The behaviour of beryllium μ4-oxo-μ-carboxylates under electron impact

The electron impact mass spectra of eight polynuclear beryllium complexes Be₄O(RCO₂)₆ (R?H, CH₃, C₂H₅) and Be₄O(RCO₂)₅OR′ (R?CH₃, R′?H, CH₃, C₂H₅, C₃H₇; R?C₂H₅, R′?C₂H₅) are reported. The major fragmentations involve the elimination of (RCO)₂O (RCOOR′) or Be(RCO₂)₂ (Be(RCO₂)OR′) from the ions [M? L]⁺ and of {(R? H)CO}, (R′? H), H₂O and BeO from the lighter ions. The fragmentation patterns are practically independent of the organic groups present and can be rationalized by stereochemical considerations.     

Silicium-stickstoff-fluorverbidungen: V. Darstellung neuer silylaminofluorsilane

Compounds of the composition RR′SiFNR″Si(CH₃)₃ (R = H, F, CH₃, C₂H₅, C₃H₇, C₂H₃, C₆H₅, C(CH₃)₃; R = F, CH₃, C₆H₅; R″ = CH₃, C(CH₃)₃, Si(CH₃)₃) are obtained by the reaction of silicontetrafluoride or organo-substituted silicon-fluorides with the lithium salts of alkylsilylamines in a molar ratio of $\text{1}\text{1}$. The disubstituted compounds RSiF(NR′Si(CH₃)₃)₂ (R = H, F, CH₃, C₂H₃, C₆H₅; R′ = CH₃, C(CH₃)₃) result when the reactants are in a $\text{1}\text{2}$ molar-ratio. Likewise the unsymmetrical siliconfluorsilylamines of the formulae F₂Si(NRSi(CH₃)₃) (NR′Si(CH₃)₃) (R = CH₃, R′ = C(CH₃)₃), as well as the trisubstituted compounds FSi(NCH₃Si(CH₃)₃)₃ and FSi(NCH₃Si(CH₃)₃)₂(N(Si(CH₃)₃)₂) were made. By reacting phenyltrifluorsilane with dialkylamines ($\text{1}\text{2}$) C₆H₅SiF₂NR₂(R = CH₃, C₂H₅) was obtained. The IR-, mass-, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported.     

ÜBER EINIGE REAKTIONEN DER DIALKYLBENZYLPHOSPHINIMIDE

Abstract

Dialkylbenzylphosphine imides C₆H₅CH₂–PRR′[dbnd]N″ (R, R′ = CH₃, C₂H₅; R″ = H, CH₃, Si(CH₃)₃ react with aliphatic and aromatic aldehydes in benzene solution on heating to 80°C directly and in high yields according to a Horner-Wittig-reaction with formation of an olefine whereas ketones like benzophenone and acetophenone only perform an O/NR″ exchange (R″ = H).

Dialkylbenzylphosphinimide C₆H₅CH₂–PRR′[dbnd]N″ mit R, R′ = CH₃, C₂H₅ und R″ = H, CH₃, Si(CH₃)₃ reagieren mit aliphatischen und aromatischen Aldehyden in benzolischer Lösung beim Erwärmen auf 80°C direkt und mit hohen Ausbeuten im Sinne einer Horner-Wittig-Reaktion unter Olefinbildung, während sich mit Ketonen wie Benzophenon oder Acetophenon nur ein O/NR″-Austausch (R″ = H) vollzieht.     

Darstellung neuer Alkylaminofluorsilane

Preparation of New Alkylaminofluorosilanes Aminofluorosilanes of the composition RSiF₂NR′R″ (R = H, CH₃, C₂H₃, C₆H₅; R′ = Si(CH₃)₃; R″ = C(CH₃)₃; R′ = R″ = i-C₃H₇), as well as C₆H₅SiF₂N[C(CH₃)₂CH₂]₂CH₂ are obtained by the reaction of fluorosilanes with the lithium salts of the corresponding amines in a molar ratio 1:1. The further reaction of these compounds with the lithium salts of alkylamines and anilin leads to the formation of the diaminofluorosilanes RSiFNR′R″NHR? (R? = C(CH₃)₃, i-C₃H₇, C₆H₅). The ¹H, ¹⁹F, ²⁹Si n.m.r. and mass spectra of the above mentioned compounds are reported.     

New deoxygenative transformations; reactions of (CO)4Fe[Si(CH3)3]2 with acyclic ethers

The reaction of cis-(CO)₄Fe[Si(CH₃)₃]₂ (I) with CH₃OSi(CH₃)₃ and C₆H₅CH₂-OSi(CH₃)₃ at 80°C affords good yields of [(CH₃)₃Si]₂O and the deoxygenation products RSi(CH₃)₃ (R = CH₃, C₆H₅CH₂). These reactions are proposed to occur via (CO)₄Fe(R)Si(CH₃)₃ intermediates. This is supported by the observed formation of cis-(CO)₄Fe(CH₃)Si(CH₃)₃ (II) during the more rapid reaction of I with (CH₃)₂O; subsequent (CH₃)₄Si elimination occurs. With (C₆H₅CH₂)₂O, I reacts at 80°C to yield C₆H₅CH₂Si(CH₃)₃ and C₆H₅CH₂OSi(CH₃)₃ as primary products. With C₆H₅CH₂OCH₃, I effects regioselective benzyl---oxygen bond cleavage.     

Triorganoantimon- und Triorganobismutderivate von 2-Pyridincarbonsäure und 2-Pyridylessigsäure Kristall- und Molekülstrukturen von (C6H5)3Sb(O2C-2-C5H4N)2 und (CH3)3Sb(O2CCH2-2-C5H4N)2

Triorganoantimony and Triorganobismuth Derivatives of 2-Pyridinecarboxylic Acid and 2-Pyridylacetic Acid. Crystal and Molecular Structures of (C₆H₅)₃Sb(O₂C-2-C₅H₄N)₂ and (CH₃)₃Sb(O₂CCH₂-2-C₅H₄N)₂ Triorganoantimony and triorganobismuth dicarboxylates R₃M(O₂C-2-C₅H₄N)₂ (M = Sb, R = CH₃, C₆H₅, 4-CH₃OC₆H₄; M = Bi, R = C₆H₅, 4-CH₃C₆H₄) and (CH₃)₃Sb(O₂CCH₂-2-C₅H₄N)₂ have been prepared from (CH₃)₃Sb(OH)₂, R₃SbO (R = C₆H₅, 4-CH₃OC₆H₄), or R₃BiCO₃ (R = C₆H₅, 4-CH₃C₆H₄) and the appropriate heterocyclic carboxylic acid. Vibrational spectroscopic data indicate a trigonal bipyramidal environment of M the O(? C)-atoms of the carboxylate ligands being in the apical and three C atoms (of R) in the equatorial positions; in addition coordinative interaction occurs in the 2-pyridinecarboxylates between M and O(?C) of one and N of the other carboxylate ligand and in (CH₃)₃)Sb(O₂CCH₂-2-C₅H₄N)₂ between Sb and O(?C) of both carboxylate ligands. (C₆H₅)₃Sb(O₂C-2-C₅H₄N)₂/(CH₃)₃Sb(O₂CCH₂-2-C₅H₄N)₂ crystallize monoclinic [space group P2₁/c/P2₁/n; a = 892.6(9)/1043.4(6), b = 1326.9(6)/3166.2(18), c = 2233.1(9)/1147.5(7) pm, β = 99.74(8)°/97.67(5)° Z = 4/8; d(calc.) = 1.522/1.553 × Mg m^?3; V_cell = 2606.7 × 10⁶/3757.0 × 10⁶pm³, structure determination from 3798/4965 independent reflexions (F ≥ 4.0 σ(F))/(I ≥ 1.96 σ(I), R(unweighted) = 0.024/0.036]. Sb is bonding to three C₆H₅/CH₃ groups in the equatorial plane [mean distances Sb? C: 212.2(3)/208.7(6) pm] and two carboxylate ligands via O in the apical positions [Sb? O distances: 218.5(2), 209.9(2)/212.1(3), 213.2(3) pm]. In (C₆H₅)₃Sb(O₂C-2-C₅H₄N)₂ there is a short Sb? O(?C) and a short Sb? N contact [Sb? O: 272.1(2), Sb? N: 260.2(2) pm] and distoritions of the equatorial angles [C? Sb? C: 99.2(1)°, 158.2(1)°, 102.0(1).] and of the axial angle [O? Sb? O: 169.9(1)°], and in (CH₃)₃Sb(O₂CCH₂-2-C₅H₄N)₂, which contains two different molecules in the asym-metric unit, there are two Sb? O(?C) contacts [Sb? O, mean: 302.2(4), and 310.7(4)pm, respectively] and distortions of the equatorial angles [C? Sb? C: 114.5(2)°, 132.4(3)° 113.1(2)°, and 123.9(3)° 115.5(2)°, 120.6(3)°, respectively] and of the axial angles [O? Sb? O: 174,9(1)°, 177.9(1)°, respectively].     

Bis(fluorbenzoyloxy)methylphosphanoxide

Bis(fluorbenzoyloxy)methyl phosphane oxides CH₃P(O)[OC(O)R]₂ [R = C₆H₄2F (1), C₆H₄3F (2), C₆H₄4F (3), C₆H₃2,6F₂ (4), C₆H2,3,5,6F₄ (5)] were prepared by treating silver salts of carboxylic acids AgOC(O)R with CH₃P(O)C?₂ (IR-, ¹H-, ¹⁹?F-and ³¹P{¹H}-NMR-data). The mixed anhydrides 1–5 show unusual thermal stability at room temperature. Stability against hydrolysis decreases with increasing number of fluorine-atoms. The reaction of R′P(O)C?₂ [R′ = CH₃, C₆H₅, (CH₃)₃C] with M^IOC(O)R_F [R_F = CF₃, C₂F₅, C₆F₅; M^I = Ag^I, Na^I T?^I] was investigated.     

Spektroskopische Untersuchungen an Siliciumverbindungen. XXXI. Schwingungsverhalten von p-substituierten N,N-Bistrimethylsilylanilinen

The following p-substituted N,N-bis-trimethlsilyl anilines p-X? C₆H₄? N[Si(CH₃)₃]₂ are prepared by silylation of free amines: X = H, CH₃, C₂H₅, CH₃O, CH₃CO, F, Cl, Br, J, CN, C₆H_S, (CH₃)₃SiO, and [(CH₃)₃Si]₂N, and the isotopic derivatives C₆H₅? ¹⁵N[Si(CH₃)₃]₂ and C₆D₅N[Si(CH₃)₃]₂. The vibrational spectra are reported and assigned. The molecular symmetry of p-[(CH₃)₃Si]₂N? C₆H₄? N[Si(CH₃)₃]₂ is determined. The influence of the mass of the substituents X on the positions of the ν_sSiNSi vibrational frequencies is discussed.     

Alkoxylierung von bis(trimethylsilyl)-aminofluorsilanen,sowie siloxanbildung unter äthereliminierung

The reaction of bis(trimethylsilyl)aminofluorsilanes, (Me₃Si)₂NSiF₂R (R = CH₃ or F), with sodium alcoholates or sodium phenylate yields under elimination of NaF alkoxy- and aryloxy-aminofluorosilanes of the composition (Me₃Si)₂NSiF(R)OR′(R′ = CH₃, C₂H₅, C₃H₇, C₆H₅). A disiloxane is formed by thermal elimination of diethyl ether from bis(trimethylsilyl)aminomethylfluoroethoxysilane. The IR, mass, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported. ab]Die Reaktion von Bis(trimethylsilyl)-aminofluorsilanen des Typs (Me₃Si)₂NSiF₂R (R = F, CH₃) mit Natriumalkoholaten und Natriumphenolat führt unter NaF-Abspaltung zu Alkyl- und Aryloxyaminofluorsilanen der Zusammensetzung: (Me₃Si)₂NSiF(R)OR′ (R′ = CH₃, C₂H₇, C₆H₅, C₆H₅). Ein Disiloxan könnte durch die thermische Eliminierung von Diäthyläther aus Bis(trimethylsilyl)aminomethyl-fluor-äthoxy-silylarnin erhalten werden.Die IR-, Massen-, ¹H- und ¹⁹F-NMR-Spektren der dargestellten Verbindungen werden mitgeteilt.     

Organische Phosphorverbindungen XXXVIII. Darstellung und Eigenschaften von Tris-(dialkoxyphosphonyl-methyl)-, Tris-(alkoxyphosphinyl-methyl)-und Tris-(oxophosphoranyl-methyl)-phosphinsäureestern sowie der entsprechenden Säuren [1]

Tris-chloromethyl-phosphine oxide, (ClCH₂₎₃ P?O(I), is obtained by chlorination of (HOCH₂₎₃P?O with PCl₅ or (C₆H₅₎₃PCl₂, and also by oxidation of (CICH₂₎₃P?O and (ClCh₂₎₂(CH₃)P?O. High yields of tris-(dialkyloxyphosphonly-methyl)-phosphine oxides, [RO₂(O)PCH_2]2P?O (II) (R?CH₃, C₂H₅, iso-C₃H₇, n-C₄H₉, 2- ethyl-hexyl), tris (alkyloxyphosphinyl-methyl)-phosphine oxides, [R₂(O)PCH_2]3P?O(R = C₆H₅, CH₃) are obtained by heating tris-chloromethyl-phosphine oxides, [(RO) (R′) (O)PCH_2]3P?O (R = C₄H₉, R′? C₆H₅) and tris-(oxophosphoranyl-phosphine oxides with phosphites, phosphonites and phosphinites, respectively, at 170–180°C for several hours. Compounds II possess an extraordinarily high absorption capacity. Thus a warm. 2% solution of II (R = C₂H₅) in benzene solidifies completely on cooling so that no benzene can be poured off. Tris-dihydroxyphosphonyl-methyl)-phosphine oxide, [(HO)₂(O)PCH_2]3P?O, obtained by hydrolysis of II (R ? C₂H₅) with refluxing conc. HCl or by thermal decomposition of II (R ? iso-C₃H₇) at 190°, titrates in aqueous solution as a hexabasic acid with breaks at pH = 4,4 (three equivalents) and pH = 10,7 (three equivalents). It forms crystalline salts with amines, alkali and alkaline earth metals, and is an excellent chelating agent. The ¹H- and ^31?P-NMR. spectra of all the compounds prepared are discussed.     

Unterschiedliche Cyclisierungsmechanismen von Aminofluorsilanen

Different Mechanisms of the Cyclisation of Aminofluorosilanes The reaction of aminofluorosilanes of the type RR′SiFNHR″ (R = H, F, CH₃, C₂H₃, C₆H₅, C(CH₃)₃; R′ = C(CH₃)₃, NiC₃H₇Si(CH₃)₃, NC(CH₃)₃Si(CH₃)₃, N[Si(CH₃)₃]₂; R″ = iC₃H₇, C(CH₃)₃, C₆H₅) with butyllithium depends on the steric influence of the ligands. With increasing size of the ligands the reaction takes its pathway from the substitution under LiF elimination via dimerisation with additional elimination of butan to the C? H cleavage and cyclisation via a methylen group. A further increase of the size of the substituted groups leads through the intermediate formation of a silicenium-ylid to ring closure reactions. These occure by migration of a methanid ion leading to intermolecular nucleophilic substitution. The isolated acyclic and heterocyclic compounds are described and the mass and ¹H-n.m.r. spectra are reported.     

Die Elektronenstoßfragmentierung von substituierten Dimethylalkoxysilanen

Electron Impact Fragmentation of Substituted Dimethylalkoxysilanes The mass spectra of substitued dimethylalkoxysilanes (H₃C)₂SiOCH₃R (R ? ? F, ? Cl, ? H, ? OCH₃, ? C₆H₅, ? CH₃, ? C₂H₅, ? n-C₃H₇), and (H₃C)₂SiOC₂H₅R (R ? ? Cl, ? C₆H₅, ? CH₃, ? C₂H₅) have been recorded and the fragmentation patterns are presented. The yield of the electron impact induced reaction (M-15)⁺→(M-45)⁺+ H₂CO occuring upon fragmentation of substituted dimethylmethoxysilanes depends on the substituent R. A quantum chemical calculation was carried out by CNDO/2 method to determine the electron density distribution in the ion at mass number (M-15). It is shown that a correlation exists between the Si? O? π bond order in this ion and the yield as well as the activation energy of this reaction.     

Umsetzungen von Borazinderivaten mit Bis(trimethylsilyl)-acetamid und Lithiumhexamethyldisilazan

Bis-(trimethylsilyl)acetamide (BSA) reacts with borazines [RNBX]₃, R=H,X=F; R=CH₃,X=F; R=C₆H₅,X=F and R=C₆H₅,X=Cl to the corresponding borazines,X=OSi(CH₃)₃. The¹H-NMR signal of the Si(CH)₃-groups of [C₆H₅NBOSi(CH₃)₃]₃ is at abnormally high field. With [CH₃NBCl]₃,BSA forms borazines which contain both Si(CH₃)₃O- and O?C(CH₃)=NSiR₃ groups bonded to the boron atoms. With LiN[Si(CH₃)₃]₂, [CH₃NBCl]₃ forms silylaminoboranes.¹H-NMR, mass spectrometric and analytical data are reported.     

Preparation and characterization of acrylates and polyacrylates having variable fluorine contents and distributions

Five acrylic esters having different fluorine contents and distributions in their side-groups (i.e., CH₂=CHC(O)OR, where R = ? C(CH₃)₂C₆F₄H, ? C(CH₃)₂C₆F₅, ? C(CF₃)₂C₆F₅, ? C(CF₃)₂C₆H₅, and ? C(CH₃)₂C₆H₅) have been prepared from the reactions of the lithium salts of their corresponding alcohols with acryloyl chloride. These monomers are polymerized under identical conditions by the radical initiator AIBN and five polyacrylates were prepared having the structure of ? [ ? CH₂CHC(O)OR? ]_n? . These addition polymers were compared and fully characterized by GPC, VPO, DSC, TGA, NMR, IR, and UV-visible spectroscopies, and they showed potential for practical applications. Significant differences in their thermal stabilities were found with respect to fluorine contents and distributions in these polyacrylates, and the highest stability arises from CF₃ substitutions in the side-chains of the polymers. © 1994 John Wiley & Sons, Inc.     

Triorganoantimon- und Triorganobismutderivate von Carbonsäuren fünfgliedriger Heterocyclen Kristall- und Molekülstruktur von (C6H5)3Sb(O2C-2-C4H3S)2

Inhaltsübersicht. Triorganoantimon- und Triorganobismutdicarboxylate R₃M[O₂C(CH₂)ⁿ-2-C₄H₃X]₂ (M = Sb, R = CH₃, C₆H₁₁, C₆H₅, 4-CH₃OC₆H₄; M = Bi, R = C₆H₅, 4-CH₃C₆H₄; n = 0, X = O, S, NH, NCH₃. M = Sb, R = CH₃, C₆H₅; M = Bi, R = C₆H₅; n = 1, X = O, S. M = Sb, R = C₆H₁₁, n = 1, X = S; R = 4-FC₆H₄, n = 0, X = O, S, NCH₃; R = 2,4,6-(CH₃)₃C₆H₂, n = 0, X = O, S, NH) wurden durch Reaktionen von R₃Sb(OH)₂ (R = CH₃, C₆H₁₁, 2,4,6-(CH₃)₃C₆H₂), R₃SbO (R = C₆H₅, 4-CH₃OC₆H₄, 4-FC₆H₄) bzw. R₃BiCO₃ mit den entsprechenden fünfgliedrigen heterocyclischen Carbonsäuren 2-C₄H₃X(CH₂)_nCOOH dargestellt. Auf der Basis schwingungsspektroskopischer Daten wird für alle Verbindungen eine trigonal bipyramidale Umgebung vom M (zwei O-Atome von einzähnigen Carboxylatliganden in den apikalen, drei C-Atome von R in den äquatorialen Positionen) vorgeschlagen, ferner eine schwache Wechselwirkung zwischen O(=C) jeder Carboxylatgruppe und M. Die Kristallstrukturbestimmung von (C₆H₅)₃Sb(O₂C–2-C₄H₃S)₃ stützt diesen Vorschlag. Die Verbindung kristallisiert triklin [Raumgruppe P$1; a = 891,8(14), b = 1058,2(12), c = 1435,6(9) pm, α = 68,53(8), β = 85,47(9), γ = 85,99(11)°; Z = 2; d(ber.) = 1,607 Mg m^–3; V(Zelle) = 1255,6 ų; Strukturbestimmung anhand von 3947 unabhängigen Reflexen (F_o > 3σ(F²_o)), R(ungewichtet) = 0,037]. Sb bindet drei C₆H₅-Gruppen in der äquatorialen Ebene [mittlerer Abstand Sb–C: 211,1(5)pm] und zwei einzähnige Carboxylatliganden in den apikalen Positionen einer verzerrten trigonalen Bipyramide [mittlerer Abstand Sb–O: 212,0(4) pm]. Aus den relativ kurzen Sb – O(=C)-Abständen [274,4(4) und 294,9(4) pm] und aus der Aufweitung des dem O(=C)-Atom nächsten äquatorialen C–Sb–C-Winkels auf 145,9(2)° [andere C-Sb-C-Winkel: 104,4(2), 109,5(2)°] wird auf schwache Sb–O(=C)-Koordination geschlossen. Schließlich wird eine Korrelation zwischen dem (+, –)I-Effekt des Organoliganden R an M (M = Sb, Bi) und der Stärke der M–O(=C)-Koordination in den Dicarboxylaten R₃M[O₂C(CH₂)_n–2-C₄H₃X]₂ vorgeschlagen. Triorganoanümony and Triorganobismuth Derivatives of Carbonic Acids of Five-membered Heterocycles. Crystal and Molecular Structure of (C₆H₅)₃Sb(O₂C–2-C₄H₃S)₂ Triorganoantimony- and triorganobismuth dicarboxylates R₃M[O₂C(CH₂)_n–2-C₄H₃X]₂ (M = Sb, R = CH₃, C₆H₁₁, C₆H₅, 4-CH₃OC₆H₄; M = Bi, R = C₆H₅, 4-CH₃C₆H₄; n = 0, X = O, S, NH, NCH₃. M = Sb, R = CH₃, C₆H₅; M = Bi, R = C₆H₅; n = 1, X = O, S. M = Sb, R = C₆H₁₁, n = 1, X = S; R = 4-FC₆H₄, n = 0, X = O, S, NCH₃; R = 2,4,6-(CH₃)₃C₆H₂, n = 0, X = O, S, NH) have been prepared by reaction of R₃Sb(OH)₂ (R = CH₃, C₆H₁₁; 2,4,6-(CH₃)₃C₆H₂), R₃SbO (R = C₆H₅, 4-CH₃OC₆H₄, 4-FC₆H₄) or R₃BiCO₃ with the appropriate five-membered heterocyclic carboxylic acid. From vibrational data for all compounds a trigonal bipyramidal environment around M (two O atoms of unidendate carboxylate ligands in apical, three C atoms (of R) in equatorial positions) is proposed and also an additional weak interaction of O(=C) of each carboxylate group and M. The crystal structure determination of Ph₃Sb(O₂C–2-C₄H₃S)₂ gives additional prove to this proposal. It crystallizes triclinic [space group P$1; a = 891.8(14), b = 1058.2(12), c = 1435.6(9) pm, α = 68.53(8), β = 85.47(9), γ = 85.99(11)°; Z = 2; d(calc.) = 1.607 Mg m^–3; V_cell = 1255.6 ų; structure determination from 3 947 independent reflexions (F_o > 3σ(F²_o)), R(unweighted) = 0.037]. Sb is bonding to three C₆H₅ groups in the equatorial plane [mean distance Sb–C: 211.1(5) pm] and two unidentate carboxylate ligands in the apical positions of a distorted trigonal bipyramid [mean distance Sb–O: 212.0(4) pm]. From the relatively short Sb–O(=C) distances [274.4(4) and 294.9(4) pm] and from the enlarged value of the equatorial C–Sb–C angle next to the O(=C) atom [145.9(2)°; other C–Sb–C angles: 104.4(2), 109.5(2)°] additional weak Sb–O(=C) coordination is inferred. Finally a correlation between the (+, –) I-effect of the organic ligands It at M and the strength of the M–O = C interaction is suggested.     

X-ray analysis of 1,3-dioxa-6-aza-2-silacyclooctane derivatives

X-ray analysis has been conducted on four dioxaazasilacyclooctanes R₂Si(OCH₂CH₂)₂NR′ with R = C₆H₅, R′ = CH₃ (IV); R = C₆H₅, R′ = (CH₃)₃C (V); R = CH₃, R′ = C₆H₅ (VI) and R = R′ = C₆H₅ (VII). The interatomic distances SiN measured for these compounds had the values: 2.68 (IV), 3.16 (V), 3.19 (VI) and 3.08 Å (VII), indicating weak nitrogen—silicon interaction and a virtual lack of coordinate Si ← N bonding. The data of other authors and our own evidence suggest that the Si ← N interaction in these compounds is strongly influenced by the electronic effects of Si- and N-substituents and, in particular, by the steric effects of the latter.     

Disilynes. III [1] A Relatively Stable Disilyne RSi≡SiR (R = SiMe(SitBu3)2)

The disilyne R**Si≡SiR** (R** = SiMe(SitBu₃)₂), prepared as the first isolable and realtively stable silicon compound with a SiSi triple bond two years ago by dehalogenation of trans‐R**ClSi=SiClR** with LiC₁₀H₈ in thf at ‐78 °C (calc.: Si≡Si distance 2.072Å, Si‐Si≡Si bond angle 148°), forms with CH₂=CH₂ a [2+2] and with CH₂=CH‐CH=CH₂ a [2+4] cycloadduct. The ethene adduct takes up oxygen very easily with change of the Si=Si group into a SiOSiO ring with formation of R**Si(μ‐O)(μ‐O)(μ‐C₂H₄)SiR**. By heating the disilyne in heptane to ca. 50 °C in the presence of traces of thf it transforms into a monoxide of the ethene adduct with formation of R**Si(μ‐O)(μ‐C₂H₄)SiR**. In thf, the disilyne rearranges at r.t. and below by migration of a SitBu₃ group with formation of a silyl substituted cyclotrisilene. X‐ray structure determinations of the ethene adduct and its mono‐ and dioxide are presented.     

The Reactions of Two New Alkoxy-silyl Functionalized Alkynes with M<Subscript>3</Subscript>(CO)<Subscript>12</Subscript> {M = Fe,Ru} and Co<Subscript>2</Subscript>(CO)<Subscript>8</Subscript>. Spectroscopic Identification of the Products

The new alkoxysilyl-functionalized alkynes [HC≡CCH₂N(H)C(=O)N(H)(CH₂)₃Si(OEt)₃] and [HC≡C(C₆H₄)–N(H)C(=O)N(H)(CH₂)₃Si(OEt)₃] have been synthesized using literature methods. These have been reacted with Fe₃(CO)₁₂, Ru₃(CO)₁₂ and Co₂(CO)₈. With the iron carbonyl only decomposition was observed: with Ru₃(CO)₁₂ splitting of the alkynes into their parent components and formation of the complexes (μ-H)Ru₃(CO)₉[HC=N(CH₂)₃Si(OEt)₃], (μ-H)Ru₃(CO)₉[C–C(C₆H₄)NH₂] and (μ-H)₂Ru₃(CO)₉[HC–CCH₃] occurred. Finally, with Co₂(CO)₈ formation of complexes Co₂(CO)₆(HC₂R) R=(C₆H₄)NH₂, CH₂NH(CO)NH(CH₂)₃Si(OEt)₃, (C₆H₄)NH(CO)NH(CH₂)₃Si(OEt)₃ containing the intact alkynes could be obtained.     

羰基化合物在Si(100)表面[2+2]环加成和α-H裂解反应的选择性

最近研究表明: 丙酮能与半导体Si(100)表面发生[2+2]环加成和α-H 裂解反应形成相应的Si―C键或Si―O键, 在半导体材料的合成方面具有重要意义. 为进一步弄清不同羰基化合物在Si(100)表面的反应机理,本文应用密度泛函理论方法在B3LYP/6-311++G(d,p)//6-31G(d)水平上较为系统地研究了一系列羰基化合物CH₃COR (R=CH₃, H, C₂H₅, C₆H₅)与Si(100)表面的反应. 研究结果表明: 不论是[2+2]环加成反应还是α-H 裂解反应都对应较低的反应势垒(小于25 kJ·mol^-1); 环加成反应的势垒比α-H 裂解反应的势垒略高; 羰基上的取代基对反应势垒的影响较少; α-H裂解反应产物为动力学和热力学控制产物; 对丁酮来说, 1-位和3-位H原子的裂解反应都比较容易, 势垒相差很小. 这些结果表明羰基化合物与Si(100)表面的反应将得到多种产物.     

Phosphaacetylenehexacarbonyldicobalt complexes: new cluster lewis bases

The reaction of RCCl₂ PCl₂ (R = CH₃, C₆ H₅, (CH₃)₃ Si) with dicobalt octacarbonyl in THF at ?78°C gave the new (RCP)Co₂(CO)₅ complexes, which contain the CPCo₂ cluster unit, as air-sensitive red oils. The complex with R = CH₃ reacted with (OC)₅M-THF to give the corresponding M(CO)₅ (M = Cr, W) adducts and the complex with R = C₆H₅ could be acetylated in the para position with CH₃ C(O)Cl/AlCl₃.