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Henning Hopf

Publications and source records attributed to Henning Hopf.

7 recordsLinked to original sources
PubMed2002

Three ruthenocene derivatives: (eta(5)-4,7-dimethylindenyl)(eta(5)-pentamethylcyclopentadienyl)ruthenium(II), [eta(5)-[2](4,7)indeno[2]paracyclophanyl](eta(5)-pentamethylcyclopentadienyl)ruthenium(II) and bis[eta(5)-[2](4,7)indeno[2]paracyclophanyl]ruthenium(II).

In the title compounds, [Ru(C(10)H(15))(C(11)H(11))], (III), [Ru(C(10)H(15))(C(19)H(17))], (IV), and [Ru(C(19)H(17))(2)], (V), respectively, the coordinating ring systems are planar and parallel, with the Ru atoms lying at perpendicular distances of Ru-Cp* 1.790 (1) A and Ru-indenyl 1.836 (1) A in (III), Ru-Cp* 1.791 (1) A and Ru-indenyl 1.837 (1) A in (IV), and Ru-indenyl 1.812 (1) A and 1.809 (1) A in (V) (Cp* is pentamethylcyclopentadienyl). The ring conformations are eclipsed for (III), staggered for (IV) and intermediate for (V). All three compounds show short intermolecular contacts from C-H groups to some ring centroids; these could be regarded as C-H.pi hydrogen bonds. The molecules of each compound are thus connected via the 2(1) screw axis to form layers parallel to the xy plane.

Journal Article↗
PubMed2002

Three isomeric bis(methoxycarbonyl)[2.2]paracyclophanes.

The title isomers 4,16- (pseudo-ortho), 4,15- (pseudo-gem) and 4,12-bis(methoxycarbonyl)[2.2]paracyclophane (pseudo-para), C(20)H(20)O(4), all show the typical structural features of [2.2]paracyclophanes (flattened boat conformation of the rings, lengthened single bonds in the bridges and narrow ring angles at the bridgehead atoms). The 4,12-isomer displays crystallographic inversion symmetry. The carbonyl groups adopt a conformation in which they are directed away from the ring systems towards the nearest bridge; the corresponding angle at the ring substituent atom is widened. Crystal packing involves C-H.pi interactions for the 4,15-isomer and weak C-H.O hydrogen bonds for the other two isomers.

Journal Article↗
PubMed2002

Anionic cyclization of a cross-conjugated enediyne.

Cross-conjugated enediynes cannot follow the Bergman cycloaromatization as it involves a methylenediyne moiety with only five pi e(-), insufficient for aromatization. Under reductive conditions the cyclization is made feasible by generating a product with a Hückel number of pi electrons. We illustrate this principle and demonstrate for the first time an anionic cyclization of a cross-conjugated enediyne that results in formation of a five-membered ring. 9-(3-Phenyl-1-phenylethynylprop-2-ynylidene)-9H-fluorene (3) was reduced by potassium to yield the dianion of 9-(3,4-diphenylcyclopenta-2,4-dienylidene)-9H-fluorene (4(2-)), which contains a cyclopentadienyl fragment, and oxidation with iodine yielded the unstable fulvalene 4.

Alkynes↗