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Table 1, footnote (b). FAB should read electron impact. Left-hand column. Ref. 1 1 should be ref. 12(a).

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New compounds in which nickel is substituted for lithium in lithium nitride show evidence of high lithium vacancy concentrations and an ordering of these vacancies to form new structural variants.The chemistry of transition metal ternary nitrides has recently been the subject of intense study. 1 However, the reactions of lithium nitride with the first row transition elements were first studied over fifty years ago. 2-4 A number of different compositions and structures are observed for the resulting lithium nitridometallates, some of the most common being based either on an antifluorite structure 2 or on a modification of the lithium nitride structure itself. 3 Late first row transition nitridometallates such as those formed with Co, Ni and Cu favour this latter structure type. The transition metal (M), in these compounds, partially substitutes for lithium between Li 2 N planes to form Li 32x M x N but the limit of substitution, x, is below unity. The parent binary nitride, Li 3 N, is a lithium ion conductor. 5 Control of x has implications both structurally and in terms of the conductivity of materials. We report here the synthesis and structure of two new layered nitridonickelates.New ternary lithium nitrides were synthesised by reaction of excess lithium nitride with nickel foil under a positive pressure of nitrogen gas. All manipulations were carried out in an argon or nitrogen-filled evacuable glove box. Lithium nitride (Li 3 N) was prepared by reaction of gaseous nitrogen with cleaned lithium metal (5-6 g) dissolved in liquid sodium at 650 °C. 6 Ternary nitrides were prepared by reaction of Li 3 N with a nickel foil (99.9% BDH) tube. The tube was placed inside a stainlesssteel crucible, sealed in a stainless steel vessel under a positive pressure of nitrogen (ca. 2 atm) and heated to 750 °C for 24 h. The vessel was cooled and opened in a nitrogen filled glove box. The reaction yielded a gold coloured coating of crystalline product on the nickel foil. The air-sensitive crystals were isolated, loaded and sealed in capillaries.Structure solution and refinement reveals two distinct products with compositions Li 5 Ni 3 N 3 and LiNiN. 7 Both compounds have structures closely related to Li 3 N, with alternate layers of Li-N sheets and metal ions stacked perpendicular to the c-axis. The proposed structures of both compounds exhibit lithium vacancy ordering not seen in lithium nitride or the previously reported Li 3-x M x N compounds. Furthermore, Li ion vacancy concentrations in these lithium nitridometallates are well above the 1-2% level usually observed in Li 3 N. This Li vacancy ordering enforces changes in space group with vacancy concentration and the approximate doubling of the Li 5 Ni 3 N 3 a-parameter relative to the Li 3 N unit cell dimensions. It was almost impossible to discriminate between ordered and disordered models for the LiNiN structure by X-ray diffraction. 8 It is useful to compare and contrast the structures of the nitridonickelates and the parent compound, Li 3 N in terms of the nitrogen coord...

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The monometallic bipyridyl complexes [MoTp*(NO)X(L-L)] [Tp* = HB(3,5-Me2C3HN2)3; L-L = 3,3‘-bipyridine, 4,4‘-bipyridine, 1,2-bis(4-pyridyl)ethane and X = Cl; L-L = 4,4‘-NC5H4(CHCH) n H4C5N, n = 0, 1, 2, 3, 4 (all trans) and X = Cl, I] and their bimetallic counterparts [{(NO)MoTp*X}2(L-L)] have been synthesized, together with [MoTp*(NO)Cl{4-NC5H4CHCHC(Me)CHCH}]2. The single crystal X-ray structure of [{MoTp*(NO)Cl}2{4,4‘-NC5H4(CHCH)4H4C5N}] confirms that the polyene chain is in the all-trans configuration and exhibits normal bond length alternation with [r C  C−rC  C] = 0.092 Å. The Mo−Mo distance is 20.764(3) Å, and the Mo−N(pyridyl) bond distance of 2.196(6) Å indicates a much lower degree of Mo−(N)ligand π bonding than that found in related amide complexes where Mo−N(amide) distances are typically some 0.3 Å shorter. Cyclic voltammograms of the monometallic complexes contain a single one-electron reduction process, whereas those of the bimetallic complexes contain two one-electron processes. The separation between the two reduction potentials varies almost linearly with polyene chain length from the statistical limit of 36 mV in the bipyridyl dimethyldecapentene derivative to 765 mV in the 4,4‘-bipyridyl derivative. The isovalent bimetallic complexes exhibit EPR signals (300 K) which show hyperfine coupling to two equivalent metal centers with J ≫ A and are consistent with the unpaired electrons occupying orbitals which are predominantly metal in character. Magnetic measurements indicate the presence of an antiferromagnetic interaction in [{MoTp*(NO)Cl}2{4,4‘-NC5H4(CHCH)4H4C5N}] with a coupling −2J estimated to be ca. 80 cm-1 over a distance of ca. 2 nm.