Darstellung und Charakterisierung neuer niedrigkoordinierter ...

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Me Me Me Si Si N Me Me Me As Cl Scheme 4. Suggested reaction mechanism of the GaCl3-assisted methyl/chlorine exchange in bis(trimethylsilyl)amino(dichloro)arsane (3), yielding cyclodisilazane (4) via release of Me2AsCl. Me 3Si–N 3 to give a tetrazarsole (m-terphenyl 6d = Ar # = 2,6-Mes 2- C 6H 3, Mes = 2,4,6-Me 3C 6H 2). 3 This at least was the idea which worked well for the analog phosphorus compound but not for 5. 2f Upon adding a solution of GaCl 3 in CH 2Cl 2 to a solution of 5 in CH 2Cl 2 the formation of an iminoarsane was not observed but again a chlorine/methyl exchange reaction occurred as displayed by 29 Si, 1 H and 13 C NMR studies. Recrystallization from toluene gave crystals suitable for an X-ray structure determination revealing again a methyl/chlorine exchange product, now with two chlorine atoms attached to the silicon and a dimethylarsane unit according to Scheme 5 (Figure 3). Ar # Me Me Me Si Me Me Me Si Me Si N Me Si N Cl As Me Scheme 5. GaCl3-assisted methyl/chlorine exchange in trimethylsilyl(m-terphenyl)amino(dichloro)arsane (5), yielding dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6). Cl GaCl 3 Obviously, when only one Me 3Si unit is present in the molecule, a double methyl/chlorine exchange at this Si center (Scheme 5) occurs while a single methyl/chlorine exchange at two different Si centers is observed when two Me 3Si groups are present (Schemes 2 and 3). The novel dichloromethylsilyl(m-terphenyl)aminodimethylarsane (6) is soluble in toluene, CH 2Cl 2 and ether and is thermally stable up to 156 °C. Aminodimethylarsane 6 is air and moisture sensitive, but under argon it is stable over a long period in both solid and common organic solvents. Interestingly, in contrast to 1 which forms a GaCl3 adduct 2, compound 6 does not form an adduct presumably due to steric reasons. Methyl/azide-exchange reactions in trimethylsilyl(mterphenyl)aminodichloroarsane. Although we noticed that GaCl 3 already reacts with 5 in a methyl/chlorine exchange reaction, we changed the synthetic approach with respect to the Cl Me GaCl 3 Cl -GaCl 3 -Me 2AsCl GaCl 3 Me Me Me Cl Si Me Me Me Si Me Me Me Me Si Si Si N Me Me Si N Me Me N Me Me Me Si N As Cl CH2Cl2 Me Si N As Me Me Me Cl (5) Cl Cl Me (6) 1/2 Ar # Me As Cl Cl As Si Cl N Me Cl Me GaCl 3 Si Me GaCl 3 Cl Me Me Me Si Me Me Me Si Si N Me Me Me Si N As Cl Cl As GaCl 3 Figure 3. ORTEP drawing of the molecular structure of 6 in the crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms omitted for clarity). order of adding the Lewis acid to determine if a formal [3+2] cyclization 2,3 is faster than the methyl/chlorine or methyl/azide exchange reaction. Hence, in a further experiment a solution of GaCl 3 in CH 2Cl 2 was added to a solution of 5 and Me 3Si–N 3 in CH 2Cl 2 at –70 °C resulting in an orange solution. After stirring at –30 °C for 30 minutes, the solution was concentrated and recrystallized at –80 °C yielding a colorless, crystaline solid (yield = 95%). A Raman experiment immediately revealed the existence of a covalent bound azide (νas = 2141 cm –1 ) and by means of Xray structure determination the formation of azidodimethylsilyl(m-terphenyl)amino(chloro)methylarsane (7) was unequivocally proven (Figure 4). 12 Scheme 6. GaCl3-assisted methyl/azide exchange in trimethylsilyl(mterphenyl)amino(dichloro)arsane (5), yielding azidomethylsilyl(mterphenyl)amino(chloro)methylarsane (7). Cl Me Me Me Cl GaCl3 Ter 1. Me3Si-N3 Ter Me Me N Si Me As Cl Cl 2. GaCl3 CH2Cl2 -40° -Me3SiCl Me N Si N3 Me Cl As Me (5) (7)
It is interesting to note that in the presence of Me 3Si–N 3 the Lewis acid GaCl 3 facilitates a methyl/azide exchange even at low temperatures (T always below –30 °C). Without GaCl3 no reaction was observed between 5 and Me 3Si–N 3. Interestingly, the novel azidodimethylsilyl(mterphenyl)amino(chloro)methylarsane (7) represents one of the rare example of structurally characterized neutral azidosilanes. 13 Compound 7 is thermally stable up to over 149 °C, is neither heat nor shock sensitive. Moreover, 7 is extremely air and moisture sensitive, but under argon it is stable over a long period in solid at ambient temperatures and in common organic solvents (e.g. toluene, CH2Cl2, ether etc.) at low temperatures (T < –40 °C). It is interesting to mention, that, when an excess of Me 3Si–N 3 was used, a Me 3Si–N 3·GaCl 3 adduct crystallizes together with 7. This adduct was first described by Kouvetakis et al. 14 Azidosilanes are frequently used for the introduction of azide groups, for the generation of silylenes and the synthesis of silyliminophosphoranes via Staudinger reaction. 12b,15,16,17,18,19,20 Figure 4. ORTEP drawing of the molecular structure of 7 in the crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms omitted for clarity). Ter AgOTf Ter Me Si N As Cl -AgCl Toluen Me Si N As Cl Me Me Cl -40° TfO Me Me (5) (8) Scheme 6. Methyl/triflate exchange in trimethylsilyl(mterphenyl)amino(dichloro)arsane (5), yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino(methyl)chloroarsane (8) (utilization of 1 eq AgOTf). Methyl/triflate-exchange reactions in trimethylsilyl(mterphenyl)aminodichloroarsane. In a second series of experiments we studied the reaction of silver triflate, AgOTf (OTf = SO 3CF 3 = trifluoromethylsulfonate = triflate), with 5, again observing interesting methyl exchange reactions, this time triggered by the action of the Lewis acid Ag + (Scheme 6 and 7). First, one eq. of AgOTf was added to a solution of 5 in CH 2Cl 2 at –30 °C under exclusion of light, resulting in the formation of N- (trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino- (methyl)chloroarsane (9) (Mp = 163 °C) in high yields (98 %) (Scheme 6, Figure 5). Usage of 2 eq. of AgOTf led to the formation of N-(trifluoromethylsulfonatodimethylsilyl)-N-(m- terphenyl)amino-trifluoromethylsulfonatomethylarsane (10) (yield = 96%, Mp = 186 °C). Both compounds (9 and 10) have been fully characterized. As expected, when one eq. AgOTf was added a methyl/triflate exchange occurs at the silicon center (Scheme 6). However, when 2 eq. of AgOTf are used, again only one methyl/triflate exchange was observed. The second eq. of AgOTf attacks the arsenic center finally forming an As–OTf bond (Scheme 7). Figure 5. ORTEP drawing of the molecular structure of 8 in the crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms omitted for clarity). Ter 2 AgOTf Ter Me Me N Si Me As Cl Cl -2 AgCl Toluen -40° Me TfO N Si Me OTf As Me (5) (9) Scheme 7. Methyl/triflate exchange in trimethylsilyl(mterphenyl)amino(dichloro)arsane (5), yielding N-(trifluoromethylsulfonatodimethylsilyl)-N-(m-terphenyl)amino-trifluoromethylsulfonatomethylarsane (9) (utilization of 2 eq AgOTf). Figure 6. ORTEP drawing of the molecular structure of 9 in the crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms omitted for clarity).
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Darstellung und Charakterisierung n
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Erklärung Ich versichere hiermit a
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Der gesamten Arbeitsgruppe möchte
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Inhaltsverzeichnis 1. Aufgabenstell
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1. Aufgabenstellung Ausgangspunkt d
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2. Allgemeiner Teil 2.1. Abkürzung
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durch eine große strukturelle Viel
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Abbildung 5. Synthese N,N-Bis(trime
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3.4 Binäre viergliedrige Phosphor(
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4. Ergebnisse und Diskussion 4.1 Ei
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Strukturmerkmale formulieren: (i) M
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synthetisiert werden, weshalb sie s
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Abbildung 14. Molekülstruktur des
Page 27 and 28: werden, allerdings liegt das Iminoc
Page 29 and 30: 4.5. Eine ungewöhnliche Reaktion:
Page 31 and 32: 4.6. Lewis-Säure-assistierte Methy
Page 33 and 34: Die durchgeführten Austauschreakti
Page 35 and 36: Um das Dimer/Monomer-Gleichgewicht
Page 37 and 38: Bei Zugabe von nur einem Äquivalen
Page 39 and 40: 5. Ausgewählte Original-Publikatio
Page 41 and 42: Mono-, Di-, and Tricoordinated Phos
Page 43 and 44: (TMS)N-P(Cl2-n)Rn (m)1, 2) together
Page 45 and 46: molecules are rather constant and r
Page 47 and 48: Figure 1. Calculated molecular stru
Page 49 and 50: Figure 6. PES for the rearrangement
Page 51 and 52: Figure 12. PES of the intrinsic TMS
Page 53 and 54: 5.2 Ein Triazadiphosphol Sebastian
Page 55 and 56: Schema 1. Synthese der GaCl 3-Adduk
Page 57 and 58: Die ausschließliche Bildung von 2
Page 59 and 60: COMMUNICATION www.rsc.org/chemcomm
Page 61 and 62: [Mes* 2 2 t Bu 2 2H] + , 56 (16.4)
Page 63 and 64: P/N-Kationen Ein kationisches cycli
Page 65 and 66: gruppe C2/c mit vier Einheiten in d
Page 67 and 68: 5.5. An Unusual Reaction: a GaCl3-A
Page 69 and 70: GaCl3-Assisted Methyl/Chlorine Exch
Page 75 and 76: 5.6. Lewis-Acid-Assisted Methyl Exc
Page 77: Obviously, in case of the arsenic c
Page 81 and 82: Table 1. Selected bond lengths (in
Page 83 and 84: (8.35). 29 Si NMR (59.6 MHz, CD 2 C
Page 85 and 86: (1) a) Huisgen, R. in 1,3-Dipolar C
Page 87 and 88: Zuschriften Arsen-Stickstoff-Verbin
Page 89 and 90: Zuschriften liumatom eine von + 1.4
Page 91 and 92: 5.8 Cationic Cyclic Arsenic(III)Azi
Page 93 and 94: exchange occurs in the cation (reac
Page 95 and 96: H. Nöth, R. Ullmann, Chem. Ber. 19
Page 97 and 98: [27] a) A. Hahma, E. Holmberg, N. H
Page 99 and 100: Publikationen 30. Mono-, Di-, and T
Page 101 and 102: Markus Kowalewski, Burkart Krumm, P
Page 103 and 104: Z. Anorg. Allg. Chem. 2008, eingere
Page 105 and 106: Tetrahedron Lett. 2008, 49, 4901 -
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Münchner Industrie-Tag, Oktober 20
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Berufstätigkeit 09/2000 - 11/2000
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Darstellung und Charakterisierung neuer niedrigkoordinierter ...

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