The magnetic and Mossbauer spectral properties of hydrated and anhydrous complex salts [Fe( bpp )2] X2, where bpp = [2,6-bis(pyrazol-3-yl)pyridine] and X = PF6, BF4, Br, I, NO3, are indicative of a temperature-induced singlet (1A1) ↔ quintet (5T2) transition in the complex cation. The nature of the transition depends on the anion and the degree of hydration. The transition is displaced to lower temperatures in the anhydrous species and for the hydrated is only partial above room temperature. The transition in the hydrated hexafluorophosphate salt occurs in two steps, and that in the anhydrous hexafluorophosphate is incomplete, a high residual fraction of quintet state species being retained below the transition temperature. For the anhydrous complexes the transition is discontinuous and that in the complex iodide is associated with a narrow thermal hysteresis with transition temperatures Tc ↓ = 203 K and Tc ↑ = 205 K. The structures of [Fe( bpp )2]I2.4H2O and [Fe( bpp )2][BF4]2.3H2O have been determined at 298 K. Both complex salts are essentially low spin at this temperature and have an average Fe-N distance of 1.95 Ǻ. The structures reveal in both instances an extended hydrogen-bonded network involving the uncoordinated >NH groups of the ligands, the anions and lattice water. It is suggested that it is this bonding which is responsible for the favouring of the singlet state in the hydrated salts. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) diiodide tetrahydrate : triclinic, space group Pī , a 8.276(8), b 8.305(7), c 21.941(27) Ǻ, α 98.11(5), β 90.08(6), γ 90.82(6)°, Z 2. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) bis ( tetrafluoroborate ) trihydrate : monoclinic, space group C2/c, a 31.222(15), b 14.456(3), c 12.907(5) Ǻ, β 99.40(2)°, Z 8.

An investigation has been made of the chemical and mineralogical transformations which have accompanied the weathering of six basic volcanic rocks from eastern New South Wales. Montmorillonite is initially formed from the destruction of the olivine, pyroxene, and plagioclase in the parent rock, but, in the near-surface horizons, this mineral is unstable and may form kaolinite, halloysite, or a poorly crystalline montmorillonite. The alumina content shows a steady increase up the profiles, whereas the alkalis, alkaline earths, and some of the silica have been lost in the ground-waters during the mineral transformations. Marked concentrations of iron and titanium occur at specific levels in some of the weathering profiles and explanations of these phenomena are given.

The reaction of C6H5P(S)(NMe2)2 (2) with BuLi in diethyl ether/hexane mixture gives the ortho-metallated species o-LiC6H4P(S)(NMe2)2 (3), which has been characterized by 31P and 13C n.m.r . spectroscopy, and by preparation of the derivatives R{o-C6H4P(S)(NMe2)2}n (where R = Me3Si or Ph2P, n = 1; R = PhP , n = 2; R = P, n = 3). A single-crystal X-ray structure determination of one derivative, phosphinetriyltris (N,N,N′,N′- tetramethyl-o-phenylenephosphonothioic diamide ), P{o-C6H4P(S)(NMe2)2}3 (6), is reported.

The crystal structure of Pb(SC6Hs)2 is pseudo-C-centred orthorhombic, a = 54.06(1), b = 11.468 (1), c = 7.4387(8)A,, ~ = [3 = "7 = 90 ° , Z = 16, and may be described as a partial ordering of a 1:1 disordered parent structure of symmetry Pmcn, Z = 4 (a t = a/2, b t = b/2, c ~ = c), in which the mirror imposes a 1:1 disorder on two-dimensionally polymeric layers perpendicular to a*. An ideally ordered structure has monoclinic space group Cll2t/d (P21/c using an alternative axis system b, c, [a + b]/2), but may also be described as two inversion-related substructures of Cmc2~ pseudosymmetry, where the b-glide planes of one substructure coincide with the mirror planes of the other and vice versa. Moving one substructure by b/2 relative to the other creates a different orientation of the structure. The crystal studied showed a partial disorder of each substructure relative to origins b/2 apart [0.964 (4):0.036 for one substructure and 0.584 (3):0.416 for the other].This lowers the symmetry of the average structure to C1121 with intensities realistically described as K2[(1 -15)lF(hkl)l 2 + blF(hkl)12], where K 2 for h odd, k odd reflections is 0.444 (7) of the value for h even, k even reflections, 6 is 0.325 (5) and F(hkl) is the structure factor for an ideally ordered structure. Final values for R of 0.046 and 0.090 were obtained for the 844 h even, k even and 687 h odd, k odd reflections with l(h) > 3cr(l(h)) used in refinement. A bond-valence interpretation of the bonding within the polymeric layer structure is given.

Iron(II) and nickel(II) bis ( ligand ) complexes of 2,6-bis(1,2,4-triazol-3-yl)pyridine and the substituted derivatives 2,6-bis(1(N)-methyl-1,2,4-triazol-3-yl)pyridine 2,6-bis(5-methyl-1,2,4-triazol-3-yl)pyridine and 2,6-bis(1,5-dimethyl-1,2,4-triazol-3-yl)pyridine have been prepared. Coordination of the unsubstituted ligand through N4 of the triazolyl moieties is confirmed by structure determination of [FeL2][NO3]2.4H2O and [NiL2]Cl2.3H2O. In both of these complex salts there is an extensive hydrogen-bonded network involving the N 1-H group, the anions and the water molecules. Bis [2,6-bis(1,2,4-triazol-3-yl)pyridine]nickel(II) dichloride trihydrate : monoclinic, space group C2/c, a 17.971(5), b 11.433(1), c 14.849(5) Ǻ, β 122.20(1)°, Z 4. Bis [2,6-bis(1,2,4-triazol-3-yl)pyridine]iron(II) dinitrate tetrahydrate : tetragonal, space group 141/a, a 11.488(2), c 21.055(7) Ǻ, Z 4. [FeL2]Cl2.3H2O is isostructural with the nickel complex and is high-spin but undergoes a partial transition to low-spin at low temperature. Conversion to low-spin is complete when the complex is dehydrated, and this change is associated with the effects of the hydrogen bonding. The solid iron complexes of the N-methyl-substituted ligands in which the hydrogen-bonding potential is reduced are entirely high-spin down to 77K. The complex of the 5-methyl derivative undergoes a continuous singlet ↔ quintet transition below room temperature.