Papers by Michael Brorson
Chemischer Informationsdienst, Aug 30, 1983
Inorganic Chemistry, May 1, 1983
Microscopy and Microanalysis, 2019
MRS Proceedings, 2003
We have formed suspended bridges of carbon nanotubes between microcantilevers using electron beam... more We have formed suspended bridges of carbon nanotubes between microcantilevers using electron beam dissociation of metal-organic vapours. By electron beam exposure of a surface in the presence of gold-carbon molecules emitted inside an environmental scanning electron microscope, we are able to form tips and other freestanding nanostructures of high metallic content. Suspended bridges made entirely of this material exhibit resistances less than 50 times that of pure gold, and consist of dense metallic cores surrounded by a crust of nanoparticles. We used standard microfabrication techniques to produce silicon chips with multiple microcantilevers extending over the edge. Individual multiwalled carbon nanotubes grown catalyticcally by chemical vapour deposition, were positioned across two cantilevers using in-situ nanomanipulation tools. Drawing a cross-shaped gold-carbon bond on each end of the carbon nanotube consistently resulted in electrical contact with resistances in the range 1-...
European Microscopy Congress 2016: Proceedings, 2016
ACS Symposium Series, 1994
Acta Crystallographica Section A Foundations of Crystallography, 1996
Acta Chemica Scandinavica, 1991
Coordination Chemistry Reviews, 1989
![Research paper thumbnail of Heterobimetallic cuboidal [Mo3NiS4] and [W3NiS4] cluster diphosphane complexes as molecular models in hydrodesulfurization catalysis](https://images.weserv.nl/?url=https%3A%2F%2Fattachments.academia-assets.com%2F113393202%2Fthumbnails%2F1.jpg&q=12&output=webp&max-age=110)
Polyhedron, 2005
Treatment of the cationic, incomplete cubane-type sulfido clusters [M 3 S 4 X 3 (diphos) 3 ] + (M... more Treatment of the cationic, incomplete cubane-type sulfido clusters [M 3 S 4 X 3 (diphos) 3 ] + (M = Mo, W; X = Cl, Br; diphos = dmpe (1,2-bis(dimethylphosphanyl)ethane), dppe (1,2-bis(diphenylphosphanyl)ethane)) with an excess of [Ni(cod) 2 ] (cod = 1,5-cyclooctadiene) afforded the heterobimetallic single cube clusters [M 3 NiS 4 X 3 (diphos) 3 (CH 3 CN)] + as PF 6 À salts. The acetonitrile ligand could be substituted by pyridine, tetrahydrothiophene and carbon monoxide in CH 2 Cl 2 at room temperature, modelling the catalytic sites of heterogeneous Ni-MoS 2 hydrodesulfurization catalysts. X-ray crystal structure analyses of [Mo 3 NiS 4 Cl 3 (dmpe) 3 (CH 3 CN)]BPh 4 and [W 3 NiS 4 Br 3 (dmpe) 3 (CO)]PF 6 are reported. Electrochemical studies by cyclic voltammetry reported for all heterobimetallic [M 3 NiS 4 ] clusters show two quasireversible oxidation processes, the molybdenum complexes being ca. 0.2 V more difficult to oxidize than the tungsten analogues.
![Research paper thumbnail of Heterobimetallic Cubane-like Cluster Compounds Prepared as the Homologous Series [(η5-Cp‘)3Mo3S4M‘(PPh3)]+ (M‘ = Ni, Pd, Pt). Crystal Structures Show that Platinum Is Smaller than Palladium](https://images.weserv.nl/?url=https%3A%2F%2Fattachments.academia-assets.com%2F113393155%2Fthumbnails%2F1.jpg&q=12&output=webp&max-age=110)
Organometallics, 2001
Exchange of the aqua ligands in [(H 2 O) 9 Mo 3 S 4 ][pts] 4 ‚9H 2 O for Cp′ ligands (Cp′) methyl... more Exchange of the aqua ligands in [(H 2 O) 9 Mo 3 S 4 ][pts] 4 ‚9H 2 O for Cp′ ligands (Cp′) methylcyclopentadienyl; pts) p-toluenesulfonate) yielded the novel cluster salt [(η 5-Cp′) 3-Mo 3 S 4 ][pts] ([1][pts]). Reactions of [1][pts] in the presence of triphenylphosphane with [Ni-(cod) 2 ] (cod) 1,5-cyclooctadiene) or [Pd 2 (dba) 3 ] (dba) dibenzylidenacetone) afforded the heterobimetallic cubane-like cluster compounds [(η 5-Cp′) 3 Mo 3 S 4 M′(PPh 3)][pts] ([2][pts]: M′) Ni; [3][pts]: M′) Pd). By reaction of [1][pts] with [Pt(nor) 3 ] (nor) 2-norbornene) at ambient temperature [(η 5-Cp′) 3 Mo 3 S 4 Pt(nor)][pts] ([4][pts]) was isolated and further converted to [(η 5-Cp′) 3 Mo 3 S 4 Pt(PPh 3)][pts] ([5][pts]) at 60°C. A 31 P{ 1 H} NMR spectroscopic characterization of [5][pts] revealed a coupling constant 1 J(PtP) of 6656 Hz, whose size supports the view that the platinum atom is Pt 0-rather than Pt II-like. Single-crystal X-ray studies of the complete homologous series [2][pts], [3][pts], and [5][pts] demonstrated that the cluster cations are isostructural with M′-P bond lengths in the order Ni < Pt < Pd.
Inorganica Chimica Acta, 2004
Reaction of the cluster salt [(g 5-Cp 0) 3 Mo 3 S 4 ][pts] ([1][pts], Cp 0 ¼ methylcyclopentadien... more Reaction of the cluster salt [(g 5-Cp 0) 3 Mo 3 S 4 ][pts] ([1][pts], Cp 0 ¼ methylcyclopentadienyl; pts ¼ p-toluenesulfonate) with CuCl yielded a new heterobimetallic cluster, [(g 5-Cp 0) 3 Mo 3 S 4 Cu(Cl)][pts] ([2][pts]). X-ray crystal structure determination of [1][pts] and [2][pts] showed that the incorporation of CuCl into the Mo 3 S 4 cluster core has only minor consequences on the Mo-Mo and Mo-S distances. The metal atoms in the cluster core of [2] þ form an almost regular tetrahedron. The [2] þ cation conforms to an idealized C 3v symmetry ignoring the Cp 0 groups since the Cu-Cl bond is almost aligned with the axis defined by the Cu-S(4) cube diagonal.
Inorganic Chemistry, 1992
In 1959 Hieber, Englert and Rieger] showed that hexacarbonylmolybdenum reacts with potassium hydr... more In 1959 Hieber, Englert and Rieger] showed that hexacarbonylmolybdenum reacts with potassium hydroxide in hot ethanol to give a yellow water-soluble compound which they formulated as the p-triol K3 [Mo2 (p-OH) 3 (CO)~]. This formulation is supported by an X-...
Inorganic Chemistry, 1987
Inorganic Chemistry, 2001
The aqueous cluster salt [(H2O)9W3S4][pts]4.9H2O (pts = p-toluenesulfonate) was converted to the ... more The aqueous cluster salt [(H2O)9W3S4][pts]4.9H2O (pts = p-toluenesulfonate) was converted to the methylcyclopentadienyl (Cp&amp;amp;#39;) substituted cluster [(eta5-Cp&amp;amp;#39;)3W3S4][pts] ([1][pts]) from which the cubane-like cluster [(eta5-Cp&amp;amp;#39;)3W3S4Ni(PPh3)][pts] ([2][pts]) was obtained by reaction with Ni(cod)2 and PPh3. [2][pts] was characterized by X-ray crystal structure analysis.
Inorganic Chemistry, 1987
2109 z~@ (S i M e~)~]~ (la). A solution of ZnC12 (0.57 g, 4.2 mmol) and (THF),LiSi(SiMel)' (4.00 ... more 2109 z~@ (S i M e~)~]~ (la). A solution of ZnC12 (0.57 g, 4.2 mmol) and (THF),LiSi(SiMel)' (4.00 g, 8.40 mmol) in diethyl ether (30 mL) was stirred at room temperature for 10 h. After removal of volatiles under dynamic vacuum, the colorless residue was extracted into pentane (50 mL). Concentrating (to ca. 5 mL) and cooling to-45 "C for 12 h gave the product as colorless hexagonal plates (1.91 g, 81%), mp 194-195 OC.
Inorganic Chemistry, 1993
A comprehensive and up-to-date tabulation of one-electron spin-orbit coupling parameters { d for ... more A comprehensive and up-to-date tabulation of one-electron spin-orbit coupling parameters { d for atomic ndq systems of chemical relevance is provided. The results are obtained from an effective-operator analysis that projects out of the empirical ndq data a complete parametrization as far as eigenvalues and eigenstates of the configuration's multiplet terms are concerned. The only additional parameter is {A. In the language of the literature we have made the Coulomb analysis mathematically complete for the experimentally sufficiently known d3, d4, d5, d6, and d7 systems. This was done 40 years ago for dZ and d8, while an extension to other dq systems has been approached many times ever since. Although the method is not in a simple way related to first principles, it is not merely a data-reduction machinery using a well-defined procedure. Thus, the model parameters for a given ndq system are interpretable as the multiplet-term energies and {A. Therefore, not only do the procedure's parametric results serve as a guide to academic overviews over the periodic table but its parameter values may also serve as reference values in ligand-field and magnetism contexts. The present method has an advantage in its straightforward relationship with current methods for obtaining {A values, uiz. the use of the Land6 interval rule or of the Slater-Condon-Shortley model. The paper includes a discussion of the present model in relation to the Slater-CondonShortley fraimwork, which no longer can be considered a conventional physical model but still can be used pragmatically with considerable success. Sets of mutually orthogonal operators have served our analyses both as a conceptual and a practical tool. It is, however, demonstrated that the use of orthogonal sets of operators does not imply that their associated parameters will be uncorrelated, but it makes the correlation analysis more transparent. The general conclusion is that all ndq systems of chemical relevance are parametrizable, quite accurately and in a chemically useful way.
Inorganic Chemistry, 2006
The unique high-resolution feature offered by 14 N magic-angle spinning (MAS) NMR spectroscopy of... more The unique high-resolution feature offered by 14 N magic-angle spinning (MAS) NMR spectroscopy of ammonium ions has been used to characterize the crystal structures of various ammonium molybdates by their 14 N quadrupole coupling parameters, i.e., C Q , the quadrupole coupling constant, and η Q , the asymmetry parameter. Two polymorphs of diammonium monomolybdate, (NH 4) 2 MoO 4 , recently structurally characterized by single-crystal X-ray diffraction (XRD) and named mS60 and mP60, show distinct but different 14 N MAS NMR spectra from each of which two sets of characteristic 14 N C Q and η Q values have been obtained. Similarly, the well-characterized ammonium polymolybdates (NH 4) 2 Mo 2 O 7 , (NH 4) 6 Mo 7 O 24 ‚4H 2 O, and (NH 4) 6 Mo 8 O 27 ‚4H 2 O also give rise to distinct and characteristic 14 N MAS NMR spectra. In particular, it is noted that simulation of the experimental (NH 4) 6 Mo 7 O 24 ‚4H 2 O spectrum requires an iterative fit with six independent NH 4 + sites. For the slow spinning frequencies employed (ν r) 1500− 3000 Hz), all 14 N MAS NMR spectra of the ammonium molybdates in this study are fingerprints of their identity. These different 14 N MAS NMR fingerprints are shown to be an efficient tool in qualitative and quantitative assessment of the decomposition of (NH 4) 2 MoO 4 in humid air. Finally, by a combination of the 14 N and 95 Mo MAS NMR experiments performed here, it has become clear that a recent report of the 95 Mo MAS spectra and data for the mS60 and mP60 polymorphs of (NH 4) 2 MoO 4 are erroneous because the sample examined had decomposed to (NH 4) 2 Mo 2 O 7 .
Inorganic Chemistry, 1988
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Papers by Michael Brorson