Electronic communications mediated by metal clusters and pi conjugated systems 2

Chapter One Introduction 1.1 Mixed-Valence Compounds Mixed-valence (MV) complexes have been commanding the attention of chemists for decades.1-4 One of the reasons is the wide occurrence of MV species in Nature as numerous metalloproteins such as ferredoxins contain MV clusters as their cofactors.3b, In addition, synthetic MV complexes are models for understanding intramolecular electron transfer.6 Electron transfer reactions are classified into outer-sphere and innersphere reactions.7 In inner-sphere electron transfers, two redox partners would form a discrete complex in which the two metal centers are bridged by ligand(s). Many MV complexes capture the essential features of these intermediates; hence studying the electronic structures and charge transfer in MV complexes would lead to a better understanding of inner-sphere electron transfer reactions. In the area of molecular magnetism, a major concern is to search for polymetallic complexes that have a high spin ground state.4b, 8a This requires knowledge of how electron spins in metal ions interact and how the medium between the metal centers mediates the interaction. It is apparent that MV complexes which usually have two or more metal ions in different spin states are a good starting point for the study of magnetic interaction in molecules. Recent interest in MV complexes also arose from their potential applications as molecular switch4a,9 and wire.4e,10 Given the importance of the compounds, it is not surprising that a myriad of MV complexes of different design has been reported in the literature and the complexes have received rigorous experimental investigations1,2,11 and theoretical treatments.4a,12 The following section is a brief introduction to the basic physical and chemical properties of MV complexes. 1.2 Classification of MV Complexes. The basic components of all MV complexes are two or more metal ions (M) and bridges or spacers which link the metal ions together (Scheme 1.1). By default, the metal ions are in different oxidation states, a+ and b+. Because of the presence of the bridge, in principle, charge can transfer or delocalize from one metal center to the other. If b+ is > a+, there are two possible scenarios: (i) an electron delocalizes from Ma+ (low valence) to Mb+( high valence), the so-called electron transfer mechanism or (ii) a hole delocalizes from the Ma+ to Mb+, the so-called hole transfer mechanism. Scheme 1.1 Bridge b+ a+ M - e M b>a Bridge a+ M + Mb+ Whether the charge delocalization is via electron or hole transfer is related to the electronic structures of the metal ions and the bridge. In general, small energy gap between the filled metal orbitals and the empty antibonding orbitals of the bridges would favor the electron transfer mechanism while a combination of the low-lying empty metal orbitals and high energy bridge’s bonding orbitals would favor the hole transfer mechanism. The extent of charge delocalization is dependent on several factors: 9b, 27b the nature of the metal ions, the geometry and length of the bridge, the electronic structures of the bridges, the solvent, and in some cases, the properties of the ancillary ligands coordinated to the metal ions. On the basis of the extent of charge delocalization, Robin and Day divided MV complexes into Classes I, II and III.1, 4, 13 Class I MV species are compounds wherein there is no charge delocalization between the metal centers; in other words, the valency is trapped in one of the centers. The situation can be represented by the energy diagram shown in Scheme 1.2 Scheme 1.2 Energy X Reaction Coordinate The two potential energy curves, each representing one of the two states of the MV complex (before and after charge transfer) intersect but there is no splitting of curves at the intersection point. The reason for the absence of splitting is that there is no electronic communication or interaction between the two metal ions. As the curves are not separated at the intersection point, the system would not be able to “crossover” from one state to another. In other words, that there is no charge delocalization is Class I systems. Usually MV complexes whose metal ions are separated far apart belong to Class I as the metal-metal ion interact decreases as metal-metal distance increases. In contrast to Class I MV species, in Class II MV compounds, weak interactions of the two redox centers exist. This can be illustrated by Scheme 1.3. Scheme 1.3 Energy Eop 2HAB Reaction Coordinate The electronic interactions between the metal ions lead to a small splitting of potential energy curves at the intersection, giving rise to an upper energy surface and a lower energy surface. As a result, the system can crossover from one state to the other state and hence charge transport through the bridge is possible. The extent of the charge delocalization is governed by the extent of splitting, HAB, which is commonly known as the electronic coupling parameter. The larger HAB is, the higher the extent of electron delocalization in Class II complexes. Experimental1,4,6b,11 and theoretical work12 have shown that HAB decreases exponentially with the distance between the redox centers and it is also sensitive to the orbital interactions between the metal centers and the bridge. Crossing over the states via the lower energy surface is known as thermal electron transfer as heat energy is required to promote the system from its equilibrium to the intersection point. On the other hand, the system can crossover to the other state by absorbing a photon of correct energy, Eop, which is equal to the vertical energy difference between the equilibrium position and the upper energy surface. This photo-induced electron transfer would give rise to absorption in the UV-vis or near infrared absorption spectrum of the MV complex and the parameters of the band, which is known as intervalence-charge-transfer (IVCT) absorption band, could provide the magnitude of HAB for the Class II MV species.1,4,6b,12 According to the theory of Hush,12a the relationship between HAB and the half-height bandwidth (∆ν1/2), band maxima (νmax), extinction coefficient (εmax) and the transition moment (d) (which is usually taken as the separation between the two redox centers) is given by equation 1.1. H AB = 2.05 × 10 −2 ε max (∆ν 1/ )ν max d (equation 1.1) For Class III MV complexes, due to the strong interactions between the metal centers, the valency completely delocalizes over the entire molecule and molecules are only in one state instead of two states in Classes I and II. The formal oxidation state of the metal ions is the average of the two oxidation states ((a+b)/2). The energy diagram for Class III complexes is completely different from that of Classes I and II. As shown in Scheme 1.4, the two potential energy curves merge, giving a single low energy curve and a single upper energy curve. There is only one energy minima in the low energy curve, in contrast to the double minima observed in the energy diagram of the other Classes. Scheme 1.4 Energy 2HAB Reaction Coordinate The strong coupling leads to a large separation between the lower and upper energy curves and the absorption of photon of the right energy would promote the complex from the ground to the excited state. It is noted that the demarcation of the three classes of MV complexes is by no means sharp, especially as it is sometimes difficult to determine if a MV complex is Class II or III and hence it is not uncommon to find MV compounds in the literature labeled as Class II/III. This is best illustrated by the Creutz-Taube ion, perhaps the most well-known MV complex. The complex, first reported by Creutz and Taube in 1969, is composed of two Ru(NH3)5 units bridged by a pyrazine (Figure 1.1).1 The metal ions are supposedly in the oxidation states +2 and +3. 5+ H 3N H 3N NH3 NH3 Ru N NH3 Figure 1.1 N H3N NH3 NH3 Ru NH3 NH3 Creutz-Taube ion At first, the ion was believed to belong to Class III.1a However, subsequent studies showed that whether the valency is delocalized or localized is dependent on the time scale of the spectroscopic techniques used to probe the metal ions.2b For example, NMR spectroscopic studies, which have a time resolution of 10-6 s, suggested that the charge is completely delocalized while faster techniques such as Resonance Raman spectroscopy (10-13 s) near infrared absorption (10-11 s), electron paramagnetic resonance (10-9 s) and Mössbauer (10-9 s) spectroscopy indicated localized valency. Another method commonly used to distinguish Class II and Class III MV complexes is to compare the half-height bandwidth (∆ν1/2) of the low energy absorption of the complexes with the one predicted by theory. According to Hush,12b ν1/2 of the IVCT absorption band of Class II MV complexes should be related to the band maxima by equation 1.2. ∆ν1/2 = (2310νmax)1/2cm-1 (equation 1.2) For Class III complexes, there is no real IVCT transition as the valency is completely delocalized in the ground state. Nevertheless, they are found to exhibit intense and low energy absorption, usually in the near infrared region, which corresponds to the electronic transition from the ground state to the excited state (Scheme 1.4). And the ∆ν1/2s of the absorption bands are found to be smaller than predicted by Hush’s equation. However, recent studies14 showed that some Class II complexes show IVCT with ∆ν1/2 smaller than the theoretical values. On the other hand, it is relatively simpler to distinguish Class I and Class II species. Class II complexes usually show weak to moderately intense IVCT absorption bands in the low UV-vis or near infrared region whereas, due to the lack of electronic communications between the metal centers, no such absorption band is found in the spectra of Class I species. In addition, electrochemical measurements showed that the reduction potentials of the metal ions in Class II complexes are split by more than 70 mV while the reduction potentials of the metal centers in Class I compounds are less than 70 mV.2b 1.3 Stability of Mixed-Valence Complexes In principle, an MV complex Ma+Mb+ can be generated from comproportionation reactions between isovalent Ma+Ma+ (fully reduced) and Mb+Mb+ (fully oxidized) (reaction 1.1). Ma+ Ma+ fully reduced + b+ M Ma+ Kc b+ M fully oxidized Mb+ mixed-valence Reaction 1.1 Comproportionation equilibrium The equilibrium constant of the reaction, known as comproportionation constant Kc = [MV]2/[fully oxidized][fully reduced], is a measure of the stability of the MV complex with respect to the isovalent compounds (scheme 1.5). Partly due to electronic communications between them, the successive oxidations of the two metal ions Ma+bridge-Ma+ to Ma+-bridge-Mb+ and Mb+-bridge-Mb+ would be at different reduction potentials E1 and E2 , and the value of Kc can be calculated from the potential difference, ∆E1/2, which is equal to E2 – E1 (equation 1.3).1,2 10 Figure 2.2 ORTEP drawing of 1•2CF3SO3• H2O (All phenyl rings and hydrogen atoms are removed and one anion CF3SO3- is not shown, thermal ellipsoids are set at 50% probability level). Figure 2.3 34 ORTEP drawing of 2•PF6 (All phenyl rings and hydrogen atoms are removed and the anion PF6 is not shown, thermal ellipsoids are set at 50% probability level). Figure 2.4 Figure 2.5 37 31 P NMR spectra of 1•2CF3SO3 31 40 P NMR spectra of 2•PF6 40 Figure 2.6 1H NMR spectra of 1•2CF3SO3 41 Figure 2.7 1H NMR spectra of 2•PF6 42 Figure 2.8 Cyclic voltammogram of 1•2CF3SO3 in CH3CN at room temperature; reference electrode: Ag/AgNO3; working electrode: Pt; scan rate = 50 mVs-1. 43 Figure 2.9a. Cyclic voltammogram of 2•PF6 in CH3CN at room temperature; reference electrode: Ag/AgNO3; working electrode: Pt; scan rate = 50 mVs-1. Figure 2.9b 44 Differential pulse voltammogram of 2•PF6 in CH3CN at room temperature; reference electrode: Ag/AgNO3; working electrode: Pt; scan rate = 20 mVs-1 45 Figure 2.10 Near infrared absorption spectrum of an acetonitrile solution of 2•PF6 (3.14 × 10-3 M) and one molar equiv. of Cp2FePF6 at room temperature. The spikes are due to solvent absorption. 50 Figure 2.11 Diagram showing electrostatic interactions in the complexes involved in the comproportionation reaction of compound 22+ 51 Figure 2.12 Interactions of orbitals between copper ions and acetylide ligand 54 156 Figure 3.1 Typical structure of complexes with σ-Pt-Pt bond 61 Figure 3.2 Qualitative molecular orbital diagram for binuclear d9-d9 Pt(I)-Pt(I) complexes 63 Figure 3.3 “A-frame” reaction between PtI-PtI complexes and d10 metals 64 Figure 3.4 ORTEP drawing of 3•Et2O (H atoms and Et2O are omitted for clarity, thermal ellipsoids are set at 50% probability level). Figure 3.5 Figure 3.6 31 HNMR of spectrum of complex in CD2Cl2 P NMR spectra of in CD2Cl2 66 68 68 Figure 3.7a Cyclic voltammogram of (0.9 mM) in CH2Cl2 at a scan rate of 20 mVs-1. Working electrode: glassy carbon (area=0.07 cm2), reference electrode: Ag/AgNO3 (0.1M),. Figure 3.7b 71 Differential pulse voltammogram of (0.9 mM) in CH2Cl2; scan rate = 10 mVs-1. Figure 3.7c 72 Extended cyclic voltammogram of (0.9 mM) in CH2Cl2 showing cathodic scan. Working electrode: glassy carbon (area=0.07 cm2), reference electrode: Ag/AgNO3 (0.1M). Figure 3.8 73 UV-vis-NIR absorption spectrum of 3+ in CH2Cl2 at 297 K (Inset: Beer plot of the absorbance of 11300 cm-1 absorption vs the concentration of 3+ as calculated from equation 3.1). Figure 3.9 ORTEP drawing of (H atoms are omitted for clarity, thermal ellipsoids are set at 50% probability level). Figure 3.10 76 78 Top view of complex showing the Pt2Au triangle; (dppm are removed for clarity, thermal ellipsoids are set at 50 % probability level). 79 157 Figure 3.11 Figure 3.12 31 H NMR of complex P NMR spectrum of complex 82 83 Figure 3.13a Cyclic voltammogram of (0.9 mM) in CH2Cl2 at a scan rate of 20 mVs-1. Working electrode: glassy carbon (area=0.07 cm2), reference electrode: Ag/AgNO3 (0.1M), supporting electrolyte: 0.1 M tetrabutylammonium hexafluorophosphate. The FcH+/FcH couple is used as internal reference. All measurements were taken at room temperature (22°C). 86 Figure 3.13b Differential pulse voltammogram of (0.9 mM) in CH2Cl2 87 Figure 3.13c Cyclic voltammogram of (0.9 mM) in CH2Cl2 showing extended anodic and cathodic scans, scan rate = 20 mV/s. 87 Figure 3.14a Cyclic voltammogram of (0.3 mM) in CH2Cl2 at a scan rate of 20 mVs-1. Figure 3.14b Differential pulse voltammogram of (0.3 mM) in CH2Cl2 88 Figure 3.14c Cyclic voltammogram of (0.3 mM) in CH2Cl2 showing extended anodic and cathodic scans. Working electrode: glassy carbon (area=0.07 cm2), reference electrode: Ag/AgNO3 (0.1M), supporting electrolyte: 0.1 M tetrabutylammonium hexafluorophosphate. The FcH+/FcH couple is used as internal reference. All measurements were taken at room temperature (22°C). Figure 4.1. ORTEP drawing of 6•Et2O (All phenyl rings and hydrogen atoms are removed, thermal ellipsoids are set at 50% probability level). Figure 4.2 89 109 ORTEP drawing of 7•2CH2Cl2 (All phenyl rings and hydrogen atoms are removed, thermal ellipsoids are set at 50% probability level). 112 158 ORTEP drawing of 8•CH2Cl2 (All phenyl rings and hydrogen atoms are Figure 4.3 removed, thermal ellipsoids are set at 50% probability level). 114 Figure 4.4 1H spectrum of complex 117 Figure 4.5 H NMR spectrum of complex Figure 4.6 1H NMR spectrum of complex 117 118 Figure 4.7 31 P NMR spectrum of complex 118 Figure 4.8 31 P NMR spectrum of complex 119 Figure 4.9 31 P NMR spectrum of complex 119 Figure 4.10 Cyclic voltammogram of in CH2Cl2 at room temperature; reference electrode Ag/AgNO3; working electrode: Pt; scan rate = 20 mV/s Figure 4.11 120 CV of measured in CH2Cl2 (0.1 M n-Bu4NPF6), working electrode: glassy carbon electrode (0.07 cm2), reference electrode: Ag/AgNO3 (0.1M in CH3CN), counter electrode: platinum wire, concentration of complex = 1.2 mM, scan rate = 10 mV/s Figure 4.12 122 CV of measured in CH2Cl2 (0.1 M n-Bu4NPF6), working electrode: glassy carbon electrode (0.07 cm2), reference electrode: Ag/AgNO3 (0.1M in CH3CN), counter electrode: platinum wire, concentration of complex = 1.2 mM, scan rate = 10 mV/s Figure 4.13 123 CV of measured in: CH2Cl2 (0.1 M n-Bu4NPF6), working electrode: glassy carbon electrode (0.07 cm2), reference electrode: Ag/AgNO3 (0.1M in CH3CN), counter electrode: platinum wire, concentration of complex = 1.2 mM, scan rate = 10 mV/s 124 159 Figure 4.14 CV of measured in: CH2Cl2 (0.1 M n-Bu4NPF6), working electrode: glassy carbon electrode (0.07 cm2), reference electrode: Ag/AgNO3 (0.1M in CH3CN), counter electrode: platinum wire, concentration of complex = 1.2 mM, scan rate = 10 mV/s 125 Figure 4.14 σ-Interaction diagram for complex es and 129 Figure 4.15 π-Interaction diagram for complexes and 130 Figure 4.16 σ-Interaction diagram for complex 132 Figure 4.17 π-Interaction diagram for complex 133 160 List of Tables Table 2.1 Selected bond length and angles for 1•2CF3SO3•H2O 35 Table 2.2 Selected bond length and angles for 2•PF6 38 Table 2.3 Reduction potentials and Kc of compounds 1•2CF3SO3 and 2•PF6 in comparison with other bis(ferrocenylacetylide) compounds. 47 Table 3.1 Selected bond length (Å) and angles (deg) for 3•Et2O 65 Table 3.2 Selected bond length (Å) and angles (deg) for 77 Table 3.3 Selected bond length (Å) and angles (deg) for 80 Table 3.4 Comproportionation constants Kc of bis(ferrocenylacetylide) Complexes 91 Table 4.1 Selected bond length (Å) and angles (deg) for 6•Et2O 108 Table 4.2 Selected Bond Distance and Angles for 7•2CH2Cl2 111 Table 4.3 Selected Bond Distance and Angles for 8•CH2Cl2 113 Table 4.4 1H and 31P NMR spectroscopic data 116 Table 4.5 Electrochemicla date of complexes 6, 7, 126 161 Appendix III Crystallographic , refinement parameters and UV-vis absorption spectra 162 III-1 Crystal data and structure refinement for 1•2CF3SO3 Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Extinction coefficient Largest diff. Peak and hole C89H76Ag3F6FeO7P6S2 2000.90 293(2) K 0.71073 Å Monoclinic P2(1)/n a = 14.1959(1) Å b = 47.4768(3) Å c = 14.4358(2) Å 8735.53(15) Å3 1.521 g/cm3 1.049 mm-1 4036 0.4 × 0.38 × 0.16 mm3 1.63 to 25.00º α = 90° β = 116.12(1)° γ = 90° -18 ≤ h ≤ 18, -63 ≤ k ≤ 24, -19 ≤ l ≤ 19 43813 15282 [R(int) = 0.0321] Sadabs (Sheldrick, 1996) 0.8312 and 0.6908 Full-matrix least-squares on F2 15245 / 167 / 1004 1.155 R1 = 0.0571, wR2 = 0.1298 R1 = 0.0739, wR2 = 0.1472 0.00079(7) 1.259 and –0.682 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 163 III-2 Crystal data and structure refinement for 2•PF6 Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions C99H84Cu3F6Fe2P7 1906.77 293(2)K 0.71073Å Monoclinic P2(1)/c a = 20.1214(3) Å α = 90° b = 15.6884(2) Å β = 108.216(1)° c = 30.8735(3) Å γ = 90° 9257.5(2) Å3 1.368 g/cm3 1.162 mm-1 3904 0.3 × 0.22 × 0.08 mm3 data 1.68 to 25.00º Volume Z Density Absorption coefficient F(000) Crystal size Theta range for collection Index ranges Reflections collected Independent reflections Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Extinction coefficient Largest diff. Peak and hole -24 ≤ h ≤ 26, -13 ≤ k ≤ 21, -41 ≤ l ≤ 38 44885 16083 [R(int) = 0.0444] Sadabs (Sheldrick, 1996) 0.8140 and 0.6574 Full-matrix least-squares on F2 15852 / 168 / 987 1.036 R1 = 0.0627, wR2 = 0.1619 R1 = 0.1056, wR2 = 0.1889 0.00038(10) 1.022 and –0.708 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 164 III-3 Crystal data and structure refinement for complex 3•Et2O Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 30.02º Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Largest diff. Peak and hole C78H72Fe2OP4Pt2 1651.12 223(2)K 0.71073Å Triclinic P-1 a = 11.7327(6)Å α = 89.990(1)° b = 16.1222(8)Å β = 82.575(1)° c = 17.7260(9)Å γ = 88.062(1)° 3322.9(3)Å3 1.650g/cm3 4.767mm-1 1632 0.2 × 0.14 × 0.12 mm3 1.71 to 30.02º -16≤ h ≤ 16, -22≤ k ≤ 22, -24≤ l ≤ 24 51762 19273[R(int) = 0.0541] 99.1% Sadabs (Sheldrick, 1996) 0.6386 and 0.5156 Full-matrix least-squares on F2 19273 / / 761 1.012 R1 = 0.0362, wR2 = 0.0679 R1 = 0.0507, wR2 = 0.0702 2.168 and –0.739 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 165 III-4 Crystal data and structure refinement for complex Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 30.04º Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Extinction coefficient Largest diff. Peak and hole C74H62AuClFe2P4Pt2 1809.41 223(2)K 0.71073Å Triclinic P-1 a = 13.1768(8) Å α = 89.858(1)° b = 14.1641(9) Å β = 76.884(1)° c = 17.7187(11) Å γ = 76.5241(1)° 3127.6(3) Å 1.921 g/cm3 7.436 mm-1 1740 0.36 × 0.24 × 0.14 mm3 1.63 to 30.04º -18 ≤ h ≤ 18, -19 ≤ k ≤ 19, -24 ≤ l ≤ 24 46642 17545 [R(int) = 0.0628] 96.0% Sadabs (Sheldrick, 1996) 0.4149 and 0.2520 Full-matrix least-squares on F2 17545 / / 757 1.048 R1 = 0.0443, wR2 = 0.0842 R1 = 0.0676, wR2 = 0.0880 0.00079(7) 3.293 and -1.415 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 166 III-5 Crystal data and structure refinement for Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 30.02º Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Largest diff. Peak and hole C74H62AuBrFe2P4Pt2 1853.87 223 (2) K 0.71073 Å Triclinic P-1 a = 13.2436(9) Å α = 89.494(1)° b = 14.1793(9) Å β = 77.104(1)° c = 17.8231(12) Å γ = 76.508(1)° 3169.2(4) Å3 1.943 g/cm3 7.927 mm-1 1776 0.34 × 0.20 × 0.20 mm3 1.48 to 30.02º -18≤ h ≤18 , -19≤ k ≤ 19, -24≤ l ≤ 25 47316 17757[R(int) = 0.0648] 96.0 % Sadabs (Sheldrick, 1996) 0.2938 and 0.1739 Full-matrix least-squares on F2 17757 / / 757 1.047 R1 = 0.0454, wR2 = 0.0714 R1 = 0.0786, wR2 = 0.0733 2.960 and –1.328 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 167 III-6 Crystal data and structure refinement for 6•Et2O Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 26.37° Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Largest diff. Peak and hole C66H64Cl2FeOP4Pt2 1513.98 293(2) K 0.71073 Å Triclinic P-1 a = 13.6887(1) Å α = 81.340(1)° b = 14.4719(2) Å β = 76.153(1)° c = 17.7935(2) Å γ = 63.728(1)° 3064.91(6) Å 1.641 g/cm3 5.019 mm-1 1488 0.4 × 0.2 × 0.14 mm3 1.75 to 26.37º -17 ≤ h ≤ 16, -18 ≤ k ≤ 18, -22 ≤ l ≤ 22 24293 12105[R(int) = 0.0528] 96.6 % Sadabs (Sheldrick, 1996) 0.5450 and 0.2937 Full-matrix least-squares on F2 12105 /12 / 672 1.164 R1 = 0.0628, wR2 = 0.1541 R1 = 0.0756, wR2 = 0.1633 2.394 and –2.908 e. Å-3 R1 = (||Fo|- |Fc||)/(|Fo|); wR2 = [w(Fo2 - Fc2)/w(Fo4)]1/2 GOF = [(w(Fo2- Fc2)2/(n-p)]1/2 168 III-7 Crystal data and structure refinement for 7•2CH2Cl2 Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 25.00º Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Extinction coefficient Largest diff. Peak and hole C63H56Cl4FeP4Pd2 1347.41 203(2) K 0.71073 Å Triclinic P-1 a = 14.3059(2) Å α = 80.544(1)° b = 14.44441(2) Å β = 71.517(1)° c = 17.8361(3) Å γ = 67.986(1)° 3236.29(8) Å 1.383 g/cm3 1.070 mm-1 1360 0.6 × 0.6 × 0.56 mm3 1.91 to 25.00º -15 ≤ h ≤ 17, -17 ≤ k ≤ 16, -21 ≤ l ≤ 19 16441 10837 [R(int) = 0.0466] 95.3 % Sadabs (Sheldrick, 1996) 0.6474 and 0.4151 Full-matrix least-squares on F2 10837 / 18 / 670 1.122 R1 = 0.0982, wR2 = 0.2672 R1 = 0.1080, wR2 = 0.2756 0.007(7) 3.142 and –2.392 e. Å-3 169 III-8 Crystal data and structure refinement for 8•CH2Cl2 Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions Volume Z Density Absorption coefficient F(000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 25.00º Absorption correction Max. and min. transmission Refinement method Data / restrains / parameters Goodness-of –fit on F2 Final R indices [I > 2sigma(I)] R indices (all data) Extinction coefficient Largest diff. Peak and hole C62H54Cl2FeP4Pd2 1262.48 566(2) K 0.71073 Å Trigonal P-1 a = 16.017(4)(4) Å α = 90° b = 16.017(4)(4) Å β = 90° c = 20.353(7) Å γ = 120° 4522(2) Å3 1.391 Mg/m3 1.058 mm-1 1914 0.56 × 0.46 × 0.16 mm3 1.47 to 25.00º -19 ≤ h ≤ 18, -18 ≤ k ≤ 18, -24 ≤ l ≤ 15 25934 5298 [R(int) = 0.0747] 100.0 % Sadabs (Sheldrick, 2001) 0.8489 and 0.5887 Full-matrix least-squares on F2 5298 / 250 / 335 0.904 R1 = 0.0611, wR2 = 0.1648 R1 = 0.1367, wR2 = 0.2064 -0.10(7) 0.394 and –0.239 e. Å-3 Because the complex is very unstable, even in calibrate tube, it still lost solvent during the measurement. One of the phenyl rings has large thermal parameters and no satisfactory disorder model could be found. As a result, the carbon atoms in the ring were treated as a regular hexagon. In addition, the Cp ring is disordered. 170 III-9    ________ UV-vis absorption spectra of complexes and recorded in acetonitrile complex (2.16 × 10–4 mol. L-1 ) complex (2.12 × 10–4 mol. L-1 ) 171 [...]... Ag(1)-Ag (2) 3 .24 51(6) Ag(1)-Ag (2) -Ag(3) 59.851(1) Ag(1)-Ag(3) 3 .24 16(6) Ag (2) -Ag(1)-Ag(3) 60.191(1) Ag (2) -Ag(3) 3 .25 27(6) Ag(1)-Ag(3)-Ag (2) 59.958(1) Ag(1)-P(1) 2. 4740(1) Ag(1)-C(1)-Ag (2) 90.6 (2) Ag(1)-P(6) 2. 4551(1) Ag(1)-C(1)-Ag(3) 89.6 (2) Ag (2) -P(3) 2. 4804 (2) Ag (2) -C(1)-Ag(3) 91.9 (2) Ag(1)-C(1) 2. 320 (6) C(1)-Ag(1)-Ag (2) 43.78(1) Ag (2) -C(1) 2. 245(5) C(1)-Ag(1)-P(1) 108. 82( 1) Ag(3)-C(1) 2. 281(6) C(1)-Ag(1)-P(6)... shown by Long27a and Wolf 27 b-c to be a Class II MV species (Kc = 6100 20 00) Detailed electrochemical and spectroscopic studies on the complex and its derivatives trans-trans-trans-[Ru(PPh3 )2( CO)(L)(C≡CFc )2] and cis- [Ru(dppm )2( C≡CFc )2( µ-CuI)] provided additional insight into the role played by the central ruthenium ion in mediating electronic communication .27 b 20 Ph2P C C Ph2P PPh2 Ru C C PPh2 Ph2P... structure and selected structural parameters of the complex are depicted in Figure 2. 2 and Table 2. 1, respectively 33 Figure 2. 2 ORTEP drawing of 1•2CF3SO3• H2O (All phenyl rings and hydrogen atoms are removed and one anion CF3SO3- is not shown, thermal ellipsoids are set at 50% probability level) 34 Table 2. 1 Selected bond length and angles for 1•2CF3SO3•H2O Bond Lengths (Å) Bond angles (deg) Ag(1)-Ag (2) ... 124 .48(5)º and 115 .27 (1)º, respectively The capping of FcC≡C- is slightly asymmetric as the Ag-C distances range from 2. 245(5) to 2. 320 (6) Å Similar Ag-C distances and distortion are found in the analogous complex 35 [Ag3(dppm)3(C≡C-C6H4-NO2-p) ]2+ (d(Ag-C) = 2. 224 (5) – 2. 349(6) Å).35a The average capping angle, defined as Ag-C(1)-Ag, is 90.7 (2) º The three Ag-Ag distances are very close (dAg-Ag = 3 .24 16(6)... linear array with the trimetallic center and the electronic communication mediated by the CuI3 cluster will be investigated 2. 2 Results and Discussion 2. 2.1 Syntheses and Structures Reacting Ag2(dppm )2( CF3SO3 )2 with ferrocenylacetylide gives rise to the monoacetylide [AgI3(dppm)3(µ3-η1-C≡CFc)]•2CF3SO3 (1•2CF3SO3) However, the diacetylide [Ag3(dppm)3(µ3-η1-C≡CFc )2] + remains elusive even when a large excess... trinuclear Ag(I) and Cu(I) clusters will be explored Our aim is to understand the electronic communication, if there is any, mediated by trinuclear d10 clusters Metal clusters are complicated molecules which commonly contain more than three metal- metal bonds, and in many cases, the electrons of the bonds are highly delocalized over the metal framework Simpler and perhaps more definite metal- metal bonds... C(1)-Ag(1)-P(6) 120 .95(1) C(1)-C (2) 1 .20 6(8) P(1)-Ag(1)-P(6) 123 .06(5) Ag(1)-O(1) 2. 743(6) Ag (2) -O(1) 2. 817(6) Ag(3)-O(1) 3 .28 0(8) The main structural feature of the complex is a trinuclear silver core capped by one FcC≡C- and bridged by three dppm The three silver atoms and ferrocenylacetylide unit show a coordination geometry of compressed trigonal pyramidal and the averaged PAg-P and P-Ag-C angles are 124 .48(5)º... communication as the Kc (6100 20 00) of trans-[Ru(dppm )2( C≡CFc )2] is much larger than FcC≡C-C≡CFc (Kc = 70) It 22 is apparent that the ability of mediating electron delocalization varies from metal to metal (C) Metal and main group clusters as bridges Metal2 9and main group clusters3 0 were also incorporated into the linkers of mixed-valence complexes An early example features cobalt-carbonyl clusters attached with... 3 .25 27(6) Å) and they are in the range of Ag-Ag distances observed in clusters such as [Ag3(dppm)3(µ3−η1-C≡CPh )2] + (2. 866 (2) – 2. 9983(1) Å)35b and [Ag3(dppm)3(C≡C-C6H4-NO2-p) ]2+ (2. 9850(6) – 3.4030(6) Å).35a The three Ag-Ag vectors are shorter than the sum of van der Waal’s radii of two Ag atoms (~ 3.4 Å), suggesting that metal- metal interaction is possible One of the CF3SO3 anions is disordered and. .. system with σ metal- meta bond as the bridge Among many metal- metal bonds, the Pt(I)-Pt(I) σ-bond was chosen in this study partly because of the known chemistry of Pt(I)-Pt(I) to undergo addition reactions with d10 metal fragments such as HgCl2 and AuCl to form A-frame trinuclear Pt2Hg and Pt2Au clusters This would provide a way to change the electronic structures of the metal- metal bond and to observe . Re(I) and Ru(II) complexes of polyynes of 2- 8 carbon atoms have been successfully synthesized (Figure 1.8). 25 19 Fe Ph 2 P PPh 2 Fe PPh 2 Ph 2 P Fe Ph 2 P PPh 2 Fe PPh 2 Ph 2 P . trans-[Ru(dppm) 2 (C≡CFc) 2 ] was independently shown by Long 27 a and Wolf 27 b-c to be a Class II MV species (Kc = 6100 20 00). Detailed electrochemical and spectroscopic studies on the complex and its derivatives. 18 N N N N N N N N N N N N n 10 5 15 7 5 320 0 379 24 2 177 23 a 23 a 23 a 23 a Ru Ru N N N N N N K c H AB /cm -1 ref Ru N N N Ru N N N 4+ 4+ K c H AB /cm -1 ref n=0 n=1 n =2 Figure 1.7 Some examples of polyaromatics