Supporting Information

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1 Supporting Information The Heptacyanotungstate(IV) Anion: A New 5 d Transition-Metal Member of the Rare Heptacyanometallate Family of Anions Francisco J. Birk, Dawid Pinkowicz, and Kim R. Dunbar* anie_ _sm_miscellaneous_information.pdf

2 Table of Contents: 1. Experimental Procedure 2. Table S1. Crystal and structural refinement data for 1 and [Co III (Cp)2]4[W IV (CN)8]. xch3cn. 3. Table S2. Bond lengths [Ǻ] and angles [ ] for Figure S1. Thermal ellipsoid plot and labeling scheme for 1 (a) and [Co III (Cp)2]4[W IV (CN)8]. xch3cn (b). 5. Figure S2. Infrared spectra for 1 in the solid state and dichloromethane solution. 6. Figure S3. UV-vis spectra for 1 in acetonitrile solution. 7. Figure S4. χmt vs T and M vs T for 1 with simultaneous fitting of both dependencies. 8. Figure S5. Reduced magnetization of References 1

3 1. Experimental Procedure All reactions were carried out under air-free conditions using standard Schlenk-line and glovebox techniques. (n-bu4n)3[w(cn)8] was prepared according to the literature method. 1 Cobaltocene was purchased from Strem and used as received. Acetonitrile was dried over 3Å sieves and distilled under N2. Diethyl ether was activated over alumina column on an MBraun solvent system and stored over 4Å sieves in the drybox. Elemental analysis was performed by Atlantic Microlabs, Inc., Norcross, GA. IR spectra were recorded on a Nicolet in10 FT-IR microscope. IR spectra for a single crystal of 1 were recorded in a Linkam thermostat sealed under Ar atmosphere to prevent decomposition. IR spectra in solution were measured for a thin film of an anhydrous, oxygen-free dichloromethane solution of 1 placed between two polished single crystal KBr windows. Electronic absorption spectra 1 in acetonitrile were measured using a Perkin Elmer Lambda 35 double beam spectrophotometer in sealed quartz cuvettes. Magnetic measurements were performed on a Quantum Design MPMS-XL SQUID magnetometer equipped with a 7T superconducting magnet in the temperature range 1.8 to 300 K. The diamagnetic contribution of the plastic bag used as a sample holder was subtracted from the raw data; core diamagnetism of the sample was corrected for using Pascal s constants. 2 Synthesis of (n-bu4n)3[w(cn)7] (1), A reaction vial was charged with g (2.02 mmol) of (n-bu4n)3[w(cn)8] and g (2.03 mmol) of Cp2Co. Addition of 10 ml of CH3CN with stirring resulted in the formation of a yellow-green solution along with a green solid precipitating. After stirring overnight, the reaction was filtered to remove the green solid, and the yellow-green filtrate was transferred to a large vial; addition of Et2O precipitated the remaining green by-product identified as the cobaltocenium(iii) octacyanotungstate(iv) acetonitrile solvate: [Co III (Cp)2]4[W IV (CN)8]. xch3cn. This solution was then filtered to yield a yellow filtrate and subjected to a slow diffusion of Et2O. The resulting colorless (slightly yellowish) crystals were then collected via filtration and washed with Et2O. Yield: g (55%). Elemental for calculated C55N10H108W1: C, 60.42; H, 9.96; N, Found: C, 60.21; H, 10.03; N, X-ray Crystallographic Measurements A colorless single crystal of 1 was mounted on a nylon loop using Paratone oil and placed in the N2 cold stream at 110 K. The data were collected on a Bruker APEX II diffractometer (MoKα radiation λ = Ǻ) equipped with a CCD detector. The data sets were recorded as four ω-scans and integrated using the Bruker APEXII software package. 3 The multi-scan absorption correction was done within the Bruker APEXII software using SADABS (v2014/5). Solution and refinement of the crystal structures were carried out using SHELXT 4 and shelxle (a graphical interface for the SHELX suite of programs), respectively. 5 Structure solution by direct methods resolved positions of all W atoms and most of the C and N atoms. The remaining non-hydrogen atoms were located by alternating cycles of least-squares refinements and difference Fourier maps. One of the n-butyl groups of a tetrabutyl ammonium cation was refined as disordered in two positions using PART instruction. Hydrogen atoms were placed at calculated positions. The final refinements were performed with anisotropic thermal parameters for all non-hydrogen 2

4 atoms. A summary of pertinent information relating to unit cell parameters, data collection, and refinement is provided in Tables S1. Selected metal ligand bond distances and angles are provided in Table S2. The corresponidng crystallographic information file was deposited with the Cambridge Structural Database: CCDC A green crystal of the by-product that forms during the synthesis of 1 was mounted using paraffin oil on a cryo-loop and placed in a N2 cold stream at 120 K. The data were collected on a Bruker D8 Quest Eco diffractometer (MoKα radiation λ = Ǻ) equipped with a Photon50 CMOS detector. The data sets were recorded as four ω-scans and integrated using the Bruker APEX3 software package.the multi-scan absorption correction was performed within the Bruker APEX3 software using SADABS (v2015/10). Solution and refinement of the crystal structures were carried out using SHELXT 4 and shelxle (a graphical interface for the SHELX suite of programs), respectively. Structure solution by direct methods resolved the positions of all W atoms and most of the C and N atoms. The remaining non-hydrogen atoms were located by alternating cycles of leastsquares refinements and difference Fourier maps. The final refinements were performed with anisotropic thermal parameters for all non-hydrogen atoms. A summary of pertinent information relating to unit cell parameters, data collection, and refinement is provided in Tables S1 and the asymmetric unit is shown in Figure S1b. The corresponidng crystallographic information file was deposited with the Cambridge Structural Database: CCDC

5 Table S1. Crystal and structural refinement data for 1 and [Co III Cp)2]4[W IV (CN)8]. xch3cn. 1 [Co III (Cp)2]4[W IV (CN)8]. xch3cn Formula W1N10C55H108 W2N19C100Co8H80 Molecular Weight Temp (K) Crystal System Monoclinic Triclinic Space Group P21/c P-1 a (Ǻ) (16) (16) b (Ǻ) (16) (16) c (Ǻ) (16) (2) α ( ) (3) β ( ) (9) (3) γ ( ) (3) V (Ǻ 3 ) 12159(15) (5) Z 8 1 Color colorless Green ρcalc (g/cm 3 ) μ (mm -1 ) θ range ( ) to to Reflections collected Unique reflections Parameters/restraints 1234, , 4 R1, a wr2 b [I > 2σ(I)] , , R1, a wr2 b (all data) , , Goodness-of-fit c (F 2 ) Largest diff. peak, hole (e Ǻ -3 ) 2.42, , a R = Σ Fo - Fc / Σ Fo. b wr = {Σ [w(fo 2 Fc 2 ) 2 ]/ Σ[w(Fo 2 )] 2 } 1/2. c Goodness-of-fit = {Σ [w(fo 2 Fc 2 ) 2 ]/(n-p)} 1/2, where n is the number of reflections and p is the total number of parameters refined. 4

6 Table S2. Select bond lengths [Ǻ] and angles [ ] for 1. W1 C (4) W1 C (4) W1 C (4) W1 C (4) W1 C (4) W1 C (4) W1 C (4) N1 C (5) N2 C (5) N3 C (5) N4 C (5) N5 C (5) N6 C (5) N7 C (5) C2 W1 C (15) C2 W1 C (16) C2 W1 C (16) C2 W1 C (16) C3 W1 C (15) C3 W1 C (15) C3 W1 C (15) C3 W1 C (15) C3 W1 C (14) C4 W1 C (15) C4 W1 C (16) C4 W1 C (14) C5 W1 C (15) C5 W1 C (15) C5 W1 C (14) C5 W1 C (15) C5 W1 C (15) C5 W1 C (14) C6 W1 C (16) C6 W1 C (15) C7 W1 C (14) N1 C1 W (4) N2 C2 W (4) N3 C3 W (3) N4 C4 W (4) N5 C5 W (4) N6 C6 W (4) N7 C7 W (4) 5

7 Figure S1. Thermal ellipsoid plot and labeling scheme for 1 (a) and [Co III (Cp)2]4[W IV (CN)8]. xch3cn (b). a) the asymmetric unit of 1 with atom labelling scheme for the anions is shown below. Thermal ellipsoids are drawn at the 50% probability level b) the asymmetric unit of [Co III (Cp)2]4[W IV (CN)8]. xch3cn with atom labelling scheme for the metal centers is shown below. Thermal ellipsoids are drawn at the 30% probability level 6

8 Figure S2. (a) infrared spectra for 1 in the solid state (red) and dichloromethane solution (blue) and (b) the spectra collected during the decomposition of a single crystal of 1 in air. 7

9 Figure S3. Electronic spectra for 1 in acetonitrile solutions (for details see text). Black solid lines correspond to the solutions prepared using anhydrous and oxygen-free MeCN and dotted lines corresponds to solutions exposed to air (leading to decomposition of 1). 8

10 Figure S4. χmt vs T (main, HDC = 0.1 T) (a) and M vs. H at 1.8 K (b) for 1. Solid lines are the best fit to both sets of simultaneously. 9

11 Figure S5. Reduced magnetization (M vs. HT -1 ) plot for 1 measured at 1, 2, 3, 4 and 5 T (violet to red points) between 1.8 and 20 K. Solid lines are the best fit using the following parameters: g = 2.0(1), D = 430(10) cm -1 and E = 40(5) cm -1 References 1. Bok, L. D. C.; Leipoldt, J. G.; Basson, S. S., Zeitschrift für anorganische und allgemeine Chemie 1975, 415, Bain, G. A.; Berry, J. F., Journal of Chemical Education 2008, 85, AXS, B. Madison, WI, Sheldrick, G., Acta Crystallographica Section A 2008, 64, Hubschle, C. B.; Sheldrick, G. M.; Dittrich, B., Journal of Applied Crystallography 2011, 44,