Volume 41, Issue 12

BaC 4 O 4 -3H 2 O was prepared by crystallization in aqueous silica gel. The crystal structure is a complicated three-dimensional framework. Ba 2+ has CN 8+1. It is surrounded by 5 water molecules and 4 O squarate atoms (Ba-O distances from 271.1 to 324.2 pm). The squarate dianion is almost planar and shows C -C and C-O bond lengths indicating the existence of resonance stabilization, although one Osquarate atom is not connected to Ba 2+ at all. Short water-O squarate distances hint to strong hydrogen bonding which obviously plays an important part in this structure.

In SrC 4 O 4 -3H 2 O (type I), Sr 2+ has CN 8. It is surrounded by 3 water molecules and 5 oxygen atoms of 4 different squarate dianions. The C-O and C-C bond lengths are typical of extensive delocalization of the π-electron system. The connection of Sr 2+ and C 4 O 4 2- leads to infinite layers, obviously interlinked by hydrogen bonding. The oxygens of the squarate behave differently: two are Sr-chelating, but simultaneously bound to two additional Sr 2+ , one is connected with one Sr 2+ only, and the fourth is not bound to any Sr 2+ . The single crystal character remained in principle unchanged during dehydration to SrC 4 O 4 · 1 H 2 O and subsequent rehydration to the trihydrate. Grinding of a crystal treated in this way led to a new modification of SrC 4 O 4 ·3 H 2 O.

BaC 6 X 2 O 4 · 3H 2 O (X = Cl, Br) crystallizes in the orthorhombic space group Cmca. 4 of the 8 oxygen atoms around Ba 2+ belong to two different dianions, chelating Ba 2+ . In this way 1-dimensional corrugated chains are formed, interlinked by two oxygen atoms of neighbouring chains, thus forming layers. This interconnection is of polar character within a layer. The in­terlinking oxygen atoms have one carbon- and two Ba 2+ neighbours. CN 8 is completed by two water molecules. The latter and a further water molecule situated between the layers may be removed reversibly in a topochemical reaction without destruction of the structure.

The isotypic compounds Na 2 (H 2 O) 24 [M 2 (C 6 H 2 O 4 ) 3 ] (M = Mn 2+ , Cd 2+ ) form infinite net-like layers. The transition metal ion is coordinated octahedrally. The dianion of 2,5-dihydroxy-1.4- benzoquinone, consisting of two allyl systems interlinked by two long C-C distances (152-153 pm), acts as a chelating ligand. Adjacent layers are connected by hydrogen bonds. The stacking sequence of these layers, ···AAA···, leads to channels, which are filled by hydrated Na + ions. The Na + ions are coordinated in a distorted octahedral fashion, with neighbouring octahedra sharing common faces.

The reaction of W 2 (NMe 2 ) 6 with hexafluoroacetone (HFA) yields W 2 [OC(CF 3 ) 2 NMe 2 ] 2 (NMe 2 ) 4 , an orange solid, which was characterized by mass spectra, 1 H, 13 C, 19 F NMR spectra and an X-ray structure analysis. The compound contains a W=W triple bond of 230.1(1) pm.

The phosphiniminato-substituted tungsten(VI) fluorides (PhpMe) 3 P=NWF 5 (2), [(PhpMe) 3 P=N] 2 WF 4 (3), (Me 3 P=N) 2 WF 4 (4) and [(t-buNH)Ph 2 P=N] 2 WF 4 (6) have been pre­pared from the corresponding SiMe 3 derivatives by reaction with WF 6 . The starting materials (PhpMe) 3 P = NSiMe 3 (1) and (t-buNH)Ph 2 P=NSiMe 3 (5) are obtained by the reaction of the phosphanes with Me 3 SiN 3 . The crystal structure of 4 shows that the cis isomer was formed. Although the molecular geometry of 4 is similar to that of (Ph 3 P=N) 2 WF 4 , some important differences are observed arising from the different electronic properties of the substituents.

Cs2K 2 Cd 3 O 5 has been prepared from mixtures of the binary oxides in a silver-tube (550 °C. 17 days). The unit cell is triclinic, P1̄ (a = 983.2, b = 918.0, c = 653.5 pm. α = 108.3°, β = 113.7°, γ = 99.9°. The crystal structure was refined to R = 5.9% and /? u = 5.8% (four-circle-diffractome­ter data, 2616 unique of 3359 measured reflexions). The Effective Coordination Numbers (ECoN) and the Madelung Part of Lattice Energy (MAPLE) are calculated and discussed.

Aqueous sodium polysulfide of composition in the range Na 2 S 2.0 to Na 2 S 4.6 undergoes autoxidation by either air or pure oxygen at temperatures of between 23 and 40 °C according to the equation [xxx] Iodometric determination, vibrational spectra and ion-pair chromatography showed that neither sulfate, sulfite nor polythionates are formed and that the sulfur precipitated consists of S 8 (≥ 99%).

Mg(SiMe 3 ) 2 · TMDAP was synthesized by reaction of Hg(SiMe 3 ) 2 with magnesium in 1,3-bis-(dimethylamino)propane/diethyl ether. The crystal structure of the compound was investigated.

Methods for the preparation of simple silaalkanes with a high content of silicon and hydrogen have been explored. Target molecules, like H 3 SiCH 2 SiH 3 and HC(SiH 3 ) 3 , may serve as precursor molecules for the production of photovoltaic elements through thermal or discharge (plasma) CVD processes. Among a variety of synthetic pathways, the reactions between HSiCl 3 and HCCl 3 in the presence of an amine (Benkeser reaction) and the direct synthesis from silicon and polychloromethanes proved most promising for large scale preparations. The CH 2 X 2 /KSiH 3 metathesis is most useful on the laboratory scale. - The Grignard synthesis was employed for partly methylated homologues, like H 3 SiCH 2 SiH 2 CH 3 , H 3 SiCH 2 SiH(CH 3 ) 2 , H 3 SiCH 2 Si(CH 3 ) 3 , and related molecules. The magnesium reduction of CHBr 3 /SiCl 4 and CHBr 3 /CH 3 SiCl 3 mixtures serves best for the preparation of HC(SiCl 3 ) 3 , which can be converted into HC(SiH 3 ) 3 using LiAlH 4 . Attempts to synthesize tetrasilylmethane via the same route, C(SiH 3 ) 4 , led only to the formation of HC(SiH 3 ) 3 .

(η 5 -C 5 H 5 ) 2 TiCl 2 reacts with P(CH 3 ) 2 (Si(CH 3 ) 3 ) to form the paramagnetic complex [(η 5 -C 5 H 5 ) 2 Ti(Cl)P(CH 3 ) 2 Si(CH 3 ) 3 ] (1). In 1 Ti is coordinated by two (η 5 -C 5 H 5 ), and a Cl-ligand. In addition Ti is bound to the P-atom of a P(CH 3 ) 2 (Si(CH 3 ) 3 ) ligand. Treatment of 1 with Na/Hg affords the dinuclear paramagnetic complex [Ti(η 5 -C 5 H 5 ) 2 (μ 2 -P(CH 3 ) 2 )] 2 (2). 2 contains two Ti(η 5 -C 5 H 5 ) 2 units. Each Ti is bound to the P-atoms of the μ 2 -P(CH 3 ) 2 -ligands. The Ti-Ti- contact (391.8 pm) does not correspond to metal-metal bonding.

At the transition metal sulfur center of [Ru(PPh 3 ) 2 dttd], (dud 2- = 2,3;8,9-dibenzo-1,4,7,10- tetrathiadecane( -2)), the substitution of one PPh 3 ligand by anions like N 3 - or CN - in CH 2 Cl 2 is always coupled with a chloromethylation of one thiolato S atom in dttd 2- yielding the [dttd-CH 2 Cl] - ligand; with N 3 - conversion of azido into cyano ligands takes place additionally. In the reaction of [Ru(PPh 3 ) 2 dttd] with covalent azides like Me 3 SiN 3 or HN 3 , the PPh 3 substitution is also coupled with the oxidation of Ru(II) to Ru(III). Thus [Ru(PPh 3 ) 2 dttd] on reaction with NEt 4 N 3 or NEt 4 CN in boiling CH 2 Cl 2 yields [Ru(PPh 3 )(L)(dttd-CH 2 Cl)], (L = N 3 - , CN - ), whereas with Me 3 SiN 3 or HN 3 in addition to [Ru(PPh 3 )(N 3 )(dttd-CH 2 Cl)] the paramagnetic (μ eff = 1.58 B.M.) [Ru(PPh 3 )(N 3 )(dttd)] is obtained. The very stable [Ru(PPh 3 )(CN)(dttd-CH 2 Cl)] forms deeply coloured adducts with H + as well as [CrCl 3 (THF) 3 ], AlCl 3 and BF 3 . With Mel it yields [Ru(PPh 3 )(CN)(Me-dttd-CH 2 Cl)]I. All compounds have been characterized by elemental analysis as well as spectroscopic means including ESCA; the structure of [Ru(PPh 3 )(CN)(dttd-CH 2 Cl)] has been solved by X-ray structure analysis.

In order to study the properties of sulfur coordinated transition metal centers. [MoCl 2 dttd] (dttd 2 = 2,3,8,9-dibenzo-1,4.7,10-tetrathiadecane(2-)) was reacted with NO in the presence of Zn. [Mo(NO) 2 dttd] was obtained whose X-ray structure analysis shows that Mo is coordinated pseudo-octahedrally by two trans thiolato S, two cis thioether S as well as two cis N atoms of nearly linear MoNO groups. With respect to its low v(NO) frequencies (1760/1665 cm -1 ) and quite normal bond lengths as well as angles [Mo(NO) 2 dttd] shows unexpectedly facile and rapid reactions with nucleophiles; with two equivalents of PR 3 (PMe 3 , PEt 3 , PMePh 2 , PEtPh 2 , PPh 3 ) it yields the corresponding phosphiniminato complexes [Mo(NO)(NPR 3 )dttd] and free phosphinoxides OPR 3 , respectively. Reaction mechanisms as well as the bonding situation in the [Mo(NPR 3 )] entity are discussed; on the basis of 95 Mo and 14 N NMR it is concluded that the conversion of NO into NPR 3 ligands includes a reduction of N(+2) to N(-3) as well as an oxidation of (formal) Mo(+2) to Mo(+3). With H 2 O the [Mo(NO)(NPR 3 )dttd] complexes hydro­lyze with loss of the NPR 3 ligands and formation of binuclear [Mo(NO)dttd] 2 . The ease of hydrolysis depends on the substituents R: In THF [Mo(NO)(NPMe 3 )dttd] hydrolyzes at 20 °C within a few minutes, [Mo(NO)(NPPh 3 )dttd], however, needs the addition of cone. HCl.

Trichlorostannatoplatinum(II) complexes containing bis(2-diphenylphosphinoethyl)phenyl- phosphine, etp, and the tripod ligand tris(2-diphenylphosphinoethyl)phosphine, PP 3 , respective­ly, have been prepared and characterized by 119 Sn{ 1 H} and 31 P{ 1 H} NMR spectroscopy. [(etp)PtCl](BPh 4 ) (1a) reacts with SnCl 2 via oxidative addition to give [(etp)PtSnCl 3 ](BPh 4 ) (1b). The 31 P NMR spectral patterns of type 1 complexes are consistent with AX 2 spin-systems and square planar structures in solution. There is 31 P NMR evidence that in the presence of (Ph 4 P)Cl 1b adds further SnCl 2 . The possibility of the formation of [(etp)Pt(SnCl 3 ) 2 ] (2) is discussed. [(PP 3 )PtCl](BPh 4 ) (3a) reacts with SnCl 2 to give [(PP 3 )PtSnCl 3 ](BPh 4 ) (3b). The 31 P NMR spec­tral patterns of 3a and 3b are consistent with AX 3 spin-systems and trigonal bipyramidal struc­tures.

Relationship between the steric conformation and the efficiency of energy transfer in binuclear zinc(II) porphyrin complexes was interpreted in terms of the absorption and fluorescence spectra.

α-H aloketones and α-halocarbonyl compounds are effectively reduced to dehalogenation to their corresponding parent ketones or carbonyl compounds in good yield by sodium borohydride and tin(II) chloride in tetrahydrofuran.

Two deoxynucleoside analogues, 1-(2-deoxy-β-D-ribofuranosyl)-2-oxo-4-imidazoline-4-carbox-amide (1) and 5-carbamoyl-2′-deoxyuridine (2), were synthesized and incorporated into decamer deoxynucleotides, which were hybridized to their complementary strands. The duplices in which 1 paired with A or G showed higher melting temperatures (Tm's) than those containing G -T or A -C mismatch, although lower than the Tm of intact totally complementary duplex. The incor­poration of 2 into a strand resulted in extreme destabilization of the duplex.

Partition coefficients of sixteen biologically important pyrimidines and purines between an organic phase and water have been determined and the best organic solvents for their extraction have been suggested.

In the course of pharmaco-chemical studies in the structure and activity relationship in harmaline series of β-carboline bases, a number of new derivatives of harmaline have been obtained and characterized through chemical and spectral studies. Pharmacological screening carried out on one of these (9) shows that it has mild physiological activity without any toxicity.

A nitronylnitroxide derivative of ferrocene has been prepared by interaction of ferrocene aldehyde with 2,3-bis(hydroxylamino)-2,3-dimethylbutane followed by oxidation with lead(IV ) oxide.

The structure of wrightiin, a depside metabolite of Erioderm a wrightii is shown by X-ray crystalo-graphy to be 2. The mass spectrum is anomalous.

A 3-step synthesis of 5-aminolevulinic acid is described.