Band 39, Heft 12

The new com pound CaZn 2 Al 2 crystallizes in the tetragonal system , space group I4/m m m (N o . 139) with the lattice constants: a = 412.7(3) pm, c = 1167.1(5) pm, d a = 2.828. The structure can be described as an “inverse” ThCr 2 Si 2 -type.

The novel anion SeBr 4 2- was prepared by dissociation of SeOBr 2 with formation of SeBr 2 and subsequent reaction with bromide in acetonitrile solution; it was isolated as the crystalline tetraphenylphosphonium salt. The X-ray structure analysis of [P(C 6 H 5 ) 4 ] 2 SeBr 4 (space group P 1̄ , a = 14.190(3), b = 15.125(3), c = 10.383(2) Å , α = 92.69(2), β = 100.89(2), γ = 92.04(2)° Å , V = 2182.2 Å 3 ) shows the structure to contain monomeric SeBr 4 2- anions with a square planar coordination of Se(II). The mean Se -Br bond length in the anion is 2.598 Å . [P(C 6 H 5 ) 4 ] 2 Se 2 Br 6 was obtained from the reaction of SeBr 4 (which is in equilibrium with SeBr 2 , Se 2 Br 2 , and Br 2 , in solution) and bromide in acetonitrile. It crystallizes in the space group P 1̄, with a = 1 0 . 9 3 3 ( 4 ) , = 11.154(4), c = 10.344(4) Å , α = 79.26(3), β = 72.63(3), y = 81.35(3)°, γ = 1176.7 Å 3 (at -120 °C), and contains a novel type of centrosymmetric Se 2 Br 6 2- ions with square planar Se-coordination. The mean terminal and bridging Se -Br bond lengths are 2.442 and 2.799 Å , resp. Vibrational spectra are reported and discussed.

Ga 2 Cl 4 reacts with hexamethylbenzene in benzene to give (hexamethylbenzene)gallium (I)- tetrachlorogallate(III), (CH 3 ) 6 C 6 G a + GaCl 4 - , in high yield. The complex crystallizes in the rhombohedral space group R 3 m with four formula units per cell. Cell constants are a = 12.449(3) Å and α = 91.01(2)°. In the structure tetrameric clusters can be identified containing two crystallographically independent formula units, one having 3 m and the other three having m symmetry. In both types of (arene)Ga + cations the Ga atoms are symmetrically positioned over the arene ring, 2.43(3) and 2.51(3) Å , respectively, away from the ring plane. Four (arene)Ga + cations and four GaCl 4 - anions are aggregated in such a way that the Ga 1 atoms are surrounded by six or seven chlorine atoms, respectively, at distances in the range 3.16(1) to 3.67(1) Å . The four hexamethylbenzene molecules form an efficient cover around the inorganic [Ga + GaCl 4 - ] 4 framework. Between the tetrameric clusters there are no contacts of the Ga 1 ···Cl Type.

The reaction between complexes [VH(CO) 6-n p n ] (n = 2, p n = Ph 2 P(CH 2 ) 2 PPh 2 ; n = 3, p n = MeC(CH 2 PPh 2 ) 3 ) and [CoX(NO) 2 ] 2 in THF, acetonitrile or acetone, L, yields the products cis-[VL 4 (NO) 2 ]X and [Co(CO) 3-m p n (NO)] (m = 0-3) via the intermediates [V(CO) 5-n p n (NO)] and [V(X)L 3 (NO)]X. Exclusion of X from the first coordination sphere is based on the absence of any halogen dependence of the 51 V shielding. Optimized procedures for the preparation of the hydridovanadium and dinitrosylcobalt complexes are described.

The reaction between [V(THF) 4 (NO) 2 ]Br and various ligands {L} with a N , P. As, Sb, O and S donor/acceptor function leads to the complexes [V(THF) 4-n {L} n (NO)i]Br, where n = 4 [P(OMe) 3 , Me 2 P(CH 2 ) 2 PMe 2 , {N }, {O }, {S}], n = 2 and 3 [{P}, AsEt 3 , SbEt 3 ], and n = 1 [P(OMe) 3, AsEt 3 , SbEt 3 , Ph 2 P (CH 2 ) 3 PPh 2, Ph 2 As(CH 2 ) 2 PPh 2 ]. The constitution of the compounds is established on the basis of 51 V NMR characteristics [(δ( 51 V) and 1 J( 51 V - 31 P)]. The two NO groups occupy cis positions (IR evidence). With isonitriles, [V(THF) 4 (NO) 2 ]X yields the neutral complexes [VX(CNR) 3 (NO) 2 ] as the main products, which exhibit a normal halogen dependence (X = Cl < Br < I) of 51 V shielding. δ( 51 V ) values span a range from +296 (L = THF) to -1100 ppm [½ L = Me 2 P(CH 2 ) 2 PMe 2 ] relative to VOCl 3 . Shielding of the 51 V nucleus decreases in the order PR 3 ≈ CNR > {N } > {S} > {O }; en > dipy. phen > diazadiene > NCR > py > NH 2 Ph; OPR 3 > OSMe 2 > OCR 2 > THF; and PMe 3 > SbEt 3 ≈ AsEt 3 ≈ -PPh 2 > - AsPh 2 . This ordering reflects (counteracting) trends in the polarizability and the π acceptor ability of the ligands. An effect caused by the chelate ring size (5-ring > 6-ring > 4-ring) is also observed and reflects torsional and ring strains.

Sc(acO) 3 was obtained from Sc 2 O 3 and (CH 3 CO) 2 O or from Sc 2 (CO 3 ) 3 and acetic acid. Recrystallization in water yields hexagonal columns of anhydrous Sc(acO) 3 . It crystallizes in the space group P 6 3 /mcm with the lattice constants a = 791.1(3) pm, c = 886.6(7) pm and z = 2. Sc(acO) 3 exhibits a polymeric structure with a linear chain of metal atoms which are connected in each case by three bridging acetato groups. For the Sc atoms results a sixfold coordination in the form of a compressed octahedron with the symmetry D 3d and with distances Sc-O = 208.4 pm. The columns of polymeric Sc(acO) 3 are arranged like in an ideal hexagonal close packing of cylindrical rods.

Oxo-phthalocyaninato-molybdenum (IV), PcMoO, was obtained in form of violet crystals by the reaction of Mo(CO) 6 with phthalodinitrile in toluene at 180 °C in a sealed tube. It crystallizes isotypically with the monoclinic form of PcTiO in the space group P2 1 /c: a = 1344.1(3). b = 1329.2(2), c = 1404.1(3) pm, β = 103.81(1)°, Z = 4. The structure is built up by monomeric molecules in which the Mo atom exhibits a square pyramidal coordination. It is located 69 pm above the plane of the phthalocyaninato ligand and forms a short bond of 166.8 pm to the O atom. The Mo-N distances range from 206.8 to 211.2 pm. In the IR spectrum ν(Mo = O) is observed at 965 cm -1 . Partial oxidation of PcMoO with I 2 yields semi-conducting PcMoOI x (x = 1 .4-2.6) with electrical conductivity of 10 -5 to 10 -4 S/cm.

Dimethyl(phenylchalcogeno)bismuthanes of the general formula (CH 3 ) 2 BiEC 6 H 5 (E = S, Se, Te), the first m olecules with a Bi -Se or a Bi-Te-bond, respectively, were synthesized in good yields by reactions of tetramethyldibismuthane and diphenyldichalcogenides. At room temperature - these thermolabile compounds react quantitatively - with increasing rate in the series S-Se-Te to give CH 3 Bi(EC 6 H 5 ) 2 and Bi(CH 3 ) 3 .

Hexaethyloctaphosphane(6) (1) was proven to possess the structure of a 2,3,4,6,7,8-hexaethylbicyclo[3.3.0]octaphosphane by a complete analysis of its 31 P { 1 H } NMR spectrum. The chemical shifts and coupling constants yielded inform ation about the configuration and conformation of 1.

Mixed ligand complexes of bis(phenyldithiocarbazato)nickel(II) with triphenylphosphane and a number of ditertiary phosphanes have been synthesised. The complexes were characterised on the basis of molar conductance, magnetic moment values, electronic and IR spectra. Out of the five prepared com plexes the mixed ligand complexes with triphenylphosphane and bis(diphenylphosphino) m ethane are paramagnetic, the mixed ligand complexes with bis(diphenylphosphino) ethane, -propane, and -butane are diamagnetic. The complexes were assigned octahedral, square planar or square pyramidal structures. The biological activities of the complexes were also tested.

The dark brown cyclo-thiazeno com plexes [MoCl 3 (N 3 S 2 )] 2 and [WCl 3 (N 3 S 2 )] 2 are obtained by quantitative reactions of MoNCl 3 with (NSCl) 3 and of WOCl 4 or WSCl 4 with excess (NSCl) 3 , respectively. They are diamagnetic, thermally stable up to 200 °C, and only slightly sensitive towards moist air, but react explosively with aqueous bases. According to the IR spectra [MoCl 3 (N 3 S 2 )] 2 is dimerized via chloro bridges whereas the tungsten com pound is associated via the γ-nitrogen atoms of the cyclo-thiazeno ligand. By reaction with [AsPh 4 ]Cl or [PPh 4 ]Cl in CH 2 Cl 2 , the compounds EPh 4 [MCl 4 (N 3 S 2 )] are obtained (E = P, As; M = Mo, W). The crystal structure of AsPh 4 [WCl 4 (N 3 S 2 )] was determined from X-ray diffraction data (1845 observed reflexions, R = 0.045). It crystallizes in the monoclinic space group P2 1 /c with four formula units per unit cell. The lattice constants are a = 1352.4, b = 968.4, c = 2393.8 pm and β = 115.1°. The com pound is built up from AsPh 4 ⊕ cations and [WCl 4 (N 3 S 2 )] ⊖ anions in which the W atoms are coordinated in a distorted octahedral fashion by four Cl and two N atoms of the N 3 S 2 ligand. The WN bond lengths (182 and 188 pm) correspond to douple bonds. The WN 3 S 2 ring is planar and has SN bond lengths between 154 and 161 pm.

An improved synthesis for [VCl 2 (N 3 S 2 )] ∞ , was found in the reaction of VOCl 3 with (NSCl) 3 ; when the reaction is performed in H 2 CCl 2 and (NSCl) 3 is used in excess, the thiazyl-solvate [VCl 2 (N 3 S 2 ) · NSCl] 2 is obtained. [VCl 2 (N 3 S 2 )] reacts with AsPh 4 Cl to form (AsPh 4 ) 2 [VCl 3 (N 3 S 2 )] 2 ; this reacts with AgN 3 in CH 2 Cl 2 suspension to yield (AsPh 4 ) 2 [V (N 3 ) 3 (N 3 S 2 )] 2 · CH 2 Cl 2 . The compounds were characterized by their IR and 51 V NMR spectra. The latter are compared with new 51 V NMR data for [VO 2 Cl 2 ] ⊖ and [VOCl 4 ] ⊖ ; a decrease of 51 V shielding in the order [VO 2 Cl 2 ] ⊖ > [VOCl 4 ] ⊖ > [VX 3 (N 3 S 2 )] 2 2⊖ (X - N 3 > Cl) is found, which is interpreted in terms of increasing polarizability of the ligands and of ring contributions to the extreme deshielding observed with the thiazenovanadates. The crystal structure of (AsPh 4 ) 2 [V(N 3 ) 3 (N 3 S 2 )] 2 · CH 2 Cl 2 was determined from X-ray diffraction data (1496 observed reflexions, R = 0.058). It crystallizes in the triclinic space group P 1̄ with one formula unit per unit cell and with the lattice constants a - 1087, b = 1317, c = 1350 pm, α = 58.8, β = 85.9, γ = 68.0°. The structure consists of AsPh 4 ⊕ ions, CH 2 Cl 2 molecules and centrosymmetric [V(N 3 ) 3 (N 3 S 2 )] 2 2⊖ anions. In the latter. N 3 S 2 ligands are bonded to the V atoms in a chelate manner with short V = N bonds (189 and 172 pm) forming planar VN 3 S 2 rings. The dimerization is accomplished by V -N donor-acceptor interactions (224 pm) involving one N atom of each VN 3 S 2 ring. The vanadium coordination number of 6 is com pleted by three azido groups with V -N bond distances of 200 to 204 pm.

Iminoboranes RB = NtBu (R = Me, Et, Pr; 1a-c) undergo a catalytic cyclodimerisation to 2a-c at -10 to -20 °C, but a thermal cyclotrimerisation to 3a-c at 50 °C. The cyclodimer 2a and the cyclotetramer 4a (R = Me) are reversibly transformed into each other at 20 to 70 °C. The cyclodimer 2d (R = Bu), kinetically stable with respect to the cyclotrimer 3d, yields 3d when reacted with the monomer 1d . The ethyloboration of the new monomer 1a , its cycloaddition with PhN 3 , and its azidosilation by Me 3 SiN 3 are described. The coordination compounds (OC) 4 Cr[(RBNtBu) 2 ] (9a-c) are formed from Cr(CO) 5 (THF) or from Cr(CO) 4 (COD) either with 1a-c or with 2a-c.

Reactions of carboxylic acid anhydrides [(RCO) 2 O where R = CH 3 , C 2 H 5 , n-C 3 H 7 and CHCl 2 ] with excess of chromium (VI) oxide at low temperatures yield chromyl carboxylates, CrO 2 (OOCR) 2 . These compounds are non-conducting in polar organic solvents. IR spectra suggest the presence of both unidentate and bidentate carboxylato groups and discrete Cr = 0 units. The 1 H NMR spectra show the presence of only one type of carboxylato group. Reactions of carboxylic acid anhydrides with CrO 3 in equimolar ratio yield reduced chromium(III) com pounds o f the type CrO(OOCR) at room temperature. Their millimolar solutions in C 6 H 5 NO 2 , CH 3 NO 2 and CH 3 CN are non-conducting. IR spectra, magnetic susceptibility and some other properties have been investigated. Both types of compounds are polymeric in nature having covalent structures.

o-Phenylene-bis(dibromophosphane) (1) is prepared by reaction of P ,P,P′,P′-tetrakis(dim ethylamino)-o-phenylenediphosphane with hydrogen bromide in ether. The reaction of o-phenylene- bis(dichlorophosphane) (2) with CH 3 OH in ether yields o-phenylene-bis(phosphonousacid- dimethylester) (3). The Michaelis-Arbuzov conversion of 3, either by heat or by catalytic amounts of CH 3 I in toluene, yields ophenylene-bis(methylphosphinic-acid-methylester) (4). The reduction of 2 must be carried out with a large excess of LiAlH 4 (1:4) in ether to give o-phenylenediphosphane (5). The cyclic anhydride (6) of P.P′-dichloro-o-phenylenediphosphonous acid is formed when 2 is hydrolyzed in ether with an equimolar amount of water. Complete hydrolysis of 2 with an excess of water gives o-phenylenediphosphonous acid (7). With hydrogen peroxide o-phenylenediphosphonic acid (8) can be isolated.

Tripod ligands of the type RSi(OCH 2 EMe 2 ) 3 (R = Me, Ph; E = P, As) (compounds 3a, b and 4a, b) have been prepared by reacting RSiCl 3 with Me 2 ECH 2 OH (2a, b) in the presence of NMe 3 . 2a, b are obtained from Me 2 EH (1a , b) and paraformaldehyde. Replacement of the cycloheptatriene ligand in M(CO) 3 CHT com pounds (M = Cr, Mo, W) yields the new complexes fac-M(CO) 3 [RSi(OCH 2 EMe 2 ) 3 ] (5a, b-10a, b). The ligand properties of 3a, b and 4a, b have been studied by determining the effects of coordination on the spectroscopic data (ν co , 1 H, 31 P NMR).

Trimeric alkoxydifluoroboranes (F 2 BOR), react with carboxylic acid anhydrides to form bicyclic acyloxyfluoroboranes of the 1.5-difluoro-3.7-dialkyl-2.4 .6 .8 .9-pentaoxa-1.5-diborabicyclo- (3.3.1)nonadiene type. A X-ray crystal structure determ ination of 6a is reported.

The metallacycles [Cl 3 MS 2 N 3 ] 2 (M = Mo, W) 1a and 2a have been obtained from reactions of S 4 N 4 with Mo 2 Cl 10 and WCl 6 , respectively, and from S 3 N 3 Cl 3 with the hexacarbonyls M(CO) 6 . The adducts Cl 3 MS 2 N 3 · CH 3 CN 1b and 2b are formed with acetonitrile, and the salts [Ph 4 As + ][Cl 4 MS 2 N 3 - ] 1c and 2c with addition of Ph 4 AsCl. Reactions of Mo 2 Cl 10 and WCl 6 , respectively, with related S -N com pounds lead predominantly to 1a and 2a; Mo 2 Cl 10 reacts with S 3 N 2 Cl 2 to give 1a , and with [Me 3 SiN] 2 S to give [Cl 3 MoN] x , while WCl 6 yields Cl 4 WNSCl with S 3 N 2 Cl 2 , and 2a with [Me 3 SiN] 2 S. [Cl 3 MoN ] x does not react with S 4 N 4 , but [Cl 3 WN] x forms 2a. Reactions of VCl 4 and VOCl 3 with [Me 3 SiN] 2 S give [Cl 2 V S 2 N 3 ] x , 3. 2c has also been obtained by the reaction of [Ph 4 As + ][Cl 5 WNSCL - ] with [Me 3 SiN] 2 S. The oxidation states of the metal atoms are +6 for 1a-c and 2a-c, and +5 for 3, respectively; as determined by 51 V and 95 Mo NMR spectroscopy and magnetic susceptibility measurements. The UV/VIS spectra of 1b , 1c , 2b, c and 3 are discussed. The electrical conductivity of 3 is reported.

Excess 1,3-dioxane 1 reacts with AgAsF 6 2 to yield a complex [Ag(1,3 -C 4 H 8 O 2 ) 3 ](AsF 6 ) 3, which was characterized by X-ray structure determination. Crystals of 3 are monoclinic, P2 1 /n, a = 939.9(2), b = 1814.0(3), c = 1147.6(3) pm , β = 92.98(2)°, Z = 4, R = 0.049 for 2825 reflections with F > 4σ(F). 3 is a chain polymer with two bridging and one terminal dioxane ligands; Ag-O bond lengths are 242-249 pm. A weak Ag ··· F contact completes a disordered octahedral coordination at silver. No ring opening of 1 occurs on reaction with 2.

Sodium bis(L-cysteinato)zincate(II) hexahydrate (1) and bis(O-ethvl-L -cysteinato)zinc(II) (2) have been prepared from respectively alkaline (pH > 11) and neutral aqueous solutions and their structures determined by X-ray structural analysis. N ,S-coordination of the Zn atoms with the formation of two five-membered chelate rings is observed for both complexes. The deprotonated carboxylate groups in 1 do not coordinate the Zn atom. Dibromo-bis(DL-penicillamine)zinc(II) (3) and dibromo-bis(D-penicillamine)zinc(II) have been isolated from acid solutions with a pH of 2. The penicillamine moieties which are present in the zwitterionic form HS-C(CH 3 ) 2 -CH(NH 3 + ) - COO - behave as m onodentate ligands with the deprotonated carboxylate group as binding site. The role of solution pH in determining the binding properties of cysteine and penicillamine with zinc(II) is discussed.

Cr(CO) 2 [P(OCH 3 ) 3 ][P(CH 3 ) 3 ](η 4 -diene) complexes (6, 7) were prepared photochemically from Cr(CO) 4 [P(OCH 3 ) 3 ][P(CH 3 ) 3 ] (3) and 1,3-butadiene (4) or trans-, trans-2,4-hexadiene (5), respectively. The stereochemistry of 6 and 7 was determined by spectroscopic means (IR , NMR). 6 and 7 form f̲a̲ and a̲f̲ isomers, 6 in addition d̲a̲ and e̲a̲ isomers, which differ in the positions of the donor ligands with respect to the coordinated dienes. They are interconverted by hindered rearrangements of the ligand spheres. The barriers of activation were found for 6 with ΔG 280 ≠ = 42.4 ± 1.2 kJ .mol -1 and ΔG 350 ≠ = 81.4 ± 7 kJ.mol -1 , for 7 with ΔG 280 ≠ = 63.9 ± 1.2 kJ.mol -1 . At 298 K 6 and 7 show dismutations to Cr(CO) 2 [P(OCH 3 ) 3 ] 2 (η 4 -diene) (8, 10) and Cr(CO) 2 [P(CH 3 ) 3 ] 2 (η 4 -diene) (9, 11) until a certain equilibrium between the three related complexes is attained. Identical mixtures are formed from equimolar amounts of 8 and 9 or 10 and 11.

By reaction of a 1-unsubstituted imidazole (im H) with alkali and R 3 ′PAuCl under phase transfer conditions or in MeOH solution R 3 ′PAu (im-N) compounds were obtained where R′ = C 6 H 11 or t-Bu, and imH was imidazole, 2-i-Pr-, 4-NO 2 -imidazole or benzimidazole. When the Ph 3 Sb (or Ph 3 As) homologue was reacted, polymeric [μ-(2-methylimidazolato-N,N′)gold(I)] n was obtained, together with (Ph 3 Sb) 2 AuCl. The X-ray crystal structure of 1-[(C 6 H 11 ) 3 PAu]-2-i-Pr-imidazole confirmed that the gold atom is linearly coordinated (177.0(1)°), with Au - N 2.019(5) and Au -P 2.255(2) Å .

The metal ions Co ++ , Ni ++ , Mg ++ , and Zn ++ form the sandwich complexes [M([12]crown-4) 2 ] ++ with [12]crown-4 in CD 3 NO 2 . From the reaction order of the crown ether exchange a strong outer sphere association between complex and ligand can be inferred. Ligand fluctuation processes occur via an intramolecular associative mechanism from which a very high symmetry of the complexes results.

The reactivity of a di-tert-butylallenylidene tetracarbonyliron complex (1) and a ,μ-di-tert-butyl-allenylideneoctacarbonyldiiron (2) compound towards triphenylphosphane and pyridine were investigated. The reaction of 1 with PPh 3 results in the formation of an ylid complex, di-tert-butylallenylidenetriphenylphosphorane tetracarbonyliron (3). 2 reacts with L = PPh 3 with substitution of one or two CO molecules to give (tBu) 2 C 3 Fe 2 (CO) 7 L 4 and (tBu) 2 C 3 Fe 2 (CO) 6 L 2 5 compounds. Pyridin (py) causes initial displacement of one CO ligand in 2 but subsequent rearrangement results in the formation of 3-t-butyl-4-dimethyl-2-(2-pyridino)pent-2-ene-lylideneheptacarbonyldiiron(0) system (7).

According to a quantum chemical analysis based on energy optimized MNDO calculations the 1.5-sigmatropic reaction of cyclopentadienylphosphanes can occur via a transition state either with retention or inversion of configuration at phosphorus, depending on the ligands within the PR 2 fragment. Electropositive R favour inversion and electronegative R retention of configuration at phosphorus. In addition, given the same ligand R, retention (over inversion) comes to the fore with increasing atomic number of the central atom at the MR 2 unit, i.e. in the order M = N < P < As < Sb.

16 compounds of the types cis-[Pt(PPh 3 ) 2 (4-CH 3 -C 6 H 4 )(Ar)] (cis-6a-g) and cis-[Pt(PPh 3 ) 2 (4-CH 3 O- C 6 H 4 )(Ar)] (cis-7a-g) (Ar = Phenyl ring substituted by at least one electron acceptor or donator substituent) have been synthesized and studied with respect to the thermal reductive elimination of the biphenyl system.

Syntheses of the four at the cyclopropane part alkyl-substituted homofulvenes 6-endo-Ethyl-1,2,3,5-tetramethyl-4-methylenebicyclo[3.1.0]hex-2-ene (endo-1a), 6-exo-Ethyl-1,2,3,5-tetramethyl-4-methylenebicyclo[3.1.0]hex-2-ene (exo-1a), 6-ercdo-Isopropyl-1,2,3,5-tetramethyl- 4-methylenebicyclo[3.1.0]hex-2-ene (endo-1b) and 6-exo-Isopropyl-1,2,3,5-tetramethyl-4-methylenebicyclo[ 3.1.0]hex-2-ene (exo-1b) are reported. Following singulet excitation endo-1a, endo-1b and exo-1b underwent photo-isomerization to 6-Ethyl-1,2,3,4-tetramethyl-5-methylenecyclohexa- 1,3-diene (2a) and 6-Isopropyl-1,2,3,4-tetramethyl-5-methylenecyclohexa-1,3-diene (2b) resp. It is demonstrated, that C-6 - the top of the cyclopropane ring in 1 - is transferred to C-6 - adjacent to the exo-methylene substituent - in the 5-methylenecyclohexa-1,3-diene system 2. A mechanism is suggested.

The striking similarities of the hypsochromic shifts of the longest wavelength absorption observed in the serie 1-3 and 4 -6 are rationalized by means of simple molecular orbital theory.

In small ranges of concentration ascorbic acid yields oscillations in the Belousov-Zhabotinskiitype reaction [substrate/bromate/cerium (sulfuric acid)]. During the reaction ascorbic acid is oxidized and decomposed. The oxidation respectively bromination of the resulting compounds, as oxalic acid, threonic acid, glyceric acid and pyruvic acid, also leeds to oscillatory chemical reactions in the same range of concentration as ascorbic acid.

The use of methanesulfonic acid as solvent and catalyst in the cyclocondensation of 1,2-dialkoxybenzenes with 3-methylbut-2-enoyl chloride to afford indanones 3, thus allowing the preparation of indenes 4 with improved overall yields, is reported. Additionally, structure of dimeric compound 7 a, formed in high yield by thermal treatment of 4a has been determined by com bination of spectroscopic means and selective deuterations.

2-(1-Piperidinyl)-1.3-dithioles (6a-c) can be condensed with benzthiazolium- and benzselenazolium perchlorates (7a-d) to the electron-rich olefines 8a-i. By the same synthetic principle the 2-(3.5-diaryl-Δ 4 -1.3.4-thiadiazolin-2-yliden)-1.3-dithioles 10a-e such as the unsymmetrically substituted bis(3.5-diaryl-Δ 4 -1.3.4-thiadiazolin-2-ylidenes) (12a-d) are acessible. The olefines 8c and h undergo [2 + 2]-cycloaddition reaction to form the cyclobutenes 16a-d, which isomerize spontaneously by electrocyclic ring opening to the 1.3-butadienes 17a-d.

From perianth of Lilium candidum L. a new flavonoid, lilyn has been isolated by column chromatography and identified by 1 H and 13 C NMR spectroscopy as 3-O-[β-D-glucopyranosyl (1-2)β-D-galactopyranoside]-kaempferol.

New ternary compounds of the formula A 2 BX 2 in the orthorhombical K 2 PdP 2 -structure, space group Cmcm, have been prepared from the elements potassium, rubidium (A -element), nickel, palladium, platinum (B -element) and phosphorus or arsenic (X -element). They are isotypic with K 2 PdAs 2 , K 2 PdP 2 and K 2 PtAs2 and are characterized by BX 2 -zig-zag-ribbons surrounded by channel-like arranged alkali atoms. Another group of ternary com pounds with the formula AB 2 X 2 (A = K, Rb; B = Fe, Co, Ru, Rh, Ir; X = P, As) is isotypic with KFe 2 As 2 , KCo 2 As 1 , KRh 2 As 2 , KRh 2 P 2 , ThCr 2 Si 2 -type structure (space group I4/mmm).

Pd(PPh 3 ) 4 reacts with [2.3-bis(diphenylphosphino)- N-methylmaleimide]-palladium (II) chloride to form new dinuclear Pd-complexes. The structures were studied by X-ray crystal structure analysis.

Hydrogen transfer from appropriate hydrogen donors to unsaturated substrates catalysed by transition metal complexes offers some advantages over hydrogenation with molecular hydrogen [1], These reactions have been carried out mainly with stoichiometric or excess amounts o f primary or secondary alcohols [2-7], hydroaromatic com pounds [8] and formic acid [9] as hydrogen donors. Although bis primary diols exhibit relatively high propensity for hydrogen donation [10, 11], little attention has been paid to the em ployment of these com pounds as the source of hydrogen in hydrogenation reactions. The aim of the present investigation was to examine the potential use of 1,4-butanediol as the source of hydrogen in the catalytic reduction of carbonyl com pounds, using ruthenium (II) complexes as homogeneous catalysts.

On the basis of spectroscopic investigations ( 1 H NMR, UV , IR and MS spectroscopy), elemental analysis and degradation reaction the structure of a new alkaloid, discarine F, from the bark extract of Discaria febrifuga Mart is elucidated.