We wish to report the synthesis and structural and partial spectral characterization of a novel Ni(0) complex of a planar dehydroannulene,l complex I (Figure 1). The incorporation of a nickel atom into the cavity of the dehydroannulene I1 leads to novel chemistry when compared to transition-metal complexes of other unsaturated hydrocarbon^^-^ and provides compelling

Reaction of Ni(COD)2 with TBC in benzene affords a planar nickel(0) complex, Ni(TBC), with the nickel atom coordinated equally by all three alkynes of the TBC ligand. The complex crystallizes in the noncentrosymmetric space group Pna21 with a = 15.518 (3) A, b = 18.761 (4) A, c = 5.375 (1) A, V = 1564.8 (5) A3, and 2 = 4. The nickel-carbon and carbon-carbon (alkyne) bond lengths average 1.958 (5) and 1.240 (10) A, respectively. The molecules are slipped-stacked in an eclipsed conformation with an interplanar spacing of 3.35 (1) A. The reaction chemistry of Ni(TBC) with several small molecules including H20, CDC13, CO, COz, 02, and CH&N has been explored. The rates of reaction with CO and O2 are solventdependent. Electrochemical studies of Ni(TBC) and TBC show two reduction waves which are moderately reversible. ASED-MO calculations on Ni(TBC) indicate the HOMO is primarily metal centered, whereas the LUMO is ligand centered. Ni(TBC) is reduced with lithium, sodium, and potassium in various solvents (THF and DME) in the presence of various chelating agents (TMEDA, 18-crown-6, and cryptand-(2.2.2)) to the monoanion and dianion. The material [K(C222)I2[Ni(TBC)] was combined with Ni(TBC) to yield a conducting material. The maximum conductivity (via two-probe powder compaction) was observed to be 2 X (a cm)-' at 0.5 electron per Ni(TBC) unit. A parallel study on TBC showed a maximum conductivity of 8 (2) X 10" (a cm)-' at 0.6 electron per TBC unit. IntroductionTransition-metal complexes of planar metallomacrocycles, including ligand systems such as the porphyrins' and phthalocyanines,2 have been studied in depth as precursors for one-dimensional conductors. These complexes have several key features in common: the molecules are planar with an extended mystem, the ligand atoms which complex the metal are relatively hard nitrogen donors, the ligand has a formal negative oxidation state, and

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CF3SO3Ag reacts with the macrocyclic triyne ligand in THF in different ratios within several days to give the title complex (I) (yield 5‐10%) and polymerized THF.

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