Martin Göhner

{Ph2(Carb)P}MCl3 (M = Pd, Pt; Carb = 2,3‐dihydro‐1,3‐diisopropyl‐4,5dimethylimidazol‐2‐ylidene) – a Novel Cationic Phosphane Ligand [1]

The phosphane ligand [Ph2(Carb)P]+ forms neutral complexes {Ph2(Carb)P}MCl3 (Carb = 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; M = Pd, Pt) through the reaction of its chloride salt with (PhCN)2MCl2; the triarylphosphane type properties of the ligand are revealed by n.m.r. and structural data.

Synthese und Deprotonierung eines Phosphinomethylimidazoliumsalzes. Zur Delokalisierung der π‐Elektronen in Aminovinylphosphanen [1]

Das ylidartige Olefin 1, 3, 4, 5-Tetramethyl-2-methylenimidazolin (1, Im=CH2) reagiert mit Chlordiphenylphosphan unter Bildung des Phosphansalzes [(Im-CH2)PPh2]Cl (6); hieraus ist das Vinylphosphan Im=CHPPh2 (8) durch Deprotonierung zuganglich. 8 reagiert mit HBF4-Etherat zum Tetrafluoroborat-Salz [(Im-CH2)PPh2]BF4 (7). Die Kristallstrukturen von 7 und 8 werden ermittelt und diskutiert. Die Delokalisierung der π-Elektronen in 8 wird durch Strukturdaten und temperaturabhangige NMR-Spektroskopie angezeigt. Tetrafluorobo-Synthesis and Deprotonation of a Phosphinomethylimidazolium Salt. On the π-Electron Delocalization im Aminovinyl Phosphanes [1] The ylidic olefin 1, 3, 4, 5-tetramethyl-2-methyleneimidazoline (1, Im=CH2) reacts with chlorodiphenylphosphane to give the phosphane salt [(Im-CH2)PPh2]Cl (6) from which the vinylphosphane Im=CHPPh2 (8) is obtained by deprotonation. 8 reacts with HBF4 etherate to give the tetrafluoroborate salt [(Im-CH2)-PPh2] BF4 (7). The crystal structures of 7 and 8 are determined and discussed. In 8, π-electron delocalisation is indicated both by structural data and temperature dependent n.m.r. spectroscopy

The 1 : 1 Adduct of 1,3-Diisopropyl-4,5-dimethyl-2,3-dihydroimidazol-2- ylidene and Nitrous Oxide

The nucleophilic carbene 1,3-diisopropyl-4,5-dimethyl-2,3-dihydroimidazol-2-ylidene (7) captures nitrous oxide under formation of both syn- (8) and anti-1,3-diisopropyl-4,5-imidazolium diazotate (9). The syn-isomer is the thermodynamically more stable form. As shown by X-ray crystallography, the two isomers are statistically distributed in the crystalline state Graphical Abstract The 1 : 1 Adduct of 1,3-Diisopropyl-4,5-dimethyl-2,3-dihydroimidazol-2- ylidene and Nitrous Oxide

Der Einfluß von Phosphoryl‐Substituenten auf die Eigenschaften P‐substituierter 2‐Methylimidazolium‐Ionen und 2‐Methylenimidazoline [1]

Die Imidazoline ImCHP(E)Ph2 [6, E = S (a), Se (b)] werden durch Umsetzung von ImCHPPh2 (4) mit Schwefel bzw. Selen erhalten. Mit HBF4 sind hieraus die entsprechenden Imidazolium-Salze [ImCH2P(E)Ph2][BF4] [5, E = S (a), Se (b)] zuganglich. 1, 3, 4, 5-Tetramethyl-2-methylenimidazolin (1, ImCH2) reagiert mit Ph2P(O)Cl unter Bildung des entsprechenden Phosphansalzes [ImCH2P(O)Ph2]Cl (7), aus dem die Vinylverbindung ImCHP(O)Ph2 (8) durch Deprotonierung erhalten wird. 8 reagiert mit uberschussiger HBF4 zum Phosphanoxid-BF3-Addukt [ImCH2P(O)Ph2 · BF3][BF4] (9). Die Kristallstrukturen von 5a, 5b, 6b, 7 · CH2Cl2 und 9 · H2O sowie vorlaufige Daten von 8 werden mitgeteilt und im Vergleich mit den Phosphanen [ImCH2PPh2][BF4] (3b) und ImCHPPh2 (4) diskutiert. Aus Strukturdaten wird auf eine π-Elektronendelokalisation in 6b und 8 geschlossen. The Influence of Phosphoryl Substituents on the Properties of P-Substituted 2-Methylimidazolium Ions and 2-Methyleneimidazolines [1] The imidazolines ImCHP(E)Ph2 [6, E = S (a), Se (b)] are obtained from ImCHPPh2 (4) and sulfur or selenium. HBF4 reaction yields the corresponding imidazolium salts [ImCH2P(E)Ph2][BF4] [5, E = S (a), Se (b)]. 1, 3, 4, 5-Tetramethyl-2-methylenimidazoline (1, ImCH2) reacts with Ph2P(O)Cl to give the corresponding phosphane salt [ImCH2P(O)Ph2]Cl (7) from which the vinyl compound ImCHP(O)Ph2 (8) is formed through deprotonation. 8 reacts with excess HBF4 to give the phosphine oxide BF3 adduct [ImCH2P(O)Ph2 · BF3][BF4] (9). The crystal structures of 5a, 5b, 6b, 7 · CH2Cl2 and 9 · H2O as well as preliminary data of 8 are reported and discussed on comparison with the phosphanes [ImCH2PPh2][BF4] (3b) and ImCHPPh2 (4). From structural data, π-electron delocalisation is concluded for 6b and 8.

2,3-Dihydro-1,3,4,5-tetraisopropylimidazol-2-yliden / 2,3-Dihydro-1,3,4,5-tetraisopropylimidazol-2-ylidene

2,3-Dihydro-1,3,4,5-tetraisopropylimidazol-2-ylidene (1d) is obtained from 1,3,4,5-tetraisopropylimidazolin- 2-thion (2d) and potassium in excellent yield. On comparison with 2,3-dihydro-1,3- diethyl-4,5-dimethylimidazol-2-ylidene (1b) and 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol- 2-ylidene (1c), 2d exhibits a markedly decreased reactivity towards electrophiles which can be explained by differences in the molecular structures in the crystal. Graphical Abstract 2,3-Dihydro-1,3,4,5-tetraisopropylimidazol-2-yliden / 2,3-Dihydro-1,3,4,5-tetraisopropylimidazol-2-ylidene

Die Strukturchemie der 2-Chalkogeno-1,3,4,5-tetraisopropylimidazoline / The Structural Chemistry of the 2-Chalcogeno-1,3,4,5-tetraisopropylimidazolines

Abstract 1,3,4,5-Tetraisopropyl-2-thioimidazoline (6b) was prepared by condensation of N,N′-diisopropylthiourea and isobutyroin. 1,3,4,5-Tetraisopropyl-2-oxoimidazoline (6a), 1,3,4,5-tetraisopropyl-2- selenoimidazoline (6c) and 1,3,4,5-tetraisopropyl-2-telluroimidazoline (6d) were obtained from 2,3- dihydro-1,3,4,5-tetraisopropylimidazol-2-ylidene and dinitrogen oxide or selenium and tellurium, respectively. The crystal structure analyses revealed the presence of the A-type rotamer for 6a while for 6c a paddlewheel-like orientation of the isopropyl substituents was found (I type). In crystals of 6b, both A- and E-type molecules are present while in solution at room temperature the I-type rotamer is detected. A dynamic 1H and 13C{1H} NMR study of 6b in the range of 185.5 to 423.3K revealed a temperature-dependent rotation of the isopropyl substituents (ΔH‡ = 15:7(9) kcal mol-1, ΔS‡ = -5(3) calK-1 mol-1, ΔG‡ = 17:2(9) kcal mol-1) with I as the rotamer of lowest energy. This result is confirmed by MO calculations which indicate A and C being the next stable rotamers. The barrier of rotation of the isopropyl substituents about the C-N bond from I to C (B3LYP ΔH‡ =13:7 kcal mol-1,ΔG‡ =15:4 kcal mol-1) is slightly lower than that about the C-C bond from I to G.

Crystal structure of 1,1',3,3'-tetraisopropyl-4,4',5,5'-tetramethyl-1H,1'H- [2,2'-biimidazole]-3,3'-diium difluoride tetrahydrate, C22H48F2N4O4

Abstract C22H48F2N4O4, tetragonal, P4̅21c (no. 114), a = 10.326(2) Å, c = 12.307(3) Å, V = 1312.2 Å3, Z = 2, Rgt(F) = 0.0316, wRref(F2) = 0.0646, T = 230 K.

Über Komplexe des Typs {(PhC=C)3P}3M(CO)3 (M = Cr, Mo, W) / On Complexes of the Type {(PhC=C)3P}3M(CO)3 (M = Cr, Mo, W)

Abstract The tris(alkinyl)phosphine complexes {(PhC=C)3P}3M(CO)3, M = Cr (3a), Mo (3b), W (3c), are obtained from P(C=CPh)3 and (C6H15N3)M(CO)3 (C6H15N3 = 1,3,5-trimethyl-1,3,5-triazacyclohexane) as stable yellow solids in good yields. While IR data indicate significant acceptor properties of the phosphane ligands, the X-ray structure analysis of 3c also allows the discussion of weak donor interactions.