Advances in rare earth and alkaline earth 8-quinaldinolate and pyrazolate chemistry

This thesis is concerned with two primary themes. Firstly, it describes the synthesis and structural characterisation of new homoleptic rare earth/alkaline earth (RE/AE) heterobimetallic complexes involving a 8-hydroxyquinoline derivative (2-methyl-8-hydroxyquinoline, 8-quinaldine, HMQ) accessed via pseudo-solid-state rearrangement reactions at elevated temperatures. Secondly, it focuses on the synthesis and characterisation of air- and moisture-sensitive RE and AE metal complexes of new unsymmetrically substituted pyrazolate ligands. These pyrazolate complexes were synthesised by either redox transmetallation/protolysis reactions involving the pyrazole and the organomercurial Hg(C6F5)2, or by direct reaction of the metal with the pyrazole after activation of the free metals by iodine. This work contributes significantly to the number of structurally characterised heterobimetallic RE/AE compounds containing HMQ. It also greatly broadens the insight into the coordination behaviour of unsymmetrically substituted pyrazolate ligands. Chapter 2 describes the synthesis and characterisation of homoleptic RE/AE heterobimetallic derivatives of 8-quinaldinolate. Rearrangement reactions between powdered RE(MQ)3 and AE(MQ)2 metal chelates in the presence of the flux 1,2,4,5-tetramethylbenzene (TMB) at elevated temperatures afforded the trinuclear and linear [Ln2AE(MQ)8]•xTMB (AE = Mg; Ln = Eu, Gd, Tb; x = 1/3; Ln = Er; x = 0; AE = Ca; Ln = La, Eu; x = 0) complexes. They also produced the homometallic [Mg4(MQ)8] complex and the structurally similar heterobimetallic [Sc2Mg2(MQ)8(OH)2]•2TMB species. Furthermore, the tetranuclear [Eu3Ba(MQ)11]•2TMB was structurally characterised. PXRD measurements on the bulk powders confirmed the presence of the structurally characterised complexes. Chapter 3 expands the pseudo-solid-state syntheses of homoleptic MQ complexes to include alkali metals and small inorganic anions. The polymeric [RbLn(MQ)4]n (Ln = Tb, Er) complexes and the unprecedented monomeric [KYb2(MQ)7] species, as well as the dimeric [Cs2(MQ)2(HMQ)2] complex are amongst the isolated structures. Furthermore, the first example of the η1(O)-μ3-η1(O’):η1(O’):η1(O’)-η1(O’’) carbonate ligation mode was found in the heteroleptic [Ln3(MQ)7CO3] (Ln = Eu, Er) complexes. In addition, the tetranuclear complexes [Eu4(MQ)8(μ4-O)Cl2] and [Eu4(MQ)8Cl4] showed a μ4-O cage derivative in the former, and a more linear arrangement of the ligands in the latter, both containing bridging chloro ligands. Crystallisation from an Et2O suspension yielded the triangular [Eu3(MQ)8(OH)]•2Et2O complex. Part of this research was undertaken on the MX1 beamline at the Australian Synchrotron. Chapter 4 investigates the synthesis and structural characterisation of divalent complexes of the unsymmetrically substituted 3-(2’-thienyl)-5-(trifluoromethyl)pyrazolate (ttfpz) ligand. Redox transmetallation/protolysis reactions in donor solvents produced the [M(ttfpz)2(thf)4] (M = Yb, Ca, Sr, Ba; thf = tetrahydrofuran) and [M(ttfpz)2(dme)n] (M = Ca, Sr, Yb, n = 2; M = Ba, n = 3; dme = 1,2-dimethoxyethane) complexes. The monomeric structures exhibit η2-bound pyrazolate ligands with eight-coordinate metal atoms for all complexes, except for the ten-coordinate barium complex [Ba(ttfpz)2(dme)3]. Chapter 5 is devoted to the synthesis and characterisation of trivalent [RE(ttfpz)3(solv)x] complexes. The same synthetic pathway, as described in Chapter 4, afforded the monomeric tris-thf complexes [RE(ttfpz)3(thf)3]•nsolv (RE = La, solv = PhMe, n = 0.5; RE = Sm, n = 0) and the bis-thf derivatives [RE(ttfpz)3(thf)2] (RE = Sc, Y, Ho, Lu). Reactions in dme led to the isolation of [RE(ttfpz)3(dme)2]•nsolv (RE = La, n = 0; solv = Et2O, n = 1; Eu, solv = dme, n = 1). Iodine activation reactions yielded [Tb(ttfpz)3(thf)3]•thf and also the hydrolysed [Er2(ttfpz)2(μ2-OH)2(dme)4]I2•2(ttfpzH) complex. In the pseudo-octahedral tris-thf derivatives, the pyrazolate and thf ligands display a change from a facial to a meridional arrangement corresponding with the change of the RE metal from La to Tb. Finally, in Chapter 6 the synthesis of some new symmetrically and unsymmetrically substituted pyrazoles and their complexation with a variety of metals is described. 3,5-Di-(2-furanyl)pyrazole (fu2pzH), 3,5-di-(2-thienyl)pyrazole (t2pzH) and the unsymmetrical 3-phenyl-5-(2-thienyl)pyrazole (PhtpzH) and 3-(2-furanyl)-5-(2-naphthyl)pyrazole (fu2nappzH) were synthesised and spectroscopically and structurally characterised. They were used in redox transmetallation/protolysis reactions in donor solvents and gave the divalent [Ca(Phtpz)2(thf)4] and [Ca(fu2nappz)2(thf)4•thf complexes, the trivalent [La(fu2pz)3(thf)3]•2thf and the dimeric hydroxide-bridged [Yb2(Phtpz)4(OH)2(thf)4]•3.5thf complex. Iodine activation reactions were further established as a general route to these pyrazolate complexes. They gave [Ba(Phtpz)2(thf)4] and the divalent [Yb(Phtpz)2(dme)2] complex. Moreover, [Yb(Phtpz)I(thf)4] is a heteroleptic iodo-containing species bearing an iodo ligand in a transoid arrangement with the Phtpz ligand. Part of this research was also undertaken on the MX1 beamline at the Australian Synchrotron

Advances in rare earth and alkaline earth 8-quinaldinolate and pyrazolate chemistry

This thesis is concerned with two primary themes. Firstly, it describes the synthesis and structural characterisation of new homoleptic rare earth/alkaline earth (RE/AE) heterobimetallic complexes involving a 8-hydroxyquinoline derivative (2-methyl-8-hydroxyquinoline, 8-quinaldine, HMQ) accessed via pseudo-solid-state rearrangement reactions at elevated temperatures. Secondly, it focuses on the synthesis and characterisation of air- and moisture-sensitive RE and AE metal complexes of new unsymmetrically substituted pyrazolate ligands. These pyrazolate complexes were synthesised by either redox transmetallation/protolysis reactions involving the pyrazole and the organomercurial Hg(C6F5)2, or by direct reaction of the metal with the pyrazole after activation of the free metals by iodine. This work contributes significantly to the number of structurally characterised heterobimetallic RE/AE compounds containing HMQ. It also greatly broadens the insight into the coordination behaviour of unsymmetrically substituted pyrazolate ligands. Chapter 2 describes the synthesis and characterisation of homoleptic RE/AE heterobimetallic derivatives of 8-quinaldinolate. Rearrangement reactions between powdered RE(MQ)3 and AE(MQ)2 metal chelates in the presence of the flux 1,2,4,5-tetramethylbenzene (TMB) at elevated temperatures afforded the trinuclear and linear [Ln2AE(MQ)8]•xTMB (AE = Mg; Ln = Eu, Gd, Tb; x = 1/3; Ln = Er; x = 0; AE = Ca; Ln = La, Eu; x = 0) complexes. They also produced the homometallic [Mg4(MQ)8] complex and the structurally similar heterobimetallic [Sc2Mg2(MQ)8(OH)2]•2TMB species. Furthermore, the tetranuclear [Eu3Ba(MQ)11]•2TMB was structurally characterised. PXRD measurements on the bulk powders confirmed the presence of the structurally characterised complexes. Chapter 3 expands the pseudo-solid-state syntheses of homoleptic MQ complexes to include alkali metals and small inorganic anions. The polymeric [RbLn(MQ)4]n (Ln = Tb, Er) complexes and the unprecedented monomeric [KYb2(MQ)7] species, as well as the dimeric [Cs2(MQ)2(HMQ)2] complex are amongst the isolated structures. Furthermore, the first example of the η1(O)-μ3-η1(O’):η1(O’):η1(O’)-η1(O’’) carbonate ligation mode was found in the heteroleptic [Ln3(MQ)7CO3] (Ln = Eu, Er) complexes. In addition, the tetranuclear complexes [Eu4(MQ)8(μ4-O)Cl2] and [Eu4(MQ)8Cl4] showed a μ4-O cage derivative in the former, and a more linear arrangement of the ligands in the latter, both containing bridging chloro ligands. Crystallisation from an Et2O suspension yielded the triangular [Eu3(MQ)8(OH)]•2Et2O complex. Part of this research was undertaken on the MX1 beamline at the Australian Synchrotron. Chapter 4 investigates the synthesis and structural characterisation of divalent complexes of the unsymmetrically substituted 3-(2’-thienyl)-5-(trifluoromethyl)pyrazolate (ttfpz) ligand. Redox transmetallation/protolysis reactions in donor solvents produced the [M(ttfpz)2(thf)4] (M = Yb, Ca, Sr, Ba; thf = tetrahydrofuran) and [M(ttfpz)2(dme)n] (M = Ca, Sr, Yb, n = 2; M = Ba, n = 3; dme = 1,2-dimethoxyethane) complexes. The monomeric structures exhibit η2-bound pyrazolate ligands with eight-coordinate metal atoms for all complexes, except for the ten-coordinate barium complex [Ba(ttfpz)2(dme)3]. Chapter 5 is devoted to the synthesis and characterisation of trivalent [RE(ttfpz)3(solv)x] complexes. The same synthetic pathway, as described in Chapter 4, afforded the monomeric tris-thf complexes [RE(ttfpz)3(thf)3]•nsolv (RE = La, solv = PhMe, n = 0.5; RE = Sm, n = 0) and the bis-thf derivatives [RE(ttfpz)3(thf)2] (RE = Sc, Y, Ho, Lu). Reactions in dme led to the isolation of [RE(ttfpz)3(dme)2]•nsolv (RE = La, n = 0; solv = Et2O, n = 1; Eu, solv = dme, n = 1). Iodine activation reactions yielded [Tb(ttfpz)3(thf)3]•thf and also the hydrolysed [Er2(ttfpz)2(μ2-OH)2(dme)4]I2•2(ttfpzH) complex. In the pseudo-octahedral tris-thf derivatives, the pyrazolate and thf ligands display a change from a facial to a meridional arrangement corresponding with the change of the RE metal from La to Tb. Finally, in Chapter 6 the synthesis of some new symmetrically and unsymmetrically substituted pyrazoles and their complexation with a variety of metals is described. 3,5-Di-(2-furanyl)pyrazole (fu2pzH), 3,5-di-(2-thienyl)pyrazole (t2pzH) and the unsymmetrical 3-phenyl-5-(2-thienyl)pyrazole (PhtpzH) and 3-(2-furanyl)-5-(2-naphthyl)pyrazole (fu2nappzH) were synthesised and spectroscopically and structurally characterised. They were used in redox transmetallation/protolysis reactions in donor solvents and gave the divalent [Ca(Phtpz)2(thf)4] and [Ca(fu2nappz)2(thf)4•thf complexes, the trivalent [La(fu2pz)3(thf)3]•2thf and the dimeric hydroxide-bridged [Yb2(Phtpz)4(OH)2(thf)4]•3.5thf complex. Iodine activation reactions were further established as a general route to these pyrazolate complexes. They gave [Ba(Phtpz)2(thf)4] and the divalent [Yb(Phtpz)2(dme)2] complex. Moreover, [Yb(Phtpz)I(thf)4] is a heteroleptic iodo-containing species bearing an iodo ligand in a transoid arrangement with the Phtpz ligand. Part of this research was also undertaken on the MX1 beamline at the Australian Synchrotron

Divalent metal complexes (Ca, Sr, Ba, Yb) of the unsymmetrical 3-(2 '-thienyl)-5-(trifluoromethyl)pyrazolate ligand

The divalent complexes [M(ttfpz)2(thf)4] (ttfpz = 3-(2′-thienyl)-5-(trifluoromethyl)pyrazolate; M = Yb, 1, Ca, 2, Sr, 3, Ba, 4; thf = tetrahydrofuran) and [M(ttfpz)2(dme)n] (M = Ca, 5, Sr, 6, Yb, 7, n = 2; M = Ba, 8, n = 3; dme = 1,2-dimethoxyethane) have been prepared by redox transmetallation/protolysis reactions employing the free metals, Hg(C6F5)2 and ttfpzH in donor solvents and their structures determined. The monomeric structures exhibit η2-bound pyrazolate ligands with eight-coordinate metal atoms for complexes 1–7 and a ten-coordinate metal for 8. The pyrazolate ligands in the thf-complexes 1–4 as well as dme-derivatives 5 and 6 are in a transoid configuration, whilst in complex 7 the ttfpz ligands exhibit a cisoid relationship. In 8 the ligands have an intermediate role in between cisoid and transoid

Syntheses at elevated temperature and structures of lanthanoid/alkaline earth heterobimetallic derivatives of 2-methyl-8-hydroxyquinoline

Rearrangement reactions between Ln(MQ)3 and AE(MQ)2 (MQ = 8-quinaldinolate) at 200–300 °C in a 1,2,4,5-tetramethylbenzene (TMB) flux afforded the homoleptic heterobimetallic complexes [Ln2AE(MQ)8] (Ln = Eu, Gd, Tb, Er with AE = Mg; Ln = La, Eu with AE = Ca) and [Eu3Ba(MQ)11]·2TMB. From an attempt to prepare [La2Mg(MQ)8], [Mg4(MQ)8] was isolated, and it was also obtained with the heterobimetallics from syntheses in which Ln = Eu, Gd, Tb. Surprisingly, [Er3(MQ)7CO3] was isolated from an attempted synthesis of [Er2Ca(MQ)8], and the Eu analogue was prepared from Eu(MQ)3 and CaCO3 in TMB at 210 °C. The [Ln2AE(MQ)8] complexes have a trinuclear structure with a linear or nearly linear Ln–AE–Ln array. Octacoordinate Ln atoms have one terminal chelating (N, O) MQ ligand and three chelating-bridging MQ ligands that link to AE through the phenolic oxygen atoms, leading to hexacoordination of AE. In [Eu3Ba(MQ)11]·2TMB, an Eu atom is positioned above the Ba–Eu vector of a somewhat bent Eu–Ba–Eu unit. All atoms are octacoordinate, and the structure features μ3-η2(N,O):η1(O):η1(O) MQ ligands in addition to terminal chelating and chelating-bridging μ-η2(N,O):η1(O) MQ groups observed in [Ln2AE(MQ)8] complexes. The three modes of ligation are also observed in [Mg4(MQ)8] where Mg is hexacoordinate but with two different arrays. [Ln3(MQ)7CO3] complexes have a perpendicular Ln–Ln–Ln arrangement with two octacoordinate metal atoms flanking a heptacoordinate one. Carbonate binding features the new η1(O)-μ3-η1(O'):η1(O'):η1(O')-η1(O") ligation mode. The carbonate ligand chelates to each of the outer Ln atoms, which are also linked to one chelating and two chelating-bridging MQ ligands. Attached to the central Ln atom is a carbonate oxygen atom, four oxygen atoms from chelating-bridging MQ ligands and a terminal MQ chelate

The effects of light lanthanoid elements (La, Ce, Nd) on (Ar)CF-Ln coordination and C-F activation in N,N-dialkyl-N '-2,3,5,6-tetrafluorophenylethane-1,2-diaminate complexes

A new class of homoleptic organoamido rare earth complexes [Ln(LMe or LEt)3] (Ln = La, Ce, Nd; LMe/Et = p-HC6F4N(CH2)2NMe2/Et2) exhibiting (Ar)CF–Ln interactions has been isolated from redox–transmetallation/protolysis (RTP) reactions between the free metals, Hg(C6F5)2 and LMe/EtH in tetrahydrofuran, together with low yields of [Ln(LMe)2F]3 (Ln = La, Ce) or [Nd(LEt)2F]2 species, resulting from C–F activation reactions. The structures of the homoleptic complexes have eight-coordinate Ln metals with two tridentate (N,N′,F) amide ligands including (Ar)CF–Ln bonds and either a bidentate (N,F) ligand (Ln = La, Ce, Nd; LEt) or a bidentate (N,N′) ligand (Ln = Nd; LMe), in an unusual case of linkage variation. All (Ar)CF–Ln bond lengths are shorter than or similar to the corresponding Ln–NMe2/Et2 bond lengths. In [Ln(LMe)2F]3 (Ln = La, Ce) complexes, there is a six-membered ring framework with alternating F and Ln atoms and the metal atoms are eight-coordinate with two tridentate (N,N′,F) LMe ligands, whilst [Nd(LEt)2F]2 is a fluoride-bridged dimer

Novel rare earth quinolinolate complexes

The reaction of europium 8-quinolinolate Eu(OQ)3 with calcium 8-quinolinolate, Ca(OQ)2, in the flux 1,2,4,5-tetramethylbenzene (TMB) at 210 °C yields the bimetallic [Eu2Ca(OQ)8], which is a linear tri-nuclear complex with two eight coordinate europium atoms flanking a six coordinate calcium atom bonded by six bridging phenolate oxygen atoms. A similar reaction between La(OQ)3 and Co(OQ)2 gave [LaCo2(OQ)7], in which two six coordinate cobalt atoms flank an eight coordinate lanthanum atom with six bridging phenolate oxygen atoms and a terminal OQ group

CCDC 877596: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 877595: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 877594: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures