Silicon‐ and Tin‐Containing Open‐Chain and Eight‐Membered‐Ring Compounds as Bicentric Lewis Acids toward Anions

Herein, we report the syntheses of silicon‐ and tin‐containing open‐chain and eight‐membered‐ring compounds Me₂Si(CH₂SnMe₂X)₂ ( 2 , X=Me; 3 , X=Cl; 4 , X=F), CH₂(SnMe₂CH₂I)₂ ( 7 ), CH₂(SnMe₂CH₂Cl)₂ ( 8 ), cyclo‐Me₂Sn(CH₂SnMe₂CH₂)₂SiMe₂ ( 6 ), cyclo‐(Me₂SnCH₂)₄ ( 9 ), cyclo‐Me_(2?n)X_nSn(CH₂SiMe₂CH₂)₂SnX_nMe_(2?n) ( 5 , n=0; 10 , n = 1, X= Cl; 11 , n=1, X= F; 12 , n=2, X= Cl), and the chloride and fluoride complexes NEt₄[cyclo‐ Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?F] ( 13 ), PPh₄[cyclo‐Me(Cl)Sn(CH₂SiMe₂CH₂)₂Sn(Cl)Me?Cl] ( 14 ), NEt₄[cyclo‐Me(F)Sn(CH₂SiMe₂CH₂)₂Sn(F)Me?F] ( 15 ), [NEt₄]₂[cyclo‐Cl₂Sn(CH₂SiMe₂CH₂)₂SnCl₂?2 Cl] ( 16 ), M[Me₂Si(CH₂Sn(Cl)Me₂)₂?Cl] ( 17 a , M=PPh₄; 17 b , M=NEt₄), NEt₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?F] ( 18 ), NEt₄[Me₂Si(CH₂Sn(F)Me₂)₂?F] ( 19 ), and PPh₄[Me₂Si(CH₂Sn(Cl)Me₂)₂?Br] ( 20 ). The compounds were characterised by electrospray mass‐spectrometric, IR and ¹H, ¹³C, ¹⁹F, ²⁹Si, and ¹¹⁹Sn NMR spectroscopic analysis, and, except for 15 and 18 , single‐crystal X‐ray diffraction studies.     

Insertions of nitriles and pyridine into the ZrSi bond of (η5-C5H5)(η5-C5Me5)Zr[Si(SiMe3)3]Me

The zirconium silyl complex CpCpZr[Si(SiMe₃)₃]Me (1; Cp = η⁵-C₅H₅; Cp = η⁵-C₅Me₅) reacts with nitriles RCN (R = Me, CHCH₂, Ph) to form the azomethine derivatives CpCpZr[NC(R)Si(SiMe₃)₃]Me (2, R = Me; 3, R = CHCH₂; 4, R = Ph). Pyridine reacts with 1 to give a 75% yield of CpCpZr[NC₅H₅Si(SiMe₃)₃]Me (5), which results from 1,2-addition of the ZrSi bond of 1 to pyridine. These reactions provide the first examples of nitrile and pyridine insertions into a transition metal-silicon bond. The related silyl complexes Cp₂Zr[Si(SiMe₃)₃]Me and CpCpZr[Si(SiMe₃)₃]Cl are much less reactive toward nitriles and pyridine.     

NMR investigation of bis(2,3-alkanedione dioximato)-bis(pyridine)cobalt(III) iodide complexes: 1H and 13C NMR spectra and 13C spin-lattice relaxation time measurements

The complexes of trans-[Co(III)(R,CH₃-dioxH)₂(py)₂]I2 (R = CH₃, C₂H₅, n-C₃H₇ and n-C₄H₉) were investigated in solution by ¹H and ¹³C NMR spectra and ¹³C spin-lattice relaxation time measurements. The ¹H and ¹³C-resonances of the R = C₂H₅, n-C₃H₇ and n-C₄H₉) groups were shifted to higher field than those of the free ligands by the complexation; it was attributable to the ring current shielding due to the axial pyridine ligands of the complexes. ¹³C spin-lattice relaxation times were interpreted as due to movement of the axial pyridine ligands as if they twist around the CoN (pyridine nitrogen) bond axis and the above R groups were moving segmentally. These segmental movements allowed the R groups to approach closely toward the axial pyridine ring plane to experience the ring current shielding.     

Bildung siliciumorganischer Verbindungen. 66. (H2Si?CH2)2 und Si-substituierte Derivate

Formation of Organosilicon Compounds. 66. (H₂Si? CH₂)₂ and Si-substituted Derivatives (H₂Si? CH₂)₂ 1 is formed in the reaction of (Cl₂Si? CH₂)₂ with LiAlH₄. In 1 , the halogenation of the SiH bond is so much preferred compared to the ring cleavage reaction, that 1 reacts with Cl₂ or Br₂ to form successively all compounds form 1-monochlor-1,3-disilacyclobutane to (X₂Si? CH₂)₂ (X = Cl, Br). The stability of the 1,3-disilacyclobutane skeleton towards HBr or Br₂ increases as the electronegativity of the Si-substituents increases. Thus, (Cl₂Si? CH₂)₂ is cleaved neither by HBr nor by Br₂, whereas e. g. [H(C₆H₅)Si? CH₂]₂ reacts to [Br(C₆H₅)Si? CH₂]₂ with Br₂, but yields meH(C₆H₅)Si? CH₂? SiBr(C₆H₅)H (me = CH₃) with HBr. In [me(C₆H₅)Si? CH₂]₂, the four-membered ring is cleaved by Br₂ as well as by HBr. The ¹H-, ²⁹Si- and ¹³C-n.m.r. data are reported.     

Austauschreaktionen an komplexgebundenen liganden von elementen der IV. Hauptgruppe : II. Aminolyse von cyclopentadienyl-dicarbonyl-trichlorsilyl-eisen

The ¹H and ¹³C NMR spectra of the following six compounds have been examined over a wide range of temperatures: four derivatives of 3,5-dimethylpyrazole substituted at the nitrogen atom by organometallic groups such as Si(CH₃)₃ (I), Si(C₂H₅)₃ (II), Si(OC₂H₅)₃ (III), Ge(CH₃)₃ (IV), 3,5-dimethyl-1-trimethylsilyl-1,2,4-triazole (V) and 1-trimethylsilylimidazole (VI). Activation energies of the metal migration have been found for the compounds (I–V) by the total NMR line-shape analysis. Proton and carbon spectra of the compound (VI) show equivalence of the positions 4 and 5 in the imidazole ring. No temperature-dependent changes in the spectra were observed at –80 to +80°. These facts may be interpreted by assuming that the organometallic group undergoes an intermolecular exchange.     

A multinuclear NMR spectroscopy study of alkoxysilanes

¹⁷O, ²⁹Si, and ¹³C NMR spectra of more than 100 mono-, di-, tri- and tetra-alkoxysilanes R_4−nSi(OR′)_n; R = C_nH_2n+1, Ph, CH₂Cl, CH₂Br; R′ = C_nH_2n+1, CH₂Ph, CH₂CH₂Cl, CH₂CHCH₂, CH₂CCH, CH₂CF₃. (CH₂)₃Cl, (CH₂)₃CN have been studied.Linear relationships between the chemical shifts of ¹⁷O, ²⁹Si, ¹³C in alkoxysilanes and the inductive and steric constants of substituents R and R′ were observed. Different transmission of electronic effects along the SiO bond in various directions was revealed by means of ¹³C, ²⁹Si, ¹⁷O NMR spectroscopy and correlation analysis. The results are discussed in terms of (pd)_π-bonding between the oxygen and silicon atoms in compounds containing an SiO bond.     

Complexes of 1-(<Emphasis Type="Italic">N</Emphasis>-heterylmethyl)silatranes with metal chlorides

The hitherto unknown complexes of 1-(N-heterylmethyl)silatranes HetCH₂Si(OCH₂CH₂)₃N (Het is imidazolyl, 3,5-dimethylpyrazolyl, 1,2,4-triazolyl, benzimidazolyl, 1,2,3-benzotriazolyl) with chlorides of divalent metals MCl₂ (M = Cu, Zn, Cd, Co, Pd) of 1:1 composition are synthesized. The ligands are coordinated to the metal ion by the pyridine nitrogen atom of the azole heterocycle.     

2,2′-Bipyridyl formation from 2-arylpyridines through bimetallic diyttrium intermediate

An alkylyttrium complex supported by an N,N′-bis(2,6-diisopropylphenyl)ethylenediamido ligand, (ArNCH₂CH₂NAr)Y(CH₂SiMe₃)(THF)₂ (1, Ar = 2,6-ⁱPr₂C₆H₃), activated an ortho-phenyl C–H bond of 2-phenylpyridine (2a) to form a (2-pyridylphenyl)yttrium complex (3a) containing a five-membered metallacycle. Subsequently, a unique C(sp²)–C(sp²) coupling of 2-phenylpyridine proceeded through a bimetallic yttrium intermediate, derived from an intramolecular shift of the yttrium center to an ortho-position of the pyridine ring in 3a, to yield a bimetallic yttrium complex (4a) bridged by two-electron reduced 6,6′-diphenyl-2,2′-bipyridyl. Aryl substituents at the ortho-position of the pyridine ring were key in order to destabilize the μ,κ²-(C,N)-pyridyldiyttrium intermediate prior to the C(sp²)–C(sp²) bond formation.     

Cleavage of the Fe—Fe Bond of （Me2SiSiMe2） [η^5－C5H4Fe（CO）2]2 with Na／Hg and Molecular Structure of the Ring－Opened Complex

The reaction of the rifle cyclic complex (1) with sodium amalgam in THF resulted in the expected cleavage of the Fe-Fe bond to afford his-sodium salt ( Me2SiSiMe2 ) [η^5-C5H4Fe(CO)2]2 (4). The latter was not isolated and was used directly to react with MeI, PhCH2Cl, CH3C(O)Cl, PhC(O)Cl,Cy3SnCl (Cy= cyclohexyl) or Ph3SnCl to afford corresponding ring-opened derivatives (Me2SiSiMe2) [η^5-C5H4Fe(CO)2]2 [5, R=Me; 6, R=PhCH2; 7, R=CH3C(O); 8, R=PhC(O); 9, R = Cy3Sn or 10, R = Ph3Sn ]. The crystal and molecular structures of 10 were determined by X-ray diffraction analysis. The molecule took the desired ant/ conformation around the Si-Si bond. The length of the Si--Si bond is 0.2343(3)nm, which is essentially identical to that in the cyclic structure of 1[0.2346(4) tun]. This result unambiguously demonstrates that the Si--Si bond in the cyclic structure of 1 is not subject to obvious strain.     

Dynamic behavior of [(η-C5H4CH3)Cr(CO)2(μ-SBu)Pt(PPh3)2] in solution

The structure and dynamic behavior of complex [(η⁵-C₅H₄CH₃)Cr(CO)₂(μ-SBu)Pt(PPh₃)₂] in solution was studied by multinuclear (¹H, ¹³C, ³¹P) NMR spectroscopy including a phase-sensitive NOESY experiment. Increasing temperature causes rupture of the Cr-Pt bond in the three-membered ring of the complex and rotation of the S-Pt(PPh₃)₂ unit around the Cr-S bond line, followed by formation of a new Cr-Pt bond to close the ring. All activation parameters for this dynamic process have been determined.     

Ab initio study of mechanism of forming a silicic <Emphasis Type="Italic">bis</Emphasis>-heterocyclic compound between (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>Si=Si: and ethane

The mechanism of the cycloaddition reaction of forming a silicic bis-heterocyclic compound between singlet state (CH₃)₂Si=Si: and ethene has been investigated with the CCSD(T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction has one dominant reaction pathway. The presented rule of this dominant reaction pathway that the 3p unoccupied orbital of Si: in (CH₃)₂Si=Si: and the π orbital of ethane forming a π → p donor-acceptor bond, resulting in the formation of a three-membered ring intermediate (INT1); Then, INT1 isomerizes to a four-membered ring silylene (P1), which driven by ring-enlargement effect; Due to sp ³ hybridization of Si: atom in the four-membered ring silylene (P1), P1 further combines with ethene to form a silicic bis-heterocyclic compound (P2).     

Darstellung und charakterisierung von verbindungen des typs (CH3)3ME(CF3)2 (M = Si,Ge, Sn; E = P,As)

Various preparative routes for the synthesis of (CH₃)₃SiP(CF₃)₂ are discussed. The most favourable method, reaction of (CH₃)₃MPH₂ with HE(CF₃)₂, provides a good yield of (CH₃)₃ME(CF₃)₂ compounds (M = Si, Ge, Sn; E = P, As). The reaction rate is dependent on M (Si < Ge <Sn) und E (P < As). The stability and reactivity of the (CH₃)₃ME(CF₃)₂ compounds are discussed. The new compounds were characterized by NMR and IR spectra and by cleavage reactions of the M-E bond. ¹H, ¹⁹F NMR and IR spectral data are reported.     

An MP2 study on pre-reactive complexes (CH_2)_2O … XY (X,Y = H,F,Cl,Br,I)

The structures, energies, atomic chaiges and IR spectra of complexes (CH2)2O…XY (X, Y = H, F, Cl, Br, and I) have been examined by means of ab initio molecular orbital theory at the second-order level of Moller-Plesset perturbation correction. It is found that the hydrogen bond O…H-X is non-linear. The attraction between X and the H atoms in oxirane ring causes O…H-X bond bending. The hydrogen bond slighdy weakens the bond strength of C-O, and leads the bending and stretching mode of IR to shift to the red. The calculation results show that there is no evidence of a significant extent of proton transfer to give (CH2)2OH …X- in the isolated complexes.     

Etude spectroscopique de derives mercuriques d'amides-thiols: I. Spectres de vibration et structure des thiol-2 N-méthylacétamide,thiol-3 N-méthylpropanamide et N-(thiol-2 éthyle) acétamide

Raman and infrared spectra of CH₃NHCOCH₂SH, CH₃NHCO(CH₂)₂SH and CH₃CONH(CH₂)₂SH have been recorded between 3800 and 200 cm^?1. Some structural information is obtained from their analysis: for pure liquids or solids, molecules form linear chains with NH ? OC hydrogen bonds, the SH group being probably bound to the oxygen of an adjacent molecule. For CCl₄ solutions, an intramolecular hydrogen bond NH ? S is observed for the first compound only, corresponding to the formation of a five-membered ring.     

Organic Phosphorus Compounds 67. The exchange Cleavage of dialkylaminomethylphosphines with aryl and diarylphosphines [1]

Interaction of dialkylaminomethyl-substituted tertiary phosphines with primary or secondary phosphines results often in the cleavage of a P? C bond and the formation of P? P bonds. Thus treatment of Ph₂PCH₂NEt₂ with Ph₂PH at 180° yields Ph₂P? PPh₂ and HNEt₂, and interaction of PhP(CH₂NEt₂)₂ and PhPH₂ at 150° results in the formation of (PhP)₅, (PhP)₄ CH₂, HNEt₂ and CH₃NEt₂.     

Vinylic selenides

The ¹H, ¹³C and ²⁹Si NMR spectra of 1,3-dioxa-6-aza-2-silacyclooctanes (I) containing a transannular N → Si bond have been studied at different temperatures in solution. The sterically less crowded equatorial location of the Si substituent at the trigonal bipyramid (TBP) corresponds to the energetically unfavourable axial position in the eight-membered heterocycle (C₈). For this reason, the preferred orientation of the Si substituent and the conformational equilibrium of C₈ strongly depend on the energy of the N → Si bond. The C₈ of I in solution has the boat-chair (BC) and/or chair-chair (CC) conformations. The weakening of the N → Si bond leads to an increase in dihedral angle ?_ON and shifts the conformational equilibrium of C₈ to the CC form. The exchange between the Si substituent positions at the TBP, observed at low temperatures proceeds through the inversion of C₈ and requires dissociation of the N → S bond.     

Metal Complexes with Biologically Important Ligands. CLXVI Tetracarbonyl Complexes of Chromium(0) and Molybdenum(0) with Schiff Bases from Pyridine‐2‐carboxaldehyde and α‐Amino Acid Esters as N,N‐Chelate Ligands

The complexes [M(CO)₄(pyridyl‐CH=N‐CHRCO₂R′)] (M = Cr, Mo; R = H, CH₃, CH(CH₃)₂, CH₂CH(CH₃)₂) were obtained by reaction of the Schiff bases from pyridine‐2‐carboxaldehyde and glycine, L‐alanine, L‐valine or L‐leucine esters with the norbornadiene complexes [M(CO)₄(nbd)] and were characterized by IR, ¹H and ¹³C NMR and UV‐vis spectra. The deeply colored complexes exhibit solvatochromism.     

Synthesis and characterizations of bis(phenoxy)‐amine tin(II) complexes for ring‐opening polymerization of lactide

A series of tin(II) complexes supported by N₂O₂ bis(phenol)‐amine ligands were prepared from the reactions of the corresponding ligands with Sn[N(SiMe₃)₂]₂ in benzene at room temperature. The ligands were designed to have different substituted group at the ortho‐position on the aryl rings (R = ^tBu, CH₃) and N‐containing side arm (E = ? CH₂NEt₂ and pyridine) giving a variation of tin(II) complexes (R = ^tBu, E = CH₂NEt₂, 2a ; R = ^tBu, E = py, 2b ; R = CH₃, E = CH₂NEt₂, 2c ; R = CH₃, E = py, 2d ). All complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. The single‐crystal X‐ray crystallography revealed that all complexes have a monomeric four‐coordinate tin center with a distorted seesaw structure. All complexes are active for solvent‐free polymerization of l ‐lactide at 120 °C giving poly(l ‐lactide) with narrow to moderate dispersity (Ð = 1.12–1.56). In the presence of benzyl alcohol during the polymerization, the resulting polymer was found to be linear having benzyl alcohol as the end group while, in the absence of benzyl alcohol, the polymer was cyclic. The large ^tBu group at the ortho‐position was found to decrease polymerization activity while the more basic ? CH₂NEt₂ group was found to increase the polymerization activity. The polymerization of rac‐lactide under a similar condition gave PLA having a slight heterotactic bias for all catalysts. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2104–2112     

1/1-komplexe des trimethylphosphinimino-pentamethyldisiloxans und des bis(trimethylphosphinimino)-dimethylsilans mit aluminium-, gallium- und indiumtrimethy. Verbindungen mit stationärem bzw. Oszillierendem akzeptor

(CH₃)₃P&zdbnd;NSi(CH₃)₂OSi(CH₃)₃ reacts with (CH₃)₃Al, (CH₃₃Ga, or (CH₃)₃In to give rigid 1/1-adducts. On the contrary, the analogous 1/1-complexes of(CH₃)₃P&.zdbndNSi(CH₃)₂-N&.zdbndP(CH₃)₃ exhibit a nonrigid behavior as shown by the temperature dependence of the ¹H NMR spectra.     

The mass spectral fragmentation of 2,2′-bis-trimethylsilylbenzhydrylethers. An indication for transannular hydrogen/deuterium rearrangements and transannular elimination reactions

The mass spectra of the methyl-, trideuteromethyl-, ethyl- and pentadeuteroethylethers of 2,2′-bis-trimethylsilylbenzhydrol are reported. The most significant ions arise from the [M – CH₃]⁺ ion, formed by loss of a methyl radical from one of the trimethylsilyl groups. After ring formation by interaction of the siliconium ion centre with an aromatic nucleus, the ion loses (CH₃)₃Si? OR (R = CH₃, C₂H₅, CD₃ and C₂D₅), giving ion m/e 223. The fragment (CH₃)₃Si? OCH₃ is also eliminated in the four ethers investigated from the ion [M – R]⁺. Attack of the siliconium ion. Indications are found for a transannular hydrogen/deuterium rearrangement and a transannular elimination reaction. The intensity of some peaks in the spectra are discussed in relation to group R.