Volume 38, Issue 5

The reaction of tris(bromo-tert-butylphosphino)phosphane, P(t-BuPBr) 3 , with lithium aluminium hydride leads to the title compound P(t-BuPH) 3 (1), which could be isolated in a pure state. 1 is the first partially substituted derivative of iso-tetraphosphane(6), P(PH 2 ) 3 , and was characterized in all details. Because of the chirality of the Z-BuPHgroups, 1 forms two diastereomers with RRS(SSR)- and RRR(SSS)-configuration in a ratio of about 3:1. The conformation of both isomers, which could be deduced from the 31 P NMR parameters, is mainly determined by the steric situation of the molecule.

It is shown that the distances (d) of the 19 longest bonds in 9 homocyclic sulfur rings of type S n (n = 6-20) depend on the torsional angles (τ) which vary between 0° and 140°. The function d = f(τ) is smallest for τ = 90-100° and largest for τ = 0°; the corresponding bond distance variation amounts to 13 pm or 6%. The height of the torsional cis-barrier is estimated from the enthalpy of formation of gaseous S 7 as equal to or smaller than 24 kJ/mol.

(Ph 3 P) 2 Pd(N 3 ) 2 reacts with CS 2 by 1,3-dipolar cycloaddition to give the thiatriazoline- 5-thionato complex (Ph 3 P) 2 Pd(N 3 CS 2 ) 2 . From the reaction of [Ph 4 As] 2 [Co(N 3 ) 4 ] with CS 2 , the isotliiocyanato complex [Ph 4 As] 2 [Co(NCS) 4 ] has been isolated, and the intermediate thiatriazoline-5-thionato complex [Ph 4 As] 2 [Co(N 3 CS 2 ) 4 ] could be detected by its electronic spectrum.

The new compound Rb[I(ICN) 2 ] can be prepared in aqueous solution by simple addition of two mole equivalents of ICN to one formula unit Rbl. The solid is isotypic with Cs[I(ICN) 2 ] and crystallizes in the orthorhombic space group Pmmn with a = 16.246 Å, b = 6.795 Å, c = 4.397 Å and Z = 2. The crystal structure has been solved from diffractometer data and refined to R = 0.035 for 313 observed reflections. The structure may be interpreted as a layer-like package of Rb+ cations and pentahalideanalogous anions [I(ICN 2 ] - . The anionic groups are angular with symmetry mm 2 and φ ( I-I - - I ) = 128.69°, φ(I- - I-C) = 175.5°, φ=(I-C-N) = 177°, d(I - -I) = 3.271 Å, d(I-C) = 2.11 A, d(C-N) = 1.13 A. The cation is surrounded by a distorted cube of iodine atoms with a minimum distance d(Rb-I) = 3.775 Å. Some additional results on the reactions of alkali halides and halogenocyans in different solvents are mentioned and compared with those described elsewhere.

Acyloxyfluoroboranes Trimeric alkoxydifluoroboranes (F2BOR)3 (2) react with organic acid anhydrides by substitution of a ring group OR forming monocyclic acyloxyfluoroboranes of the type 2,2,6,6-tetrafluoro-l,4-dialkyl-l,3,5-trioxa-2,6-diboracyclohexene (3). The X-ray crystal structure determination of 3a shows two conformational isomers: two planar and two non-planar six-membered rings are present in the unit cell. The ring conformation is influenced by weak intermolecular H — F interactions.

While trying to react NbBr 5 with sulfur in a closed tube, crystals of the new modification β-NbBr 5 were obtained. Its X-ray diffraction patterns have sharp reflexions and diffuse streaks showing the presence of a one-dimensional disorder. From the sharp reflexions alone, a statistically averaged sub-structure results; it has the space group Ccmm and the lattice constants a 0 = 644, b 0 = 1867 and c 0 = 615 pm. Taking into account the diffuse streaks, the true structure was deduced; its lattice constants are a = 2a 0 , c = Co, b indefinite due to the disorder. β-NbBr 5 is isostructural to tantalum pentaiodide. It consists of layers of (NbBr 5 ) 2 molecules that are stacked with displacement faults in the direction of b. The bromine atoms have a hexagonal close-packing arrangement.

Synthesis and characterization of non-oxo Mo(IV) complexes with the tetradentate thioether-thiol ligand 2,3,8,9-dibenzo-1,4,7,10-tetrathiadecane(dttd-H 2 ) are reported. MoCl 4 (THF) 2 reacts with dttd-H 2 in THF at room temperature to give the paramagnetic (2.61 BM, 295 K) [Mo(dttd)Cl 2 ]. The chlorine ligands in [Mo(dttd)Cl 2 ] can be substituted by sulfur ligands yielding diamagnetic complexes as [Mo(dttd)(CeH 4 S 2 )], [Mo(dttd)(SC 2 H 4 S)] and [Mo(dttd)(SC 2 H 5 ) 2 ]; with Na 2 S, NaHS or H 2 S, the di-μ-sulfido bridged complex [(dttd)Mo(S) 2 Mo(dttd)] is obtained. The reduction of [Mo(dttd)Cl 2 ] by various reducing agents in the presence of CO or NO yields labile carbonyl and nitrosyl species in solution. In contrast to [Mo(dttd)Cl 2 ], the complexes with MoSe cbromophores showed no reactivity to CO or NO under reducing conditions.

Diazadiene metal tetracarbonyls, DAD M(CO) 4 , (M = Cr, Mo, W; DAD = R-N = CH-CH = NR with aliphatic and aromatic substituents R) show equidistribution of one labelled CO when synthesized from fac-DAD M(CO) 3 (CH 3 CN) as a consequence of intramolecular CO site exchange. The structures of two Mo-complexes (1: R = iso-propyl; 2: R = 2,6-diisopropylphenyl) with DAD's of different bulkiness have been solved by X-ray methods. From the infrared solution spectra, including those of isotopically labelled ( 13 CO, C 18 O) compounds, all of the force constants k 1 , k 2 , k tt , k cc and k cc have been calculated independently. The ratios of interaction force constants deviate sharply from Cotton-Kraihanzel assumptions, perhaps because of the substantial deviation of the iraws-pair of CO groups from linearity (1: 154.5°, 2: 147.9°). The solid state N-Mo, Mo-C and C - O bond lengths are neither in agreement with the generally accepted picture for donor/acceptor influences nor with typical IR data and force constant interpretations. (2 with higher v(CO) and k 1 , k 2 has the longer CO bonds and shorter Mo-C bonds than 1.) The force constant sets have been used to calculate CO frequencies for over 60 labelled compounds with good accuracy (Δv < 2 cm -1 ).

The reaction of C 5 H 5 (CO) 2 Mn[C(C 6 H 5 )F] with n-C 4 H 9 Li results in cleavage of the C(carbene)-F bond and formation of C 5 H 5 (CO) 2 Mn[C(C 6 H 5 )n-C 4 H 9 ]. In a similar way fluoride can be abstracted by ethanol to yield C 5 H 5 (CO) 2 Mn[C(C 6 H 5 )OC 2 H 5 ].

The cationic carbyne complex [(CO) 5 WCNEt 2 ]BF 4 (1) reacts with potassiumdiphenylamide, KNPh 2 , with nucleophilic addition of the amide anion to give (CO) 5 W[C(NEt 2 )NPh 2 ] (2). The corresponding reactions with KPPh 2 , KPEt 2 , KPMePh, NaSbPh 2 and NaBiPh 2 yield the complex [(CO) 5 W(CNEt 2 )] 2 (3), which is formed by reductive dimerization of two carbyne fragments. In case of KPMePh the carbene complexes (CO) 5 W[C(NEt 2 )PMePh (4) and trans-(MePhPH)(CO) 4 W[C(NEt 2 )PMePh] (5) are also obtained. On warming in solution 5 spontaneously rearranges to the novel cyclic carbene complex (6). Reaction conditions, properties and spectroscopic data of the new compounds are reported.

Reaction of trans-bromotetracarbonyl(phenylcarbyne)-complexes of chromium, molybdenum and tungsten and trans-bromotetracarbonyl(methylcarbyne) complexes of chromium and tungsten with the bidentate ligands 2,2′-bipyridyl and 1,10-phenanthroline results in the replacement of two carbonyl groups leading to very thermostable carbyne complexes with the general formula Br(CO) 2 LMCR (L: 2,2′-bipy, ophen; M: Cr, Mo, W; R : CH 3 , C 6 H 5 ).

Abstract η 3 -Allyl- or η 3 -methallyl-η 5 -cyclopentadienylpalladium react with hydrogensulfide at - 78 °C with selective cleavage of the cyclopentadienyl group to give the dimeric, thermolabile η 3 -allyl- or η 3 -methallylhydrogensulfidopalladium (2, 2a), which decompose above ≈ - 60 °C to palladiumsulfide and propene or isobutene. The new compounds have been characterised by 1 H NMR, IR and Raman spectroscopy. Similarly, η 3 -allyl- and η 3 - methallylhydrogensulfidoplatinum (6, 6 a) have been prepared from hydrogensulfide and η 3 -allyl- and η 3 -methallyl-?75-cyclopentadienylplatinum, respectively. From bis(??3-allyl)- or bis(?y3-methallyl)palladium and H2S rj3-allyl- or ??3-methallylhydrogensulfidopalladium (2', 2a') have been obtained and their IR spectra and physical properties found to differ from those of 2 or 2a.

η 3 -Allylhydrogensulfidopalladium (6) reacts with bis-(η 3 -allyl)- (4) or η 5 -cyclopentadienyl-η 3 -allyl-palladium (11) with elimination of propene to give the known η 3 -allylpalladium- sulfur-cluster (2). The same method was used to prepare the first bimetallic η 3 -allyl-Ni-Pd-, Ni-Pt- and Pd-Pt-sulfur complexes 12-14 (IR-spectra); their structures are still unknown. The polynuclear η 3 -methally Ipalladium- and -platinum-sulfur complexes 2 a and 3 a, soluble in benzene and toluene, have been prepared from the corresponding bis(η 3 -methallyl)metal compounds and H 2 S. In benzene, 2 a may have a structure in which the four palladium atoms adopt a square planar (2a′) or tetrahedral (2a″) geometry.

η 3 -Allylhydrogensulfidonickel (2) reacts with n-butyllithium with elimination of lithium sulfide and formation of the ionic η 3 -allylnickel-sulfur-cluster [(η 3 -C 3 H 5 Ni) 3 S 2 ] + [Li(THF) 2 ] - (4). The crystal structure of the analogous THF-TMEDA-adduct (4′) indicates that the nickel and sulfur atoms of the anion adopt a trigonal bipyramidal arrangement, in which the sulfur atoms are at the apices of the bipyramid. The Li(THF) 2+ cation in 4 can be replaced by the (n-C 4 H 9 ) 4 N + cation (5). The 1 H NMR spectra suggest the presence of two stereoisomers of the anionic clusters in 4 and 5 having C 3h and C s symmetry. In the reaction of η 3 -allyl- or η 3 -methallylhydrogensulfidopalladium (6, 6 a) with n-butyl-lithium crystalline compounds having the composition RC 3 H 4 PdSLi(THF)≈ 4 , R = H, CH 3 (7, 7 a) are obtained; their 1 H NMR spectra also reveal the existence of the two stereoisomers having C 3h and C s symmetry. The same type of stereoisomerism is observed with the crystalline [(n-C 4 H 9 ) 4 N] + [(η 3 -C 3 H 5 Pd) 3 S 2 ] - (8) obtained from 7 and (n-C 4 H 9 ) 4 N+ClO 4 - . For 7 and 7 a an ionic structure consisting of trigonal bipyramidal (η 3 -RC 3 H 4 Pd) 3 S 2 - anions and Li 3 S(THF) 4 + cations is proposed.

In the pyrolysis of 1,2,3-benzoselenodiazole using a short-distance furnace, a short-lived intermediate is detected photoelectron spectroscopically. Mass spectra recorded under similar conditions suggest an isomer C 6 H 4 Se rearranging to the more stable final product 6-fulveneselone. The ionization pattern obtained by computerized spectra stripping is assigned to benzselenirene by molecular radical cation state comparison based on MNDO calculations.

The trimethylsilylalkyl acetoacetates 1 b and 2 b as well as their carba analogues 1 a and 2 a have been reduced microbiologically by Kloeckera corticis (ATCC 20109), leading to the corresponding ( + )-3(S)-hydroxybutanoates 3b, 4b, 3a, and 4a. The enantiomeric purity was found to be 80% (3a, 3b, 4b) and 65% (4a), respectively. The reduction of lb and 2b is - to our knowledge - the first example for a controlled microbiological transformation of organosilicon substrates.

Compounds cis-[Pt(PPh 3 ) 2 (3-X-C 6 H 4 ) 2 ] [X = F, Cl, CF 3 , CH 3 O, (CH 3 ) 2 N] and cis- [Pt(PPh 3 ) 2 (3-X-C 6 H 4 )(Y-C 6 H 4 )] [X = F / Y = H, 4-F, 4-CF 3 , 4-CH 3 O; X = Cl/Y = 4-F; X = CF 3 /Y = 4-F; X = CH 3 O/Y = 4-F] have been synthesized and studied thermally with respect to the reductive elimination of disubstituted biphenyls. Activation parameters ⊿H≠ and ⊿S≠ are reported and discussed.

19 F NMR chemical shifts of 14 fluorine substituted cis-Bis(phenyl)bis(triphenylphos-phane)platinum(II) compounds are discussed with respect to d π p π -interactions between platinum and sp 2 -hybridized carbon.

The long-sought ethylen fluoronium ion (2) is generated as an intermediate in the dissociative ionization of 1-fluoro-2-(p-methyl)phenoxy ethane (4). However, prior to collisionally induced dissociation 2 undergoes ring-opening, associated with hydrogen migration, to form 1-fluoroethyl cation (3). Other decomposition pathways of the molecular ions of 4 involve (i) direct formation of 3 via a combination of C-O-cleavage (loss of ArO -) and [1,2] hydrogen migration (18%) and (ii) complete positional loss of the a-and β-methylene hydrogen atoms (34%). The remaining 48% of the molecular ions of 4 dissociate via anchimeric assistance of the fluorine in the elimination of ArO·, thus giving rise to the formation of 2.

The reaction of substituted cinnamonitrile derivatives with cyanoacetanilide and ethyl acetoacetate is reported. Several new polyfunctional pyridine and pyran derivatives could be synthesised. The structures of the prepared compounds and the mechanisms of their formation is reported.

The amino acids alanine, valine, leucine, isoleucine, norvaline, α-amino butyric acid, and β -methyl aspartic acid are utilized as substrates for organocobalamin syntheses under “oxidizing/reducing” conditions. In the presence of V +3 as the reducing agent, free radicals are generated by the reaction of oxygen radicals with the amino acids through hydrogen atom abstraction. These amino acid radicals then combine with the cobalt atom of vitamin B 12 r to yield the respective organocobalamins. The cobalamin obtained from the reaction of β-methyl aspartic acid is a possible intermediate in the coenzyme B 12 dependent skeletal rearrangement of β-methyl aspartic acid to glutamic acid. HPLC analysis of the cobal-amins prepared from D, L-alanine indicates that the corrin ligand is relatively ineffective at promoting asymmetric syntheses under these conditions.

A tricyclic 1,1,1-tricarbonyl-2,3,1-diazaferrole derivative (1) reacts photochemically with 1,3-dienes with formation of [4 + 2]-cycloadducts. Introduction of substituents in the 1- or 1,4-positions of the diene or of electron releasing groups in the dienophile results in an inhibition of the cycloaddition. The reaction proceeds stepwise via photodissociation of carbon monoxide, coordination of the diene to iron, intramolecular photocycloaddition, and re-uptake of carbon monoxide. No cycloaddition occurs if the complexed diene is allowed to react thermally. X-ray structural analyses of 1 and its cycloadduct with 2,3-dimethylbutadiene (3d) reveal the presence of a novel type of three electron metal - diazene bond for both compounds and delocalized bonding for the diazaferrole 1.

Novel trialkylstannanedithiocarboxylato complexes are formed in a one-pot reaction of R 3 SnCS 2 Li (R = benzyl, methyl, cyclohexyl) with BrM(CO) 5 (M = Mn, Re) in a THF/dioxane solution. Tetracarbonylmetal species could be detected by IR spectroscopy in all cases. The more stable rhenium chelate complexes, R 3 SnCS 2 Re(CO) 4 , were isolated by chromatographic separation as yellow, low-melting solids with 10-20% yield.

The photochemical transformation of 5,6-Dehydrokawain (1) to rel-(lR,6S,7S,8S)-5-methoxy-7-phenyl-8-[6-(4-methoxy-2-pyronyl)]-1-(E)-styryl-2-oxabicyclo[4,2,0]octa-4-en-3-one (2) by irradiation with a light bulb [1] is con-firmed. Kawain (3) turns out to be resistent to photochemical reaction in several tests. During irradiation by a Hg-lamp a transformation to cis-Kawain (4) takes place, however.

The absolute configuration of julifloridine is proposed to be 2 R, 3 R, 6 R through 13 C Spectra, 1 H NMR Spectra,