Group 11 complexes with the bis(3,5-dimethylpyrazol-1-yl)methane ligand. How secondary bonds can influence the coordination environment of Ag(I): the role of coordinated water in [Ag2(mu-L)2(OH2)2](OTf)2

The complexation properties of the ligand bis(3,5-dimethylpyrazol-1-yl)methane (L) towards group 11 metals have been studied. The reaction in a 1 : 1 molar ratio with [Cu(NCMe)4]PF6 or Ag(OTf) complexes gives the mononuclear [CuL(NCMe)]PF6 (1), with crystallographic mirror symmetry, or dinuclear [Ag2(mu-L)2](OTf)2 (2) (OTf = trifluoromethanesulfonate) in which the ligand bridges both silver centres, an unprecedented mode of coordination for this type of ligands. Compound 2 crystallizes with two water molecules and forms a supramolecular structure through classical hydrogen bonding. The reaction in a 2 : 1 ratio affords in both cases the four-coordinated derivatives [ML2]X (M = Cu, X = PF6 (3); Ag, X = OTf 4). The treatment of [Ag(OTf)(PPh3)] with the ligand L gives [AgL(PPh3)]OTf (5). The gold(I) derivative [Au2(C6F5)2(mu-L)] (6) has also been obtained by reaction of L with two equivalents of [Au(C6F5)(tht)]. These complexes present a luminescent behaviour at low temperature; the emissions being mainly intraligand but enhanced after coordination of the metal. Compounds 1-4 have been characterized by X-ray crystallography. DFT studies showed that, in the silver complex 2, coordination of H2O to Ag in the binuclear complex is favoured by formation of a hydrogen-bonding network, involving the triflato anion, and releasing enough energy to allow distortion of the Ag2 framework.     

Mixed-ligand molecular paneling: dodecanuclear cuboctahedral coordination cages based on a combination of edge-bridging and face-capping ligands

Reaction of a tris-bidentate ligand L(1) (which can cap one triangular face of a metal polyhedron), a bis-bidentate ligand L(2) (which can span one edge of a metal polyhedron), and a range of M(2+) ions (M = Co, Cu, Cd), which all have a preference for six coordination geometry, results in assembly of the mixed-ligand polyhedral cages [M12(mu(3)-L(1))4(mu-L(2))12](24+). When the components are combined in the correct proportions [M(2+):L(1):L(2) = 3:1:3] in MeNO2, this is the sole product. The array of 12 M(2+) cations has a cuboctahedral geometry, containing six square and eight triangular faces around a substantial central cavity; four of the eight M3 triangular faces (every alternate one) are capped by a ligand L(1), with the remaining four M3 faces having a bridging ligand L(2) along each edge in a cyclic helical array. Thus, four homochiral triangular {M3(L(2))3}(6+) helical units are connected by four additional L(1) ligands to give the mixed-ligand cuboctahedral array, a topology which could not be formed in any homoleptic complex of this type but requires the cooperation of two different types of ligand. The complex [Cd3(L(2))3(ClO4)4(MeCN)2(H2O)2](ClO4)2, a trinuclear triple helicate in which two sites at each Cd(II) are occupied by monodentate ligands (solvent or counterions), was also characterized and constitutes an incomplete fragment of the dodecanuclear cage comprising one triangular {M3(L(2))3}(6+) face which has not yet reacted with the ligands L(1). (1)H NMR and electrospray mass spectrometric studies show that the dodecanuclear cages remain intact in solution; the NMR studies show that the Cd 12 cage has four-fold (D2) symmetry, such that there are three independent Cd(II) environments, as confirmed by a (113)Cd NMR spectrum. These mixed-ligand cuboctahedral complexes reveal the potential of using combinations of face-capping and edge-bridging ligands to extend the range of accessible topologies of polyhedral coordination cages.     

Structures and dynamic behavior of large polyhedral coordination cages: an unusual cage-to-cage interconversion

The bis-bidentate bridging ligand L {α,α'-bis[3-(2-pyridyl)pyrazol-1-yl]-1,4-dimethylbenzene}, which contains two chelating pyrazolyl-pyridine units connected to a 1,4-phenylene spacer via flexible methylene units, reacts with transition metal dications to form a range of polyhedral coordination cages based on a 2M:3 L ratio in which a metal ion occupies each vertex of a polyhedron, a bridging ligand lies along every edge, and all metal ions are octahedrally coordinated. Whereas the Ni(II) complex [Ni(8)L(12)](BF(4))(12)(SiF(6))(2) is an octanuclear cubic cage of a type we have seen before, the Cu(II), Zn(II), and Cd(II) complexes form new structural types. [Cu(6)L(9)](BF(4))(12) is an unusual example of a trigonal prismatic cage, and both Zn(II) and Cd(II) form unprecedented hexadecanuclear cages [M(16)L(24)]X(32)(X = ClO(4) or BF(4)) whose core is a skewed tetracapped truncated tetrahedron. Both Cu(6)L(9) and M(16)L(24) cages are based on a cyclic helical M(3)L(3) subunit that can be considered as a triangular "panel", with the cages being constructed by interconnection of these (homochiral) panels with additional bridging ligands in different ways. Whereas [Cu(6)L(9)](BF(4))(12) is stable in solution (by electrospray mass spectrometry, ES-MS) and is rapidly formed by combination of Cu(BF(4))(2) and L in the correct proportions in solution, the hexadecanuclear cage [Cd(16)L(24)](BF(4))(32) formed on crystallization slowly rearranges in solution over a period of several weeks to the trigonal prism [Cd(6)L(9)](BF(4))(12), which was unequivocally identified on the basis of its (1)H NMR spectrum. Similarly, combination of Cd(BF(4))(2) and L in a 2:3 ratio generates a mixture whose main component is the trigonal prism [Cd(6)L(9)](BF(4))(12). Thus the hexanuclear trigonal prism is the thermodynamic product arising from combination of Cd(II) and L in a 2:3 ratio in solution, and arises from both assembly of metal and ligand (minutes) and rearrangement of the Cd(16) cage (weeks); the large cage [Cd(16)L(24)](BF(4))(32) is present as a minor component of a mixture of species in solution but crystallizes preferentially.     

Silver(I) complexes of fixed, polytopic bis(pyrazolyl)methane ligands: influence of ligand geometry on the formation of discrete metallacycles and coordination polymers

Reactions of the arene-linked bis(pyrazolyl)methane ligands m-bis[bis(1-pyrazolyl)methyl]benzene, (m-[CH(pz)2]2C6H4, Lm), p-bis[bis(1-pyrazolyl)methyl]benzene, (p-[CH(pz)2]2C6H4, Lp), and 1,3,5-tris[bis(1-pyrazolyl)methyl]benzene (1,3,5-[CH(pz)2]3C6H3, L3) with AgX salts (pz = 1-pyrazolyl; X = BF4- or PF6-) yield two types of molecular motifs depending on the arrangement of the ligating sites about the central arene ring. Reactions of the m-phenylene-linked Lm with AgBF4 and AgPF6 afford complexes consisting of discrete, metallacyclic dications: [Ag2(mu-Lm)2](BF4)2 (1) and [Ag2(mu-Lm)2](PF6)2 (2). When the p-phenylene-linked Lp is treated with AgBF4 and AgPF6, acyclic, cationic coordination polymers are obtained: {[Ag(mu-Lp)]BF4}infinity (3) and {[Ag(mu-Lp)]PF6}infinity (4). Reaction of the ligand L3, containing three bis(pyrazolyl)methane units in a meta arrangement, with an equimolar amount of AgBF4 again yields discrete metallacyclic dications in which one bis(pyrazolyl)methane unit on each ligand remains unbound: [Ag2(mu-L3)2](BF4)2 (5). Treatment of L3 with an excess of AgBF4 affords a polymer of metallacycles, {[Ag3(mu-L3)2](BF4)3}infinity (6), with one of the bis(pyrazolyl)methane units on each ligand bound to a silver cation bridging two metallacycles. The supramolecular structures of the silver(I) complexes 1-6 are organized by noncovalent interactions, including weak hydrogen bonding, pi-pi, and anion-pi interactions.     

Molecular squares, cubes and chains from self-assembly of bis-bidentate bridging ligands with transition metal dications

The two new ligands L(fur) and L(th) consist of two chelating pyrazolyl-pyridine termini connected to furan-2,5-diyl or thiophene-2,5-diyl spacers via methylene groups. Reaction of these with a range of transition metal dications that prefer octahedral coordination affords a series of unusual structures which are all based on a 2M : 3L ratio. [M(8)(L(fur))(12)]X(16) (M = Co, Cu, X = BF(4); and M = Zn, X = ClO(4)) are octanuclear cubes with approximate D(4) symmetry in which two cyclic tetranuclear helicate M(4)L(4) units are connected by four additional 'pillar' ligands. In contrast [Ni(4)(L(fur))(6)](BF(4))(8) is a centrosymmetric molecular square consisting of two dinuclear Ni(2)L(2) units of opposite chirality that are connected by a pair of additional L(fur) ligands such that the four edges of the Ni(4) square are spanned by alternately two and one bridging ligands. [M(4)(L(th))(6)](BF(4))(8) (M = Co, Ni, Cu) are likewise molecular squares with similar structures to [Ni(4)(L(fur))(6)](BF(4))(8) with the significant difference that the two crosslinked double helicate M(2)L(2) units are now homochiral. The Cd(II) complexes both behave quite differently to the first-row metal complexes, with [Cd(L(fur))(BF(4))](BF(4)) being a simple mononuclear complex with a single ligand in which the furan oxygen atom is weakly interacting with the Cd(II) centre. In contrast, in {[Cd(2)(L(th))(3)](BF(4))(4)}(∞), where this quasi-pentadentate coordination mode of the ligand is not possible because thiophene is too poor an electron donor, the ligand reverts to bis-bidentate bridging coordination to afford a one-dimensional chain consisting of an infinite sequence of crosslinked, homochiral, Cd(2)(L(th))(2) double helicate units.     

Multi-dimensional transition-metal coordination polymers of 4,4'-bipyridine-N,N'-dioxide: 1D chains and 2D sheets

Reaction of 4,4'-bipyridine -N, N' -dioxide (L) with a variety of transition-metal salts in MeOH affords a range of coordination polymer products. For the complexes [FeCl 3(mu-L)] infinity, 1, and ([Cu(L) 2(OHMe) 2(mu-L)].2PF 6. n(solv)) infinity, 2, 1D chain structures are observed, whereas ([Mn(mu-L) 3].2ClO 4) infinity, 3, and ([Cu(mu-L) 3].2BF 4) infinity, 4, both show 2D sheet architectures incorporating an unusual 3 (6)- hxl topology. The more common 4 (4)- sql topology is observed in [Cd(ONO 2) 2(mu-L) 2] infinity, 5, ([Cu(OHMe) 2(mu-L) 2].2ZrF 5) infinity, 6, ([Cu(L) 2(mu-L) 2].2EF 6) infinity ( 7 E = P; 8 E = Sb), and ([Et 4N][Cu(OHMe) 0.5(mu-L) 2(mu-FSiF 4F) 0.5].2SbF 6. n(solv)) infinity, 9. In 6, the [ZrF 5] (-) anion, formed in situ from [ZrF 6] (2-), forms 1D anionic chains ([ZrF 5] (-)) infinity of vertex-linked octahedra, and these chains thread through a pair of inclined polycatenated ([Cu(OHMe) 2(mu-L) 2] (2+)) infinity 4 (4)- sql grids to give a rare example of a triply intertwined coordination polymer. 9 also shows a 3D matrix structure with 4 (4)- sql sheets of stoichiometry ([Cu(L) 2] (2+)) infinity coordinatively linked by bridging [SiF 6] (2-) anions to give a structure of 5-c 4 (4).6 (6)- sqp topology. The mononuclear [Cu(L) 6].2BF 4 ( 10) and [Cd(L) 6].2NO 3 ( 11) and binuclear complexes [(Cu(L)(OH 2)) 2(mu-L) 2)].2SiF 6. n(solv), 12, are also reported. The majority of the coordination polymers are free of solvent and are nonporous. Thermal treatment of materials that do contain solvent results in structural disintegration of the complex structures giving no permanent porosity.     

Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: dodecanuclear and tetranuclear coordination cages and cyclic helicates

The tetradentate ligand L(naph) contains two N-donor bidentate pyrazolyl-pyridine units connected to a 1,8-naphthyl core via methylene spacers; L45 and L56 are chiral ligands with a structure similar to that of L(naph) but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(L(naph))](OTf) and [Ag(L(naph))](BF4) have unremarkable mononuclear structures, with Cu(I) being four-coordinate and Ag(I) being two-coordinate with two additional weak interactions (i.e., "2 + 2" coordinate). In contrast, [Cu4(L(naph))4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L45)](BF4) and [Ag(L45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L45)](ClO4) and [Ag4(L56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications Co(II), Cu(II), and Cd(II), L(naph) generates a series of unusual dodecanuclear coordination cages [M12(L(naph))18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L45)6](ClO4)(8), with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.     

Electron paramagnetic resonance and spectroscopic characteristics of electrogenerated mixed-valent systems [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+ (M = Rh, Ir; L = 2,5-diiminopyrazines) in relation to the radicals [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ and [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+

Electrochemical reduction of the dinuclear [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]2+ ions (M = Rh, Ir; L = 2,5-bis(1-phenyliminoethyl)pyrazine (bpip) and 2,5-bis[1-(2,6-dimethylphenyl)iminoethyl]pyrazine (bxip)) proceeds via the paramagnetic intermediates [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ (L = bpip) or [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+ (L = bxip) and [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+. Whereas the first is clearly a radical species with a small g anisotropy, the chloride-free cations are distinguished by structured intervalence charge transfer (IVCT) bands in the near-infrared region and by rhombic electron paramagnetic resonance features between g = 1.9 and g = 2.3, which suggests considerable metal participation at the singly occupied MO. Alternatives for the d configuration assignment and for the role of the bisbidentate-conjugated bridging ligands will be discussed. The main difference between bpip and bxip systems is the destabilization of the chloride-containing forms through the bxip ligand for reasons of steric interference.     

Synthesis and structures of some heterometallic [(Li, Y)2, (M3, Ce) (M = Li or Na), (Li, Zr2) and (Li, Zr)4] oligomeric diamides derived from 1,2-bis(neopentylamino)benzene

The following crystalline, X-ray-characterised heterometallic oligomeric diamides have been prepared in good yield under mild conditions in diethyl ether from the dilithio or disodio derivative of the N,N'-dineopentyl-1,2-diaminobenzene [{N(H)(CH2Bu(t))}2C6H4-1,2] (abbreviated as H2L):[Y(L)(mu-Cl)2Li(OEt2)2]2 (1), [Li(OEt2)2Li(mu2-Cl)4(mu3-Cl)2{Zr(L)}2]2 (2), [Zr(L)2(mu-Cl){Li(OEt2)2}(mu2-Cl)2Zr(L)] (3), [Ce{(mu-L)M}3(OEt2)(1/2)] (3M = Li(1.82)Na(1.18)) (4), [Ce{(mu-L)Na}3(OEt2)] (5) and [Ce{(mu-L)Na}3] (6). Compounds 1-3 were obtained from Li2(L) and YCl3 (the colourless 1) or ZrCl4 (the red 2 and 3), while the red 4 and 5 were isolated from CeCl3 and M2(L) (3M = Li(1.82)Na(1.18)) (4) or Na2(L) (5). Attempted oxidation of 5 with Br2 in hexane yielded the black 6. The ligand is N,N'-chelating to each of the d- or f-block metals in 1-6; and in 4-6 L is also acting as a bridge between Ce and the alkali metal, to which L is thus also chelating.     

Syntheses, crystal structures, and magneto-structural correlations of novel Cu(II) complexes containing a planar [Cu(mu-L1)]2 (HL1 = 3-(2-pyridyl)pyrazole) unit: from dinuclear to tetranuclear and then to one-dimensional compounds

Seven new Cu(II) complexes based on a binuclear planar unit [Cu(mu-L(1))](2), [[Cu(mu-L(1))(NO(3))(H(2)O)](2) (1), [Cu(mu-L(1))(HL(1))(ClO(4))](2) (2), [Cu(4)(mu-L(1))(6)(NO(3))(2)] (3), [Cu(4)(mu-L(1))(6)(L(1))(2)] (4), [Cu(4)(mu-L(1))(6)(mu-L(2))](n) (5), [Cu(4)(mu-L(1))(6)(mu-L(3))](n) (6), [[Cu(4)(mu-L(1))(4)(mu-L(4))(2)](H(2)O)(3)](n) (7) (HL(1) = 3-(2-pyridyl)pyrazole, L(2) = 1,8-naphthalenedicarboxylate, L(3) = terephthalate, L(4) = 2,6-pyridinedicarboxylate)}, have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. In 1 and 2, the Cu(II) centers are linked by deprotonated pyrazolyl groups to form dinuclear structures. 3 and 4 have similar gridlike tetranuclear structures in which two additional deprotonated L(1) ligands bridge two [Cu(mu-L(1))](2) units perpendicularly. 5 and 6 consist of similar one-dimensional (1-D) chains in which gridlike tetranuclear copper(II) units similar to that of 3 are further linked by L(2) or L(3) ligands, respectively. And, in 7, L(4) ligands link [Cu(mu-L(1))](2) binuclear units to form a tetranuclear gridlike structure in chelating/bridging mode and simultaneously bridge the tetranuclear units to form a 1-D chain. The magnetic properties of all complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements. The obtained parameters of J range from -33.1 to -211 cm(-1), indicating very strong antiferromagnetic coupling between Cu(II) ions. The main factor that affects the |J| parameter is the geometry of the Cu(N(2))(2)Cu entity. From the magnetic point of view, 1 and 2 feature "pure" dinuclear, 3 and 5 tetranuclear, and 4, 6, and 7 pseudodinuclear moieties.     

Conformationally rigid chelate rings in metal complexes of pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotetra- and cyclotriphosphazene platforms

Divalent metal halides react with pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotri- and cyclotetraphosphazene ligands to form the complexes, [MLX2] [M=Co or Cu; L=(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotriphosphazene (L1) or (2,2'-dioxybiphenyl)tetrakis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L2); X=Cl or Br], [ZnLCl2] [L=bis(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotriphosphazene (L3) or bis(2,2'-dioxybiphenyl)bis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L4)], [MLCl2] [M=Cu or Hg; L=tris(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotetraphosphazene (L5)] and [Cu2LCl4] (L=trans-bis(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotetraphosphazene (L6)]. Single-crystal X-ray structures show the L2 ligand complexes to have a N3Cl2 five-coordinate, trigonal-bipyramidal donor set with the phosphazene ring and pendant pyridyloxy nitrogens binding to the metal ions. The coordinated L2 ligand in the complex, [CoL2Cl2], slowly hydrolyses in acetonitrile with the loss of a pyridine pendant arm to form a dimetallic species, which has been characterized by crystallography as [{CoL2aCl}]2.4MeCN (L2a=[N3P3(biph)(OPy)3(O)]-, biph=2,2'-dioxybiphenyl, OPy=2-oxopyridine). The ligands, L3, L4, L5, and L6, bind to the metal halides via gem-substituted pyridyloxy nitrogens only. The resulting rigid eight-membered chelate rings all have distorted boat conformations, which force distorted-tetrahedral N2Cl2 coordination environments onto the metal ions. The spectroscopic (ESR and electronic) and magnetic properties of the complexes are reported.     

Synthesis and coordination chemistry of two N2-donor chelating di(indazolyl)methane ligands: structural characterization and comparison of their metal chelation aptitudes

The N(2)-donor bidentate ligands di(1H-indazol-1-yl)methane (L(1)) and di(2H-indazol-2-yl)methane (L(2)) (L in general) have been synthesized, and their coordination behavior toward Zn(II), Cd(II), and Hg(II) salts has been studied. Reaction of L(1) and L(2) with ZnX(2) (X = Cl, Br, or I) yields [ZnX(2)L] species (1-6), that, in the solid state, show a tetrahedral structure with dihapto ligand coordination via the pyrazolyl arms. The reaction of L(1) and L(2) with Zn(NO(3))(2)·6H(2)O is strongly dependent on the reaction conditions and on the ligand employed. Reaction of L(1) with equimolar quantities of Zn(NO(3))(2)·6H(2)O yields the neutral six-coordinate species [Zn(NO(3))(2)(L(1))], 7. On the other hand the use of L(1) excess gives the 2:1 adduct [Zn(NO(3))(2)(L(1))(2)], 8 where both nitrates act as a unidentate coordinating ligand. Analogous stoichiometry is found in the compound obtained from the reaction of L(2) with Zn(NO(3))(2)·6H(2)O which gives the ionic [Zn(NO(3))(L(2))(2)](NO(3)), 10. Complete displacement of both nitrates from the zinc coordination sphere is observed when the reaction between L(1) excess and the zinc salt was carried out in hydrothermal conditions. The metal ion type is also determining structure and stoichiometry: the reaction of L(2) with CdCl(2) gave the 2:1 adduct [CdCl(2)(L(2))(2)] 11 where both chlorides complete the coordination sphere of the six-coordinate cadmium center; on the other hand from the reaction of L(1) with CdBr(2) the polynuclear [CdBr(2)(L(1))](n) 12 is obtained, the Br(-) anion acting as bridging ligands in a six-coordinate cadmium coordination environment. The reaction of L(1) and L(2) with HgX(2) (X = Cl, I, SCN) is also dependent on the reaction conditions and the nature of X, two different types of adducts being formed [HgX(L)] (14: L = L(1), 16, 17: L = L(1) or L(2), X = I, 19: L = L(2), X = SCN) and [HgX(L)(2)] (15: L = L(2), X = Cl, 18: L = L(1), X = SCN). The X-ray diffraction analyses of compounds 1, 2, 4, 5, 7, 8, 10-12, 14, 15, and 19 are also reported. The variations of the coordination geometry parameters in the complexes are compared and discussed.     

Metallochain cluster complexes and metallomacrocyclic triangles based on coordination bonds between palladium or platinum and diphosphinoacetylene ligands

To explore the potential of the coordination chemistry of Pd and Pt halides with phosphinoacetylene ligands for the generation of novel, highly metallated organometallic coordination polymers, investigations on model compounds [MX2(PPh2 C identical to CPh)2] that exhibit trans-configured Pd centers and cis-configured Pt centers have been performed. The molecular structure of the trans-Pd complexes 2 (M = Pd, X = Br) and 5 (M = Pd, X = I) appeared suitable for the generation of linear materials, whereas the cis-Pt complex 6 (M = Pt, X = I) suggested the prospective formation of ring systems. The presence of acetylene moieties allowed for further increase of metal concentration by cluster formation with [Co2(CO)8]. Two novel bimetal cluster complexes 7 and 8 were obtained from 5 and 6, respectively, and these exhibit a bridging iodine ligand as an interesting structural motif leading to heterocyclic systems with M-I-Co-C-P skeletons (M = Pd or Pt). A similar approach with [Fe2(CO)9] led to the formation of several products, including an unusual Pd-Fe cluster-containing compound 10. The extension of the coordination strategy to rigid bis(phosphinoacetylene) ligands gave rise to strained ring systems. Surprisingly, for the cis-configured PtCl2 center, a rarely observed triangular structure 12 was obtained exclusively. The corresponding PtI2 analog, 13a rearranged over time to form a "ring-fused" system 13b with an extended BINAP-like ligand.     

Thiol- and thioether-based bifunctional chelates for the {M(CO)3}+ core (M = Tc, Re)

By analogy to the recently described single amino acid chelate (SAAC) technology for complexation of the {M(CO)3}+ core (M = Tc, Re), a series of tridentate ligands containing thiolate and thioether groups, as well as amino and pyridyl nitrogen donors, have been prepared: (NC5H4CH2)2NCH2CH2SEt (L1); (NC5H4CH2)2NCH2CH2SH (L2); NC5H4CH2N(CH2CH2SH)2 (L3); (NC5H4CH2)N(CH2CH2SH)(CH2CO2R) [R = H (L4); R = -C2H5 (L5). The {Re(CO)3}+ core complexes of L1-L5 were prepared by the reaction of [Re(CO)3(H2O)3]Br or [NEt4]2[Re(CO)3Br3] with the appropriate ligand in methanol and characterized by infrared spectroscopy, 1H and 13C NMR spectroscopy, mass spectrometry, and in the case of [Re(CO)3(L2)] (Re-2) and [Re(CO)3(L1)Re(CO)3Br2] (Re-1a) by X-ray crystallography. The structure of Re-2 consists of discrete neutral monomers with a fac-Re(CO)3 coordination unit and the remaining coordination sites occupied by the amine, pyridyl, and thiolate donors of L2, leaving a pendant pyridyl arm. In contrast, the structure of Re-1a consists of discrete binuclear units, constructed from a {Re(CO)3(L1)}+ subunit linked to a {Re(CO)3Br2}- group through the sulfur donor of the pendant thioether arm. The series of complexes establishes that thiolate donors are effective ligands for the {M(CO)3}+ core and that a qualitative ordering of the coordination preferences of the core may be proposed: pyridyl nitrogen approximately thiolate > carboxylate > thioether sulfur > thiophene sulfur. The ligands L1 and L2 react cleanly with [99mTc(CO)3(H2O)3]+ in H2O/DMSO to give [99mTc(CO)3(L1)]+ (99m)Tc-1) and [99mTc(CO)3(L2)] (99mTc-2), respectively, in ca. 90% yield after HPLC purification. The Tc analogues 99mTc-1 and 99mTc-2 were subjected to ligand challenges by incubating each in the presence of 1000-fold excesses of both cysteine and histidine. The radiochromatograms showed greater than 95% recovery of the complexes.     

Synthesis and structures of some bimetallic (Li/Ca, Li/Zn, Li/Li) diamides derived from 1,2-bis(neopentylamino)benzene and of Li2[{N(SiMe2NPr(i)2)}2C6H4-1,2](thf)3

The following crystalline, or microcrystalline (4), metal diamides have been prepared under mild conditions from the N,N'-disubstituted 1,2-diaminobenzene [{N(R)H}2C6H4-1,2] (H(2): R = CH2But; H2L': R = SiMe2NPri2): [Li(thf)(mu-L)(mu-I)Ca(thf)] (1), [Li(thf)4][{Zn(mu-L)}3(mu3-Cl)] (2), [Li(thf)4][Zn(L)2] (3), [{Li(OEt2)(mu-L)Zn}2(mu-L)] (4), [Li(OEt2)(mu-L)Zn(mu-L)Zn(LH)] (5) and [Li(thf)(mu-L')Li(thf)2] (6). Compounds 1-5 were obtained from [Li2(L)] and CaI2 (1) or ZnCl2 (2-5) while 6 was derived from H2(L') and LiBun. Compound 5 was isolated as a very minor by-product from the synthesis of 4, and is assumed to have been formed therefrom by adventitious hydrolysis. The green salt 3 was paramagnetic with the negative charge uniformly delocalised on the two ligands. The other compounds were colourless and diamagnetic. The X-ray structures of each, except 4, are reported and discussed.     

Synthesis, crystal structure, aqueous speciation, and kinetics of substitution reactions in a water-soluble Mo3S4 cluster bearing hydroxymethyl diphosphine ligands

The [Mo3S4Cl3(dhmpe)3]Cl ([1]Cl) cluster has been prepared from [Mo3S7Cl6]2- and the water-soluble 1,2-bis(bis(hydroxymethyl)-phosphino)ethane (dhmpe, L) ligand. The crystal structure has been determined by X-ray diffraction methods and shows the incomplete cuboidal structure typical of the M3Q4 clusters (M=Mo, W; Q=S, Se), with a capping sulfide ligand to the three metal centers and the other three sulfides acting as bridges between two Mo atoms. The octahedral coordination around each metal center is completed with a chlorine and two phosphorus atoms of one L ligand. The chemistry of aqueous solutions of [1]Cl is dominated by the formation of the [Mo3S4L(L-H)2(H2O)]2+ complex ([2]2+), where the three chlorides have been replaced by one water molecule and two alkoxo groups of two different dhmpe ligands, thus leading to a solution structure where the three metal centers are not equivalent. A detailed study based on stopped-flow, 31P{1H} NMR, and electrospray ionization mass spectrometry techniques has been carried out to understand the behavior of [2]2+ in aqueous solution. In this way, it has been established that the addition of an excess of X- (Cl-, SCN-) leads to [Mo3S4X3(dhmpe)3]+ complexes in three resolved kinetic steps that correspond to the sequential coordination of X- at the three metal centers. However, whereas the first two steps involve the opening of the chelate rings formed with the alkoxo groups of the dhmpe ligands, the third one corresponds to the substitution of the coordinated water molecule. These results demonstrate that the asymmetry introduced by the closure of chelate rings at only two of the three Mo centers makes the kinetics of the reaction deviate significantly from the statistical behavior typically associated with M3Q4 clusters. The results obtained for the reaction of [2]2+ with acid and base are also described, and they complete the picture of the aqueous speciation of this cluster.     

A closed molecular cube and an open book: two different products from assembly of the same metal salt and bridging ligand

Reaction of the bis-bidentate bridging ligand L1 with Co(ClO4)2 or Zn(BF4)2 affords a mixture of complexes [M8(L1)12]X16 and [M6(L1)9]X12 having the same metal : ligand ratio: the former is a molecular cube with a metal ion at each vertex and a bridging ligand spanning each edge, whereas the latter has a metal framework like that of an 'open book' containing cross-linked double helical metal-ligand subunits.     

Synthesis and spectroscopic studies of mixed-ligand and polymeric dinuclear transition metal complexes with bis-acylhydrazone tetradentate ligands and 1,10-phenanthroline

Two types of dinuclear copper(II) and nickel(II) complexes with two tetradentate N2O2 donor ligands 1,4-bis(1-anthranoylhydrazonoethyl)benzene (L1), 1,4-bis(1-salicyloylhydrazonoethyl)benzene (L2) and N,N'-bidentate heterocyclic base [1,10-phenonthroline (phen)] have been synthesized and characterized by elemental analysis, infrared spectra, UV-vis electronic absorption spectra and magnetic susceptibility measurements. The reaction of metal(II) acetates with the solution containing ligand and 1,10-phenonthroline in methanol gives mixed-ligand dinuclear metal(II) complexes with general formula [M2L(phen)2]Cl2 (L=L1 or L2), whereas, the ligands react with metal(II) acetates to form polymeric dinuclear complexes with general formula [(M2L2)n] (L=L1 or L2). In the complexes, the ligands act as dianionic tetradentate and coordination takes place in the enol tautomeric form with the enolic oxygen and azomethine nitrogen atoms while the phenolic hydroxyl and amino groups of aroylhydrazone moiety do not participate in coordination. The effect of varying pH and solvent on the absorption behavior of both ligands and complexes has been investigated.     

Syntheses and structures of Ag(I)-containing coordination polymers and Co(II)-containing supramolecular complex based on novel fulvene ligands

Three new rigid conjugated fulvene ligands L1-L3 were synthesized. L1 and L3 have been prepared by an aroylation reaction of cyclohexyl-substituted cyclopentadienyl anions. L2 was prepared by the reaction of L1 with PhNHNH2 in hot enthanol. Six new coordination polymers, namely [Ag(C25H20N2O2)(ClO4)] x 3.5C6H6 (1), [Ag2(mu-C31H24N4)(eta2-C6H6)(H2O)](ClO4)2 x (C6H6) x (H2O)0.5 (3), [Ag(C31H24N4)]SbF6 x solvate (4), [Ag(C31H24N4)](SbF6)2 x 2C6H6 x CH2Cl2 (5), [Ag(C25H20N2O2)2]SbF6 (6), and [Ag(C25H20N2O2)2]SbF6 (7), and one seven-membered cobaltacycle-containing complex, namely Co(C25H20N2O2)2(C2H5OH)2 (2), were obtained through self-assembly based on these three new fulvene lignads. L2-L3 and compounds 1-7 have been fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The results indicate that the coordination chemistry of new fulvene ligands is versatile. They can bind metal ions not only through the terminal N-donors and fulvene carbon atoms into organometallic coordination polymers but also through the two chelating carbonyl groups into unusual seven-membered metallo-ring supramolecular complexes. In the solid state, ligands L1-L3 are luminescent. A blue-shift in the emission was observed between the free ligand L1 and the one incorporated into Co(II)-containing complex 2, and a red-shift in the emission was observed between the free ligand L3 and the one incorporated into Ag(I)-containing polymeric compounds 6 and 7.