Cyanide-limited complexation of molybdenum(III): synthesis of octahedral [Mo(CN)(6)](3-) and cyano-bridged [Mo(2)(CN)(11)](5-)

Octahedral coordination of molybdenum(III) is achieved by limiting the amount of cyanide available upon complex formation. Reaction of Mo(CF(3)SO(3))(3) with LiCN in DMF affords Li(3)[Mo(CN)(6)] x 6DMF (1), featuring the previously unknown octahedral complex [Mo(CN)(6)](3-). The complex exhibits a room-temperature moment of mu(eff) = 3.80 mu(B), and assignment of its absorption bands leads to the ligand field parameters Delta(o) = 24800 cm(-1) and B = 247 cm(-1). Further restricting the available cyanide in a reaction between Mo(CF(3)SO(3))(3) and (Et(4)N)CN in DMF, followed by recrystallization from DMF/MeOH, yields (Et(4)N)(5)[Mo(2)(CN)(11)] x 2DMF x 2MeOH (2). The dinuclear [Mo(2)(CN)(11)](5-) complex featured therein contains two octahedrally coordinated Mo(III) centers spanned by a bridging cyanide ligand. A fit to the magnetic susceptibility data for 2, gives J = -113 cm(-1) and g = 2.33, representing the strongest antiferromagnetic coupling yet observed through a cyanide bridge. Efforts to incorporate these new complexes in magnetic Prussian blue-type solids are ongoing.     

Assignment of the electronic spectra of [Mo(CN)(8)](4)(-) and [W(CN)(8)](4)(-) by Ab initio calculations

CASPT2 calculations are performed on the dodecahedral and square antiprismatic isomers of the [Mo(CN)(8)](4)(-) and [W(CN)(8)](4)(-) complexes. The high-energy experimental bands above 40000 cm(-)(1) are assigned to MLCT transitions. The experimental observed trend of the extinction coefficients for the molybdenum and tungsten complex is reproduced by our CASSCF oscillator strengths. All bands below 40000 cm(-)(1) can be ascribed to ligand-field transitions, although small contributions from forbidden MLCT transitions cannot be excluded. In order to account for all experimental bands in the electronic spectrum of these octacyanocomplexes, a dynamic equilibrium in solution between the two isomeric forms must be hypothesized. Spin-orbit coupling effects are found to be more important for the square antiprismatic isomers; in particular, large singlet-triplet mixings are calculated for this isomer of [W(CN)(8)](4)(-). Ligand-field and Racah parameters as well as spin-orbit coupling constants are determined on the basis of the calculated transition energies. The obtained values for these parameters support the recently proposed model for exchange interactions in magnetic clusters and networks containing pentavalent octocyanometalates of molybdenum and tungsten.     

Excited-state interactions for [Au(CN)(2)(-)](n) and [Ag(CN)(2)(-)](n) oligomers in solution. Formation of luminescent gold-gold bonded excimers and exciplexes.

Solutions of K[Au(CN)(2)] and K[Ag(CN)(2)] in water and methanol exhibit strong photoluminescence. Aqueous solutions of K[Au(CN)(2)] at ambient temperature exhibit luminescence at concentration levels of > or =10(-2) M, while frozen methanol glasses (77 K) exhibit strong luminescence with concentrations as low as 10(-5) M. The corresponding concentration limits for K[Ag(CN)(2)] solutions are 10(-1) M at ambient temperature and 10(-4) M at 77 K. Systematic variations in concentration, solvent, temperature, and excitation wavelength tune the luminescence energy of both K[Au(CN)(2)] and K[Ag(CN)(2)] solutions by >15 x 10(3) cm(-1) in the UV-visible region. The luminescence bands have been individually assigned to *[Au(CN)(2)(-)](n) and *[Ag(CN)(2)(-)](n) excimers and exciplexes that differ in "n" and geometry. The luminescence of Au(I) compounds is related for the first time to Au-Au bonded excimers and exciplexes similar to those reported earlier for Ag(I) compounds. Fully optimized unrestricted open-shell MP2 calculations for the lowest-energy triplet excited state of staggered [Au(CN)(2)(-)](2) show the formation of a Au-Au sigma single bond (2.66 A) in the triplet excimer, compared to a weaker ground-state aurophilic bond (2.96 A). The corresponding frequency calculations revealed Au-Au Raman-active stretching frequencies at 89.8 and 165.7 cm(-1) associated with the ground state and lowest triplet excited state, respectively. The experimental evidence of the exciplex assignment includes the extremely large Stokes shifts and the structureless feature of the luminescence bands, which suggest very distorted excited states. Extended Hückel (EH) calculations for [M(CN)(2)(-)](n) and *[M(CN)(2)(-)](n) models (M = Au, Ag; n = 2, 3) indicate the formation of M-M bonds in the first excited electronic states. From the average EH values for staggered dimers and trimers, the excited-state Au-Au and Ag-Ag bond energies are predicted to be 104 and 112 kJ/mol, respectively. The corresponding bond energies in the ground state are 32 and 25 kJ/mol, respectively.     

Heterobimetallic coordination polymers incorporating [M(CN)(2)](-) (M = Cu,Ag) and [Ag(2)(CN)(3)](-) units: increasing structural dimensionality via M-M' and M...NC interactions

A series of new heterometallic coordination polymers has been prepared from the reaction of metal-ligand cations and KAg(CN)(2) units. Many of these contain silver-silver (argentophilic) interactions, analogous to gold-gold interactions, which serve to increase supramolecular structural dimensionality. Compared to [Au(CN)(2)](-) analogues, these polymers display new trends specific to [Ag(CN)(2)](-), including the formation of [Ag(2)(CN)(3)](-) and the presence of Ag...N interactions. [Cu(en)(2)][Ag(2)(CN)(3)][Ag(CN)(2)] (1, en = ethylenediamine) forms 1-D chains of alternating [Ag(CN)(2)](-) and [Ag(2)(CN)(3)](-) units via argentophilic interactions of 3.102(1) A. These chains are connected into a 2-D array by strong cyano(N)-Ag interactions of 2.572(3) A. [Cu(dien)Ag(CN)(2)](2)[Ag(2)(CN)(3)][Ag(CN)(2)] (2, dien = diethylenetriamine) forms a 1-D chain of alternating [Cu(dien)](2+) and [Ag(CN)(2)](-) ions with the Cu(II) atoms connected in an apical/equatorial fashion. These chains are cross-linked by [Ag(2)(CN)(3)](-) units via argentophilic interactions of 3.1718(8) A and held weakly in a 3-D array by argentophilic interactions of 3.2889(5) A between the [Ag(CN)(2)](-) in the 2-D array and the remaining free [Ag(CN)(2)](-). [Ni(en)][Ni(CN)(4)].2.5H(2)O (4) was identified as a byproduct in the reaction to prepare the previously reported [Ni(en)(2)Ag(2)(CN)(3)][Ag(CN)(2)] (3). In [Ni(tren)Ag(CN)(2)][Ag(CN)(2)] (5, tren = tris(2-aminoethyl)amine), [Ni(tren)](2+) cations are linked in a cis fashion by [Ag(CN)(2)](-) anions to form a 1-D chain similar to the [Au(CN)(2)](-) analogue. [Cu(en)Cu(CN)(2)Ag(CN)(2)] (6) is a trimetallic polymer consisting of interpenetrating (6,3) nets stabilized by d(10)-d(10) interactions between Cu(I)-Ag(I) (3.1000(4) A). Weak antiferromagnetic coupling has been observed in 2, and a slightly stronger exchange has been observed in 6. The Ni(II) complexes, 4 and 5, display weak antiferromagnetic interactions as indicated by their relatively larger D values compared to that of 3. Magnetic measurements on isostructural [Ni(tren)M(CN)(2)][M(CN)(2)] (M = Ag, Au) show that Ag(I) is a more efficient mediator of magnetic exchange as compared to Au(I). The formation of [Ni(CN)(4)](2)(-), [Ag(2)(CN)(3)](-), and [Cu(CN)(2)](-) are all attributed to secondary reactions of the dissociation products of the labile KAg(CN)(2).     

Preparation and Structures of the 2.2.2-Cryptand(1+) Salts of the [Sb(2)Se(4)](2)(-), [As(2)S(4)](2)(-), [As(10)S(3)](2)(-), and [As(4)Se(6)](2)(-) Anions

2.2.2-Cryptand(1+) salts of the [Sb(2)Se(4)](2)(-), [As(2)S(4)](2)(-), [As(10)S(3)](2)(-), and [As(4)Se(6)](2)(-) anions have been synthesized from the reduction of binary chalcogenide compounds by K in NH(3)(l) in the presence of the alkali-metal-encapsulating ligand 2.2.2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane), followed by recrystallization from CH(3)CN. The [Sb(2)Se(4)](2)(-) anion, which has crystallographically imposed symmetry 2, consists of two discrete edge-sharing SbSe(3) pyramids with terminal Se atoms cis to each other. The Sb-Se(t) bond distance is 2.443(1) ?, whereas the Sb-Se(b) distance is 2.615(1) ? (t = terminal; b = bridge). The Se(b)-Sb-Se(t) angles range from 104.78(4) to 105.18(5) degrees, whereas the Se(b)-Sb-Se(b) angles are 88.09(4) and 88.99(4) degrees. The (77)Se NMR data for this anion in solution are consistent with its X-ray structure (delta 337 and 124 ppm, 1:1 intensity, -30 degrees C, CH(3)CN/CD(3)CN). Similar to this [Sb(2)Se(4)](2)(-) anion, the [As(2)S(4)](2)(-) anion consists of two discrete edge-sharing AsS(3) pyramidal units. The As-S(t) bond distances are 2.136(7) and 2.120(7) ?, whereas the As-S(b) distances range from 2.306(7) to 2.325(7) ?. The S(b)-As-S(t) angles range from 106.2(3) to 108.2(3) degrees, and the S(b)-As-S(b) angles are 88.3(2) and 88.9(2) degrees. The [As(10)S(3)](2)(-) anion has an 11-atom As(10)S center composed of six five-membered edge-sharing rings. One of the three waist positions is occupied by a S atom, and the other two waist positions feature As atoms with exocyclic S atoms attached, making each As atom in the structure three-coordinate. The As-As bond distances range from 2.388(3) to 2.474(3) ?. The As-S(t) bond distances are 2.181(5) and 2.175(4) ?, and the As-S(b) bond distance is 2.284(6) ?. The [As(4)Se(6)](2)(-) anion features two AsSe(3) units joined by Se-Se bonds with the two exocyclic Se atoms trans to each other. The average As-Se(t) bond distance is 2.273(2) ?, whereas the As-Se(b) bond distances range from 2.357(3) to 2.462(2) ?. The Se(b)-As-Se(t) angles range from 101.52(8) to 105.95(9) degrees, and the Se(b)-As-Se(b) angles range from 91.82(7) to 102.97(9) degrees. The (77)Se NMR data for this anion in solution are consistent with its X-ray structure (delta 564 and 317 ppm, 3:1 intensity, 25 degrees C, DMF/CD(3)CN).     

Microsolvation of the dicyanamide anion: [N(CN)(2)(-)](H(2)O)n (n = 0-12)

Photoelectron spectroscopy is combined with ab initio calculations to study the microsolvation of the dicyanamide anion, N(CN)(2)(-). Photoelectron spectra of [N(CN)(2)(-)](H2O)n (n = 0-12) have been measured at room temperature and also at low temperature for n = 0-4. Vibrationally resolved photoelectron spectra are obtained for N(CN)(2)(-), allowing the electron affinity of the N(CN)2 radical to be determined accurately as 4.135 +/- 0.010 eV. The electron binding energies and the spectral width of the hydrated clusters are observed to increase with the number of water molecules. The first five waters are observed to provide significant stabilization to the solute, whereas the stabilization becomes weaker for n > 5. The spectral width, which carries information about the solvent reorganization upon electron detachment in [N(CN)(2)(-)](H2O)n, levels off for n > 6. Theoretical calculations reveal several close-lying isomers for n = 1 and 2 due to the fact that the N(CN)(2)(-) anion possesses three almost equivalent hydration sites. In all the hydrated clusters, the most stable structures consist of a water cluster solvating one end of the N(CN)(2)(-) anion.     

Theoretical Modeling of Water Exchange on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)

Density functional theory is applied to modeling the exchange in aqueous solution of H(2)O on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)]. Optimized structures for the starting molecules are reported together with trigonal bipyramidal (tbp) systems relevant to an associative mechanism. While a rigorous tbp geometry cannot by symmetry be the actual transition state, it appears that the energy differences between model tbp structures and the actual transition states are small. Ground state geometries calculated via the local density approximation (LDA) for [Pd(H(2)O)(4)](2+) and relativistically corrected LDA for the Pt complexes are in good agreement with available experimental data. Nonlocal gradient corrections to the LDA lead to relatively inferior structures. The computed structures for analogous Pd and Pt species are very similar. The equatorial M-OH(2) bonds of all the LDA-optimized tbp structures are predicted to expand by 0.25-0.30 ?, while the axial bonds change little relative to the planar precursors. This bond stretching in the transition state counteracts the decrease in partial molar volume caused by coordination of the entering water molecule and can explain qualitatively the small and closely similar volumes of activation observed. The relatively higher activation enthalpies of the Pt species can be traced to the relativistic correction of the total energies while the absolute DeltaH() values for exchange on [Pd(H(2)O)(4)](2+) and [Pt(H(2)O)(4)](2+) are reproduced using relativistically corrected LDA energies and a simple Born model for hydration. The validity of the latter is confirmed via some simple atomistic molecular mechanics estimates of the relative hydration enthalpies of [Pd(H(2)O)(4)](2+) and [Pd(H(2)O)(5)](2+). The computed DeltaH() values are 57, 92, and 103 kJ/mol compared to experimental values of 50(2), 90(2), and 100(2) kJ/mol for [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)], respectively. The calculated activation enthalpy for a hypothetical dissociative water exchange at [Pd(H(2)O)(4)](2+) is 199 kJ/mol. A qualitative analysis of the modeling procedure, the relative hydration enthalpies, and the zero-point and finite temperature corrections yields an estimated uncertainty for the theoretical activation enthalpies of about 15 kJ/mol.     

Kinetics and mechanism of formation of the platinum-thallium bond: the [(CN)(5)Pt-Tl(CN)(3)](3)(-) complex

Formation kinetics of the metal-metal bonded [(CN)(5)PtTl(CN)(3)](3)(-) complex from Pt(CN)(4)(2)(-) and Tl(CN)(4)(-) has been studied in the pH range of 5-10, using standard mix-and-measure spectrophotometric technique at pH 5-8 and stopped-flow method at pH > 8. The overall order of the reaction, Pt(CN)(4)(2)(-) + Tl(CN)(4)(-) right harpoon over left harpoon [(CN)(5)PtTl(CN)(3)](3)(-), is 2 in the slightly acidic region and 3 in the alkaline region, which means first order for the two reactants in both cases and also for CN(-) at high pH. The two-term rate law corresponds to two different pathways via the Tl(CN)(3) and Tl(CN)(4)(-) complexes in acidic and alkaline solution, respectively. The two complexes are in fast equilibrium, and their actual concentration ratio is controlled by the concentration of free cyanide ion. The following expression was derived for the pseudo-first-order rate constant of the overall reaction: k(obs) = (k(1)(a)[Tl(CN)(4)(-) + (k(1)(a)/K(f)))(1/(1 + K(p)[H(+)]))[CN(-)](free) + k(1)(b)[Tl(CN)(4)(-)] + (k(1)(b)/K(f)), where k(1)(a) and k(1)(b) are the forward rate constants for the alkaline and slightly acidic paths, K(f) is the stability constant of [(CN)(5)PtTl(CN)(3)](3)(-), and K(p) is the protonation constant of cyanide ion. k(1)(a) = 143 +/- 13 M(-)(2) s(-)(1), k(1)(b) = 0.056 +/- 0.004 M(-)(1) s(-)(1), K(f) = 250 +/- 54 M(-)(1), and log K(p) = 9.15 +/- 0.05 (I = 1 M NaClO(4), T = 298 K). Two possible mechanisms were postulated for the overall reaction in both pH regions, which include a metal-metal bond formation step and the coordination of the axial cyanide ion to the platinum center. The alternative mechanisms are different in the sequence of these steps.     

Direct Lanthanide-Transition Metal Interactions: Synthesis of (NH(3))(2)YbFe(CO)(4) and Crystal Structures of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity)

The heterometallic complex (NH(3))(2)YbFe(CO)(4) was prepared from the reduction of Fe(3)(CO)(12) by Yb in liquid ammonia. Ammonia was displaced from (NH(3))(2)YbFe(CO)(4) by acetonitrile in acetonitrile solution, and the crystalline compounds {[(CH(3)CN)(3)YbFe(CO)(4))](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity) were obtained. An earlier X-ray study of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH(3)CN)(3)YbFe(CO)(4)](infinity) is a sheetlike array with direct Yb-Fe bonds. Crystal data for {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity): monoclinic space group P2(1)/c, a = 21.515(8) ?, b = 7.838(2) ?, c = 19.866(6) ?, beta = 105.47(2) degrees, Z = 4. Crystal data for [(CH(3)CN)(3)YbFe(CO)(4)](infinity): monoclinic space group P2(1)/n, a = 8.364(3) ?, b = 9.605(5) ?, c = 17.240(6) ?, beta = 92.22(3) degrees, Z = 4. Electrical conductivity measurements in acetonitrile show that these acetonitrile complexes are partially dissociated into ionic species. IR and NMR spectra of the solutions reveal the presence of [HFe(CO)(4)](-). However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO)(4)](-) on the basis of their IR spectra. The solid state MAS (2)H NMR spectra of deuterated acetonitrile complexes give no evidence for [(2)HFe(CO)(4)](-). It appears that rupture of the Yb-Fe bond could occur in solution to generate the ion pair [L(n)Yb](2+)[Fe(CO)(4)](2-), but then the highly basic [Fe(CO)(4)](2-) anion could abstract a proton from a coordinated acetonitrile ligand to form [HFe(CO)(4)](-). However, upon crystallization, the proton could be transferred back to the ligand, which results in the neutral polymeric species.     

Mechanistic studies on the reactions of PhS(-) or [MoS(4)](2)(-) with [M(4)(SPh)(10)](2)(-) (M = Fe or Co)

Kinetic studies, using stopped-flow spectrophotometry, on the reactions of [M(4)(SPh)(10)](2)(-) (M = Fe or Co) with PhS(-) to form [M(SPh)(4)](2)(-) are described, as are the reactions between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) to form [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). The kinetics of the reactions with PhS(-) are consistent with an initial associative substitution mechanism involving attack of PhS(-) at one of the tetrahedral M sites of [M(4)(SPh)(10)](2)(-) to form [M(4)(SPh)(11)](3)(-). Subsequent or concomitant cleavage of a micro-SPh ligand, at the same M, initiates a cascade of rapid reactions which result ultimately in the complete rupture of the cluster and formation of [M(SPh)(4)](2)(-). The kinetics of the reaction between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) indicate an initial dissociative substitution mechanism at low concentrations of [MoS(4)](2)(-), in which rate-limiting dissociation of a terminal thiolate from [M(4)(SPh)(10)](2)(-) produces [M(4)(SPh)(9)](-) and the coordinatively unsaturated M site is rapidly attacked by a sulfido group of [MoS(4)](2)(-). It is proposed that subsequent chelation of the MoS(4) ligand results in cleavage of an M-micro-SPh bond, initiating a cascade of reactions which lead to the ultimate break-up of the cluster and formation of the products, [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). With [Co(4)(SPh)(10)](2)(-), at higher concentrations of [MoS(4)](2)(-), a further substitution pathway is evident which exhibits a second order dependence on the concentration of [MoS(4)](2)(-). The mechanistic picture of cluster disruption which emerges from these studies rationalizes the "all or nothing" reactivity of [M(4)(SPh)(10)](2)(-).     

Synthesis, Structure, and Reactivities of [eta(2)-P(7)M(CO)(4)](3)(-), [eta(2)-HP(7)M(CO)(4)](2)(-), and [eta(2)-RP(7)M(CO)(4)](2)(-) Zintl Ion Complexes Where M = Mo, W

Ethylenediamine (en) solutions of [eta(4)-P(7)M(CO)(3)](3)(-) ions [M = W (1a), Mo (1b)] react under one atmosphere of CO to form microcrystalline yellow powders of [eta(2)-P(7)M(CO)(4)](3)(-) complexes [M = W (4a), Mo (4b)]. Compounds 4 are unstable, losing CO to re-form 1, but are highly nucleophilic and basic. They are protonated with methanol in en solvent giving [eta(2)-HP(7)M(CO)(4)](2)(-) ions (5) and are alkylated with R(4)N(+) salts in en solutions to give [eta(2)-RP(7)M(CO)(4)](2)(-) complexes (6) in good yields (R = alkyl). Compounds 5 and 6 can also be prepared by carbonylations of the [eta(4)-HP(7)M(CO)(3)](2)(-) (3) and [eta(4)-RP(7)M(CO)(3)](2)(-) (2) precursors, respectively. The carbonylations of 1-3 to form 4-6 require a change from eta(4)- to eta(2)-coordination of the P(7) cages in order to maintain 18-electron configurations at the metal centers. Comparative protonation/deprotonation studies show 4 to be more basic than 1. The compounds were characterized by IR and (1)H, (13)C, and (31)P NMR spectroscopic studies and microanalysis where appropriate. The [K(2,2,2-crypt)](+) salts of 5 were characterized by single crystal X-ray diffraction. For 5, the M-P bonds are very long (2.71(1) ?, average). The P(7)(3)(-) cages of 5 are not displaced by dppe. The P(7) cages in 4-6 have nortricyclane-like structures in contrast to the norbornadiene-type geometries observed for 1-3. (31)P NMR spectroscopic studies for 5-6 show C(1) symmetry in solution (seven inequivalent phosphorus nuclei), consistent with the structural studies for 5, and C(s)() symmetry for 4 (five phosphorus nuclei in a 2:2:1:1:1 ratio). Crystallographic data for [K(2,2,2-crypt)](2)[eta(2)-HP(7)W(CO)(4)].en: monoclinic, space group C2/c, a = 23.067(20) ?, b = 12.6931(13) ?, c = 21.433(2) ?, beta = 90.758(7) degrees, V = 6274.9(10) ?(3), Z = 4, R(F) = 0.0573, R(w)(F(2)) = 0.1409. For [K(2,2,2-crypt)](2)[eta(2)-HP(7)Mo(CO)(4)].en: monoclinic, space group C2/c, a = 22.848(2) ?, b = 12.528(2) ?, c = 21.460(2) ?, beta = 91.412(12) degrees, V = 6140.9(12) ?(3), Z = 4, R(F) = 0.0681, R(w)(F(2)) = 0.1399.     

New members of the [Ru(diimine)(CN)(4)](2-) family: structural, electrochemical and photophysical properties

A series of complexes of the type K(2)[Ru(NN)(CN)(4)] has been prepared, in which NN is a diimine ligand, and were investigated for both their structural and photophysical properties. The ligands used (and the abbreviations for the resulting complexes) are 3-(2-pyridyl)pyrazole (Ru-pypz), 2,2'-bipyrimidine (Ru-bpym), 5,5'-dimethyl-2,2'-bipyridine (Ru-dmb), 1-ethyl-2-(2-pyridyl)benzimidazole (Ru-pbe), bidentate 2,2':6',2'-terpyridine (Ru-tpy). The known complexes with = 2,2'-bipyridine (Ru-bpy) and 1,10-phenathroline (Ru-phen) were also included in this work. A series of crystallographic studies showed that the [Ru(NN)(CN)(4)](2-) complex anions form a range of elaborate coordination networks when crystallised with either K(+) or Ln(3+) cations. The K(+) salts are characterised by a combination of near-linear Ru-CN-K bridges, with the cyanides coordinating to K(+) in the usual 'end-on' mode, and unusual side-on pi-type coordination of cyanide ligands to K(+) ions. With Ln(3+) cations in contrast only Ru-CN-Ln near-linear bridges occurred, affording 1-dimensional helical or diamondoid chains, and 2-dimensional sheets constituted from linked metallamacrocyclic rings. All of the K(2)[Ru(CN)(4)] complexes show a reversible Ru(II)/Ru(III) couple (ca.+0.9 V vs. Ag/AgCl in water), the exception being Ru-tpy whose oxidation is completely irreversible. Luminescence studies in water showed the presence of (3)MLCT-based emission in all cases apart from Ru-bpym with lifetimes of tens/hundreds of nanoseconds. Time-resolved infrared studies showed that in the (3)MLCT excited state the principal C-N stretching vibration shifts to positive energy by ca. 50 cm(-1) as a consequence of the transient oxidation of the metal centre to Ru(III) and the reduction in back-bonding to the cyanide ligands; measurement of transient decay rates allowed measurements of (3)MLCT lifetimes for those complexes which could not be characterised by luminescence spectroscopy. A few complexes were also examined in different solvents (MeCN, dmf) and showed much weaker emission and shorter excited-state lifetimes in these solvents compared to water.     

Large pressure-induced increase in luminescence intensity for the [Pd(SCN)(4)](2-) complex

Luminescence from a square planar [Pd(SCN)(4)](2-) complex shows very large increases in intensity and lifetime from ambient pressures up to 27 kbar. The band maximum shows a blue-shift of approximately 29 cm(-1)/kbar. These spectroscopic observations can be rationalized qualitatively by considering multiple effects, and they underline the strong interrelation between molecular structure, energies, and geometries of excited electronic states, and optical properties.     

Ge(7)O(13)(OH)(2)F(3)](3)(-).Cl(-).2[Ni(dien)(2)](2+): the first chainlike germanate templated by a transition metal complex

The first chainlike germanate, [Ge(7)O(13)(OH)(2)F(3)](3)(-).Cl(-).2[Ni(dien)(2)](2+), has been solvothermally synthesized by using Ni(dien)(2)(2+) cations as the template and characterized by IR, SEM, TGA, powder X-ray diffraction (PXRD), energy-dispersive X-ray analysis (EDXA), elemental analysis, and single-crystal X-ray diffraction, respectively. This compound crystallized in the monoclinic space group P2/nwith a = 8.8904(2) A, b = 17.4374(3) A, c = 13.2110(3) A, beta = 101.352(1) degrees, V = 2007.97(7) A(3), and Z = 2. Interestingly, the structure contains two types of chiral mer-[Ni(dien)(2)](2+) cations and two types of chiral chains, one left-handed and the other right-handed, which lead to a racemic compound. The orderly separation of achiral s-fac-[Ni(dien)(2)](2+) and chiral mer-[Ni(dien)(2)](2+) isomers was found in the structure. The structure is stabilized by N-H.O(F, Cl) hydrogen bonds.     

Te(CN)4] versus [Te(CN)3(micro-CN)](n)

Solvent molecules have a great influence on the structure and stability of tellurium tetracyanide; whereas Te(CN)4 x (diglyme)(2) contains monomeric Te(CN)4 units, [Te(CN)3(micro-CN) x diglyme](n) is a coordination polymer.     

Preparation and characterization of the argentates: [Ag[P(CF(3))(2)](2)](-), [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-) (M = Cr, W), and [Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)](-): X-ray crystal structure of [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)

The first example of a mononuclear diphosphanidoargentate, bis[bis(trifluoromethyl)phosphanido]argentate, [Ag[P(CF(3))(2)](2)](-), is obtained via the reaction of HP(CF(3))(2) with [Ag(CN)(2)](-) and isolated as its [K(18-crown-6)] salt. When the cyclic phosphane (PCF(3))(4) is reacted with a slight excess of [K(18-crown-6)][Ag[P(CF(3))(2)](2)], selective insertion of one PCF(3) unit into each silver phosphorus bond is observed, which on the basis of NMR spectroscopic evidence suggests the [Ag[P(CF(3))P(CF(3))(2)](2)](-) ion. On treatment of the phosphane complexes [M(CO)(5)PH(CF(3))(2)] (M = Cr, W) with [K(18-crown-6)][Ag(CN)(2)], the analogous trinuclear argentates, [Ag[(micro-P(CF(3))(2))M(CO)(5)](2)](-), are formed. The chromium compound [K(18-crown-6)][Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)] crystallizes in a noncentrosymmetric space group Fdd2 (No. 43), a = 2970.2(6) pm, b = 1584.5(3) pm, c = 1787.0(4), V = 8.410(3) nm(3), Z = 8. The C(2) symmetric anion, [Ag[(micro-P(CF(3))(2))Cr(CO)(5)](2)](-), shows a nearly linear arrangement of the P-Ag-P unit. Although the bis(pentafluorophenyl)phosphanido compound [Ag[P(C(6)F(5))(2)](2)](-) has not been obtained so far, the synthesis of its trinuclear counterpart, [K(18-crown-6)][Ag[(micro-P(C(6)F(5))(2))W(CO)(5)](2)], was successful.     

Solid-state ligand dynamics in interpenetrating Mn[N(CN)(2)](2)(pyrazine): a neutron spectroscopy study

We have used quasielastic neutron scattering to probe the solid-state ligand dynamics in the coordination polymer Mn[N(CN)(2)](2)(pyz) [pyz = pyrazine] which has double-interpenetrating 3D lattices. A reversible structural phase transition occurs at 410 K as shown by neutron spectroscopy and differential scanning calorimetry. The origin of this transition is linked to rotational dynamics associated with the bridging pyz ligands. At 425 K, the pyrazine ring motion can be solely regarded as a 180 degrees reorientational jump about the axis defined by the Mn-N coordinative bonds, occurring with a correlation time of approximately 70 ps. This model can be extended to the 200-410 K temperature region using high-resolution backscattering spectroscopy to measure an identical motion on the time scale of nanoseconds with an activation energy of 24 +/- 2 kJ mol(-1). In contrast, no quasielastic scattering is seen for the 2D layered variant beta-Cu[N(CN)(2)](2)(pyz), owing to its more compact layer packing motif. Importantly, this work represents the very first study of solid-state rotational dynamics in an interpenetrating lattice structure.     

A theoretical study of the NMR spin-spin coupling constants of the complexes [(NC)(5)Pt-Tl(CN)(n)](n-) (n = 0-3) and [(NC)(5)Pt-Tl-Pt(CN)(5)](3-): a lesson on environmental effects

The molecular geometries and the nuclear spin-spin coupling constants of the complexes [(NC)(5)Pt-Tl(CN)(n)](n-), n = 0-3, and the related system [(NC)(5)Pt-Tl-Pt(CN)(5)](3-) are studied. These complexes have received considerable interest since the first characterization of the n = 1 system by Glaser and co-workers in 1995 [J. Am. Chem. Soc. 1995, 117, 7550-7551]. For instance, these systems exhibit outstanding NMR properties, such as extremely large Pt-Tl spin-spin coupling constants. For the present work, all nuclear spin-spin coupling constants J(Pt-Tl), J(Pt-C), and J(Tl-C) have been computed by means of a two-component relativistic density functional approach. It is demonstrated by the application of increasingly accurate computational models that both the huge J(Pt-Tl) for the complex (NC)(5)Pt-Tl and the whole experimental trend among the series are entirely due to solvent effects. An approximate inclusion of the bulk solvent effects by means of a continuum model, in addition to the direct coordination, proves to be crucial. Similarly drastic effects are reported for the coupling constants between the heavy atoms and the carbon nuclei. A computational model employing the statistical average of orbital-dependent model potentials (SAOP) in addition to the solvent effects allows to accurately reproduce the experimental coupling constants within reasonable limits.