Molecular Structures of Sulfur Cyanide Trifluoride, SF(3)CN, and Sulfinyl Cyanide Fluoride, FS(O)CN

General valence force fields for SF(3)CN and FS(O)CN are derived from vibrational data taken from the literature and from theoretical calculations. Gas phase electron diffraction studies on both molecules yield the following geometric parameters (r(a) distances and angles with 3sigma uncertainties). SF(3)CN: r(S-F(e)) = 155.2(4) r(S-F(a)) = 165.7(3), r(S-C) = 173.6(8), r(C&tbd1;N) = 115.9(4) pm; angle(F(a)SF(e)) = 86.9(3), angle(F(a)SC) = 86.0(4) angle(F(e)SC) = 98.7(8), angle(F(a)SF(a)) = 169.0(6), angle(SCN) = 171(4) degrees. FS(O)CN: r(S-F) = 159.8(3), r(S=O) = 143.2(2), r(S-C) = 178.3(3), r(C&tbd1;N) = 115.0(3) pm; angle(FSO) = 104.9(4), angle(FSC) = 93.9(4), angle(CSO) = 105.3(5), angle(SCN) = 176(4) degrees. These experimental results are compared to ab initio values (HF/3-21G, HF/6-31G, and MP2/6-31G), and the bonding properties in these sulfur (IV) cyanides are discussed.     

Cycloaddition of single oxygen and triazolinedione (TAD) with spirocyclopentadienyl-1,3,5-cycloheptatrienes1: tropilidene versus norcaradiene reactivity

4-Methyl-1,2,4-triazoline-3,5-dione (MTAD) gives with 7-spiro-fluorenyl-1,3,5-cycloheptatriene ($\text{1d}$) initially he norcaradine-type urazole ($\text{N3d}$) which at ambient temperatures rearranges into ($\text{6d}$), while ¹0₂ gives the tropilidene-type endoperoxide ($\text{T4d}$).     

Polyhedral cobalt(II) and iron(II) siloxanes: synthesis and x-ray crystal structure of [(RSi(OH)O2)Co(OPMe3)]4 and [(RSiO3)2(RSi(OH)O2)4(mu3-OH)2Fe8(THF)4] (R = (2,6-iPr2C6H3)N(SiMe3))

The cobalt(II) and iron(II) siloxane compounds were prepared by the reaction of lipophilic N-bonded silanetriol 1 with metal silylamides M[N(SiMe3)2]2 (M = Co (2), Fe (3)) in a 1:1 and 3:4 molar ratio, respectively. A plot of 1/chi versus temperature in the range of 2-300 K indicates the paramagnetic behavior of 2 and 3. The composition and molecular structures of 2 and 3 were fully determined by IR, elemental analysis, and X-ray crystal structural analyses. Compound 2 possesses a pseudo-4-fold (S4) symmetry, whereas 3 reveals an inversion center. Compound 2 represents a tetracobalt(II) drum while 3 exhibits an octairon(II) cage containing siloxane ligands.     

Zum Formalismus der LCPO-MO-Methode

Based on the combination ofPars-Orbitals (PO) the LCPO-MO-Method has been described for the quantum chemical treatment of large molecules which are divided in reasonable fragments. The secular matrix constructed from the Eigenvalues and parameters of the molecular fragments has a characteristic block-form. The dimension of the secularproblem can be reduced and depends on the used approximations. The resulting method is demonstrated for naphthalene.

Herrn Professor Dr.O. E. Polansky zu seinem 60. Geburtstag gewidmet.     

Syntheses and molecular structures of eta3-[(eta5-Cp*)(CO)2Fe-AsPC(SiMe3)2]M(CO)2(eta5-Cp)(M = Mo, W): the first complexes featuring eta3-arsaphosphaallyl ligands

Reaction of (eta5-Cp)(CO)2M=P=C(SiMe3)2 4a (M = Mo) and 4b (M = W) with (eta5-Cp*)(CO)2Fe-As=C(NMe2)2 5 affords the eta3-1-arsa-2-phosphaallyl complexes [(eta5-Cp*)(CO)2Fe-AsPC(SiMe3)2]M(CO)2(eta5-Cp) 6a and 6b, the molecular structures of which were determined by X-ray analyses.     

C-F or C-H bond activation and C-C coupling reactions of fluorinated pyridines at rhodium: synthesis, structure and reactivity of a variety of tetrafluoropyridyl complexes

Reactions of [RhH(PEt3)3] (1) or [RhH(PEt3)4] (2) with pentafluoropyridine or 2,3,5,6-tetrafluoropyridine afford the activation product [Rh(4-C5NF4)(PEt3)3] (3). Treatment of 3 with CO, 13CO or CNtBu effects the formation of trans-[Rh(4-C5NF4)(CO)(PEt3)2] (4a), trans-[Rh(4-C5NF4)(13CO)(PEt3)2] (4b) and trans-[Rh(4-C5NF4)(CNtBu)(PEt3)2] (5). The rhodium(III) compounds trans-[RhI(CH3)(4-C5NF4)(PEt3)2] (6a) and trans-[RhI(13CH3)(4-C5NF4)(PEt3)2] (6b) are accessible on reaction of 3 with CH3I or 13CH3I. In the presence of CO or 13CO these complexes convert into trans-[RhI(CH3)(4-C5NF4)(CO)(PEt3)2] (7a), trans-[RhI(13CH3)(4-C5NF4)(CO)(PEt3)2] (7b) and trans-[RhI(13CH3)(4-C5NF4)(13CO)(PEt3)2] (7c). The trans arrangement of the carbonyl and methyl ligand in 7a-7c has been confirmed by the 13C-13C coupling constant in the 13C NMR spectrum of 7c. A reaction of 4a or 4b with CH3I or 13CH3I yields the acyl compounds trans-[RhI(COCH3)(4-C5NF4)(PEt3)2] (8a) and trans-[RhI(13CO13CH3)(4-C5NF4)(PEt3)2] (8b), respectively. Complex 8a slowly reacts with more CH3I to give [PEt3Me][Rh(I)2(COCH3)(4-C5NF4)(PEt3)](9). On heating a solution of 7a, the complex trans-[RhI(CO)(PEt3)2] (10) and the C-C coupled product 4-methyltetrafluoropyridine (11) have been obtained. Complex 8a also forms 10 at elevated temperatures in the presence of CO together with the new ketone 4-acetyltetrafluoropyridine (12). The structures of the complexes 3, 4a, 5, 6a, 8a and 9 have been determined by X-ray crystallography. 19F-1H HMQC NMR solution spectra of 6a and 8a reveal a close contact of the methyl groups in the phosphine to the methyl or acyl ligand bound at rhodium.     

Synthese und Kristallstruktur der molekularen Clusterverbindung W6Br14

Synthesis and Crystal Structure of the Molecular Cluster Compound W₆Br₁₄ Brownish-black crystals of W₆Br₁₄ are formed in the direct synthesis from W₆Br₁₂ and Br₂ (400 K). The compound crystallizes cubically with neutral cluster molecules ([W₆Br]Br): a = 13.458 Å; Pn3 (Nr. 201); d?(W? W) = 2.653 Å; d?(W? Brⁱ) = 2.616 Å; d?(W? Br^a) = 2.569 Å. The W atoms are 0.03 Å outside of the Br cube faces. The molecules are arranged according to a cF point configuration, but each is rotated ?23° about a threefold axis in order to avoid short inter cluster distances Br^a? Br^a. Nevertheless, via 12 short intermolecular distances per cluster of about d(Brⁱ …? Br^a) = 3.487 Å the clusters are interconnected by forming two independent and interpenetrating 3D nets (Cu₂O type). Although local distortion of the M₆X cluster does not occur, as is expected for this system with 22 electrons per M₆ octahedron, it is assumed that the Jahn-Teller theorem is fulfilled collectively via the low-symmetry nets of intermolecular interactions.     

(+)-(1S, 3S, 6S, 8S)-und (−)-(1R, 3R, 6R, 8R)-4, 9-Twistadien: Synthese und Bestimmung der absoluten Konfiguration

(+)-(1S, 3S, 6S, 8S)-and (?)-(1R, 3R, 6R, 8R)-4, 9-Twistadiene: Synthesis and Absolute Configuration A synthesis and the determination of the absolute configuration of (+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-4, 9-twistadiene ((+)- and (?)- 4 , respectively) is described. Their chiroptical properties are compared with those of saturated twistane ((+)- and (?)- 5 ) as well as with those of the unsaturated and saturated 2, 7-dioxatwistane analogs (+)- and (?)- 9 , and (+)- and (?)- 10 , respectively, which also are compounds of known absolute configurations.     

Nb2Y2X6, a Novel Type of NbIV Compounds with Cross-linked Nb2 and Y2 Dumbbells (Y = Se,Te; X = Br,I)

The compounds Nb₂Se₂Br₆, Nb₂Te₂Br₆, and Nb₂Te₂I₆ were prepared from the elements in sealed quartz ampoulès at 1073 K. The crystalline solids, exhibiting a metallic lustre, are insensitive against moisture and oxygen. All compounds undergo several reversible thermal transitions with temperature (DTA). Beside binary halides only NbYX₃ is present in the gas phase. The structures consist of one-dimensional infinite chains of halogen bridged Nb₂(Y₂)X₄ units containing single side-on bonded Nb₂ and Y₂ dumbbells forming a quasi tetrahedral Nb₂Y₂ cluster (Nb? Nb ? 283.2; 287.5; 293.2 pm; Se? Se ? 230.5 pm; Te? Te ? 267.0; 268.5 pm). The structural and magnetic properties clearly prove the formal oxidation states Nb⁴⁺ and Y^1?, unexpected from stoichiometry. (Structural data: all P2/a (No. 13); Nb₂Se₂Br₆: a = 1254.0(12); b = 689.7(10); c = 662.4(10) pm; β = 98.9(1)°; Z = 2; 1274 hkl; R = 0.066. Nb₂Te₂Br₆: a = 1259.7(13); b = 713.5(9); c = 667.0(9) pm; β = 97.6(1)°; 1557 hkl; R = 0.043. Nb₂Te₂I₆: a = 1347.3(3); b = 742.9(2); c = 714.1(2) pm; β = 98.52(2)°; 1540 hkl; R = 0.026).