Nico Graw
@uni-goettingen.de
Faculty of Chemistry
Georg-August-Universität
RESEARCH, TEACHING, or OTHER INTERESTS
General Chemistry, Inorganic Chemistry, Education
Scopus Publications
Scopus Publications
Leon Kreßner, Daniel Duvinage, Pim Puylaert, Nico Graw, Regine Herbst-Irmer, Dietmar Stalke, Oliver P. E. Townrow, and Malte Fischer
American Chemical Society (ACS)
In the pursuit of terminal tin chalcogenides, heteroleptic stannylenes bearing terphenyl- and hexamethyldisilazide ligands were reacted with carbodiimides to yield the respective guanidinato complexes. Further supported by quantum chemical calculations, this revealed that the iso-propyl-substituted derivative provides the maximum steric protection achievable. Oxidation with elemental selenium produced monomeric terminal tin selenides with four-coordinate tin centers. In reactions with N2O as oxygen transfer reagent, silyl migration toward putative terminal tin oxide intermediates gave rise to tin complexes with terminal ─OSiMe3 functionality. To prevent silyl migration, the silyl groups were substituted with cyclohexyl moieties. This analogue exhibited distinctively different reactivities toward selenium and N2O, yielding a 1,2,3,4,5-tetraselenastannolane and chalcogenide-bridged dimeric compounds, respectively.
Nico Graw, Paul Niklas Ruth, Tobias Ernemann, Regine Herbst-Irmer, and Dietmar Stalke
International Union of Crystallography (IUCr)
The MetalJet X-ray source provides indium Kα radiation with a wavelength even shorter than Ag radiation. This paper reports on problematic spectral impurities and presents possible countermeasures so that collection of data with excellent quality up to a high resolution is possible. It is demonstrated that these data can be used in the refinement of a multipole model, the results of which are used for a topological analysis to assess the bonding situation in a sulfur ylide compound.
Paul Niklas Ruth, Nico Graw, Tobias Ernemann, Regine Herbst-Irmer, and Dietmar Stalke
International Union of Crystallography (IUCr)
The MetalJet source makes available new Kα radiation wavelengths for use in X-ray diffraction experiments. The purpose of this paper is to demonstrate the application of indium Kα radiation in independent-atom model refinement, as well as approaches using aspherical atomic form factors. The results vary greatly depending on the detector employed, as the energy cut-off of the Eiger2 CdTe provides a solution to a unique energy contamination problem of the MetalJet In radiation, which the Photon III detector cannot provide.
Arun Kumar, Komal Yadav, Nico Graw, Madhusudan K. Pandey, Regine Herbst‐Irmer, Upakarasamy Lourderaj, Dietmar Stalke, and Herbert W. Roesky
Wiley
AbstractReduction of LAlI2 (L=PhC(NiPr2C6H3)2) with two equivalents of KC8 in toluene affords the [2+4]cycloaddition product of a dialumene with toluene. The mechanism for the formation of product complex was investigated using density functional theory (DFT) methods.
Mohd Nazish, Christina M. Legendre, Nico Graw, Regine Herbst-Irmer, Shahila Muhammed, Pattiyil Parameswaran, Dietmar Stalke, and Herbert W. Roesky
American Chemical Society (ACS)
We present an approach for preparing chain-type unsaturated molecules with low oxidation state Si(I) and Sb(I) supported by amidinato ligands that exploit to generate heavy analogues of ethane 1,2-diimine. The reduction of antimony dihalide (R-SbCl2) with KC8 in the presence of silylene chloride afforded L─(Cl)Si═Sb─Tip (1) and L(Cl)Si═Sb─TerPh (2), respectively. Compounds 1 and 2 further undergo reduction with KC8 to produce Tip─Sb═LSi─LSi═Sb─Tip (3) and TerPh─Sb═LSi─LSi═Sb─TerPh (4). The solid-state structures and DFT studies show that all compounds have σ-type lone pairs at each Sb atom. It forms a strong pseudo-π-bond with Si. The pseudo-π-bond is formed by the hyperconjugative donation of the π-type lone pair at Sb to the Si-N σ* MO. The quantum mechanical studies indicate that compounds 3 and 4 has delocalized pseudo-π-MOs arising from hyperconjugative interactions. Hence, 1 and 2 can be considered as isoelectronic to imine, while 3 and 4 are isoelectronic to ethane-1,2-diimine. The proton affinity studies indicate that the pseudo-π-bond resulting from the hyperconjugative interaction is more reactive than the σ-type lone pair.
Tim Patten, Nico Graw, Sebastian Friedl, Dietmar Stalke, and Anna Krawczuk
Wiley
AbstractIn today's world, the development and research of optoelectronic materials and devices based on solid‐state luminescence is essential. Due to their versatile application possibilities, e.g. as light‐emitting diodes or lasers, they are already indispensable. This work presents three halogenated anthracene derivatives [9‐PPh2‐10‐X‐(C14H8)] and their respective photoluminescent behavior in solution and in the solid state. The formation of halogen–π interactions in the solid state leads to unanticipated luminescence properties for the chlorinated species, resulting in a strong bathochromic shift, green fluorescence and a longer lifetime. In contrast, the other two derivatives, which in turn form only weak π–π interactions due to a small overlap of the anthracene rings, barely change their luminescence behavior in the solid state. By employing additional charge density studies, the structure–property correlation is also investigated. In particular, focus is given to halogen bonding and halogen–π interactions and their influence on photophysical properties of the studied compounds. Through the new knowledge gained, this study will help in the future development and selective application of the photophysical properties of solid‐state luminescent materials.
Mohd Nazish, Christina M. Legendre, Nico Graw, Regine Herbst‐Irmer, Dietmar Stalke, Siddharth Sankar Dutta, Upakarasamy Lourderaj, and Herbert W. Roesky
Wiley
AbstractHerein, we report the stabilization of lithium‐ion as the source of lithium to use as a trans‐metalation reagent [{PhC(NtBu)2Si(tBu)Li}2I(tBuN)2CPh] (1). The reaction of 3 equivalents of the LSitBu (L=PhC(NtBu)2) and lithium iodide at low temperature leads to a silylene stabilized lithium‐ion with an additional coordination of amidinate ligand. Compound 1 shows two four membered and one six membered ring as confirmed by QTAIM calculations. Whereas the reaction of the LSiCl with 1.5 equivalents of carbodiimide (CyN)2C at room temperature affords compound [PhC(NtBu)2Si(Cl)(NCy)2NCy] (2) with the CN2SiN2C skeleton containing silicon as a central atom. Both the compounds were fully characterized by NMR, mass spectrometry, X‐ray crystallographic analysis, and quantum mechanical calculations.
Mohd Nazish, Yi Ding, Christina M. Legendre, Arun Kumar, Nico Graw, Brigitte Schwederski, Regine Herbst-Irmer, Parameswaran Parvathy, Pattiyil Parameswaran, Dietmar Stalke,et al.
Royal Society of Chemistry (RSC)
Silicon-boron radicals have been synthesized in high excess yield through one-pot reduction using different halogen and organic substituents. Further Si–B radical undergoes oxidative addition of bromine and selenium leading to the formation of compounds 4 and 5.
Arun Kumar, Samya Banerjee, Nishant Sharma, Mohd Nazish, Nico Graw, Regine Herbst-Irmer, Dietmar Stalke, Upakarasamy Lourderaj, and Herbert W. Roesky
Royal Society of Chemistry (RSC)
Synthesis, crystal structure, and DFT study of amidinate compounds with Al(ii)–Al(ii) and Ga(ii)–Ga(ii) bonds as dihalide dimers.
Ekta Nag, Aditya Kulkarni, Sai Manoj N. V. T. Gorantla, Nico Graw, Maria Francis, Regine Herbst-Irmer, Dietmar Stalke, Herbert W. Roesky, Kartik Chandra Mondal, and Sudipta Roy
Royal Society of Chemistry (RSC)
Fluorescent diarylchlorostibane, distibane are utilized as precursors for syntheses of redox-active dimeric/trimeric alkali-metal antimonides by reductive dehalogenation. DFT and EDA-NOCV analysis are performed to shed light on the electron transfer mechanism.
Nico Graw and Dietmar Stalke
International Union of Crystallography (IUCr)
The ability to imagine symmetry and the spatial arrangement of atoms and molecules is crucial in chemistry in general. Teaching and understanding crystallography and the composition of the solid state therefore require understanding of symmetry elements and their relationships. To foster the student's spatial imagination, models representing a range of concepts from individual rotation axes to complete space groups have been designed and built. These models are robust and large enough to be presented and operated in a lecture hall, and they enable students to translate conventional 2D notations into 3D objects and vice versa. Tackling them hands-on means understanding them.
Samya Banerjee, Chowan Ashok Kumar, Sanjoy Bose, Samir Kumar Sarkar, Sandeep K Gupta, Nico Graw, Christian Köhler, Regine Herbst‐Irmer, Dietmar Stalke, Sayan Dutta,et al.
Wiley
AbstractSynthesis of four and five coordinated aluminum amidinate (PhC(NtBu)2=L) compounds are reported herein along with their single‐crystal X‐ray structures and detailed characterizations using both, experimental and computational techniques. LAlCl2 (1) and L2AlCl (2) were synthesized by treating AlCl3 with PhC(NtBu)2Li in an equivalent ratio of 1 : 1 and 1 : 2, respectively. [LAl(C2H5)Cl] (3) was prepared from a reaction of AlCl2(C2H5) with PhC(NtBu)2Li in an equivalent ratio of 1 : 1. Reactivity of 3, an amidinate based organo‐aluminum compound is explored for the various reactions. 3 produced [LAl(C2H5)(μ‐F)]2 (4) on treatment with Me3SnF. Interestingly, [LAl(C2H5)Cl] (3) was converted to [LAlCl(μ‐OEt)]2 (5) when refluxed in Et2O. 3 gives the monomeric and neutral cyclic (alkyl)(amino) carbene (cAAC) based radical [LAl(C2H5)(cAAC)] (6) on reduction with KC8 in the presence of cAAC.
Samya Banerjee, Sayan Dutta, Samir Kumar Sarkar, Nico Graw, Regine Herbst-Irmer, Debasis Koley, Dietmar Stalke, and Herbert W. Roesky
Royal Society of Chemistry (RSC)
Synthesis, crystal structure and DFT study of β-diketiminate stabilized In(ii)–In(ii) bond and bis(amidinato)indium(iii) monohalides.
Mujahuddin M. Siddiqui, Samya Banerjee, Sanjoy Bose, Samir Kumar Sarkar, Sandeep K. Gupta, Johannes Kretsch, Nico Graw, Regine Herbst-Irmer, Dietmar Stalke, Sayan Dutta,et al.
American Chemical Society (ACS)
Neutral, mononuclear aluminum and gallium radicals, stabilized by cyclic (alkyl)(amino)carbene (cAAC), were synthesized. LMCl2 upon reduction with KC8 in the presence of cAAC afforded the radicals LMCl(cAAC), where L = PhC(NtBu)2 and M = Al (1), Ga (2). The radicals were characterized by X-ray crystallography, electron paramagnetic resonance (EPR) spectroscopy, and mass spectrometry. EPR, SQUID measurement, and computational calculations confirmed paramagnetism of the radicals with unpaired spin mainly on cAAC.
Mingdong Zhong, Yashuai Liu, Subrata Kundu, Nico Graw, Jiancheng Li, Zhi Yang, Regine Herbst-Irmer, Dietmar Stalke, and Herbert W. Roesky
American Chemical Society (ACS)
Carbenes are known as donor molecules to form with chloroalane adducts, which enhances their aerobic and thermal stabilities. In contrast, the insertion products (cAACH)AlCl2(cAAC) (1) and (cAACH)AlHCl(THF) (2; THF = tetrahydrofuran) have been formed in the reaction of a cyclic alkyl(amino)carbene (cAAC:) with HAlCl2, and H2AlCl, respectively. PhC(NtBu)2Li as the precursor for the reaction with HAlCl2 in a molar ratio of 2:1 can easily form compound [PhC(NtBu)2]2AlH (3) with five-coordinate aluminum. The new products have been studied by spectroscopic methods and single-crystal X-ray diffraction.
Ingo Koehne, Nico Graw, Thorsten Teuteberg, Regine Herbst-Irmer, and Dietmar Stalke
American Chemical Society (ACS)
Within this work, the field of bulky methanides in metal coordination is exceeded by the synthesis of the versatile and promising bis(4,6-isopropylbenzoxazol-2-yl)methane (7) ligand platform. As an enhancement in this class of ligands, isopropyl (iPr) substituents as steric-demanding groups have been successfully introduced in proximity to the coordination pocket, mimicking the shielding abilities of the ubiquitous NacNac ligand scaffold to improve the steric protection of a coordinated s-block metal cation. A percent buried volume (% Vbur) calculation as well as an electronic structure analysis shades light onto the shielding and electronic abilities of the ligand in comparison to other selected methanides and diketiminates. Upon deprotonation with a variety of different group 1 and 2 metalation agents, a row of novel s-block metal complexes of the parent deprotonated monoanionic ligand 7 was obtained and structurally, as well as spectroscopically, characterized. In particular, in this context, the alkali-metal precursor complexes [Li(THF)2{(4,6-iPr-NCOC6H2)2CH}] (8) and [K{μ-(4,6-iPr-NCOC6H2)2CH}]∞ (9) as well as the alkaline-earth-metal compounds [MgCl(THF)2{(4,6-iPr-NCOC6H2)2CH}] (10) and [M(THF)n{(4,6-iPr-NCOC6H2)2CH}2] [M = Mg, n = 0 (11); M = Ca, n = 1 (12); M = Sr, n = 1 (13); M = Ba, n = 1 (14)] were successfully synthesized. Especially, the latter four exhibit interesting trends in the solid state as well as in solution within the metal series.