Synthesis and coordination chemistry of a photoswitchable bis(phosphine) ligand

A 1,2-dithienylethene compound bearing bis(phosphine) groups (1o) represents a new class of photoresponsive ligands where there are steric and electronic differences between two photogenerated isomers. The coordination chemistry of this ligand class is demonstrated by preparing a gold(I) complex (2o) and a phosphine selenide (3o).     

Synthesis of C2-chiral bifunctionalised spin labels and their application to troponin C

An enantiomeric pair of C2-chiral bifunctionalised spin labels having a pyrrolidine nitroxide moiety, whose configurations were determined by X-ray crystal diffraction analysis, was prepared and applied to troponin C whose binding mode of double disulfide linkage was proved by EPR spectroscopy.     

Amino-closo-dodecaborate--a new ligand in coordination chemistry

The synthesis and characterization of three ruthenium complexes [Bu(3)MeN][Ru(PPh(3))(2)(NH(2)-B(12)H(11))Cl], [Bu(4)N][Ru(dppb)(NH(2)-B(12)H(11))Cl] and [RuCO(PPh(3))(2)(NH(2)-B(12)H(11))] with amino-closo-dodecaborate as the coordinating ligand are described.     

Synthesis, characterization and coordination chemistry of a macrocyclic ligand containing arsenic donors

The preparation and characterization of the macrocyclic diamido-diarsine ligand [As2N2]Li2(1,4-dioxane) (1) (where As2N2 = PhAs(CH2SiMe2NSiMe2CH2)2AsPh) and a series of early transition metal complexes are presented. The complexes [As2N2]MCl2 (M = Zr, 2; Ti, 4) and the complex ([As2N2]Y)2(mu-Cl)2 (5) can be prepared by reaction of 1 with the corresponding THF adduct of the metal halide. The iodide derivative of 2, [As2N2]ZrI2 (3) can be prepared by reaction with iodotrimethylsilane. The lithium complex 1 displays a very long lithium-arsenic bond distance of 3.162(10) A, and the yttrium complex 5 is the first known complex containing a yttrium-arsenic bond. Reduction of 2, 3 or 4 using C8K or activated magnesium decomposed the complexes in such a manner that the ligand was separated from the metal centre. Indirect evidence suggests this may be due to reduction of arsenic in the ligand in preference to the metal.     

Synthesis and coordination chemistry of organoiridium complexes supported by an anionic tridentate ligand

Treatment of deprotonated N-(dimethylaminoethyl)-2-diphenylphosphinoaniline with bis(cyclooctene)iridium chloride dimer affords a thermally stable iridium(I) olefin complex. Infrared analysis of the corresponding monocarbonyl iridium(I) compound indicates a relatively electron rich metal center. Reaction of the iridium(I) cyclooctene complex with iodomethane effects oxidation of the metal yielding a five-coordinate iridium(III) methyl iodide complex which reversibly coordinates tetrahydrofuran. X-ray crystallography confirms coordination of ether to the iridium(III) methyl iodide complex and NMR spectroscopic experiments establish an equilibrium constant of 1.66(9) M for tetrahydrofuran binding. A five-coordinate iridium(III) dimethyl complex has also been prepared and characterized by X-ray diffraction. Hydrogenolysis of the dialkyl species permits identification of a short-lived classical iridium(III) dihydride complex.     

Synthesis and coordination chemistry of an alkyne functionalised bis(pyrazolyl)methane ligand

The alkyne functionalised bidentate N-donor ligand (2-propargyloxyphenyl)bis(pyrazolyl)methane was prepared in high yield from the reaction of (2-hydroxyphenyl)bis(pyrazolyl)methane with propargyl bromide in the presence of base. A series of transition-metal complexes including [MCl2] (M=Cu, Co, Ni, Zn, Pt), [M2](NO3)2 (M=Cu, Co, Ni, Zn), [Ag]NO3 and [Pd(dppe)](OTf)2 were prepared and characterised by spectroscopic techniques. In addition, ligand as well as the Co(II) and Zn(II) complexes [CoCl2]2, [ZnCl2] were structurally characterized by single-crystal X-ray diffraction. The organometallic gold(I) and platinum(II) acetylide complexes [Pz2CH(C6H(4)-2-OCH2C[triple bond, length as m-dash]CAuPPh3)] and trans-[{Pz2CHC6H(4)-2-OCH2C[triple bond, length as m-dash]C}2Pt(PPh3)2] were prepared from and [AuCl(PPh3)] and trans-[PtCl2(PPh3)2], respectively. Treatment of these complexes with [Pd(OTf)2(dppe)] or [Cu(MeCN)4]PF6 results in formation of the cationic, mixed-metal complexes, which were isolated (Pt/Pd, Au/Pt) or detected by electrospray mass spectrometry (Au/Cu, Pt/Cu).     

Synthesis and coordination chemistry of tetrabutyldithioimidodiphosphinates

Butyl substituted imidodithiophosphinates R₂P(S)NP (S)R′₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBu) have been synthesised via an HBr elimination reaction between R₂P(S)NH₂ and R′₂P(S)Br The compounds were characterised spectroscopically Crystallographic and spectroscopic studies reveal ⁿBu₂P(S)NHP(S)ⁿBu₂ and ^sBu₂P(S)NHP(S)ⁱBu₂ to be hydrogen bonded transoid dimers and ⁱBu₂P(S)NHP(S)ⁱBu₂ to be a transoid hydrogen bonded chain Reactions of the imidodithiophosphinates with ZnCl₂ or MCl₂COD gave the coordination complexes M[R₂P(S)NP (S)R′₂]₂ (R=ⁿBuⁱBu^sBuR′=ⁿBuⁱBu^sBuM=ZnPd: R=ⁿBuⁱBu^sBuPt).     

Synthesis,characterization, and coordination chemistry of the 2-azaphenalenyl radical

The 2-azaphenalenyl radical 2 has been synthesized and characterized by ESR spectroscopy. Variable-temperature ESR measurements were carried out on both the phenalenyl (1) and the 2-azaphenalenyl (2) radicals. The phenalenyl radical 1 has the known propensity to dimerize at temperatures below 20 degrees C, but unexpectedly less so than originally reported. The first experimental measurement of bond dissociation enthalpy for the dimerization of the phenalenyl radical 1 was obtained in CCl(4) (11.34 +/- 0.11 kcal/mol) and toluene (9.8 +/- 0.7 kcal/mol). The 2-azaphenalenyl radical 2 does not show a propensity to dimerize over the measurable temperature range (220-330 K), but does so in the presence of Cu(hfac)(2) (hfac = hexafluoroacetylacetonate). The latter complex was characterized by X-ray crystallography.     

Synthesis and coordination chemistry of tri-substituted benzamidrazones

A series of N(1),N(1),N(3)-tri-substituted benzamidrazones of the general formula [PhC(NHR)=NNMe(2)] (R = Me, n-Pr, i-Pr, n-Bu, Bn, Ph; 1a-f) was synthesized via condensation of 1,1-dimethylhydrazine with the corresponding imidoyl chloride, [PhC(Cl)=NR]. Multinuclear NMR data, and zero-point energy DFT calculations conducted with the B3LYP functional and 6-31G+(d,p) basis set, suggest that these compounds exist as a single tautomer in solution; possessing a weak intramolecular hydrogen bond and a structure dominated by the localised resonance structure ArC(NHR)=N-NMe(2). An X-ray crystallographic study upon PhC(NHPh)=NNMe(2) (1f) demonstrated that this compound adopts an identical tautomer in the solid state. Reactions of [PhC(NHMe)=NNMe(2)] (1a) with [LMCl(2)](2) (M = Ru, L = cymene; M = Rh, Ir, L = Cp*) results in the stoichiometric formation of products of the formula [LM{PhC(=NMe)NHNMe(2)}Cl](+)Cl(-) (2a-c) in which the amidrazone chelates the metal in a κ(2)-N(1),N(3)-coordination mode. Formation of this five-membered chelate occurs with a concomitant tautomerisation of the amidrazone ligand to an alternative tautomer, i.e. [PhC(=NMe)NHNMe(2)], the latter tautomer is expected to be readily energetically accessible based upon the aforementioned DFT calculations. This series of salts may be deprotonated with lithium hexamethyldisilazide to form the corresponding charge neutral complexes [LM{PhC(NMe)=NNMe(2)}] (3a-c). In contrast, the reaction of N(1),N(1),N(3)-tri-substituted benzamidrazones with [(cymene)RuCl(2)](2) in the presence of NaOAc yielded a mixture of cyclometallation (C-H activation) and amidrazone chelation/deprotonation (N-H activation) products. Reaction of 1a yielded an inseparable mixture of products, whilst the reaction of 1c resulted in formation of the cyclometallated product [LM{C(6)H(5)C(=N(i)Pr)NHNMe(2)}] (L = cymene, M = Ru; 4a) in a modest 62% yield. This latter complex could be isolated as a crystalline orange solid, full characterisation including single crystal X-ray diffraction demonstrated that the amidrazone coordinates in a κ(2)-N(2),C-coordination mode.     

Synthesis, structure and coordination of the ambiphilic ligand (2-picolyl)BCy2

The new pyridine-borane compound (2-picolyl)BCy2, readily prepared from 2-picolyllithium and ClBCy2, adopts a head-to-tail dimeric structure in the solid state as indicated by X-ray diffraction analysis and according to NMR and DFT studies, the dimeric form equilibrates in solution with a strained monomeric structure; the ambiphilic behavior of the new compound is illustrated by its bridging coordination to the (p-cymene)RuCl2 unit.     

Preparation and coordination complex of the first imine-bridged tetrathiafulvalene-pyridine donor ligand

The first imine-bridged pyridyltetrathiafulvalene building block (TTF-CH=N-Py, 1) has been synthesized via the Schiff base condensation of formyltetrathiafulvalene and 2-aminopyridine. The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [CuII(hfac)2(TTF-CH=N-Py)] (2) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center, thus making this ligand an attractive precursor for the assembly of pi-d systems.     

Synthesis and coordination chemistry of perfluoroalkylated dithiophosphate ligands

Dithiophosphoric acids [HS₂P(OC₂H₄C_nF_2n+1)₂] (n = 4, 6) have been prepared in high yields. Deprotonation and reaction with transition metal substrates affords fluorous metal complexes which have been characterised by elemental analysis, mass spectrometry, IR and NMR spectroscopies. The structures of [Cu{S₂P(OC₂H₄C_nF_2n+1)₂}(PPh₃)₂] (n = 4, 6) and [Cu{-S₂P(OC₂H₄C₄F₉)₂}(PPh₃)]₂ have been determined by single crystal X-ray diffraction.     

Synthesis and coordination chemistry of fluorinated phosphonic acids

Phosphonic acids [(HO)₂P(O)C₂H₄C_nF_2n+1] (n = 4, 6) and [(HO)₂P(O)C₆H₄-4-C_nF_2n+1] (n = 0, 1, 6) have been prepared in good yields. Deprotonation and reaction with cis-[PtCl₂(PPh₃)₂] affords fluorinated platinum complexes which have been characterised by elemental analysis, mass spectrometry, IR and NMR spectroscopies. The structures of [Pt{O₂P(O)C₆H₄-4-F}(PPh₃)₂], [Pt{O₂P(O)C₆H₄-4-CF₃}(PPh₃)₂] and [Pt{O₂P(O)C₂H₄C₆F₁₃}(PPh₃)₂] have been determined by single crystal X-ray diffraction.     

Synthesis and coordination chemistry of fluorinated xanthate ligands

Alkali metal, copper, nickel and rhodium complexes of alkylated [S₂COC₈H₁₇] and fluoroalkylated xanthate ligands [S₂COC_mH_2mC_nF_2n+1] (m = 2, n = 4, 6; m = 3, n = 1, 8) have been prepared in high yields and characterised by elemental analysis, mass spectrometry, IR and NMR spectroscopies. The structures of [Cu(S₂COC₈H₁₇)(PPh₃)₂], [Cu(S₂COC₃H₆CF₃)(PPh₃)₂], [Ni(S₂COC₃H₆CF₃)₂], [Cp^*RhCl(S₂COC₈H₁₇)] and [Cp^*RhCl(S₂COC₃H₆CF₃)] have been determined by single crystal X-ray diffraction.     

Asymmetric polymerization of triphenylmethyl methacrylate by C2-chiral catalysts

Asymmetric polymerization of triphenylmethyl methacrylate (TrMA) was investigated with optically active anionic catalysts in toluene at ?78°C. The catalysts were prepared in various combinations of organolithium compounds with C²-chiral tertiary diamines ( 1 – 6 ). Tetramethyl-ethylenediamine derivative bearing an axially dissymmetric biphenyl moiety ( 1 ) and the binaphthyl analogue ( 4 ) were found to provide efficient catalysts for the preparation of highly isotactic poly(TrMA)s of very large optical rotations whose signs depended on the configurations of the diamines. Especially, the catalysts consisting of 1 gave nearly pure one-handed helical polymers soluble in tetrahydrofuran (THF) in excellent yields, regardless of the kind of the lithium compounds used. The BuLi- 1 catalyst caused the metallation of toluene used as the solvent, and hence the resulting polymer had a benzyl moiety as an initiator fragment. The polymerization was also discussed with respect to the mole ratio of 1 to BuLi. Circular dichroism (CD) spectra of the (?)- and (+)-polymers, which were obtained with the BuLi-(R)- 1 and -(S)- 1 catalysts, respectively, were virtually complete mirror images of each other. High performance liquid chromatography (HPLC) using the THF–soluble, optically active poly(TrMA) as chiral adsorbent realized the complete resolution of racemic compounds.     

Synthesis and coordination chemistry of perfluoroalkyl-derivatised β-diketonates

A series of fluorinated β-diketones, R_fC(O)CH₂C(O)R_f′ (R_f=C₆F₁₃, R_f′=CF₃; R_f=R_f′=C₆F₁₃, C₇F₁₅), have been prepared in reasonable yields by a two-step synthesis. On reaction with appropriate metal substrates, deprotonation and concurrent coordination of the perfluoroalkyl-derivatised β-diketonate ligands affords a range of fluorous metal complexes which have been characterised by elemental analysis, mass spectrometry, IR and NMR spectroscopies. The structures of [Cu(L-L)₂(H₂O)₂] {L-L=CF₃C(O)CHC(O)C₆F₁₃, C₆F₁₃C(O)CHC(O)C₆F₁₃} and [Cu(PPh₃)₂{C₇F₁₅C(O)CHC(O)C₇F₁₅}] have been determined by single-crystal X-ray diffraction.     

Advances in the coordination chemistry of nitrogen ligand complexes of coinage metals

Coinage metals nitrogen chemistry has not been studied extensively until recently. The focus of this review is the base- and halide-free complexes of the monoanionic nitrogen ligands. This review describes how minor ligand modifications can result in a drastic change in the metal–metal interactions in multinuclear compounds. Crystal structures of these complexes show individual complexes, dimers, supramolecular columnar packing or more complex supramolecular aggregates. Bulky substituents on the ligands can prevent intermolecular metal–metal interactions or the formation of supramolecular architectures. The nuclearity and metal–metal interactions in these complexes are controlled by ligand steric and electronic factors and solvent of crystallization. Many classes of nitrogen ligand coordination compounds have given rise to advances in several fundamental and applied research aspects. Recent potential applications of nitrogen ligand complexes are highlighted particularly for those complexes included in this review.     

Lanthanum and alkali metal coordination chemistry of the bis(dimethylphenylsilyl)amide ligand

The coordination chemistry of the bis(dimethylphenylsilyl)amide ligand, [N(SiMe2Ph)2]1-, with sodium, potassium, and lanthanum has been investigated for comparison with the more commonly used [N(SiMe3)2]1- and [N(SiHMe2)2]1- ligands. HN(SiMe2Ph)2 reacts with KH to produce KN(SiMe2Ph)2, 1, which crystallizes from toluene as the dimer [KN(SiMe2Ph)2(C7H8)]2, 2. The structure of 2 shows that the [N(SiMe2Ph)2]1- ligand can function as a polyhapto ligand with coordination from each phenyl group as well as the normal nitrogen ligation and agostic methyl interactions common in methylsilylamides. Each potassium in 2 is ligated by an eta4-toluene, two bridging nitrogen atoms, and an eta2-phenyl, an eta1-phenyl, and an eta1-methyl group. KN(SiMe2Ph)2 crystallizes from toluene in the presence of 18-crown-6 to make the monometallic complex (18-crown-6)KN(SiMe2Ph)2, 3, in which [N(SiMe2Ph)2]1- functions as a simple monodentate ligand through nitrogen. The reaction of HN(SiMe2Ph)2 with NaH in THF at reflux for 2 days generates Na[N(SiMe2Ph)2], 4, which crystallizes as the solvated dimer {(THF)Na[mu-eta1:eta1-N(SiMe2Ph)2]}2, 5. A lanthanide metallocene derivative of [N(SiMe2Ph)2]1- was obtained by reaction of K[N(SiMe2Ph)2] with [(C5Me5)2La][(mu-Ph)2BPh2]. Crystals of (C5Me5)2La[N(SiMe2Ph)2], 6, show agostic interactions between lanthanum and methyl groups of each silyl substituent. The [N(SiMe3)2]1- analogue of 3, (18-crown-6)KN(SiMe3)2, 7, was also structurally characterized for comparison.     

Synthesis and coordination chemistry of ferrocenyl-1,2,3-triazolyl ligands

"Click" reactions between ethynylferrocene and mono-, bis-, and tris-azido aromatic derivatives yielded mono-, bis-, and tris-1,2,3-ferrocenyltriazoles (1, 2, and 3, respectively) as orange crystals. The X-ray crystal structure of the monoferrocenyltriazole compound 1 was solved with two nearly identical molecules within the asymmetric unit. In both molecules, the two Cp rings make a tilt angle of 2.1(3) degrees [0.7(3) degrees], and they are roughly eclipsed with a twist angle of 2.4(3) degrees [1.8(3) degrees]. Reaction of 1 with [PdCl2(PhCN)2] in dimethylsulfoxide (DMSO) yielded orange crystals of [PdCl2L2] (4; L=1), for which the X-ray crystal structure shows trans coordination to the nitrogen atom close to the ferrocene substitution. The Pd atom is located on an inversion center and displays a nearly perfect square planar environment. In DMSO-d6, 4 reversibly dissociates to regenerate 1, whose (1)H NMR spectrum is then observed. The 1H NMR study also shows that progressive addition of PdCl2 or [PdCl2(NCR)2] (R=Me or Ph) to DMSO-d6 solutions of 1 reversibly leads to the formation of 4 and the addition of excess PdII is necessary to lead to the complete disappearance of the signals of 1. The cyclic voltammograms of 1, 2, and 3 show the reversible oxidation wave of the ferrocenyl group, and that of 4 shows that this wave appears with increased intensity tentatively attributable to redox-catalyzed oxidation.     

Synthesis and coordination chemistry of 1-cymantrenyl-2,3,4,5-tetraphenylborole

In this contribution, we report the synthesis of base-free 1-cymantrenyl-2,3,4,5-tetraphenylborole and two of its Lewis base adducts. In addition, the structural characterization and investigation of the photophysical properties are provided.