A series of cobalt(II) complexes of a highly electron-withdrawing amido ligand, [N(C6F5)(C6H3Pri2-2,6)]− (L), were synthesized and structurally characterized. Mononuclear [CoL(Cl)(TMEDA)] (3) and heterobimetallic [CoL2(μ-Cl)Li(THF)3] (4) were obtained by direct metathetical reactions of anhydrous CoCl2 with one molar equivalent of [LiL(TMEDA)] (1) (TMEDA = Me2NCH2CH2NMe2) and [LiL(THF)3] (2), respectively. Complex 3 underwent facile ligand substitution reactions with LiMe and NaN3, yielding the corresponding mixed-ligand complexes [CoL(X)(TMEDA)] (X = Me 5, N36). Treatment of 3 with NaOMe led to the heterobimetallic complex [CoL2(μ-OMe)Na(TMEDA)] (7). The solid-state structures of complexes 1–7 were established by X-ray diffraction analysis.

Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (1) with potassium hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (2) and KL(THF)2 (3), respectively. Treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 afforded the corresponding Ln(II) amido complexes [EuL(μ-L)2K(THF)] (4) and [YbL2(THF)2] (5). In contrast, an analogous reaction of SmI2(THF)2 with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL3] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine yielded the trivalent [EuL3] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the bis(amido) Yb(III) iodide complex [YbL2(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(I) iodide. A subsequent reaction of 8 with KOBut gave, unexpectedly, the Yb(III) triamide [YbL3] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL3] (9) as the only isolable product. The solid-state structures of complexes 2 and 4–9 were elucidated by X-ray diffraction analysis.

A series of N2O2 tripodal tetradentate ligands derived from di-/tetra-tert-butyl substituted 2-[bis(2-hydroxybenzyl)aminomethyl]X (X = pyridine and benzimidazole) (H2Ln (n = 1–4)) and 8-[bis(3,5-di-tert-butyl-2-hydroxybenzyl)]aminoquinoline (H2L5) were synthesised through a 4-step reaction scheme involving sequential formylation, reduction, bromination and alkylation. Treatment of H2Ln (n = 1–5) with [WO2Cl2(dme)] (dme = 1,2-dimethoxyethane) in the presence of triethylamine gave the corresponding cis-dioxotungsten(VI) complexes [WO2(Ln)] (n = 1–5). The corresponding molybdenum analogues [MoO2(Ln)] (n = 1–5) were also prepared from the reaction of [MoO2(acac)2] (acac = acetylacetonate) with H2Ln (n = 1–3) or [MoO2Cl2(dme)] (dme = 1,2-dimethoxyethane) with H2Ln (n = 4 and 5). All these compounds were fully characterised by a wide range of spectroscopic methods. The molecular structures of [MoO2(Ln)] (n = 2, 4) and [WO2(L2)] were also confirmed by single-crystal X-ray diffraction analysis. The catalytic activities of [MO2(Ln)] (M = Mo, W; n = 1–4) towards epoxidation of styrene were also examined.

A new synthetic route to the known tripodal tetradentate N3O ligand L1 (HL1 = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLn (n = 2, 3) were prepared by a similar procedure. Treatment of HLn (n = 1–3) with FeCl3·6H2O in hot methanol led to the mononuclear iron(III) complexes [Fe(Ln)Cl2] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L1)Cl2] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.Mononuclear Fe(III) complexes of the general formula [Fe(Ln)Cl2] (1: n = 1, 2: n = 2, 3: n = 3), where Ln are N-capped tripodal tetradentate N3O ligands, were synthesised and structurally characterised. Complex 1 exhibited significant DNA cleavage activity in the presence of H2O2.

Neutral mononuclear lanthanide(II) bis(amidinate) complexes [LnL2(THF)x] [L = PhC(NSiMe3)(NC6H3Pri2-2,6)−; Ln = Sm, x = 2 (3); Ln = Eu, x = 2, (4); Ln = Yb, x = 1 (5)] were synthesized by the reaction of the appropriate LnI2(THF)2 with potassium amidinate [KL]n (2). The reduction chemistry of 3−5 was also examined. The reaction of the Sm(II) and Eu(II) amidinates 3 and 4 with diphenyl dichalcogenides PhEEPh (E = Se, Te) led to the binuclear lanthanide(III) amidinate-chalcogenolate complexes [LnL2(μ-EPh)]2 [Ln = Sm, E = Se (6); Ln = Eu, E = Se (7); Ln = Sm, E = Te (9)], whereas reacting the Yb(II) bis(amidinate) 5 with PhSeSePh yielded the mononuclear [YbL2(SePh)(THF)] (8). The reaction of 5 with iodine led to the Yb(III) bis(amidinate) iodide complex [YbL2(I)(THF)] (10). Treatment of 3 with N,N′-dicyclohexylcarbodiimide afforded the mixed-ligand Sm(III) tris(amidinate) [SmL2{CyNC(H)NCy}] (11) (Cy = cyclohexyl). The molecular structures of complexes 2−5 and 7−11 were elucidated by X-ray diffraction analyses.

The air-sensitive bis(µ-iodo)dicopper(I) complex 1 supported by [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine (L) has been prepared by treating copper(I) iodide with L in anhydrous THF. Compound 1 crystallizes as a dimer in space group C2/c. Each copper(I) center has distorted tetrahedral N2I2 coordination geometry with Cu–N(pyridyl) distances 2.061(3) and 2.063(3) Å, Cu–I distances 2.6162(5) and 2.7817(5) and a Cu⋯Cu distance of 2.9086(8) Å. Complex 1 is rapidly oxidized by dioxygen in CH2Cl2 with a 1 : 1 stoichiometry giving the bis(µ-iodo)peroxodicopper(II) complex [Cu(L)(µ-I)]2O2 (2). The reaction of 1 with dioxygen has been characterized by UV-vis, mass spectrometry, EPR and Cu K-edge X-ray absorption spectroscopy at low temperature (193 K) and above. The mass spectrometry and low temperature EPR measurements suggested an equilibrium between the bis(µ-iodo)peroxodicopper(II) complex 2 and its dimer, namely, the tetranuclear (peroxodicopper(II))2 complex [Cu(L)(µ-I)]4O4 (2′). Complex 2 undergoes an effective oxo-transfer reaction converting PPh3 into OPPh3 under anaerobic conditions. At sufficiently high concentration of PPh3, the oxygen atom transfer from 2 to PPh3 was followed by the formation of [Cu(PPh3)3I]. The dioxygen reactivity of 1 was compared with that known for other halo(amine)copper(I) dimers.

The unsymmetrical benzamidinate ligand [PhC(NSiMe3)(NAr)]− (Ar=2,6-Me2C6H3), denoted L−, and its lithium derivative [LiL(TMEDA)] (1) (TMEDA=N,N,N′,N′-tetramethylethylenediamine) have been prepared. Treatment of 1 with MCl2 (M=Mn, Co, Fe or Ni) afforded the corresponding divalent transition metal benzamidinates with interesting molecular structures. The reaction of two equivalents of 1 with MnCl2 or CoCl2 afforded the centrosymmetric binuclear complexes [(ML2)2·(TMEDA)] (M=Mn 2, Co 5). On the other hand, the reaction of FeCl2 with 1, in an appropriate stoichiometric ratio, led to the mononuclear mono(benzamidinate) [FeL(Cl)(TMEDA)] (3) and the bis(benzamidinate) [FeL2(TMEDA)] (4) complexes. The addition of two equivalents of 1 to NiCl2 yielded the mononuclear [NiL2] (6). X-Ray crystallography revealed that the κ2-benzamidinate ligand L− is bonded to the metal centre of these complexes in an unsymmetrical fashion. The TMEDA ligand in 2–5 exhibits different coordination modes. It acts as a chelating ligand in 3, as a monodentate ligand in 4, and as an unusual N,N′-bridging ligand in 2 and 5.

Treatment of [MO2Cl2·(DME)] (M = Mo, W; DME = 1,2-dimethoxyethane) with the lithium reagents LiLn [L1 = −N(SiMe3)(2-C5H3N-6-Me), L2 = −N(SiButMe2)(2-C5H3N-6-Me), L3 = −N(SiButPh2)(2-C5H3N-6-Me)] afforded the corresponding cis-dioxo-Mo(VI) amido complexes [MoO2(Ln)2] (Ln = L11, Ln = L22, Ln = L33) and cis-dioxo-W(VI) amido complexes [WO2(Ln)2] (Ln = L14, Ln = L25, Ln = L36). X-Ray crystallography shows that compounds 1, 2, 4 and 5 are mononuclear with the amido ligands bound to the metal centres in a N,N-chelating fashion forming highly strained four-membered metallacyclic rings with biting angles Namido–M–Npy around 60°. The Mo–Namido and W–Namido distances are comparable which fall in the range of 2.070–2.081 Å.

Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (1) with potassium hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pri2-2,6)(2-C5H3N-6-Me)] (2) and KL(THF)2 (3), respectively. Treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 afforded the corresponding Ln(II) amido complexes [EuL(μ-L)2K(THF)] (4) and [YbL2(THF)2] (5). In contrast, an analogous reaction of SmI2(THF)2 with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL3] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine yielded the trivalent [EuL3] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the bis(amido) Yb(III) iodide complex [YbL2(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(I) iodide. A subsequent reaction of 8 with KOBut gave, unexpectedly, the Yb(III) triamide [YbL3] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL3] (9) as the only isolable product. The solid-state structures of complexes 2 and 4–9 were elucidated by X-ray diffraction analysis.

A series of cobalt(II) complexes of a highly electron-withdrawing amido ligand, [N(C6F5)(C6H3Pri2-2,6)]− (L), were synthesized and structurally characterized. Mononuclear [CoL(Cl)(TMEDA)] (3) and heterobimetallic [CoL2(μ-Cl)Li(THF)3] (4) were obtained by direct metathetical reactions of anhydrous CoCl2 with one molar equivalent of [LiL(TMEDA)] (1) (TMEDA = Me2NCH2CH2NMe2) and [LiL(THF)3] (2), respectively. Complex 3 underwent facile ligand substitution reactions with LiMe and NaN3, yielding the corresponding mixed-ligand complexes [CoL(X)(TMEDA)] (X = Me 5, N36). Treatment of 3 with NaOMe led to the heterobimetallic complex [CoL2(μ-OMe)Na(TMEDA)] (7). The solid-state structures of complexes 1–7 were established by X-ray diffraction analysis.

A series of N2O2 tripodal tetradentate ligands derived from di-/tetra-tert-butyl substituted 2-[bis(2-hydroxybenzyl)aminomethyl]X (X = pyridine and benzimidazole) (H2Ln (n = 1–4)) and 8-[bis(3,5-di-tert-butyl-2-hydroxybenzyl)]aminoquinoline (H2L5) were synthesised through a 4-step reaction scheme involving sequential formylation, reduction, bromination and alkylation. Treatment of H2Ln (n = 1–5) with [WO2Cl2(dme)] (dme = 1,2-dimethoxyethane) in the presence of triethylamine gave the corresponding cis-dioxotungsten(VI) complexes [WO2(Ln)] (n = 1–5). The corresponding molybdenum analogues [MoO2(Ln)] (n = 1–5) were also prepared from the reaction of [MoO2(acac)2] (acac = acetylacetonate) with H2Ln (n = 1–3) or [MoO2Cl2(dme)] (dme = 1,2-dimethoxyethane) with H2Ln (n = 4 and 5). All these compounds were fully characterised by a wide range of spectroscopic methods. The molecular structures of [MoO2(Ln)] (n = 2, 4) and [WO2(L2)] were also confirmed by single-crystal X-ray diffraction analysis. The catalytic activities of [MO2(Ln)] (M = Mo, W; n = 1–4) towards epoxidation of styrene were also examined.