@article{FoehrenbacherKrahfussZapfetal.2021, author = {F{\"o}hrenbacher, Steffen A. and Krahfuss, Mirjam J. and Zapf, Ludwig and Friedrich, Alexandra and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo}, title = {Tris(pentafluoroethyl)difluorophosphorane: a versatile fluoride acceptor for transition metal chemistry}, series = {Chemistry Europe}, volume = {27}, journal = {Chemistry Europe}, number = {10}, doi = {10.1002/chem.202004885}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256665}, pages = {3504-3516}, year = {2021}, abstract = {Fluoride abstraction from different types of transition metal fluoride complexes [L\(_n\)MF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C\(_2\)F\(_5\))\(_3\)PF\(_2\) to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C\(_2\)F\(_5\))\(_3\)PF\(_3\)]\(^-\)) is reported. (C\(_2\)F\(_5\))\(_3\)PF\(_2\) reacted with trans-[Ni(iPr\(_2\)Im)\(_2\)(Ar\(^F\))F] (iPr2Im=1,3-diisopropylimidazolin-2-ylidene; Ar\(^F\)=C\(_6\)F\(_5\), 1 a; 4-CF\(_3\)-C\(_6\)F\(_4\), 1 b; 4-C\(_6\)F\(_5\)-C\(_6\)F\(_4\), 1 c) through fluoride transfer to form the complex salts trans-[Ni(iPr\(_2\)Im)\(_2\)(solv)(Ar\(^F\))]FAP (2 a-c[solv]; solv=Et\(_2\)O, CH\(_2\)Cl\(_2\), THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh\(_3\), solvent coordination was suppressed and the complexes trans-[Ni(iPr\(_2\)Im)\(_2\)(PPh\(_3\))(C\(_6\)F\(_5\))]FAP (trans-2 a[PPh\(_3\)]) and cis-[Ni(iPr\(_2\)Im)\(_2\)(Dipp\(_2\)Im)(C\(_6\)F\(_5\))]FAP (cis-2 a[Dipp\(_2\)Im]) (Dipp\(_2\)Im=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were isolated. Fluoride abstraction from [(Dipp\(_2\)Im)CuF] (3) in CH\(_2\)Cl\(_2\) or 1,2-difluorobenzene led to the isolation of [{(Dipp\(_2\)Im)Cu}\(_2\)]\(^2\)\(^+\)2 FAP\(^-\) (4). Subsequent reaction of 4 with PPh\(_3\) and different carbenes resulted in the complexes [(Dipp\(_2\)Im)Cu(LB)]FAP (5 a-e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp\(_2\)Im)Cu(C\(_6\)Me\(_6\))]FAP (5 f), which serves as a source of [(Dipp\(_2\)Im)Cu)]\(^+\). Fluoride abstraction of [Cp\(_2\)TiF\(_2\)] (7) resulted in the formation of dinuclear [FCp\(_2\)Ti(μ-F)TiCp\(_2\)F]FAP (8) (Cp=η\(^5\)-C\(_5\)H\(_5\)) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand.}, language = {en} } @article{HorrerKrahfussLubitzetal.2020, author = {Horrer, G{\"u}nther and Krahfuß, Mirjam J. and Lubitz, Katharina and Krummenacher, Ivo and Braunschweig, Holger and Radius, Udo}, title = {N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Complexes of Titanium(IV) and Titanium(III)}, series = {European Journal of Inorganic Chemistry}, volume = {2020}, journal = {European Journal of Inorganic Chemistry}, number = {3}, doi = {10.1002/ejic.201901207}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208725}, pages = {281-291}, year = {2020}, abstract = {The reaction of one and two equivalents of the N -heterocyclic carbene IMes [IMes = 1,3-bis(2,4,6-trimethyl-phenyl)imidazolin-2-ylidene] or the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) [cAAC\(^{Me}\) = 1-(2,6-diisopropyl-phenyl)-3,3,5,5-tetra-methylpyrrolidin-2-ylidene] with [TiCl\(_{4}\)] in n -hexane results in the formation of mono- and bis-carbene complexes [TiCl\(_{4}\)(IMes)] 1 , [TiCl\(_{4}\)(IMes)2] 2 , [TiCl\(_{4}\)(cAAC\(^{Me}\))] 3 , and [TiCl\(_{4}\)(cAAC\(^{Me}\))\(_{2}\)] 4 , respectively. For comparison, the titanium(IV) NHC complex [TiCl\(_{4}\)(Ii Pr\(^{Me}\))] 5 (Ii Pr\(^{Me}\) = 1,3-diisopropyl-4,5-dimethyl-imidazolin-2-ylidene) has been synthesized and structurally characterized. The reaction of [TiCl\(_{4}\)(IMes)] 1 with PMe\(_{3}\) affords the mixed substituted complex [TiCl\(_{4}\)(IMes)(PMe\(_{3}\))] 6 . The reactions of [TiCl\(_{3}\)(THF)\(_{3}\)] with two equivalents of the carbenes IMes and cAAC\(^{Me}\) in n -hexane lead to the clean formation of the titanium(III) complexes [TiCl\(_{3}\)(IMes)\(_{2}\)] 7 and [TiCl\(_{3}\)(cAAC\(^{Me}\))\(_{2}\)] 8 . Compounds 1 -8 have been completely characterized by elemental analysis, IR and multinuclear NMR spectroscopy and for 2 -5 , 7 and 8 by X-ray diffraction. Magnetometry in solution, EPR and UV/Vis spectroscopy and DFT calculations performed on 7 and 8 are indicative of a predominantly metal-centered d\(^{1}\)-radical in both cases.}, language = {en} } @article{LorkowskiKrahfussKubickietal.2019, author = {Lorkowski, Jan and Krahfuß, Mirjam and Kubicki, Maciej and Radius, Udo and Pietraszuk, Cezary}, title = {Intramolecular Ring-Expansion Reaction (RER) and Intermolecular Coordination of In Situ Generated Cyclic (Amino)(aryl)carbenes (cAArCs)}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {48}, doi = {10.1002/chem.201902630}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-212496}, pages = {11365 -- 11374}, year = {2019}, abstract = {Cyclic (amino)(aryl)carbenes (cAArCs) based on the isoindoline core were successfully generated in situ by α-elimination of 3-alkoxyisoindolines at high temperatures or by deprotonation of isoindol-2-ium chlorides with sodium or copper(I) acetates at low temperatures. 3-Alkoxy-isoindolines 2 a,b-OR (R=Me, Et, iPr) have been prepared in high yields by the addition of a solution of 2-aryl-1,1-diphenylisoindol-2-ium triflate (1 a,b-OTf; a: aryl=Dipp=2,6-diisopropylphenyl; b: Mesityl-, Mes=2,4,6-trimethylphenyl) to the corresponding alcohol (ROH) with NEt3 at room temperature. Furthermore, the reaction of 2 a,b-OMe in diethyl ether with a tenfold excess of hydrochloric acid led to the isolation of the isoindol-2-ium chlorides 1 a,b-Cl in high yields. The thermally generated cAArC reacts with sulfur to form the thioamide 3 a. Without any additional trapping reagent, in situ generation of 1,1-diphenylisoidolin-3-ylidenes does not lead to the isolation of these compounds, but to the reaction products of the insertion of the carbene carbon atom into an ortho C-H bond of a phenyl substituent, followed by ring-expansion reaction; namely, anthracene derivatives 9-N(H)aryl-10-Ph-C14H8 4 a,b (a: Dipp; b: Mes). These compounds are conveniently synthesized by deprotonation of the isoindol-2-ium chlorides with sodium acetate in high yields. Deprotonation of 1 a-Cl with copper(I) acetate at low temperatures afforded a mixture of 4 a and the corresponding cAArC copper(I) chloride 5 a, and allowed the isolation and structural characterization of the first example of a cAArC copper complex of general formula [(cAArC)CuCl].}, language = {en} } @article{TenderaHelmKrahfussetal.2021, author = {Tendera, Lukas and Helm, Moritz and Krahfuss, Mirjam and Kuntze-Fechner, Maximilian W. and Radius, Udo}, title = {Case Study of N-\(^{i}\)Pr versus N-Mes Substituted NHC Ligands in Nickel Chemistry: The Coordination and Cyclotrimerization of Alkynes at [Ni(NHC)\(_{2}\)]}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {71}, doi = {10.1002/chem.202103093}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257137}, pages = {17849-17861}, year = {2021}, abstract = {A case study on the effect of the employment of two different NHC ligands in complexes [Ni(NHC)\(_{2}\)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\) 1\(^{Me}\), Mes\(_{2}\)Im 2) and their behavior towards alkynes is reported. The reaction of a mixture of [Ni\(_{2}\)(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{4}\)(μ-(η\(^{2}\) : η\(^{2}\))-COD)] B/ [Ni(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{2}\)(η\(^{4}\)-COD)] B' or [Ni(Mes\(_{2}\)Im)\(_{2}\)] 2, respectively, with alkynes afforded complexes [Ni(NHC)\(_{2}\)(η\(^{2}\)-alkyne)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\): alkyne=MeC≡CMe 3, H\(_{7}\)C\(_{3}\)C≡CC\(_{3}\)H\(_{7}\) 4, PhC≡CPh 5, MeOOCC≡CCOOMe 6, Me\(_{3}\)SiC≡CSiMe\(_{3}\) 7, PhC≡CMe 8, HC≡CC\(_{3}\)H\(_{7}\) 9, HC≡CPh 10, HC≡C(p-Tol) 11, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 12, HC≡CCOOMe 13; NHC=Mes\(_{2}\)Im: alkyne=MeC≡CMe 14, MeOOCC≡CCOOMe 15, PhC≡CMe 16, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 17, HC≡CCOOMe 18). Unusual rearrangement products 11 a and 12 a were identified for the complexes of the terminal alkynes HC≡C(p-Tol) and HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)), 11 and 12, which were formed by addition of a C-H bond of one of the NHC N-\(^{i}\)Pr methyl groups to the C≡C triple bond of the coordinated alkyne. Complex 2 catalyzes the cyclotrimerization of 2-butyne, 4-octyne, diphenylacetylene, dimethyl acetylendicarboxylate, 1-pentyne, phenylacetylene and methyl propiolate at ambient conditions, whereas 1\(^{Me}\) is not a good catalyst. The reaction of 2 with 2-butyne was monitored in some detail, which led to a mechanistic proposal for the cyclotrimerization at [Ni(NHC)\(_{2}\)]. DFT calculations reveal that the differences between 1\(^{Me}\) and 2 for alkyne cyclotrimerization lie in the energy profile of the initiation steps, which is very shallow for 2, and each step is associated with only a moderate energy change. The higher stability of 3 compared to 14 is attributed to a better electron transfer from the NHC to the metal to the alkyne ligand for the N-alkyl substituted NHC, to enhanced Ni-alkyne backbonding due to a smaller C\(_{NHC}\)-Ni-C\(_{NHC}\) bite angle, and to less steric repulsion of the smaller NHC \(^{i}\)Pr\(_{2}\)Im\(^{Me}\).}, language = {en} } @phdthesis{Krahfuss2020, author = {Krahfuß, Mirjam Julia}, title = {N-Heterocyclic Silylenes as ambiphilic Reagents in Main Group Chemistry and as Ligands in Transition Metal Chemistry}, doi = {10.25972/OPUS-21724}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217246}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2020}, abstract = {This thesis reports on the applications of a particular N-heterocyclic silylene, Dipp2NHSi (1), as an ambiphilic reagent in main group chemistry and as a ligand in transition metal chemistry. One focus of the work lies in the evaluation of the differences in the reactivity of N-heterocyclic silylenes in main group element and transition metal chemistry in comparison with the in these areas nowadays ubiquitous N-heterocyclic carbenes. The first chapter gives an insight into the reactivity of Dipp2NHSi with respect to different types of main group element compounds. Silylene 1 was reacted with group 13 compounds. Adduct formation was observed with AlI3, Al(C6F5)3 and B(C6F5)3 which led to isolation of Dipp2NHSi·AlI3 (2), Dipp2NHSi·Al(C6F5)3 (3) and Dipp2NHSi·B(C6F5)3 (4). Furthermore, the reactivity of Dipp2NHSi (1) with respect to different elementhalide bonds was investigated. The reaction with elemental bromine and iodine leads to the dihalosilanes Dipp2NHSiBr2 (5) and Dipp2NHSiI2 (6). Utilizing methyl iodide, benzyl chloride and benzyl bromide, the insertion products Dipp2NHSi(I)(Me) (10), Dipp2NHSi(Cl)(benzyl) (11) and Dipp2NHSi(Br)(benzyl) (12) are obtained. Thus, insertion is preferred to reductive coupling with formation of RH2C-CH2R (R = H, Ph) and the corresponding dihalosilane. The reaction of 1 with Me3SnCl leads to the diazabutene {(Me3Sn)N(Dipp)CH}2 (9). The reaction of 1 with Ph2SnCl2 gives exclusively Dipp2NHSiCl2 (8) and cyclic polystannanes (Ph2Sn)n. The reactivity of 1 towards selected 1,3-dipolar compounds was also examined and Dipp2NHSi was reacted with azides of different size. The reaction with adamantyl azide led to the formation of the tetrazoline 13. For the reaction with the sterically less demanding trimethylsilyl azide the azido silane Dipp2NHSi(N(SiMe3)2)(N3) (14) and the degradation product 14* was isolated. The cyclosilamine 15 was formed from the reaction of 1 with 2,6-(diphenyl)phenyl azide. The bonding situation and ligation properties of Dipp2NHSi in transition metal complexes was assessed in the second part of the thesis by means of theoretical calculations and experimental investigations. Calculations on the main electronic features of Me2Im/Me2NHSi and Dipp2NHSi/Dipp2Im revealed significant differences in the frontier orbital region of these compounds, which affect the ligation properties of NHSis in general. It was demonstrated that NHSis show significantly different behaviour concerning their coordination chemistry. In particular, one energetically low lying π-acceptor orbital seems to determine the coordination chemistry of these ligands. To provide experimental support for these calculations, the silylene complexes [M(CO)5(Dipp2NHSi)] (M = Cr 16, Mo 17, W 18) were synthesized from Dipp2NHSi and [M(CO)6] (M = Cr, Mo, W) and the tungsten NHSi complex 18 was compared to the NHC complexes [W(CO)5(iPr2Im)] (19), [W(CO)5(iPr2ImMe)] (20) and [W(CO)5(Me2ImMe)] (21). The bonding of Me2Im and Me2NHSi (= L) to transition metal complexes has been assessed with DFT calculations for the model systems [Ni(L)], [Ni(CO)3(L)], and [W(CO)5(L)]. These studies revealed some common features in the difference between M-NHSi and M-NHC bonding which largely affect the bonding situation in transition metal complexes. NHSis show a propensity for bridging two metal atoms which was demonstrated on three different examples. Dipp2NHSi reacts with [Ni(CO)4] to form the dinuclear silylene-bridged complex [{Ni(CO)2(μ-Dipp2NHSi)}2] (22) upon CO elimination. The reduction of [Ni(η5-C5H5)2] with lithium naphthalenide in the presence of Dipp2NHSi yielded the NHSi-bridged Ni(I) dimer [{(η5 C5H5)Ni(µ-Dipp2NHSi)}2] (23). The dimeric half-sandwich complex [{(η5-C5H5)Fe(CO)2}2] led upon reaction with Dipp2NHSi to the formation of the dinuclear, NHSi-bridged complex [{(η5-C5H5)Fe(CO)}2(µ-CO)(µ-Dipp2NHSi)] (24). The insertion of Dipp2NHSi into metal halide bonds was investigated in a series of manganese complexes [Mn(CO)5(X)] (X = Cl, Br, I). The reaction of Dipp2NHSi with [Mn(CO)5(I)] led to substitution of two carbonyl ligands with Dipp2NHSi (1) to afford the tricarbonyl complex [Mn(CO)3(Dipp2NHSi)2(I)] (25). In 25, the iodide ligand is aligned in the {Mn(CO)3} plane, located between both NHSi silicon atoms. Treatment of [Mn(CO)5(Br)] with two equivalents of Dipp2NHSi afforded the complex [Mn(CO)3(Dipp2NHSi)2(Br)] (26), in which the bromide ligand is distorted towards one of the NHSi ligands. The reaction of the silylene ligand with [Mn(CO)5(Cl)] at room temperature afforded a mixture of two products, [Mn(CO)3(Dipp2NHSi)2(Cl)] (27*) and the insertion product [Mn(CO)4(Dipp2NHSi)(Dipp2NHSi-Cl)] (27). Complete transfer of a halide to the silylene was achieved for the reaction of Dipp2NHSi with [(η5-C5H5)Ni(PPh3)(Cl)] to yield [Ni(PPh3)(η5-C5H5)(Dipp2NHSi-Cl)] (28). Similarly, the reaction with [(η5-C5H5)Fe(CO)2(I)] led to the formation of [(η5 C5H5)Fe(CO)2(Dipp2NHSi-I)] (29).}, subject = {Silandiylverbindungen}, language = {en} } @article{PhilippKrahfussRadackietal.2021, author = {Philipp, Michael S. M. and Krahfuss, Mirjam J. and Radacki, Krzysztof and Radius, Udo}, title = {N-Heterocyclic Carbene and Cyclic (Alkyl)(amino)carbene Adducts of Antimony(III)}, series = {European Journal of Inorganic Chemistry}, volume = {2021}, journal = {European Journal of Inorganic Chemistry}, number = {38}, doi = {10.1002/ejic.202100632}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257408}, pages = {4007-4019}, year = {2021}, abstract = {A systematic study on Lewis-acid/base adducts of N-heterocyclic carbenes (NHCs) and the cyclic (alkyl)(amino)carbene cAAC\(^{Me}\) (1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene) with antimony(III) chlorides of the general formula SbCl\(_{2}\)R (R=Cl, Ph, Mes) is presented. The reaction of the NHCs Me\(_{2}\)Im\(^{Me}\) (1,3,4,5-tetra-methyl-imidazolin-2-ylidene), iPr\(_{2}\)Im\(^{Me}\) (1,3-di-isopropyl-4,5-dimethyl-imidazolin-2-ylidene), Mes\(_{2}\)Im, Dipp\(_{2}\)Im (R\(_{2}\)Im=1,3-di-organyl-imidazolin-2-ylidene; Mes=2,4,6-trimethylphenyl, Dipp=2,6-di-isopropylphenyl) and cAAC\(^{Me}\) with antimony(III) compounds SbCl\(_{2}\)R (R=Cl (1), Ph (2) and Mes (3)) yields the adducts NHC ⋅ SbCl\(_{2}\)R (R=Cl (4), Ph (5) and Mes (6); NHC=Me\(_{2}\)Im\(^{Me}\) (a), iPr\(_{2}\)Im\(^{Me}\) (b), Dipp\(_{2}\)Im (c) and Mes\(_{2}\)Im (d)) and cAAC\(^{Me}\) ⋅ SbCl\(_{2}\)R (R=Cl (4 e) and Ph (5 e)). Thermal treatment of (Dipp\(_{2}\)Im) ⋅ SbCl\(_{2}\)Ar (Ar=Ph (5 c) and Mes (6 c)) in benzene leads to isomerization to the backbone coordinated \(^{a}\)NHC-adduct \(^{a}\)Dipp\(_{2}\)Im ⋅ SbCl\(_{2}\)Ar (Ar=Mes (7) and Ph (8)) (\(^{"a"}\) denotes "abnormal" coordination mode of the NHC) in high yields. One of the chloride substituents at antimony of 7 can be abstracted by GaCl3 or Ag[BF\(_{4}\)] to obtain the imidazolium salts [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][BF\(_{4}\)] (9) and [\(^{a}\)Dipp\(_{2}\)Im ⋅ SbClMes][GaCl\(_{4}\)] (10).}, language = {en} } @article{LorkowskiKrahfussKubickietal.2019, author = {Lorkowski, Jan and Krahfuss, Mirjam and Kubicki, Maciej and Radius, Udo and Pietraszuk, Cezary}, title = {Intramolecular ring expansion reaction (RER) and intermolecular coordination of in situ generated Cyclic (Amino)(Aryl)Carbenes (cAArCs)}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {48}, doi = {10.1002/chem.201902630}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204847}, pages = {11365-11374}, year = {2019}, abstract = {Cyclic (amino)(aryl)carbenes (cAArCs) based on the isoindoline core were successfully generated in situ by α-elimination of 3-alkoxyisoindolines at high temperatures or by deprotonation of isoindol-2-ium chlorides with sodium or copper(I) acetates at low temperatures. 3-Alkoxy-isoindolines 2 a ,b-OR (R=Me, Et, i Pr) have been prepared in high yields by the addition of a solution of 2-aryl-1,1-diphenylisoindol-2-ium triflate (1 a ,b-OTf ; a : aryl=Dipp=2,6-diisopropylphenyl; b : Mesityl-, Mes=2,4,6-trimethylphenyl) to the corresponding alcohol (ROH) with NEt3 at room temperature. Furthermore, the reaction of 2 a ,b-OMe in diethyl ether with a tenfold excess of hydrochloric acid led to the isolation of the isoindol-2-ium chlorides 1 a ,b-Cl in high yields. The thermally generated cAArC reacts with sulfur to form the thioamide 3 a . Without any additional trapping reagent, in situ generation of 1,1-diphenylisoidolin-3-ylidenes does not lead to the isolation of these compounds, but to the reaction products of the insertion of the carbene carbon atom into an ortho C-H bond of a phenyl substituent, followed by ring-expansion reaction; namely, anthracene derivatives 9-N(H)aryl-10-Ph-C14H8 4 a ,b (a : Dipp; b : Mes). These compounds are conveniently synthesized by deprotonation of the isoindol-2-ium chlorides with sodium acetate in high yields. Deprotonation of 1 a-Cl with copper(I) acetate at low temperatures afforded a mixture of 4 a and the corresponding cAArC copper(I) chloride 5 a , and allowed the isolation and structural characterization of the first example of a cAArC copper complex of general formula [(cAArC)CuCl].}, language = {en} } @article{TenderaSchaubKrahfussetal.2020, author = {Tendera, Lukas and Schaub, Thomas and Krahfuss, Mirjam J. and Kuntze-Fechner, Maximilian W. and Radius, Udo}, title = {Large vs. Small NHC Ligands in Nickel(0) Complexes: The Coordination of Olefins, Ketones and Aldehydes at [Ni(NHC)\(_{2}\)]}, series = {European Journal of Inorganic Chemistry}, volume = {2020}, journal = {European Journal of Inorganic Chemistry}, number = {33}, doi = {10.1002/ejic.202000493}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216058}, pages = {3194 -- 3207}, year = {2020}, abstract = {Investigations concerning the reactivity of Ni(0) complexes [Ni(NHC)\(_{2}\)] of NHCs (N-heterocyclic carbene) of different steric demand, Mes\(_{2}\)Im (= 1,3-dimesitylimidazoline-2-ylidene) and iPr\(_{2}\)Im (= 1,3-diisopropyl-imidazoline-2-ylidene), with olefins, ketones and aldehydes are reported. The reaction of [Ni(Mes\(_{2}\)Im)\(_{2}\)] 1 with ethylene or methyl acrylate afforded the complexes [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-C\(_{2}\)H\(_{4}\))] 3 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-(C,C)-H\(_{2}\)C=CHCOOMe)] 4, as it was previously reported for [Ni\(_{2}\)(iPr\(_{2}\)Im)\(_{4}\)(µ-(η\(^{2}\):η\(^{2}\))-COD)] 2 as a source for [Ni(iPr\(_{2}\)Im)\(_{2}\)]. In contrast to 2, complex 1 does not react with sterically more demanding olefins such as tetramethylethylene, 1,1-diphenylethylene and cyclohexene. The reaction of [Ni(NHC)\(_{2}\)] with more π-acidic ketones or aldehydes led to formation of complexes with side-on η\(^{2}\)-(C,O)-coordinating ligands: [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH\(^{t}\)Bu)] 5, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 6, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CMePh)] 7, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 8, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 9, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(OMe)(CF\(_{3}\)))] 10 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 11, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(CH(CH\(_{3}\))\(_{2}\)))] 12, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-NMe\(_{2}\)-C\(_{6}\)H\(_{4}\)))] 13, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-OMe-C\(_{6}\)H\(_{4}\)))] 14, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 15 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 16. The reaction of 1 and 2 with these simple aldehydes and ketones does not lead to a significantly different outcome, but NHC ligand rotation is hindered for the Mes\(_{2}\)Im complexes 3, 4 and 11-16 according to NMR spectroscopy. The solid-state structures of 3, 4, 11 and 12 reveal significantly larger C\(_{NHC}\)-Ni-C\(_{NHC}\) angles in the Mes\(_{2}\)Im complexes compared to the iPr\(_{2}\)Im complexes. As electron transfer in d\(^{8}\)- (or d\(^{10}\)-) ML\(_{2}\) complexes to π-acidic ligands depends on the L-M-L bite angle, the different NHCs lead thus to a different degree of electron transfer and activation of the olefin, aldehyde or ketone ligand, i.e., [Ni(iPr\(_{2}\)Im)\(_{2}\)] is the better donor to these π-acidic ligands. Furthermore, we identified two different side products from the reaction of 1 with benzaldehyde, trans-[Ni(Mes\(_{2}\)Im)\(_{2}\)H(OOCPh)] 17 and [Ni\(_{2}\)(Mes\(_{2}\)Im)\(_{2}\)(µ\(_{2}\)-CO)(µ\(_{2}\)-η\(^{2}\)-C,O-PhCOCOPh)] 18, which indicate that radical intermediates and electron transfer processes might be of importance in the reaction of 1 with aldehydes and ketones.}, language = {en} } @article{KrahfussRadius2021, author = {Krahfuss, Mirjam J. and Radius, Udo}, title = {N-Heterocyclic Silylene Main Group Element Chemistry: Adduct Formation, Insertion into E-X Bonds and Cyclization of Organoazides}, series = {European Journal of Inorganic Chemistry}, volume = {2021}, journal = {European Journal of Inorganic Chemistry}, number = {6}, doi = {10.1002/ejic.202000942}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224507}, pages = {548 -- 561}, year = {2021}, abstract = {Investigations concerning the reactivity of the N-heterocyclic silylene Dipp\(_{2}\)NHSi (1, 1,3-bis(2,6-diisopropylphenyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene) towards selected alanes and boranes, elemental halides X\(_{2}\) (X=Br, I), selected halide containing substrates such as tin chlorides and halocarbons, as well as organoazides are presented. The NHSi adducts Dipp\(_{2}\)NHSi⋅AlI\(_{3}\) (2), Dipp\(_{2}\)NHSi⋅Al(C\(_{6}\)F\(_{5}\))\(_{3}\) (3), and Dipp\(_{2}\)NHSi⋅B(C\(_{6}\)F\(_{5}\))\(_{3}\) (4) were formed by the reaction of Dipp\(_{2}\)NHSi with the corresponding Lewis acids AlI\(_{3}\), Al(C\(_{6}\)F\(_{6}\))\(_{3}\) and B(C\(_{6}\)F\(_{5}\))\(_{3}\). Adducts 3 and 4 were tested with respect to their ability to activate small organic molecules, but no frustrated Lewis pair reactivity was observed. Reactions of Dipp\(_{2}\)NHSi with Br\(_{2}\), I\(_{2}\), Ph\(_{2}\)SnCl\(_{2}\) and Me\(_{3}\)SnCl led to formation of Dipp\(_{2}\)NHSiBr\(_{2}\) (5), Dipp\(_{2}\)NHSiI\(_{2}\) (6), Dipp\(_{2}\)NHSiCl\(_{2}\) (7) and {(Me\(_{3}\)Sn)N(Dipp)CH}\(_{2}\) (8), respectively. The reaction with the halocarbons methyl iodide, benzyl chloride, and benzyl bromide afforded the insertion products Dipp\(_{2}\)NHSi(I)(CH\(_{3}\)) (9), Dipp\(_{2}\)NHSi(Cl)(CH\(_{2}\)Ph) (10) and Dipp\(_{2}\)NHSi(Br)(CH\(_{2}\)Ph) (11). Reaction of Dipp\(_{2}\)NHSi with the organoazides Ad-N\(_{3}\) (Ad=adamantyl) and TMS-N\(_{3}\) (TMS=trimethylsilyl) led to the formation of 1-Dipp\(_{2}\)NHSi-2,5-bis(adamantyl)-tetrazoline (12) and bis(trimethylsilyl)amido azido silane (13), respectively. For 2,6-(diphenyl)phenyl-N\(_{3}\) C-H activation occurs and a cyclosilamine 14 was isolated.}, language = {en} } @article{FoehrenbacherZehKrahfussetal.2021, author = {F{\"o}hrenbacher, Steffen A. and Zeh, Vivien and Krahfuss, Mirjam J. and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo}, title = {Tris(pentafluoroethyl)difluorophosphorane and N-Heterocyclic Carbenes: Adduct Formation and Frustrated Lewis Pair Reactivity}, series = {European Journal of Inorganic Chemistry}, volume = {2021}, journal = {European Journal of Inorganic Chemistry}, number = {20}, doi = {10.1002/ejic.202100183}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257386}, pages = {1941-1960}, year = {2021}, abstract = {The synthesis and characterization of Lewis acid/base adducts between tris(pentafluoroethyl)difluorophosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and selected N-heterocyclic carbenes (NHCs) R\(_{2}\)Im (1,3-di-organyl-imidazolin-2-ylidene) and phosphines are reported. For NHCs with small alkyl substituents at nitrogen (R=Me, nPr, iPr) the adducts NHC ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (2 a-h) were isolated. The reaction with the sterically more demanding NHCs Dipp\(_{2}\)Im (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolin-2-ylidene) (1 i) and tBu\(_{2}\)Im (1,3-di-tert-butyl-imidazolin-2-ylidene) (1 j) afforded the aNHC adducts 3 i and 3 j (a denotes "abnormal" NHC coordination via a backbone carbon atom). The use of tBuMeIm (1-tert-butyl-3-methyl-imidazolin-2-ylidene) (1 m) led to partial decomposition of the NHC and formation of the salt [tBuMeIm-H][MeIm ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)] (4 m). The phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) forms adducts with PMe\(_{3}\) but does not react with PPh\(_{3}\) or PCy\(_{3}\). The mer-cis isomer of literature-known Me\(_{3}\)P ⋅ PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) (5 a) was structurally characterized. Mixtures of the phosphorane PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) and the sterically encumbered NHCs tBu\(_{2}\)Im, Dipp\(_{2}\)Im, and Dipp\(_{2}\)Im\(^{H2}\) (1,3-bis-(2,6-di-iso-propylphenyl)-imidazolidin-2-ylidene) (1 k) showed properties of FLPs (Frustrated Lewis Pairs) as these mixtures were able to open the ring of THF (tetrahydrofuran) to yield NHC-(CH\(_{2}\))\(_{4}\)O-PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\) 6 i-k. Furthermore, the deprotonation of the weak C-H acids CH\(_{3}\)CN, acetone, and ethyl acetate was achieved, which led to the formation of the corresponding imidazolium salts and the phosphates [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CN)]\(^{-}\) (7), [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(OC(=CH\(_{2}\))CH\(_{3}\))]\(^{-}\) (8) and [PF\(_{2}\)(C\(_{2}\)F\(_{5}\))\(_{3}\)(CH\(_{2}\)CO\(_{2}\)Et)]\(^{-}\) (9).}, language = {en} }