Ferrocene compounds. XXXIX.

In the title compound, [Fe(C₅H₅)(C₁₄H₁₃O)], the plane of the heterocyclic ring is almost perpendicular to the plane of the substituted cyclo­penta­dienyl ring, and the heterocyclic ring adopts a half‐chair conformation. The conformation of the nearly parallel cyclo­penta­dienyl (Cp) rings [the dihedral angle between their planes is 2.7 (1)°] is almost halfway between eclipsed and staggered, and the rings are mutually twisted by about 19.4 (2)° (mean value). The mean lengths of the C—C bonds in the substituted and unsubstituted cyclo­penta­dienyl ring are 1.420 (2) and 1.406 (3) Å, respectively, and the Fe—C distances range from 2.029 (2) to 2.051 (2) Å. The phenyl and unsubstituted cyclo­penta­dienyl rings are involved in C—H⃛π interactions, with intermolecular H⃛centroid distances of 2.85 and 3.14 Å for C—H⃛π(Ph), and 2.88 Å for C—H⃛π(Cp). In two of these interactions, the C—H bond points towards one of the ring bonds rather than towards the ring centroid. In the crystal structure, the C—H⃛π interactions connect the mol­ecules into a three‐dimensional framework.     

Azinyl Sulfides. LXVII.

The title compound, C₆H₇NS, is planar, with endo‐C—N—C bond angles of 118.7 (2) and 118.8 (2)°, and C—S bond lengths of 1.697 (2) and 1.692 (2) Å for the two symmetrically independent mol­ecules. 1‐Methylpyridinium‐4‐thiol­ate is the major contributor to the molecular structure in the solid state.     

Overcrowding motifs in large PAHs. An ab initio study.

Planar and overcrowded LPAHs C(34)H(18) anthra[9,1,2-cde]benzo[rst]penaphene (1), benzo[rst]phenanthro[10,1,2-cde]pentaphene (2), tetrabenzo[a,cd,j,lm]perylene (3), tetrabenzo[a,cd,lm,o]perylene (4), and LPAHs C(38)H(18) anthra[2,1,9,8-klmno]naphtho[3,2,1,8,7-vwxyz]hexaphene (5), dianthra[2,1,9,8-stuva;2',1',9',8'-hijkl]pentacene (6), dibenzo[jk,uv]dinaphtho[2,1,8,7-defg;2',1',8',7'-opqr]perylene (7), diphenanthro[5,4,3-abcd;3',4',5'-lmno]perylene (8), potential products of peri-peri reductive couplings of benzanthrone and of naphthanthrone, respectively, were subjected to an ab initio study with emphasis on overcrowding motifs. The HF and DFT B3LYP methods were employed to calculate energies and geometries of the minima conformations of these LPAHs. The most stable LPAHs in these series were found to be planar C(2)(v)()-1 and C(2)(v)()-5, respectively. Among overcrowded LPAHs, twisted-folded C(2)-3 and C(2)-7 with two cove regions were found to be more stable than their respective isomers twisted-folded C(2)-4 and C(2)-8 with one fjord region each, in contrast to the semiempirical predictions. The energy differences between the most stable planar isomer and the overcrowded isomers were significantly smaller in the C(38)H(18) series, than in the C(34)H(18) series. Overcrowded twisted-folded C(2)-7 with two coves was found to be more stable than planar C(2)(h)()-6 by 2.0 kJ/mol (at B3LYP/6-311G), indicating enhanced role of aromatic stabilization and decreased destabilization due to overcrowding, with increasing the number of aromatic rings. Heats of formation of LPAHs 1-8 were derived from the ab initio total energies (at B3LYP/6-31G). A search of the conformational spaces of 3 and 4 revealed an anti-folded local minimum C(i)()-3 and a syn-folded transition state C(s)()-4, 23.7 and 120.3 kJ/mol higher in energy than the twisted-folded C(2)-3 and C(2)-4, respectively (at B3LYP/6-31G). The cove and fjord torsion angles in the C(38)H(18) series were found to be smaller than in the C(34)H(18) series. The nonbonding distances between carbon atoms at cove and fjord regions of the overcrowded LPAHs were found to be smaller than the sum of the van der Waals radii of two carbon atoms     

ICP-AES法测定菜头肾中多种微量元素

为探讨测定菜头肾中多种微量元素的方法,采用HNO3-HC lO4体系湿法消化,运用ICP-AES法测定了菜头肾中的多种微量元素。结果表明,菜头肾中K、Ca、Mg、P、S、A l、Na、Fe、Mn等元素含量相对较高,变异系数范围在0.23%~8.92%之间,元素的回收率在82.9%~106.1%之间。该法简便快速,可同时测定菜头肾中多种微量元素。     

珠子参化学成分分析

从珠子参根茎中分离得到7个化合物. 利用核磁共振、 质谱和红外等手段, 并结合其理化性质, 鉴定了其结构, 它们分别是24(R)-珠子参苷R1, 6-O-[β-D-吡喃葡萄糖基(1→2)-β-D-吡喃葡萄糖基]-20-O-[β-D-吡喃葡萄糖基(1→4)-β-D-吡喃葡萄糖基]-20(S)-原人参三醇、 6″-乙酰基-人参皂苷Rd、 人参皂苷Rf、 竹节参皂苷Ⅳa、 人参皂苷Rd和竹节参皂苷Ⅴ. 其中, 24(R)-珠子参苷R1和6-O-[β-D-吡喃葡萄糖基(1→2)-β-D-吡喃葡萄糖基]-20-O-[β-D-吡喃葡萄糖基(1→4)-β-D-吡喃葡萄糖基]-20(S)-原人参三醇为2个新化合物, 6″-乙酰基-人参皂苷Rd 和人参皂苷Rf为首次从珠子参根茎中得到.     

Conformational study of phosphoserine in aqueous solutions. II—1H n.m.r. results

The 270 MHz n.m.r. spectra of phosphoserine (PSer) have been measured and completely analysed for seven pD values. The resulting vicinal coupling constants ³J(HαHβ) and ³J(PHβ) are used to discuss the conformations of PSer with respect to the (Hα)? Cα? Cβ? (O) and (Cα)? Cβ? O? (P) bond axes. The all-trans conformer predominates for all pD values, with its fractional population being minimal at pD values close to neutrality. The Cβ? O bond rotamer populations agree reasonably well with those obtained from ¹³C investigations.     

Poly­sulfonyl­amines. CXLV.

The prominent features in the molecular structure of the title compound (alternative name: 2‐diethyl­carbamoyl‐1,1,3,3‐tetraoxo‐1,3,2‐benzodi­thia­zole), C₁₁H₁₄N₂O₅S₂, arise in the urea moiety S₂N—C(O)—N′C₂: the sum of the angles at N is 332.3 (1)°, the N—C(O)—N′C₂ unit is planar, and distances N—C(O) = 1.494 (3) Å, N′—C(O) = 1.325 (2) Å and C—O = 1.215 (2) Å. The mol­ecules are associated via five C—H?O hydrogen bonds to form layers parallel to the yz plane. This compound and its di­methyl homologue, which were synthesized by treating the silver salt of o‐benzene­disulfon­imide with carbamoyl chlorides, are prone to rapid hydro­lysis at the weak N—C(O) bond. For both mol­ecules, the rotational barrier about the partial N′—C(O) double bond is ca 50 kJ mol^?1 at 250 K (from dynamic ¹H NMR experiments).     

Photochemische Reaktionen. 87. Mitteilung. Zur Photolyse von 9-Oxabicyclo[3.3.1]nonan-2-on

Photolysis of Bicyclo[3.3.1]nonan-2-one. Disproportionations, the secondary processes available to the acyl-alkyl biradical b (X(9) = 0) formed from 9-oxabicyclo[3.3.1]-nonan-2-ones a (X(9) = 0) in a primary photochemical process by α-cleavage (Norrish type I cleavage) were studied. Special attention was paid to the selectivity between the two possible H-abstractions: the one at C(3) (→ ketene c , X(9)= 0) and the other one at C(8) (→ alkenal d , X(9) = 0) and to the selectivity of the H-abstraction at a definite methylene group (C(3) or C(8)). In the case of ketene formation (→ c , X(9) = 0) the specificity of the insertion of the migrating H-atom at C(1) was studied. endo-6-Hydroxy-9-oxabicyclo[3.3.1]nonan-2-one ( 6 ) and derivatives of it ( 7, 8, 16, 17, 19, 21, 30 and 38 ) as well as exo-6-hydroxy-9-oxabicyclo[3.3.1]-nonan-2-one ( 41 ) and its derivative 42 were used as substrates. UV.-irradiation of 6 in benzene yielded 1,5-dioxa-2-cis-decalone ( 44 ) by way of a ketene g (R = H) as demonstrated by the photolysis of 7 (→ 45 ), 8 (→ 43 ), and 17 (→ 47 ). Specific labellings with deuterium proved that H-abstraction occurs intramolecularly at C(3) (e.g. 16 → 54 ; 6 + 16 → 44 + 54 ), that one of the H-atoms at C(3) migrates specifically to C(1) ( 21 → 55 ; 19 → 56 ), endo-H–C(3) being favored by a factor of 6. The abstraction showed an unexpected primary isotope effect of about 2. UV-irradiation of 41 in benzene yielded in addition to the expected 1,5-dioxa-2-trans-clecalone ( 63 ) about 3% of an isomeric compound 67 which probably results from H-abstraction at C(8) (→ alkenal 65) followed by cyclisation.     

Multicomponent polyanions. 45. A multinuclear NMR study of vanadate(V)-oxalate complexes in aqueous solution.

The two complexes formed in the aqueous vanadooxalate system, V(Ox)- and V(Ox)2(3-), have been characterized using 51V, 13C and 17O NMR. For the V(Ox)2(3-) complex, two peaks are observed in 13C NMR and four in 17O NMR. This leads to the conclusion that each oxalate ligand has two different distances to the VO2 group. This fact, together with the peak integrals and the chemical shifts, indicates strongly that the hexacoordinate complex [VO2(C2O4)2]3- found in single-crystal X-ray structure determinations persists in aqueous solution. The dependence of the 13C NMR linewidths upon temperature reveals two types of dynamic processes: (1) a rearrangement in which the two different V-Oox switch places and (2) an exchange of the oxalate ligands in the [VO2(C2O4)2]3- complex with free oxalate, probably through a dissociative process. Rate constants and activation parameters for the two dynamic processes involving [VO2(C2O4)2]3- have been calculated from the shape of the 13C NMR signals. For the V(Ox)- complex, only one relatively narrow peak is obtained in 13C NMR and three peaks in 17O. This fact, as well as the relative positions of these peaks, is in accordance with a pentacoordinate complex [VO2(C2O4)H2O]-, where the two V-O distances to the oxalate ligand are equal. We also show that, in the pH range 0.8-6.6, there is no protonation of the studied complexes, in agreement with previous potentiometric results.     

Crystal structures of synthetic analgetics. V. Dextromoramide.

The molecular and crystal structure of dextromoramide has been determined by X-ray methods. The crystals are orthorhombic, space group P212121 with unit cell dimensions a = 9.720(4) A; b = 12.226(3) A; c = 18.381(3) A. The structure was determined by direct methods and the model refined to an R-value of 0.036 for 1788 observed reflections. The mean e.s.d.'s in bond lengths and angles are 0.004 A and 0.3, respectively. The morpholine moiety is nearly in antiposition relative to the quaternary carbon atom C6, the pertinent angle C6 - C7 - C9 - N2 being - 159.4. This conformation is similar to that previously reported for the bitartrate of the title compound. The pyrrolidine ring has the envelope conformation and the amide group is strictly planar. The conformation of some acyclic analgetics are discussed.     

BECKMANN-Umlagerung und Fragmentierung. II. Teil. Versuche zur 7-Zentren-Fragmentierung von γ-Aminoketoximen. Fragmentierungsreaktionen, 19. Mitteilung

The occurrence of so-called synchronous 7 -centre-fragmentation has been excluded for γ-amino-ketoxime derivatives N? C? C? C? C?N? X. Fragmentation may occur, however, by another route. Reaction rates of the p-toluenesulfonates of (4-quinuclidinyl)-methyl-ketoxime ( 10b ) and (3β-tropanyl)-methyl-ketoxime ( 14b ) in 80% ethanol and the resulting products have been determined. Whereas the latter γ-aminoketoxime underwent quantitative BECKMANN rearrangement to 3β-acetylaminotropane ( 29 ), the former yielded 3% fragmentation products besides rearranged 4-acetylamino-quinuclidine ( 13 ). A kinetic study reveals that both 10b and 14b react via the rearranged nitrilium ions 12a and 16a , respectively. In the case of the N-(4-quinuclidinyl)-acetonitrilium ion ( 12a ) 5-centre-fragmentation competes with hydration to the amide 13 .     

Synthesis of heparin saccharides III. Synthesis of derivatives of D-glucosamine as starting materials for disaccharides.

Derivatives of benzyl 2-[1-(benzyloxy)formamido]-2-deoxy-α-D-glucopyranoside with various protecting groups at C(3) (benzoyl, benzyl and N-phenylcarbamoyl) and C(6) (benzoyl, benzylsulfonyl, N-phenylcarbamoyl and tosyl) have been synthesized as starting materials for disaccharides. The C(4) and C(6) hydroxyl groups of the amino sugar were initially blocked by an acetal group. After introduction of the protecting group at C(3), the acetal group was removed by acid hydrolysis, and the C(6) hydroxyl group was selectively acylated or sulfonylated. The 3,6-di-O-benzoate has also been prepared by dimolar benzoylation of the amino sugar, whereby the 4,6-isomer was obtained as a by-product.     

Organotransition-Metal Metallacarboranes. 46. Multidecker Sandwiches of the Cobalt Group Metals(,)(1)

The double-decker sandwich complex CpIr(2,3-Et(2)C(2)B(4)H(4)) (1a) was prepared via deprotonation of nido-2,3-Et(2)C(2)B(4)H(6) to its mono- or dianion and reaction with (CpIrCl(2))(2) in THF and isolated as a colorless air-stable solid; the B(4)-chloro derivative 1b was also obtained. Decapitation of 1a and 1b with TMEDA afforded colorless nido-CpIr(2,3-Et(2)C(2)B(3)H(5)) (2a) and its 4-chloro derivative 2b. Chlorination of 1a by Cl(2) or N-chlorosuccinimide gave the symmetrical species CpIr(2,3-Et(2)C(2)B(4)H(3)-5-Cl) (1c), which was decapped to yield nido-CpIr(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (2c). The triple-decker complexes CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)IrCp (3), an orange solid, and dark green CpIr(2,3-Et(2)C(2)B(3)H(2)-4[6]-Cl)CoCp (5) were prepared from 2a and nido-CpCo(2,3-Et(2)C(2)B(3)H(5)) (4a), respectively, by deprotonation and reaction with (CpIrCl(2))(2) in THF. Reaction of the 2c(-) anion with Rh(MeCN)(3)Cl(3) gave the dark green tetradecker complex [CpIr(Et(2)C(2)B(3)H(2)-5-Cl)](2)RhH (6). In an attempt to prepare a heterotrimetallic Co-Rh-Ir tetradecker sandwich, a three-way reaction involving the deprotonated anions derived from CpCo(2,3-Et(2)C(2)B(3)H(4)-5-Cl) (4b) and 2c with Rh(MeCN)(3)Cl(3) was conducted. The desired species CpCo(Et(2)C(2)B(3)H(2)Cl)RhH(Et(2)C(2)B(3)H(2)Cl)IrCp (7) and the tetradeckers [CpCo(Et(2)C(2)B(3)H(2)Cl)](2)RhH (8) and 6 were isolated in small quantities from the product mixture; many other apparent triple-decker and tetradecker products were detected via mass spectroscopy but were not characterized. All new compounds were isolated via column or plate chromatography and characterized via NMR, UV-visible, and mass spectroscopy and by X-ray crystal structure determinations of 1a and 3. Crystal data for 1a: space group C2/c; a = 28.890(5) ?, b = 8.511(2) ?, c = 15.698(4) ?, beta = 107.61(2) degrees; Z = 8; R = 0.049 for 1404 independent reflections having I > 3sigma(I). Crystal data for 3: space group P2(1)/c; a = 11.775(4) ?, b = 15.546(5) ?, c = 15.500(5) ?, beta = 103.16(3) degrees; Z = 4; R = 0.066 for 2635 independent reflections having I > 3sigma(I).     

Contributions to reversed-phase column selectivity. I. Steric interaction

In reversed-phase chromatography (RPC), the restricted retention of "bulky" solutes can occur in one of two ways, giving rise to either "shape selectivity" or "steric interaction." Starting with data for 150 solutes and 167 monomeric type-B alkylsilica columns, the present study examines the steric interaction process further and compares it with shape selectivity. The dependence of column hydrophobicity and steric interaction on column properties (ligand length and concentration, pore diameter, end-capping) was determined and compared. The role of the solute in steric interaction was found to be primarily a function of solute molecular length, with longer solutes giving increased steric interaction. We find that there are several distinct differences in the way shape selectivity and steric interaction are affected by separation conditions and the nature of the sample. Of particular interest, steric interaction exhibits a maximum effect for monomeric C(18) columns, and becomes less important for either a C(1) or C(30) column; shape selectivity appears unimportant for monomeric C(1)-C(18) columns at ambient and higher temperatures, but becomes pronounced for C(30) - as well as polymeric columns with ligands ≥C(8). One hypothesis is that shape selectivity involves the presence or creation of cavities within the stationary phase that can accommodate a retained solute (a primarily enthalpic process), while steric interaction mainly makes greater use of spaces that pre-exist the retention of the solute (a primarily entropic process). The related dependence of hydrophobic interaction on column properties was also examined.     

Natural Abundance 13C-NMR. of Reduced Isoalloxazine

When an isoalloxazine derivative ( 1 ) was reduced ( 2 ) its ¹³C-NMR. resonances were all shifted upfield and the largest shifts were observed for C (4a), C(6) and C(8) but downfield shifts for C(2), C(4) and C(10a). The results and their biochemical implications are shortly discussed.     

Pheromones of insects and their analogs. XX. Methyl-branched pheromones based on 4-methyltetrahydropyran.

A synthesis is proposed of 4,8-dimethyldecanal (VIII) — a pheromone of the flour beetlesTribolium confusum andT. castaneum. By heating 71.2 g of 4-methyltetrahydropyran (I), 83.2 g of AcBr and 1.57 g of ZnCl₂ (45°C), then 120°C, 2 h), 1-acetoxy-5-bromo-3-methylpentane (II) was obtained. The hydrolysis of 19.8 g of (II) (MeOH-H₂O, TsOH, 20°C, 15 h) gave 5-bromo-3-methylpentan-1-ol (III). From 18.1 g of (III) and 38.9 ml of 2,3-dihydropyran (Et₂O, TsOH, 20°C, 20 h) was obtained the 2-THPL ester of (III), (IV), which was converted into 3-methyloct-7-en-1-ol (V) by the treatment of the corresponding Grignard reagent with allyl bromide (THF, CuI-bi-2-pyridyl, 2°C, 4 h, Ar). The interaction of 1.42 g of (V) with Et₃Al (hexane, 20°C, Cp₂ZrCl₂, Ar) gave 3,7-dimethylnonan-1-ol (VI), boiling which with 48% HBr in the presence of concentrated H₂SO₄ gave 1-bromo-3,7-dimethylnonane (VII) which was then converted into the desired (VIII) by the reaction of the corresponding Grignard reagent with DMFA (0–2°C, 1 h; 20°C, 2 h; Ar). The characteristics of the compounds — yield (%), n_D (°C): (I), 79, 1.4340 (22); (III) 89, 1.4660 (23); (IV), 82, 1.4739 (23); (V), 85, —; (VI), 90, 1.4483 (20); (VII), 88, 1.4409 (22); (VIII), 88, 1.4589 (22). Details of the IR and PMR spectra of compounds (II)–(VII) are given.Institute of Chemistry, Bashkir Scientific Center, Urals Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 272–276, March–April, 1989.     

Mehrstufige Redoxsysteme. XLIX. Mitteilung. Mit π-Systemen substituierte 1,3-Dimethylidencyclobutane: Synthese und Eigenschaften

Multistep Redox Systems. 1,3-Dimethylidenecyclobutanes Substituted by π-Syntheses and Properties As potential redox systems 1,3-dimethylidenecyclobutanes are synthesized in which the ‘exo’-methylidene group participates in a cyclopentadienyl (type C4 )or cycloheptatrienyl (type A5 ) system. Benzo-annellated systems are also described. The formation of the C?C bond by the reaction of thioketones ( 3 and 31 ) with diazo compounds is extended to extended to 1,6,7,21 , and 24 , which so far had not been employed. In some cases, intermediate thiiranes can be isolated (e.g. 4 ) which are smoothly transformed into the target compounds of types C4 and A5 by extrusion of sulfur. The new C?C bonds may be introduced stepwise, thereby allowing the synthesis of unsymmetrically substituted 1,3-dimethylidenecyclobutanes (e.g. 20 and 35 ). Reduction of by Na does not produce bicyclobutanes but compounds 43 and 44 with one dihydrofulvene unit.     

Acyl- und Alkylidenarsane. VI. Vergleichende Untersuchungen zur Struktur von Bis (2,2-dimethylpropionyl) phenylarsan und -phosphan

Acyl- and Alkylidenearsines. VI. Comparative Studies on the Structures of Bis(2,2-di-methylpropionyl)phenylarsine and -phosphine . Bis(2,2-dimethylpropionyl)phenylarsine 1a [19] and -phosphine 1b [20] prepared from the corresponding bis(trimethylsilyl) derivative and 2,2-dimethylpropionyl chloride, crystallize in the monoclinic space group P2₁/c with following dimensions of the unit cell determined at a temperature of measurement of ?70 ± 3°C/?73 ± 3°C: a = 1449.3(7)/1468.3(3); b = 1050.0(5)/985.9(2); c = 1138.5(4)/1159.4(4) pm; β = 108.27(3)/105.61(3)°; Z = 4. X-ray structure determinations (R_w = 0.044/0.044) reveal distances of 205 and 191 pm between the pnicogen and the carbon atom of the carbonyl group which, as in similar trifluoromethyl compounds [2], are definitely elongated with respect to standard values of 194 and 183 pm. Further characteristic mean bond lengths and angles are: As? C(phenyl) 194; P? C(phenyl) 184; C?O 119/121; C(O)? C 153/154; C(O)? As? C(O) 91; C(O)? P? C(O) 95; As? C? O 120; P? C? O 120; As? C(O)? C 117 and P? C(O)? C 118°.     

Iminoacylation. 3. Formation of platinum(IV)-based metallaligands due to facile one-end addition of vic-dioximes to coordinated organonitriles

The reaction of vic-dioximes with the organonitrile platinum(IV) complexes trans-[PtCl4(RCN)2] (R = Me, CH2Ph, Ph, vic-dioxime = dimethylglyoxime; R = Me, vic-dioxime = cyclohexa-, cyclohepta-, and cyclooctanedione dioximes) proceeds rapidly under relatively mild conditions and affords products of one-end addition of the dioximes to the nitrile carbon, i.e. [PtC4(NH=C(R)ON=[spacer]=NOH)2] (1-6) (R = Me, CH2Ph, Ph, spacer = C(Me)C-(Me) for dimethylglyoxime; R = Me, spacer = C[C4H8]C, C[C5H10]C, C[C6H12]C for the other dioximes), giving a novel type of metallaligand. All addition compounds were characterized by elemental analyses (C, H, N, C1, Pt), FAB mass spectrometry, and IR and 1H, 13C[1H], and 195Pt NMR spectroscopy. X-ray structure determination of the dimethylformamide bis-solvate [PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] x 2DMF (la) disclosed its overall trans geometry with the dimethylglyoxime part in anti configuration and the amidine one-end (rather than N,N-bidentate) coordination mode of the N-donor ligands. When a mixture of cis- and trans-[PtC4(MeCN)2] in MeCN was treated with dimethylglyoxime, the formation of, correspondingly, cis- and trans-[PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] (1) was observed and cis-to-trans isomerization in DMSO-d6 solution was monitored by 1H, 2D [1H,15N] HMQC, and 195Pt NMR spectroscopies. Although performed ab initio calculations give evidence that the trans geometry is the favorable one for the iminoacylated species [PtCl4-(ligand)2], the platinum(IV) complex [PtCl4(NH=C(Me)ON=C[C4Hs]C=NOH)2] (4) was isolated exclusively in cis configuration with the two metallaligand "arms" held together by intramolecular hydrogen bonding between the two peripheral OH groups, as it was proved by single-crystal X-ray diffractometry. The classic substitution products, e.g. [PtC12(N,N-dioximato)2] (12-15), are formed in the addition reaction as only byproducts in minor yield; two of them, [PtCl2(C7H11N2O2)2] (14) and [PtCl2(C8H13N2O2)2] (15), were structurally characterized. Complexes (12-15) were also prepared by reaction of the vic-dioximes with [PtCl4L(Me2SO)] (L = Me2SO, MeCN), but monoximes (Me2C=NOH, [C4H8]C=NOH, [C5H10]C=NOH, PhC(H)=NOH, (OH)C6H4C(H)= NOH) react differently adding to [PtCl4(MeCN)(Me2SO)] to give the corresponding iminoacylated products [PtCl4(NH=C(Me)ON=CRR')(Me2SO)](7-11).     

Chemical applications of topology and group theory. 34. Structure and bonding in titanocarbohedrene cages

Chemical bonding models are developed for the titanocarbohedrenes Ti14C13 and Ti8C12 by assuming that the Ti atoms use a six-orbital sd5 manifold and there is no direct Ti...Ti bonding. In the 3 x 3 x 3 cubic structure of Ti14C13, the 8 Ti atoms at the vertices of the cube are divided into two tetrahedral sets, one Ti(III) set and one Ti(IV) set, and the 6 Ti atoms at the midpoints of the cube faces exhibit square planar TiC4 coordination with two perpendicular three-center four-electron bonds. The energetically unfavorable Th dodecahedral structure for Ti8C12 has 8 equivalent Ti(III) atoms and C2(4-) units derived from the complete deprotonation of ethylene. In the more energetically favorable Td tetracapped tetrahedral structure for Ti8C12, the C2 units are formally dianions and the 8 Ti atoms are partitioned into inner tetrahedra (Ti(i)) bonded to the C2 units through three-center Ti-C2 bonds and outer tetrahedra (Ti degrees) bonded to the C2 units through two-center Ti-C bonds. The Ti atoms in one of the Ti4 tetrahedra are Ti(0) and those in the other Ti4 tetrahedron are Ti(III). Among the two such possibilities, the lower energy form has the (Ti0)o4(Ti(III))i4 configuration, corresponding to dicarbene C2 ligands with two unpaired electrons in the carbon-carbon pi-bonding similar to the multiple bond in triplet O2. This contrasts with the opposite (Ti(III)o4(Ti0)i4 configuration in the higher energy form of Th-Ti8C12, corresponding to ethynediyl ligands with full C...C triple bonds and unpaired electrons in the C sp hybrid orbitals for sigma-bonding to Ti.