Preparation of tris(trimethylsilyl)methyl (“trisyl”) derivatives of silicon

Treatment of (Me₃Si)₃CLi (“trisyl”lithium, TsiLi) with appropriate silicon halides has given a range of compounds of the type (Me₃Si)₃CSiRR′X; e.g., TsiSiCl₃, TsiSiMeCl₂, TsiSiMe₂X (X = Cl, OMe), TsiSiPh₂X (X = F, Cl, OMe), and TsiSiPhMeH. The trisyl group causes very large steric hindrance to nucleophilic displacements at the silicon to which it is attached, so that (unless one or more hydride ligands are present) most of the common displacements at silicon do not occur. However, halides can be reduced to hydrides by LiAlH₄, and the hydrides can be converted into halides in electrophilic displacements by hallogens. The presence of even one hydride ligand markedly reduces the hindrance, so that, for example, TsiSiPhHI reacts with refluxing methanol to give TsiSiPhH(OMe).     

Organometallic Reactions and Syntheses : Volume 6, E. I. Becker and M. Tsutsui,ed., Plenum Publishing Corporation., New York/ London, 1977, xii + 314 pages $47.40

The (Me₃Si)₃C group causes very large steric hindrance to nucleophilic displacement at a silicon atom to which it is attached, and (Me₃Si)₃CSiMe₂Cl is even less reactive than t-Bu₃SiCl towards base. The compounds (Me₃Si)₃CSiMe₂X (X = Cl, Br, or I) are cleaved by MeOH/MeONa to give (Me₃Si)₂CHSiMe₂OMe, possibly via the silaolefin (Me₃Si)₂ CSiMe₂, and the correspondLug (Me₃Si)₃ CSiPh₂X compounds undergo the analogous reaction even more readily. The halides (Me₃Si)₃CSiR₂X (X = Cl or Br) and (Me₃Si)₃CSiCl₃ do not react with boiling alcoholic silver nitrate, but the iodides (Me₃Si)₃CSiR₂I are rapidly attacked.     

Some highly sterically hindered organo-silanols and -siloxanes

Reaction of the iodides TsiSiMe₂I and TsiSiPh₂I, (Tsi  (Me₃Si)₃C) with AgClO₄ in t-BuOH provides a route to the silanols TsiSiMe₂OH and (Me₃Si)₂-C(SiPh₂Me)(SiMe₂OH), respectively. TsiSiMe₂OH gives the disiloxane TsiSiMe₂OSiMe₃ when treated with either (a) Me₃SiOClO₃ (prepared in situ from AgClO₄ and Me₃SiCl) in benzene, (b) Me₃SiI (in the presence of a little (Me₃Si)₂-NH), (c) O,N-bis(trimethylsilyl)acetamide, or (d) MeLi followed by Me₃SiCl. It does not react with Me₃SiCl, but with Me₂SiCl₂ gives TsiSiMe₂OSiMe₂Cl, and with CH₃COCl gives TsiSiMe₂OCOCH₃. The disiloxane is stable to methanolic acid or base, but reacts with KOH in H₂O/Me₂SO and with CF₃COOH to give TsiSiMe₂OH. The disiloxane (Me₃Si)₂C(SiPh₂Me)(SiMe₂OSiMe₃) is formed by treatment of (Me₃Si)₂C(SiPh₂Me)(SiMe₂OH) with Me₃SiI/(Me₃Si)₂NH. Treatment of TsiSiPhMeI with AgClO₄ in t-BuOH gives the silanols TsiSiPhMeOH and (Me₃Si)₂C(SiPhMe₂)(SiMe₂OH) (which with Me₃SiI/(Me₃Si)₂NH give the corresponding disiloxanes) along with some of the t-butoxide (Me₃Si)₂C(SiPhMe₂)(SiMe₂OBu^t).     

Reactions of some sterically-hindered organosilicon hydrides and iodides with halogens

The reaction of TsiSiMe₂H (I) (Tsi = (Me₃Si)₃C) with I₂ or with a molar equivalent of ICl gives the iodide TsiSiMe₂I (II) in hydroxylic media (MeOH, CH₃CO₂H, CF₃CO₂H) as it does in CCl₄. The reaction with I₂ is very fast in CF₃CO₂H, but in MeOH is only about as fast as in CCl₄. The iodide II reacts with ICl in MeOH to give a mixture of TsiSiMe₂OMe (III) and TsiSiMe₂Cl (IV), but the reaction is markedly slower than that in CCl₄ (in which IV is formed). The hydride I also reacts with INO₃ in MeOH to give II, and the latter reacts with INO₃ to give III. The reactions of TsiSiPh₂H (V) and TsiSiPh₂I (VI) with ICl in MeOH are markedly slower than those of I and II; even with one equivalent of ICl in MeOH, V gives a mixture of VI and the (rearranged) methoxide (Me₃Si)₂C(SiPh₂Me)(SiMe₂OMe) (VII). Reaction of VI with ICl in MeOH gives VII and the rearranged chloride (Me₃Si)₂C(SiPh₂Me)(SiMe₂Cl). The formation of methoxides in the reactions of the iodides II and VI with ICl in MeOH, and the rearrangements observed in the case of VI, are consistent with a mechanism involving an intermediate silicocation. Other mechanistic aspects are discussed.     

Dimethylerdmetall‐Heterocyclen als Derivate trimethylsilylierter, ‐germylierter und ‐stannylierter Phosphane und Arsane – Synthesen,Spektren und Strukturen

Dimethyl Earth‐Metal Heterocycles – Derivatives of Trimethyl‐silylated, ‐germylated, and ‐stannylated Phosphanes and Arsanes – Syntheses, Spectra, and Structures The organo earth‐metal heterocycles [Me₂M^III–E(M^IVMe₃)₂]_n with M^III = Al, Ga, In; E = P, As; M^IV = Si, Ge, Sn and n = 2, 3 (Me = CH₃) have been prepared from the dimethyl metal compounds Me₂M^IIIX (X = Me, H, Cl, OMe, OPh) and the pnicogen derivatives H_nE(M^IVMe₃)_3–n (n = 0, 1) according to known preparation methods. The mass, ¹H, ¹³C, ³¹P, ²⁹Si, ¹¹⁹Sn nmr, as well as the ir and Raman spectra have been discussed comparatively; selected representatives are characterized by X‐ray structure analyses. The dimeric species with four‐membered (E–M^III)₂ rings are isotypic and crystallize in the triclinic space group P1, the trimer [Me₂In–P(SnMe₃)₂]₃ with a strongly puckered (In–P)₃‐ring skeleton crystallizes with two formula units per cell in the same centrosymmetric triclinic space group.     

NMR-spektroskopische Untersuchungen an Undecamethylcyclohexasilanyl-Derivaten

The structure and ²⁹Si chemical shifts of nine undecamethylcyclohexasilanyl derivatives, Si₆Me₁₁X (X = Fe(CO)₂cp, SO₃CF₃, F, Cl, Br, I, H, C CH, OH), have been assigned using ¹J_SiSi and ²J_SiSi derived from ²⁹Si-INADEQUATE and ²⁹Si-INEPT-INADEQUATE and ²⁹Si-INEPT-INADEQUATE NMR spectra. Only the halo-derivatives exhibit linear correlation between ¹J_SiSi and Pauling electronegativities. The correlation of other derivatives is improved by employing Inamato's inductivity values. A new synthetic route to Si₆Me₁₁X (X = F, Cl, Br, I) has been developed.     

29Si NMR Spektroskopie von Cyclopentasilanen

The structure and ²⁹Si chemical shifts of the halodimethylsilylnonamethylcyclopentasilanes Si₅Me₉SiMe₂X (1–4) and the halononamethylcyclopentasilanes Si₅Me₉X (5–8) (X = F, Cl, Br, I) have been assigned using ¹J(SiSi) and ²J(SiSi) coupling constants derived from ²⁹Si-INADEQUATE and ²⁹Si-INEPT—INADEQUATE NMR spectra. The compounds exhibit good correlation between chemical shift, ¹J(SiSi) and Pauling electronegativities.     

The perfluoropinacolyl group,a stabilizing substituent for unsual phosphines and phosphoranes

The perfluoropinacolyl qroup (=PFP) stabilises halogenophosphoranes of the type $\text{1}$ e.g.

X¹=X²=X³=F,Cl,Br or X¹=X²=Cl,Br, X³=F , covalent species which are able to react with Li₂PFP to form spirocyclic systems [1]. Precursors of compounds $\text{1}$ are the phosphites $\text{2}$ (X=F,Cl,Br). The aminophosphite with X=NH₂ shows interesting behaviour towards hexafluoroacetone forming a spiro system containg a four and a five membered ring. Phosphites with X=NR¹R² add readily chlorine to give stable chlorophosphoranes. Products of the ammonolysis of the trifluorophosphoranes (X¹=X²=X³=F) were the aminophosphoranes (H₂N)_nPF_3?n(PFP) (n=1,2,3) in good yields. Dynamic processes of the latter compounds were discussed on the bases of low temperatur ¹⁹F n.m.r. spectroscopy.     

Modulating the frontier orbitals of L(X)Ga-substituted diphosphenes [L(X)GaP]2 (X = Cl,Br) and their facile oxidation to radical cations

Modulating the electronic structures of main group element compounds is crucial to control their chemical reactivity. Herein we report on the synthesis, frontier orbital modulation, and one-electron oxidation of two L(X)Ga-substituted diphosphenes [L(X)GaP]₂ (X = Cl 2a, Br 2b; L = HC[C(Me)N(Ar)]₂, Ar = 2,6-i-Pr₂C₆H₃). Photolysis of L(Cl)GaPCO 1 gave [L(Cl)GaP]₂2a, which reacted with Me₃SiBr with halide exchange to [L(Br)GaP]₂2b. Reactions with ^MeNHC (^MeNHC = 1,3,4,5-tetramethylimidazol-2-ylidene) gave the corresponding carbene-coordinated complexes L(X)GaPP(^MeNHC)Ga(X)L (X = Cl 3a, Br 3b). DFT calculations revealed that the carbene coordination modulates the frontier orbitals (i.e. HOMO/LUMO) of diphosphenes 2a and 2b, thereby affecting the reactivity of 3a and 3b. In marked contrast to diphosphenes 2a and 2b, the cyclic voltammograms (CVs) of the carbene-coordinated complexes each show one reversible redox event at E_1/2 = −0.65 V (3a) and −0.36 V (3b), indicating their one-electron oxidation to the corresponding radical cations as was confirmed by reactions of 3a and 3b with the [FeCp₂][B(C₆F₅)₄], yielding the radical cations [L(X)GaPP(^MeNHC)Ga(X)L]B(C₆F₅)₄ (X = Cl 4a, Br 4b). The unpaired spin in 4a (79%) and 4b (80%) is mainly located at the carbene-uncoordinated phosphorus atoms as was revealed by DFT calculations and furthermore experimentally proven in reactions with ⁿBu₃SnH, yielding the diphosphane cations [L(X)GaPHP(^MeNHC)Ga(X)L]B(C₆F₅)₄ (X = Cl 5a, Br 5b). Compounds 2–5 were fully characterized by NMR and IR spectroscopy as well as by single crystal X-ray diffraction (sc-XRD), and compounds 4a and 4b were further studied by EPR spectroscopy, while their bonding nature was investigated by DFT calculations.

Carbene-coordination allowed for one-electron oxidation of diphosphenes [LGa(X)P]₂ to P-centered radicals cations 4a (X = Cl) and 4b (X = Br), in which the unpaired spin mainly reside at the carbene uncoordinated P-atoms.     

N,N,N′,N′-Tetramethylethylendiamin-di(tert-butyl)aluminium-Kationen — Molekülstruktur des [(Me3C)2Al · TMEDA]⊕[(Me3C)2AlBr2]⊖

(N,N,N′,N′ -tetramethylethylendiamine) di(tert-butyl)aluminium Cations — Molecular Structure of [(Me₃C)₂Al(TMEDA)]^⊕[(Me₃C)₂AlBr₂]^? Dimeric di(tert-butyl)aluminium halides (Me₃C)₂AlX (X = Cl, Br) react with N,N,N′,N′ -tetramethylethylendiamine (TMEDA) to give three compounds: the salt-like [(Me₃C)₂Al(TMEDA)]^⊕[(Me₃C)₂AlX₂]^? 1 , characterized by crystal structure determination, and [(Me₃C)₂Al(TMEDA)]^⊕X^? 3 both with chelating amine, and the more covalent, pentane soluble (Me₃C)₂AlX(TMEDA) 2 with TMEDA bound by only one nitrogen atom. The reaction resembles the symmetrical and unsymmetrical cleavage of diborane(6). 3 (X = Cl) is also formed by treatment of 1 with boiling n-hexane in the presence of TMEDA over a period of 24 hours, while for X = Br the more covalent 2 is the main product under similar conditions. In solution 2 decomposes slowly yielding different products in dependency of the solvent: in benzene 3 and in n-pentane 1 are formed.     

Trimethylaluminum mediated halomethylation of [(arene)2Fe]2+ cations

The arene salts [(arene)₂Fe](PF₆)₂ (arene = mesitylene 1a, and hexamethylbenzene, 1c) react readily with AlMe₃ in dichloromethane or dibromomethane to produce the novel exo-halomethyl-η⁵-cyclohexadienyl salts [(η⁵-exo-CH₂XC₆H₃Me₃)(η⁶-C₆H₃Me₃)Fe]PF₆ (X = Cl, 2d; X = Br, 2e) and [(η⁵-exo-CH₂XC₆Me₆)(η⁶-C₆Me₆)Fe]PF₆ (X = Cl, 2f; X = Br, 2g) which have been characterized spectroscopically and, in the case of 2f, crystallographically.     

Synthese et structure du sulfate double MSbF2SO4 (M = Rb,Cs)

The crystal structure of RbSbF₂SO₄ has been determined on a single crystal (R = 0.078 for 710 reflections). The structure shows sulfate anions distorted by the SOSb bonds. The antimony atom is from an SbF₂ unit. This antimony dihalogen is from the family of the $\text{1}\text{1}$ compounds which are in MX₃SbX₃ (M = Al, Ga, In) (X = Cl, Br) systems.     

Thermal and photochemical reactions of allylcobaloximes with para-substituted benzenesulphonyl chloride under aerobic and anaerobic conditions

The compounds p-XC₆H₄SO₂Cl (X = Cl, Br, I, OMe) react regiospecifically with allyl-, 2-methylallyl-, 3-methylallyl- and 3,3-dimethylallyl-cobaloximes under thermal and photochernical conditions. A rearranged organic product is obtained in each case. The yields are much better in photochemical reactions. A chain mechanism is involved in which the organosulphonyl radical and cobaloxime(II) are the chain propagating species. Yields of the sulphones are drastically reduced when the reactions are carried out in the presence of oxygen.     

Ligating properties of thionitrosoamines: III. Carbonyl complexes of rhodium(I) and rhodium(III) containing N-thionitrosodimethylamine

Me₂NNS reacts with [Rh(CO)₂Cl]₂ to produce the complex cis-Rh(SNNMe₂)(CO)₂Cl (1). The latter undergoes reversible CO substitution by Me₂NNS to give the complex trans-Rh(SNNMe₂)₂(CO)Cl (2a). Complexes 1 and 2a, in solution lose CO and Me₂NSS, respectively, to give the complex trans-(μ-Cl)₂[Rh(SNNMe₂)(CO)]₂ (3). Complex 1 can also be prepared by bubbling CO through a CH₂Cl₂ solution of Rh(SNNMe₂)(diene)Cl (diene = 1,5-cyclooctadiene (4a), norbornadiene (4b)) obtained by a bridge-splitting reaction of Me₂NNS with [Rh(diene)Cl]₂. 1 and 2a react with EPh₃ (E = P, As, Sb) to give the complexes trans-Rh(EPh₃)₂(CO)Cl. The complexes trans-Rh(E′Ph₃)₂(CO)X (X = Cl, E′ = As, Sb; X = Br, NCS, E′ = As) undergo reversible E′Ph₃ displacement upon treatment with Me₂NNS to give the complexes trans-Rh(SNNMe₂)₂(CO)X (X = Cl (2a), Br (2b), NCS (2c)). Oxidative additions of Br₂, I₂, or HgCl₂ to 2a produce stable adducts, while the reaction of 2a with CH₃I gives an inseparable mixture of the adduct Rh(SNNMe₂)₂(CO)(CH₃)ClI and the acetyl derivative Rh(SNNMe₂)₂(CH₃CO)ClI. A mixture of the acetyl derivative (μ-Cl)₂[Rh(SNNMe₂)(CH₃CO)I]₂ and the adduct (μ-Cl)₂[Rh(SNNMe₂)(CO)(CH₃)I]₂ is obtained by treating 1 with CH₃I. The IR spectra of all the compounds are consistent with S-coordination of Me₂NNS. Because of the restricted rotation around the NN bond, the ¹H NMR spectra of the new compounds exhibit two quadruplets in the range 3.5–4.3δ when ⁴J(HH) = 0.7–0.5 Hz. When ⁴J(HH) < 0.5 Hz, the perturbing effect of the quadrupolar relaxation of the ¹⁴N nucleus obscures the spin-spin coupling and two broad signals are observed in the range 3.6–4δ.     

The photodecomposition of platinacycloalkanes in solution.: I. 1,3-propanediylplatinum(IV) compounds

The gaseous products of the photolysis at 25°C of the platinacyclobutane compounds [X₂$\text{PtCH}{}_2\text{CH}{}_2\text{C}$H₂(N-N)] where X = Cl, Br and N-N = 1,10-phenanthroline, 2,2′-bipyridine, (CH₂NMe₂)₂, (C₅H₅N)₂ in several solvents, in the absence and presence of various additives, have been determined. With solvents of relatively low dielectric constant (e.g. CH₂Cl₂), over 85 mol % of the hydrocarbon products was propene, the formation of which appears to involve a direct transfer of a hydrogen atom between neighbouring groups in the ring. With solvents of relatively high dielectric constant (MeCN, Me₂SO) in the presence of species, e.g. I^?, SbPh₃, having a high trans effect, cyclopropane is the main volatile product. The effect of added halide ion and of the mixed solvents Me₂SO/PhMe and Me₂SO/PhSH indicates that ionisation of the platinacyclobutane and the formation of platinum substituted propyl ion-radicals precede the formation of cyclopropane (and the small amounts of ethylene produced).The photolysis of [X₂$\text{PtCH}{}_2\text{CH}{}_2\text{C}$H₂(MeCN)₂] in methyl cyanide solution in the presence of Et₃RNX′ (X′ = Cl, R = H; X′ = Br, R = Et) gives appreciable amounts of ethylene in the products (up to 25 mol %). It is suggested that the halide ions add to the platinum to give negatively charged platinacyclobutane species, the photodecomposition of which may give C₂H₄.     

The Cyclohexasilanes Si6H11X and Si6Me11X with X=F,Cl, Br and I: A Quantum Chemical and Raman Spectroscopic Investigation of a Multiple Conformer Problem

The conformers of the monohalocyclohexasilanes, Si₆H₁₁X (X=F, Cl, Br or I) and the haloundecamethylcyclohexasilanes, Si₆Me₁₁X (X=F, Cl, Br or I) are investigated by DFT calculations employing the B3LYP density functional and 6‐31+G* basis sets for elements up to the third row, and SDD basis sets for heavier elements. Five minima are found for Si₆H₁₁X—the axial and equatorial chair conformers, with the substituent X either in an axial or equatorial position—and another three twisted structures. The equatorial chair conformer is the global minimum for the X=Cl, Br and I, the axial chair for X=F. The barrier for the ring inversion is ～13 kJ mol^?1 for all four compounds. Five minima closely related to those of Si₆H₁₁X are found for Si₆Me₁₁X. Again, the equatorial chair is the global minimum for X=Cl, Br and I, and the axial chair for X=F. Additionally, two symmetrical boat conformers are found as local minima on the potential energy surfaces for X=F, Cl and Br, but not for X=I. The barrier for the ring inversion is ～14–16 kJ mol^?1 for all compounds. The conformational equilibria for Si₆Me₁₁X in toluene solution are investigated using temperature dependent Raman spectroscopy. The wavenumber range of the stretching vibrations of the heavy atoms X and Si from 270–370 cm^?1 is analyzed. Using the van′t Hoff relationship, the enthalpy differences between axial and equatorial chair conformers (H_ax?H_eq.) are 1.1 kJ mol^?1 for X=F, and 1.8 to 2.8 kJ mol^?1 for X=Cl, Br and I. Due to rapid interconversion, only a single Raman band originating from the “averaged” twist and boat conformers could be observed. Generally, reasonable agreement between the calculated relative energies and the experimentally determined values is found.     

Neutrale Bis‐Aziridin‐Komplexe des Typs [M(CO)3XAz2] (M = Mn,Re; X = Cl,Br; Az = N(H)C2H2Me2)

The pentacarbonylhalogene complexes [XM(CO)₅] (M = Mn, Re; X = Cl, Br) ( 1a – 2b ) react with 2,2‐dimethylaziridine by thermally induced substitution reaction to give the neutral bis‐aziridine complexes [M(X)(CO)₃Az₂] (Az = N(H)C₂H₂Me₂) ( 3a – 4b ). As a result of the X‐ray structure analyses, the metal atoms are octahedrally configurated in the facial arrangement; the intact three‐membered rings coordinate through their distorted tetrahedrally configurated N atoms. All compounds 3a – 4b are stable with respect to the directed thermal alkene elimination to give the corresponding nitrene complexes (CO)₄(X)M=NH; their IR, ¹H and ¹³C{¹H} NMR, and MS spectra are reported and discussed.     

Tris(trimethylsilyl)methanselenenylhalogenide und -chalkogenide

Tris(trimethylsilyl)methaneselenenyl Halides and Chalcogenides . Ditrisyldiselenide ( 1 ) (trisyl = TSi = (Me₃Si)₃C) reacts with SOCl₂, Br₂ and I₂ to provide trisylselenenyl halides TSiSeX ( 2 : X = Cl; 3 : X = Br, 4 : X = I). Insertion of S and Se into the Se? Se bond of 1 to yield (TSiSe)₂S_n ( 5 : n = 1; 6 : n = 2) and (TSiSe)₂Se_n ( 7 : n = 1; 8 : n = 2) was catalysed by iodine. 5 was isolated in pure state and examined by X-ray diffraction. Triselenide 7 can be cleaved by I₂ in CS₂ to give 4 and Se₂I₂ ( 9 ). From 2 with Me₃SiCN and Me₃SiNCS, the new selenenyl pseudohalides TSiSeCN ( 10 ) and TSiSeSCN ( 11 ) were prepared. The compounds were characterised by ¹H, ¹³C- and ⁷⁷Se n.m.r. spectra.     

A 29Si, 13C and 1H NMR study of the interaction of various halotrimethylsilanes and trimethylsilyl triflate with dimethyl formamide and acetonitrile,a comment on the nucleophile induced racemisation of halosilanes

The ²⁹Si, ¹³C and ¹H NMR spectra of $\text{1}\text{1}$ mixtures of Me₃SiI and Me₃SiOSO₂CF₃ with DMF in CD₂Cl₂ show signals that are consistent with the formation of Me₃SiO$\text{C}\text{+}$H(NMe₂)X^? but not with penta- or hexa-coordinate silicon species. The spectra of a $\text{1}\text{1}$ mixture of Me₃SiBr and DMF show a rapidly exchanging, equilibrium mixture of Me₃SiO$\text{C}\text{+}$H(NMe₂)Br^? and starting materials. No strong evidence for salt formation between DMF and Me₃SiCl was obtained. The spectra of Me₃SiX (X = I, Br, Cl, OSO₂CF₃) in CD₃CN indicate that neither adduct formation nor extra coordination at silicon is significant.     

Reaktionen von Bortrihalogeniden mit Tris-(trimethylsily)-amin

Interaction of Borontrihalides and Tris-(trimethylsilyl)-amine According to the reaction conditions and the used halides borontrihalides BX₃ (X = F, Cl, Br) and tris-(trimethylsily1)-amine, (Me₃Si)₃N, I, (Me ? CH₃—) interact to give MeBX₂, (Me₃Si)₂N? BMeX, (Me₃Si)₂N? BX₂ or mixtures of these compounds; e. g. BF₃, and I yield (Me₃Si)₂N? BF₂ and Me₃SiF, while BBr₃ and I at 23°C form MeBBr₂ and (Me₃Si)₂NSiMe₂Br. In addition the unknown aminoboranes (Me₃Si)₂N? BMe₂ and (Me₃Si)₂N? BMeBr were synthesized using a different route.