Otto Mundt

ACYL- AND ALKYLIDENEPHOSPHINES. XXI.1 Acylphosphines and Their Derivatives with Phosphorus Atoms of Coordination Number 3, 2, and 1

Abstract The following article summarizes our work on acylphosphines and acylphosphides as well as on alkylidene- and alkylidynephosphines, most of which were thought only thirty years ago not to exist under ordinary conditions.

Raman spectroscopic evidence for colinear arrangement in the solid state of thermochromic distibanes

Abstract The IR and Raman spectra of the compounds (CH 3 ) 2 SbSb(CH 3 ) 2 (I), [(CH 3 ) 3 Si] 2 SbSb[Si(CH 3 ) 3 ] 2 (II), [(CH 3 ) 3 Si] 2 AsAs[Si(CH 3 ) 3 ] 2 (III) and (C 6 H 5 ) 2 SbSb(C 6 H 5 ) 2 (IV) have been studied in the liquid and solid states. Given assignments for I to III are based on normal coordinate analyses, and force constants are reported. The solid state Raman spectra of I and II exhibit strong lines near 50 cm −1 , which are assigned to the longitudinal acoustic mode of an infinite linear chain of Sb atoms. Intermolecular Sb…Sb force constants, 0.125 and 0.18 N cm −1 , are determined for I and II respectively.

Element–Element-Bindungen, IV. Molekül-und Kristallstruktur des Tetramethyldiphosphans und -diarsans /Element–Element Bonds, IV. Molecular and Crystal Structure of Tetramethyldiphosphane and -diarsane

Abstract The molecular and crystal structures of the isotypic compounds tetramethyldiphosphane 1 and -diarsane 2 have been determined by single crystal X-ray diffraction (monoclinic; C2/m; Z = 2; 1/2: -155/-144 °C\a = 540.6(2)/555.8(2); b = 1131.0(6)/l 136.7(6); c -602.5(2)/612.8(2) pm;β = 97.31(3)/95.24(3)°;P-P 221.2(1)/As-As 242.9(1) pm). In accordance with the crystallographically imposed symmetry 2/m, the molecules adopt antiperiplanar conformation. Their crystal structures are closely related to those of the homologues tetramethyldistibane 3 [1] and -dibismuthane 4 [3]. As found for the latter compounds, the E -E units (E = P, As) are also aligned in linear chains, but the intermolecular E···E contacts (P···P 381/As···As 370 pm) do not allow any extended interaction between molecules, which otherwise would result in thermochromic effects.

Zur strukturellen flexibilität der “antiaromatischen” 1,4- dihydropyrazine. Kristall- und molekülstrukturen metallorganischer derivate

Abstract Molecular and crystal structures of the cyclic conjugated 8-π-electron systems 1,4-bis(trimethylgermyl)- and 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (I and II) and of 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (III) have been determined by X-ray crystallography at low temperatures. Whereas the first two species exhibit virtually planar six-membered ring conformations and very little pyramidalization at the nitrogen centers, the sterically more crowded tetramethyl derivative III has a pronounced boat conformation with a dihedral angle of about 140° between the ring halves. These structural results are in excellent agreement with theoretical calculations as well as spectroscopic data and illustrate the exceptional structural flexibility of the “antiaromatic” 1,4-dihydropyrazine system.

Untersuchungen am Chlordiphenyl- und Tribenzylstiban sowie am Tribenzyldibromstiboran – Molekülstrukturen und Isotypie

Chlordiphenylstiban (1 d) {P21/c; Z = 4; a = 1191,8(1); b = 853,4(1); c = 1112,0(1) pm; β = 93,60(1)°; –100 ± 2 °C} kristallisiert isotyp zu einer Reihe homologer Verbindungen der Zusammensetzung (H5C6)2E–X (E = As, X = Cl, Br, I; E = Sb, X = Br, I); der Strukturtyp des Tribenzylstibans (5 d) {Pbca; Z = 8; a = 832,1(2); b = 2681,3(5); c = 1600,9(3) pm; –100 ± 3 °C} ist vom Tribenzylmethanol, -silanol und -silan her bekannt. Demgegenuber weist Tribenzyldibromstiboran (6) {P21/n; Z = 4; a = 938,4(2); b = 2292,4(5); c = 1019,7(2) pm; β = 112,71(1)°; –100 ± 3 °C} keine entsprechenden Beziehungen zu bereits bekannten Strukturtypen auf. Charakteristische, gemittelte Bindungslangen und -winkel sind {1 d: Sb–Cl 240,9(1); Sb–C 214,0 pm; Cl–Sb–C 93,8; C–Sb–C 98,6(1)°; 5 d: Sb–C 217,5(3) pm; C–Sb–C 94,9(6)°; 6: Sb–Br 264,6; Sb–C 217,0(8) pm; Br–Sb–Br 179,4(1)°; C–Sb–C 120°; Br–Sb–C 84,8(2)° bis 94,7(2)°}. Beim Stiboran 6 deuten sich sehr schwache intermolekulare Antimon‥Brom-Wechselwirkungen (Sb‥Br 417 pm) an; sie wirken sich jedoch in auffallender Weise auf die Molekulkonformation aus. Element–Element Bonds. X. Studies of Chloro(diphenyl)stibane, Tribenzylstibane and Tribenzyldibromostiborane – Molecular Structures and Isotypism Chlorodiphenylstibane (1 d) {P21/c; Z = 4; a = 1191.8(1); b = 853.4(1); c = 1112.0(1) pm; β = 93.60(1)°; –100 ± 2 °C} crystallizes isotypically with a series of homologous (H5C6)2E–X compounds (E = As, X = Cl, Br, I; E = Sb, X = Br, I); the structure type of tribenzylstibane (5 d) {Pbca; Z = 8; a = 832.1(2); b = 2681.3(5) pm; c = 1600.9(3); –100 ± 3 °C} is already known from tribenzylmethanol, -silanol and -silane. Tribenzyldibromostiborane (6) {P21/n; Z = 4; a = 938.4(2); b = 2292.4(5); c = 1019.7(2) pm; β = 112.71(1)°; –100 ± 3 °C} does not show an analogous relationship to known structure types. Characteristic mean bond lengths and angles are {1 d, Sb–Cl 240.9(1), Sb–C 214.0 pm, Cl–Sb–C 93.8°, C–Sb–C 98.6(1)°; 5 d, Sb–C 217.5(3) pm, C–Sb–C 94.9(6)°; 6, Sb–Br 264.6; Sb–C 217.0(8) pm, Br–Sb–Br 179.4(1)°; C–Sb–C 120°; Br–Sb–C 84.8(2)° to 94.7(2)°}. Stiborane 6 exhibits very weak intermolecular Sb‥Br interactions of 417 pm which, however, affect the molecular conformation in a striking way.

Common Features in the Crystal Structures of the Compounds Bis(dimethylstibanyl)oxane and -sulfane, and the Minerals Valentinite and Stibnite (Grauspießglanz)

Bis(dimethylstibanyl)oxane (1) and -sulfane (2), the two simplest organoelement species with an Sb–E–Sb fragment (E = O, S), were prepared by alkaline hydrolysis of bromodimethylstibane and by oxidation of tetramethyldistibane with sulfur [18], respectively. As shown by an x-ray structure analysis of compound 1 (m. p. < –20 °C; P212121, a = 675.9(2), b = 803.1(2), c = 1666.8(4) pm at –70 ± 2 °C; Z = 4; R1 = 0.042), the molecules (O–Sb 198.8 and 209.9 pm, Sb–O–Sb 123.0°) adopt a syn-anti conformation in the solid state and are arranged in zigzag chains along [010] via weak intermolecular O‥Sb interactions (258.5 pm, Sb–O‥Sb 117.8°, O‥Sb–O 173.5°) making use, however, of only one Me2Sb moiety. Primary and secondary bond lengths and angles agree very well with corresponding values published for valentinite, the orthorhombic modification of antimony(III) oxide [3]. Bis(dimethylstibanyl)sulfane (2) (m. p. 29 to 31 °C) crystallizes in the uncommon space group P6522 (a = 927.8(3), c = 1940.9(7) pm at –100 ± 2 °C; Z = 6; R1 = 0.021). Owing to coordination numbers of (1 + 1) and (2 + 2) for both Me2Sb groups and the sulfur atom, respectively, molecules with an approximate syn-syn conformation (S–Sb 249.8 pm, Sb–S–Sb 92.35°) build up a three-dimensional net of double helices which are linked together by Sb‥S contacts (316.4 pm). These parameters shed more light onto the rather complicated structure and bonding situation in stibnite (antimony(III) sulfide [4]). The molecular packing of compound 2 is compared with the structures of relevant inorganic solids, especially with that of β-quartz [37]. Gemeinsamkeiten in den Kristallstrukturen der Verbindungen Bis(dimethylstibanyl)oxan und -sulfan und den Mineralien Valentinit und Stibnit (Grauspiesglanz) Bis(dimethylstibanyl)oxan (1) und -sulfan (2), die beiden einfachsten elementorganischen Vertreter mit einer Sb–E–Sb-Einheit (E = O, S) wurden durch alkalische Hydrolyse von Bromdimethylstiban bzw. durch Oxidation von Tetramethyldistiban mit Schwefel [18] dargestellt. Nach den Ergebnissen einer Rontgenstrukturanalyse an Verbindung 1 (Schmp. < –20 °C; P212121, a = 675,9(2), b = 803,1(2), c = 1666,8(4) pm bei –70 ± 2 °C; Z = 4; R1 = 0,042) nehmen die Molekule (O–Sb 198,8 und 209,9 pm; Sb–O–Sb 123.0°) im Festkorper die syn-anti Konformation ein und ordnen sich unter Beteiligung nur einer der beiden Me2Sb-Gruppen uber kurze intermolekulare O‥Sb Kontakte (258,5 pm; Sb–O‥Sb 117,8°; O‥Sb–O 173,5°) zu Zickzack-Ketten langs [010] an. Ahnliche Bindungslangen, -winkel und Kontakte treten in der bekannten Kristallstruktur des Minerals Valentinit, der orthorhombischen Modifikation des Antimon(III)-oxids [3], auf. Bis(dimethylstibanyl)sulfan (2) (Schmp. 29 bis 31 °C) kristallisiert in der verhaltnismasig seltenen Raumgruppe P6522 (a = 927,8(3), c = 1940,9(7) pm bei –100 ± 2 °C; Z = 6; R1 = 0,021). Mit Koordinationszahlen von (1 + 1) fur nun alle Me2Sb-Gruppen bzw. (2 + 2) fur die Schwefelatome bauen die annahernd syn-syn konformierten Molekule (S–Sb 249,8 pm; Sb–S–Sb 92,35°) uber Sb‥S Kontakte (316,4 pm) eine dreidimensional verknupfte Anordnung von Doppelhelices auf. Mit den an Verbindung 2 bestimmten Werten lassen sich entsprechende Parameter aus der verhaltnismasig komplizierten und bindungstheoretisch schwer verstandlichen Struktur des Minerals Stibnit (Grauspiesglanz, Sb2S3 [4]) gut einordnen. Die Packung der Bis(dimethylstibanyl)sulfan-Molekule wird mit einigen im Aufbau ahnlichen anorganischen Festkorpern, insbesondere aber mit β-Quarz [37] verglichen.

Element—Element-Bindungen, III [1]. Intermolekulare Sb···Sb-Wechselwirkungen im kristallinen Tetramethyldistiban1 / Element—Element Bonds, III [1]. Intermolecular Sb···Sb Interactions in Crystalline Tetramethyldistibane

Tetramethyldistibane which shows a colour change from deep red to pale yellow upon melting, has been subjected to single-crystal x-ray diffraction analyses at -21° and -139 °C (orthorhombic,Pnma, Z = 4, -139 °C: a = 1150.9(3); b = 1136.8(2) ; c = 651.6(2) pm). The molecules adoptthe antiperiplanar conformation with the crystallographically imposed symmetry m (Cs) and arealigned in extended linear antimony chains with short intermolecular contacts (-139 °C: Sb-Sb283.8(1), Sb···Sb 367.8(1) pm; Sb-Sb---Sb 179.2°). The structure is compared with those ofsimilar compounds.

Coupled electron pair calculations for R - C = E molecules (E = N, P, As or Sb)

Abstract The effect of substituents R (R = H, H 3 C, F or H 5 Ce) on CE groups in alkylidyne compounds R - C  E (E = N, P, As or Sb) has been studied at the level of valence electron CEPA (coupled electron pair approximation) calculations. Although the reactivities of R-CE compounds differ widely (depending on E), the isolated molecules all have surprisingly similar electronic structures. For the H, H 3 C and F species, our calculated bond lengths r e (R-C) and r e ,(CE) agree well with experimental values where such are known. Along with the force constants, some trends for the changes in bond strength emerge. A plausible dependence of the dipole moments on E is observed. For benzonitrile (H 5 C 6 -CN), published experimental values of the C-C(N) bond length differ. The problem is explored using several basis sets and methods to obtain a value of 1.436(10) A. The C-C(P) bond length in benzylidynephosphane (H 5 C 6 -CP) is calculated to be 1.435(10) A. Possible uncertainties of some of the experimental values are discussed.

Bis[1,2-bis(dimethylamino)ethan-N,N']lithium-disilylphosphanid : Synthese und Struktur (Metallderivate von Molekülverbindungen ; 7)

Untersuchungen an kristallinen Lithiumphosphaniden ergeben in Abhangigkeit von den Liganden am Lithium- und den Substituenten am Phosphoratom eine uberraschend grose Strukturviefalt. Das aus Silylphosphan durch zweifache Lithinierung mit Lithium-dimethylphosphanid, nachfolgende einfache Silylierung mit Silyl-trifluormethansulfonat und anschliesende Komplexierung gut zugangliche Bis[1,2-bis(dimethylamino)ethan-N,N]lithium-disilylphosphanid (1) gehort zur bislang kleinen Gruppe der im Festkorper ionisch vorliegenden Verbindungen. Nach einer Rontgenstruktur-analyse (wR = 0,038) an den aus Diethylether isolierten Kristallen {monoklin; Raumgruppe P21/c; a = 897,8(1); b = 1 673,6(2); c = 1 466,8(1) pm;β = 90,73(1)° bei -100 ± 3°C; Z = 4 Formeleinheiten} ist Lithium verzerrt tetraedrisch von vier Stickstoffatomen aus zwei 1,2-Bis(dimethyl-amino)ethan-Molekulen umgeben. Das Disilylphosphanid-Anion weist einen gegenuber dem Standard von 225 auf 217 pm verkurzten mittleren P-Si-Abstand und einen Si-P-Si-Winkel von 92,3° auf. Crystalline lithium phosphanides studied so far show a remarkably high diversity of structure types dependent on the ligands at lithium and the substituents at phosphorus. Bis[1,2-bis(dimethylamino)ethane-N,N]lithium disilylphosphanide (1) discussed here, belongs to the up to now small group of compounds which are ionic in the solid state. It is best prepared from silylphosphane by twofold lithiation with lithium dimethylphosphanide first and subsequent monosilylation with silyl trifluoromethanesulfonate, followed by complexation. As found by X-ray structure determination (wR = 0.038) on crystals obtained from diethyl ether {monoclinic; space group P21/c; a = 897.8(1); b = 1 673.6(2); c = 1 466.8(1) pm; β= 90.73(1)° at -100 ± 3°C; Z = 4 formula units}, the lithium cation is tetrahedrally coordinated by four nitrogen atoms of two 1,2-bis(dimethylamino)ethane molecules. Characteristic parameters of the disilylphosphanide anion are a shortened average P-Si bond length of 217 pm (standard value 225 pm) and a Si-P-Si angle of 92.3°.

Homo- und heteronukleare Bindungen bei schweren Elementen der 15. und 16. Gruppe

Binuclear molecules R 2 E-ER 2 or R-Y-Y-R, formed by the heavier pnicogen (E) or chalkogen atoms (Y), respectively, tend to align in homonuclear linear chains in the solid state, if steric requirements introduced by the substituents R do not prevent this association. Going from the third period elements phosphorus or sulfur to their higher homologues, the longer intermolecular distances within these chains gradually change in nature from normal van der Waals contacts to secondary bonds. For distibanes and dibismuthanes the differing bonding situations between the solid and liquid states are reflected in a bathochromic colour shift upon crystallization. Mononuclear halogenostibanes and -bismuthanes with aromatic groups are subject to intermolecular association, too, if there are enough electronegative substituents to invoke a sufficient Lewis acidity at the pnicogen atom. Non-classical pnicogen-arene interactions are found together with asymmetrie halogeno bridges for aryl-substituted stibanes. Only one of the corresponding bismuthanes has been investigated up to now; it shows symmetrie halogeno bridges, but no bismuth-arene coordination.