Bildung siliciumorganischer Verbindungen. 89. Selektive Photobromierung von Si-methylierten Carbosilanen

Formation of Organosilicon Compounds. 89. Selective Photobromination of Si-methylated Carbosilanes A selective photobromination of the C atoms in the skeleton of Si-methylated carbosilanes is reported. (me₃Si? CH₂)₂Sime₂ reacts to me₃Si? CBr₂? Sime₂? CH₂? Sime₃ in good yields (me = CH₃); the second CH₂ group is considerably slower brominated. Photobromination of (me₂Si? CH₂)₃ consecutively yields a and b . Also from (me₂Si? CH₂)₄ the derivative with one CBr₂ group is accessible. Bromination of tertiary CH groups is highly preferred; this is shown by the selective formation of c . The C-bromination of SiBr-substituted carbosilanes is significantly more difficult; nevertheless (Brme₂Si)₂CH₂ selectively forms (Brme₂Si)₂CBr₂. Brme₂Si? CH₂? Sime₂? CH₂? Sime₃ forms Brme₂Si? CH₂? Sime₂? CBr₂? Sime₃, i. e., only the CH₂ group non-adjacent to SiBr is attacked. The formation of CHBr groups could not be detected. Higher temperatures and longer reaction times increase the formation of polymers.     

Synthesis of cationic dialkylgold(III) complexes: nature of the facile reductive elimination of alkane

A series of gold(III) cations of the type cis-[CH₃)₂AuL₂]⁺ X^? where L  Ph₃, PMePh₂, PMe₂Ph, PMe₃, AsPh₃, AsPh₃, SbPh₃, $\text{1}\text{2}$H₂NCH₂CH₂NH₂, $\text{1}\text{2}$ Ph₂PCH₂CH₂-PPh₂, $\text{1}\text{2}$ Ph₂AsCH₂CH₂AsPh₂, and $\text{1}\text{2}$o-C₆H₄(AsMe₂)₂ and X  BF₄^?, PF₆^?, ClO₄^?, and F₃CSO₃^? has been prepared. In addition, the cis complexes [(CH₃)(CD₃)-Au(PPh₃)₂]F₃CSO₃, [(C₂H₅)₂Au(PPh₃)₂]F₃CSO and [(n-C₄H₉)₂Au(PPh₃)₂]F₃-CSO₃ have been synthesized. All have been characterized by PMR, Raman and infrared spectroscopy. These [R₂AuL₂]X compounds yield only ethane, butane, or octane via reductive elimination, and no disproportionation is observed. The alkane eliminations have been studied in CHCl₃, CH₃Cl₂, and CH₃COCH₃ solution as a function of temperature, concentration of the complex, and concentration of added ligand L. Elimination is fastest when L is bulky (PPh₃ > PMePh₂ > PMe₂Ph > PMe₃), decreases in the sequence SbPh₃ > AsPh₃ > PPh₃, is slow with chelating ligands, is inhibited by excess ligand, and there is small anion effect as X is varied. As R is varied, the rate of elimination decreases Bu ? Et > Me. An intramolecular dissociative mechanism is proposed which involves rapid elimination of alkane from an electron deficient dialkylgold(III) complex with nonequivalent gold—carbon bonds and produces the corresponding [AuL₂]X complex.     

γ-Hydroxypropyl-functionalised iron thiolate complexes: crystal and molecular structure of [{Fe2(CO)6(μ-SCH2CH2CH2OH)}2(μ4-S)]

The γ-hydroxypropyl-functionalised diiron dithiolate complex [Fe₂(CO)₆(μ-SCH₂CH₂CH₂OH)₂] is prepared upon thermolysis of Fe₃(CO)₁₂ and HO(CH₂)₃SH and further reaction with dppm (dppm = Ph₂PCH₂PPh₂) affords [Fe₂(CO)₄(μ-dppm)(μ-SCH₂CH₂CH₂OH)₂]. From the reaction of Fe₃(CO)₁₂ with dppm(S₂) a minor product is the tetrairon cluster, [{Fe₂(CO)₆(μ-SCH₂CH₂CH₂OH)}₂(μ⁴-S)], the mode of formation of which is unclear. It has been crystallographically characterised and adopts a μ⁴-S bridged double butterfly structure which is compared with other crystallographically characterised complexes of this type. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cationic Palladium(II), Platinum(II), and Rhodium(I) Complexes as Acetalisation Catalysts

The use of [Pd(H₂O)2(Ph₂PCH₂CH₂PPh₂)] (CF₃SO₃)₂ as a catalyst for the acetalisation of a variety of aldehydes and ketones and for trans-acetalisation is described. It is also shown that Pt(H₂O)2(PH₂PCH₂CH₂PPh₂) (CF₃SO₃)₂ is at least as effective as the corresponding Pd compound, while much lower reaction rates are observed with [Rh(MeOH)₂(Ph₂PCH₂CH₂PPh₂)] [BF₄].     

Uranium-sulfilimine chemistry. The preparation of Cp2*UCl2(HNSPh2) and its hydrolysis with HNSPh2 · H2O

The reaction of Cp₂*UCl₂ with HNSPh₂ produces Cp₂*UCl₂(HNSPh₂), which is the first structurally characterized complex of a sulfilimine. The hydrolysis of Cp₂*UCl₂(HNSPh₂) with HNSPh₂ · H₂O yields a tetrauranium cluster whose heavy atom structure has been determined by x-ray diffraction and which is formulated as a U^IV/U^V complex: [Cp*(Cl)(HNSPh₂)U(μ₃-O)(μ₂-O)₂U(Cl)(HNSPh₂)₂]₂.     

Reaktionen von π-Organokomplexen des Nickels mit tertiären Phosphanen

Reactions of π-Organonickel Complexes with Tertiary Phosphanes In a hexane solution Ni(C₅H₅)₂ reacts with PBu₃ or Ph₂PBu forming the nickel(O) complexes Ni(PBu3)₄ or Ni(Ph₂PBu)₄ (A). Under the same conditions only one cyclopentadienyl ligand is substituted by PhPBu₂ and the nickel(I) compound (C₅H₅)Ni (PhPBu₂)₂ (B) is obtained. Products of the reactions between B and α,α′-dipyridyl, hydrogen chlorid in ether, or Ni(PhPBu₂),Cl₂ are Ni(dipy)₂, [PhPHBu₂]₂[NiCl₄], or (C₅H₅) Ni(PhPBu₂)₂Cl. By the reaction with HgCl₂ a cyclopentadienyl compound of an unknown structur is formed. The compound Ni(PhPBu₂)₄ which is analogous to A is synthesized by the reduction of bis(acety1acetonato)-nickel with Et₂AlOEt in the presence of PhPBu₂ or by the reaction of bis (cyclooctadiene-1,5)-nickel with PhPBu₂.     

Polymorphism of Ph2P(CH2Py)(NSiMe3) and the Staudinger Reaction of Ph2P(CH2Py) with Hydrogenazide1)

A new polymorph of the iminophosphorane Ph₂P(CH₂Py)(NSiMe₃), ( 1 ), is compared to a just recently published. The reaction of the starting material, the phosphane Ph₂P(CH₂Py) with N₃SiMe₃ in the presence of water gives [Ph₂P(CH₂Py)(NH₂)][N₃], ( 2 ). A comparison of the structural and NMR parameters of 2 with previously reported derivatives of 1 , suggests that 2 is best described as a phosphonium salt in which the negatively charged imino nitrogen atom is protonated, according to [Ph₂(CH₂Py)P⁺—NH₂][N₃]^—, rather than as an iminiumphosphane salt [Ph₂(CH₂Py)P=⁺NH₂][N₃]^—.     

Bildung siliciumorganischer Verbindungen. LXII. Teilbromierte Carbosilane

Formation of Organosilicon Compounds. LXII. Partial Brominated Carbosilanes The photobromination of 1 leads to compound 2 as well as to C-chlorinated derivatives if the time of reaction is prolonged. Compound 2 is also formed from (Br₂Si–CH₂)₃; Gl. (1) see ?Inhaltsübersicht”?. In a corresponding reaction (Cl₃Si–CH₂)₂SiCl₂ gives successively Cl₃Si–CHBr–SiCl₂–CH₂–SiCl₃, Cl₃Si–CBr₂–SiCl₂–CH₂–SiCl₃ and Cl₃Si–CCl₂–SiCl₂–CH₂–SiCl₃. (Cl₃Si)₂CBr₂ is accessible through the photobromination of (Cl₃Si)₂CH₂. The reactivity of the CBr₂-group is quite obvious in the reaction of Cl₂Si–CBr₂–SiCl₂–CH₂–SiCl₃ with LiAlH₄ yielding (H₃Si–CH₂)₂SiCl₂ as well as in the reaction of compound 2 with CH₃MgCl yielding [(CH₃)₂Si–CH₂]₃. By treatment of the SiH groups with bromine the preparation of compounds with the general formulas CH₃SiH_nBr_3?n; (H_3?nSiBr_n)₂CH₂; (H_3?nSiBr_n? CH₂)₂SiH_2?nBr_n; (H_2?nBr_nSi? CH₂)₃ and (H_3?nSiBr_n)₂CCl₂ is possible. Analysis of the nmr spectra shows that 1,3-Dibromo-1,3,5-trisilacyclohexane is formed to 67% in the trans and to 33% in the cis configuration; 1,3,5-Tribromo-1,3,5-trisilacyclohexane is formed to 80–90% in teh cis-trans configuration. The results of ¹H and ²⁹Si NMR investigations are reported.     

Electroreduction of CuO-V2O5 in sulfolane containing lithium perchlorate

Variations in the composition of polymetallic oxide system V₂O₅-CuO are found to be accompanied by a gradual change in electrochemical properties. Average discharge voltage of copper vanadates 2CuO-V₂O₅ and 4CuO-V₂O₅ is higher than that of V₂O₅. The depth of electroreduction of 2CuO-V₂O₅,3CuO-V₂O₅, and 4CuO-V₂O₅ is, respectively, 3.32, 3.0, and 2.7 electrons per mole of vanadium, which is almost twice that of V₂O₅.     

Siloxymethylamines as Aminomethylation Reagents for Amines Leading to Labile Diaminomethanes That can be Trapped as Their [Mo(CO)4] Complexes

Compound Et₃SiOCH₂NMe₂ transfers Me₂NCH₂ to R₂NH (R₂=Et₂, PhMe, [Cr(η⁶‐C₆H₅)(CO)₃]Me, PhH) to form previously unknown diaminomethanes, Me₂NCH₂NR₂ and, in the case of R₂=PhH, the triamine Me₂NCH₂N(Ph)CH₂NMe₂. The diaminomethanes exhibit an unreported disproportionation to a mixture of (R₂N)₂CH₂, (Me₂N)₂CH₂, and Me₂NCH₂NR₂, which can be trapped as their [Mo(CO)₄(diamine)] complexes. Whereas PhMeNCH₂NMe₂ is a labile material, the metal‐substituted ([(η⁶‐C₆H₅)Cr(CO)₃]MeNCH₂NMe₂ is a stable material. The triamine Me₂NCH₂N(Ph)CH₂NMe₂ is unstable with respect to transformation to 1,3,5‐triphenyltriazine, but is readily trapped as the bidentate‐triamineMo(CO)₄. All metal complexes were characterized by single‐crystal X‐ray diffraction.     

Selecting oxygen source for partial oxidation of methane to methanol using microwave plasmas

The methanol selectivity in partial oxidation of methane in microwave plasma reactors is improved by using H₂O in the presence or absence of O₂. The use of H₂O₂ as an oxygen source has a similar effect, although it is less effective than H₂O. The addition of H₂ to the system has little effect on selectivity. Two pathways are suggested for the formation of methanol. One involves a CH₃O^* or CH₃O₂ ^* intermediate, while the other involves a direct combination of CH₃ ^* and OH^* radicals. The first pathway is favored in the presence of O₂ while the latter is favored in the presence of H₂O or H₂O₂. The best results are obtained for the CH4-O₂-H₂O system when methanol is formed through both pathways.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Synthesis of Bis(pentafluoroethyl)germanes

The chemistry of bis(pentafluoroethyl)germanes (C₂F₅)₂GeX₂ is presented. The synthesis of such species requires Br₂GePh₂, wherein the phenyl substituents function as suitable protecting groups. After treatment with two equivalents of LiC₂F₅, (C₂F₅)₂GePh₂ is produced. The replacement of the phenyl rings is smoothly effected by gaseous HBr or HCl in the presence of a Lewis acidic catalyst. The trigermoxane [(C₂F₅)₂GeO]₃ results from the reaction of (C₂F₅)₂GeBr₂ with Ag₂CO₃. Its crystalline 1,10‐phenanthroline adduct was fully characterised by X‐ray diffraction. The combination of (C₂F₅)₂GeBr₂ with Bu₃SnH gave rise to the formation of (C₂F₅)₂GeH₂.     

Thermal analysis of dithiomalonamide complexes

Dithiomalonamide [H₂A, CH₂(CSNH₂)₂] and 2,2-dimethyldithiomalonamide [H₂B, C(CH₃)₂(CSNH₂)₂] can act as bidentate ligands and form stable, cationic 1∶2 complexes with general formula M₂(H₂L)₂X₂ [M=Ni²⁺, Pd²⁺, Pt²⁺;X=C1, Br, I; H₂L=H₂A, H₂B] in strong acidic medium. An elaborate thermal study is presented, based on results from elemental analyses and vibrational studies (IR and Raman spectroscopy). The H₂A complexes start to decompose by releasing two HX molecules whereafter a stable intermediate M(HA)₂ is formed. The H₂B complexes degrade in a different way; the metal-sulphur bond is broken and the ligand is expelled as a whole. Influences of the metal ion and of the halogenide counterions are investigated.     

New cyclic phosphonium salts derived from the reaction of phosphine-aldehydes with acid

Various cyclic phosphonium structures are formed in high yield by the deprotection of unstable phosphine-aldehydes in acidic solution. When there is a methylene spacer between the phosphine and the aldehyde, a phosphonium ion [PHR₂CH₂CH(OEt)₂]Br₂, R=iPrOH, Et is obtained. Reaction of these phosphonium salts with water produces the dimers [-PR₂CH₂CH(OH)-]₂[Br]₂ R = iPr, Et. When there is an ethylene spacer as in PPh₂CH₂CH₂CH(OCH₂CH₂O), a remarkable tetramer with a 16-membered ring [-PPh₂CH₂CH₂CH (OH)-]₄[Cl]₄ forms as one diastereomer in hydrochloric acid solution. Reaction of HCl with the protected phosphine-aldehyde with a propylene spacer (PPh₂CH₂CH₂CH₂CH(OCH₂CH₂O)) results in the formation of the monomeric phosphonium salt [-PPh₂ CH₂CH₂CH₂CH(OH)-]Cl with a 5-membered ring. Solid state structures of different ring types were determined using X-ray diffraction experiment.     

Hydrogen‐bonding and π–π stacking interactions in aquachloridobis(1,10‐phenanthroline)cobalt(II) chloride dichloridobis(1,10‐phenanthroline)cobalt(II) hexahydrate

The title compound, [CoCl(C₁₂H₈N₂)₂(H₂O)]Cl·[CoCl₂(C₁₂H₈N₂)₂]·6H₂O, is the first example of a new 1:1 cocrystal of the octahedral [CoCl₂(phen)₂] and [CoCl(phen)₂(H₂O)]⁺·Cl⁻ complexes (phen is 1,10‐phenanthroline). The latter form heterochiral dimers held by strong π–π stacking interactions via their phenathroline ligands, which confirms that π stacking is an important and reliable synthon in supramolecular design. In addition, the crystal structure is networked by H₂O...H₂O, H₂O...Cl⁻ and H₂O...Cl hydrogen bonds, which interconnect the different units of the cobalt complexes.     

The first compound with an unusual type of anion, [Li(SR)2]–: bis­(μ2‐aqua‐d2)tetra­kis(aqua‐d2)dilithium(I) bis­[bis­(tri‐tert‐butoxy­silanethiol­ato‐κ2O,S)lithate(I)] dihydrate‐d2

The title complex, [Li₂(D₂O)₆][Li(C₉H₂₇SSiO₃)₂]₂·2D₂O, is the first compound with an S—M bond (M = alkali metal) within an unusual type of lithate anion, [Li(SR)₂]⁻ {where R is Si[OC(CH₃)₃]₃}. There is a centre of symmetry located in the middle of the Li₂O₂ ring of the cation. All Li atoms are four‐coordinate, with LiO₄ (cations) and LiO₂S₂ (anions) cores. The singly charged [Li(SR)₂]⁻ anions are well separated from the doubly charged [Li₂(D₂O)₆]²⁺ cations; the distance between Li atoms from differently charged ions is greater than 5 Å. Both ion types are held within an extended network of O—D⋯O and O—D⋯S hydrogen bonds.     

Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex

Improving our comprehension of diverse CO₂ activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO₂ activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO₂ is readily reduced to CO, but isolated thorium(III) CO₂ activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)₃] ( 1 , Cp′′={C₅H₃(SiMe₃)₂‐1,3}), reacts with CO₂ to give the mixed oxalate‐carboxylate thorium(IV) complex [{Th(Cp′′)₂[κ²‐O₂C{C₅H₃‐3,3′‐(SiMe₃)₂}]}₂(μ‐κ²:κ²‐C₂O₄)] ( 3 ). The concomitant formation of oxalate and carboxylate is unique for CO₂ activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO₂ activation can differ from better understood uranium(III) chemistry.     

Synthesis,characterization and X-ray crystal structures of polyether and ethylene bridged bis(azolyl) platinum(II) complexes

The preparation of platinum(II) complexes of the types [PtCl₂{Y(CH₂CH₂O) _x CH₂CH₂Y}] (Y: imidazol-1-yl, im; pyrazol-1-yl, pz or benzimidazol-1-yl, bim) and [PtI₂{im(CH₂CH₂O) _x CH₂CH₂im}] with varying ligand backbone length (x between 0 and 3) is described. A new bis(pyrazol-1-yl) polyether compound, pz(CH₂CH₂O)₂CH₂CH₂pz, is reported. Spectroscopic characterization of the complexes is discussed. Two crystal structures of the general formula [PtCl₂{im(CH₂CH₂O) _x CH₂CH₂im}] (x is 1 or 3) are also reported.