Ligand effects in the syntheses and structures of novel heteroleptic and homoleptic bismuth(III) formamidinate complexes

Metathesis reactions of the alkali metal formamidinates M(RNC(H)NR), M = Li or K; R = C(6)H(3)-2,6-Pr(i)(2) (L(1)), C(6)H(3)-2,6-Et(2) (L(2)); C(6)H(2)-2,4,6-Me(3) (L(3)), C(6)H(3)-2,6-Me(2) (L(4)) or C(6)H(4)-2-Ph (L(5)), with BiX(3) (X = Cl or Br) gave a range of bismuth(iii) formamidinate complexes [Bi(L)Br(micro-Br)(thf)](2) (L = L(1), L(4)), [{Bi(L(1))Cl(2)(thf)}(2)Bi(L(1))Cl(2)], [Bi(L)(2)X] (L = L(2), L(5), X = Br; L = L(1), X = Cl), and [Bi(L)(3)] (L = L(2), L(3)). An analogous organometallic complex Bi(L(1))(2)Bu(n) was also isolated as a side product in one instance. Structural characterisation of the di-halide complexes show symmetrical dimers for X = Br, with two bromide bridges, and a coordinated thf molecule on each Bi atom, whereas for X = Cl a thf deficient species was crystallised, and has a weakly associated trinuclear array with two coordinated thf molecules per three Bi atoms. Complexes of the form Bi(L)(2)X (X = Br, Cl, Bu(n)) and Bi(L)(3) all have monomeric structures but the Bi(L)(3) species show marked asymmetry of the formamidinate binding, suggesting that they have reached coordination saturation.     

Ru(2) Bi(14) Br(4) ](AlCl(4) )(4) by Mobilization and Reorganization of Complex Clusters in Ionic Liquids

Two polymorphs of the new cluster compound [Ru(2) Bi(14) Br(4) ](AlCl(4) )(4) have been synthesized from Bi(24) Ru(3) Br(20) in the Lewis acidic ionic liquid [BMIM]Cl/AlCl(3) ([BMIM](+) : 1-n-butyl-3-methylimidazolium) at 140?°C. A large fragment of the precursor's structure, namely the [(Bi(8) )Ru(Bi(4) Br(4) )Ru(Bi(5) )](5+) cluster, dissolved as a whole and transformed into a closely related symmetrical [(Bi(5) )Ru(Bi(4) Br(4) )Ru(Bi(5) )](4+) cluster through structural conversion of a coordinating Bi(8) (2+) to a Bi(5) (+) polycation, while the remainder was left intact. Both modifications have monoclinic unit cells that comprise two formula units (α form: P2(1) /n, a=982.8(2), b=1793.2(4), c=1472.0(3)?pm, β=109.05(3)°; β form: P2(1) /n, a=1163.8(2), b=1442.7(3), c=1500.7(3), β=97.73(3)°). The [Ru(2) Bi(14) Br(4) ](4+) cluster can be regarded as a binuclear inorganic complex of two ruthenium(I) cations that are coordinated by terminal Bi(5) (+) square pyramids and a central Bi(4) Br(4) ring. The presence of a covalent Ru?Ru bond was established by molecular quantum chemical calculations utilizing real-space bonding indicator ELI-D. Structural similarity of the new and parent cluster suggests a structural reorganization or an exchange of the bismuth polycations as mechanisms of cluster formation. In this top-down approach a complex-structured unit formed at high temperature was made available for low-temperature use.     

Density functional study of 8- and 11-vertex polyhedral borane structures: comparison with bare germanium clusters

Density functional theory (DFT) at the hybrid B3LYP level has been applied to the polyhedral boranes B(n)H(n)(z) (n = 8 and 11, z = -2, -4, and -6) for comparison with isoelectronic germanium clusters Ge(n)(z). The energy differences between the global minima and other higher energy borane structures are much larger relative to the case of the corresponding bare germanium clusters. Furthermore, for both B(8)H(8)(2-) and B(11)H(11)(2-), the lowest energy computed structures are the corresponding experimentally observed most spherical deltahedra predicted by the Wade-Mingos rules, namely the D(2)(d) bisdisphenoid and the C(2)(v) edge-coalesced icosahedron, respectively. Only in the case of B(8)H(8)(2-) is there a second structure close (+2.6 kcal/mol) to the D(2)(d) bisdisphenoid global minimum, namely the C(2)(v) bicapped trigonal prism corresponding to the "square" intermediate in a single diamond-square-diamond process that can lead to the experimentally observed room temperature fluxionality of B(8)H(8)(2-). Stable borane structures with 3-fold symmetry (e.g., D(3)(h), C(3)(v), etc.) are not found for boranes with 8- and 11-vertices, in contrast to the corresponding germanium clusters where stable structures derived from the D(3)(d) bicapped octahedron and D(3)(h) pentacapped trigonal prism are found for the 8- and 11-vertex systems, respectively. The lowest energy structures found for the electron-rich boranes B(8)H(8)(4-) and B(11)H(11)(4-) are nido polyhedra derived from a closo deltahedron by removal of a relatively high degree vertex, as predicted by the Wade-Mingos rules. They relate to isoelectronic species found experimentally, e.g., B(8)H(12) and R(4)C(4)B(4)H(4) for B(8)H(8)(4-) and C(2)B(9)H(11)(2-) for B(11)H(11)(4-). Three structures were found for B(11)H(11)(6-) with arachno type geometry having two open faces in accord with the Wade-Mingos rules.     

Cobalt-centered ten-vertex germanium clusters: the pentagonal prism as an alternative to polyhedra predicted by the Wade-Mingos rules

One of the most exciting recent (2009) discoveries in metal cluster chemistry is the pentagonal prismatic Co@Ge(10)(3-) ion, found in [K(2,2,2-crypt)](4)[Co@Ge(10)][Co(1,5-C(8)H(12))(2)]·toluene and characterized structurally by X-ray diffraction. The complete absence of triangular faces in the pentagonal prismatic structure of Co@Ge(10)(3-) contradicts expectations from the well-established Wade-Mingos rules, which predict polyhedral structures having mainly or entirely triangular faces. A theoretical study on Co@Ge(10)(z) systems (z = -5 to +1) predicts a singlet D(5h) pentagonal prismatic global minimum for the trianion Co@Ge(10)(3-) in accord with this experimental result. Redox reactions on this pentagonal prismatic Co@Ge(10)(3-) trianion generate low-energy pentagonal prismatic structures for Co@Ge(10)(z) where z = 0, -1, -2, -4, and -5 having quartet, triplet, doublet, doublet, and triplet spin states, respectively. Similar theoretical methods predict a singlet C(3v) polyhedral structure for the monoanion Co@Ge(10)(-), similar to previous theoretical predictions on the isoelectronic neutral Ni@Ge(10) and the structure realized experimentally in the isoelectronic Ni@In(10)(10-) found in the K(10)In(10)Ni intermetallic. Redox reactions on this C(3v) polyhedral Co@Ge(10)(-) monoanion generate low energy C(3v) polyhedral structures for Co@Ge(10)(z) where z = 0, -2, -3, and -4 having doublet, doublet, triplet, and quartet spin states, respectively.     

Carbonylchromium derivatives of bismuth: new syntheses and relevance to cbond;o activation

We have discovered a series of novel pentacarbonylchromium derivatives of bismuth from the reactions of NaBiO(3) with [Cr(CO)(6)] in KOH/MeOH solutions. When the reaction was carried out at room temperature, the highly charged [Bi[Cr(CO)(5)](4)](3-) (1) was obtained, whose structure was shown by X-ray analysis to possess a central bismuth atom tetrahedrally coordinated to four [Cr(CO)(5)] groups. As the reaction was heated at 80 degrees C, the methyl-substituted complex [MeBi[Cr(CO)(5)](3)](2-)(2) was obtained, presumably via the CbondO activation of MeOH. Further reactions of 1 with CH(2)Cl(2) or CHtbondCCH(2)Br form the halo-substituted complexes [XBi[Cr(CO)(5)](3)](2-)(X=Cl, 3; Br, 4), respectively. On the other hand, the reactions of 1 with RI (R=Me, Et) led to the formation of the alkyl-substituted complexes [RBi[Cr(CO)(5)](3)](2-)(R=Me, 2; Et). The formation of complexes 1-4 is discussed, presumably via the intermediate bismuthinidene [Bi[Cr(CO)(5)](3)](-) or the trianion [Bi[Cr(CO)(5)](3)](3-).     

Density functional theory study of eight-atom germanium clusters: effect of electron count on cluster geometry

Density functional theory (DFT) at the hybrid B3LYP level has been applied to the germanium clusters Ge8z(z=-6, -4, -2, 0, +2, +4) using nine initial geometries. For Ge8(2-) the D2d bisdisphenoid structure predicted by the Wade-Mingos rules is not computed to be the global minimum but instead lies 3.9 kcal mol-1 above the Td tetracapped tetrahedron global minimum predicted to exhibit spherical aromaticity. The hyperelectronic clusters Ge(8)4- and Ge8(6-) have nido B8H12 and square antiprism structures, respectively, as global minima in accord with the Wade-Mingos rules and experimental data on E(8)2+(E=Sb, Bi) cations. Hypoelectronic eight-vertex clusters isoelectronic and isolobal with Ge8, Ge8(2+) and Ge(8)4+ are not known experimentally. Their computed structures include smaller polyhedra having one or more capped triangular faces as well as more open non-polyhedral structures.     

铋(Ⅲ)配合物Bi(1,10-phen)[S2CN(CH3)2]2(NO3),

Three bismuth（Ⅲ） complexes Bi（1,10-phen）[S2CN（CH3）2]2（NO3） （1）, {Bi（S2COCH3）[S2CNC6Hs（CH3）]2}2 （2） and [Bi（S2CNBu2）2（CH3OH）（NO3）]∞ （3） were synthesized and characterized by elemental analysis and IR spectra. Their crystal structures were determined by X-ray single crystal diffraction analysis. Studies show that complex 1 has a monomeric structure with the central bismuth atom eight-coordinated in a capped distorted pentagonal bipyramidal geometry. The complex 2 takes centrosymmetric dimeric structure and the bismuth atoms are seven-coordinated in distorted pentagonal bipyramidal geometry.In complex 3, the bismuth atoms are seven-coordinated in distorted pentagonal bipyramidal geometry by bridging nitrate O atoms and the resulting structure is onedimensional infinite chain polymer.     

Copper halide-bridged ruthenium telluride carbonyl complexes: discovery of the semiconducting cluster chain polymer {[PPh4]2[Te2Ru4(CO)10Cu4Br2Cl2].THF}infinity

A new series of Te-Ru-Cu carbonyl complexes was prepared by the reaction of K(2)TeO(3) with [Ru(3)(CO)(12)] in MeOH followed by treatment with PPh(4)X (X=Br, Cl) and [Cu(MeCN)(4)]BF(4) or CuX (X=Br, Cl) in MeCN. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was first treated with PPh(4)X followed by the addition of [Cu(MeCN)(4)]BF(4), doubly CuX-bridged Te(2)Ru(4)-based octahedral clusters [PPh(4)](2)[Te(2)Ru(4)(CO)(10)Cu(2)X(2)] (X=Br, [PPh(4)](2)[1]; X=Cl, [PPh(4)](2)[2]) were obtained. When the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)X (X=Br, Cl) followed by the addition of CuX (X=Br, Cl), three different types of CuX-bridged Te-Ru carbonyl clusters were obtained. While the addition of PPh(4)Br or PPh(4)Cl followed by CuBr produced the doubly CuBr-bridged cluster 1, the addition of PPh(4)Cl followed by CuCl led to the formation of the Cu(4)Cl(2)-bridged bis-TeRu(5)-based octahedral cluster compound [PPh(4)](2)[{TeRu(5)(CO)(14)}(2)Cu(4)Cl(2)] ([PPh(4)](2)[3]). On the other hand, when the reaction mixture of K(2)TeO(3) and [Ru(3)(CO)(12)] was treated with PPh(4)Br followed by the addition of CuCl, the Cu(Br)CuCl-bridged Te(2)Ru(4)-based octahedral cluster chain polymer {[PPh(4)](2)(Te(2)Ru(4)(CO)(10)Cu(4)Br(2)Cl(2)).THF}(infinity) ({[PPh(4)](2)[4].THF}(infinity)) was produced. The chain polymer {[PPh(4)](2)[4].THF}(infinity) is the first ternary Te-Ru-Cu cluster and shows semiconducting behavior with a small energy gap of about 0.37 eV. It can be rationalized as resulting from aggregation of doubly CuX-bridged clusters 1 and 2 with two equivalents of CuCl or CuBr, respectively. The nature of clusters 1-4 and the formation and semiconducting properties of the polymer of 4 were further examined by molecular orbital calculations at the B3LYP level of density functional theory.     

Influence of ligand polarizability on the reversible binding of O2 by trans-[Rh(X)(XNC)(PPh3)2] (X = Cl, Br, SC6F5, C2Ph; XNC = xylyl isocyanide). Structures and a kinetic study

The complexes trans-[Rh(X)(XNC)(PPh 3) 2] (X = Cl, 1; Br, 2; SC 6F 5, 3; C 2Ph, 4; XNC = xylyl isocyanide) combine reversibly with molecular oxygen to give [Rh(X)(O 2)(XNC)(PPh 3) 2] of which [Rh(SC 6F 5)(O 2)(XNC)(PPh 3) 2] ( 7) and [Rh(C 2Ph)(O 2)(XNC)(PPh 3) 2] ( 8) are sufficiently stable to be isolated in crystalline form. Complexes 2, 3, 4, and 7 have been structurally characterized. Kinetic data for the dissociation of O 2 from the dioxygen adducts of 1- 4 were obtained using (31)P NMR to monitor changes in the concentration of [Rh(X)(O 2)(XNC)(PPh 3) 2] (X = Cl, Br, SC 6F 5, C 2Ph) resulting from the bubbling of argon through the respective warmed solutions (solvent chlorobenzene). From data recorded at temperatures in the range 30-70 degrees C, activation parameters were obtained as follows: Delta H (++) (kJ mol (-1)): 31.7 +/- 1.6 (X = Cl), 52.1 +/- 4.3 (X = Br), 66.0 +/- 5.8 (X = SC 6F 5), 101.3 +/- 1.8 (X = C 2Ph); Delta S (++) (J K (-1) mol (-1)): -170.3 +/- 5.0 (X = Cl), -120 +/- 13.6 (X = Br), -89 +/- 18.2 (X = SC 6F 5), -6.4 +/- 5.4 (X = C 2Ph). The values of Delta H (++) and Delta S (++) are closely correlated (R (2) = 0.9997), consistent with a common dissociation pathway along which the rate-determining step occurs at a different position for each X. Relative magnitudes of Delta H (++) are interpreted in terms of differing polarizabilities of ligands X.     

Density functional theory study of twelve-atom germanium clusters: conflict between the Wade-Mingos rules and optimum vertex degrees

Density functional theory (DFT) at the hybrid B3LYP level has been applied to Ge(12)(z) bare germanium clusters (z = -6, -4, -2, 0, +2, +4, +6) starting from 11 initial configurations. The Wade-Mingos rules are seen to have limited value in rationalizing the results since they frequently require vertex degrees higher than the optimum vertex degree of 4 for germanium. Thus the expected I(h) regular icosahedron is no longer the global minimum for Ge(12)(2-) although it remains a low energy structure for Ge(12)(2-) lying only 5.6 kcal mol(-1) above a bicapped arachno structure conforming to the Wade-Mingos rules. The three lowest energy structures for Ge(12)(4-) within 11 kcal mol(-1) are a prolate (elongated) polyhedron with six quadrilateral faces and eight triangular faces, the dual of the bisdisphenoid with four trapezoidal and four pentagonal faces, and a polyhedron with two quadrilateral and 16 triangular faces related but not identical to the polyhedron found in the known tetracarbon carboranes R(4)C(4)B(8)H(8). The lowest energy structures for the neutral Ge(12) are seen to be distorted versions of the icosahedron and the bicapped 10-vertex arachno lowest energy structures for Ge(12)(2-). The low energy structures for the even more hypoelectronic Ge(12)(2+) and Ge(12)(4+) are even more unusual including a hexacapped octahedron, a tetracapped square antiprism, and a double cube for Ge(12)(2+) and a C(2v) structure with a central unique degree 6 vertex for Ge(12)(4+).     

Electronic structures of ruthenium and osmium complexes of 9,10-phenanthrenequinone

The reaction of 9,10-phenanthrenequinone (PQ) with [M(II)(H)(CO)(X)(PPh(3))(3)] in boiling toluene leads to the homolytic cleavage of the M(II)-H bond, affording the paramagnetic trans-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2·toluene, and 4·CH(2)Cl(2), EPR spectra, and density functional theory (DFT) calculations have substantiated that 1-4 are 9,10-phenanthrenesemiquinone radical (PQ(?-)) complexes of ruthenium(II) and osmium(II) and are defined as trans-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (1), cis-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (2), trans-[Os(II)(PQ(?-))(PPh(3))(2)(CO) Br] (3), and cis-[Os(II)(PQ(?-))(PPh(3))(2)(CO)Br] (4). Two comparatively longer C-O [average lengths: 1, 1.291(3) ?; 2·toluene, 1.281(5) ?; 4·CH(2)Cl(2), 1.300(8) ?] and shorter C-C lengths [1, 1.418(5) ?; 2·toluene, 1.439(6) ?; 4·CH(2)Cl(2), 1.434(9) ?] of the OO chelates are consistent with the presence of a reduced PQ(?-) ligand in 1-4. A minor contribution of the alternate resonance form, trans- or cis-[M(I)(PQ)(PPh(3))(2)(CO)X], of 1-4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe(3))(2)(CO)Cl] (5), cis-[Ru(PQ)(PMe(3))(2)(CO)Cl] (6), and cis-[Os(PQ)(PMe(3))(2)(CO)Br] (7). However, no thermodynamic equilibria between [M(II)(PQ(?-))(PPh(3))(2)(CO)X] and [M(I)(PQ)(PPh(3))(2)(CO)X] tautomers have been detected. 1-4 undergo one-electron oxidation at -0.06, -0.05, 0.03, and -0.03 V versus a ferrocenium/ferrocene, Fc(+)/Fc, couple because of the formation of PQ complexes as trans-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (1(+)), cis-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (2(+)), trans-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (3(+)), and cis-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (4(+)). The trans isomers 1 and 3 also undergo one-electron reduction at -1.11 and -0.96 V, forming PQ(2-) complexes trans-[Ru(II)(PQ(2-))(PPh(3))(2)(CO)Cl](-) (1(-)) and trans-[Os(II)(PQ(2-))(PPh(3))(2)(CO)Br](-) (3(-)). Oxidation of 1 by I(2) affords diamagnetic 1(+)I(3)(-) in low yields. Bond parameters of 1(+)I(3)(-) [C-O, 1.256(3) and 1.258(3) ?; C-C, 1.482(3) ?] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV-vis/near-IR absorption features of 1-4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5(+), and 5(-).     

Bending, twisting, and breaking CuCN chains to produce framework materials: the reactions of CuCN with alkali-metal halides

The reactions of the low-temperature polymorph of copper(I) cyanide (LT-CuCN) with concentrated aqueous alkali-metal halide solutions have been investigated. At room temperature, KX (X = Br and I) and CsX (X = Cl, Br, and I) produce the addition products K[Cu(2)(CN)(2)Br].H(2)O (I), K(3)[Cu(6)(CN)(6)I(3)].2H(2)O (II), Cs[Cu(3)(CN)(3)Cl] (III), Cs[Cu(3)(CN)(3)Br] (IV), and Cs(2)[Cu(4)(CN)(4)I(2)].H(2)O (V), with 3-D frameworks in which the -(CuCN)- chains present in CuCN persist. No reaction occurs, however, with NaX (X = Cl, Br, I) or KCl. The addition compounds, I-V, reconvert to CuCN when washed. Both low- and high-temperature polymorphs of CuCN (LT- and HT-CuCN) are produced, except in the case of Cs[Cu(3)(CN)(3)Cl] (III), which converts only to LT-CuCN. Heating similar AX-CuCN reaction mixtures under hydrothermal conditions at 453 K for 1 day produces single crystals of I-V suitable for structure determination. Under these more forcing conditions, reactions also occur with NaX (X = Cl, Br, I) and KCl. NaBr and KCl cause some conversion of LT-CuCN into HT-CuCN, while NaCl and NaI, respectively, react to form the mixed-valence Cu(I)/Cu(II) compounds [Cu(II)(OH(2))(4)][Cu(I)(4)(CN)(6)], a known phase, and [Cu(II)(OH(2))(4)][Cu(I)(4)(CN)(4)I(2)] (VI), a 3-D framework, which contains infinite -(CuCN)- chains. After 3 days of heating under hydrothermal conditions, the reaction between KI and CuCN produces [Cu(II)(OH(2))(4)][Cu(I)(2)(CN)I(2)](2) (VII), in which the CuCN chains are broken into single Cu-CN-Cu units, which in turn are linked into chains via iodine atoms and then into layers via long Cu-C and Cu-Cu interactions.     

Density functional theory study of 11-atom germanium clusters: effect of electron count on cluster geometry

Density functional theory (DFT) at the hybrid B3LYP level has been applied to the germanium clusters Ge(11)(z) (z = -6, -4, -2, 0, +2, +4, +6) starting from eight different initial configurations. The global minimum within the Ge(11)(2-) set is an elongated pentacapped trigonal prism distorted from D(3)(h) to C(2v) symmetry. However, the much more spherical edge-coalesced icosahedron, also of C(2v) symmetry, expected by the Wade-Mingos rules for a 2n + 2 skeletal electron system and found experimentally in B(11)H(11)(2-) and isoelectronic carboranes, is of only slightly higher energy (+5.2 kcal/mol). Even more elongated D(3)(h) pentacapped trigonal prisms are the global minima for the electron-rich structures Ge(11)(4-) and Ge(11)(6-). For Ge(11)(4-) the C(5v) 5-capped pentagonal antiprism analogous to the dicarbollide ligand C(2)B(9)H(11)(2-) is of significantly higher energy (approximately 28 kcal/mol) than the D(3h) global minimum. The C(2v) edge-coalesced icosahedron is also the global minimum for the electron-poor Ge(11) similar to its occurrence in experimentally known 11-vertex "isocloso" metallaboranes of the type (eta(6)-arene)RuB(10)H(10). The lowest energy polyhedral structures computed for the more hypoelectronic Ge(11)(4+) and Ge(11)(6+) clusters are very similar to those found experimentally for the isoelectronic ions E(11)(7-) (E = Ga, In, Tl) and Tl(9)Au(2)(9-) in intermetallics in the case of Ge(11)(4+) and Ge(11)(6+), respectively. These DFT studies predict an interesting D(5h) centered pentagonal prismatic structure for Ge(11)(2+) and isoelectronic metal clusters.     

Change of electrical conductivities between hydrated and dehydrated samples of honeycomb sheet structures with mixed oxidation state paddlewheel dirhodium complexes and halide ions

A series of mixed oxidation state compounds, [{Rh(2)(acam)(4)}(3)(μ(3)-X)(2)]·nH(2)O (Hacam = acetamide; X = Cl, n = 4 (1·4H(2)O); X = Br, n = 10 (2·10H(2)O); X = I, n = 10 (3·10H(2)O)) and [{Rh(2)(pram)(4)}(3)(μ(3)-X)(2)]·6H(2)O (Hpram = propionamide; X = Cl (4·6H(2)O), Br (5·6H(2)O), I (6·6H(2)O)) were synthesized and their X-ray structures were determined. In the crystal structure of all of these complexes, dirhodium complexes and halide ions construct 2-D honeycomb sheet arrangements in which the walls consist of Rh(2) units and halide ions lie at the corners. Complexes 1·4H(2)O, 4·6H(2)O, 5·6H(2)O and 6·6H(2)O have three independent Rh(2) units, in which there are two Rh(2)(5+) and one Rh(2)(4+). In these structures, the water molecules hydrogen bond to O atoms and from the N atoms of the amidate ligands. The number of hydrogen bonds from water molecules to the Rh(2)(4+) unit is greater than that to the Rh(2)(5+) units. This suggests that there exists pinning of the oxidation states by water molecules. In the structures of 2·10H(2)O and 3·10H(2)O, all of the Rh(2) units are crystallographically equivalent. In these structures, eight of the 10 water molecules form a honeycomb-like network between the {Rh(2)(acam)(4)}(3)X(2) honeycomb sheets. The former four structures show very low electrical conductivities of ca. 10(-8) S cm(-1) (room temperature, pellets) and the latter structures have the higher values of ca. 10(-4) S cm(-1). In the former complexes, improvement of the values to 10(-6) S cm(-1) was observed, caused by loss of pinning water.     

Iminopyridine complexes of manganese, rhenium, and molybdenum derived from amino ester methylserine and peptides Gly-Gly, Gly-Val, and Gly-Gly-Gly: self-assembly of the peptide chains

Complexes containing pyridine-2-carboxaldehyde (pyca) ligand acting as κ(2)-(N,O) chelates in [MX(CO)(3)(pyca)] (M = Mn, Re; X = Cl, Br), or [MoX(methallyl)(CO)(2)(pyca)] (X = Cl, Br), are good precursors for iminopyridine complexes derived from amino esters and peptides of formula [MX(CO)(3)(py-2-C(H)═NCHX-COOY)] or [MoX(methallyl)(CO)(2)(py-2-C(H)═NCHX-COOY)], via Schiff condensation of the aldehyde function of pyca with the terminal NH(2) group of the amino ester or peptide. X-ray determinations confirm the structures and show that in solid phase the peptide chains assemble through H-bonds adopting different patterns which depend on the geometry of the metal-ligand fragments. The H-bonding patterns have been analyzed in detail and described by using graph set methods. In most cases, Mo complexes show intramolecular arrangement involving the halogen (Cl or Br) and an NH group of the side chain. For the Mn and Re complexes, the peptide side arms form infinite chains, helices, and rings. In many cases, the terminal carboxylic O-H function is engaged in a "terminal" H-bond with a polar molecule of solvent (THF or acetone), instead of forming the usual head-to-head arrangement found in simple carboxylic acids. For the longer tripeptide Gly-Gly-Gly, a discrete, dimeric association is observed, in which the peptide chains show antiparallel arrangement with a complementary disposition of the internal N-H and C═O functions. DOSY experiments in solution show significant changes in the diffusion rates upon addition of OPBu(3), which indicate H-bonding interaction of OPBu(3) with the peptide hydrogens.     

Ruthenium bipyridyl compounds with two terminal alkynyl ligands

Compounds of the form Ru(X2bipy)(PPh3)2(-C triple bond CC6H4NO2-p)2(X2bipy = 4,4'-X(2)-2,2'-bipyridine, X = Me 3a, Br 3b, I 3c) have been synthesised from the mono-alkynyl precursors Ru(X2bipy)(PPh3)2(-C triple bond CC6H4NO2-p)Cl (X = Me 2a, Br 2b, I 2c); the former are the first ruthenium bis-alkynyl compounds that also contain a bipyridyl ligand. Spectroelectrochemical investigation of 3a shows that the metal is readily oxidised to form the ruthenium(III) compound 3a+, and will also undergo a single-electron reduction at each nitro group to form 3a2-. ESR and UV/visible spectra of these redox congeners are presented. We also report the synthesis of [Ru(Me2bipy)(PPh3)2(-C triple bond CBut)(N triple bond N)][PF6] during the attempted synthesis of Ru(Me2bipy)(PPh3)2(-C triple bond CBut)2, and report its X-ray crystal structure and IR spectrum. X-Ray crystal structures of 3b and 3c(as two different solvates) are presented, and the nature of the intermolecular interactions seen therein is discussed. Z-Scan measurements on Ru(Me2bipy)(PPh3)2(-C triple bond CR)Cl (R = C6H4NO2-p2a, But, Ph, C6H4Me) are also reported, and show that Ru(Me2bipy)(PPh3)2(-C triple bond CR)Cl (R = C6H4NO2-p2a, Ph) exhibit moderate third-order non-linearities.     

Photoinduced one-electron reduction of alkyl halides by dirhodium(II,II) tetraformamidinates and a related complex with visible light

Various substituted dirhodium tetraformamidinate complexes, Rh(2)(R-form)(4) (R = p-CF(3), p-Cl, p-OCH(3), m-OCH(3); form = N,N'-diphenylformamidinate), and the new complex Rh(2)(tpgu)(4) (tpgu = 1,2,3-triphenylguanidinate) have been investigated as potential agents for the photoremediation of saturated halogenated aliphatic compounds, RX (R = alkyl group). The synthesis and characterization of the complexes is reported, and the crystal structure of Rh(2)(tpgu)(4) is presented. The lowest energy transition of the complexes is observed at approximately 870 nm and the complexes react with alkyl chlorides and alkyl bromides under low energy irradiation (lambda(irr) > or = 795 nm), but not when kept in the dark. The metal-containing product of the photochemical reaction with RX (X = Cl, Br) is the corresponding mixed-valent Rh(2)(II,III)X (X = Cl, Br) complex, and the crystal structure of Rh(2)(p-OCH(3)-form)(4)Cl generated photochemically from the reaction of the corresponding Rh(2)(II,II) complex in CHCl(3) is presented. In addition, the product resulting from the dimerization of the alkyl fragment, R(2), is also formed during the reaction of each dirhodium complex with RX. A comparison of the dependence of the relative reaction rates on the reduction potentials of the alkyl halides and their C-X bond dissociation energies are consistent with an outer-sphere mechanism. In addition, the relative reaction rates of the metal complexes with CCl(4) decrease with the oxidation potential of the dirhodium compounds. The mechanism of the observed reactivity is discussed and compared to related systems.     

Molecular Structures and Photophysical Properties of Dirhodium Fluorophosphine Complexes

The excited state properties of a series of singly bonded dirhodium compounds, consisting of Rh(0)(2), Rh(0)Rh(II)X(2), and Rh(II)(2)X(4) (X = Cl and Br) cores coordinated by three bis(difluorophosphino)methylamine ligands, have been investigated. The newly synthesized complexes with X = Br have been structurally characterized. The mixed-valence complex Rh(2)[&mgr;-CH(3)N(PF(2))(2)](3)Br(2)[(PF(2))CH(3)N(PF(2))] crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 13.868(7) ?, b = 16.090(5) ?, c = 11.614(5) ?, V = 1591(3) ?(3), and Z = 4; the structure was refined to values of R = 0.052 and R(w) = 0.062. Orange crystals of Rh(2)[&mgr;-CH(3)N(PF(2))(2)](3)Br(4) are monoclinic with a C2/c space group: a = 14.62(6) ?, b = 12.20(2) ?, c = 14.33(1) ?; beta = 106.0(2) degrees; V = 2457(11) ?(3); Z = 4; and R = 0.058 and R(w) = 0.056. Crystalline solids and low-temperature glasses of each member of the chloride and bromide series exhibit long-lived red luminescence. Excitation profiles and temperature dependencies of the emission bandwidths and lifetimes for all complexes are characteristic of luminescence originating from a dsigma excited state. Efficient nonradiative decay is observed upon the thermal population of an excited state proximate to the lowest energy emissive excited state of these complexes. The nonradiative decay rate constant of the upper excited state is 10(2)-10(3) and 10(3)-10(4) greater than that of the emissive excited state for complexes with X = Cl and Br, respectively.     

Syntheses and crystal structures of two new bismuth hydroxyl borates containing [Bi2O2]2+ layers: Bi2O2[B3O5(OH)] and Bi2O2[BO2(OH)

Two new bismuth hydroxyl borates, Bi(2)O(2)[B(3)O(5)(OH)] (I) and Bi(2)O(2)[BO(2)(OH)] (II), have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal and powder X-ray diffraction data, respectively. Compound I crystallizes in the orthorhombic space group Pbca with the lattice constants of a = 6.0268(3) ?, b = 11.3635(6) ?, and c = 19.348(1) ?. Compound II crystallizes in the monoclinic space group Cm with the lattice constants of a = 5.4676(6) ?, b = 14.6643(5) ?, c = 3.9058(1) ?, and β = 135.587(6)°. The borate fundamental building block (FBB) in I is a three-ring unit [B(3)O(6)(OH)](4-), which connects one by one via sharing corners, forming an infinite zigzag chain along the a direction. The borate chains are further linked by hydrogen bonds, showing as a borate layer within the ab plane. The FBB in II is an isolated [BO(2)(OH)](2-) triangle, which links to two neighboring FBBs by strong hydrogen bonds, resulting in a borate chain along the a direction. Both compounds contain [Bi(2)O(2)](2+) layers, and the [Bi(2)O(2)](2+) layers combine with the corresponding borate layers alternatively, forming the whole structures. These two new bismuth borates are the first ones containing [Bi(2)O(2)](2+) layers in borates. The appearance of Bi(2)O(2)[BO(2)(OH)] (II) completes the series of compounds Bi(2)O(2)[BO(2)(OH)], Bi(2)O(2)CO(3), and Bi(2)O(2)[NO(3)(OH)] and the formation of Bi(2)O(2)[B(3)O(5)(OH)] provides another example in demonstrating the polymerization tendency of borate groups.     

Novel bismuth and lead coordination polymers synthesized with pyridine-2,5-dicarboxylates: two single component "white" light emitting phosphors

New two-dimensional (2D) bismuth and three-dimensional (3D) lead based coordination polymers containing pyridine-2,5-dicarboxylate ligands (H(2)pydc) have been synthesized hydrothermally and characterized by single crystal X-ray diffraction. Bi(3)(μ(3)-O)(2)(pydc)(2)(Hpydc)(H(2)O)(2) (1), which crystallizes in the space group P1? (a = 8.7256(5) ?, b = 11.1217(7) ?, c = 14.0933(9) ?, α = 85.239(1)°, β = 98.582(1)°, γ = 71.106(1)°), has a 3D structure that contains Bi(6)O(4) clusters that connect into 2D sheets via linking ligands. The sheets form a 3D supramolecular structure via hydrogen bonding along the z-axis. Pb(pydc)(H(2)O) (2), which crystallizes in the space group P2(1)/c (a = 10.8343(14) ?, b = 11.2099(15) ?, c = 6.6573(9) ?, β = 90.697(2)°), contains 1D chains of corner-sharing distorted face capped trigonal prisms that are connected into a 3D framework via the pydc ligand. In addition, the ligands are hydrogen bonded to each other. Both 1 and 2 are single component "white" light emitting phosphors and are shown to exhibit "white" luminescence that covers a much wider spectral range than is observed for the as received H(2)pydc ligand.