Volume 44, Issue 3

The crystal structures of Na 3 SbSe 4 , K 3 SbSe 4 and [Ba(en) 4 ] 2 [Ba(en) 3 ](SbSe 4 ) 2 contain isolated tetrahedral anions SbSe 4 3- , which are the first examples of selenoantimonates(V). Na 3 SbSe 4 (space group 143m , a = 750.1(2) pm, Z = 2) is an isotype of the (NH 4 ) 3 SbS 4 -structure type; K 3 SbSe 4 (space group R3c, a = 1137.5(4) pm, c = 1359.6(4) pm, Z = 6) forms a slightly distorted variant. In the crystal structure of [Ba(en) 4 ] 2 [Ba(en) 3 ](SbSe 4 ) 2 (space group P2 1 , a = 965.8(4) pm, b = 1764.8(8) pm, c = 1463.2(6) pm, β = 90.8(1)°, Z = 2) the cations are in six- and eight-fold coordinations by the bidentate ligands.

Reaction of [(en) 2 Co(H 2 O) 2 ](ClO 4 ) 3 with the dichlorides of nickel, magnesium , and zinc, leads at an pH of ca. 8 to the heterometallic, isomorphous complexes [M II {(OH) 2 Co III (en) 2 } 3 ](ClO 4 ) 4 Cl·3H 2 O. The central metal(2 +) cations of these complexes are surrounded octahedraily by three [(en) 2 Co(OH) 2 ] + chelate ligands. This has been confirmed by X-ray structure analyses. The cation antipodes of the racemic salts exhibit the conformations Δ (⋀ ⋀ ⋀) / ⋀ (Δ Δ Δ) .

NdSe 1,9 has been prepared as grey, strongly reflecting platelets by reaction of elemental neodymium with selenium in the ratio 1 :2 and subsequent chemical vapour phase transport with iodine. It crystallizes in the tetragonal space group P4 2 /n with a = 925.36(7), c = 1679.2(3) pm and Z = 20. The structure determination results in a formulation of NdSe 1,9 as Nd 20 (Se(I) 2 ) 8 Se(I) 2 ⃞ 2 Se(II) 20 , where the defect layer built from the Se(I) 2 2- and Se(I) 2- ions corresponds to the F layer in the PbFCl substructure.

Di-tert-butylfluorosilyl-tert-butylphosphane (1) reacts with n-C 4 H 9 Li to give the lithium salt (CMe 3 ) 2 SiF-PLi(THF) 3 CMe 3 (2) and butane. The crystal structure of 2 has been determined. Fluorosilylphosphanes of the type (CMe 3 ) 2 SiFP(R)CMe 3 [R = SiMe 3 (5), SiCl 2 Me (6). SiCl 3 (7), SiF 2 C 6 H 5 (8), BFN (SiMe 3 ) 2 (9), SiClMeP(CMe 3 )SiF(CMe 3 ) 2 (10)] are obtained in the reaction of 2 with halogenosilanes and -borane. 6 and 7 undergo rearrangement via chloro-fluoro exchange reaction to give (CMe 3 ) 2 SiCl-P(SiClRF)CMe 3 [R = Cl (11), Me (12)].

A m ino and Im inovanadium (V) C om pounds, Preparation, 5IV NM R Spectra The reaction o f V O C l3 with rm -butylam ine and silylated derivatives has been studied. 0 = V C 1 2[N'C4H 9(R)] (R = SiM e3, SiM e2NH'C4H 9), 0 = V (0 S i M e 3)2Cl and binuclear vanadium (V) com plexes with bridging oxo and nitrogen ligands have been prepared; their spec­ troscopic data ('H N M R ,51V N M R , IR) are reported. A simple route for preparing'C4H 9N =V C 13 and ['C4H 9N = V (0)C 1]" is described including com plex formation with pyridine and chloride ions.

(dmb) 2 IrCH 3 (dmb = 2.3-dimethylbuta-1.3-diene) reacts with Ph 3 CBF 4 in CH 2 Cl 2 to form the cation [(dmb) 2 Ir] + which crystallizes as the adduct [(dmb) 2 Ir(OCMe 2 )]BF 4 from acetone solution. The labile acetone ligand is easily displaced by pyridine, cyclohexylisonitrile, phosphane and arsane donor molecules. X-ray diffraction analysis of [(dmb) 2 Ir(AsPh 3 )]BF 4 reveals tetragonal pyramidal coordination at the iridium atom with the arsane ligand in axial position and with isolated BF 4 anions. Spectroscopic data of the new [(dmb) 2 IrL]BF 4 compounds are discussed and related with metal-ligand bond interactions.

A lkylbrom ogerm anes, Synthesis, C V D Feeding G as, G erm anium /Copper Mixtures From the copper-catalyzed reaction o f germanium powder with dibrom om ethane at 310 °C a mixture o f alkylbrom ogermanes is obtained. The major products are CH 3G eB r3, Br3G eC H 2Br From the copper-catalyzed reaction of germanium powder with dibromomethane at 310 °C a mixture of alkylbromogermanes is obtained. The major products are CH 3 GeBr 3 , Br 3 GeCH 2 Br (1), CH 2 (GeBr 3 ) 2 (2) and (CH 2 GeBr 2 ) 3 (3). The product distribution parallels the analogous reaction with dichloromethane reported previously. All com pounds were characterized by analytical and spectroscopic data, and can be converted into the corresponding hydrides.

1,3-Diisopropyl-2,2-dimethyl-1,3,2,4λ 2 -diazasilastannetidine (1b) and -plumbetidine (2b) are dimeric [(1b) 2 , (2b) 2 ] in solution. At room temperature the structure of (1b) 2 is fluxional. The dynamic behaviour is interpreted - on the basis of 1 H. 13 C, 29 Si and 119 Sn NMR data - as an intramolecular process in which the four-membered rings keep their identity. Such a process involves either concerted opening of the two coordinative Sn - N bonds and mutual slippage of the two rings, or consecutive cleavage of one of the coordinative Sn - N bonds and rotation about the other one. At room temperature the dimer (2b) 2 is in equilibrium with its monomer 2b, whereas at low temperature the dynamic process corresponds to that established for (1b) 2 . In solutions which contain a mixture of the dimers (1b) 2 and (2b) 2 , the presence of the mixed dimer 1b/2b can be proved unambiguously by consistent 29 Si, 119 Sn and 207 Pb NMR data.

The crystal structure of [AsPh 4 ] 2 [Pb(S 2 C=C(CN) 2 ) 2 ] has been determined by X-ray diffraction. In the pyramidal complex anion [Pb(S 2 C=C(CN) 2 ) 2 ] 2- Pb is coordinated to the sulfur atoms of the dithiolates. The geometry is indicative for a stereochemically active lone-pair at the apex of the square pyramid.

Cs 3 As 7 , a compound with cage-like As 7 3- anions, has been prepared from the elements in sealed quartz ampoules at 820 K. The ruby-red compound undergoes a first order phase transition at 640 K and is obtained as microcrystalline samples. The structure of the low-temperature α-modification is not known, but β-Cs 3 As 7 belongs to the plastically crystalline β-Rb 3 P 7 type of structure (F m 3̄ m , a (673 K) = 1169,2(1) pm). Cs 3 As 7 melts under its own vapour pressure at 1061 K, and is easily soluble in liquid ammonia. From those solutions ruby red crystals of Cs 3 (NH 3 )As 7 precipitate. In dynamical vacuum NH 3 is evaporated in the region of 300 to 520 K, resulting in Cs 3 As 7 . Cs 3 (NH 3 )As 7 crystallizes in the space group P2 1 /a (a = 2759.0(12) pm, b = 744.1(3) pm, c = 751.5(3) pm, β = 90.16(5)°; Z = 4). The structure is closely related to the plastically crystalline β-Rb 3 P 7 type structure (Li 3 Bi variant). The heptaarsanortricyclene anion is coordinated by cesium atoms, connecting the anions to a three dimensional arrangement. The anion exhibits a differentiation of As - As bond lengths typical for ionic nortricyclenes (d(basis) = 251.2 pm; d(basis-bridge) = 235.5 pm; d(bridge-bridgehead) = 240.1 pm). The distances Cs to As are in the range 372 to 401 pm. The cesium atoms are surrounded by three resp. four As atoms and the NH 3 molecules. The FIR and Raman spectra are given for different temperatures as well as of an en-solution of Cs 3 (NH 3 )As 7 . The valence vibrations of NH 3 are found at 3175 (A 1 ) and 3320 cm -1 (E ). The fundamental vibrations of the three-membered ring of different heteronortricyclenes with P and As are compared and yield a correlation factor χ = 0.57(1) for the observed frequencies between P 3 and As 3 . The band gaps E G are determined from the diffuse reflexion at 2.14 eV for Cs 3 (NH 3 )As 7 and 2.00 eV for Cs 3 As 7 .

The crystal structure of the binuclear copper(II) complex. [Cu 2 (L)(2-pyridonato)] was determined by X-ray diffraction, where H 3 (L) represents the Schiff base ligand derived from 1,3-diaminopropane-2-ol and acetylacetone. Two copper(II) ions are bridged by alkoxide and 2-pyridonate groups with a Cu-Cu separation of 3.249(2) Å . Ferromagnetic interaction is found to be operating in this complex, which is attributed to the small dihedral angle (121°) between the two planes containing the copper(II) ion.

In order to study the properties of sulfur coordinated transition metal centers, [Mo(NO)(Cl)(dttd)] (1) (dttd 2- = 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane(2 -)) was synthesized. It shows no reaction with AgPF 6 , but it reacts very rapidly even at low temperatures with liquid ammonia and dialkylamines HNR 2 (HNMe 2 , HNEt 2 ) yielding the corresponding amidocomplexes [Mo(NO)(NR 2 )(dttd)] (R = H 4, Me 2, Et 3). For these reactions an associative mechanism is suggested. X-ray structure analyses of [Mo(NO)(Cl)(dttd)] (1) and [Mo(NO)(NMe 2 )(dttd)] (2) show the Mo centers to be coordinated pseudo-octahedrally by two trans thiolato S, two cis thioether S atoms and the two cis coligands NO and Cl or NO and NMe: , respectively. Both dialkylamido complexes (R = Me 2, Et 3) show no coalescence of the two N(alkyl) signals in the 1 H NMR spectra up to 140 °C, the NH-Signals of 4 coalesce at 70 ± 5 °C (⊿G* = 73 ± 1.5 kJ mol -1 ). The amido ligands act as σ - π four electron donor ligands such that the Mo center obtains a formal 18 electron configuration and the Mo-NR 2 bond represents a Mo = N double bond. This follows from the short Mo-N distance (192.4(8) pm) and the planarity of the N(alkyl) atom of 2 as well as the stability of the Mo - NR 2 bond (R = H, M e, Et) with respect to rotation. Since sterical effects can be excluded, the high rotation barriers must be due to exclusively electronic effects.

The preparation and characterization of some anionic mixed ligand com plexes of Co(II), Ni(II) and Cu(II) containing the two anionic ligands alkyldithiocarbonate and oxinate are reported. The ionic nature of the complexes was inferred from the conductivity data. Alkyldithiocarbonates act in these complexes as bidentate ligands. Based on the spectroscopic and magnetic data the complexes appear to possess pseudo-octahedral metal coordination.

Reaction of 1,3,5-tris(dimethylamino)benzene (TDMAB ) with 1,2,3,4,5,6-hexacyanobenzene (HCNB) in acetonitrile solution gives - depending on the crystallization method - two different products: dark needles of a 1:1 (1) and black compact crystals with a metallic lustre of a 2:1 (2) charge transfer complex. 2 crystallizes in the triclinic space group P1 , Z = 1, a = 9.9489(22), b = 10.0555(21), c = 10.1418(20) Å , α = 115.006(16)°, β = 102.820(17)°, γ = 93.647(18)°, V = 882.3 Å 3 , d c = 1.2 g cm -3 , measured at room temperature, R = 0.053 for 2670 observed independent reflections and 301 parameters. The structure contains isolated “trimers” of one HCNB acceptor which is “pancaked” by two TDMAB neighbors. The arrangement of these trimers in the lattice results in alternating HCNB and TDMAB sheets. The solid is diamagnetic. 1 could not be obtained in crystals suitable for a single crystal X-ray investigation. Its paramagnetism which is observed immediately after preparation disappears in the course of several days.

CD and UV spectra of four chiral 11-cis-retinal Schiff bases obtained by condensing the aldehyde with asymmetric amines are used to gain structural information about the polyene conformation. The spectra are temperature-dependent indicating the same 12-s-cis/trans equilibrium as in 11-cis-retinal. In addition, CD absorptions arise at lower temperatures whose only origin is the inherent dissymmetric nature of the retinylidene Chromophore. CNDO /S-calculations performed on the basis of force-field optimized geometries give results which can partially be rationalized on the basis of experimental data. Quantitative agreement is obtained in the case of chiral hydrogen-bonded dimers.

The absolute configurations of the known juglomycins A (1) and B (2) have been elucidated by single crystal X-ray structure analysis of 1 and its 6,8-dibromo derivative (1b). The structure of 2 has been corrected; it differs from 1 in its configuration at C-4', and not at C-3' as previously assumed. Relationships with the closely related isochromanquinone antibiotics are discussed.

A presumed precursor of the juglomycins, (2S, 3'R, 4'R)-2,3-dihydro-juglomycin A (3), has been isolated and its X-ray structure determined. 3 forms an equilibrium with a novel hemi-ketal (4). The structures of new juglomycins (C, D, E, F) and some derivatives have been elucidated and their structure/activity-relationships are discussed.

The preparation and spectroscopic characterization of the sulfonium salts SH 3 + AsF 6 - and SD 3 + SbF 6 - is reported. SCl 3 + SbF 6 - is synthesized by chlorination of SH 3 + SbFA - with Cl 2 in liquid SO 2 .

The reduction of Cp'MCl 4 complexes (Cp' = η 5 -C 5 H 5 , η 5 -C 5 Me 5 ; M = Nb, Ta) in the presence of excess PMe 3 , leads to the highly reactive products Cp'M (PMe 3 ) 3 Cl 2 . One or two PMe 3 ligands of these compounds can be substituted by CO or CO 2 toyield Cp'M (PMe 3 ) 2 (CO)Cl 2 , Cp'M(PMe 3 )(CO) 2 Cl 2 and an oxo complex.

Di-trichloroacetimide, HN(COCCl 3 ) 2 . was prepared by the reaction of trichloroacetic acid with trithiazylchloride at 60 °C. The compound was characterized by its IR spectrum as well as by an X-ray structure determination: Space group P 1, Z = 2, 1662 observed independent reflexions, R = 0.034. Lattice dimensions at 17 °C: a = 640.9(2); b = 924.1(3); c = 943.0(2) pm; α = 92.11(2)°; β = 106.53(3)°; γ = 99.02(3)°. The compound forms the Z,Z(trans-trans)isomer. There is no intermolecular hydrogen-bonding.

The colourless compound Na 4 OI 2 : has been prepared and characterized by X-ray diffraction techniques. Na 4 OI 2 : crystallizes in a tetragonal body-centered lattice with a = 467.7(1) pm, c = 1602.0(3) pm (Z = 2) and is isotypic to K 2 NiF 4 .