Joseph Grobe

Alternativ-Liganden, XXXVII. Phosphanliganden mit Bor als Lewis-acidem Zentrum: Synthese und Koordinationseigenschaften / Alternative Ligands, XXXVII. Phosphane Ligands with Boron as Lewis-acidic Centre: Synthesis and Coordinating Properties

The complex [Rh(CO)Cl{Me2PC(Me)=C(Me)BMe2}2] (5) has been prepared again in order to prove its structure with weak bonding interactions between the basic rhodium centre and the Lewisacidic Me2B group of the donor/acceptor ligand Me2PC(Me)=C(Me)BMe2 (1). For further investigations additional ligands with P-donor and B-acceptor centres, e. g. Ph2PC(Ph)=C(Ph)BPh2 (2), B(OCH2PMe2)3 (3), and B(CH2CH2PMe2)3 (4), have been prepared and the coordinating properties have been studied by reactions of 1 and 4 with [(π-C5Me5)Rh(CO)2] and Pd(PPh3)4, respectively. Because single crystals of the products [(π-C5Me5)Rh(CO)Me2PC(Me)=C(Me)BMe2] (6), [(π-C5Me5)Rh(CO){Me2PC(Me)=C(Me)BMe2}2] (7) as well as [Pd{B(CH2CH2PMe2)3}] (8) or [(Ph3P)Pd{B(CH2CH2PMe2)3}] (9) could not be generated, quantum chemical calculations have been used to elucidate the coordination geometry expected for 5, 8 and 9. The calculations support the structure of 5 within the expected limitations of the experimental and theoretical methods and - in spite of the extremely soft coordination sphere of 8 and 9 - are in accord with spectroscopic results for the cage structures.

SYNTHESIS, STRUCTURE AND ISOMERIZATION OF FLUORINE-CONTAINING 1,2-DIHYDRO-1,3-DIPHOSPHETES

Abstract Reaction of perfluoro-2-phosphapropene 1 with phosphaalkynes of the type RC P (2) smoothly yields the formal [2 + 2] cycloaddition products, 1,2-dihydro-1,3-diphosphetes RC=P − − CF 2 − − P ¯ CF 3 (R = Me2N (3a), Et2N (3b), iPr2N (3c), tBu (3d)). Instead of the not isolable aminophosphaalkynes Me2NC P and Et2NC P, the precursors HP C(F)NR2 are successfully used as synthetic equivalents. The results of a single-crystal X-ray analysis of 3a almost exactly agree with the structural data of an ab initio calculation. The elongated sp2 CP distance in 3a (exp. 173.7(2) pm, calc. 171.4 pm) is due to the interaction of the Me2N lone pair with the PC (p p)π bond. Surprisingly, the sterically unshielded derivatives 3a and 3b at 25°C undergo an interesting rearrangement to the thermodynamically more stable 1,2-dihydro-1,2-diphosphetes RC=C(F) − − P(CF 3 ) − − P ¯ F (R = Me2N (6a, Et2N(6b)) via a 1,2-fluorine shift, an electrocyclic ring opening to a 1,4-diphosphabutadiene intermediate and an intramolecular [2 + 2] cycloaddition. This mechanism is supported by high level ab initio calculations.

Reaktive EC(pp)π-systeme XXII. Trifluormethylselenocarbonylfluorid: Darstellung und reaktionen mit 1,3-dienen sowie sekundären aminen

Abstract The red-violet trifluoromethylselenocarbonylfluoride SeC(F)CF 3 ( 1 ) is produced quantitatively by thermal 1,2-elimination of Me 3 SnF from trimethylstannylpentafluoroethylselane Me 3 SnSeC 2 F 5 ( 2 ) at 300°C and 10 −2 torr. 1 is less inert than the related selenocarbonyldifluoride SeCF 2 and shows a strong dienophilicity. The reactions of 1 with 2,3-dimethyl-1,3-butadiene, isoprene, cyclopentadiene, pentamethylcyclopentadiene and 1,3-cyclohexadiene, respectively, afford the corresponding Diels-Alder adducts 3–7 in high yields (70–98%). Compound 1 reacts with secondary amines, such as dimethyl-, diethyl- or di-isopropylamine and pyrrolidine to give trifluoromethyl selenocarbonylamides F 3 CC(Se)NR 2 ( 8–11 ). All the new compounds of this study ( 2–11 ) have been characterized by elemental analysis (C, H, N) and spectroscopic investigations (MS, IR, NMR).

Reactions of Polyfluoroarenes with MenE‐MMe3 Reagents (MenE = Me2As, Me2P, Me2N, and MeS; M = Si, Sn): Synthesis of Polyfluoroaryl MenE Compounds

Trimethylsilyldimethylarsane Me3SiAsMe2 was used as a reagent for the substitution of fluorine in polyfluoroarenes C6F5X (X = F, H, Cl) and C5NF5 by the Me2As group. The reactions occur between 50 — 180 °C, either in benzene or without solvent, to give as a rule 4-X-1-(dimethylarsano)tetrafluorobenzenes XC6F4AsMe2, (1—3) and 4-dimethylarsano-tetrafluoropyridine C5NF4AsMe2 (4), respectively, in yields between 43 and 94 %. In the case of C6F6, also double substitution is observed affording 1, 4-bis(dimethylarsano)tetrafluorobenzene 5 in addition to the monosubstituted derivative. The time and temperature dependencies of the reactions increase in the sequence: C6F6< C6F5H < C6F5Cl < C5NF5. The arsanes 1 and 4 were transformed to the potentially valuable bidentate ligands 1-(dimethylarsano)-4-(dimethylphosphano)tetrafluorobenzene 6 and 4-(dimethylarsano)-2-(dimethylphosphano)trifluoropyridine 8 by reaction with trimethylsilyl-dimethylphosphane Me3SiPMe2. 6reacts with oxygen to yield the corresponding phosphane oxide 7. Trimethylsilyl-dimethylamine Me3SiNMe2 also was successfully tested as a reagent for the dimethylamination of polyfluoroarenes C6F5X [X = F, H, Cl, CF3, P(S)Me2], 1-P(S)Me2-4-H-C6F4 and 4-X-C5NF4 [X = F, PMe2, P(S)Me2]. Sulfuration of the new Me2P derivatives 8 and 20 leads to the corresponding thiophosphanes 9 and 21 (Schemes 2 and 3). Furthermore, the recently reported very efficient one-pot synthesis of Me2P substituted polyfluoroarenes (e.g. XC6F4PMe2 with X = F, Me2PC6F4) was extended to the preparation of Me2As and MeS derivatives of pentafluoropyridine using a mixture of Me3SnH, As2Me4 (or S2Me2) and C5NF5 as precursors for the one-pot reaction. The expected products 4-(dimethylarsano)tetrafluoropyridine 4 and 4-(methylthio)tetrafluoropyridine 22, respectively, were obtained in 84 and 82 % isolated yields. The novel compounds were characterized by spectroscopic (NMR, MS) and analytical data. Compounds 5, 7, 9 and 21 could be isolated in form of single crystals and their structures have been studied by X-ray diffraction. Reaktionen von Polyfluorarenen mit MenE—MMe3-Reagenzien (MenE = Me2As, Me2P, Me2N, MeS; M = Si, Sn): Synthese von MenE-substituierten Polyfluorarenen Trimethylsilyl-dimethylarsan Me3SiAsMe2 wurde bei Polyfluorarenen C6F5X (X = F, H, Cl) und Perfluorpyridin C5NF5 als Reagenz fur die Substitution von Fluor durch die Me2As-Gruppe eingesetzt. Die Reaktionen wurden in Benzol oder ohne Losungsmittel bei Temperaturen zwischen 50 und 180 °C durchgefuhrt und liefern in der Regel die 4-X-1-(Dimethylarsano)tetrafluorbenzole XC6F4AsMe2 (1 — 3) bzw. 4-Dimethylarsanotetrafluorpyridin C5NF4AsMe2 (4) in Ausbeuten von 43 — 94 %. Im Fall von C6F6 wird auch Zweifachsubstitution zum 1, 4-Bis(dimethylarsano)tetrafluorbenzol 5 beobachtet. Die Reaktivitat, gemessen am Zeitbedarf und an der Temperaturabhangigkeit der Reaktionen, wird von der Art des Polyfluorarens bestimmt und nimmt in der Reihe C6F6 < C6F5H < C6F5Cl < C5NF5 zu. Die Arsane 1 und 4 wurden mit Trimethylsilyl-dimethylphosphan Me3SiPMe2 zu den heterosubstituierten Derivaten 1-(Dimethylarsano)-4-(dimethylphosphano)tetrafluorbenzol 6 bzw. 4-(Dimethylarsano)-2-(dimethylphosphano)-trifluorpyridine 8 umgesetzt, die als potenzielle zweizahnige Liganden von Interesse sind. 6 reagiert mit Sauerstoff zum entsprechenden Phosphanoxid 7. Trimethylsilyl-dimethylamin Me3SiNMe2 wurde als Reagenz fur die Dimethylaminierung der Polyfluorarene C6F5X [X = F, H, Cl, CF3, P(S)Me2], 1-P(S)Me2-4-HC6F4 and 4-X-C5NF4 [X = F, PMe2, P(S)Me2] ebenfalls untersucht. Durch Sulfurierung der Me2P-Derivate 8 und 20 werden die Thiophosphane 9 und 21 erhalten (Schemata 2 und 3). Auserdem wurde die vor kurzem entwickelte Eintopf-Synthese fur Me2P substituierte Polyfluorarene (z. B. XC6F4PMe2 mit X = F, Me2PC6F4) auf die Darstellung von Me2As- und MeS-Derivaten des Pentafluorpyridins ausgedehnt: Als Edukte fur die Eintopf-Reaktionen wurden Me3SnH, As2Me4 (oder S2Me2) und C5NF5 verwendet. Die erwarteten Produkte 4-(Dimethylarsano)tetrafluorpyridin 4 bzw. 4-(Methylthio)tetrafluorpyridin 22 wurden in 84- bzw. 82- %iger Ausbeute isoliert. Die neuen Verbindungen wurden durch spektroskopische (NMR, MS) und analytische Daten charakterisiert. Die Vertreter 5, 7, 9 und 21 konnten in Form von Einkristallen isoliert werden; ihre Strukturen wurden durch Rontgenbeugung aufgeklart.

Reaktive EC (pp) π-Systeme: XIII. [2 + 4]-Cycloadditionen mit Selenocarbonyldifluorid als Dienophil☆

Abstract The Diels-Alder adducts 2–6 are prepared in good yields (67–98%) by [2 + 4] cycloaddition of the selenocarbonyldifluoride F2CSe (1) to a 1,3-diene e.g. isoprene, 2,3-dimethyl-1,3-butadiene, cyclopentadiene, pentamethylcyclopentadiene and 1,3-cyclohexadiene. The only by-product, (F2CSe)x, is formed by the polymerization of 1. The new compounds 2–6 are stable at room temperature; they have been characterized by elemental analysis (C, H) and by MS, NMR and IR spectroscopy.

Silaethene: XIII. Erzeugung von SiC-Doppelbindungen in der Koordinationssphäre von Eisencarbonylkomplexen

Abstract The suitability of the vinylsilyliron complexes [Cp(CO) 2 Fe]RSi(Cl)CHCH 2 [R = Me ( 1 ), Ph ( 2 ), Bu t ( 3 ), Fe(CO) 2 Cp ( 4 )] and of [Cp(CO) 2 Fe]MeSi(Cl)CMeCH 2 ( 14 ) as precursors for the generation of silaethene derivatives has been investigated. The starting compounds 1 to 4 and 14 can be obtained from Me(Vi)SiCl 2 , Ph(Vi)SiCl 2 , HSiCl 3 and MeSiCl 3 , respectively, by judicious combination of published procedures. They have been characterized by analytical and spectroscopic studies as well as by comparison with known data. The generation of the SiC intermediates was attempted by treating the vinylsilyl iron complexes wit LiBu t at low temperatures (−10°C). Only with 1 was a smooth reaction observed with formation of the Z Z dimer 1,3-bis(cyclopentadienyl-dicarbonyliron)-1,3-dimethyl-2,4-dineopentyl-1,3-disilacyclobutane ( 16 ) of the expected silaethene [Cp(CO) 2 Fe]-MeSiCHCH 2 Bu t . This intermediate also seems plausible on the basis of trapping experiments, using 2,3-dimethyl-1,3-butadiene, isoprene or 1,3-cyclohexadiene. However, since 16 is formed as the main product even in the presence of an excess of these dienes, the cyclization of the lithiated precursor ClSiMe[Fe(CO) 2 Cp]-CH(CH 2 Bu t )SiMe[Fe(CO) 2 Cp]CH(Li)CH 2 Bu t must be regarded as an alternative route to 16 . The crystal and molecular structure of 16 indicate a Z Z configuration of the bulky ring substituents. The disilacyclobutane skeleton is nonplanar with a dihedral angle of 18.7°. Similar to other 1,3-disilacyclobutane derivatives, 16 shows a fairly short transannular Si(1)⋯Si(2) distance of 2.641(1) A. Due to the −I effect of the phenyl substituent reaction of 2 with LiBu t yields oligomeric coupling products, whereas in 3 , 4 or 14 for steric reasons LiBu t clearly attacks the carbonyl ligand instead of the CC double bond to give black, pyrophoric solids of low solubility.

Reaktive EC (p-p)π-systeme: IX. Diels-alder-reaktionen des acyclischen arsaalkens F3CAsCF2☆☆☆

Abstract The Diels-Alder adducts 2–8: are prepared in a one-pot procedure by [2 + 4] cycloaddition of the perfluoro-2-arsapropene F3CAsCF2 (1) to the corresponding 1,3-dienes, producing 1 in situ by thermal (70–80°C) elimination of Me3SnF from trimethylstannylbis(trifluoromethyl)arsane. The extreme reactivity of 1 is demonstrated by its reaction with thiophene. The observed formation of the cis and trans dimers (F3CAsCF2)2 as by-products is due to partial cycloreversion of the Diels-Alder compounds.

NOVEL TETRAPHOSPHABARRELENE AND -SEMIBULLVALENE DERIVATIVES BY REACTIONS OF 2,4,6-TRI-TERT-BUTYL-1,3,5-TRIPHOSPHABENZENE WITH PHOSPHAALKYNES

2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene 4 reacts with phosphaalkynes P≡C–R [R = tBu (5a), tPen (5b)] at room temperature in a formal [4 + 2] cycloaddition to yield the corresponding 1,3,5,7-tetraphosphabarrelene derivatives 8a and 8b, respectively. The analogous reaction of 4 with the aminophosphaethyne P≡C–N(iPr)2 (9) unexpectedly leads to the 1,3,4,7-tetraphosphasemibullvalene derivative 10 as the only product. The single-crystal X-ray analysis of 10 exhibits a diphosphirane unit with a very long PP distance of 2.274(1) A together with a large extension of the PCP angle in the three-membered ring to 75.3(1)°.

Silaethene: XII. Massenspektrometrische untersuchungen an monosilacyclobutanen

Mass spectra of monosilacyclobutanes H2SiCH2CH2CH2 (1), Me(H)SiCH2CH2CH2 (2), Me2SiCH2CH2CH2 (3), (CD3)2SiCH2CH2CH2 (4), Me(Cl)SiCH2CH2CH2 (5), Cl2SiCH2CH2CH2 (6), F2SiCH2CH2CH2 (7), H2SiCH(Me)CH2CH2 (8), Me2SiCH(Me)CH2CH2 (9) and Cl2SiCH(Me)CH2CH2 (10) have been recorded using ionization potentials between 70 and 15 eV. Appearance potentials (AP) were deduced for the M+, (M+ − 28) and (M+ − 15) fragments, and the enthalpy of dissociation for the process has been calculated from a thermochemical cycle (49.6 ± 5 kcal mol− 207.4 kJ mol−1). The energy differences Δ1 = AP(M+ − 28) - AP(M+) for the elimination of C2H4 from the parent ions [R1R2SiCH2CH2CH2 increase with increasing ionization potential of the substituents R1 and R2. The elimination of CH3 from parent ions without methyl substituents is obviously a low-energy fragmentation route as indicated by the fairly low values for Δ2 = AP(M+ − 15) - AP(M+).

Alternativ-Liganden XXXVIII. [1] Neue Versuche zur Synthese von Pd(0)- und Pt(0)-Komplexen des Tripod-Phosphanliganden FSi(CH2CH2PMe2)3 / Alternative Ligands XXXVIII. [1] Further Attempts to Synthesize Pd(0) and Pt(0) Complexes with the Tripod Phosphane Ligand FSi(CH2CH2PMe2)3

The tripod phosphane ligand FSi(CH2CH2PMe2)3 (1) has been prepared again and attempts to generate F3CSi(CH2CH2PMe2)3 (2) were undertaken for the preparation of transition metal cage compounds of the type A(CCP)3M or A(CCP)3M-L (A = FSi, F3CSi). The photochemical addition of dimethylphosphane to trifluoromethyl-trivinylsilane, however, gave 1 instead of the expected CF3Sitripod ligand 2, obviously due to difluorocarbene elimination. 1 was used to prepare the chromium carbonyl derivative (CO)3Cr[(Me2PCH2CH2)3SiF] (3) from Cr(CO)3CHT, and 3 was characterized by NMR and IR spectroscopy. The novel complex FSi(CH2CH2PMe2)3Pd (4) and its PPh3 derivative [FSi(CH2CH2PMe2)3Pd]PPh3 (5) have been obtained by reacting 1 with Pd(PPh3)4 and were characterized by NMR (4) and X-ray diffraction (5). The data prove the expected Pd→Si interaction by characteristic coordination shifts and a Pd-Si distance of 3.875 Å which is smaller than the Ni-Si distance in the corresponding nickel compound (3.92 Å ). The preparation of the analogous platinum complex from the precursors Pt(PPh3)4, Pt(C7H10)3, or (Ph3P)2Pt(η2-C2H4) failed, whereas the reaction of 1 with Pt(PEt3)4 was successful, but surprisingly led to the trinuclear complex [FSi(CH2CH2PMe2)3Pt]3(PMe2CH2CH2)3SiF (6) with three cages of type 4 and an additional ligand 1 as a bridging unit. Complex 6 was isolated and characterized spectroscopically. Quantum chemical calculations have been used to elucidate the coordination geometry expected for 4, 5 and the corresponding platinum cage 4′ in 6. The calculations support the structure of 5 within the expected limitations of the experimental and theoretical methods and - in spite of the extremely soft coordination sphere of the studied cages - are in accord with the spectroscopic results.