]2 (3), [Rh(3,5-Me2-pf) (nbd)]2 (4), and [Rh(2,6-F2-pf) (nbd)]2 (5), have been synthesized and characterized by X-ray structure analysis, 1H, 13C, and 19F NMR, UV–vis, ESI-TOF-MS, and elemental analysis. In these complexes, two rhodium atoms are bridged by two formamidinato ligands and each rhodium atom is coordinated by one chelating cod or nbd ligand to form an approximately square planar coordination structure with two nitrogen atoms and two double bonds. The Rh··Rh distances are in the range of 3.2668 to 2.9726 A, suggesting a direct bonding interaction between two rhodium atoms. Variable temperature NMR studies in CD2Cl2 solution have revealed that 1–5 exhibit a novel dynamic behavior, that is, an interconversion between two enantiomers. The activation parameters for racemization have been determined by the line shape analyses of the 1H and 19F NMR spectra taken at various temperatures. Variable temperature NMR studies have also revealed that the rotation rates of the four aryl groups around N–C(aryl) bonds are extremely different in each complex. The cyclic voltammetry study has shown that the oxidation potentials corresponding to Rh23+/Rh2+ are 0.41 V in the cod complexes (1 and 2) while those in the nbd complexes (3–5) have shown negative shift by ca. 0.2 V. The reasons for the difference in dynamic behaviors and redox properties among these complexes have been discussed.

Lantern-type dinuclear complexes, cis-[Ru2{3,5-(CF3)2-pf}2(O2CMe)2Cl] and [Ru2{3,5-(CF3)2-pf}3(O2CMe)Cl] (3,5-(CF3)2-pf− = N,N′-bis[3,5-bis(trifluoromethyl)phenyl]formamidinate anion), were prepared and characterized. The cis-(2:2) and (3:1) arrangements of the formamidinate and acetate bridging ligands around the Ru25+ core were confirmed by the X-ray crystal analysis as well as 1H and 19F NMR spectra (measured at 25 °C in CD2Cl2), where paramagnetic shifts were observed for the signals due to the unpaired electrons in the dinuclear core. Variable-temperature magnetic moments (2–300 K) showed the existence of three unpaired electrons in the dinuclear units with the large D values (60 cm−1 for the cis-(2:2) Ru25+ complex and 50 cm−1 for the (3:1) Ru25+ complex). The electronic state with S = 3/2 was also ascertained by the EPR spectra measured in solid at 4 K and in frozen toluene/dichloromethane solution at 15 K, absorption spectra in dichloromethane and cyclic voltammograms (CVs) in THF using tetra-n-butyl ammonium perchlorate (TBAP) as electrolyte.

Homo- and hetero-dinuclear nickel(II), copper(II), and oxidovanadium(IV) complexes of a Schiff-base-fused phthalocyanine (pc) with bulky substituents, 2,6-dimethylphenoxy and t -butyl groups, were prepared and characterized. The introduced salen-like Schiff-base unit was shown to affect the spectral feature based on the pc unit in the near infrared region, the Q band being widely split over 600–800 nm. A fairly large ferromagnetic interaction ( J = 6.0 cm −1 ) was observed for the Cu II (pc)–Cu II (salen) homo-dinuclear complex, while an antiferromagnetic interaction ( J = −3.2 cm −1 ) was observed for the Cu II (pc)–V IV O(salen) hetero-dinuclear complex.

Lantern-type dinuclear complexes, cis-[Ru2(4-Me-pf)2(O2CMe)2Cl] and trans-[Ru2(2,6-Et2-pf)2(O2CMe)2Cl] (4-Me-pf− = N,N′-bis(4-methylphenyl)formamidinate ion and 2,6-Et2-pf− = N,N′-bis(2,6-diethylphenyl)formamidinate ion), were prepared and characterized. The dinuclear structures with cis- and trans-arrangements of the bridging ligands were confirmed by the X-ray crystal structures as well as 1H NMR spectra (298 K) in CD2Cl2, where the proton signals were observed at widely spread positions δ = − 80 to 25 ppm. Variable-temperature magnetic moments (2–300 K) showed the existence of three unpaired electrons in dinuclear units with large D values (65 cm− 1 for cis-Ru2II,III and 90 cm− 1 for trans-Ru2II,III).

There are two types of electron configuration, (dxy)2(dxz, dyz)3 and (dxz, dyz)4(dxy)1, in low spin iron(III) porphyrin complexes. In order to reveal how the electronic effect of substituents affects the electron configuration of low spin iron(III) porphyrin complexes, we have examined the 13C NMR, 1H NMR, and EPR spectra of a series of tetrabutylammonium (dicyano)[meso-tetrakis(p-substituted phenyl)porphyrinato]ferrate(III), [Fe(p-X–TPP)(CN)2]−Bu4N+, in both CD2Cl2 and CD3OD solutions. The chemical shifts of the meso carbon signals, which sharply reflect the electron configuration of low spin iron(III), have changed to a great extent depending on the electron-donating or electron-withdrawing ability of the para-substituent. The isotropic shifts of the meso-carbon signals of [Fe(p-X–TPP)(CN)2]−Bu4N+ are determined on the basis of the meso-carbon chemical shifts of the corresponding diamagnetic cobalt(III) complexes, [Co(p-X–TPP)(CN)2]−Bu4N+. The plots of the isotropic shifts against Hammett σp values have yielded good linear lines with the slopes, −22 and −69 ppm, in CD2Cl2 and CD3OD, respectively. On the basis of these results, we have concluded that the electron-withdrawing groups at the phenyl para-positions stabilize the (dxy)2(dxz, dyz)3 state while the electron-donating groups at the same positions stabilize the (dxz, dyz)4(dxy)1 state. The conclusion is further supported by the 1H NMR and EPR results.

An annulated dinuclear palladium(II) phthalocyanine complex ( 1 ) was synthesized and characterized. It was found that 1 worked as a photo-catalyst for the decomposition of 1,3-diphenylisobenzofuran (DPBF) in aerated toluene under the irradiation of the light in the near-infrared (NIR) region (λ > 780 nm).

There has been much interest directed to lantern-type diuclear metal complexes with direct metal–metal bonds due to their unique properties based on their metal–metal bonds.1,2 Formamidinate ions as well as carboxylate ions are known to work as a dinuclearting ligand to give a lantern-type dinuclear structure.1,2 Dinuclear complexes with the mixing of carboxylato and formamidinato bridges are intriguing, because the chemistry would be newly developed based on the different bridging groups within the dinuclear core. We have reported on the crystal structure rhodium(II) dinuclear complexes with two formamidinatao and two carboxylato bridging ligands in a cis(2:2) arrangement around the dinuclear core, cis-[Rh2(4-Etpf)2(O2CCF3)2(H2O)(MeOH)] (1) and cis-[Rh2(4-Etpf)2(O2CCF3)2(MeOH)2] (2), where 4-Et-pf= N,N¢-bis(4ethylphenyl)formamidinate anion.3,4 They have the same dinuclear structure with similar dimensions other than the difference in the axial ligand between H2O and MeOH (Rh–Rh = 2.4487(7)A, Rh–N(4-Et-pf) = 2.008(4) – 2.012(3)A, Rh–O(O2CCF3) = 2.078(3) – 2.100(3)A, Rh–O(H2O) = 2.453(5) A, and Rh–O(MeOH) = 2.321(3)A for 1; Rh–Rh = 2.4484(6)A, Rh–N(4Et-pf) = 2.005(3) – 2.016(3)A, Rh–O(O2CCF3) = 2.079(2) – 2.115(2)A, and Rh–O(MeOH) = 2.314(2) and Crystal Structure of a Lantern-Type Dirhodium(II) Complex with a cis-(2:2) Arrangement of Two Formamidinato and Two Trifluoroacetato Bridges

Deuterated dinuclear ruthenium(II,III) 3,4,5-tri(ethoxy-d 5)benzoate, [Ru2{3,4,5-(C2D5O)3C6H2-COO}4Cl]n, was synthesized by a reaction of [Ru2(C2H5COO)4Cl]n and 3,4,5-tri(ethoxy-d 5)benzoic acid and characterized by single-crystal X-ray analysis as well as IR, UV-VIS, and 1H NMR spectra, and compared with those of the undeuterated complex [Ru2{3,4,5-(C2H5O)3C6H2COO}4Cl]n. Single-crystal X-ray analysis showed that chloride ligands bridge the dinuclear ruthenium(II,III) units at the axial positions to form a zigzag chain molecule with the Ru1-Cl-Ru2 angle of 123.82(4)°. 1H NMR spectra in CD2Cl2 displayed a broad signal attributable to o-H atoms on the phenyl rings of the benzoate ligands from approximately δ = 23 to δ = 32 at 25°C and several signals from approximately δ = −50 to δ = 50 at −80°C. These spectra show the preservation of the polymeric or oligomeric chain structure in dichloromethane, which is supported by the solution behavior confirmed by the UV-VIS spectra and electronic conductance.

Polymeric complexes of ruthenium(II)-ruthenium(III) tetracarboxylato units linked by cyanato, thiocyanato, and selenocyanato ligands [Ru2{O2C(CH2)mCH3}4(L)]n (m = 0, 4–7; L = OCN−, SCN−, and SeCN−) were prepared and characterized based on the elemental analyses, IR, and diffuse reflectance spectra. Magnetic susceptibilities were measured at the temperature range of 4.5 K to 300 K, where the interdimer antiferromagnetic interactions were revealed. The strongest interaction was exhibited in case of m = 7 and L = OCN−. 1H-NMR spectra of [Ru{O2C(CH2)7CH3}4(SCN)]n in CD2Cl2 showed broad signals which can be ascribed to polymeric species, as the addition of tetrabutylammonium thiocyanate caused sharper signals due to the formation of [Ru2{O2C(CH2)7CH3}4(SCN)2]− adduct as the main species in the solution.

The title compound of a lantern-type rhodium(II) dimer, [Rh2(4-Et-pf)2(O2CCF3)2(H2O)(MeOH)] (4-Et-pf – = N,N¢-bis(4ethylphenyl)formamidinate anion), was isolated and the crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. It crystallizes in the triclinic space group P1 with a = 10.866(2)A, b = 13.435(3)A, c = 14.834(4)A, a = 85.764(3)˚, b = 75.546(3)˚, g = 83.729(3)˚, V = 2082.0(7)A 3 , Dx = 1.571 g/cm 3 , and Z = 2. The R1 [I > 2s(I)] and wR2 (all data) values are 0.0449 and 0.1222, respectively, for all 12360 independent reflections. The cis-(2:2) arrangement of the 4-Et-pf and trifluoroacetato ligands within the dimer was confirmed, the methanol and water molecules coordinating to each axial site of the dimer, respectively. The Rh–Rh distance is 2.4487(7)A and the axial Rh–O distances are 2.321(3) (for Rh–O (MeOH)) and 2.454(5)A (for Rh–O (H2O)), respectively.

The title compound, dinuclear rhodium(II) complex with di-N,N′-p-tolylformamidinate ion (form-) and acetonitrile [Rh2(form)4(CH3CN)]·2H2O, was isolated from the CH2Cl2-CH3CN solution containing equimolar amounts of [Rh2(form)4] and 1,4-dicyanobenzene (1,4-dcb), and the crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. It crystallizes in the tetragonal space group P4/ncc with a = 16.275(3)A, c = 23.955(6)A, V = 6345(2)A3, Dx = 1.231 g/cm3, and Z = 4. The R1 and wR2 values are 0.0437 and 0.1402, respectively, for 3250 reflections. The crystal consists of tetrakisformamidinato-bridged rhodium(II) dimers with a Rh-Rh distance of 2.4750(10)A, CH3CN molecules axially coordinating to the rhodim(II) dimer with a Rh-N distance of 2.119(7)A, and crystal waters. The crystal does not include 1,4-dcb, showing that 1,4-dcb did not work to link the rhodium(II) dimer.

The title polymer compound of rhodium(II) formamidinate with toluene as crystal solvents [Rh2(form)4(1,4-dib)]n·2n(toluene) (form- = N,N′-di-p-tolylformamidinate anion; 1,4-dib = 1,4-diisocyanobenzne) was isolated, and the crystal structure was determined by the single-crystal X-ray diffraction method at 123 K. It crystallizes in the orthorhombic space group P212121 with a = 11.5161(16)A, b = 20.946(4)A, c = 28.944(4)A, V = 6981.7(16)A3, Dx = 1.343 g/cm3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0441 and 0.0744, respectively, for all 16061 independent reflections. The Rh-Rh distance is 2.5702(5)A and the axial Rh-C (dib) distances are 2.041(3) and 2.050(3)A. The polymer chain with the alternated arrangement of rhodium(II) dimer and 1,4-dib extends along the c axis in the crystal, slightly tilting with respect to the axis.

The title compound, dinuclear rhodium(II) pentafluorobenzoate with methanol [Rh2(O2CC6F5)4(CH3OH)2], was isolated and the crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. It crystallizes in the monoclinic space group P21/c with a = 7.889(3)A, b = 34.808(14)A, c = 12.983(5)A, β = 103.930(7)°, V = 3460(2)A3, Dx = 2.139 g/cm3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0319 and 0.0747, respectively, for all 8031 independent reflections. The Rh-Rh distance is 2.3829(9)A and the axial Rh-O (methanol) distances are 2.2689(19) and 2.254(2)A. The 13C and 19F NMR spectra showed that the dimer structure is preserved in THF.

Low-spin ferric porphyrin radical cations formed by the oxidation of chloro(meso-tetraalkylporphyrinato)iron(III) followed by the addition of bulky 2-methylimidazole show antiferromagnetic coupling, which is interpreted in terms of the interaction between porphyrin a2u and iron dxy orbitals caused by the S4 ruffling of the porphyrin core.

Combined analyses using NMR, EPR and Mössbauer spectroscopy as well as SQUID magnetometry have revealed that highly saddle shaped Fe(OETPP)I adopts an essentially pure intermediate spin state in spite of the coordination of an iodide ligand.

Bis(thf)(porphyrinato)iron(III) complexes with highly S4-ruffled and S4-saddled porphyrin cores are determined to be very pure intermediate spin complexes on the basis of NMR, EPR, Mossbauer, and magnetic data.

The meso-13C chemical shifts have been revealed to serve a powerful probe to determine the coordination structure and electron configuration of ferric porphyrin complexes.