Tag Archives: Impossible Molecules

Grignard Goes Inorganic

Great news for the inorganic chemists!!! A classical strategy widely used for decades in organic chemistry is now available for the synthesis of bimetallic species. A new Mn-Mg bonded compound was recently discovered by the group of Cameron Jones in Australia while trying to synthesise new Mn-Mn complexes. The direct comparison with the well known Grignard reagents gives the new Mn-Mg based complex the qualification of “inorganic Grignard reagent”.

inorganic grignard

Normal Grignard reagents, or maybe more correctly now Organic Grignard reagents, are organomagnesium based strong nucleophiles used mainly but not exclusively for the formation of carbon-carbon bonds. Discovered by French chemist François Auguste Victor Grignard who was awarded the 1912 Nobel Prize in Chemistry, Grignard reagents have become an essential tool in organic synthesis.

reacciones_2

The inorganic version, the so called “Inorganic Grignard reagents”, are not a new concept although their use is yet far from been a general tool for the creation of metal-metal bonds. The new Mn-Mg bonded compound discovered by Jones and co-workers was successfully utilised to transfer the Manganese fragment for the preparation of the first two-coordinate manganese(I) dimer, and the related Mn-Cr hetereobimetallic complex.

Do you want to know more? Take a look to the original paper.

Jamie Hicks, Chad E. Hoyer, Boujemaa Moubaraki, Giovanni Li Manni, Emma Carter, Damien M. Murphy, Keith S. Murray, Laura Gagliardi, and Cameron Jones. A Two-Coordinate Manganese(0) Complex with an Unsupported Mn–Mg Bond: Allowing Access to Low Coordinate Homo- and Heterobimetallic Compounds. J. Am. Chem. Soc., 2014, 136, 5283–5286.

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A NanoCar for NanoKid.

Molecular motors are biological molecular machines that convert energy into motion or mechanical work participating in many important processes such as muscle contraction, intracellular cargo transport or transcription of RNA from DNA. Thus, it is natural that these systems serve as an inspiration for chemists on the search for new and more complex synthetic machine-like functions.

In 1999 Feringa and co-workers at the University of Groningen (Netherlands) designed a synthetic molecular rotor, activated by ultraviolet light, capable of performing unidirectional 360o rotation and more recently in 2011 they took the concept one step further by synthesising a light-driven nanocar.

nanokid_nanocar

The car composed by a carbazole substituted diphenylbutadiyne chassis and 4 fluorene-based molecular motors acting as wheels can travel as far as 6 nm across a Cu(111) surface in 10 excitation steps. Movement requires that the adsorption energy of the molecule is less than the energy released in the isomerization step upon excitation and each cycle of unidirectional rotation takes 4 reaction steps: 1 double-bond isomerization induced by electronic excitation followed by 1 helix inversion induced by vibrational excitation and again 1 more double-bond isomerization and 1 more helix inversion to complete a 360o  rotation.

I can imagine  a teenager NanoKid, the kid-shaped organic molecule from the series of Nanoputians, asking his NanoDaddy to buy him the last model of NanoCar capable of running 6 nm in 10 electric bursts. Although, I don’t think NanoMum likes the idea…

Do you want to know more? Then, go directly to the sources:

Nagatoshi Koumura, Robert W. J. Zijlstra, Richard A. van Delden, Nobuyuki Harada, Ben L. Feringa. Light-driven monodirectional molecular rotor. Nature 401, 152-155 (9 September 1999).

Tibor Kudernac, Nopporn Ruangsupapichat, Manfred Parschau, Beatriz Maciá, Nathalie Katsonis, Syuzanna R. Harutyunyan, Karl-Heinz Ernst, Ben L. Feringa. Electrically driven directional motion of a four-wheeled molecule on a metal surface. Nature 479, 208–211 (10 November 2011).

An Unusual Lewis Acid Hydrocarbon.

I would like to highlight the definition of hydrocarbon, a very basic concept in organic chemistry but of relevance for this post. According to the IUPAC, hydrocarbons are compounds consisting of carbon and hydrogen only. It doesn’t seem obvious to imagine an organic compound composed only by carbon and hydrogen with Lewis acidity not being a charged species such as a carbocation. Back in 2010 the group of Manuel Alcarazo at Max Planck Institute of Coal Research published a  very creative paper describing the properties of a bisfuorenylallene as a Lewis acid. The natural tendency of the fluorene moites to accept a pair of electrons to gain aromatization gives the central carbon of the allene a carbocationic character and thus the ability to behave as a Lewis acid.

Unsual hydrocarbon lewis acid

A clear experimental evidence of the behaviour of the bisfluorenylallene as a Lewis acid is the formation of classical Lewis acid-Lewis base adducts in the presence of small Lewis bases. In another stroke of genius, Acarazo and co-workers apply the Lewis acid ability of the fluorenyl based allene to the field of Frustrated Lewis Pairs (a field dominated by borane-based Lewis acids) towards the activation of sufur-sulfur bonds.

Do you want to know more? Check this paper out.

Blanca Ins, Sigrid Holle, Richard Goddard, and Manuel Alcarazo. Heterolytic S-S Bond Cleavage by a Purely Carbogenic Frustrated Lewis Pair. Angew. Chem. Int. Ed. 2010, 49, 8389 –8391.

Nanoputians: Nanoscale Human Figures.

Although this is not new material,  I would like to open  Nanoputianmy section of “Impossible molecules” with a great example of creativity and tons of good sense of humour in organic chemistry: The Nanoputians. Back in 2003, James Tour and colleagues published a paper in Journal of Organic Chemistry where they describe the synthesis of an array of human-shaped organic molecules they called Nanoputians as a reference to the well known small characters, the Lilliputians, from the classic Gulliver’s travels . A very educational paper, ideal for undergrads and organic chemistry newcomers. It is very enjoyable the way they describe the synthesis of their Nanoputians using body-part-like descriptions and the originality of the names given to the molecules for a nano-universe with Nanokids, Nanobakers, Nanoballetdancers and more.  I could not say how many  organic chemistry papers I have read in my life so far, but there is no doubt that I will always remember Nanoputians and I am completely sure I will not be the only one.

Do you want to know more? Read the original papers.

Chanteau, S. H.; Tour, J. M. “Synthesis of Anthropomorphic Molecules:  The NanoPutians”. The Journal of Organic Chemistry 2003, 68, 8750–8766.

Chanteau, S. H.; Ruths, T.; Tour, J. M. “Arts and Sciences Reunite in Nanoput: Communicating Synthesis and the Nanoscale to the Layperson”. Journal of Chemical Education 2003, 80, 395.