Studies in Werner clathrates. II. Structure and thermal analysis of bis(isothiocyanato)tetrakis(4-phenylpyridine)nickel(II) benzene clathrate (1:4)

C46H36N6NiS2.4C6H6, M r= 1107.7, triclinic, Pl , a = 9.52 (1), b = 12.19 (3), c = 13.72 (2) A, ix= 100.3 (1), f l = 9 0 . 3 (1), y = 105-9 (2) °, V = 1504.0]k 3, Z = 1, host:guest= 1:4, Dm = 1.235, D x = 1.22 gcm -3, 2(Mo Ktx) = 0.7107 A, g = 3.95 cm -l, F(000) = 582, T = 294 K, R = 0.097 (wR = 0.078) for 3782 observed reflections. The host molecule has a + + configuration and guest molecules are contained in a large channel parallel to a which has been mapped by volume calculations. Thermal decomposi* Part 10: Nassimbeni, Niven & Taylor (1988a). To whom correspondence should be addressed. 0108-2701/89/040591-05503.00 tion studies indicate release of guest molecules at ca 307 K. Introduction. Werner clathrates are complexes of the type MX2L4 where M=diva len t transition-metal cation, e.g. Mn2+-Cu 2+, X = anionic ligand e.g. halide, NCS-, NO2, NCO-, and L =electrically neutral substituted pyridine or a-arylalkylamine. Since the pioneering work in the 1950's (Schaeffer, Dorsey, Skinner & Christian, 1957) these compounds have been used to separate a wide variety of isomeric and other organic compounds. The 4-methylpyridine (4-Mepy) derivative of the bis(isothiocyanato)nickel(II) complex © 1989 International Union of Crystallography 592 C46H36N6NiS2.4C6H 6 entraps a wide variety of guest molecules in cavities of the channel, layer and cage types, and its physicochemical properties have recently been reviewed (Lipkowski, 1984). We have studied the effect of varying the substituent on the base on the clathrating ability of the complex. The host complexes studied so far have been of the type [Ni(NCS)2(4-Rpy)4] where R = ethyl (Moore, Nassimbeni & Niven, 1987a), vinyl (Moore, Nassimbeni, Niven & Taylor, 1986) and phenyl (Nassimbeni, Papanicolaou & Moore, 1986; Nassimbeni, Niven & Taylor, 1987, 1988a, 1988b). We report here the structure of another 4-phenylpyridine derivative with benzene as the guest molecule and describe the physical environment of the guest with relation to its thermal decomposition. Experimental. The host powder of [Ni(NCS)2(4Phpy)4] was prepared by treating an aqueous solution of nickel(II) isothiocyanate with a stoichiometric quantity of 4-phenylpyridine dissolved in a minimum of methanol. The clathrate was formed by dissolving the dried precipitate in benzene until saturated, then centrifuging to produce a clear blue solution. Slow evaporation at room temperature gave blue rectangular lath-shaped crystals after 72 h. Crystal density was determined by flotation in water/saturated KI solution. Approximate cell parameters and space-group symmetry were determined photographically. A suitable crystal for data collection had to be mounted in a Lindemann-glass capillary with mother liquor, to prevent deterioration in the atmosphere by desorption of the guest solvent. Crystal mounting proved difficult because the crystals had the unusual ability to move in the capillary even after being firmly wedged. Mounting was eventually achieved by introducing glass fibres on both sides of the crystal (dimensions 0.46 x 0-59 x 0.46 mm), adding mother liquor, and sealing with a flame. Although this method of mounting prevented gross movement, there was continual recentring (10 times) throughout the data collection (total exposure time was 34.6 h). Data collection: Nonius CAD-4 diffractometer, graphite-monochromated Mo Ks radiation. 25 reflections (16 < {9< 17 °) for measurement of the lattice parameters at 294 K. 09--2{9 scan technique, scan width Ato = (1-0 + 0.35tan{9) °, {9 scan range 1-20 °, final acceptance limit 20o at 20 ° min -~ in 09 and maximum recording time of 30s. No absorption correction applied owing to severe 'decay'. Centring checked every 100 measured reflections whilst intensities of three standard reflections (229, 239, 1,1,10) monitored every hour indicated loss of intensity of 55% during the data collection. Intensities corree all H atoms geometrically positioned with a single common temperature factor. Two independent guest molecules located in general positions, no H atoms on guest molecules and all guest C atoms were assigned a common isotropic temperature factor. 289 parameters refined, R =0 .097 , wR =0 .078 with w = [tr2Fo I-l, S = 8.18, max. A/a = 0.014, zip within +0.62 to -0 .71 e A -3. Complex neutral-atom scattering factors for non-H atoms from Cromer & Mann (1968) and for H atoms from Stewart, Davidson & Simpson (1965). Molecular parameters obtained from PARST (Nardelli, 1983), drawings from PLUTO (Motherwell, 1974), space-filling drawings from A L C H E M Y (Tripos Associates, Inc., 1987) and volume calculations with OPEC (Gavezzotti, 1983). L. LAVELLE, L. R. NASSIMBENI, M. L. NIVEN A N D M. W. T A Y L O R 593 Table 2. Selected bond lengths (A) and bond angles (o) with e.s.d. ' s in parentheses for C46H36N6NiS2.4C 6H6 Ni(I)---N(I) 2-049 (9) N(I I)-Ni(I)-N(21) 91-8 (5) Ni(I)-N(I I) 2-176(10) N(I)--Ni(I)-N(21) 90.3(5) Ni( I)-N(2 I) 2-, 14 (9) N(I)-Ni(I)-N( I ,) 89-6 (6) N(I)-C(1) 1.168 ( 1 3 ) Ni(l)-N(I)-C(I) 173.0 (ll) C(I)-S(l) i.626 (ll) N(i)-C(I)-S(I) 177.8(13) C(14)-C(I I 1) 1-536 (14) C(24)-C(211) 1.46, (17) Thermograms were carried out on a S tantonRedcroft thermal analyser, operating at a uniform heating rate of 10 K min ' (range 313 to 673 K ) w i t h nitrogen (60 ml min -I) passed over samples. Crystals were removed from solution, dried by patting and weighed quickly before analysis. Platinum containers (alumina used as reference) located directly on the thermocouple so furnace temperature only measured. Lag between this and sample temperature calculated using 6 standards in the range 373 to 573 K. Enthalpy values calculated by comparison of DTA peak areas with a standard (naphthalene) of known AH value. Cl14