Anilido Ligand Research Articles

Reductive Elimination from Phosphine-Ligated Alkylpalladium(II) Amido Complexes To Form sp3 Carbon-Nitrogen Bonds.

We report the formation of phosphine-ligated alkylpalladium(II) amido complexes that undergo reductive elimination to form alkyl-nitrogen bonds and a combined experimental and computational investigation of the factors controlling the rates of these reactions. The free-energy barriers to reductive elimination from t-Bu3P-ligated complexes were significantly lower (ca. 3 kcal/mol) than those previously reported from NHC-ligated complexes. The rates of reactions from complexes containing a series of electronically and sterically varied anilido ligands showed that the reductive elimination is slower from complexes of less electron-rich or more sterically hindered anilido ligands than from those containing more electron-rich and less hindered anilido ligands. Reductive elimination of alkylamines also occurred from complexes bearing bidentate P,O ligands. The rates of reactions of these four-coordinate complexes were slower than those for reactions of the three-coordinate, t-Bu3P-ligated complexes. The calculated pathway for reductive elimination from rigid, 2-methoxyarylphosphine-ligated complexes does not involve initial dissociation of the oxygen. Instead, reductive elimination is calculated to occur directly from the four-coordinate complex in concert with a lengthening of the Pd-O bond. To investigate this effect experimentally, a four-coordinate Pd(II) anilido complex containing a flexible, aliphatic linker between the P and O atoms was synthesized. Reductive elimination from this complex was faster than that from the analogous complex containing the more rigid, aryl linker. The flexible linker enables full dissociation of the ether ligand during reductive elimination, leading to the faster reaction of this complex.

Cover Feature: A Structurally Characterized CuIII Complex Supported by a Bis(anilido) Ligand and Its Oxidative Catalytic Activity (Chem. Eur. J. 56/2017)

Cover Feature: A Structurally Characterized Cu^III Complex Supported by a Bis(anilido) Ligand and Its Oxidative Catalytic Activity (Chem. Eur. J. 56/2017)

Studies on Three-Coordinate [Co{N(SiMe3)2}2L] Complexes, L = N-Heterocyclic Carbene

A series of three-coordinate N-heterocyclic carbene bis(trimethylsilyl)amide complexes of cobalt, [Co{N(SiMe3)2}2(NHC)] (NHC = N,N′-diarylimidazolin-2-ylidene, aryl = 2,6-diisopropylphenyl, SIPr (1), aryl = mesityl, SIMes (2); κ1-N,N′-diphosphanylimidazol-2-ylidene, PCP (5); κ1-N-phosphanyl-N′-2,6-diisopropylphenylimidazol-2-ylidene, PC (6); cyclic alkyl amino carbene :C(Cy)CH2CMe2N-2,6-Pri2C6H3, cAACCy (7)) were prepared by the reaction of [Co{N(SiMe3)2}2] with the corresponding NHCs. The complexes exhibited interesting transamination reactivity in reactions with bulky 2,6-diisopropylaniline (NH2(DiPP)), where adjustment of the stoichiometry and reaction conditions resulted in the substitution of one or two N(SiMe3)2 ligands by the anilido ligand NH(DiPP), giving [Co{N(SiMe3)2}{NH(DiPP)}(NHC)] (NHC = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, IPr (8)) and [Co{NH(DiPP)}2(NHC)] (NHC = SIPr (9); IPr (10); PCP (11)). X-ray crystallography revealed trigonal-planar coordination geometry at Co for all o...

Well‐controlled ring‐opening polymerization of cyclic esters catalyzed by aluminum amido complexes: Kinetics and mechanism

ABSTRACTA series of aluminum dimethyl complexes 1–6 bearing N‐[2‐(pyrrolidinyl)benzyl]anilido ligands were synthesized and well characterized. The molecular structure of complex 1 determined by an X‐ray diffraction study indicates the bidentate chelating mode of the pyrrolidinyl‐anilido ligand. In the absence of a coinitiator, these complexes exhibited excellent control toward the polymerizations of ε‐caprolactone and rac‐lactide, affording polyesters with quite narrow molecular weight distributions (Mw/Mn = 1.04–1.26). The end group analysis of ε−CL oligomer via 1H NMR and ESI‐TOF MS methods gave strong support to the hypothesis that the polymerization catalyzed by these aluminum complexes proceeds via a coordination‐insertion mechanism involving a unique AlN (amido) bond initiation. Via 1H NMR scale oligomerization studies, it is suggested that the insertion of the first lactide monomer into AlN bond of the complex is much easier than the insertion of lactide monomer into the newly formed AlO (lactate) bond and might also be easier than the insertion of the first ε−CL monomer into AlN bond. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3096–3106

Zirconium and Titanium Propylene Polymerization Precatalysts Supported by a Fluxional C2-Symmetric Bis(anilide)pyridine Ligand

Titanium and zirconium complexes supported by a bis(anilide)pyridine ligand (NNN = pyridine-2,6-bis(N-mesitylanilide)) have been synthesized and crystallographically characterized. C2-symmetric bis(dimethylamide) complexes were generated from aminolysis of M(NMe2)4 with the neutral, diprotonated NNN ligand or by salt metathesis of the dipotassium salt of NNN with M(NMe2)2Cl2. In contrast to the case for previously reported pyridine bis(phenoxide) complexes, the ligand geometry of these complexes appears to be dictated by chelate ring strain rather than metal–ligand π bonding. The crystal structures of the five-coordinate dihalide complexes (NNN)MCl2 (M = Ti, Zr) display a C1-symmetric geometry with a stabilizing ipso interaction between the metal and the anilido ligand. Coordination of THF to (NNN)ZrCl2 generates a six-coordinate C2-symmetric complex. Facile antipode interconversion of the C2 complexes, possibly via flat C2v intermediates, has been investigated by variable-temperature 1H NMR spectroscopy for (NNN)MX2(THF)n (M = Ti, Zr; X = NMe2, Cl) and (NNN)Zr(CH2Ph)2. These complexes were tested as propylene polymerization precatalysts, with most complexes giving low to moderate activities (102–104 g/(mol h)) for the formation of stereoirregular polypropylene.

Bis(μ2-η2:η2-2,4,6-trimethylbenzonitrile)bis[(N-isopropyl-3,5-dimethylanilido)molybdenum(III)](Mo—Mo)

The title compound, [Mo2(C11H16N)4(C10H11N)2], is a dinuclear molybdenum complex with a formal metal–metal bond [Mo⋯Mo separation = 2.5946 (8) Å], four anilide-type ligands and two bridging mesityl nitrile groups. There are two inversion symmetric mol­ecules in the unit cell (an inversion center is localized at the mid-point of the Mo—Mo bond), each with approximate non-crystallographic C 2h symmetry. The mol­ecules contain disordered isopropyl and 3,5-C6H3Me2 groups on different anilido ligands; the major component having an occupancy of 0.683 (7). The complex was obtained in low yield as the product from the reaction between the bridging pyrazine adduct of molybdenum tris­-anilide ([μ2-(C4H4N2){Mo(C11H16N)3}2]) and mesityl nitrile with a loss of one anilido ligand.

Dichloridobis{N-[(dimethylamino)dimethylsilyl]-2,6-dimethylanilido-κ2N,N′}zirconium(IV)

The monomeric title zirconium(IV) compound, [Zr(C12H21N2Si)2Cl2], was prepared by the metathetical reaction of [LiN(SiMe2NMe2)(2,6-Me2C6H3)]2 with zirconium tetra­chloride. The ZrIV atom is N,N′-chelated by the N-silylated anilido ligand. Along with two Cl atoms, the six-coordinated ZrIV atom demonstrates a highly distorted octa­hedral geometry. The two ligands around the ZrIV atom are arranged cis to each other and obey the C 2 symmetry operation. That means the asymmetric unit consists of only half of the mol­ecular compound and the complete mol­ecule is generated by a twofold axis. The two ends of the N—Si—N chelating unit exhibit different affinities for the metal center. The Zr—Namino bond is longer than the Zr—Nanilido bond.

Synthesis of rhodium–carbonyl complexes bearing a novel P,N-chelating ligand of Schiff-base type

Schiff-base type N,P-chelating ligands, phosphorus analogues of imino–anilido ligands, were designed and synthesized as a new type of ligands toward transition metals, and the rhodium–carbonyl complexes bearing the novel imino–phosphido and phosphaalkenyl-anilido ligands were synthesized as stable crystalline compounds. Their structures were definitively revealed by X-ray crystallographic analysis, showing the unique electronic features of the ligands. In addition, the effective trans-influence of the phosphorus atom was suggested on the basis of the structural parameters and spectroscopic features of the isolated complexes.

Dichloridobis{N-[(dimethylamino)dimethylsilyl]-2,6-dimethylanilido-κ2N,N′}hafnium(IV)

In the monomeric hafnium(IV) title compound, [Hf(C12H21N2Si)2Cl2], the Hf atom is N,N′-chelated by the N-silylated anilido ligand. The two ligands around the Hf atom are arranged cis to each other; a twofold rotation axis passes through the Hf atom. The two ends of the N—Si—N chelating unit exhibit different affinities to the metal center. The Zn—Namino bond is longer than the Zn—Nanilido bond. Along with two Cl atoms, the six–coordinate Hf atom demonstrates a highly distorted octa­hedral geometry.

Synthesis and Reactivity of a Ruthenium(III) Bis(anilide) Dimer by Oxidative Addition of an N,N‘-Disubstituted Hydrazine

The RuIII bis(anilide) dimer [Cp*RuCl(μ-NHPh)]2 (1a) is formed upon reaction of (Cp*RuCl)4 with 1,2-diphenylhydrazine in benzene. An X-ray crystal structure shows a centrosymmetric (Ci) dimer with a planar Ru2N2 core. Reaction of (Cp*RuCl)4 with a mixture of PhNHNHPh and TolNHNHTol gives only the homodimers 1a and [Cp*RuCl(μ-NHTol)]2 (Tol = p-tolyl). The lack of crossover indicates that cleavage of the hydrazine N−N bond is an intramolecular process. In polar solvents such as acetonitrile, the Ci dimer 1a isomerizes to the C2v isomer 1b, in which the anilido substituents are cis across the Ru2N2 core. Both isomers appear to be kinetic products of the synthesis, but 1b isomerizes to 1a in the benzene solvent. In the presence of 1a, 1,2-diphenylhydrazine disproportionates into azobenzene and aniline, and labeling studies show that this occurs without participation of the anilido ligands of 1a. Complex 1a shows slow exchange of the anilide ligands with toluidine (H2NTol) by NMR spectroscopy and is unreactive...

Chemistry Surrounding Monomeric Copper(I) Methyl, Phenyl, Anilido, Ethoxide, and Phenoxide Complexes Supported by N-Heterocyclic Carbene Ligands: Reactivity Consistent with Both Early and Late Transition Metal Systems

Monomeric copper(I) alkyl complexes that possess the N-heterocyclic carbene (NHC) ligands IPr, SIPr, and IMes [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] react with amines or alcohols to release alkane and form the corresponding monomeric copper(I) amido, alkoxide, or aryloxide complexes. Thermal decomposition reactions of (NHC)Cu(I) methyl complexes at temperatures between 100 and 130 degrees C produce methane, ethane, and ethylene. The reactions of (NHC)Cu(NHPh) complexes with bromoethane reveal increasing nucleophilic reactivity at the anilido ligand in the order (SIPr)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh) [dtbpe = 1,2-bis(di-tert-butylphosphino)ethane]. DFT calculations suggest that the HOMO for the series of Cu anilido complexes is localized primarily on the amido nitrogen with some ppi(anilido)-dpi(Cu) pi-character. [(IPr)Cu(mu-H)]2 and (IPr)Cu(Ph) react with aniline to quantitatively produce (IPr)Cu(NHPh)/dihydrogen and (IPr)Cu(NHPh)/benzene, respectively. Analysis of the DFT calculations reveals that the conversion of [(IPr)Cu(mu-H)]2 and aniline to (IPr)Cu(NHPh) and dihydrogen is favorable with DeltaH approximately -7 kcal/mol and DeltaG approximately -9 kcal/mol.

Hydrogen−Deuterium Exchange between TpRu(PMe3)(L)X (L = PMe3 and X = OH, OPh, Me, Ph, or NHPh; L = NCMe and X = Ph) and Deuterated Arene Solvents: Evidence for Metal-Mediated Processes

At elevated temperatures (90-130 degrees C), complexes of the type TpRu(PMe3)2X (X = OH, OPh, Me, Ph, or NHPh; Tp = hydridotris(pyrazolyl)borate) undergo regioselective hydrogen-deuterium (H/D) exchange with deuterated arenes. For X = OH or NHPh, H/D exchange occurs at hydroxide and anilido ligands, respectively. For X = OH, OPh, Me, Ph, or NHPh, isotopic exchange occurs at the Tp 4-positions with only minimal deuterium incorporation at the Tp 3- or 5-positions or PMe3 ligands. For TpRu(PMe3)(NCMe)Ph, the H/D exchange occurs at 60 degrees C at all three Tp positions and the phenyl ring. TpRu(PMe3)2Cl, TpRu(PMe3)2OTf (OTf = trifluoromethanesulfonate), and TpRu(PMe3)2SH do not initiate H/D exchange in C6D6 after extended periods of time at elevated temperatures. Mechanistic studies indicate that the likely pathway for the H/D exchange involves ligand dissociation (PMe3 or NCMe), Ru-mediated activation of an aromatic C-D bond, and deuteration of basic nondative ligand (hydroxide or anilido) or Tp positions via net D+ transfer.

Nucleophilic aromatic substitution on aryl-amido ligands promoted by oxidizing osmium(IV) centers.

Addition of amine nucleophiles to acetonitrile solutions of the OsIV anilido complex TpOs(NHPh)Cl2 (1) [Tp = hydrotris(1-pyrazolyl)borate] gives products with derivatized anilido ligands, i.e., TpOs[NH-p-C6H4(N(CH2)5)]Cl2 (2) from piperidine and TpOs[NH-p-C6H4N(CH2)4]Cl2 (3) from pyrrolidine. These materials are formed in approximately 30% yield under anaerobic conditions, together with approximately 60% yields of the OsIII aniline complex TpOs(NH2Ph)Cl2 (5). Formation of the para-substituted materials 2 or 3 from 1 involves oxidative removal of two hydrogen atoms (two H+ and two e-). The oxidation can be accomplished by 1, forming 5, or by O2. Related reactions have been observed with other amines and with the 2-naphthylamido derivative, which gives an ortho-substituted product. Kinetic studies indicate an addition-elimination mechanism involving initial attack of the amine nucleophile on the anilido ligand. These are unusual examples of nucleophilic aromatic substitution of hydrogen. Ab initio calculations on 1 show that the LUMO has significant density at the ortho and para positions of the anilido ligand, resembling the LUMO of nitrobenzene. By analogy with nucleophilic aromatic substitution, 2 is quantitatively formed from piperidine and the p-chloroanilide TpOs(NH-p-C6H4Cl)Cl2 (7). Binding the anilide ligands to an oxidizing OsIV center thus causes a remarkable umpolung or inversion of chemical character from a typically electron-rich anilido to an electron-deficient aromatic functionality. This occurs because of the coupling of redox changes at the TpOsIV center with bond formation at the coordinated ligand.

Fluxional and Rigid (Trimethylphosphane)cobalt Complexes Containing Chelating (2‐Diphenylphosphanyl)anilido Ligands

Abstract2‐(Diphenylphosphanyl)anilines (P∧NHR) eliminate methane upon reaction with [CoMe(PMe3)4] forming the complexes [Co(η2‐P∧NR)(PMe3)3] (1: R = H; 2: R = Me) and [Co(η2‐P∧NR)(PMe3)2] (3: R = Me). Reaction with HCl gives [CoCl(η1‐P∧NHR)(PMe3)2] (4: R = H; 5: R = Me) and reaction with CO or olefin gives [Co(η2‐P∧NR)(CO)(PMe3)2] (6: R = H; 7: R = Me) and [Co(η2‐P∧NR)(olefin)(PMe3)2] (8: R = H, olefin = C2H4; 9: R = Me, olefin = C2H4; 10: R = Me, olefin = C3H6), respectively. No catalytic transformation of the olefins was observed. Oxidation by iodomethane yields a cobalt(II) compound [CoI(η2‐P∧NR)(PMe3)2] (11: R = Me). By treating 2‐(diphenylphosphanyl)aniline with [CoMe2(PMe3)3] a methylcobalt(II) complex [CoMe(η2‐P∧NR)(PMe3)2] (12: R = H) is obtained, while an excess of the aniline produces [Co(η2‐P∧NR)2] (13: R = H; 14: R = Me) or [Co(η2‐P∧NR)2(PMe3)] (15: R = H; 16: R = Me). The methylcobalt(III) complexes mer‐trans‐[CoIMe2(η2‐P∧NR)(PMe3)2] were obtained from LiP∧NR and [CoClMe2(PMe3)3]. Dynamic 31P NMR spectra and the structures of complexes 3, 6, 12, and 13 are discussed. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

Ruthenium(II) Anilido Complexes TpRuL2(NHPh): Oxidative 4,4‘-Aryl Coupling Reactions (Tp = Hydridotris(pyrazolylborate); L = PMe3, P(OMe)3, or CO)

Reactions of the Ru(II) amido complexes TpRuL2(NHPh) (L = CO, PMe3, or P(OMe)3) with AgOTf (OTf = trifluoromethanesulfonate) yield the binuclear complexes [TpRuL2NH(C6H4−)]2[OTf]2 along with the Ru(II) amine complexes [TpRuL2(NH2Ph)][OTf] in an approximate 1:1 molar ratio. In these reactions, the two ruthenium fragments are coupled via C−H bond cleavage and C−C bond formation at the para position of anilido ligands. A resonance structure corresponding to Ru(II) metal centers linked by a diimine ligand contributes significantly to the bonding. Evidence for such a contribution comes from the diamagnetic nature of the binuclear complexes and a solid-state X-ray crystallographic study of [TpRu{P(OMe)3}2NH(C6H4−)]2[OTf]2. It is proposed that the coupled products are formed via initial single-electron oxidation followed by C−C bond formation. Variable-temperature NMR spectra of the aryl-coupled complexes are consistent with two geometrical isomers around the rigid HN−C6H4−C6H4NH bridges.

Lanthanide(II) Complexes Bearing Linked Cyclopentadienyl−Anilido Ligands: Synthesis, Structures, and One-Electron-Transfer and Ethylene Polymerization Reactions

Reactions of Ln[N(SiMe3)2]2(thf)2 (Ln = Sm, Yb) with 1 equiv of (C5Me4H)SiMe2NHPh afforded the first linked cyclopentadienyl−anilido (or amido) lanthanide(II) complexes Me2Si(C5Me4)(NPh)Ln(thf)x (1, Ln = Yb, x = 3; 2, Ln = Sm, x = 0−1) in 75−84% isolated yields. Recrystallization of 1 from toluene/hexane yielded the less solvated complex [Me2Si(C5Me4)(NPh)Yb(thf)]2 (1‘). Complex 1 adopts a monomeric structure containing one chelating Cp−anilido ligand and three thf ligands, while 1‘ forms a dimeric structure through an “intermolecular” Yb−Ph π-interaction. Reaction of 1 or 1‘ with azobenzene gave the binuclear Yb(III) complex Me2Si(C5Me4)(NPh)Yb(thf)(μ,η2: η3-N2Ph2)Yb(NPh)(C5Me4)SiMe2 (3), which contains a cis-oriented azobenzene dianion unit bonding in a η3 fashion to one Yb atom and in a η2 fashion to the other Yb atom. Reaction of 1 with 1 equiv of fluorenone gave the corresponding Yb(III) ketyl complex Me2Si(C5Me4)(NPh)Yb(thf)2(OC13H8) (4) in 75% isolated yield. Treatment of 4 with hexane/ether led to formation of the pinacolate complex [Me2Si(C5Me4)(NPh)Yb(thf)]2(μ-O2C26H16) (5), in which the pinacolate unit is arranged in a gauche conformation. Dissolving of 5 in THF cleaved the central C−C bond of the pinacolate unit in 5 and regenerated 4 quantitatively. The Sm(II) complex 2 showed moderate activity (44.8 kg of polymer (mol of Sm)-1 h-1) for the polymerization of ethylene under 1 atm at room temperature, yielding linear polyethylene with Mn = 7.26 × 105 and Mw/Mn = 1.58.

The changing structural chemistry of lithium anilide on solvation by pyridine, 4-methylpyridine or 4-tert-butylpyridine

A family of crystalline lithium anilide solvates, [{PhN(H)Li·(pyr)2}2] 1, [{PhN(H)Li·(4-Me-pyr)2}2] 2 and [{PhN(H)Li}4·(4-But-pyr)6] 3 has been synthesised by reacting the aromatic primary amide with two molar equivalents of the appropriate pyridine-based solvent (pyridine, 4-methylpyridine and 4-tert-butylpyridine, respectively) in hexane–toluene solution. X-Ray crystallographic studies have revealed three contrasting structures: 1 adopts a dinuclear, dimeric [(anilido)N–Li]2 ring arrangement with a transoid (anti) conformation of amido substituents; 2 adopts a similar arrangement but with a cisoid (syn) conformation of amido substituents; and 3 adopts a novel tetranuclear arrangement with a central [(anilido)N–Li]2 transoid ring, separating two mixed ligand [(anilido)N–Li-(pyr)N–Li] rings, made possible by the unusual μ-bonding of a 4-tert-butylpyridine ligand. A combination of 1H, 7Li and 13C NMR spectroscopic studies at 300 K suggests similar environments exist for corresponding atoms in [2H8]-toluene solutions of 1, 2 or 3. Further examination of the solution of 3 over the temperature window (300–193 K) has detected a fluxional structure involving the intramolecular exchange of two distinct types of anilido ligand, consistent with those present in the molecular structure of crystalline 3.

Rhodium and iridium complexes with 2-(diphenylphosphanyl)anilido ligands: reactions with phenylacetylene and dimethyl acetylenedicarboxylate †

Treatment of [Ir(CO)(PPh3)(‘PNMe’)] (‘PNMe’ = 2-Ph2PC6H4NMe–) with phenylacetylene resulted in oxidative addition and opening of the chelate ring to afford mono- and bis-(alkynyl) derivatives, [IrH(CCPh)(CO)(PPh3)(‘PNMe’)] 1 and [IrH(CCPh)2(CO)(PPh3)(η1-‘PN(Me)H’)] 2, respectively. Complex 2 exists as two isomers with trans-located phosphane ligands and cis- or trans-coordinated alkynyl groups. The minimum values of the spin–lattice relaxation times, T1(min), observed for the hydride ligands of the two isomers ruled out the possibility of short IrH· · ·HN contacts in 2. Combination of [Ir(CO)(PPh3)(‘PNMe’)] with dimethyl acetylenedicarboxylate (dmad) gave the irida(III)cyclopropene-like complex [Ir{C2(CO2Me)2}(CO)(PPh3)(‘PNMe’)] 3 as the expected 1∶1 adduct. In contrast, [Rh(CO)(PPh3)(‘PNMe’)] and dmad interacted by insertion of the activated alkyne into the Rh–N bond, forming the seven-membered metallaheterocycle [Rh{C(CO2Me)C(CO2Me)N(Me)C6H4PPh2-2}(CO)(PPh3)] 4. [Ir(CO)(PPh3)(‘PNH’)] (‘PNH’ = 2-Ph2PC6H4NH–) and dmad reacted to initially produce a mixture of metallacyclic [Ir{C2(CO2Me)2}(CO)(PPh3)(‘PNH’)] 5 and unchanged starting materials. Subsequent treatment with methanol resulted in the formation of the iridium(III) complex [Ir{C(O)OMe}{C(CO2Me)CH[C(O)OMe]}(PPh3)(‘PNH’)] 6, which X-ray crystallography showed to contain a chelating vinyl ligand featuring substantial carbenoid character.

Variable temperature multidimensional NMR study of anionic Rh(I) anilido [(R 3P) 2Rh(NHPh) 2] −, M + complexes

Variable temperature multidimensional NMR studies of [(R 3P) 2Rh(NHPh) 2] −, Li + complexes enabled the detection of activation of one aromatic ortho proton of each anilido ligand. This activation is not attributable to a CH oRh agostic interactions, but rather to interaction with lithium, resulting from a short distance between the lithium atom and one of the aromatic ortho hydrogens of each anilido ligand.

Bulky metal aryloxides, arylamides and sulphur and phosphorus analogues—III. Aluminium compounds derived from 2,4,6-TRI-t-butylaniline; X-ray structure of [ [formula omitted]{μ-NHC 6H 2Bu t2-4,6-C(Me) 2CH 2-2}] 2

Treatment of AlMe 3 with ArNH 2 (Ar = C 6H 2Bu t 3 t-2,4,6) in C 6H 14 at 60°C afforded [AlMe 2(μ-NHAr)] 2 ( 1). Heating the amide 1 either at 200°C for 3 h or (NMR) in C 6D 6 at 80°C for 3 weeks in a sealed tube led to methane elimination and formation of the cyclometallated compound [ AlMe {μ-NHC 6H 2Bu 2 t-4,6-C(Me) 2CH 2-2}] 2 ( 2); unexpectedly, the hydrogen atom abstracted from the N HAr ligand of 1 originated from the 2-t-butyl group rather than the NH. Deuterolysis of 2 yielded D 2NC 6H 2Bu 2 t-4,6-C(Me) 2CH 2D-2. AlCl 3 and ArNH 2 gave the 1 : 1 adduct AlCl 3(NH 2Ar) ( 3), which upon heating either at 150°C and 10 −4 torr or (NMR) in C 6D 6, at 80°C for 24 h gave isobutene and the retro-Friedel Crafts product AlCl 3(NH 2C 6H 3Bu 2 t-2,4) ( 4). An excess of LiNHAr did not react with AlMe 3, but with AlCl 3 furnished Al(NHAr) 2Cl ( 5). The X-ray structure of the cyclo-metallated compound 2 showed it to be a pentacyclic centrosymmetric dimer, containing a central (AlN) 2 square [<AlN> 1.965(6) Å], with the adjacent six-membered unsaturated alumino-heterocycles in a twisted boat conformation, one below and the other above the (AlN) 2 plane and the two anilido ligands in a transoid arrangement. The preparation of the metal anilides M(NHAr) [M = Li ( 6), SiMe 3 ( 7) or SnMe 3 ( 8)] is described.