Hypervalent Organoselenium(II) Compounds with Organophosphorus Ligands. Crystal and Molecular Structure of [2‐(iPr2NCH2)C6H4]Se[S2PR′2] (R′ = Ph,OiPr)

Redistribution reactions between diorganodiselenides of type [2‐(R₂NCH₂)C₆H₄]₂Se₂ [R = Et, iPr] and bis(diorganophosphinothioyl disulfanes of type [R′₂P(S)S]₂ (R = Ph, OiPr) resulted in the hypervalent [2‐(R₂NCH₂)C₆H₄]SeSP(S)R′₂ [R = Et, R′ = Ph ( 1 ), OiPr ( 2 ); R = iPr, R′ = Ph ( 3 ), OiPr ( 4 )] species. All new compounds were characterized by solution multinuclear NMR spectroscopy (¹H, ¹³C, ³¹P, ⁷⁷Se) and the solid compounds 1 , 3 , and 4 also by FT‐IR spectroscopy. The crystal and molecular structures of 3 and 4 were determined by single‐crystal X‐ray diffraction. In both compounds the N(1) atom is intramolecularly coordinated to the selenium atom, resulting in T‐shaped coordination arrangements of type (C,N)SeS. The dithio organophosphorus ligands act monodentate in both complexes, which can be described as essentially monomeric species. Weak intermolecular S ··· H contacts could be considered in the crystal of 3 , thus resulting in polymeric zig‐zag chains of R and S isomers, respectively.     

Charge Effects in PCP Pincer Complexes of NiII bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis

This contribution reports on a new family of Ni^II pincer complexes featuring phosphinite and functional imidazolyl arms. The proligands ^RPIMC^HOP^R′ react at room temperature with Ni^II precursors to give the corresponding complexes [(^RPIMCOP^R′)NiBr], where ^RPIMCOP^R=κ^P,κ^C,κ^P‐{2‐(R′₂PO),6‐(R₂PC₃H₂N₂)C₆H₃}, R=iPr, R′=iPr ( 3 b , 84 %) or Ph ( 3 c , 45 %). Selective N‐methylation of the imidazole imine moiety in 3 b by MeOTf (OTf=OSO₂CF₃) gave the corresponding imidazoliophosphine [(^iPrPIMIOCOP^iPr)NiBr][OTf], 4 b , in 89 % yield (^iPrPIMIOCOP^iPr=κ^P,κ^C,κ^P‐{2‐(iPr₂PO),6‐(iPr₂PC₄H₅N₂)C₆H₃}). Treating 4 b with NaOEt led to the NHC derivative [(NHCCOP^iPr)NiBr], 5 b , in 47 % yield (NHCCOP^iPr=κ^P,κ^C,κ^C‐{2‐(iPr₂PO),6‐(C₄H₅N₂)C₆H₃)}). The bromo derivatives 3–5 were then treated with AgOTf in acetonitrile to give the corresponding cationic species [(^RPIMCOP^R)Ni(MeCN)][OTf] [R=Ph, 6 a (89 %) or iPr, 6 b (90 %)], [(^RPIMIOCOP^R)Ni(MeCN)][OTf]₂ [R=Ph, 7 a (79 %) or iPr, 7 b (88 %)], and [(NHCCOP^R)Ni(MeCN)][OTf] [R=Ph, 8 a (85 %) or iPr, 8 b (84 %)]. All new complexes have been characterized by NMR and IR spectroscopy, whereas 3 b , 3 c , 5 b , 6 b , and 8 a were also subjected to X‐ray diffraction studies. The acetonitrile adducts 6 – 8 were further studied by using various theoretical analysis tools. In the presence of excess nitrile and amine, the cationic acetonitrile adducts 6 – 8 catalyze hydroamination of nitriles to give unsymmetrical amidines with catalytic turnover numbers of up to 95.     

Methyl- and phenyl-bis(tertiary phosphine) N-bonded carboxamido complexes of platinum(II)

Methyl- or phenylN-carboxamido-complexes of platinum(II) Pt(NHCOR')RL₂ (L = PEt₃, R = Me, R′ = Me, CH = CH₂; L = PEt₃, R = Ph, R′ = Me; L = PMe₂Ph, R = Ph, R′ = Me, Ph; L = PMePh₂, R = Ph, R′ =₃, R = Ph, R′ = Me) have been prepared by the reaction of KOH with cationic nitrile complexes [PtR(NCR′)L₂]BF₄. Thermally unstable hydrido-N-carboxamido-complexes could be detected spectroscopically. IR and NMR (¹H, ³¹P) spectra of some of the complexes indicate the existence of a solvent- and temperature-dependent equilibrium between syn-and anti-isomers arising from restricted rotation about the NC bond of the carboxamido-group. The anti-isomer is favoured by nonpolar solvents and by increasing bulk of L. In the complex [PtH(NCCH CH₂)(PEt₃)₂]BF₄, IR and NMR spectra show acrlonitrile to be bound through nitrogen, not through the olefinic CC bond.     

Chelatkomplexe LM/n von Übergangsmetallen mit Iminophosphin-säureamidato-Liganden R2P(NR′)2– (= L)

Chelate Complexes LM/n of Transition Metals with Phosphinoimidic Amidato Ligands R₂P(NR′)₂^– (= L) Reaction of LLi with metal halides or metal halide complexes affords chelate complexes LM/n (L = R₂P(NR′)₂^–; M = Cr⁺⁺⁺, Co⁺⁺, Ni⁺⁺, Zn⁺⁺). With the bulky ligand t-Bu₂P(NSiMe₃)₂^– and Ni(PPh₃)₂Cl₂ or Ni(dme)Br₂ (dme = dimethoxyethane) only halide bridged chelates [LNiHal]₂ (Hal = Cl, Br) containing tetrahedral chromophors NiN₂Hal₂ were obtained. Main objects of investigation were the bischelates L₂Ni 2 . 2 a (R = i-Pr, R′ = Me) and 2 c (R = Ph, R′ = Et) are planar, 2 b (R = i-Pr, R′ = Et) and 2 d–g (R, R′ = i-Pr, i-Pr; Ph, i-Pr; Et, SiMe₃; Ph, SiMe₃) tetrahedral. In solutions of 2 b and 2 c a conformational equilibrium planar (diamagnetic) tetrahedral (paramagnetic) exists that is shifted to the right with increasing temperature and is dominated by the tetrahedral ( 2 b ) or planar conformer ( 2 c ) at room temperature. As is the case with the isovalence electronic compounds [R₂P(S)NR′]₂Ni small substituents R′ apparently favour the planar state and in contrast to some complexes [R₂P(O)NR′]₂Ni no paramagnetic planar species 2 have yet been observed. These findings that are derived from the results of magnetic measurements and of UV/VIS as well as NMR spectroscopy are confirmed by crystal structure determinations: 2 a was found to be planar (orthorhombic; a = 3382.8(11), b = 1124.0(4), c = 8874(3); P2₁2₁2; Z = 6), and 2 g to be tetrahedral (monocline; a = 1268.4(2), b = 1806.8(2), c = 1971.6(2), P2₁/n; Z = 4). The bite angle NNiN of the chelate ligand in 2 a (ca. 77°) is similar to those in paramagnetic planar complexes [R₂P(O)NR′]₂Ni (NNiO 74–77°) and shows that a small chelate bite does not necessarily imply paramagnetism of planar Ni(II) complexes.     

A Mild and Highly Efficient Catalyst for Beckmann Rearrangement, BF3·OEt2

BF₃·OEt₂ (Boron trifluoride etherate), an inexpensive and commercially easily available Lewis acid stoichiometrically employed for Beckamann rearrangement in general, was now found to efficiently catalyze Beckmann rearrangement of ketoximes into their corresponding amides (up to 99% yield) in anhydrous acetonitrile under reflux temperature.     

Interplay between Cationic and Neutral Species in the Rhodium‐Catalyzed Hydroaminomethylation Reaction

The reactivity of [Rh(CO)₂{(R,R)‐Ph? BPE}]BF₄ ( 2 ) toward amine, CO and/or H₂ was examined by high‐pressure NMR and IR spectroscopy. The two cationic pentacoordinated species [Rh(CO)₃{(R,R)‐Ph? BPE}]BF₄ ( 4 ) and [Rh(CO)₂(NHC₅H₁₀){(R,R)‐Ph‐BPE}]BF₄ ( 8 ) were identified. The transformation of 2 into the neutral complex [RhH(CO)₂{(R,R)‐Ph? BPE}] ( 3 ) under hydroaminomethylation conditions (CO/H₂, amine) was investigated. The full mechanisms related to the formation of 3 , 4 and 8 starting from 2 are supported by DFT calculations. In particular, the pathway from 2 to 3 revealed the deprotonation by the amine of the dihydride species [Rh(H)₂(CO)₂{(R,R)‐Ph? BPE}]BF₄ ( 6 ), resulting from the oxidative addition of H₂ on 2 .     

m‐Metallaphenol: Synthesis and Reactivity Studies

Treatment of the osmium complex [Os{CHC‐(PPh₃)CH(OH)‐η²‐C≡CH}(PPh₃)₂(NCS)₂] ( 1 ) with excess triethylamine produces the first m‐metallaphenol complex [Os{CHC(PPh₃)CHC(OH)CH}(PPh₃)₂(NCS)₂] ( 2 ). The NMR spectroscopic and structural data as well as the nucleus‐independent chemical‐shift (NICS) values suggest that osmaphenol 2 has aromatic character. The reactivity studies demonstrate that 2 can react with different isocyanates to form the annulation reaction products [Os{CHC(PPh₃)CHC(O?C?ONR)C}(PPh₃)₂(NCS)₂] (R=Ph ( 3 ), iPr ( 7 ), Bn ( 8 )) via the carbamate intermediates [Os{CHC(PPh₃)CHC(O‐C?ONHR)CH}(PPh₃)₂(NCS)₂] (R=Ph ( 4 ), iPr ( 5 ), Bn ( 6 )). In addition, the similar annulation reactions can be extended to other unsaturated compounds containing N–C multiple bonds, for example, isothiocyanates, pyridine, and sodium thiocyanate, which can produce the corresponding fused osmabenzene complexes. In contrast, the reactions of 2 with common electrophiles, such as NOBF₄, NO₂BF₄, N‐bromosuccinimide, and N‐chlorosuccinimide only led to the decomposition of the metallaphenol ring. The experimental results suggest that 2 is very electrophilic and readily reacts with nucleophiles, which is mainly due to the metal center and the strong electron‐withdrawing phosphonium group.     

Double stereoselective coordination of chiral N,S ligands: Synthesis,coordination chemistry and utilization in Pd‐catalyzed allylic alkylation

A series of chiral pentane‐2,4‐diyl‐based thioether‐amine ligands [ 4 and 5 ; (R,S)‐ and (S,S)‐R¹SCH(CH₃)CH₂CH(CH₃)NHR², respectively, where 4a R¹ = iPr, R² = Ph; 4b R¹ = tBu, R² = Ph; 4c R¹ = 1‐Ad, R² = Ph; 5a R¹ = iPr, R² = Ph; 5b R¹ = tBu, R² = Ph; 5c R¹ = 1‐Ad, R² = Ph; 5d R¹ = iPr, R² = 4‐MeOC₆H₄; 5e R¹ = iPr, R² = 4‐MeC₆H₄; 5f R¹ = iPr, R² = 3,5‐Me₂C₆H₃] with stereogenic S‐ and N‐donor atoms has been prepared starting from cyclic sulfates via optically pure γ‐aminoalcohol or 2,4‐dimethylazetidine intermediates. The synthesis of the novel diastereomerically related ligand sets 4 and 5 was accomplished starting from the same source of chirality. The modular ligand structure and the novel synthetic strategies developed for their synthesis allowed the easy modification of the ligands’ (i) S‐ and (ii) N‐substituents, as well as (iii) the relative stereochemistry within the ligand backbone. Six‐membered [Pd(N,S)Cl₂]‐type chelate complexes of the diastereomerically related ligands 4a and 5a were synthesized and characterized by X‐ray crystallography in the solid phase, by density functional theory calculations and in solution by NMR spectroscopy. The coordination of 5a resulted in the formation of a single chair conformation by the stereospecific locking of both stereolabile (N and S) donor atoms. In contrast, compound 4a forms rapidly equilibrating palladium species due to the fast inversion of the sulfur donor. Ligands with stereochemically fixed donor atoms provided robust and efficient catalytic systems that can be effectively applied in alkylene carbonates as green reaction media. Remarkably, the phosphine‐free catalysts are air‐stable, and at room temperature in the presence of moisture gave excellent ee’s (up to 93%) in asymmetric allylation processes thanks to the double stereoselective coordination.     

Enol ethers and acetals: acylation with dichloroacetyl,acetyl and benzoyl chloride in ionic liquid medium

Synthesis of 4-alkoxy-1,1-dichloro-3-alken-2-ones [CHCl₂C(O)C(R²)C(R¹)-OR, where R, R¹, R² = Et, H, H; Me, Me, H; Et, H, Me; Me, –(CH₂)₂–; Me, –(CH₂)₃–; Et, Et, H; Et, Bu, H; Et, i-Pr, H; Et, i-Bu, H; Me, Ph, H; Me, thien-2-yl, H] from acylation of enol ethers and acetals with dichloroacetyl chloride, in ionic liquid ([BMIM][BF₄] or [BMIM][PF₆]) is reported. The synthesis of alkenones [R³–C(O)C(R²)C(R¹)-OR], where R/R¹/R²/R³ = Et/H/H/Ph, t-Bu/H/H/Ph, Me/-(CH₂)₄/Ph, Me/-(CH₂)₄/Me] from the reaction of enol ethers with benzoyl chloride or acetyl chloride, in ionic liquid [BMIM][BF₄], is also reported. Last products are described for the first time.     

P‐Aminophosphaalkenes with C‐Isopropyldimethylsilyl Groups

Amination of the C‐isopropyldimethylsilyl P‐chlorophosphaalkene (iPrMe₂Si)₂C=PCl ( 1 ) leads to the P‐aminophosphaalkenes (iPrMe₂Si)₂C=PN(R)R′ (R, R′ = Me ( 2 ), R = H, R′ = nPr ( 3 ), R = H, R′ = iPr ( 4 ), R = H, R′ = tBu ( 5 ), R = H, R′ = 1‐Ada ( 6 ), R = H, R′ = CPh₃ ( 7 ), R = H, R′ = Ph ( 8 ), R = H, RR′ = 2,6‐iPr₂Ph (= DIP) ( 10 ), R = H, R′ = 2,4,6‐Me₃Ph (= Mes) ( 11 ), R = H, R′ = 2,4,6‐tBu₃Ph (= Mes*)] ( 12 ), R = H, R′ = SiMe₃ ( 13 ), and R, R′ = SiMe₂Ph (1 4 ). ³¹P‐NMR spectra confirm that phosphaalkenes 2 – 7 and 10 – 14 are monomeric in solution; the structures of 7 , 10 , and 12 were determined by X‐ray crystallography. Freshly prepared (iPrMe₂Si)₂C=PN(H)Ph ( 8 ) is a monomer that dimerizes with (N→C) proton migration within several hours to the stable diazadiphosphetidine [(iPrMe₂Si)₂CHPNPh]₂ ( 9 ). NMR‐scale reactions of deprotonated 5 and 13 with tBuiPrPCl provide by P–P bond formation the P‐phosphanyl iminophosphoranes [(iPrMe₂Si)₂C=](RN=)PPtBu(iPr) [R = tBu ( 15 ), R = Me₃Si ( 17 )]. Deprotonated 5 and Me₃GeCl deliver by N–Ge bond formation the aminophosphaalkene (iPrMe₂Si)₂C=PN(tBu)GeMe₃ ( 20 ), which with elemental selenium 5 undergoes (N→C) proton migration to form the alkyl(imino)(seleno)phosphorane [(iPrMe₂Si)₂CH](tBuN=)P=Se ( 21 ), which is a selenium‐bridged cyclic dimer in the solid state.     

Neue Aminometallane des Aluminiums und Galliums

New Aminometalanes of Aluminum and Gallium The reaction of secondary amines R′RNH with trimethyaluminum leads to the formation of dimeric aminoalanes [RR′NAlMe₂]₂ ( 1 ) (R = 2,6-Me₂C₆H₃, R′ = SiMe₂(2,4,6-Me₃C₆H₂)) and 2 (R = Ph, R′ = SiMe₃). Using a different stoichiometric ratio, a monomeric aminoalane [RR′N]₂AlMe ( 3 ) (R = Ph, R′ = SiPh₂Me) is obtained, having an aluminum atom of coordination number three due to the steric demand of the substituents. The synthesis of the corresponding aminogallanes 4 , 5 and 6 is achieved by reaction of lithium amides LiNRR′ (R = Ph, 2,6-iPr₂C₆H₃; R′ = SiMe₃, SiMe₂iPr) with dimethylgalliumchloride, Me₂GaCl, in n-hexane. The formation of the dimeric species is in 1 through carbon while that in 2 and 3 is formed through nitrogen. The X-ray single crystal structure analysis of 1 , 2 , 3 and 4 are reported.     

Reactions of methylchlorodisilanes with Grignard reagents

Reactions of Cl₂MeSiSiMeCl₂ with RMgCl make it possible to obtain and isolate pure disilanes containing a smaller number of functional groups, namely, RMeClSiSiMeCl₂ (R = Ph), RMeClSiSiMeRCl (R = Prⁱ, Ph), and R₂MeSiSiMeRCl (R = Buⁱ). The reaction of Cl₂MeSiSiMeCl₂ with BuⁿMgCl is the least selective. The chlorides obtained were reduced with LiAlH₄ into the corresponding hydrides.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 954–957, May, 1995.     

Platinum(II) Mixed Ligand Complexes with Thiourea Derivatives,Dimethyl Sulphoxide and Chloride: Syntheses,Molecular Structures,and ESCA Data

The platinum(II) mixed ligand complexes [PtCl(L^1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R₂NC(S)NHC(O)R′ (R = Et, R′ = p‐O₂N‐Ph: HL¹; R = Ph, R′ = p‐O₂N‐Ph: HL²; R = R′ = Ph: HL³; R = Et, R′ = o‐Cl‐Ph: HL⁴; R₂N = EtOC(O)N(CH₂CH₂)₂N, R′ = Ph: HL⁵) and Et₂NC(S)N=CNH‐1‐Naph (HL⁶), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L^{1, 2})₂] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, ¹H‐NMR, ¹³C‐NMR, as well as X‐ray structure analysis ([PtCl(L¹)(dmso)] and [PtCl(L^{3, 4})(dmso)]) and ESCA ([PtCl(L^{1, 2})(dmso)] and [Pt(L^{1, 2})₂]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the Pt^II atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO₂, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f_7/2 electron binding energies of the complexes [PtCl(L^{1, 2})(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L^{1, 2})₂]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.     

Dialkyl- and diaryl-platinum(II) complexes with secondary phosphines: Preparation,structure and thermal reaction giving the metallopolymer

Alkyl and arylplatinum complexes with 1,5-cyclooctadiene ligand, [PtR₂(cod)] (R = Me, Ph, C₆H₄-p-CF₃, C₆F₅), react with secondary phosphines, PHR′₂ (R′ = i-Bu, t-Bu, Ph), to afford the mononuclear platinum complexes, cis-[PtR₂(PHR′₂)₂] (1a: R = Me, R′ = i-Bu; 1b: R = Me, R′ = t-Bu; 1c: R = Me, R′ = Ph; 2a: R = Ph, R′ = i-Bu; 2b: R = Ph, R′ = t-Bu; 2c: R = R′ = Ph; 3a: R = C₆H₄-p-CF₃, R′ = i-Bu; 3b: R = C₆H₄-p-CF₃, R′ = t-Bu; 3c: R = C₆H₄-p-CF₃, R′ = Ph; 4a: R = C₆F₅, R′ = i-Bu; 4c: R = C₆F₅, R′ = Ph) in 81–98% yields. Molecular structures of the complexes except for 1a, 1c and 2a were determined by X-ray crystallography. Complex 1b has a square-planar structure with Pt–C(methyl) bonds of 2.083(8) and 2.109(8) Å, while the Pt–C(aryl) bonds of 2b–c, 3a–c, 4a and 4c (2.055(1)–2.073(8) Å) are shorter than them. Thermal decomposition of 1b, 2a–c, and 3a–c releases methane, biphenyl or 4,4′-bis(trifluoromethyl)biphenyl as the organic products, which are characterized by NMR spectroscopy. The solid product of the thermal reactions of 2b and 2c were characterized as the metallopolymers formulated as [Pt(PR′₂)₂]_n (5b: R′ = ^tBu; 5c: R′ = Ph), based on the solid-state NMR and elemental analyses.     

Monomere Dialkylmetallkomplexe des Typs R2M(NR′)2XR mit M = Al,Ga, In,TI; X = S,C und R,R′ = Alkyl und Silyl

Monomeric Dialkyl Metal Complexes of the R₂M(NR′)₂XR Type with M = Al, Ga, In, Tl; X = S, C and R, R′ = Alkyl and Silyl N,N′-Bis(trimethylsilyl)sulfurdiimide reacts with the trimethyl derivatives of aluminium, gallium, and indium within insertion. Hereby monomeric sulfinic acid imidamidates Me₂M(NSiMe₃)₂SMe (Me = CH₃) are formed. The lithium amidinates Li(NR′)₂CMe (R′ = i-C₃H₇ and SiMe₃) are formed likewise by insertion reactions with LiMe and the corresponding carbodiimides R′N?C?NR′ and were used in reactions with R₂MCl (M = Al to Tl) to synthesize dialkyl metal amidinates R₂M(NR′)₂CMe. The NMR (¹H and ¹³C) and the vibrational spectra (IR and Raman) are discussed and applied to describe the structure of these chelat complexes.     

A facile synthesis of 3‐Substituted 5‐Oxo‐1,2,4‐thiadiazoles from amidoximes

The reaction of amidoximes 1 with 1,1′‐thiocarbonyldiimidazole (TCDI) followed by treatment with silica gel or boron trifluoride diethyl etherate (BF₃·OEt₂) provided 3‐substituted 4,5‐dihydro‐5‐oxo‐1,2,4‐thiadiazoles 2 in moderate yields. The Lewis acids are considered to promote the rearrangement of the thioxocarbamate intermediates 5 to the thiol carbarn ate intermediates 7 , which cyclize to afford 4,5‐dihydro‐5‐oxo‐1,2,4‐thiadiazoles 2 .     

O-Alkyl Trithiophosphate Derivatives of Triorganotin(IV) and S-Alkyl Trithiophosphate Derivatives of Diorganotin(IV) Chloride

Reactions of triorganotin chlorides with potassium salt of O-alkyl trithiophosphate [ROP(S)(SK)₂; R = Me, Prⁱ, Ph] in 2:1 molar ratio in anhydrous benzene yield triorganotin O-alkyl trithiophosphate of the type ROP(S) [SSnR′₃]₂ R = Me, Prⁱ; Ph, R′ = Prⁿ, Buⁿ, Ph] which are found to be monomeric in nature. These complexes are soluble in common organic solvents. Similar reactions of diorganotin chloride with dipotassium salt of S-alkyl trithiophosphate yield diorganotin-S-alkyl trithiophosphate of the type [(RS)P(O)S₂]₂SnR′₂; R = Me, Prⁱ; R′ = Me, Et, Ph, which also are found to be monomeric in nature and are soluble in common organic solvents. The newly synthesized derivatives have been characterized by physicochemical and spectroscopic techniques, IR, NMR (¹H, ³¹P, and ¹¹⁹Sn).     

Effect of catalysts on asymmetric induction cationic copolymerization of l-menthyl vinyl ether with indene

Cationic copolymerization of l-menthyl vinyl ether (l-MVE) with indene (IN) was carried out with several catalysts in toluene (Tol) at 0°C. The catalysts used were BF₃OEt₂, CH₃COClO₄, and SnCl₄. l-Menthyl residue, an optically active side chain of the copolymer obtained, was removed with dry hydrogen bromide gas by the ether cleavage reaction. Ether-cloven copolymers [vinyl alcohol(VA)–IN] also had optical rotation. The efficiency of asymmetric induction to the polymer main chain was in the order of BF₃OEt₂ > CH₃COClO₄ > SnCl₄.     

Organometallic and organobimetallic complexes of platinum(II) containing 2,2′-bipyrimidyl: syntheses and spectroscopic characteristics

Preparations are described of several monometallic complexes (bipym)PtR₂ [bipym = 2,2′-bipyrimidyl; R = Me, CF₃, Ph, 1-adamantylmethyl (adme); R₂ = (CH₂)₄] and bimetallic analogues R₂Pt(μ-bipym)PtR′₂ [R = R′ = CH₃, C₆H₅, adme; R = CH₃, R′ = Ph, adme, CF₃]. IR, ¹H NMR and UV/visible spectroscopic characteristics of the two modes of bipyrimidyl coordination are discussed.     

Two‐Coordinate Magnesium(I) Dimers Stabilized by Super Bulky Amido Ligands

A variety of very bulky amido magnesium iodide complexes, LMgI(solvent)_0/1 and [LMg(μ‐I)(solvent)_0/1]₂ (L=‐N(Ar)(SiR₃); Ar=C₆H₂{C(H)Ph₂}₂R′‐2,6,4; R=Me, Prⁱ, Ph, or OBu^t; R′=Prⁱ or Me) have been prepared by three synthetic routes. Structurally characterized examples of these materials include the first unsolvated amido magnesium halide complexes, such as [LMg(μ‐I)]₂ (R=Me, R′=Prⁱ). Reductions of several such complexes with KC₈ in the absence of coordinating solvents have afforded the first two‐coordinate magnesium(I) dimers, LMg?MgL (R=Me, Prⁱ or Ph; R′=Prⁱ, or Me), in low to good yields. Reductions of two of the precursor complexes in the presence of THF have given the related THF adduct complexes, L(THF)Mg?Mg(THF)L (R=Me; R′=Prⁱ) and LMg?Mg(THF)L (R=Prⁱ; R′=Me) in trace yields. The X‐ray crystal structures of all magnesium(I) complexes were obtained. DFT calculations on the unsolvated examples reveal their Mg?Mg bonds to be covalent and of high s‐character, while Ph???Mg bonding interactions in the compounds were found to be weak at best.