Np(COT)* and PU(COT)~ (COT = C8Ha2-) were prepared by the reaction in THF solution of KzCOT with NpC14 and [(CzHS)4N]2P~C16, respectively. Infrared spectra of both were consistent with D8h molecular symmetry ("sandwich" compounds), and X-ray diffraction patterns showed both to be isomorphous with U(COT)*. The isomer shift of the Mossbauer spectrum of Np(COT)* was unusually positive for a Np4+ compound, indicating an electron contribution from the ligand to the bonding. The magnetic moments measured between 4.2 and 44'K were 2.43 BM for U(COT)z and 1.81 BM for Np(C0T)z; Pu(C0T)z was diamagnetic. A crystal-field model with an orbital reduction factor, k, of 0.8 is in reasonable agreement with the experimental results.he reduction of cyclooctatetraene in tetrahydro-T furan (THF) solution produces the planar CsHs2anion (COT),4s5 which can react with the anhydrous metal chlorides of transition metals to form M(COT), M2(COT)3, or M(COT)2 complexes.6 The preparation of U(COT)2 extended these complexes to actinide-Crystallographic studiess show that the U(COT)2 molecule has a "sandwich" structure, with planar eight-member COT rings above and below the U4f ion in D8h molecular symmetry. An electronic configuration has been proposed' for U(COT)2 that involves participation of the 5f orbitals in the bonding of the complex, with the orbitals of the two 5f electrons of the U4+ ion mixing with the degenerate Esu orbitals of the ligands in essentially a nonbonding combination.NP(COT)~ and PU(COT)~ were prepared to allow a more thorough investigation of the nature of the actinide(1V)-COT compounds. Mossbauer measurements on Np(COT)* provide information on the shielding of s orbitals by outer electrons, and thus on the participation of ligand electrons in the bonding. Magnetic susceptibility measurements on U(COT)z, Np-(COT)2, and Pu(COT)2 (U4+, 5f2; Np4+, 5f3; Pu4+, 5f4) narrow the choice of applicable molecular models. Experimental SectionReagents. The preparation of UCL, NpC14, and [(CZH~)~N]Y PuCl6 has been previously r e p ~r t e d . ~ Cyclooctatetraene, benzene, and toluene were of reagent grade, and were further dried by passage through 4-A molecular sieve. Dissolved oxygen was removed by repeatedly evacuating to about 0.3 atm. Tetrahydrofuran (THF) was purified by distillation from LiAlH4 in a nitrogen atmosphere. The quality of THF was found to be a major factor in the success of preparations; addition of LiAlH4 as a solution in

Potassium bis(cyclooctatetraenyl)neptunium(III) (KNp(COT)•., COT = C6H81 2~) and KPu(COT)2 were prepared as bis(tetrahydrofuran) (THF) solvates by treating the trivalent actinide bromides or iodides with K2COT in THF solution. X-Ray powder patterns indicate that these compounds are isostructural, and the similarity of the powder patterns of KPu(COT)2 • (CH30CH2)20 with the Ce3+ analog suggests that the Pu3+ ion is in a Dsd ("sandwich") site in the molecule. The Móssbauer spectrum of the Np(III) compound has an isomer shift ( ) of +3.92 cm/sec, which confirms a +3 valence with only slight covalency, and a quadrupole splitting constant {eqQj4) of 0.72 cm/sec with zero asymmetry. Magnetic susceptibility measurements on both compounds are reported and discussed in terms of crystal field models.

Magnetic susceptibilities of uranium, plutonium, and neptunium trichlorides, tribomides, and triiodides were measured from 2.7°K to as high as 240°K with a vibrating-sample magnetometer at applied fields up to 12 kOe. Antiferromagnetic transitions were observed in UCl3, TN=22.0±1.0°K; in UBr3, TN=15.0±0.5°K; in UI3, TN=3.4±0.2°K; and in PuCl3, TN=4.5±0.5°K. A ferromagnetic transition at Tc=4.75±0.1°K was found for PuI3, and a slight hysteresis was measured at 2.7°K. Temperature-independent paramagnetism was observed for NpCl3 below 50°K, for α-NpBr3 below 30°K, and for NpI3 below 15°K. All these latter compounds, and PuBr3, exhibited Curie-Weiss paramagnetism at higher temperatures, with effective moments near the free-ion moments. The experimental magnetic susceptibility of PuCl3 from 10 to 100°K agrees with the susceptibility calculated from crystal field energy levels and wavefunctions.

FePc should only reduce as a trinegative ion, if the first is discontinued, while the remainder of the metal phthalocyanine studies reduce to yield four steps, and five for CoPc. The nature of the reduced species for FePc must still remain in doubt although it seems probable that addition to the central metal ion does occur at some stage.In conclusion it must be stressed that the authors are very much aware of the possibility that the reduction processes may well be assigned to other species when more data become available especially for the complexes with cobalt and iron, and possibly manganese; however, we do believe that the configurations suggested are the most consistent with the electron spin resonance and the electronic absorption data at the present time.