John D. Bradshaw

Reaction chemistry, NMR spectroscopy, and X-ray crystallography of [Fe2(μ-SiMe2)2(CO)4] and [Fe2(μ-SiMeCl)2(CO)4]. Electronic structure and bonding in Fe2E2 rings of [Fe2(μ-ER2)2(CO)4] binuclear complexes (E=C, Si, Ge, Sn, Pb)

Abstract The rings [Fe2(μ-SiRR′)2(CO)8] (R=Me, R′=Me or Cl) react with HMPA to give the base-stabilized silylenes [Fe(SiRR′(HMPA))(CO)4]. The reactions of [Fe2(μ-SiMe2)2(CO)8] with DABCO, THF and PMe3 have also been examined. The crystal structures of both [Fe2(μ-SiMe2)2(CO)8] and [Fe2(μ-SiMeCl)2(CO)8] show planar rings, CH⋯OC short contacts and relatively short but non-bonding SiSi distances. The possibility of through-ring MM or EE bonding in complexes of the type [M2(μ-ER2)2(CO)8] (M is a transition metal and E is a Group 14 element) is analyzed with the help of theoretical calculations based on density functional theory. For compounds with 20 ring electrons (or a framework electron count, FEC, of eight), regular M2E2 rings are expected, with no short through-ring distances. The framework electron counting rules, geometry optimization of several model complexes and a structural database analysis consistently indicate that through-ring bonding exists only when the FEC is less than eight. In that case, the isomer with a short metal–metal bond is found to be significantly more stable than that with a short EE distance.

Syntheses and crystal structures of 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC), 1,2:5,6:9,10:13,14-tetrabenzo-3,7,11,15-tetradehydro[16]annulene (QBC) and a tetracobalt complex of QBC. The first example of a transition metal complex of QBC

1,2:5,6:9,10:13,14-Tetrabenzo-3,7,11,15-tetradehydro[16]annulene, or tetrabenzocyclyne (QBC) and 1,2:5,6:9,10:13,14:17,18:21,22-hexabenzo-3,7,11,15,19,23-hexadehydro[24]annulene (HBC) have been structurally characterized by X-ray. crystallography. QBC crystallizes in two different space groups; P21/c with a = 10.652(3) A, b = 10.624(2) A, c = 19.549(4) A, β = 93.83(2)°, V = 2207.4(8) A3, and Z = 4 and P41212 with a = 9.330(1) A, c = 25.497(8) A, V = 2219.6(12) A, and Z = 4. HBC crystallizes in monoclinic P21/n with a = 14.763(3) A, b = 10.296(2) A, c = 22.057(4) A, β = 108.61(3), V = 3177.4(11) A3, T = 133 K, and Z = 4. Reaction of QBC with dicobaltoctacarbonyl has produced a tetracobalt complex which has been characterized by X-ray crystallography. This complex crystallizes in monoclinic P21/c with a = 14.699(3) A, b = 17.188(3) A, c = 17.254(3) A, β = 112.63(3)°, V = 4023.5(13) A3, and Z = 4. Only two of the four CC triple bonds of QBC bind to dicobalthexacarbonyl moieties even when excess dicobaltoctacarbonyl is used.

Aryl nitro group substitution by primary and secondary amines

Abstract Primary and secondary amines react with 1,2-dihalo-4,5-dinitrobenzene to give nitro group substitution at mild temperatures. The halogen substituents on the ring remain unsubstituted and can be used for further reaction chemistry.

Synthesis and crystal structure of 1,2:7,8 : 13,14:19,20-tetrabenzocyclotetracosa-1,7,13,19-tetraene-3,5,9,11,15,17,21,23-octayne

The title compound has been synthesized in a relatively high yield by the Glaser coupling reaction and characterized by X-ray crystallography and spectroscopy.