Roger C. Pettersen

Sesquiterpenes from Flourensia cernua

Abstract The common western shrub Flourensia cernua has yielded the eremophilane sesquiterpene flourensic acid and a new aromadendrane sesquiterpene flourensadiol. The toxic component(s) of the plant were found in a petrol-soluble fraction.

The X-ray structure of [Me3SiC4SiMe3]2Fe2(CO)7: a σ—π-type bonding complex between a diacetylene and Iron carbonyl

Abstract The photochemical reaction of bis-(trimethylsily) butediyne, Me3SiC4SiMe3, with Fe(CO)5 in benzene yields a product of formula [Me3C4SiMe3]2Fe2(CO)7, II. The formula and molecular structure were determined by single crystal x-ray analysis. The results correct a structure (I) previously proposed based on spectroscopic evidence. The red crystals are monoclinic, space group I2/a with a = 21.647(6), b = 8.924(2), c = 19.544(8) A, β = 96.09(3]° and Z = 4. Anisotropic refinement of 21 independent atoms with 872 observed reflections converged at R = 0.062 and Rw = 0.064. The molecule II is made up of two diacetylene ligands, an inserted CO group and an (CO)3Fe-Fe(CO)3 group. The diacetylene ligands line up in a “head-to-head” arrangement and combine with the CO and iron carbonyl through reaction off one of the triple bonds. The two reactive carbon atoms from one ligand π-bond to one iron atom, while one of these carbon atoms σ-bonds to the second iron atom. The reverse occurs for the second ligand. A molecule of CO inserts and bridges between carbon atoms of each ligand substituted with SiMe3. The other carbon atoms which σ-bond to the iron atoms are substituted with CCSime3. Three isomers are possible for this reaction, but II is the only one observed.

Photochemical and thermal reactions of iron pentacarbonyl with dimethyldiacetylene (DMDA): spectral characterization of reaction complexes

Abstract A series of photochemical and thermal reactions has been carried out with iron pentacarbonyl and the conjugated alkadiyne dimethyldiacetylene (DMDA). One product (DMDA)Fe(CO) 6 , was prepared directly from starting materials in tetrahydrofuran under photochemical conditions. Previously analogs of this complex had been prepared only under thermal conditions from complex intermediates. An X-ray analysis has established the structure of this complex; 13 C NMR and other spectral data reported here are in agreement. Under thermal conditions in xylene, three isomeric forms of a tricarbonylferroleiron tricarbonyl (DMDA) 2 Fe 2 (CO) 6 complex were prepared. Separation and purification of two of these isomers was achieved; selected spectral data are reported. Infrared and mass spectra are also reported for the complex (DMDA) 2 Fe(CO) 4 resulting from the photochemical reaction of starting materials in cyclohexane.

X-Ray crystal and molecular structure of [Et2NCFe(CO)3]2: an example of the division of an alkyne into two separate units by rupture of the CC bond

X-Ray crystallography of the complex [Et2NCFe(CO)3]2 obtained from Fe(CO)5 and Et2NCCNEt2 indicates rupture of the carbon–carbon triple bond during the formation of this iron complex to give two separate bridging Et2NC (diethylimmoniocarbene) units.

The crystal and molecular structure of fluorensadiol, a natural product sesquiterpene isolated from a West Texas shrub

Flourensadiol, C15Hz602, is a newly discovered aromadendrane sesquiterpene isolated from the common western shrub Flourensia cernua. The compound crystallizes in space group P212~21 with a = 8.401 (4), b= 16.318 (3), c=20-251 (4) ~, and Z = 8. The structure was solved by direct-phasing methods and refined by block-diagonal least-squares calculations to a weighted R value of 0.077 and an unweighted R value of 0-078. The basic skeletal structure of flourensadiol was found to be tricyclic, consisting of a cyclopropane ring fused to a hydroazulene moiety. The two independent molecules in the asymmetric unit are virtually identical except for the orientation of a hydroxymethyl group. A network of hydrogen bonding is observed in the molecular packing arrangement.

Synthesis and crystal structure of [{Mn(η-C5H4Me)(CO)2}2{µ-(2–3-η:4–5-η)-MeCCCCMe}], a manganese-conjugated diacetylene complex

The photochemical reaction of hexa-2,4-diyne and [Mn(η-C5H4Me)(CO)3] gives as the single product the title compound (13), which has been unambiguously identified by X-ray crystallography. The compound crystallizes in the monoclinic space group P21/a with a= 10.073(4), b= 13.302(7), c= 8.012(3)A, β= 105.52(4)°, and Z = 2. The structure has been solved by the heavy-atom method and refined by least squares to final agreement indices of R= 0.034 and R′= 0.042 for 944 reflections. Structural and i.r. data suggest that the alkyne ligand in (13) is a good σ donor but a poor π acceptor. This is the first crystallographic study of a [Mn(η-C5H4R)(CO)2(alkyne)] species, even though many such compounds are known.

Photochemical reaction of a conjugated diacetylene with iron pentacarbonyl; preparation and structure of tetracarbonyl(2-methyl-3-prop-1-ynylmaleoyl)iron(O)

U.v. irradiation of Fe(CO)5 and dimethyldiacetylene (DMDA) in tetrahydrofuran gave tetracarbonyl-(2-methyl-3-prop-1-ynylmaleoyl)iron(o), (1); its structure has been determined by X-ray crystallography.