John Fawcett

Room-temperature cyclometallation of amines, imines and oxazolines with [MCl2Cp*]2(M = Rh, Ir) and [RuCl2(p-cymene)]2

N,N-Dimethylbenzylamine, alkyl and aryl imines derived from benzaldehyde, and 2-phenyl-4,4-dimethyloxazoline all undergo cyclometallation with [IrCl2Cp*]2 (Cp* = η-C5Me5) when treated with NaOAc in dichloromethane at room temperature. The imines are also cyclometallated by [RhCl2Cp*]2 under the same conditions whilst only N-alkyl imines are cyclometallated by [RuCl2(p-cymene)]2. The role of acetate in the cyclometallation is more than just as a base. X-Ray structures of cyclometallated complexes [MCl{C6H4-2-C(H)NCH2CH2OMe-κC,N}(η-ring)](M = Ir, Rh ring = Cp*; M = Ru, ring = p-cymene), [MCl{C6H4-2-C(H)NCH2CH2OMe-κC,N}Cp*](M = Ir, Rh), [RuCl(η2-O2CMe)(p-cymene)] and [IrCl2(NH2Ph)Cp*] are reported.

Phosphorus(III) ligands in fluorous biphase catalysis

Abstract The synthesis, coordination chemistry and catalytic applications of a series of perfluoroalkyl-substituted phosphorus(III) ligands is illustrated.

Arene-ruthenium complexes with salicyloxazolines: diastereoselective synthesis, configurational stability and applications as asymmetric catalysts for Diels-Alder reactions.

Reaction of the dimers [RuCl2(eta6-arene)]2 (arene = benzene, p-cymene, mesitylene) with salicyloxazolines in the presence of NaOMe gives complexes [RuCl(R-saloxaz)(arene)] (1-5) which have been fully characterised. Complexes [RuL(iPr-saloxaz)(mes)]Y (L = py, 2-Mepy, 4-Mepy; PPh3; Y- = SbF6 or BPh4) 6-9 were prepared by treating the chloride 2a with ligand L and NaY (Y- = SbF6 or BPh4) in methanol at reflux. Halide complexes [RuX(iPr-saloxaz)(mes)](X = Br, 10; X = I, 11) were synthesised by treating 2a with AgSbF6 then with 1.2 equivalents of KBr or NaI, the methyl complex [RuMe(iPr-saloxaz)(mes)] 12 was synthesised from 2a by reaction with MeLi. Five complexes, [RuCl(iPr-saloxaz)(mes)] 2a, [RuCl(tBu-saloxaz)(p-cymene)] 3b, [RuCl(Ph-saloxaz)(mes)] 5a, [Ru(4-Mepy)(iPr-saloxaz)(mes)][SbF6] 7, and [Ru(PPh3)(iPr-saloxaz)(mes)][SbF6] 9, have been characterised by X-ray crystallography. Treatment of complexes 1-5 with AgSbF6 gives cationic species which are enantioselective catalysts for the Diels-Alder reaction of acroleins with cyclopentadiene, the effect of substituents on enantioselectivity has been examined.

Structures and catalytic properties of triphenylphosphine oxide complexes of scandium and lanthanide triflates

Abstract The complexes M(OTf) 3 (Ph 3 PO) 4 where M=lanthanide metals and scandium have been prepared and characterised in the solid state by single crystal X-ray diffraction, infrared spectroscopy and elemental analysis. All the complexes have the ionic structure [M(OTf) 2 (Ph 3 PO) 4 ] + [OTf] − . Single crystal X-ray structures for M=Sc, Nd and Lu are reported. In the complexes of the early lanthanides (LaNd) the metals are seven-coordinate with one monodentate, one bidentate triflate. The smaller lanthanide ions, and scandium, have six-coordinate structures with an approximate octahedral coordination about the metal where both triflates are bound as monodentate ligands. The solution structures have been analysed by electrospray mass spectrometry, which indicates that extensive ligand redistribution occurs. The complexes catalyse the Friedel Crafts acylation, alkenylation and alkylation of activated aromatics with modest increases in selectivity compared to the same reactions using scandium triflate.

Ring-closing metathesis in carbohydrate annulation

Even eight-membered rings (such as in 2) can be formed by ring-closing metathesis of glucose derivatives such as 1. Enantiomerically pure tricyclic spiro compounds can also be prepared.

Alkyne insertion into cyclometallated pyrazole and imine complexes of iridium, rhodium and ruthenium; relevance to catalytic formation of carbo- and heterocycles.

The cyclometallated complexes [MCl(C^N)(ring)] (HC^N = 2-phenylpyrazole, M = Ir, Rh ring = Cp*; M = Ru, ring = p-cymene) readily undergo insertion reactions with RC≡CR (R = CO(2)Me, Ph) to give mono insertion products, the rhodium complex also reacts with PhC≡CH regiospecifically to give an analogous product. The products of the reactions of the cyclometallated imine complexes [MCl(C^N)Cp*] (HC^N = PhCH=NR, R = Ph, CH(2)CH(2)OMe, Me; M = Ir, Rh) with PhC≡CPh depend on the substituent R; when R = CH(2)CH(2)OMe a monoinsertion is observed, however for R = Me the initial insertion product is unstable, undergoing reductive elimination with loss of the organic fragment, and for R = Ph no metal-containing product is isolated. With PhC≡CH the cyclometallated imine complexes can give mono or di-insertion products. The implications for catalytic synthesis of carbo- and heterocycles by a tandem C-H activation, alkyne insertion mechanism are discussed.

Carbon–fluorine and –hydrogen bond activation and carbon–carbon bond formation in η5-pentamethylcyclopentadienyl-rhodium and -iridium phosphine complexes; crystal structures of [M(η5-C5Me5)Cl{(C6F5)2PCH2CH2P(C6F5)2}]+BF4–(M = Rh or Ir)

The reaction between [{M(η5-C5Me5)Cl(µ-Cl)}2](M = Rh or Ir) and (C6F5)2PCH2CH2P(C6F5)2(dfppe) in refluxing benzene yielded the cationic species [M{η5-C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}Cl]+ in which two C–F and two C–H bonds have been cleaved and two C–C bonds formed; HF is also produced. The complexes [M(η5-C5Me5)Cl(dfppe)]+BF4–(M = Rh or Ir), which have not undergone C–F bond activation, were formed by treatment of [{M(η5-C5Me5)Cl(µ-Cl)}2] with NH4BF4 and dfppe, and have been structurally characterized by X-ray crystallography. Activation of the C–F bonds in these complexes is induced by thermolysis in refluxing ethanol. The reaction between [{M(η5-C5Me5)Cl(µ-Cl)}2](M = Rh or Ir) and dfppe in refluxing ethanol yielded a mixture of the cations [M(η5-C5Me5)Cl(dfppe)]+, [M{η5-C5Me3[CH2C6F4P(C6F5)CH2]2-1,3}Cl]+ and, where M = Rh, the singly C–F bond-activated species [Rh{η5-C5Me4CH2C6F4P(C6F5)CH2CH2P(C6F5)2}Cl]+.

Zerovalent palladium and platinum complexes of aminomethylphosphines. Crystal structure of the palladium(0) dibenzylideneacetone complex [Pd(PhCHCHCOCHCHPh){((C6H11)2PCH2)2NMe}]

Abstract Tris(dibenzylideneacetone)dipalladium and bis(dibenzylideneacetone)platinum react with N, N-bis(dicyclohexylphosphinomethyl)methylamine, (Cy2PCH2)2NMe (Cy = cyclohexyl), and with N, N-bis(diphenylphosphinomethyl)methylamine, (Ph2PCH2)2NMe (Ph = phenyl), to give the complexes [M(dba){(R2PCH2)2NMe}] (M  Pd or Pt, dba = dibenzylideneac ), R  Cy or Ph. Thezerovalent platinum complex [Pt(PPh3){(Cy2PCH2)2NMe}] can be obtained by hydrazine hydrate reduction a mixture of [PtCl2Cy2PCH2)2NMe] and triphenylphosphine or one of cis-[PtCl2(PPh3)2] and (Cy2PCH2)2NMe. The crystal structure of [Pd(dba){(Cy2PCH2)2NMe}] has been determined and some reactions of the complexes are reported.

The structures of bis-maltolato-zinc(II) and of bis-3-hydroxy-1,2-dimethyl-4-pyridinonato–zinc(II) and –lead(II)

Abstract The structures of bis-(3-hydroxy-4-pyronato)zinc(II) {bis-maltolato-zinc(II), Zn(malt)2·1.5H2O}, bis-(1,2-dimethyl-3-hydroxy-4-pyridinonato)zinc(II) {Zn(L1)2·7H2O}, and bis-(1,2-dimethyl-3-hydroxy-4-pyridinonato)lead(II) {Pb(L1)2·7H2O}, determined by X-ray diffraction techniques, are reported. The zinc in {Zn(L1)2·7H2O} is five coordinated; in Zn(malt)2·1.5H2O zinc occurs in both five- and six-coordination. Pb(L1)2·7H2O is dimeric; each lead has five oxygens, two of them bridging, in its coordination shell. All three compounds contain water molecules coordinated to the metal; both L1 complexes also contain water of crystallisation in the form of extended chains. All three compounds are extensively hydrogen bonded.

Synthesis of 4,4-difluoroglycosides using ring-closing metathesis

4-Deoxy-4,4-difluoro-glycosides have been synthesised for the first time via a direct sequence involving ring-closing metathesis and indium-mediated difluoroallylation with 1-bromo-1,1-difluoropropene in water. Two protecting group strategies were explored, one to allow protection of the primary C-6 hydroxyl group throughout the sequence, while the second was intended to allow deprotection after RCM and before dihydroxylation. The benzyl ether could be used in the first role, and pivaloyl is effective in the second. Dihydroxylations were highly stereoselective and controlled by the orientation of the glycosidic C-O bond.