Neutral and Cationic Organoaluminum Complexes Utilizing a Novel Anilido−Phosphinimine Ancillary Ligand

Contrasting a series of bidentate amido phosphine oxide, sulfide, or selenide ligands and complexes of dimethyl aluminum and indium

A series of EP(V)-imine phosphine-imine ligands (Dipp-NC(CH3)-(CH2)-PE(Ph2)) (Dipp = 2,6-diisopropylphenyl, E = O, S, Se) and corresponding dimethyl aluminum and indium complexes were prepared and characterized using multi-nuclear NMR spectroscopy and SC-XRD. Solution-state 1H and 31P NMR spectroscopy indicate a mixture of isomers in solution (C6D6, CDCl3, and CD3CN). Solid state structures of both the imine and (E)-enamine isomers of the oxygen-based ligand have been observed. These three ligands (L) were then deprotonated with M(CH3)3 (M = Al or In), with methane loss forming a 6-membered ring via bidentate chelation ((κ2-L)M(CH3)2). The indium/oxide complex also crystallized as a 12-membered ring.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Synthesis, characterization, and reactivity of group 13 hydride complexes based on amido-amine ligands

The preparation of group 13 hydride complexes supported by N,N',N'-substituted 1,2-ethanediamines is reported. Dihydridoalanes LAlH2, for which the aggregation behaviour in solution and in the solid state is modulated by the steric bulk of the aryl substituent, readily react with elemental sulphur affording dinuclear aluminium sulphide complexes. Chloridohydrido trielanes LEHCl (E = B, Al, Ga) have been synthesized as well starting from the hydrochloride salts of the protio-ligands and the chlorido substituent within LAlHCl is readily replaced using Li[N(SiMe3)2]. Depending on the steric bulk of the ligand, the chloridohydrido gallane gives rise to a dinuclear gallium(ii) complex upon heating. All twelve complexes reported in here have been fully characterized and the solid-state structure of eleven complexes has been examined by means of single-crystal X-ray diffraction analysis.

Synthesis, structural characterization, and bonding analysis of two-coordinate copper(I) and silver(I) complexes of pyrrole-based bis(phosphinimine): new metal-pyrrole ring π-interactions

The reaction between 2,5-bis(diphenylphosphinomethyl)pyrrole and Me3SiN3 gave the new pyrrole-based bis(phosphinimine) L1H in an excellent yield. L1H reacts with [CuCl(COD)]2, AgBF4, or AgOTf to give the corresponding two-coordinate mononuclear ionic complex formulated as [M{(L1H)-κ2N,N}]+[X]- where M = Cu and Ag; X = [CuCl2], BF4 or OTf. Their single crystal X-ray diffraction studies confirmed the two-coordinate geometry formed by the chelate bonding mode of L1H. These 10-membered metalacycles exhibit planar chirality and were also characterized by spectroscopic methods. In addition, in all three structures, there exists a hitherto unknown π-interaction between the pyrrole ring atoms and metal, represented as η2-(Cα-N) in the copper(i) complex, and η3-(Cα-N-Cα') in the silver(i) complexes. These weak interactions were supported by DFT calculations in terms of their electron densities, non-covalent interaction plots and the decrease in the aromaticity of the pyrrole ring.

Phosphasalalen Rare-Earth Complexes for the Polymerization of rac-Lactide and rac-β-Butyrolactone

A series of new phosphasalalen pro-ligands, analogues of salalen but with an iminophosphorane replacing the imine functionality, and their corresponding rare-earth alkoxide and siloxide complexes were synthesized. The multinuclear NMR spectra and X-ray diffraction analyses revealed that, for the tert-butoxide and ethoxide complexes, the resulting phosphasalalen rare-earth product was composed of a mononuclear alkoxide and a binuclear complex containing bridged alkoxo and hydroxo groups, while an analogous binuclear complex was isolated as the sole product for the siloxide complex. All the complexes could catalyze the heteroselective ring-opening polymerization (ROP) of rac-lactide (P_r up to 0.77) with high catalytic activities and a controlled polydispersity. Remarkably, the yttrium and lutetium phosphasalalen complexes could also efficiently catalyze the ROP of rac-β-butyrolactone to produce syndiotactic polymers (P_r up to 0.73) while their salalen analogues were inert, revealing the special effects of the iminophosphorane moiety. Detailed end-group analyses and kinetic investigations suggested that the alkoxo-hydroxo-bridged complexes maintained their binuclear structures in the polymerization.

Synthesis and characterization of group 13 dichloride (M = Ga, In), dimethyl (M = Al) and cationic methyl aluminum complexes supported by monoanionic NNN-pincer ligands

A series of monoanionic NNN-pincer ligands effectively stabilize five-coordinate gallium and indium dichloride complexes, as well as neutral dimethyl aluminum species, and organometallic cations thereof.

Reactivity of N-Phosphinoguanidines of the Formula (HNR)(Ph2PNR)C(NAr) toward Main Group Metal Alkyls: Facile Ligand Rearrangement from N-Phosphinoguanidinates to Phosphinimine-Amidinates

We report the reactivity of N-phosphinoguanidines of the formula (HNR)(Ph₂PNR)C(NAr) (R = ⁱPr and Ar = 2,6-ⁱPr₂C₆H₃ [Dipp] for 1a, R = ⁱPr and Ar = 2,4,6-Me₃C₆H₂ [Mes] for 1b, and R = Cy and Ar = Dipp for 1c), prepared in high yields from the corresponding trisubstituted guanidines, toward main group metal alkyls AlMe₃, ZnEt₂, MgⁿBu₂, and ⁿBuLi to obtain novel phosphinoguanidinato and phosphinimine-amidinato compounds. Reactions of 1a-c with AlMe₃ at room temperature led to the kinetic phosphinoguanidinato products [Al{κ²-N,N'-(NR)C(NAr)(NRPPh₂)}Me₂] (2a-c), whereas the mild heating (60-80 °C) of solutions of 2a-c give the thermodynamic phosphinimine-amidinato products [Al{κ²-N,N'-(NR)C(NAr)(PPh₂NR)}Me₂] (3a-c) after ligand rearrangement. The reactions of equimolar amounts of 1a-c and ZnEt₂ initially give solutions containing unstable phosphinoguanidinato compounds [Zn{κ²-N,P-(NR)C(NAr)(NRPPh₂)}Et] (4a-c), which rearrange upon mild heating to the phosphinimine-amidinato derivatives [Zn{κ²-N,N'-(NR)C(NAr)(PPh₂NR)}Et] (6a-c). Bis(phosphinoguanidinato) compounds [Zn{κ²-N,P-(NR)C(NAr)(NRPPh₂)}₂] (5a-c) can be obtained under mild conditions (<45 °C) in THF, whereas bis(phosphinimine-amidinato) compounds [Zn{κ²-N,N'-(NR)C(NAr)(PPh₂NR)}₂] (7a-c) are also accessible under more forcing conditions (55-100 °C) from (i) ZnEt₂ and 1b,c (2 equiv), (ii) 6a and 1a, or (iii) 5b,c. Equimolar mixtures of MgⁿBu₂ and 1a-c in THF at room temperature give unstable phosphinimine-amidinato monoalkyl products [Mg{κ²-N,N'-(NR)C(NAr)(PPh₂NR)}ⁿBu(THF)₂] (8a-c), whereas 2 equiv of 1a,b are required to reach the bischelate compounds [Mg{κ²-N,N'-(NⁱPr)C(NAr)(PPh₂NⁱPr)}₂] (9a,b). Finally, phosphinoguanidinato compounds [Li{κ²-N,P-(NR)C(NDipp)(NRPPh₂)}(THF)₂] (10a,c) were obtained in the reactions of 1a,c with ⁿBuLi in THF under ambient conditions. The removal of the solvent from solutions of 10a,c under partial vacuum leads to the dinuclear compounds [Li₂{μ-κ²-N,N':κ¹-N-(NR)C(NDipp)(NRPPh₂)}₂(THF)₂] (11a,c) after the decoordination of one of the THF molecules in 10a,c and dimerization. Heating solutions of 10a,c at 60 °C triggers ligand rearrangement to give phosphinimine-amidinato compounds [Li{κ²-N,N'-(NR)C(NDipp)(PPh₂NR)}(THF)₂] (12a,c). We also propose a mechanism for the ligand rearrangement reaction from 10a to give 12a, supported by DFT calculations, which fits nicely with our experimental results. It essentially involves a carbodiimide deinsertion reaction followed by a [3 + 2] cycloaddition between the resulting lithium phosphino-amide and the carbodiimide.

Consecutive N2 loss from a uranium diphosphazide complex

A new 'diphosphazidosalen' ligand was synthesized and successfully transferred to uranium using salt metathesis strategies. The resultant 8-coordinate uranium(iv) diphosphazide complex [κ6-1,2-{(N3)PPh2(2-O-C6H4)}2C6H4]UCl2 (1) is unstable to consecutive N2 loss, affording the asymmetric species [κ5-1-{(N3)PPh2(2-O-C6H4)}-2-{N=PPh2(2-O-C6H4)}C6H4)]UCl2 (2), defined by a phosphazide-phosphinimine mixed-ligand framework, and ultimately, the uranium(iv) phosphasalen complex [κ4-1,2-{N=PPh2(2-O-C6H4)}2C6H4]UCl2(THF) (3).

Reaction of an N/Al FLP-based aluminum hydride toward alkynes: deprotonated alumination versus hydroalumination with regioselective cis-addition character

Reactions of an N/Al FLP-based aluminum dihydride (o-TMP-C6H4)AlH2 (1, TMP = N(CMe2CH2)2CH2) with several terminal and internal alkynes were studied. 1 reacted with HC[triple bond, length as m-dash]CR by deprotonated alumination to yield (o-TMP-C6H4)Al(C[triple bond, length as m-dash]CR)2 (R = Ph (2), 1-C4H3S (3)) and with HC[triple bond, length as m-dash]CPPh2 by deprotonated alumination followed by HC[triple bond, length as m-dash]CPPh2 C(sp)-H-activation addition to yield [o-(TMP)H-C6H4]Al(C[triple bond, length as m-dash]CPPh2)3 (4). Furthermore, 1 reacted with R1C[triple bond, length as m-dash]CR2 to produce mono-hydroalumination compounds (o-TMP-C6H4)AlH(CR1[double bond, length as m-dash]CHR2) (R1,R2 = Ph,Ph (5), Ph,Et (6) and SiHMeR',Ph (7, R' = N(SiMe2Ph)-2,6-iPr2C6H3), all as monomers, as well as {(o-TMP-C6H4)AlH[C(PPh2)[double bond, length as m-dash]CHPh]}2 (8), a dimer formed due to the intermolecular P/Al donor-acceptor interaction. Moreover, bis-hydroalumination compounds (o-TMP-C6H4)Al(CR1[double bond, length as m-dash]CHR2)2 (R1,R2 = SiHMe2,PPh2 (9) and SiHPh2,PPh2 (10)) were produced. Natural Bond Orbital (NBO) analysis was performed, which revealed the inequivalent charge distribution on the C[triple bond, length as m-dash]C carbon atoms of the alkynes that have two different substituents. The electronic matching interaction between the Al-H and C[triple bond, length as m-dash]C bonds is discussed. The hydroalumination reaction exhibits the regioselective cis-addition character.

Highly luminescent copper(i) halide complexes chelated with a tetradentate ligand (PNNP): synthesis, structure, photophysical properties and theoretical studies

Strongly emissive copper(i) halide complexes constructed from a new tetradentate chelating ligand and butterfly-shaped Cu₂X₂ cores are presented and systematically investigated.

Cleavage of an aryl carbon–nitrogen bond of a phosphazido iron(ii) complex promoted by hydride metathesis

The unexpected reaction of a Fe(ii) enamidophosphazide complex with KBEt₃H, which results in the elimination of N₂ and 1,3-Me₂C₆H₄ to generate a dinuclear Fe(ii) derivative with bridging phosphinimido units, is presented along with mechanistic studies.

A cascade reaction: ring-opening insertion of dioxaphospholane into lutetium alkyl bonds

Although an organolutetium complex of a new dioxaphospholane-substituted carbazole-based pincer ligand appears immune to cyclometalation, an unusual ring-opening insertion reaction was observed.

Palladium complexes derived from N,N-bidentate NH-iminophosphorane ligands: synthesis and use as catalysts in the Sonogashira reaction

The addition of primary amines to the C=C bond of diphenylalkenyl iminophosphoranes yielded a new subtype of N,N-bidentate ligands bearing N=P(V)-C-C-NH backbones. These donor ligands reacted with PdCl(2)(COD) to give the corresponding σN,σN-palladium complexes containing secondary amino groups, bearing an intrinsically chiral nitrogen atom, and iminophosphorane units. These new complexes have been fully characterized by the use of spectroscopic techniques and X-ray crystallography. The comparison of the data extracted from their solution NMR spectra with their solid state structures demonstrated the conformational stability of their six-membered chelate ring and also the configurational stability of the chiral nitrogen atom, thus ruling out an arm-off racemization process. The addition of the chiral, racemic α-methylbenzylamine to the prochiral P-alkenyl iminophosphoranes yielded mixtures of the two expected diasteroisomeric ligands in low diastereoisomeric ratios. One of these mixtures was resolved into their components, each one in turn giving rise to a pair of diasteromeric palladium complexes epimeric at the amino nitrogen atom. One selected example of the new complexes efficiently catalyzes the copper- and amine-free Sonogashira reaction of aryl halides with acetylenes.

Synthesis and Reactivity of Rare Earth Metal Alkyl Complexes Stabilized by Anilido Phosphinimine and Amino Phosphine Ligands

Anilido phosphinimino ancillary ligand H(2)L(1) reacted with one equivalent of rare earth metal trialkyl [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] (Ln=Y, Lu) to afford rare earth metal monoalkyl complexes [L(1)LnCH(2)Si(CH(3))(3)(THF)] (1 a: Ln=Y; 1 b: Ln=Lu). In this process, deprotonation of H(2)L(1) by one metal alkyl species was followed by intramolecular C--H activation of the phenyl group of the phosphine moiety to generate dianionic species L(1) with release of two equivalnts of tetramethylsilane. Ligand L(1) coordinates to Ln(3+) ions in a rare C,N,N tridentate mode. Complex l a reacted readily with two equivalents of 2,6-diisopropylaniline to give the corresponding bis-amido complex [(HL(1))LnY(NHC(6)H(3)iPr(2)-2,6)(2)] (2) selectively, that is, the C--H activation of the phenyl group is reversible. When 1 a was exposed to moisture, the hydrolyzed dimeric complex [{(HL(1))Y(OH)}(2)](OH)(2) (3) was isolated. Treatment of [Ln{CH(2)Si(CH(3))(3)}(3)(thf)(2)] with amino phosphine ligands HL(2-R) gave stable rare earth metal bis-alkyl complexes [(L(2-R))Ln{CH(2)Si(CH(3))(3)}(2)(thf)] (4 a: Ln=Y, R=Me; 4 b: Ln=Lu, R=Me; 4 c: Ln=Y, R=iPr; 4 d: Ln=Y, R=iPr) in high yields. No proton abstraction from the ligand was observed. Amination of 4 a and 4 c with 2,6-diisopropylaniline afforded the bis-amido counterparts [(L(2-R))Y(NHC(6)H(3)iPr(2)-2,6)(2)(thf)] (5 a: R=Me; 5 b: R=iPr). Complexes 1 a,b and 4 a-d initiated the ring-opening polymerization of d,l-lactide with high activity to give atactic polylactides.

New coordination modes at molybdenum for 2-diphenylphosphinoaniline derived ligands

The complexes [MoCl3(1-N,2-Ph2P-C6H4)2] (1) and {MoCl(Nt-Bu)[1-micro(N),2-(Ph2P)C6H4]}2 (2) have been obtained from the reaction of 2-diphenylphosphinoaniline [1,2(NH2)(Ph2P)C6H4] with either sodium molybdate [Na2MoO4] (in the presence of Et3N and Me3SiCl) or [MoCl2(Nt-Bu)2(DME)]; the crystal structure of 1 reveals a novel MoNC2PN six-membered conjugated ring system derived from a P-N coupling reaction between two ligands, whilst that of 2 reveals bridging imido/terminal phosphine ligation.

Imino Sulfinamidines: Synthesis and Coordination Chemistry of a Novel Class of Chiral Bidentate Ligands

The new imino sulfinamidine ligand PhS(NHt-Bu)=NC(Me)=N(C6H3-2,6-iPr2), LH (11) was synthesized from N-(2,6-diisopropylphenyl)acetamidine (9) and N-tert-butyl phenylsulfinimidoyl chloride (10). Reaction of LH (11) with ZnEt2 or AlMe3 gave the complexes LZnEt (12) and LAlMe2 (13), respectively. The structures of 12 and 13 were determined by X-ray diffraction and were shown to contain L as a kappa2-N1,N5 bidentate ligand in a six-membered chelate. Formation of the magnesium complex (LMgN(TMS)2 x L2Mg) (14) from 11, MgI2, and KN(SiMe3)2 highlighted a secondary coordination mode of L, binding through the sulfinamidine nitrogens in a four-membered chelate.

Neutral and cationic aluminium complexes of a sterically demanding N-imidoylamidine ligand

The N-imidoylamidine ligand i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2 2 was prepared. Direct reactions with AlI3 or AlMe3 afforded [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlI2][AlI4] 3 and [i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlMe2][AlMe4].AlMe3, 4 respectively. Thermolysis of 4 gave (i-Pr2C6H3NC(=CH2)(NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe2 6. Subsequent reaction with B(C6F5)3 gave the zwitterionic species [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe(mu-MeB(C6F5)3)] 7. In a related reactions of 2, [Ph3C][B(C6F5)4] and AlMe3, AlH3.NEtMe2 or AlD3.NMe3, the complexes [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlR2][B(C6F5)4] (R = Me 5, H 8, D 9) and [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlH][B(C6F5)4] 10 are formed. Single-crystal X-ray data for 2, 3, 5 and 10 are reported.

Transition metal complexes of a sterically demanding diimine ligand

The reaction of the metal halide with the sterically demanding ligand (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2 afforded the complexes (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2MX2 (X = Cl, M = Fe (2), Co (3); X = Br, M = Ni (4), M = Cu (5), Zn (6)). The species of 2 reacts with Li(OEt2)B(C6F5)4 to form the yellow adduct [(i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Fe(µ-Cl)2Li(OEt2)2][B(C6F5)4] (7) while alkylation of 2 gave (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2FeClCH2SiMe3 (8). The species [(i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2Ni(η3-C3H5)][B(3,5-CF3C6H3)4] (9) was obtained from reaction of 1 with [(η3-C3H5)NiBr]2 and [Na][B(3,5-(CF3)2C6H3)4] while reaction of 4 with Super-Hydride afforded (i-Pr2C6H3N)(C(Me)(NC6H3-i-Pr2))2NiH2BEt2 (10). X-ray data are reported for 2–10. The sterically demanding nature of the ligand inhibits subsequent reactivity of these species. Key words: sterically demanding ligands, chelate complexes, X-ray structure, diimine ligands.

Organoaluminium complexes incorporating an amido phosphine chelate with a pendant amine arm

The palladium-catalyzed aryl amination of 1-bromo-2-fluorobenzene with N,N-dimethylethylenediamine quantitatively produces N-(dimethylaminoethyl)-2-fluoroaniline, which subsequently reacts with KPPh2 in 1,4-dioxane to afford N-(dimethylaminoethyl)-2-diphenylphosphinoaniline (H[PNN]). The reactions of trialkylaluminium with H[PNN] in toluene generate the corresponding aluminium dialkyl complexes [PNN]AlR2 (R = Me, Et, i-Bu). The solution NMR spectroscopic and X-ray crystallographic studies are indicative of a trigonal bipyramidal geometry for these aluminium complexes in which the amino nitrogen atom is trans to the phosphorus donor of the [PNN]- ligand. This study presents rare examples of structurally characterized, five-coordinate aluminium hydrocarbyl complexes supported by phosphine-derived ligands.