Volume 48, Issue 3

Sulfur diimides R 1 (NSN)R 2 (1) with different substituents R 1 and/or R 2 or with functional groups react with hexachlorodisilane (2) or octachlorotrisilane (3) to give the corresponding diaminosulfanes (4, 5) in quantitative yield. The formation of cyclic intermediates prior to the redox process is discussed. The products have been characterized by 1 H, 13 C, 15 N and 29 Si NMR in solution as well as by 15 N and 29 Si CP/MAS NMR in the solid state (4a, 4f). The crystal structure of ClMe 2 Si(Cl 3 Si)NSN(SiCl 3 )SiMe 2 Cl (4f) has been determined: space group PĪ (no. 2) with a = 864.2(2), b = 1096.8(2), c = 1232.7(2) pm and Z = 2.

Bromotriphenylphosphonium tribromide, [(C 6 H 5 ) 3 PBr]Br 3 , has been prepared by the reaction of triphenylphosphine with bromine in dichloromethane. Light-brown crystals are obtained by recrystallization from the same solvent. The crystal and molecular structure of the title compound has been determined. The crystals are monoclinic, space group P2 1 /c, Z = 8; a = 1917.1(8), b = 1182.2(9), c = 1823.5(4) pm, β = 108.34(2)°. R = 0.056 (R w = 0.063) for 1813 reflections with I ≥ 3σ(I). In the solid state the title compound exists as discrete monomeric (C 6 H 5 ) 3 PBr+ and Br 3 ⁻ ions with two crystallographically independent ions of each sort. The cations have a slightly irregular tetrahedral geometry around the P atom. The tribromide anions are nearly symmetrical and slightly bent.

The disilanol (CMe 3 ) 2 Si(OH) 2 (1) serves as a starting material in the reaction with C 4 H 9 Li and sodium for the construction of the alkali derivatives 2,3,4, and the siloxanes 5,6,7,8. The six-membered cyclosiloxane 10 and the spirocyclic compound 11 are easily prepared in the reaction of [(Me 3 C) 2 Si(OH)] 2 O (8) with 2C 4 H 9 Li and SiF 4 or SnBr 4 . The crystal structures of (Me 3 C) 2 Si(OLi) 2 (3), (Me 3 C) 2 Si(ONa)OH (4), and (Me 3 C) 2 Si(ONa)OSiF(Me 3 C) 2 (9) have been determined and are discussed.

A cobalt(III) complex with pyruvylglycine oxime (H 3 G) of composition Na 3 [CoG 2 ] · 9 H 2 O is synthesized and investigated by means of X-ray analysis, infrared, electronic and NMR spectroscopy. The crystals are triclinic, space group P1̄, a = 15.477(5), b = 9.931(4), c = 7.773(4)Å; α = 75.60(3); β = 82.86(4); γ = 93.54(3)°; Ζ = 2. The structure was refined to final R = 0.036 for 3347 independent observed reflections. The structure consists of the complex anions, Na + cations and water molecules. The ligands are coordinated via the deprotonated oxime and amide nitrogen and the carboxyl oxygen atoms in a meridional fashion (Co—O(carboxyl) = 1.971 and 1.947 Å; Co— N(oxime) = 1.891 and 1.909; Co— N(amide) = 1.876 and 1.866Å). The Co(III) coordination octahedron is slightly distorted; the Co—O and Co—N distances are in agreement with the data for oxime and peptide complexes of Co(III). The unit cell contains 2 enantiomeric complex anions related by a center of symmetry. The electronic, IR and NMR ( 1 H and 13 C) spectra of the complex are compared to those of the free ligand and of dipeptidato complexes of Co(III).

Aquacopper(II) glycyl-β-alaninate (1) and aquacopper(II)-β-alanylglycinate (2) were obtained from CuCO 3 and the appropriate dipeptide under reflux in water. 2 crystallizes in the orthorhombic space group Pna2 I . The lattice constants (291 K) are: a = 8.984(2), b = 12.456(2), c = 6.978(2) Å. The dipeptide anion, acting as a tridentate ONN ligand, and one oxygen atom of the carboxylate group of a neighbouring molecule form the base of a square pyramid around Cu, with water in the apical position. Cu is found slightly above the base. The molecules are connected by bridging carboxylate groups to form chains which are linked by hydrogen bonds between the water molecule and the oxygen atom of the peptide group.

Complexes obtained from CrCl 3 Py 3 with some optically active α-hydroxy acids have been characterized by elemental analysis, magnetic susceptibility, vibrational (IR), electronic and circular dichroism (CD) spectra. The magnetic susceptibility data are close to the spin-only value for a d 3 chromium(III) ion in octahedral or distorted octahedral symmetry. Three (Cr—Cl) vibrational modes in the region 410-290 cm -1 are observed for some of the complexes indicating C 2ν , local symmetry of ligand atoms around the chromium(III). In the electronic spectra two peaks are observed in the range 16949-18018 and 22986-24570 cm -1 . They are assigned to d—d transitions in pseudo octahedral symmetry. The structure of the complexes is likely to be facial since strong and well defined Cotton effects are observed. The parameters (D q , B, β 35 ) for the complexes provide reassurance that pyridine nitrogen is preserved.

[{(CO) 4 Co} 2 SnCl 2 ] reacts with silylated chalcogens E(SiMe 3 ) 2 (E = S, Se) to form the compounds [{(CO) 4 Co}4Sn 2 E 2 ] (E = S (1), Se (2)). According to crystal structure determinations 1 and 2 contain planar Sn 2 E 2 rings. The Sn atoms are coordinated nearly tetrahedrally by two bridging chalcogen atoms and two {(CO) 4 Co} groups.

The diamagnetic tetranuclear cluster complexes Mo 3 CuS 4 I(R 2 PS 2 ) 4 •C 5 H 5 N 2 (a: R=Et, b: R=Pr) are obtained by reaction of Mo 3 S 4 L 4 (L = R 2 PS 2- ) 1 with CuI and pyridine. Each Mo atom of the cubane-type Mo 3 CuS 4 core is chelated by L. Two of the Mo atoms are bridged by the fourth L, while a pyridine ligand completes the coordination sphere of the third Mo atom, and iodine is bonded to the Cu atom. Magnetic, NMR- and MS-spectroscopic data are given. 2b crystallizes in the monoclinic space group P2 1 /n with Z = 4 and lattice parameters a = 21,164(7), b = 10,653(3), c = 25,455(8)Å, and β = 106,25(3)°.

Tetraphenylcyclopentadiene (1) reacts with acylchlorides RC(O)Cl (R = CH 3 , C 3 H 7 , C 5 H 11 ,C 7 H 15 ) to form the corresponding [(cyclopentadiene tetrayl)tetrakis] (4,1-phenylene)alkanones C 5 H 2 (C 6 H 4 C(O)R-4) 4 (2a, 2b, 2c and 2d). 2a reacts with NaNH 2 generating the corresponding sodium salt Na[C 5 H(C 6 H 4 C(O)R-4) 4 ] (3a). 2a, 2b, 2c, and 2d react with T1OC 2 H 5 yielding the thallium(I) derivatives Tl[C 5 H(C 6 H 4 C(O)R-4) 4 ] (4a, 4b, 4c, 4d). Octaphenylferrocene (5) reacts with acylchlorides RC(O)Cl (R = CH 3 , C 3 H 7 , C 5 H 11 , C 7 H 15 ) to form octaacylated ferrocenes Fe[C 5 H(C 6 H 4 C(O)R-4) 4 ] 2 (6a, 6b, 6c and 6d). 6a can also be prepared by reacting FeI 2 with 3a. 6a reacts with NaOBr yielding Fe[C 5 H(C 6 H 4 C(O)OH-4) 4 ] 2 (7), which after reaction with C 5 H 11 OH and C 7 H 15 OH gives the corresponding octaesters Fe[C 5 H(C 6 H 4 C(O)OR-4) 4 ] 2 (8c and 8d). 6a and 6b are reduced by N 2 H 4 (H 2 O) to give Fe[C 5 H(C 6 H 4 CH 2 R-4) 4 ] 2 (11a and 11b). The X-ray crystal structures of tetraphenylcyclopentadiene (2 a), as well as of the partially and totally substituted ferrocene derivatives Fe[C 5 H(C 6 H 4 C(O)CH 3 -4) 4 ][C 5 H(C 6 H 4 C(O)CH 3 -4) 3 (C 6 H 5 )] (9), Fe[C 5 H(C 6 H 4 C(O)C 3 H 7 -4)(C 6 H 5 ) 3 ] 2 (10) and Fe[C 5 H(C 6 H 4 C 4 H 9 -4) 4 ] 2 (11b) have been determined. The 1 H and 13 C NMR spectra of the new compounds are reported and discussed.

μ-Oxo-bis[N ,N '-o-phenylene-di(salicylaldiminato)iron(III)] was synthesized in dioxane solvent and its crystal structure determined. [C 2 OH 14 N ,OiFe]-,O · (C 4 H 8 O 2 ), monoclinic, space group P2 1 / c ,a = 14.650(2), b = 18.990(1), c = 13.296(1) Å, β = 76.080(7), V = 3590.3 Å 3 , Z = 4. Two iron (III) atoms in square pyramidal pentacoordination are bridged by an oxygen atom with an Fe - O - Fe angle of 145 and a Fe-Fe distance of 3.409(1) Å. The iron (III) centers are antiferrommagnetically coupled (J = -9 8 .5 cm -1 ), as derived from temperature-dependent magnetic susceptibility measurements in the range 4.2 to 286.5 K.

The 1-amino-2-neopentylsilenes 5-8 are formed in the reaction of Li t Bu with the aminovinylsilanes 1-4 in n-pentane (addition of Li t Bu to the vinylic double bond with subsequent 1,2-elimination of LiCl). The α-Li adducts initially formed are trapped by Me 3 SiOSO 2 CF 3 to yield α-SiMe 3 -silanes. The silenes undergo insertion reactions into the Si—O bond of Me 3 SiOMe. In the absence of any trapping reagent dimerization occurs. One of the 1,3-disilacyclobutanes thus formed (15) could be examined by X-ray diffraction. Reacting with 1,3-butadienes the chlorosubstituted silenes 5 and 8 yield [2 + 2]-cycloaddition products. With 1,3-cyclohexadiene Diels-Alder adducts are also obtained, but with cyclopentadiene the [4+2] adducts are formed exclusively. Products of an ene-reaction are observed upon treatment of 2,5-norbornadiene with the silenes 5 and 8. The methylsubstituted silene 6 does not undergo any cycloaddition reaction at all, while from silene 7 only traces of the cycloadducts are produced. Both species mainly yield the dimers. The preference for the [2+2] reaction type, exhibited by the silenes 5 and 8, is due to their polarity. The almost complete absence or low yield of any cycloaddition products from 6 or 7 can be correlated with the energy levels of their frontier molecular orbitals. The distribution of the disilacyclobutanes and cycloaddition product isomers is explained by the characteristics of the stereospecifically Ε-configurated silenes. The product distribution can also be rationalized considering the ambiphilic nature of the system ViRR′SiCl/Li 1 Bu.

The reaction of 1,3-dimethyl-1,3-diaza-2-chloro-5,6-benzo-1,3,2-phosphorinan-4-one 1 with N-trimethylsilylacetamide 2 and 2-methylpiperidine hydrochloride furnished the P-substituted derivatives 3 and 4. The reaction of 1 with trimethylbromo- and trimethyliodosilane yielded the 2-bromo- and 2-iodo- substituted compounds 5 and 6. 1-Methyl-3-(2-chloroethyl)-1,3-diaza-2-chloro-5,6-benzo-1,3,2-phosphorinan-4-one 8 was prepared in the reaction of N-methyl-N'-(2-chloroethyl)-anthranilamide 7 with phosphorus trichloride. The reaction of 8 with N-trifluoromethyl-3-nitrophenylamine 9 or with sodium fluoride led to the 2-fluorosubstituted product 11. From the unusual reaction of 8 with 9 in the presence of triethylamine N-difluoromethylene-3-nitrophenylimine 10 and the intermediate product, triethylamine hydrofluoride, were isolated. A mechanism of formation of 11 is proposed. The reaction of 8 with N-trimethylsilylacetamide 2 and bis-2-chloroethylamine hydrochloride furnished the expected substitution products 14 and 15, involving the 5,6-benzo-1,3,2-phosphorinan-4-one ring system. The characterization of 3-6, 8, 11, 14 and 15 rests, especially, on their 1 H-, 13 Cand 31 P-NMR spectra, and their mass spectra.

The synthesis of the triphenylmethyl-phosphonic and -phosphonothioic dihalides Ph 3 CP(:X)Y 2 (X = O, S; Y = F, Cl) is described. The NMR parameters of these compounds are discussed and compared to these of other phosphonic and thiophosphonic dihalides. Single crystal X-ray analysis was used to confirm the structure of Ph 3 CP(:O)F 2 2 [C2/c, a = 1599.6(4), b = 1096.3(3), c = 1863.1(7) pm, ß = 109.11(2)°, T = 178 K, R = 0.034]. The geometry at the phosphorus atom is approximately tetrahedral. The bonds between phosphorus and fluorine are extremely short [P— F 153.1(1) and 153.3(1) pm]. Bond distances and angles for this compound are compared to those of methylphosphonic difluoride which were obtained from microwave spectra.

By 103 Rh and 15 N NMR spectroscopy eight bond isomers of the preparatively feasible system [Rh(NCS) n (SCN) 6-n ] 3- , n = 0-4, including the three pairs of stereoisomers for n = 2,3,4 are identified and assigned unequivocally by their clearly resolved signals. A downfield shift of approximately 540 ppm per isomerization step from S bonding to N bonding is observed in the 103 Rh spectra. The non-separable stereoisomers exhibit a high field shift of 4-30 ppm of the trans/mer as compared to the cis/fac isomers. The spectra of the 99% isotopically 15 N enriched bond isomers reveal splittings of the 103 Rh signals into the expected multiplets with 1 J(RhN) couplings of about 23 Hz, which are confirmed and determined more precisely to 21,0 Hz for SRhN axes and 24,1 Hz for NRhN axes from the 15 N spectra. The 15 N resonances are observed in three characteristic regions depending on the bond type of the ambident ligands and their geometrical arrangement. For S bonding the signals appear at lowest field between — 134 and —141 ppm, for N bonding in asymmetric axes NRhS between —269 and —271 ppm, and in symmetric axes NRhN at highest field between —292 and —297 ppm. Some signals in the S bonding region are split by a very small 3 J(RhN) coupling of about 0,7 Hz.

The complex cation [tripod Co η 2 -(NH 2 O)] + , 2, (tripod = CH 3 C(CH 2 PPh 2 ) 3 ) containing an η 2 -coordinated NH 2 O − -ligand is an isoelectronic equivalent to the recently reported complex [tripod Co η 2 -(Ν 2 Η 3 )] + , 1, which contains side-on coordinated N 2 H 3 − [1,4]. The structures of the two cations 1 and 2 are almost superimposable. The structural discrimination between the NH 2 - and O- parts of the η 2 -NH 2 O - -ligand in 2 has been corroborated by the synthesis and X-ray analysis of the cations [tripod Co η 2 -(NMe 2 O)] + , 3, and [tripod Co Cl (NH 2 OMe)] + , 4. The hydroxylamido(1–) compound 2 upon treatment with air transforms into the nitrosyl compound [tripod Co (NO)], 5, the structure of which has also been determined.

The preparation of the daphnane prototype polyfunctional diterpene resiniferonol from resiniferatoxin (1) contained in latex from Euphorbia unispina or E. poisonii was modified to convert in an `early’ fraction of the acetone extract the extremely irritant 1 to the much less irritant 9,13,14-ortho(phenylacetate) 2 by transesterification. 2 was obtained in good yields and can be handled conveniently to prepare resiniferonol as reported previously. By esterification of resiniferonol with homologous straight chain aliphatic acids from C 2 to C 18 resiniferonol-14,20-diacylates were prepared. Treatment of the diacylates with perchloric acid/methanol yielded by intramolecular formation of the orthoester function the corresponding 9,13,14-orthoester-20-acylates. They were cleaved selectively by base catalysed transesterification to obtain the resiniferonol-9,13,14-orthoacetate (3), -hexanoate (4), -decanoate (5), -tetradecanoate (6) and -octadecanoate (7). On the mouse ear, unexpectedly they exhibit only weak irritant activity and on the mouse back skin practically no tumor promoting activity.

Novel microheterogeneous systems for the direct photoreduction of water using visible light in analogy to the photochemical reaction center of Rhodopseudomonas viridis are described in detail. These physical model systems for photosynthesis feature the recently synthesized bisheteroleptic metal complexes [Ru(bpy) 2 (PP)]Cl 2 , [Ru(bpy) 2 (PPB)]Cl 2 , [Ru(bpy) 2 (PPB-pCl)]Cl 2 and [Ru(bpy) 3 ]Cl 2 , adsorbed on a negatively charged SiO 2 —TiO 2 -colloid, the zwitterionic electron relay PVS and a long-term stable and highly efficient TiO 2 —Pt-“antenna” catalyst as well as TEOA as sacrificial electron donor. Evidence for the directed absorption of the sensitizers on the SiO 2 —TiO 2 -colloid is taken from UV-VIS-measurements, steady-state luminescence-spectroscopy and the quantum yields for PVS-reduction. The hydrogen production in the presence of the SiO 2 —TiO 2 -colloid is clearly enhanced and proofs the validity of the underlying concept of physical model systems for photosynthesis.

Benzoquinones such as primin (2-methoxy-6-pentyl-1,4-benzoquinone) from Primula obconica HANCE (Primulaceae) are known to be strong sensitizers and thus the source of severe allergic contact dermatitis (cell-mediated type of allergy). In order to determine the relationship between sensitizing capacity and chemical structure the synthesis of 19 side-chain-modified analogues of primin was carried out. With each of these primin derivatives 10 guinea pigs were sensitized using a modified FCA-method (FCA = Freund’s complete adjuvant). Elicitation was done open epicutaneously with 0.001 molar concentrations. In these sensitization experiments 2-methoxy-6-alkyl-1,4-benzoquinones (chain length C 1 -C 15 ) showed ascending sensitizing potency with increasing number of the side chain carbon atoms reaching maximum activity at an alkyl chain of 10 to 11 carbons. Beyond this point a decrease of the sensitizing potency in correlation with a further prolongation of the side chain was observed.

Potassium bishydridobis(tetrazol-1-yl)borate (1) has been synthesized from KBH 4 and tetrazole and characterized spectroscopically. Its crystal structure has been determined. 1 crystallizes in the monoclinic space group P2 1 /n with a = 537.8(2), b = 1703.5(9), c = 919.6(3) pm, β = 106.12(3)° and V = 809.4(6)· 10 6 pm 3 .

The ion pair [Hg(cyclam)] 2+ [Co(CO) 4 ]- displays a Co(–I) to Hg(II) metal-to-metal charge transfer (MMCT) band at 288 nm. Upon MMCT excitation the ion pair undergoes a photoconversion to [HgCO 2 (CO) 8 ].