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Density functional calculations were performed on a series of M(OH3)-substituted (M = Ti, V) cyclopolyenes as simple models of metal carbides and oligomerization of the metal acetylide complexes {M(OH)(sub 3)}(sub 2)(mu-C2) as a possible precursor of these [(OH)(sub 3)MC](sub n) (n = 4, 6) hypothetical species are studied. The comparison of the electronic structure of these metal substituted cyclopolyenes with those of the corresponding cyclopolyenes has shown that these species should be more reactive toward both electrophilic and nucleophilic attacks.

The extended Huckel tight binding method was used in determining the electronic structures of the carbides Tm2Fe2Si2C, Th2Re2Si2C, ThFe2SiC and Ho2Cr2C3 and the d-electron counts of their transition metal atoms Cr, Fe, Re and the bonding of their linear M-C-M units where M = Cr, Fe and Re. Results indicate that the M-C bonds of the M-C-M units were observed to be double bonds. The 14 MOs of the linear M-C-M units in R2Fe2Si2C and R2Re2Si2C are completely filled because the Si 3p level function as acceptor levels for these MOs.

Single-crystal X-ray counter data provided the crystal structure of Gd2B3C2. The boron-carbon structural alignment of the B-C net in Gd2B3C2 explains a formal charge of 5- per B3C2 unit. The electronic structure of the boron-carbon layers observed in ThB2C and alpha-UB2C structures is strongly associated with that of the anionic two-dimensional boron-carbon layers.

Magnesium sesquicarbide (Mg2C3) was prepared from pulverized magnesium and n-pentane vapor dried with sodium. The PXD diagram of the carbide revealed an orthorhombic unit cell with the dimensions a = 6.4108(3) Angstrom (A), b = 5.2786(2) A and c = 3.7283(2) A. The carbide consists of three-membered carbon groups with C-C bond lengths of 1.332(2) A which exhibit isoelectronic behavior. This structure is attributed to the carbide's low ionicity which allows the electron-deficient Mg atoms to coordinate with both the terminal and central atom of the C3 group.

The complex Fe3Ru5(mu6-C)(mu5-C)(mu-PPh2)2(CO)17 resulted from the reaction of Ru5(mu5-C2PPh2)(mu-PPh2)(CO)13 with Fe2(CO)9. The complex was formed through the cleavage of the P-C(sp) and C-triple bond-C bonds in Ru5(mu5-C2PPh2)(mu-PPh2)(CO)13 and of a Ru-Ru bond with the subsequent Fe3 unit insertion into the C-triple bond-C bond. The complex has a metal core with face-sharing Fe2Ru3C and Fe3Ru3C carbide clusters.

The redox condensation of (PPN)2(Os3 CO 9 CCO) and Ni(CO)4 yielded the seven-metal carbide cluster (PPN)2(Os3Ni4C CO 15). The compound consists of a carbide ligand which occupies the center of a trigonal prism of two Os atoms and four Ni atoms. A square face of two Ni and two Os atoms is capped by an Os atom. This Os atom is not joined to the carbide. Unbridged bonds are approximately 0.15 Angstrom longer than the Ni-Ni bonds bridged by CO.