Elimination Of Me3SiCl Research Articles

Carbene-Stabilized Phosphagermylenylidene: A Heavier Analog of Isonitrile.

Phosphagermylenylidenes (R-P═Ge), as heavier analogs of isonitriles, whether in their free state or as complexes with a Lewis base, have not been previously identified as isolable entities. In this study, we report the synthesis of a stable monomeric phosphagermylenylidene within the coordination sphere of a Lewis base under ambient conditions. This species was synthesized by Lewis base-induced dedimerization of a cyclic phosphagermylenylidene dimer or via Me3SiCl elimination from a phosphinochlorogermylene framework. The deliberate integration of a bulky, electropositive N-heterocyclic boryl group at the phosphorus site, combined with coordination stabilization by a cyclic (alkyl)(amino)carbene at the low-valent germanium site, effectively mitigated its natural tendency toward oligomerization. Structural analyses and theoretical calculations have demonstrated that this unprecedented species features a P═Ge double bond, characterized by conventional electron-sharing π and σ bonds, complemented by lone pairs at both the phosphorus and germanium atoms. Preliminary reactivity studies show that this base-stabilized phosphagermylenylidene demonstrates facile release of ligands at the Ge atom, coordination to silver through the lone pair on P, and versatile reactivity including both (cyclo)addition and cleavage of the P═Ge double bond.

A Robust, Divalent, Phosphaza-bicyclo[2.2.2]octane Connector Provides Access to Cage-Dense Inorganic Polymers and Networks

While polymers containing chain or ring motifs in their backbone are ubiquitous, those containing well-defined molecular cages are very rare and essentially unknown for the inorganic elements. We report that a rigid and dinucleophilic cage (PNSiMe3)2(NMe)6, which is chemically robust and accessible on a multi-gram scale from commercial precursors, serves as a linear and divalent connector that forms cage-dense inorganic materials. Reaction of the cage with various ditopic P(III) dihalide comonomers proceeded via Me3SiCl elimination to give high molecular weight (30 000-70 000 g mol-1), solution-processable polymers that form free-standing films. The end groups of the polymers could be tuned to engender orthogonal reactivity and form block copolymers. Networked cage-dense materials could be accessed by using PCl3 as a tritopic P(III) linker. Detailed mechanistic studies implicate a stepwise polycondensation that proceeds via phosphino-phosphonium ion intermediates, prior to Me3SiCl loss. Thus, metathesis between the dinucleophilic cage and polyhalides represents a general strategy to making cage-dense polymers, setting the stage for systematically understanding the consequences of the three-dimensional microstructure on macroscopic material properties.

Introducing N-Heterocyclic Iminophosphoranes (NHIPs): Synthesis by [3 + 2] Cycloaddition of Azophosphines with Alkynes and Reactivity Studies

Azophosphines (Ar-N═N-PR2) were prepared from N-aryl-N'-(trimethylsilyl)diazenes (Ar-N═N-SiMe3) and R2PCl by Me3SiCl elimination or oxidation of phosphinohydrazines (Ar-NH-NH-PR2) by 2,5-dialkyl-1,4-benzoquinones. Azophosphines underwent 1,3-dipolar cycloaddition with cyclooctyne and dimethylacetylene dicarboxylate to give N-heterocyclic iminophosphoranes (NHIPs), which are structurally similar to cyclic (alkyl)(amino)carbenes. The cycloaddition reaction is compatible with various phosphorus atom substituents including phenyl (NHIP-1,4,6), isopropyl (NHIP-2), cyclohexyl (NHIP-3), and dimethylamino (NHIP-5) groups. The pKBH+ values of the NHIPs in acetonitrile range from 13.13 to 23.14. On the basis of the Huynh electronic parameter, NHIP-1 and NHIP-2 have σ-donor strengths comparable with that of 1,8-diazabicyclo[5.4.0]undec-7-ene. NHIP-1 underwent facile 1,2-addition with pentafluoropyridine to form a rare fluorophosphorane. The treatment of NHIP-1 with triphenylsilane resulted in P-N bond cleavage, accompanied by the reduction of phosphorus(V) to phosphorus(III). A homoleptic, cationic CuI-NHIP-1 complex was also prepared. The potential utility of π-donating NHIPs was demonstrated by the stabilization of a reactive iminoborane (Cl-B≡N-SiMe3). The facile scalable synthesis, tunability of steric demands, and basicity of NHIPs suggest that this new heterocycle class may find a wide range of applications in synthetic chemistry.

Chalcogen‐Pnictogen Complexes of Anionic N‐Heterocyclic Carbenes with a Weakly Coordinating Borate Moiety

AbstractChalcogen‐pnictogen dihalide complexes which bear an anionic N‐heterocyclic carbene ligand with a tethered weakly coordinating borate moiety (WCA‐IDipp, WCA=B(C6F5)3, IDipp=1,3‐bis(2,6‐diisopropyphenyl)imidazolin‐2‐ylidene) were isolated and fully characterized. The metathesis reaction between the lithium salts [{(WCA‐IDipp)E}Li(toluene)] (E=S, Se) and pnictogen trihalides E′X3 (E=P, As, Sb; X=Cl, Br) afforded the complexes of the general type (WCA‐IDipp)E−E′X2 (E=S, Se; E=P, As, Sb; X=Cl, Br). In contrast, lithium chloride elimination was not observed with BiCl3 under the same reaction conditions and instead, the lithium complexes [{(WCA‐IDipp)E−BiCl3}Li(thf)4] (E=S, Se) were obtained. However, the corresponding bismuth dichloride derivatives (WCA‐IDipp)E−BiCl2 were accessible from the reaction of (WCA‐IDipp)ESiMe3 with BiCl3 upon Me3SiCl elimination.

Phosphanylphosphido and phosphanylphosphinidene complexes of zirconium(IV) supported by bidentate N,N ligands

Phosphanylphosphido complexes of zirconium, [NacNacZrCl2(η2-R2P–PSiMe3)] (R=t-Bu, i-Pr), were synthesized in the reaction of R2P–P(SiMe3)Li·nTHF (R=t-Bu, i-Pr) with a β-diketiminate complex, [NacNacZrCl3], in toluene. Elimination of Me3SiCl from [NacNacZrCl2(η2-R2P–PSiMe3)] provided the phosphanylphosphinidene complexes [NacNacZrCl(η2-R2P–P)] (R=t-Bu, i-Pr). Moreover, the reaction of [NacNacZrCl2(η2-R2P–PSiMe3)] with R2P–P(SiMe3)Li·nTHF yielded the phosphanylphosphinidenoid complexes [NacNacZrCl2(η2-R2P–PLi)] (R=t-Bu, i-Pr). The same reaction, but in the presence of 12-crown-4, gave rise to the phosphanylphosphinidene complexes [NacNacZrCl(η2-R2P–P)]. The X-ray structures of [NacNacZrCl2(η2-i-Pr2P–PSiMe3)] and [NacNacZrCl(η2-t-Bu2P–P)] revealed that the R2P-P ligands exhibit side-on coordination to the metal center. From the reaction of i-Pr2P–P(SiMe3)Li·3THF with [{PhN(CH2)3NPh)}ZrCl2], a triple-core, anionic, phosphanylphosphinidene complex, [{PhN(CH2)3NPh)}Zr3Cl2(μ2-Cl)(μ2-i-Pr2P–P)2(μ3-i-Pr2P–P)2]−[Li(DME)3]+, was obtained in which the i-Pr2P–P ligands exhibit bridging coordination.

Synthesis and structures of titanium(IV) imido complexes with dianionic ligands of triazapentadienyl derivatives

The reaction of PhN(Li)SiMe3 with dimethylcyanamide or 1-piperidinecarbonitrile and further with one third equiv of TiCl4(THF)2 led via Me3SiCl elimination to novel five-coordinate titanium(IV) triazapentadienates L1L2TiCl (L1 = [N(Ph)C(R)NC(R)N(R′)]−, L2 = [N(Ph)C(R)NC(R)N]2−; 1, R = dimethylamino, R′ = H; 2, R = 1-piperidino, R′ = SiMe3; 3, R = dimethylamino, R′ = SiMe3). The crystal structure studies of 1–3 revealed dianionic triazapentadienate binding of the metal center. The very short bond length of TiN implies the multiple bond character and imido feature of the ligand. The catalytic activity of selected complexes 1 and 2 in the polymerization of ethylene is reported.

Base-Stabilized Phosphinidene Boranes by Silylium-Ion Abstraction.

We report the preparation of N-heterocyclic carbene (NHC)-stabilized compounds containing P=B double bonds. The reaction of the highly functionalized phosphinoborane Mes*(SiMe3 )P-B(Cl)Cp* with Lewis bases allows access to base-stabilized phosphinidene boranes Mes*P=B(L)Cp* (L=4-dimethylaminopyridine (DMAP), NHC) by Me3 SiCl elimination. The formation of these species is shown to proceed through transient borylphosphide anions generated by Me3 Si abstraction.

Thorium Triamidoamine Complexes: Synthesis of an Unusual Dinuclear Tuck-in–Tuck-over Thorium Metallacycle Featuring the Longest Known Thorium−σ-Alkyl Bond

We report the synthesis and characterization of a range of thorium(IV)–halide, −amide, and −alkyl complexes supported by a sterically demanding triamidoamine ligand. Reaction of [ThCl4(THF)3.5] with [Li3(TrenDMBS)(THF)3] (TrenDMBS = N(CH2CH2NSiMe2But)3) gave [Th(TrenDMBS)(Cl)(THF)] (1), which was converted to [Th(TrenDMBS)(I)] (2), with concomitant elimination of Me3SiCl, by treatment with Me3SiI. Treatment of 2 with [LiNEt2] afforded [Th(TrenDMBS)(NEt2)] (3), or treatment with [PhCH2K] produced the dimeric tuck-in–tuck-over alkyl complex [Th{N(CH2CH2NSiMe2But)2(CH2CH2NSiMeBut-μ-CH2)}]2 (4), which features the longest reported Th−σ-alkyl bond distance of 2.875(9) Å. Reaction of 4 with [Et3NH][BPh4] to give the putative separated ion pair complex [Th(TrenDMBS)][BPh4] resulted in an intractable product mixture. In order to furnish a greater understanding of the latter reaction, the solvent-separated ion pair complex [U(TrenDMBS)(NCMe)2][BPh4] (5) was prepared from the monomeric uranium analogue of 4, [U{N(CH2CH2NSiMe2But)2(CH2CH2NSiMeBut-μ-CH2)}] (I), to provide a related model complex and to examine potential routes to useful TrenDMBS–actinide precursors. The nascent reactivity of 4 is suggested by the isolation of a small quantity of the oxo-insertion product [Th{N(CH2CH2NSiMe2But)2(CH2CH2NSiMeButCH2-μ-O)}]2 (6) when 4 is stored in diethyl ether. The complexes have been variously characterized by single-crystal X-ray diffraction, NMR spectroscopy, FTIR spectroscopy, Evans method solution magnetic moment determination, and CHN elemental analyses.

New route to access an acyl-functionalized phosphasilene and a four-membered Si-P-C-O heterocycle.

An acyl-functionalized phosphasilene, LSi(COtBu)=P(SiMe3) (L = PhC(NtBu)2) was synthesized on a new route by the addition of tBuCOCl to the phosphinosilylene LSiP(SiMe3)2 and subsequent Me3SiCl elimination. DFT studies elucidated its molecular structure, the influence of the acyl group on UV/Vis transitions, and revealed the mechanism. The intermediate LSi(COtBu)ClP(SiMe3)2, with a five-coordinate silicon center, was characterized by NMR spectroscopy and X-ray analysis. On the other hand, phosphasilene LSi(SiMe3)=P(SiMe3) reacted with tBuCOCl by a [2+2] cycloaddition of the silicon-phosphorus double bond and the carbon-oxygen double bond in addition to Me3SiCl elimination, thereby affording the novel, fully characterized compound LSi(SiMe3)[P=C(tBu)O] bearing a Si-P-C-O heterocycle with a phosphorus-carbon double bond. DFT studies suggest that two mechanisms occur simultaneously.

Azidophosphenium Cations: Versatile Reagents in Inorganic Synthesis

This work describes the synthesis and characterization of a series of iminophosphorane-substituted phosphenium cations of the type [R2NPNP(Cl)2NPNR'2][GaCl4] [R = iPr; R' = iPr (7[GaCl4]), SiMe3 (8)], which are directly derived from azidophosphenium salt [iPrNPN3][GaCl4] (2iPr[GaCl4]) and the corresponding chlorophosphane R2NPCl2. The reactivity of 7[GaCl4] toward 2,3-dimethylbutadiene (dmb) and 2,2'-bipyridine (bipy) was investigated, resulting in the formation of 7-dmb[GaCl4] and 7-Cl. In addition, self-condensation of [(Me3Si)2NPN3][GaCl4] (2SiMe3[GaCl4]) was studied in detail, and [(Me3Si)2NPNP(XY)N(SiMe3)2][GaCl4] [X = Cl; Y = Cl (13), N3 (14)] were determined as products on the basis of (31)P NMR spectroscopy. The reaction of 2SiMe3[GaCl4] with [(Me3Si)2NPCl][GaCl4] (1SiMe3[GaCl4]) yielded an unprecedented bicyclic 1,3,2λ(3),4λ(5)-diazadiphosphetidine (15), which was formed via a GaCl3-assisted Me3SiCl elimination starting from 13. Furthermore, cations of the type [R2NPNPR'3][GaCl4] [R = iPr; R' = cHex (19)] were obtained by the effective combination of 2R[GaCl4] (R = iPr, SiMe3) with PR'3 (R' = Ph, cHex). Azidochlorophosphanes R2NP(N3)Cl [R = iPr, SiMe3 (20R)] are shown to be accessible when 2R[GaCl4] was combined with bipy. All new compounds were fully characterized by means of X-ray, vibrational spectroscopy, CHN analysis, and NMR experiments. All compounds were further investigated by means of density functional theory, and the bonding situation was accessed by natural bond orbital analysis.

The Reactivity of Silylated Amino(dichloro)phosphanes in the Presence of Silver Salts

New cyclic and acylic phosphorus-nitrogen compounds have been synthesized in reactions of Hyp-N(SiMe3)PCl2 (hypersilyl = Hyp = (Me3Si)3Si) with silver salts of the perfluorinated anions [CF3CO2](-), [CF3SO3](-), and [C6F5](-). Depending on the choice of the silver salt, not only AgCl but also Me3SiCl elimination could be observed, leading to a transient highly reactive 1,3 dipole molecule. This 1,3 dipole molecule was found to be a key species, which can undergo [3 + 2] cyclization, when a dipolarophile such as acetonitrile is present. Also, dimerization or even cyclo-tetramerization are observed. The occurrence of different reaction channels demonstrates that the hypersilyl moiety can act as a highly reactive functional group. All new compounds have been characterized by single-crystal X-ray diffraction studies.

Diatomic PN – trapped in a cyclo-tetraphosphazene

(Me3Si)2NPCl2, which is formally capable of eliminating two equivalents of Me3SiCl, is shown to be a suitable starting material to prepare highly reactive PN species by successive elimination of Me3SiCl. Me3SiCl elimination can be triggered either thermally and/or by addition of a Lewis acid such as GaCl3, thus leading to the formation of a highly labile aminochlorophosphenium cation in [(Me3Si)2NPCl][GaCl4] and iminophosphenium salt [Me3Si–NP][GaCl4] upon warming to ambient temperatures. This work describes the synthesis and characterization of a cyclo-tetraphosphazane in [PN(dmb)]4 (5) (dmb = 2,3-dimethyl-1,3-butadiene) obtained by thermal elimination of Me3SiCl from (Me3Si)2NPCl2 at 120 °C in toluene solution. The reactive intermediate Me3SiNPCl was trapped with dmb to form the cyclic phosphazane Me3SiN(dmb)PCl, which eventually oligomerizes to give 5. In the presence of dmb or chd (chd = 1,3-cyclohexadiene) (Me3Si)2NP(OTf)2 reacts by eliminating Me3SiOTf to yield the spirocyclic phospholenium salts [Me3SiN(dmb)P(dmb)][OTf] (7) and [Me3SiN(chd)P(chd)][OTf] (8), of which the solid state structures were successfully determined. 7 decomposes when exposed to moisture to give an unprecedented cyclic ammonium phosphinoxide [P(O)H(dmb)2NH2][OTf] (9). Tetraphosphazane 5 is shown to be a versatile ligand in transition metal chemistry. It coordinates in an η3-fashion in {[PN(dmb)]4Mo(CO)3} (5·Mo) and is able to coordinate a second metal fragment, exemplified by the formation of the ditungsten complex{[PN(dmb)]4W2(CO)7} (5·W2) with a semi-bridging carbonyl ligand. All compounds were structurally characterized and the bonding situation was investigated by density functional theory and natural bond orbital analysis (NBO).

Synthesis of 1,3-Dichloro-cyclo-1,3-diphosphadiazanes from Silylated Amino(dichloro)phosphanes

The synthesis of 1,3-dichloro-cyclo-1,3-diphosphadiazanes [ClP(μ-NR)]2 via elimination of Me3SiCl from silylated amino(dichloro)phosphanes, R-N(SiMe3)PCl2, was studied by different synthetic protocols starting from R-N(H)SiMe3 (R = Si(SiMe3)3 = Hyp, N(SiMe3)2, Mes* = 2,4,6-tri-tert-butylphenyl, Ter = 2,4-bis(2,4,6-trimethylphenyl)phenyl, Dipp = 2,6-diisopropylphenyl, Dmp =2,6-dimethylphenyl, Ad = Adamantyl, Trityl = Ph3C, Tos = tosyl = CH3C6H4SO2, n-Oct = n-octyl, and Me3Si). A new synthetic route using trimethylsilyl-substituted amino(dichloro)phosphanes, R-N(SiMe3)PCl2, was developed to form cyclo-diphosph(III)-azanes simply by adding a mixture of R(f)OH/base (R(f)OH = hexafluoroisopropanole). By this method electron-rich/-poor aryl-, silyl-, and bissilylamino-substituted cyclo-diphosph(III)-azanes are accessible such as the unprecedented (Me3Si)2N-substituted species [ClP(μ-NN(SiMe3)2)]2 starting from tris(trimethylsilyl)hydrazine and PCl3. Additionally, the difficulties with the preparation of cyclo-diphosphadiazanes depending on the starting materials, solvents, and bases due to the competition of different reaction channels are studied.

Reactions of the Disilane Me3SiSiCl3 with P‐Chlorophosphaalkenes: Transient and Persistent Per‐Silylated Phosphaalkenes

AbstractReactions of P‐chlorophosphaalkenes (RMe2Si)2C=PCl (1a: R = Me; 1b: R = Ph) with the disilane Me3SiSiCl3 (5) furnish diphosphenes (Cl3Si)(RMe2Si)2C–P=P–C(SiCl3)(SiMe2R)2 (4a: R = Me; 4b: R = Ph) by Me3SiCl elimination. The structure of the new compound 4b was confirmed by X‐ray diffraction; it displays crystallographic inversion symmetry. Monitoring the reactions with 31P‐ and 29Si‐NMR spectroscopy detected P‐(trichlorosilyl)phosphaalkenes (RMe2Si)2C=PSiCl3 (2a, R = Me; 2b, R = Ph) as the primary intermediates from reductive P‐silylation of 4a, 4b, and P‐[(trichlorosilyl)phosphanyl]phosphaalkenes (RMe2Si)2C=P–P(SiCl3)C(SiCl3)(SiMe2R)2 (3a: R = Me; 3b: R = Ph) as unsymmetric dimerisation products that rearrange to provide 4a, 4b in step III of the reaction sequence. This step (the P→C 1,3‐trichlorosilyl shift reaction) was mimicked by the synthesis of (Me3Si)2C=P–P(SiCl3)tBu (7), which rearranges into an unsymmetric diphosphene tBuP=PC(SiMe3)2SiCl3 (8). The bulkier P‐chlorophosphaalkene (iPrMe2Si)2C=PCl (1c) reacts with 5, eliminates Me3SiCl and thereby provides the first persistent acyclic per‐silylated phosphaalkene (iPrMe2Si)2C=PSiCl3 (2c) in an incomplete reaction. 2c exhibits an exceptionally large NMR coupling 1J(31P,29Si) = ±249 Hz. Within weeks, the mixtures of 1c and 2c undergo decomposition with loss of the P=C functions.

The potential energy surface of the triazadiphosphole formation

The formal GaCl3-assisted [3+2] cycloaddition of two (Me3Si)2N–N(SiMe3)–PCl2 molecules resulting in the formation of a triazadiphosphole has been studied by means of B3LYP/6-31G(d,p) computations. These calculations revealed a stepwise reaction mechanism starting from the disguised 1,3-dipole and dipolarophile (Me3Si)2N–N(SiMe3)–PCl2. Comparison of the potential energy surface for the formation of a triazadiphosphole in the presence and without a Lewis acid indicate, that addition of a Lewis acid such as GaCl3 decreases the activation barriers to Me3Si–Cl elimination, in accord with experiment.

Staudinger Reaction as a Way Out To Avoid Cyclization in the Reaction of Silylated Dichloro(hydrazino)phosphane with Trimethylsilyl Azide

AbstractReaction of dichloro‐N,N′,N′‐[tris(trimethylsilyl)]hydrazinophosphane (1) with Me3SiN3 leads after an initial chlorine/azide exchange in a Staudinger reaction to a new phosphorus azide. The in situ formed phosphoranimine reacts with GaCl3 by Me3SiCl elimination, resulting in a phosphoranimino–dichlorogallane, which dimerizes to a Ga2N2‐four‐membered ring. The overall reaction at ambient temperature represents a fast and clean high‐yielding reaction (reaction time 2 h). The dimer of the formed azido–phosphoranimino–dichlorogallane was fully characterized and shown to be stable to temperatures above 103 °C.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Transition‐Metal‐Free Boron–Carbon Bond Activation: Insertion of an NNP Fragment into a Boron–Carbon Bond

AbstractThe influence and reactivity of fluorine‐containing Lewis acids such as neat BF3, BF3·OEt2, and B(C6F5)3 on Me3SiCl elimination in (Me3Si)2N–N(SiMe3)–PCl2 was investigated. The reaction with B(C6F5)3 resulted in the formation of a novel diazadiphosphetidine with a phosphorus(III) atom attached to a pentafluorophenyl group, which can be regarded as a formal NNP fragment insertion into a B–C bond.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Boron and Aluminum Complexes of Sterically Demanding Phosphinimines and Phosphinimides

Reactions of sterically demanding phosphinimines R3PNH [R=i-Pr (1), t-Bu (2)] were examined. Reactions with B(C6F5)3 formed the adducts (R3PNH)B(C6F5)3 [R=i-Pr (3), t-Bu (4)] in high yield. On the other hand, 2 reacts with HB(OBu)2, evolving H2 to give t-Bu3PNB(OBu)2 (5). The reaction of 2 equiv of 2 with BH3.SMe2 affords the species (t-Bu3PN)2BH (6). In contrast, the reaction of n-Bu(t-Bu)2PNH with BH3.SMe2 results in the formation of the robust adduct n-Bu(t-Bu)2PNH.BH3 (8). An alternative route to borane-phosphinimide complexes involves Me3SiCl elimination, as exemplified by the reaction of BCl2Ph with n-Bu3PNSiMe3, which gives the product n-Bu3PNBCl(Ph) (9). The corresponding reactions of the parent phosphinimines 1 and 2 with AlH3.NMe2Et give the dimers [(mu-i-Pr3PN)AlH2]2 (10) and [(mu-t-Bu3PN)AlH2]2 (11). Species 11 reacts further with Me3SiO3SCF3 to provide [(mu-t-Bu3PN)AlH(OSO2CF3)]2 (12). The reaction of the lithium salt [t-Bu3PNLi]4 (13) with BCl3 proceeds smoothly to give t-Bu3PNBCl2 (14), which is readily alkylated to give t-Bu3PNBMe2 (15). Subsequent reaction of 15 with B(C6F5)3 results in methyl abstraction and the formation of [(mu-t-Bu3PN)BMe]2[MeB(C6F5)3]2 (16). The reaction of 13 in a 2:1 ratio with BCl3 gives the salt [(t-Bu3PN)2B]Cl (17). This species can be methylated to give (t-Bu3PN)2BMe (18), which undergoes subsequent reaction with [Ph3C][X] (X=[B(C6F5)4], [PF6]) to form the related salts [(t-Bu3PN)2B][B(C6F5)4] (19) and [(t-Bu3PN)2B][PF6] (20), respectively. Analogous reactions with [Ph3C][BF4] afforded [t-Bu3PNBF2]2 (21). Compounds 3, 4, 6, 8, 11, 12, 17, 19, and 21 were characterized by X-ray crystallography.

Decomposition of [2-Pyr(SiMe3)2C]2SbCl into the Stibaalkene [2-Pyr(SiMe3)2C−SbC(SiMe3)2-Pyr]: Solid, Solution, and ab Initio Study

The disubstituted antimony chloride complex [2-Pyr(SiMe3)2C]2SbCl (Pyr = C5H4N), formed from the 2:1 reaction of [2-Pyr(SiMe3)2CLi·tmeda] with SbCl3, readily decomposes into the stibaalkene species [2-Pyr(SiMe3)2CSbC(SiMe3)2-Pyr] via β-elimination of Me3SiCl. The stibaalkene species is an intensely colored, highly air and moisture sensitive, deep red oil. In thf solution the elimination of Me3SiCl occurs at temperatures ca. −40 °C; however, orange crystals of [2-Pyr(SiMe3)2C]2SbCl were obtained from an Et2O solution maintained at −25 °C and the structure was determined by single-crystal X-ray diffraction. 1H and 13C NMR spectra of the crystals of [2-Pyr(SiMe3)2C]2SbCl have been obtained in d8-toluene at −30 °C, and its decomposition to the stibaalkene was followed by recording spectra as the sample was warmed to 30 °C. DFT ab initio calculations have been conducted to investigate the role of the pyridyl groups in Me3SiCl elimination as well as the structure and stability of the final stibaalkene. These in...

Supported Constrained-Geometry Catalysts on Cross-Linked (Aminomethyl)polystyrene: Studies of Ethylene and 1-Octene Polymerizations

The reaction of TiCl4 with (chlorodimethylsilyl)(trimethylsilyl)cyclopentadiene results in the chemoselective elimination of Me3SiCl and cleanly affords ((chlorodimethylsilyl)cyclopentadienyl)titanium trichloride (2). Likewise, the reaction of TiCl4 with (chlorodimethylsilyl)(trimethylsilyl)tetramethylcyclopentadiene (6) also results in the chemoselective elimination of Me3SiCl and cleanly affords ((chlorodimethylsilyl)tetramethylcyclopentadienyl)titanium trichloride (7). This observation is in sharp contrast to the reaction of 6 with ZrCl4, which results in the chemoselective elimination of Me3SiCl but affords a mixture of half-sandwich and zirconocene complexes. Support of complex 2 or 7 on (aminomethyl)polystyrene (AMPS, 1% cross-linking, 1.3 wt % N, 0.928 mmol of N/g of support), where the mole ratio of amine content of the support to precursor catalysts was selected to be 3:1, leads to the assembly of the constrained-geometry catalyst (CGCs) 8 or 9, respectively. From the 29Si NMR, the presence of a ...