Iminophosphines: synthesis, formation of 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and N-(pyridin-2-yl)-2-diphenylphosphinoylaniline, coordination chemistry and applications in platinum group catalyzed Suzuki coupling reactions and hydrosilylations

The aprotic and protic bi- and multidentate iminophosphines 2-Ph₂PC₆H₄N=CR¹R² (R¹=H, R²=Ph=2a; R¹=Me R²=Ph=2b; R¹=H, R²=2-thienyl=2c; R¹=H, R²=C₆H₄-2-PPh₂=2d; R¹=H, R²=C₆H₄-2-OH=2e, R¹=H, R²=C₆H₄-2-OH-3-Bu^t=2f; R¹=H, R²=CH₂C(O)Me=2g) have been prepared by the acid catalyzed condensation of 2-(diphenylphosphino)aniline with the corresponding aldehyde–ketone. Iminophosphine 2d can be reduced with sodium cyanoborohydride to give the corresponding amino-diphosphine 2-Ph₂PC₆H₄N(H)CH₂C₆H₄-2-PPh₂ (2h). In the presence of a stoichiometric quantity of acid, 2-(diphenylphosphino)aniline reacts in an unexpected manner with benzaldehyde, salicylaldehyde, or acetophenone to give the corresponding 2,3-dihydro-1H-benzo[1,3]azaphosphol-3-ium salts and with pyridine-2-carboxaldehyde to give N-(pyridin-2-ylmethyl)-2-diphenylphosphinoylaniline, the latter of which has been characterized by single-crystal X-ray crystallography, as its palladium dichloride derivative. The attempted condensation of 2-(diphenylphosphino)aniline with pyridine-2-carboxaldehyde to give the corresponding pyridine-functionalized iminophosphine resulted in an unusual transformation involving the diastereoselective addition of two equivalents of aldehyde to give 1,2-dipyridin-2-yl-2-(o-diphenylphosphinoyl)phenylamino-ethanol, which has been characterized by a single-crystal X-ray structure determination. The bidentate iminophosphine 2-Ph₂PC₆H₄N=C(H)Ph reacts with [(cycloocta-1,5-diene)PdClX] X=Cl, Me) to give [Pd{2-Ph₂PC₆H₄N=C(H)Ph}ClX] and the imino-diphosphine 2-Ph₂PC₆H₄N=C(H)C₆H₄-PPh₂ reacts with [(cycloocta-1,5-diene)PdClMe] to give [Pd{2-Ph₂PC₆H₄N=C(H)C₆H₄---PPh₂}ClMe] and each has been characterized by single-crystal X-ray crystallography. The monobasic iminophosphine 2-Ph₂PC₆H₄N=C(Me)CH₂C(O)Me reacts with [Ni(PPh₃)₂Cl₂] in the presence of NaH to give the phosphino–ketoiminate complex [Ni{2-Ph₂PC₆H₄N=C(Me)CHC(O)Me}Cl], which has been structurally characterized. Mixtures of iminophosphines 2a–h and a palladium source catalyze the Suzuki cross coupling of 4-bromoacetophenone with phenyl boronic acid. The efficiency of these catalysts show a marked dependence on the palladium source, catalysts formed from [Pd₂(OAc)₆] giving consistently higher conversions than those formed from [Pd₂(dba)₃] and [PdCl₂(MeCN)₂]. Catalysts formed from neutral bi- and terdentate iminophosphines 2a–d gave significantly higher conversions than those formed from their monobasic counterparts 2e–f. Notably, under our conditions the conversions obtained with 2a–c compare favorably with those of the standards; catalysts formed from tris(2-tolyl)phosphine and tris(2,4-di-tert-butylphenyl)phosphite and a source of palladium. In addition, mixtures of [Ir(COD)Cl]₂ and 2a–h are active for the hydrosilylation of acetophenone; in this case catalysts formed from monobasic iminophosphines 2e–f giving the highest conversions.     

Tridentate chelate π-bonded complexes of rhodium(I), iridium(I), and iridium(III) and chelate σ-bonded complexes of nickel(II), palladium(II), and platinum(II) formed by intramolecular hydrogen abstraction reactions

2,2′-Bis(o-diphenylphosphino)bibenzyl, o-Ph₂PC₆H₄CH₂CH₂C₆H₄PPh₂-o (bdpbz), is dehydrogenated by various rhodium complexes to give the planar rhodium(I) complex

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, from which the ligand, 2,2′-bis(o-diphenylphosphino)-trans-stilbene (bdpps) can be displaced by treatment with sodium cyanide. The stilbene forms stable chelate olefin complexes with planar rhodium(I) and iridium(I) and with octahedral iridium(III). On reaction with halide complexes of nickel(II), palladium(II) or platinum(II), the stilbene ligands

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(R = Ph or o-CH₃C₆H₄) lose a vinyl proton in the form of hydrogen chloride to give chelate, planar σ-vinyls of general formula =CHC₆H₄PR₂-o) (M = Ni, Pd, Pt; X = Cl, Br, I) of high thermal stability; analogous methyl derivatives =CHC₆H₄PR₂-o) are obtained from Pt(CH₃)₂(COD) (COD = 1,5-cyclooctadiene) and the stilbene ligands. The bibenzyl also forms chelate σ-benzyls HCH₂C₆H₄PPh₂-o) (M = Pd, Pt; X = Cl, Br, I). The ¹H NMR spectra of the o-tolyl methyl groups in the compounds =CHC₆H₄PR₂-o) (M = Ni, Pd, Pt; R = o-CH₃C₆H₄) vary with temperature, probably as a consequence of interconversion of enantiomers arising from restricted rotation about the M---P and M---C bonds. Possible mechanisms for the dehydrogenation reactions are briefly discussed.     

Structure and Bonding in Bis(1‐naphthyl) Diselenide and Bis{[2‐(N,N‐dimethylamino)methyl]phenyl} Tetraselenide,and Their Brominated Derivatives

The formation and crystal structures of bis(1‐naphthyl) diselenide ( 1 ) and bis{[2‐(N,N‐dimethylamino)methyl]phenyl} tetraselenide ( 2 ) are described. Whereas 1 can be produced in good yields, 2 is formed only as a minor product together with the known main product, bis{[2‐(N,N‐dimethylamino)methyl]phenyl} diselenide. The composition of the reaction mixture is semi‐quantitatively estimated by ⁷⁷Se NMR spectroscopy and DFT calculations. The effect of the n²→σ*(Se–Se) and π→σ*(Se–Se) secondary bonding interactions on the Se–Se bonds is discussed both by DFT calculations and comparison with literature, as available. The bromination of 1 yields monomeric (1‐naphthyl)selenenyl bromide ( 3 ) in good yields. That of the reaction mixture of (C₆H₄CH₂NMe₂)Se_x (x = 2–4) and Se₈ afforded (C₆H₄CH₂NMe₂H)₂[SeBr₄] ( 4 ) and (C₆H₄CH₂NMe₂H)₂[SeBr₆] ( 5 ) in addition to (C₆H₄CH₂NMe₂)SeBr, which has been previously reported.     

Methyl-oxygen bond cleavage in hemilabile phosphine-ether ligand of ruthenium(II) complexes

The preparation and characterization are described for four ruthenium(II) complexes containing hemilabile phosphine-ether ligand o-(diphenylphosphino)anisole (Ph₂PC₆H₄OMe-o) and/or bidentate ligand diphenylphosphino-phenolate ([Ph₂PC₆H₄O-o]⁻) Ru(RCN)₂(κ²-Ph₂PC₆H₄O-o)₂ (1a: R = Me; 1b: R = Et) and [Ru(RCN)₂(κ²-Ph₂PC₆H₄O-o)(κ²-Ph₂PC₆H₄OMe-o)](PF₆) (2a: R = Me; 2b: R = Et). The ruthenium(II) phosphine-ether complexes undergo mild methyl-oxygen bond cleavage. Two different kinds reaction mechanism are proposed to describe the methyl-oxygen bond cleavage, one involving attack of anionic nucleophiles and another involving the phosphine. The new reactions define novel routes to phosphine-phenolate complexes. The structures of complexes 1a, 1b and 2a were confirmed by X-ray crystallography.     

Chemie polyfunktioneller Moleküle. 119 [1] Tetracarbonyl-dicobalt-tetrahedran-Komplexe mit den Liganden Bis(diphenyl-phosphanyl)amin, 2-Butin-1,4-diol und tert-Butylphosphaacetylen — Kristallstrukturanalyse des Phosphaalkin-Derivats

Chemistry of Polyfunctional Molecules. 119 [1]. Tetracarbonyl-dicobalt-tetrahedrane Complexes with the Ligands Bis(diphenylphosphanyl)-amine, 2-Butin-1,4-diol, and tert.-Butylphosphaacetylene — Crystal Structure of the Phosphaalkyne Derivative Co₂(μ-CO)₂(CO)₄(μ-Ph₂P? NH? PPh₂—P,P′) · 1/2C₆H₅CH₃ ( 4 · 1/2C₆H₅CH₃) reacts with 2-butine-1,4-diol, HOCH₂? C?C? CH₂OH ( 5 ), to the dark-red tetrahedrane complex Co₂(CO)₄(μ-η²,η²-HOCH₂? C?C? CH₂OH? C², C³) · (μ-Ph₂P? NH? PPh₂? P,P′) · THF (6 · THF). With t-butyl-phosphaacetylene, tBu? C?P ( 7 ), 4 · THF forms Co₂(CO)₄(μ-η²,η²-tBu? C?P)(μ-Ph₂P? NH? PPh₂? P,P′) ( 8 ), which also belongs to the tetrahydrane type. The compounds were characterized by their mass, IR, ³¹P{¹H} NMR, ¹³C{¹H} NMR, and¹H NMR spectra. Crystals suitable for X-ray structure analyses have been obtained for 8 from dioxane. The dark red blocks crystallize in the monoclinic P2₁/c space group with the lattice constants a = 1404,1(5), b = 1330,0(7), c = 2578,8(10)pm; β = 90,82(3)°.     

Rare‐Earth‐Metal–Hydrocarbyl Complexes Bearing Linked Cyclopentadienyl or Fluorenyl Ligands: Synthesis,Catalyzed Styrene Polymerization,and Structure–Reactivity Relationship

A series of rare‐earth‐metal–hydrocarbyl complexes bearing N‐type functionalized cyclopentadienyl (Cp) and fluorenyl (Flu) ligands were facilely synthesized. Treatment of [Y(CH₂SiMe₃)₃(thf)₂] with equimolar amount of the electron‐donating aminophenyl‐Cp ligand C₅Me₄H‐C₆H₄‐o‐NMe₂ afforded the corresponding binuclear monoalkyl complex [({C₅Me₄‐C₆H₄‐o‐NMe(μ‐CH₂)}Y{CH₂SiMe₃})₂] ( 1 a ) via alkyl abstraction and C? H activation of the NMe₂ group. The lutetium bis(allyl) complex [(C₅Me₄‐C₆H₄‐o‐NMe₂)Lu(η³‐C₃H₅)₂] ( 2 b ), which contained an electron‐donating aminophenyl‐Cp ligand, was isolated from the sequential metathesis reactions of LuCl₃ with (C₅Me₄‐C₆H₄‐o‐NMe₂)Li (1 equiv) and C₃H₅MgCl (2 equiv). Following a similar procedure, the yttrium‐ and scandium–bis(allyl) complexes, [(C₅Me₄‐C₅H₄N)Ln(η³‐C₃H₅)₂] (Ln=Y ( 3 a ), Sc ( 3 b )), which also contained electron‐withdrawing pyridyl‐Cp ligands, were also obtained selectively. Deprotonation of the bulky pyridyl‐Flu ligand (C₁₃H₉‐C₅H₄N) by [Ln(CH₂SiMe₃)₃(thf)₂] generated the rare‐earth‐metal–dialkyl complexes, [(η³‐C₁₃H₈‐C₅H₄N)Ln(CH₂SiMe₃)₂(thf)] (Ln=Y ( 4 a ), Sc ( 4 b ), Lu ( 4 c )), in which an unusual asymmetric η³‐allyl bonding mode of Flu moiety was observed. Switching to the bidentate yttrium–trisalkyl complex [Y(CH₂C₆H₄‐o‐NMe₂)₃], the same reaction conditions afforded the corresponding yttrium bis(aminobenzyl) complex [(η³‐C₁₃H₈‐C₅H₄N)Y(CH₂C₆H₄‐o‐NMe₂)₂] ( 5 ). Complexes 1 – 5 were fully characterized by ¹H and ¹³C NMR and X‐ray spectroscopy, and by elemental analysis. In the presence of both [Ph₃C][B(C₆F₅)₄] and AliBu₃, the electron‐donating aminophenyl‐Cp‐based complexes 1 and 2 did not show any activity towards styrene polymerization. In striking contrast, upon activation with [Ph₃C][B(C₆F₅)₄] only, the electron‐withdrawing pyridyl‐Cp‐based complexes 3 , in particular scandium complex 3 b , exhibited outstanding activitiy to give perfectly syndiotactic (rrrr >99 %) polystyrene, whereas their bulky pyridyl‐Flu analogues ( 4 and 5 ) in combination with [Ph₃C][B(C₆F₅)₄] and AliBu₃ displayed much‐lower activity to afford syndiotactic‐enriched polystyrene.     

Synthese,Röntgenstrukturanalyse und Multikern‐NMR‐spektroskopische Untersuchung einiger intramolekular stickstoffstabilisierter Bor‐, Aluminium‐ und Galliumorganyle

Synthesis, X‐Ray Structure, and Multinuclear NMR Investigation of some intramolecularly Nitrogen stabilized Organoboron, ‐aluminum, and ‐gallium Compounds The intramolecularly nitrogen stabilized organoaluminum‐ and organoboron compounds Me₂Al(CH₂)₃NMe₂ ( 1 ), Me₂AlC₁₀H₆‐8‐NMe₂ ( 2 ), ⁱPr₂Al(CH₂)₃NEt₂ ( 3 ), (CH₂)₅Al(CH₂)₃NMe₂ ( 4 ), and (CH₂)₅B(CH₂)₃NMe₂ ( 5 ) are synthesized from Me₂AlCl and the corresponding organolithium compounds and from AlCl₃ or BCl₃, the lithium alkyl and ⁱPrMgCl or BrMg(CH₂)₅MgBr, respectively. AlCl₃ and GaCl₃ react with Li(CH₂)₃NMe₂ or LiCH₂CHMeCH₂NMe₂ forming Cl₂AlCH₂CHMeCH₂NMe₂ ( 6 ), Cl₂Al(CH₂)₃NMe₂ ( 8 ), and Cl₂Ga(CH₂)₃NMe₂ ( 9 ). The reaction of 6 and of 8 or 9 with BrMg(CH₂)₅MgBr and BrMg(CH₂)₆MgBr, respectively, yields (CH₂)₅AlCH₂CHMeCH₂NMe₂ ( 7 ), (CH₂)₆Al(CH₂)₃NMe₂ ( 10 ), and (CH₂)₆Ga(CH₂)₃NMe₂ ( 11 ). MeAlCl₂, made by the redistribution reaction of AlCl₃ with Me₂AlCl, reacts with 2 equivalents of Li(CH₂)₃NMe₂ yielding MeAl[(CH₂)₃NMe₂]₂ ( 12 ) and with MeN[(CH₂)₃MgCl]₂ under formation of MeAl[(CH₂)₃]₂NMe ( 13 ). MeAlCl₂, MeGaCl₂, or GaCl₃ accordingly react with one equivalent of organolithium reagent to give the intramolecularly nitrogen stabilized organoaluminum and organogallium chlorides MeClAl(CH₂)₃NMe₂ ( 14 ), MeClGa(CH₂)₃NMe₂ ( 15 ), MeClGaC₆H₄‐2‐CH₂NMe₂ ( 16 ) as well as Cl₂GaC₆H₄‐2‐CHMeNMe₂ ( 17 ). The compounds were characterized by elemental analyses, mass spectroscopy, ¹H, ¹¹B, ¹³C and ²⁷Al NMR investigations. Single crystal X‐ray structure analyses of 1 , 2 , 4 , 5 and 17 reveal the monomeric molecular structures with intramolecular nitrogen coordination.     

Mixed ligand complexes of platinum(0) containing diphosphines

The reaction of PtCl₂L (L = diphosphine) with the appropriate diphosphine L′ in ethanol followed by reduction with aqueous sodium borohydride leads to either disproportionation to give mixtures of the bis(diphosphine) complexes PtL₂ and PtL′₂ or to the formation of the mixed ligand complex PtLL′ depending on the diphosphines. Mixed ligand complexes are obtained when L=Ph₂P(CH₂)₂PPh₂, L′ = Ph₂P(CH₂PPh₂cis-Ph₂PCH CHPPh₂, Ph₂P(CH₂)₂AsPh₂, Ph₂- P(CH₂)₄PPh₂, o-Ph₂PC₆H₄PPh₂; and L=(C₆H₁₁)₂P(CH₂₂P(C₆H₁₁)₂, L′= Ph₂P(CH₂)PPh₂, Ph₂P(CH₂)₂PPh₂cis-Ph₂PCHCHPPh₂, (2S,3S)-Ph₂PCH- (CH₃)CH(CH₃)PPh₂, (R)-Ph₂PCH(CH₃)CH₂PPh₂. When L=Ph₂P(CH₂)₄PPh₂ L′= Ph₂P(CH₂₃PPh₂ or cis-Ph₂PCHCHRPh₂ the mixed ligand complexes are obtained but extensive disproportionation also occurs.     

1‐Azonia‐2‐boratanaphthalenes

The 1‐azonia‐2‐boratanaphthalenes (NH)(BX)C₈H₆ can be synthesized from 2‐aminostyrene and the dihaloboranes XBHal₂ ( 1 ‐ 4 : X = Cl, Br, iPr, tBu). Further derivatives (NH)(BX)C₈H₆ are obtained from 1 by replacing Cl by alkoxy or alkyl groups [ 5 ‐ 8 : X = OMe, OtBu, Me, (CH₂)₃NMe₂]. The hydrolysis of 1 gives a mixture of the bis(azoniaboratanaphthyl) oxide [(NH)BC₈H₆]₂O ( 9 ) and the hydroxy derivative (NH)[B(OH)]C₈H₆ ( 10 ). The diboryl oxide 9 crystallizes in the space group C2/c. The lithiation of 4 at the nitrogen atom gives [NLi(tmen)](BtBu)C₈H₆ ( 11 ), which upon reaction with the diborane(4) B₂Cl₂(NMe₂)₂ yields the 1, 2‐bis(azoniaboratanaphthyl)diborane B₂[N(BtBu)C₈H₆]₂(NMe₂)₂ ( 12 ). The 2‐chloro‐1‐methyl‐4‐phenyl derivative (NMe)(BCl)C₈H₅Ph ( 13 ) of the parent (NH)(BH)C₈H₆ can be synthesized from the aminoborane BCl₂(NMePh) and phenylethyne. Substitution of Cl in 13 gives the derivatives (NMe)(BX)C₈H₅Ph [ 14 ‐ 20 : X = N(SiMe₃)₂, Me, Et, iBu, tBu, CH₂SiMe₃, Ph] and the reaction of 13 with Li₂O affords the bis(azoniaboratanaphthyl) oxide [(NMe)BC₈H₅Ph]₂O ( 21 ). The reaction of 16 or 19 with [(MeCN)₃Cr(CO)₃] yields the complexes [{(NMe)(BX)C₈H₅Ph}Cr(CO)₃] ( 22 , 23 : X = Et, CH₂SiMe₃), in which the chromium atom is hexahapto bound to the homoarene part of 16 or 19 , respectively. The complex 23 crystallizes in the space group P2₁/c. Upon reaction of the phenols para‐C₆H₄R(OH) with the aryldichloroboranes ArBCl₂ and subsequent condensation of the products with phenylethyne, the 1‐oxonia‐2‐boratanaphthalenes O(BAr)C₈H₄RPh with R in position 6 and Ph in position 4 are formed ( 24 ‐ 26 : Ar = Ph, R = H, Me, OMe; 27 ‐ 29 : Ar = C₆F₅, R = H, Me, OMe). The azoniaboratanaphthalenes 1 ‐ 23 were characterized by NMR methods.     

Preparation and characterization of a novel asymmetrically oxidized complex of 2-(diphenylphosphino)-benzenethiol with ruthenium. The crystal and molecular structure of [Ru(2-Ph2PC6H4S)·(2-Ph2PC6H4S−OH)(2-Ph2PC6H4SO2)]·1/2H2O

The reaction between [RuCl₂(PPh₃)₃] and 2-(diphenylphosphino)-benzenethiolate anion (DPPBT) yields the 18-electron Ru^II complex [Ru(DPPBT)₃][HNEt₃] (1), which is readily oxidised first to the neutral Ru^III complex [Ru(DPPBT)₃] (2), and then to the 18 electron Ru^III complex [Ru(2-Ph₂PC₆H₄S)(2-Ph₂PC₆H₄S−OH)·(2-Ph₂PC₆H₄SO₂)]·1/2H₂O (3). The x-ray crystal structure of complex (3) reveals it has a pseudo-octahedral geometry. One sulphur has been oxidised to a sulphinic acid (S−OH) group and a second to a sulphinate (SO₂) group, both being ligatedvia sulphur.     

New Palladium(II) Complexes with a Tridentate PNO Ligand

The synthesis of neutral and cationic palladium complexes containing the tridentate monoanionic ligand [2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O]^? is described. Deprotonation of the Schiff base formed by condensation of 2-(diphenylphosphino)benzaldehyde with 2-aminophenol in the presence of the appropriate palladium precursor ([Pd(AcO)₂] or [PdCl₂(PhCN)₂]) form the corresponding neutral complexes [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(AcO)] (1) or [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(Cl)] (2) in good yield. The first reacts smoothly with thiols and activated phenols to give complexes of general formula [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(X)] (X = OC₆F₅ (3), SEt (4), S^tBu (5), SC₆H₅ (6), SC₆H₄-4Me (7), SC₆H₄-4NO₂ (8)). When the chloro complex is treated with silver perchlorate and tertiary phosphines (L) the cationic derivatives [Pd{2-(2-Ph₂PC₆H₄-CH=N)C₆H₄O}(L)][ClO₄] (L = PPh₃ (9), PMePh₂ (10), PMe₂Ph (11), PEt₃ (12)) were obtained. The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, ¹H, ¹⁹F and ³¹P NMR).     

Synthesis,Structure, and Fluxionality of Strained Hypercoordinate Silicon‐Bridged [1]Ferrocenophanes

The first hypercoordinate sila[1]ferrocenophanes [fcSiMe(2‐C₆H₄CH₂NMe₂)] ( 5 a ) and [fcSi(CH₂Cl)(2‐C₆H₄CH₂NMe₂)] ( 5 b ) (fc=(η⁵‐C₅H₄)Fe(η⁵‐C₅H₄)) were synthesized by low‐temperature (?78 °C) reactions of Li[2‐C₆H₄CH₂NMe₂] with the appropriate chlorinated sila[1]ferrocenophanes ([fcSiMeCl] ( 1 a ) and [fcSi(CH₂Cl)Cl] ( 1 d ), respectively). Single‐crystal Xray diffraction studies revealed pseudo‐trigonal bipyramidal structures for both 5 a and 5 b , with one of the shortest reported Si???N distances for an sp³‐hybridized nitrogen atom interacting with a tetraorganosilane detected for 5 a (2.776(2) Å). Elongated Si? C_ipso bonds trans to the donating NMe₂ arms (1.919(2) and 1.909(2) Å for 5 a and 5 b , respectively) were observed relative to both the non‐trans bonds ( 5 a : 1.891(2); 5 b : 1.879(2) Å) and the Si? C_ipso bonds of the non‐hypercoordinate analogues ([fcSiMePh] ( 1 b ): 1.879(4), 1.880(4) Å; [fcSi(CH₂Cl)Ph] ( 1 e ): 1.881(2), 1.884(2)). Solution‐state fluxionality of 5 a and 5 b , suggestive of reversible coordination of the NMe₂ group to silicon, was demonstrated by means of variable‐temperature NMR studies. The ΔG^≠ of the fluxional processes for 5 a and 5 b in CD₂Cl₂ were estimated to be 35.0 and 37.6 kJ mol^?1, respectively (35.8 and 38.3 kJ mol^?1 in [D₈]toluene). The quaternization of 5 a and 5 b by MeOTf, to give [fcSiMe(2‐C₆H₄CH₂NMe₃)][OTf] ( 7 a‐ OTf) and [fcSi(CH₂Cl)(2‐C₆H₄CH₂NMe₃)][OTf] ( 7 b‐ OTf), respectively, supported the reversibility of NMe₂ coordination at the silicon center as the source of fluxionality for 5 a and 5 b . Surprisingly, low room‐temperature stability was detected for 5 b due to its tendency to intramolecularly cyclize and form the spirocyclic [fcSi(cyclo‐CH₂NMe₂CH₂C₆H₄)]Cl ( 9 ‐Cl). This process was observed in both solution and the solid state, and isolation and Xray characterization of 9 ‐Cl was achieved. The model compound, [Fc₂Si(2‐C₆H₄CH₂NMe₂)₂] ( 8 ), synthesized through reaction of [Fc₂SiCl₂] with two equivalents of Li[2‐C₆H₄CH₂NMe₂] at ?78 °C, showed a lack of hypercoordination in both the solid state and in solution (down to ?80 °C). This suggests that either the reduced steric hindrance around Si or the unique electronics of the strained sila[1]ferrocenophanes is necessary for hypercoordination to occur.     

Syntheses and structures of novel paramagnetic organometallic complexes of manganese(II) and chromium(II)

The reactions of LiC₆H₄CH₂NMe₂ with MnI₂ and CrCl₂ in tetrahydrofuran gave the air-sensitive, paramagnetic complexes Li₂(THF)₂MX₂(C₆H₄CH₂NMe₂)₂. The solvated lithium halide may be removed from these complexes to give M(C₆H₄CH₂NMe₂)₂ as paramagnetic organometallic complexes. Similarly the reactions of LiCH₂C₆H₄NMe₂ with CrCl₂ and MnI₂ gave M(CH₂C₆H₄NMe₂)₂ whose magnetic moments and molecular weight measurements indicate that association occurs in solution. The X-ray crystal structure of Mn(CH₂C₆H₄NMe₂)₂ was determined. The molecule is dimeric, containing one bridging and one terminal CH₂C₆H₄NMe₂ ligand per metal. The bridging ligand is bonded to both manganese atoms through a common CH₂ group. One manganese atom has a bidentate CH₂C₆H₄NMe₂ ligand while the other manganese atom has a monodentate o-dimethylaminobenzyl ligand.     

Lewis acid promoted dehydration of amides to nitriles catalyzed by [PSiP]-pincer iron hydrides

The dehydration of primary amides to their corresponding nitriles using four [PSiP]-pincer hydrido iron complexes 1–4 [(2-Ph₂PC₆H₄)₂MeSiFe(H)(PMe₃)₂ ( 1 ), (2-Ph₂PC₆H₄)₂HSiFe(H)(PMe₃)₂ ( 2 ), (2-(iPr)₂PC₆H₄)₂HSiFe(H)(PMe₃)₂ ( 3 ) and (2-(iPr)₂PC₆H₄)₂MeSiFe(H)(PMe₃)₂ ( 4 )] as catalysts in the presence of (EtO)₃SiH as dehydrating reagent was explored in the good to excellent yields. It was proved for the first time that Lewis acid could significantly promote this catalytic system under milder reaction conditions than other Lewis acid-promoted system, such as shorter reaction time or lower reaction temperature. This is also the first example that dehydration of primary amides to nitriles was catalyzed by silyl hydrido iron complexes bearing [PSiP]-pincer ligands with Lewis acid as additive. This catalytic system has good tolerance for many substituents. Among the four iron hydrides 1 is the best catalyst. The effects of substituents of the [PSiP]-pincer ligands on the catalytic activity of the iron hydrides were discussed. A catalytic reaction mechanism was proposed. Complex 4 is a new iron complex and was fully characterized. The molecular structure of 4 was determined by single crystal X-ray diffraction.     

Helicate tris(aryl)carbinolates bearing pendant NR2 donors – a new family of supporting ligands for the synthesis of Sc3+ alkyl complexes

The reactions of aryllithium reagents o-LiC₆H₄CH₂NR₂ with (MeO)₂CO afford two new tris(aryl)carbinols bearing pendant-NR₂ donor groups in the side chain [o-R NCH C H ] COH [R = Me, R + R = (CH) ]. These alcohols feature helical chirality due to differently inclined aromatic fragments and are presented in a crystalline cell as two M and P enantiomers. Carbinol (R = Me) readily reacts with (Me3SiCH2)3Sc(THF)2 to give a scandium bis(alkyl) complex [(o-C₆H₄CH₂NMe₂)₃CO]Sc(CH₂SiMe₃)₂ featuring rigid binding of the alkoxy anion through a κ¹-O, κ²-N chelating coordination mode     

Synthesis and reactivity of new trimethylplatinum(IV) complexes containing chiral Schiff bases as ligands: Crystal structure of (OC-6-44-C)-[PtIMe3{κ-(R)-Ph2P(C6H4)CHNC*H(Ph)Me-P,N}]

Reaction of the tetranuclear complex [PtIMe₃]₄ with the ligand (S)- and (R)-Ph₂P(C₆H₄)CHNC*H(Ph)Me in a 1:4 molar ratio yields the mononuclear neutral complexes in diastereoisomeric mixtures [PtIMe₃{κ²-Ph₂P(C₆H₄)CHNC*H(Ph)Me-P,N}]. Iodide abstraction from mixture with AgBF₄ in the presence of pyridine (Py) induces a reductive elimination reaction with loss of ethane, leading to the cationic complex [PtMe(Py){κ²-Ph₂P(C₆H₄)CHNC*H(Ph)Me-P,N}][BF₄] [C* = (S)-, 3; (R)-, 4]. When this reaction was carried out in the presence of PPh₃ a consecutive orthometallation reaction with loss of methane is produced, forming the cationic complex [Pt(PPh₃){κ³-Ph₂P(C₆H₄)CHNC*H(C₆H₄)Me-C,P,N}][BF₄], [(S)-, 5; (R)-, 6]. All species were characterised in solution by ¹H and ³¹P{¹H} NMR spectroscopy, elemental analysis and mass spectrometry.The crystal structure of the diastereoisomer (OC-6-44-C)-[PtIMe₃{κ²-(R)-Ph₂P(C₆H₄)CHNC*H(Ph)Me-P,N}] has been determined by single-crystal X-ray diffraction.     

Synthese und Charakterisierung neuer intramolekular stickstoffstabilisierter Organoaluminium‐ und Organogalliumalkoxide

Synthesis and Characterization of New Intramolecularly Nitrogen‐stabilized Organoaluminium‐ and Organogallium Alkoxides The intramolecularly nitrogen stabilized organoaluminium alkoxides [Me₂Al{μ‐O(CH₂)₃NMe₂}]₂ ( 1a ), Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6 ( 2a ), [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]₂ ( 3a ) and [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]₂ ( 4 ) are formed by reacting equimolar amounts of AlMe₃ and Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, (S)‐i‐PrNHCH(i‐Pr)CH₂OH, or (S)‐PhCH₂NHCH(i‐Pr)CH₂OH, respectively. An excess of AlMe₃ reacts with Me₂N(CH₂)₂OH, Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, and (S)‐i‐PrNHCH(i‐Pr)CH₂OH producing the “pick‐a‐back” complexes [Me₂AlO(CH₂)₂NMe₂](AlMe₃) ( 5 ), [Me₂AlO(CH₂)₃NMe₂](AlMe₃) ( 1b ), [Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6](AlMe₃)₂ ( 2b ), and [(S)‐Me₂AlOCH₂CH(i‐Pr)NH‐i‐Pr](AlMe₃) ( 3b ), respectively. The mixed alkyl‐ or alkenylchloroaluminium alkoxides [Me(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 6 ) and [{CH₂=C(CH₃)}(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 8 ) are to obtain from Me₂AlCl and Me₂N(CH₂)₂OH and from [Cl₂Al{μ‐O(CH₂)₂NMe₂}]₂ ( 7 ) and CH₂=C(CH₃)MgBr, respectively. The analogous dimethylgallium alkoxides [Me₂Ga{μ‐O(CH₂)₃NMe₂}]₂ ( 9 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]_n ( 10 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]_n ( 11 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)N(Me)CH₂Ph}]_n ( 12 ) and [(S)‐Me₂Ga{μ‐OCH₂(C₄H₇NHCH₂Ph)}]_n ( 13 ) result from the equimolar reactions of GaMe₃ with the corresponding alcohols. The new compounds were characterized by elemental analyses, ¹H‐, ¹³C‐ and ²⁷Al‐NMR spectroscopy, and mass spectrometry. Additionally, the structures of 1a , 1b , 2a , 2b , 3a , 5 , 6 and 8 were determined by single crystal X‐ray diffraction.     

Synthesis,Characterization, and Syndio‐Specific Styrene Polymerization of Pyrrolyl‐Substituted Cyclopentadienyl Scandium Complexes

Acid‐base reaction of Sc(CH₂C₆H₄NMe₂‐o)₃ with 1 equiv. of pyrrolyl‐substituted cyclopentadienyl ligand C₄H₂Me₂NSiMe₂C₅Me₄H in toluene gave the half‐sandwich scandium bis(aminobenzyl) complex (C₄H₂Me₂NSiMe₂C₅Me₄)Sc(CH₂C₆H₄NMe₂‐o)₂ ( 2 ). Amine elimination between Sc[N(SiHMe₂)₂]₃(THF) and one equivalent of C₄H₂Me₂NSiMe₂C₅Me₄H afforded the scandium bis(silylamide) complex (C₄Me₂H₂NSiMe₂C₅Me₄)Sc[(NSiHMe₂)₂SiMe₂](THF) ( 3 ). Both scandium complexes 2 and 3 were characterized by elemental analysis, NMR spectroscopy, and single‐crystal X‐ray diffraction. 2 and 3 could serve as highly active precursors for styrene polymerization to give syndio‐tactic polystyrene (rrrrrr > 99 %).     

1,5-Diphosphabicyclo[3.3.1]nonan

1,5-Diphosphabicyclo [3.3.1]nonane 1,5-Diphosphabicyclo[3.3.1]nonane 8 has been obtained by free-radical cyclization of CH₂?CHCH₂(H)PCH₂P(H)CH₂CH?CH₂ 6 and 1-allyl-1,3-diphosphorinane 7 . For the synthesis of 6 and 7 the chlorophosphine Cl₂PCH₂PCl₂ 1 is used as a starting material, which can be converted into Me₂N(Cl)PCH₂P(Cl)NMe₂ 3 by reaction with (Me₂N)₂PCH₂P(NMe₂)₂ 2 . Treatment of 3 with two equivalents of allyl lithium and cleavage of the PN bonds in CH₂?CHCH₂(Me₂N)PCH₂P(NMe₂)CH₂CH?CH₂ 4 with diluted HCl affords CH₂?CHCH₂(H)(O)PCH₂P(O)(H)CH₂CH?CH₂ 5 . Phenylsilane is used for the first time as a reducing agent to obtain a secundary phosphine like 6 from the secundary phosphine oxide ( 5 ). Prolonged heating increases the yield of the byproduct 7 in the mixture of 6 and 7 . Reactions of the trivalent phosphorus in 8 with CS₂, CH₃I, POCl₃, NO, sulfur, and KSeCN, respectively, delivers the corresponding derivatives 9–17 . The compounds decribed are characterized by ¹H, ¹³C, ³¹P, ⁷⁷Se n.m.r., i.r., and m.s. data.     

Palladium(II) iminophosphine complexes

New complexes of general formula [PdCl₂(NP)] (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr, ^t Bu, NH-Me) and [Pd(NP)₂](ClO₄)₂ (NP = o-Ph₂PC₆H₄-CH=N-R; R = Me, ⁱ Pr) have been prepared by directly reacting the precursor PdCl₂(PhCN)₂ with iminophosphines (NP) in 1:1 and 1:2 molar ratios respectively. When the chloro-complex [PdCl₂(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)] was treated with CF₃SO₃Ag in MeCN, the labile complex [Pd(o-Ph₂PC₆H₄-CH=N ⁱ -Pr)(MeCN)₂](CF₃SO₃)₂ was obtained in good yield. The reactivity of the new precursor towards a variety of neutral N- and P-donor ligands (py, PMe₂Ph, PMePh₂, PEt₃, bipy, dppe, 2-thpy) has been studied. The new complexes were characterized by partial elemental analyses and by spectroscopy (i.r., ¹H- and ³¹P-n.m.r.). The molecular structure of the aquo-complex [Pd(NP)(2-thpy)(H₂O)](CF₃SO₃)₂ has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as a chelating ligand with coordination around the palladium atom slightly distorted from square-planar geometry.