Volume 37, Issue 3

Four silver(I)-germanates have been prepared from the binary components Ag 2O and GeO 2 by solid state reaction applying elevated oxygen pressures (2500-3000 bar). Ag 6 Ge 2 O 7 isisostructural to Ag 6 Si 2 O 7 (II) [P2 1 ,a= 16.268(3), b = 10.021(2), c = 5.320(1) Å, β = 90.85(2)°], Ag 10 Ge 4 O 13 to Ag 10 Si 4 O 13 [PT, a = 11.731(3), b = 9.147(3), c = 8.727(4) Å, a = 99.33(2), β = 91.61(1), γ = 114.27(2)°]. According to the results of preparative investigations and chemical analysis there are two further phases in the system Ag 2 O/GeO 2 of compositions ′Ag 2 GeO 3′ and ′Ag 2 Ge 2 O 5 ′.

Tri-n-butylfluorophosphonium bromide and N-trimethylsilylphosphinimines R 3 P=N-SiMe 3 react with formation of trimethylsilyl bromide and fluoride and mixed phosphiniminophosphonium bromides/fluorides, [Bu n 3 P-N=PR 3 ]Br/F. Metathetical reactions with sodium iodide, ammonium hexafluorophosphate and potassium Perchlorate yield the corresponding phosphiniminophosphonium iodides, hexafluorophosphates and perchlorates, respectively. The cations [Bu n 3 P-N=PR 3 ] + behave as phase-transfer agents. In the presence of these cations permanganate anion is transferred from aqueous solutions into benzene.

Polymeric bis(dimethyl- and diphenylglyoximato)-complexes of Fe(II) and Co(II) with 4,4′-bipyridine as a bridging ligand have been synthesized from the glyoximato metal complexes and 4,4′-bipyridine in ethanol. The Co(II) compounds are paramagnetic and surprisingly stable against oxidation. The iron complexes are weak electrical conductors with approximately 10 -9 Ω -1 cm -1 . Bis(dimethylglyoximato)-4,4′-bipyridine cobalt(II) crystallizes triclinic in the space group PT with Z=1. The crystal structure is built up by linear chains of alternating Co(II) glyoximato complexes and axial bonded 4,4′-bipyridine bridges. The compound is characterized by strong Co-N-bonds of 189 pm within the glyoximato moiety and weak bonds of 228 pm to the bipyridine ligand. The two heterocycles of the bipyridine are coplanar, therefore the local symmetry of the complex is D 2h .

The reaction of S 4 N 4 with PdCl 2 in methanol yields among other products the dinuclear complex Pd 2 (S 3 N) 2 (S 3 N 2 ) (D): dark red needles, space group R"3̄ with a = 32.759(15), c = 6.516(4) Å and Z = 18. The structure of D was determined by an X-ray analysis. Each palladium atom is part of an almost planar PdS 3 N metallocycle. The SNSNS group acts as a bridge whereby each of its terminal S atoms is bonded to both Pd atoms. The Pd atoms possess a square planar coordination by four S atoms. The coordination planes form an angle of 114.9°. The Pd-Pd distance of 2.921(2) Å is rather short.

N-Substituted 2-Amino-4,4,5,5-tetrakis(trifluoromethyl)-l,3,2 λ 3 (λ 5 )-dioxaphospholanes, Dilithium Perfluoropinacolate, Diazadiphosphetidine, 2,2,2 -Trichloro -4,4,5,5 -tetrakis (trifluoromethyl) -1,3,2 λ5 -dioxaphospholane MeN(PCl 2 ) 2 reacts with Li 2 [0C(CF 3 ) 2 C(CF 3 ) 2 O] to give MeN{P[0C(CF 3 ) 2 C(CF 3 ) 2 O]} 2 which adds chlorine under formation of MeN{PCl 2 [0C(CF 3 ) 2 C(CF 3 ) 2 O]} 2 . The chlorophosphorane decomposes slowly to yield PCl 3 [0C(CF 3 )C(CF 3 ) 2 O] and the diazadiphosphetidine {MeNPCl[OC(CF 3 ) 2 C(CF 3 ) 2 O]} 2 .

(Me 2 PCH 2 ) 2 PMe (3) is obtained from MePCl 2 (2a) or MeP(OPh) 2 (2b) and LiCH 2 PMe 2 (1). The oxides [Me 2 P(O)CH 2 ] 2 PMe (4) and [Me 2 P(O)CH 2 ] 2 P(O)Me (5), are formed on the reaction with air. Quaternisation with Mel gives the salts [(Me 3 PCH 2 ) 2 PMe]I 2 (6) and [(Me 3 PCH 2 ) 2 PMe 2 ]I 3 (12). For comparison, also the isoelectronic (Me 3 SiCH 2 ) 2 PMe (7), and (Me 3 SiCH 2 ) 2 P t Bu (8), are synthesized and transformed to their methylphosphonium salts 10 and 11. With CH 2 Br 2 , 3 forms the six-membered heterocycle [MeP(CH 2 PMe 2 ) 2 CH 2 ]Br 2 (13a), which could not be isolated in a pure state, however. 3 may be metalated by LiBu: Li[Me 2 PCHP(Me)CH 2 PMe 2 ] (15), is obtained, but a second metalation step could not be observed. The hydrolysis of 12 under unusual mild conditions (H 2 O or H 2 O/CH 3 OH) gives [Me 2 P(O)CH 2 PMe 3 ]I (16), and [Me 4 P]I (17), as main products. Properties and NMR data of the new compounds are described.

The pseudohalogens (XCN) 2 (X = S or Se) react with n-C 5 H 5 Co(CO) 2 and n-Me 3 SiC 5 H 4 Co(CO) 2 with formation of the 18 electron complexes, RCo(CO)(XCN) 2 (R = n-C 5 H 5 or n-Me 3 SiC 5 H 4 ). By reactions with X(CN) 2 (X = S or Se), the cyclopentadienyl cobalt dicarbonyls are transformed into the mixed complexes, RCo(CO)(CN)(XVN) (R = n-C 5 H 5 or n-Me 3 SiC 5 H 4 . All the compounds are characterized by elemental analysis, IR, electronic and 1 H NMR spectra. The thiocyanogen derivatives undergo linkage isomerism (N→S) in polar solvents.

The first phosphorus arsenic polycycle t-Bu 6 As 2 P 6 (1) was synthesized by dehalogenation of a 3:1 mixture of tert-butyldichlorophosphane and phosphorus trichloride using magnesium. 1 has been characterized by spectroscopic methods and by a crystal structure analysis having the t-Bu 6 Ps-analogous 2,2′,3,3′,4,4′-hexa-tert-butyl-l′-diarsa-2,2′,3,3′,4,4′-hexaphospha- bicyclobutane structure. In solution, the rotation around the exocyclic As-As bond is restricted already at room temperature. 1 crystallizes triclinically in the space group PT (No. 2) with a = 919.4 pm, b = 924.3 pm, c = 1171.7 pm, a = 97.21°, β = 102.98°, γ = 112.75°, and Z = 1 formula unit (V = 0.8694 nm 3 , D x = 1.295 Mg · m -3 ). The crystal structure has been solved by 'direct methods' and refined to R = 0.048 with 2131 observed reflections. The molecule with symmetry C 1 consists of two trans oriented and slightly folded four-membered P 3 As rings. The exocyclic bond length (d(As-As) = 244.1 pm) as well as the average endocyclic bond lengths d̅(As-P) = 235.6 pm; 3d̅(P-P) = 222.6 pm) are normal. The arrangement of the tert-butyl substituents with average bond lengths d̅(P-C) = 189.9 pm and d̅(C-C) = 1 5 2 . 5 p m is all-trans.

S-Perfluoroalkyl-N-pentafluorosulphanyl sulphurmonofluoride imides (Rt - CF 3 (1a) , t-C 3 F 7 (1b)) are prepared by the reaction of NSF 3 with appropriate sulphurtrifluoride derivatives. The fluorine bonded to sulphur(IV) in 1a and 1b is substituted by PCl 5 to give sulphurmonochloride imides (Rt = CF 3 (2a), i-C 3 F 7 (2b)). The chlorine in 2a and 2b can be exchanged by reaction with suitable silver(I) and mercury(II) salts.

A series of organorhodium and -iridium complexes M(R)(CO)(PPh 3 ) 2 (M = Rh: R = C 6 H 5 , 2-MeC 6 H 4 , 4-MeC 6 H 4 , 2,4,6-Me 3 C 6 H 2 , CH 3 , CH 2 SiMe 3 , CH 2 CMe 3 ; M = Ir: R = CH 3 , CH 2 Ph, CH 2 SiMe 3 , CH 2 CMe 3 ) has been prepared from MCl(CO)(PPh 3 ) 2 and the corresponding organolithium or Grignard reagents. Of these compounds, the mesitylrhodium complex Rh(2,4,6-Me 3 C 6 H 2 )(CO)(PPh 3 ) 2 as well as the iridium and rhodium alkyls with Me 3 SiCH 2 and Me 3 CCH 2 ligands show cis,trans-isomerism which is demonstrated on the basis of infrared and NMR spectroscopic evidence.

The synthesis of the ureadiido compounds M′[M(CO)nL] (1-5; M′ = Li, K; M = Mn, Re; n = 5,4), in which the ureadiide ions act as monodentate and bidentate ligands, resp., is described. The force constants of the CO-stretching vibrations are calculated and the σ-donor and π-acceptor properties of ureadiide ligands are discussed.

Carbonyl complexes of chromium, molybdenum and tungsten of the type DAD M(CO) 4 with DAD - diazadiene (R-N=CR′-CR′=NR) are shown by cyclic voltammetry to undergo electron transfer reactions to [DAD M(CO) 4 ] + and [DAD M(CO)4] - . The rate of subsequent chemical reactions with nucleophiles or by loss of ligands depend on the sol-vent, the metal and the ligands' electronic and steric properties. Chromium(+I) is more readily stabilized than Mo(+I) or W(-I) while the opposite is true for the stability of the anions formed. The dimerisation of a low-coordinate species DAD Mo(CO) 3 from the reduction of DAD Mo(CO) 3 (CH 3 CN) is detected electrochemically. The stabilization of oxidation states +1 and -I is briefly discussed in view of the DAD ligand properties.

The preparation and structural characterization of phosphinomethylthioethernickel(II) complexes of the general type [NiX 2 (Ph 2 PCH 2 SR) 2 ] (X = CI, Br, I, NCS: R = Me, Ph) are reported. In all the complexes the phosphinomethylthioethers act as monodentate ligands coordinating via the phosphorus atom. The isothiocyanate complexes are diamagnetic both in solution and in the solid state and have been assigned trans-planar configuration. As shown by magnetic measurements and by electronic spectroscopy, the halo complexes exhibit a square-planar (diamagnetic) ⇄ distorted-tetrahedral (paramagnetic) equilibrium in solution, while in the solid state the complexes are either square-planar or distorted-tetrahedral. For the complex [NiBr 2 (Ph 2 PCH 2 SMe) 2 ] both isomers have been isolated in the solid state.

The synthesis of bis[diphenylchalcogenide-2,2′-diolate(2-)]-cobaltate(II) compounds is described. In these complexes diphenyloxide-2,2′-diolate acts as a bidentate, diphenylsulfide- 2,2′-diolate as a tridentate chelating ligand leading to tetrahedral or octahedral coordinated cobalt(II), resp. An X-ray analysis of sodium bis[diphenylsulfide-2,2′-diolate(2-)]cobaltate(II)-acetonewater (1/2/1) shows the ligands to occupy fac-, their sulfur atoms cis-positions. The Co-0 distances (average 204.5 pm) are in the normal range while the C-S distances (average 248.5 pm) are longer than usually found indicating weaker bonds to sulfur than to oxygen.

The coordination properties of Ph 2 PEt (pi) and (Ph 2 PCH 2 CH 2 ) 2 PCH 2 CH 2 P(CH 2 CH 2 PPh 2 ) 2 (P 2 P 4 ) towards HV(CO) 6 and [V(CO) 6 ] - are compared. Preparation and spectral properties (IR, 1 H, 31 P and 51 V NMR) are described for the complexes HV(CO) 4 (p 1 ) 2 , [Et 4 N][V(CO) 6-n (p 1 ) n ] (n = 1, 2), HY(CO) m P 2 P 4 (m = 1-5) and [Et 4 N][V(CO) mP 2 P 4 ] (M = 1-3). The anionic species are obtained by photo-induced CO exchange, the hydrido complexes by treatment of the anionic complexes with t-BUCl/H 2 O or - more conveniently - by ion exchange on silica gel (m - 1-3) and subsequent UY irradiation (m = 4, 5). Complexes containing four CO groups are cis-configurated, the p 1 species being extremely labile. Trisubstitution yields an isomeric mixture of mer- and fac-[V(CO) 3 p 2 p 4 ] - . A consistent explanation of the 1 H pattern in the hydride region is possible on the basis of a facecapped octahedral structure with a restricted dynamic behaviour. The positions of the CO ligands in HV(CO) 3 p 2 p 4 and HV(CO) 2 P 2 P 4 are facial and trans, respectively. Only chelate five-ring structures are formed.

Extensive quantum mechanical calculations on the unrestricted MINDO/3 level reveal that for some ionised carbonic acids the energetically most feasible pathway for uni-molecular C-C cleavage cannot be described as being a one-step process. In complete agreement with experimental results the computational data are consistent with an inter-pretation of the reaction as being a two-step process, in which the reaction commences with a hydrogen migration from a CH-bond onto the ionised C = 0 group. The dissociation is completed with a radical induced C-C cleavage thus generating quite stable protonated unsaturated carbonic acids. Whereas the MINDO/3 results clearly show that the two-step process is energetically favoured over the direct C-C cleavage, this computational method fails badly in explaining the experimentally established fact that in the two-step sequence the hydrogen migration is the rate-determining step. This failure is due to the MINDO/3 inherent weakness of overestimating the stability of cyclic ions, e.g. cyclic transition states as they are formed in the course of the hydrogen migration step. Single point ab initio calculations carried out on the 4-31G level substantiate this interpretation in that the transition state for the hydrogen migration is calculated to lie substantially higher than that for the actual C-C dissociation step, but is still much lower than that calculated for a direct simple bond cleavage process of the respective cation radical.

Depending upon the molar ratio of the educts and the reaction conditions used, hexa-fluoroacetone azine (1) reacts with N,N-dialkyl-cyanamides (2) to give 3,4,6-triazaocta-2,4,6-trienes (6) and/or 4,4-bis(trifluoromethyl)-1,4-dihydro-1,3,5-triazines (7). Cyclo-addition reactions of 6 with tert-butyl isocyanide and 1-diethylamino(propine) are de-scribed. IR, 1 H, 19 F, and 13 C NMR data of the new compounds are discussed.

Pulse radiolysis experiments monitoring optical absorbance as well as conductivity and in-situ ESR radiolysis studies show that the OH radical reacts with the enol (k=8.6 x 10 9 M -1 s -1 ) and the enolate (k = 7.4 X 10 9 M -1 s -1 ) forms of acetylacetone by addition to the C = C double bond in aqueous N 2 O saturated solution. The OH reaction with enol leads to equal amounts of two radicals, CH 3 COCHOHCOHCH 3 (2) and CH 3 COCHC(OH) 2 CH 3 (4), as determined by scavenger reactions. At pH less than 1 the radical CH 3 COCHCOCH 3 (1) is observed by ESR spectroscopy showing that radical 2 and/or 4 eliminate water by proton catalyzed reactions. Under alkaline condition the OH adducts to the enolate eliminate OH -with rate constants larger than 10 5 s -1 leading to radical 1. G(OH - ) is determined to be 5.6 showing that addition is the main reaction of OH with enolate. To a much smaller degree the OH radical is proposed to abstract an H atom from that CH 3 group which is attached to the C -C double bond in enol and enolate, producing substituted allyl radicals which absorb in the visible region. The reaction of OH with the keto form has not been observed indicating that the rate constant of this reaction is significantly smaller than those with enol and enolate.

The preparation of various 1-substituted 4,4,4-Trichloro-2-bromo-butanes by photo-addition of bromotrichloromethane to allylic systems is described. Generally a more uniform product and a higher yield are obtained by this photoaddition than by the corresponding chemically initiated radical chain reaction.

Colorless alkylmolybdates(VI) of composition R-MoO 3 -are generated in aqueous solutions by the alkaline hydrolysis of complexes R-Mo(Bpy)(0) 2 Br(Bpy = 2,2′-bipyridyl, R = CH 3 and higher alkyl). At room temperature in alkaline aqueous solution, the new organometallic derivatives of oxomolybdate(VI) are remarkably resistant against Mo-C bond hydrolysis. Decomposition occurs more rapidly on heating, affording unrearranged alkanes according to the eq.: R-MoO 3 - + OH - →RH + Mo04=. In acidic solutions, the methylmolybdate(VI) species decomposes with the formation of a mixture of methane and ethane while higher alkylmolybdates carrying hydrogen in the β-position relative to molybdenum undergo Mo-C bond heterolysis by way of β-elimina-tion: R-CH 2 CH 2 -MoO 3 → Mo +4 (aq) + H + + R-CH = CH 2 . The Mo-C bond of alkylmolybdates is resistant to oxidants but is very sensitive to cleavage under reducing conditions. Reductive Mo-C bond cleavage occurs particularly rapidly in the presence of thiols and reduced ferredoxin model compounds. The latter reactions simulate the terminal steps of hydrocarbon producing reactions of nitrogenase with alternate substrates such as CN-, R-CN or R-NC, confirming previous mechanistic conclusions concerning the mechanism of nitrogenase action.

Evidence is produced to the effect that in mass spectrometry a quasi-thermal retro-Diels-Alder decomposition does not occur. This reaction has to be triggered by the positive charge in the molecule.

The title compounds were prepared by chemical vapour transport. They crystallize in the space group P3̅m 1 with the lattice parameters a = 7.532(3) (7.589(5)) and c = 36.54(2) (36.70(5))!. X-ray powder diffraction data are listed and the T,x phase diagram of the system AlInS 3 -In 2 S 3 is shown.

Secondary and tertiary alcohols are converted cleanly to the parent hydrocarbons in the gas phase with H 2 in the presence of a Ni/Al 2 O 3 catalyst at 190 °C. Primary alcohols are de-hydroxymethylated; e.g., 1-hydroxymethylada-mantane (4) gives adamantane (1). Alumina alone, in the absence of Ni, results in the formation of homoadamantane (5) from 4.