21 New compounds and structures William T. A. Harrison Department of Chemistry, University of Aberdeen, Aberdeen, UK AB24 3UE. E-mail: w.harrison@abdn.ac.uk 1 Introduction Synthetic and structural solid state chemistry is one of the most thriving and varied areas of the subject. Any survey that attempted to be fully comprehensive would be impossibly unwieldy. Therefore, this review attempts to provide an overview of some of the most significant developments reported in 1998.As in previous years, it focuses largely on new structure types containing extended inorganic lattices. 2 Oxides Many new vanadium oxide phases have been prepared by a variety of synthesis methods. A new polymorph of VO 2 , designated VO 2 (C), containing sheets of vertexsharing VO 5 square pyramids was prepared from VO 2 ·0.5H 2 O by chimie douce methods.1 Two vanadium oxide phases, BaV 7 O 16 ·nH 2 O,2 and Zn 2 (OH)VO 4 ,3 have been prepared by combined hydrothermal/electrochemical methods as single crystals.The former phase contains both VO 4 tetrahedra and distorted VO 6 octahedra and an average vanadium oxidation state of 4.29. The latter contains tetrahedral VV in a new superstructure modification of the adamite [Zn 2 (OH)AsO 4 ] structure type.Cr 0.11 V 2 O 5.16 4 has been prepared by a sol–gel process and has a structure (with ordered Cr and V) related to that of orthorhombic V 2 O 5 . Hydrothermally prepared SrV 12 O 27 ·3H 2 O (average V oxidation state\4.33) contains VO 6 octahedra andVO 5 square pyramids enclosing wide tunnels occupied by Sr2` cations and H 2 O molecules. 5 Fe 2 V 4 O 13 ,6 prepared by cooling from the melt, contains edge-sharing Fe 2 O 10 octahedral dimers and U-shaped [V 4 O 13 ]6~ clusters.A surprising double substitution mechanism (MoVI for VV accompanied by a stoichiometric quantity of additionalO2~ ions) results in the formation of Fe 2 V 3.16 Mo 0.84 O 13.42 . The isostructural FeVMoO 7 and CrVMoO 7 contain7 very unusual[VMoO 7 ]3~ ions.Single crystal studies showed perfect ordering of the VV and MoVI cations and the presence of an isolated Mo––O bond. a-CoV 3 O 8 contains8 VIV and VV and is antiferromagnetic below 8K. Ceramic methods were used to synthesise BiCa 2 VO 6 9 and BiCu 2 VO 6 10 (Fig. 1) which both Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 409Fig. 1 Structure of BiCu 2 VO 6 as VO 4 tetrahedra and BiO 2 chains. Open circles are Cu atoms. (Reproduced by permission from J. Solid State Chem., 1998, 141, 149.) contain [BiO 2 ]~ chains and [VO 4 ]3~ tetrahedra. However, the di§erent coordination preferences for calcium (irregular seven-fold) and copper (square pyramidal]distorted octahedral) lead to quite distinct structures.BiCa 2 VO 6 (space group Cmc2 1 ) may be ferroelectric. A soft chemical route e§ected the conversion of (NC 7 H 14 ) 4 ·H 2 V 10 O 28 to the lamellar (NC 7 H 14 )·V 4 O 10 ,11 which contains disordered VIV and VV on one square-pyramidal site. Hydrothermally prepared (N 2 C 4 H 12 )·V 4 O 9 12 is also layered and contains a new topology of edge-sharingVIVO 5 square pyramids. La 3 Co 3 O 8 has a structure ‘intermediate’ between perovskite and brownmillerite.13 It contains vertex-linked CoO 6 octahedra and CoO 4 tetrahedra, and orders antiferromagnetically at temperatures below 35 K.La 4 Co 3 O 9 is related to three-layer Ruddlesden –Popper phases, but contains an octahedral/tetrahedral/octahedral layer motif. It may be structurally derived from La 4 Co 3 O 10 by ordering of oxygen vacancies and is antiferromagnetic below 305 K.14 La 2 Ti 2 O 7 ,15 prepared by topotactic dehydration of HLaTiO 4 , possesses a defective two-layer Ruddlesden–Popper structure. Careful synthetic work has resulted in several layered titanates: Na 2~x`yCax@2 La 2 Ti 3 O 10 is a triple-layered phase with unusual electrical properties.16 BaLa 4 Ti 4 O 15 contains17 perovskite-like blocks four TiO 6 octahedra thick.It is the n\5 member of the series (Ba,La)nTin~1 O 3n and shows Ba/La ordering over the 12-fold coordinated sites. Ba 5 Fe 4 Ti 10 O 31 exhibits18 a complex 18-layer hexagonal structure. The octahedral cation sites contain a mixture of FeIII and TiIV, the tetrahedral sites only FeIII. A much simpler phase is NaTiO 2 , which shows19 a symmetry change from trigonal to monoclinic and associated magnetic anomalies on cooling which may be correlated with an increase in the Ti–Ti bonding. 15R SrMn 1~xFexO 3~x (x[0.1) (Fig. 2) crystallises20 in a new 15-layer hexagonal perovskite stacking sequence denoted (cchch) 3 . Face-, edgeand corner-sharing occurs for the octahedral sites. Neutron di§raction measurements showed that the MnIV cations order ferromagnetically (T N \220 K), whilst the FeIII cations remain magnetically disordered at 3K.A new series of cuprates, [M 2 Cu 2 O 3 ]m[CuO 2 ]n (m\n\1), whereMis an alkaline earth or trivalent metal have been reported,21 some of which show a T#[85K Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 410Fig. 2 15R crystal structure of SrMn 1~xFexO 3~x: circles represent Sr2` cations, octahedra represent (Mn,Fe)O 6 units.The three transition metal sites are labelled. (Reproduced by permission from Inorg. Chem., 1998, 37, 6071.) superconducting transition. Their structures were interpreted in terms of ‘the commensurate version of two fragments due to the reconstruction of the Cu–O ribbons.’ Nd 4 Cu 2 O 7 is an unusual coppper(I) oxide containing two- and four-coordinate copper sites which may be viewed as a cooperatively distorted T@-type [Nd 2 CuO 4 ] structure. 22 Tl(Sr 1.4 La 2.6 )Ni 2 O 9 is a direct23 nickel-containing analogue of the superconducting cuprate Tl(Ba 2~xLa 2`x)Cu 2 O 9 .The structure of Mn 3 Ta 2 O 8 was determined24 ab initio from synchrotron and electron di§raction data and is a complex tetragonal I5]I5]2 fluorite superstructure.SrMnTeO 6 is characterised25 by staggered (Mn,Te) 6 O 18 Kagome� layers along [001] and SrO 6 hexagonal prisms. The ‘condensed’ silicates Fe 4 Si 2 Sn 7 O 16 26 and Cs 4 CuSi 2 O 7 27 were prepared by solid state methods. Structural, Mo� ssbauer and susceptibility measurements indicated that the former phase contains mixed-valent tin (SnII, SnIV).The latter phase contains square planar CuIIO 4 and Si 2 O 7 groups incorporated into CuSi 2 O 7 ribbons. The hexagonal A 4 A@Ir 2 O 9 (A\Sr, Ba; A@\Cu, Zn) family of phases28 are very sensitive to preparation conditions, and may crystallise in commensurate or incommensurate modifications depending on thermal treatment, but their magnetic properties appear to be unchanged. The related Sr 6 Rh 5 O 15 contains29 infinite face-sharing Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 411Fig. 3 Arrangement of the four di§erent Mo clusters within the hexagonal unit cell in Pr 4 Mo 9 O 18 . (Reproduced by permission from Inorg. Chem., 1998, 37, 6229.) columns built up from four RhIV octahedra interspersed by RhII trigonal prisms.Sr 3 MRhO 6 (M\Y, Sc, In)30 are isostructural with K 4 CdCl 6 and contain infinite chains of alternating RhO 6 octahedra and MO 6 trigonal prisms. The reaction of ammonia and ammonium heptamolybdate has led31 to two polymorphs of the simple molybdate (NH 4 ) 2 MoO 4 , which di§er in their hydrogen bond topologies. The layered molybdate (C 2 H 10 N 2 )[Mo 4 O 12 ] was prepared32 hydrothermally and contains a two-dimensional network of MoV- and MoIV-centred octahedra sandwiching ethylenediammonium cations.Several reduced-molybdenum containing phases containing complex clusters have been prepared. The semiconducting (E! \0.12 eV) phasesM 4 M@3 Mo 26 O 48 (M\Sr, Eu;M@\Al, Ga)33 are built up from Mo 7 groups and infinite Mo 7 –Mo 10 –Mo 7 chains. Pr 4 Mo 9 O 18 is an extremely complex phase (Fig. 3) containing Mo 3 , Mo 7 , Mo 13 and Mo 19 clusters.34 The Mo 7 cluster is planar and the Mo 13 and Mo 19 groupings are hemispherical and spherical, respect- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 412ively. A detailed structural study35 aMo 2 O 5 by neutron di§raction and EXAFS measurements revealed the presence of disordered Mo 3 and Mo 6 clusters.Cu 2 Th 4 (MoVIO 4 ) 9 is cubic,36 with a three-dimensional network of ThO 9 and MoO 4 polyhedra delimiting cages occupied by the CuI species. Bi 3 NbO 7 is an oxygendeficient fluorite37 with promising ionic conduction properties up to 875 °C. Tl 8 Nb 27.2 O 72 is related to hexagonal bronzes.38 Pr 2 Nb 11 O 30 was prepared39 by chemical vapour transport methods and contains both six- and seven-coordinated niobium atoms.Se 4 Nb 2 O 13 [or (NbO) 2 (SeO 3 ) 2 (Se 2 O 5 )] is a new non-centrosymmetric phase40 containing SeO 3 and Se 2 O 5 moieties in combination with NbO 6 octahedra. Despite the presence of the asymmetric NbV and SeIV species, the non-linear optical response of this phase is very low. The metallic SbRe 2 O 6 contains41 slabs built up from pairs of ReO 6 octahedra sharing edges [d(Re · · · Re)\2.52Å] interspersed by the antimony species. Pb 6 Re 6 O 19 contains similar Re 2 O 10 groups and is also metallic. 42 A new metastable modification of bismuth oxide, Bi 2 O 3 , has been synthesised at high pressure and temperature.43 It is isostructural with a-La 2 O 3 and slowly transforms to other modifications of Bi 2 O 3 under ambient conditions.K 4 Bi 2 O 5 contains44 isolated [Bi 4 O 10 ]8~ groupings with BiIII showing both pyramidal and see-saw (SF 4 like) coordinations.Ba 2 BiGa 11 O 20 is structurally related to Ba 3 TiAl 10 O 20 but is complicated by disorder of the barium and bismuth cations which may be rationalised in terms of the stereochemically active lone pair of the latter species.45 Pb 2 TeO 5 contains46 isolated chains of distorted TeO 6 octahedra crosslinked by PbO 7 groups.a-Tl 2 Te 2 O 5 shows47 the structural e§ect of the stereochemical activity of both the thallium(I) and tellerium(IV) lone pairs and has strong two dimensional character. Ab initio powder methods were used to solve the hexagonal structure of the technologically important cement phase erroneously described as CaAl 2 O 4 ·10H 2 O (‘CAH 10 ’) which has been implicated in building collapses as a hydration product of CaAl 2 O 4 , the main phase of high alumina cement.48 The actual stoichiometry is better described by the formula CaAl 2 (OH) 8 (H 2 O) 2 ·1.84H 2 O.SrCe 2 O 4 is the first new inorganic structure to result from a combinatorial approach to solid state synthesis.49 Weinberg and co-workers49 reported the preparation and structural characterisation of this new material by ab initio powder methods.Initially, the putative SrCe 2 O 4 was selected from a ‘discovery library’ of some 25 000 chemical compositions on the basis of its photoluminescence properties. The structure contains linear chains of edgesharing CeIVO 6 octahedra. 3 Zeolites and molecular sieves It has been an exceptional year for the synthesis and characterisation of new zeolite structures. The chabazite modification50 of SiO 2 has the lowest framework density of any pure silica polymorph. Microcrystalline single crystal di§raction methods revealed that \[(C 13 H 24 N) 4.1 F 3.3 (OH) 0.8 (H 2 O) 1.6 ][SiO 2 ] 64 , denoted SSZ-23, contains very unusual seven- and nine-membered-ring pore openings.51 Similar methods showed that the borosilicate phase SSZ-42 contains undulating, one-dimensional 12-ring channels.52 It is thermally stable to at least 800 °C.The aluminosilicate framework of the remarkable blue volcanic mineral zeolite, tscho� rtnerite, Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 413Fig. 4 A unique 3-connected two-dimensional sheet in (CH 3 NH 3 ) 2 Ga 2 Ge 3 O 10 .The five T-atom unit surrounded by three 3-ring units are denoted as 4\1 units. The bridging atoms are omitted for clarity. (Reproduced by permission from J. Am. Chem. Soc., 1998, 120, 11 204.) \Ca 4 (K,Ca,Sr,Ba) 3 Cu 3 (OH) 8 [Si 12 Al 12 O 48 ]·xH 2 O (xq20), contains53 an enormous, new, 96-membered (tscho� rtnerite) cage, as well as double-six-rings, doubleeight- rings, sodalite cages and truncated cuboctahedra.Complex Cu–Ca–O clusters are a feature of the extra-framework content of this phase. The structure of ERS-7 (framework Si:Al ratio\25: 1), containing a new 17-sided ‘picnic-basket’ (46546582) cage was elucidated by simulated annealing (based on six independent tetrahedral atom sites in the asymmetric unit) and refined against synchrotron powder di§raction data.54 Stucky and co-workers have continued their trail blazing investigations into nonaluminium containing molecular sieves.(H 3 NCH 2 CH 2 NH 3 ) 0.5 ZnAsO 4 55 is the first amine-templated arsenate molecular sieve and crystallises in a new topology based on 4.82 sheets. [(H 3 C) 2 NH(CH 2 ) 2 NH(CH 3 ) 2 ]Co 2 Al 4 (PO 4 ) 6 56 contains two-dimensional 8-ring channels.There is a non-random distribution of cobalt and aluminium over the metal sites. No fewer than five distinct analogues of zeolite edingtonite were prepared in the aluminium–cobalt–phosphate and gallium–cobalt–phosphate systems with appropriate organic templates.57 The family of molecular sieves58 of various framework compositions (BeAsO, ZnAsO, GaGeO) denoted UCSB-7 possess two independent sets of three-dimensional crosslinked helical pores separated by a ‘gyroid periodic minimal surface.’ Perhaps the most interesting new framework composition is the gallogermanate system.The gallium: germanium ratio appears to be highly flexible, and both odd- and even-membered ring systems can be formed from the GaO 4 and GeO 4 building blocks.(CH 3 NH 3 ) 2 Ga 2 Ge 3 O 10 59 (Fig. 4) contains very unusual threemembered rings and fibrous-zeolite-like 4\1 subunits which combine to form infinite Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 414Fig. 5 Perspective view of the framework of gallophosphate Mu2 showing the two types of cage-like voids (one without OH group; the other with 8 T-OH groups); the Ga and P atoms are located at the vertices.(Reproduced by permission from Chem. Commun., 1998, 1769. 9-ring channels. (N 2 C 4 H 11 )GaGe 5 O 12 60 contains 5–1 secondary building units which assemble into a structure containing one-dimensional 10-ring channels. Other gallogermanates60 crystallise as analogues of sodalite (both cubic and triclinic variants), analcime, and known zincoarsenate frameworks.DIPYR-GaPO (Ga 7 P 6 O 28 F 3 N 2 C 10 H 16 ) contains61 14-ring channels with two amines (pyridine and 4,4@-dipyridyl) appearing to co-template this new framework. Mu2, or Ga 32 P 32 O 120 (OH) 16 F 6 ·(C 9 H 21 N 2 ) 6 ·12H 2 O,62 is a new open-framework gallofluorophosphate built up from double-four-ring subunits hosting fluoride ions in a similar manner to the situation in cloverite (Fig. 5). (NH 4 ) 2 Ge 7 O 15 contains both GeO 4 and GeO 6 polyhedra, which fuse together into a new framework containing 9-ring pores.63 4 Oxy-anions The group of Cheetham have continued their exploration of organically templated tin(II) phosphates. The polyhedral building units of the novel structures of [Sn 3 (PO 4 ) 2 (OH)]·0.5[H 3 N(CH 2 ) 6 NH 3 ] and [Sn 3 (PO 4 ) 2 (OH)]·0.5[H 3 N(CH 2 ) 8 NH 3 ] are truncated SnO 4 square pyramids, SnO 3 trigonal pyramids and PO 4 tetrahedra; Sn–O–Sn bonds result from this connectivity.64 The framework of [CN 3 H 6 ]- Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 415Fig. 6 Polyhedral views of (C 4 H 12 N 2 ) 2 [Fe 6 (HPO 4 ) 2 (PO 4 ) 6 (H 2 O) 2 ] ·H 2 O (top) and [HN(CH 2 CH 2 ) 3 NH] 3 [Fe 8 HPO 4 ) 12 (PO 4 ) 2 (H 2 O) 6 ] (bottom) emphasising the threedimensional Fe/P/O frameworks surrounding channel systems occupied by the organic species. (Reproduced by permission from Chem.Mater., 1998, 10, 2599.) [Sn 4 P 3 O 12 ] is chiral (space group P4 3 or P4 1 ) and enantiomeric crystals can be hand sorted.65 The three-dimensional [Sn 4 P 3 O 12 ]·0.5[NH 3 CH 2 CH 2 CH(NH 3 )CH 2 CH 3 ]· 2H 2 O loses water (but not template) reversibly and appears to show ion-exchange propert66 [C 2 N 2 H 10 ][Sn 2 (PO 4 ) 2 ]·H 2 O contains infinite layers of strictly alternating pyramidal SnO 3 and tetrahedral PO 4 moieties.67 The related Sn 2 (PO 4 )[C 2 O 4 ] 0.5 adopts a one-dimensional structure with respect to Sn/P/O connectivity.68 Lii et al.69 have characterised a family of organically templated iron phosphates (Fig. 6). For example, using piperazine as a template leads to at least three distinct structures: (C 4 H 12 N 2 )[Fe 4 (OH) 2 (HPO 4 ) 5 ], (C 4 H 11 N 2 ) 0.5 [Fe 3 (HPO 4 ) 2 (PO 4 )(H 2 O)] and Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 416(C 4 H 12 N 2 ) 2 [Fe 6 (HPO 4 ) 2 (PO 4 ) 6 (H 2 O) 2 ]·H 2 O.70,71 Interesting features of these phases include the presence of mixed valent iron (FeII and FeIII) and FeO 6 octahedra and FeO 5 trigonal bipyramids as polyhedral building blocks.Numerous other organically templated phosphates continue to be reported. A novel room-temperature synthesis in silica gel was used to prepare the layered phases R·M(HPO 4 ) 2 ·2H 2 O (R\C 5 NH 6 `, C 3 N 2 H 5 `; M\Al, Ga) which contain vertexsharing trans-MO 4 (H 2 O) 2 octahedra and HPO 4 tetrahedra.72 However, C 3 N 2 H 5 ·Al(HPO 4 ) 2 ·2H 2 O could also be prepared73 solvothermally at 160 °C.CN 3 H 6 ·Al(HPO 4 ) 2 ·2H 2 O 74 (prepared at 120 °C) adopts74 essentially the same structure, and may show ‘template cooperation’ in terms of infinite stacks of guanidinium cations.The layered *,*-Co(en) 3 [Al 3 P 4 O 16 ]·xH 2 O contains more typical AlO 4 tetrahedra and may be converted to the chain-like phase Co(en) 3 [AlP 2 O 8 ]·xH 2 O by hydrothermal treatment.75 The layered (CN 3 H 6 ) 2 ·(VO 2 ) 3 (PO 4 )(HPO 4 ) contains76 the hexagonal tungsten oxide motif of vertex-sharing VVO 6 octahedra capped by phosphate groups with guanidinium cations serving to pillar the sheets.Organically templated zinc phosphates may crystallise as one-dimensional [H 3 N(CH 2 ) 3 NH 3 ·Zn(HPO 4 ) 2 ],77 two-dimensional [H 3 N(CH 2 ) 3 NH 3 ·Zn 2 - (HPO 4 ) 2 (H 2 PO 4 ) 2 ],77 or three-dimensional [H 3 NCH 2 CH 2 NH 3 ·Zn 6 (PO 4 ) 4 - (HPO 4 )(H 2 O)]78 structures in terms of Zn/P/O connectivity.However, the lack of any e§ective control or predictability of such syntheses remains a serious shortcoming of such methods. The first layered, organically templated uranium(VI) phosphates,79 NH(CH 2 CH 3 ) 3 ·(UO 2 ) 2 (PO 4 )(HPO 4 ) and N(CH 2 CH 2 CH 3 ) 4 ·(UO 2 ) 3 (PO 4 )(HPO 4 ) 2 , contain sheets of edge-sharing UO 7 pentagonal pyramids crosslinked by PO 4 tetrahedra.The uranyl [UO 2 ]2` groupings are close to linear. (C 2 H 9 N 2 ) 6 ·Co 3 Mo 4 P 4 O 28 80 is a three-dimensional open-framework phase built up from CoO 6 , MoO 6 and PO 4 groups which surround unusual seven-membered intersecting channels. The ethylenediamine template may be removed by thermal treatment without structure collapse. Several new simple inorganic phosphates have been described.InPO 4 ·H 2 O, containing In 2 O 8 (H 2 O) 2 dimers, represents81 the ‘missing link’ between InPO 4 ·2H 2 Oand InPO 4 . NH 4 CuPO 4 ·H 2 O, which orders antiferromagnetically at very low temperatures, 82 is layered, with CuO 5 square pyramids fusing together into Cu 2 O 8 dimers, which in turn are crosslinked by phosphate groups into infinite sheets. NH 4 VOPO 4 ·H 2 O shows83 strong one-dimensional character based on double chains built up from vertex-linked VO 4 (H 2 O) square pyramids and PO 4 tetrahedra.No magnetic ordering was observed at 4K. High temperature–high pressure methods were used to prepare NH 4 Fe 2 (PO 2 ) 2 which contains84 fully ordered FeIIO 6 and FeIIIO 6 octahedra. b-LiZnPO 4 ·H 2 O85 and NaZnPO 4 -ABW86 crystallise as new modifications of the zeolite-ABW [LiAlSiO 4 ·H 2 O] tetrahedral topology with previously unobserved crystal symmetries for this structure type.Ba 3 V 2 O 3 (PO 4 ) 3 87 and Ba 2 V 5 O 8 (PO 4 ) 4 ,88 prepared by high-temperature methods, are the first mixed-valence (VIV and VV) barium vanadium phosphates. The latter phase contains three di§erent vanadium coordinations–pyramidal, octahedral and tetrahedral.The hydrothermally prepared Ba 2 (VO 2 )(PO 4 )(HPO 4 )·H 2 O is noncentrosymmetric, transparent, and contains unusual VVO 5 trigonal bipyramids, linked by phosphate groups into infinite chains.89 The new bismuth oxyphosphate, Bi 6.67 (PO 4 ) 4 O 4 , contains90 BiO 5 , BiO 6 and BiO 8 polyhedra. Substitution of bismuth Annu. Rep. Prog. Chem., Sect.A, 1999, 95, 409–429 417Fig. 7 (opposite) The structures of (a) [H 3 N(CH 2 ) 3 NH 3 ]U 2 F 10 ·2H 2 O (UFO-1), (b) [H 3 N(CH 2 ) 4 NH 3 ]U 2 F 10 ·3H 2 O (UFO-2), and (c) [H 3 N(CH 2 ) 6 NH 3 ]U 2 F 10 ·2H 2 O (UFO-3) viewed parallel to the uranium fluoride layers (along the [010] direction) showing the location of the organic template in each case. The carbon atoms are represented by dark spheres, the nitrogen atoms by lighter spheres.The occluded water molecules are excluded for clarity. In UFO-1, the [H 3 N(CH 2 ) 3 NH 3 ]2` cation lies on an inversion center and the end carbon atom is disordered around this position. For clarity, this disorder is not represented in the figure and only one orientation of the template is shown. (Reproduced by permission from Chem.Mater., 1998, 10, 3131.) by both alkali metal and alkaline earth cations is possible, leading to the Bi 6.5 A 0.5 (PO 4 ) 4 O 2 (A\Li`, Na`, K`) and Bi 6 M(PO 4 ) 4 O 4 (M\Sr2`, Cd2`, Pb2`, Ca2`) series, respectively. PbIISnIV(PO 4 ) 2 shows91 the expected stereochemical activity of the lead(II) lone pair in a new structure type related to the mineral yavapaiite [KFe(SO 4 ) 2 ].The Li 9 M 3 (P 2 O 7 ) 3 (PO 4 ) 2 (M\Al, Ga, Cr, Fe) series92 are isostructural and display lithuim ion conductivity and ion-exchange properties. Na 2 MnIIP 2 O 7 93 was prepared from a high temperature reaction and is composed of slabs of fused Mn 4 P 4 O 26 cages. Synthetic taranakite,94 K 3 Al 5 (HPO 4 ) 6 (PO 4 ) 2 ·18H 2 O, contains the longest crystallographic axis (94.98Å) of any mineral described hitherto.Slabs of composition K 3 Al 5 (HPO 4 ) 6 (PO 4 ) 2 ·12H 2 O are separated from each other by water layers. The group of Raveau have continued their exhaustive investigations of phosphates of the heavier transition metals. The MoV-containing Li 3 (MoO) 2 (PO 4 ) 3 is related to Na 3 (MoO) 2 (PO 4 ) 3 , but the modified polyhedral connectivity in the lithium phase results in di§erently shaped channels accommodating the smaller Li` cation.95 Similarly, the A 2 Mo 3 O 5 (PO 4 ) 3 (A\Cs, Rb, K, Tl) series96 adopt a three-dimensional structure in which the [Mo 3 P 3 O 17 ] 2 ~ framework is flexible in accommodating di§erently sized univalent cations.The AMoOPO 4 Cl (A\K, Rb) structure97 is strongly layered in nature, and contains sheets of vertex-sharing MoO 5 Cl octahedra and PO 4 tetrahedra, akin to the situation described below for ANbOAsO 4 Cl.Structurally, K 3 Nb 3 WO 9 (PO 4 ) 4 98 is closely related to hexagonal tungsten bronzes. However, electrons are localised in this phase despite the existence of infinite octahedral [MO 3 ] chains. ANb 4 WO 9 (PO 4 ) 3 (A\K, Rb, Cs) and related phases99 are closely related to a defective ReO 3 structure and show electronic conduction properties describable by a ‘variable, range-hopping’ mechanism.The full structures of b-Ti(PO 4 )(H 2 PO 4 )100 and s-Zr(HPO 4 ) 2 101 were determined from neutron powder data. Hydrogen bonds appear to play key structural roles in stabilising the layered structure of the titanium phase, and the three-dimensional zirconium material.Several organo zirconium fluorophosphates102 of formula R·Zr 2 (PO 4 ) 2 (HPO 4 )F·H 2 O (R\1,3-diaminopropane, etc.) crystallise with the threedimensional ‘ZrPO-1’ framework (ZrO 6 and ZrO 5 F octahedra, PO 4 tetrahedra) and show very promising zeolite-like sorption properties.103 The fluoride-rich Na 7 Mn 5 F 13 (PO 4 ) 3 (H 2 O) 3 104 contains MnF 3 O 2 (H 2 O) octahedra showing a stong, static Jahn–Teller distortion along a F–Mn–OH 2 axis and MnF 3 O 3 octahedra only showing a weak, dynamical Jahn–Teller e§ect.Na 2 BP 2 O 7 (OH)105 contains layers of BO 4 /PO 4 tetrahedra enclosing 6- and 8-rings occupied by the sodium cations. Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 418Annu. Rep. Prog.Chem., Sect. A, 1999, 95, 409–429 419Arsenates are receiving more attention. Careful synthetic work was necessary to prepare the new Zn 9 (AsO 4 ) 6 ·4H 2 O (ZnO 6 , ZnO 5 , ZnO 4 and AsO 4 polyhedra) in reasonable yield.106 Zr 3 (AsO 4 ) 4 (H 2 O) 2 ·2H 2 O contains107 one-dimensional channels occupied by water molecules and may have useful ion-exchange properties. Ba 4 Mn 2 Ag 2 O(AsO 4 ) 4 is a new barium manganese oxide–arsenate incorporating nonlinear O–Ag–O dumbbells in its structure.108 The cubic Rb 3 Sc 2 (AsO 4 ) 3 is distinct from garnets and shows similarity to Na 4 BaCu 3 F 12 in terms of cation positions.109 Tl 2 Cu(AsO 4 )110,111 is constructed from thallium(I) cations and isolated [Cu 2 As 2 - O 8 ]4~ ions (components: AsO 4 tetrahedra and O–Cu–O dumbbells).K 2 Cu 2 (SeO 3 ),112 K 2 Cu 3 (SeO 3 ) 4 ,112 CoSeO 3 ·H 2 O-II,113 CoSeO 3 ·H 2 O-III,113 and Cr(HSeO 3 )(Se 2 O 5 )-II114 all adopt new crystal structures which have the common feature of pyramidal SeO 3 groups. The layered A 2 (MoO 3 ) 3 TeO 3 (A\NH 4 , Cs) tellurites contain115 pyramidal [TeO 3 ]2~ groups and are isostructural with their A 2 (MoO 3 ) 3 SeO 3 selenite counterparts.Mn(ReO 4 ) 2 ·2H 2 O contains116 interconnected ReO 4 tetrahedra andMnO 4 (H 2 O) 2 octahedra. Dehydration leads to the layered phase Mn(ReO 4 ) 2 (ReO 4 tetrahedra and MnO 6 octahedra). Ag 2 Cs(B 15 O 24 ) contains117 the novel, cyclic [B 15 O 24 ]3~ ion built up from twelve BO 3 and three BO 4 units. 5 Halides and oxyhalides O’Hare and co-workers reported the hydrothermal syntheses and single crystal structures of the first fully fluorinated organically templated materials–[H 3 N(CH 2 ) 3 NH 3 ]- U 2 F 10 ·2H 2 O, [H 3 N(CH 2 ) 4 NH 3 ]U 2 F 10 ·3H 2 O, [H 3 N(CH 2 ) 6 NH 3 ]U 2 F 10 ·2H 2 O, and [HN(CH 2 CH 2 NH 3 ) 3 ]U 5 F 24 .118 These layered UFO phases contain UF 8 and UF 9 polyhedra (Fig. 7), sharing edges and/or corners. The inter-lamella organic cations may be ion-exchanged, thus providing a mild-condition route to new metal–uranium –fluorides.More conventional fluorides reported in 1998 include NaLnCu 2 F 8 (Ln\Sm, Eu, Y, Er, Yb)119 which contain sheets of CuF 4 square planes interleaved alternately by Na` and Ln3` cations, both of which occupy square-antiprismatic sites. The light green Ni(NH 3 ) 2 V 2 F 8 120 was prepared adventitiously from the reaction of NH 4 F, vanadium metal and nickel extracted from the monel ampoule.It contains alternating layers of VF 6 and NiF 4 (NH 3 ) 2 octahedra. Ba 0.43(1) Sr 0.57(1) AlF 5 contains121 linear chains of AlF 6 units, whereas SrAlF 5 contains [Al 2 F 10 ]4~ dimers. Ba 2 Cu 2 AlF 11 adopts122 a new crystal structure containing a three-dimensional network of CuF 6 and AlF 6 octahedra which share both edges and vertices. The new phases La 3 Zr 4 F 25 and a-LaZr 3 F 15 emerged from a study of the LaF 3 –ZrF 4 pseudo binary system.123 The former is cubic and contains ZrF 6 octahedra and LaF 8 dodecahedra sharing vertices.The latter has an orthorhombic crystal structure containing LaF 6 trigonal prisms, ZrF 6 octahedra and ZrF 7 monocapped trigonal prisms.Eu3` luminescence properties were reported for both materials. KTbIIITbIV 2 F 12 contains124 perfectly ordered terbium(III) (as [TbF 8 ]5~ cubes) and terbium(IV) (as [TbF 8 ]4~ dodecahedra) cations. The phase transition behaviour of metastable b-CuAlCl 4 and the thermodynamically favoured a-CuAlCl 4 has been studied.125 Both phases contain large van der Waals channels and show reversible adsorption of CO and ethylene.The noncen- Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 420trosymmetric Ba 2 ScCl 7 contains126 isolated ScCl 6 octahedra and a ‘lonesome’ chloride ion bound only to Ba2`. Ab initio powder methods revealed that Rb 6 Pb 5 Cl 16 127 adopts a structure containing several di§erent metal coordination environments: RbCl 6`2 and PbCl 6`2 double capped boats, RbCl 9 tricapped trigonal prisms, and RbCl 8 cubes.One cation site contains a statistical (1: 3) distribution of Rb and Pb. The sealed-tube reaction128 of MoCl 3 and BiCl 3 led to an unusual light red material containing [Mo 6 Cl 14 ]2~ clusters and [BiCl]2` dumbbells. The Mo atoms are octahedral, and the bismuth atoms are distorted monocapped trigonal prismatic (one short]six very long Bi–Cl bonds).K 2 W 6 Br 14 , Rb 2 W 6 Br 14 and Cs 2 W 6 Br 14 adopt distinct crystal structures129 containing the [W 6 Br 14 ]2~ cluster. The cluster packing is pseudo-ccp for the potassium phase and hcp for the rubidium and caesium phases, with the alkali metal cations occupying octahedral holes.The complex formula of the subbromide Bi 34 Ir 3 Br 37 130 can be broken down into cuboctahedral [IrBi 6 Br 12 ]~ clusters, [IrBi 6 Br 13 ]2~ clusters, Bi 5 ` square pyramids and Bi 6 2` octahedra. KInBr 3 131 is a much simpler phase containing formal In2` cations as a component part of [In 2 Br 6 ]2~ groupings. BaScO 2 F, prepared by solid state reaction, appears to be the first example of a simple perovskite of stoichiometry AIIBIII[XII~] 2 [Y~].132 The oxide and fluoride ions are completely disordered.Ab initio methods showed the structure of SrHg 2 O 2 Cl 2 133 to contain unusual T-shaped HgIIO 3 groupings, as well as more familiar HgIIO 2 dumbbells. Together, these units form infinite sheets. The structure of SbTeO 3 Cl was also determined134 ab initio to reveal SbO 3 and TeO 3 pyramids linking together into strongly covalent [SbTeO 3 ]` sheets which are held together by chloride anions. Supercritical water was the reaction medium for the synthesis of Ba 2 Cu 4 Te 4 O 11 Cl 4 and BaCu 2 Te 2 O 6 Cl 2 .135 The tellurium(IV) atoms adopt pyramidal coordination in both phases.Structural and magnetic data indicated that the former phase contains mixed valent copper(I) and copper(II) whilst the latter material contains only divalent copper.The MNbAsO 5 Cl (M\Rb, Cs) types,136 grown as single crystals from a eutectic NaCl–KCl flux, are strongly layered with alternating NbAsO 5 and MCl slabs making up the structure. The structure can be visualised as ‘coordination intercalation’ of rock salt layers into the a-NbAsO 5 topology, with distorted NbO 5`1 octahedra replaced by NbO 5 Cl groupings.Bi 9 (V 1~xPx) 2 ClO 18 shows137 some resemblance to Aurivillius phases, with a major new feature of large one-dimensional tunnels occupied by chloride ions which show significant ionic mobility. NaW 2 O 2 Br 6 138 and Ag 0.37 WOBr 3 139 both contain trans-WO 2 Br 4 octahedra linked into infinite double chains.LnSCl (Ln\La–Nd)140 and Ln 7 S 6 Cl 9 (Ln\Pr, Nd)141 exemplify the rich and under-explored solid-state chemistry of the lanthanide–sulfide–chloride phase space. The basic lanthanide coordinations of square antiprism, trigonal prism and capped trigonal prism, are complicated by considerations of the S/Cl distribution over the anion sites. Ta 3 SBr 7 142 is the first example of a tantalum sulfide halide not isostructural with its niobium counterpart and may be regarded as a variety of the Cd(OH) 2 packing motif. 6 Sulfides Ozin and coworkers have done a great deal of work on the systematics of formation Annu. Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 421Fig. 8 A labelled portion of two pores from a single layer of [(C 3 H 7 ) 2 NH 2 ] 3 In 6 S 11 H. (Reproduced by permission from Chem.Commun., 1998, 1715.) and structures of microporous tin sulfides.143–146 Some clear correlations between the size and shape of template molecules and the topology of the resulting tin–sulfur framework were observed. A typical phase to emerge from this work was (C 6 N 2 H 14 ) 2 Sn 3 S 7 147 which contains Sn 3 S 4 ‘broken cube’ clusters as a component park of 24-atom rings.A facile, room-temperature synthesis was used. This area of chemistry is rapidly expanding, with respect to the metallic component of the framework. The first open-framework germanium sulfide, d-GeS 2 ,148 was prepared by the polycondensation of molecular [N(CH 3 ) 4 ] 4 Ge 4 S 10 under acidic conditions. Open framework indium sulfides reported last year include [(CH 3 ) 2 NH 2 ] 6 In 10 S 18 which is built up from vertex-linked [In 10 S 20 ]10~ ‘supertetrahedron’ clusters.149 All the In atoms are tetrahedral, with the sulfur atoms existing in terminal, bridging and trigonal geometries.This network encloses a channel system occupied by the highly disordered dimethylamine species. The layered [(C 3 H 7 ) 2 NH 2 ] 3 In 6 S 11 H150 contains pores of atom-to-atom dimensions of 6.9]12.8Å (Fig. 8). ‘Condensed’ metal sulfides are being studied by several groups. Mo 7 S 8 151 is the first example of a Chevrel type phase containg ‘extra’ molybdenum in the channels. LiAuS and NaAuS are not isostructural152 but both contain (AuS)n n~ threads which interweave into a ‘chicken-wire like’ motif involving Au· · ·Au interactions which appear to stabilise the structures.Bi 2 M 4 S 8 (M\Al, Ga)153 contains the hitherto unknown cluster cation Bi 2 4` [d(Bi–Bi)\3.14Å]. Tl 2 Au 4 S 3 is the x\4/3 member of the series A 2~xAuxQ.154 Gold–sulfur and gold–gold interactions are considered to be important in stabilising the structure. NaNbS 6 contains155 infinite anionic chains rather than the isolated anions of related compounds.PdGeS 3 was prepared156 from the elements at 600 °C and contains double chains of GeS 4 tetrahedra sharing corners encapsulating palladium cations in distorted square planar coordination to sulfur. Semiconducting Cu 4 Sn 7 S 16 is a defect spinel,157 which may be reformulated as (Cu 0.75 .0.25 )(Sn 1.75 Cu 0.25 )S 4 . The ternary sulfides A 3 MS 4 (A\Na, Rb; M\Nb, Ta) are Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 422Fig. 9 Crystal structure of SrSiAl 2 O 3 N 2 . (Reproduced by permission from Z. Anorg. Allg. Chem., 1998, 624, 1154.) based158 on a simple structure of isolated [MS 4 ]3~ ions and alkali metal cations. The A 2 Sn 4 S 9 (A\K, Rb, Cs) family159 contain a previously unseen form of the [Sn 4 S 9 ]2~ network.KIn 5 S 6 and MIn 5 S 7 (M\Na, K)160 contain In`, In3` and covalent pairs of [In 2 ]4` if an ionic model can be assumed to apply. A complicated substitution mechanism of alkali metal cations for In` occurs. Quaternary sulfides are being prepared in increasing numbers and show great structural variety. A 2 Hg 3 F 2 M 2 S 8 (A\Rb, Cs; M\Sn, Ge) contain161 both twocoordinate linear and three-coordinate pseudotrigonal Hg2` cations.Rb 2 Au 6 Sb 4 S 10 consists162 of two interpenetrating [Au 3 Sb 4 S 8 ]~ and [Au 3 S 2 ]~ frameworks. KCuGd 2 S 4 contains163 GdS 6 octahedra and CuS 4 tetrahedra delimiting tunnels occupied by the 8-fold coordinated potassium cations. K 2 Au 2 Ge 2 S 6 has one-dimensional character164 with [Ge 2 S 6 ]4~ units linked by linear, two-coordinate Au` ions.The A 2 Au 2 Cd 2 S 4 series (A\Rb, Cs) contains165 [Cd 2 S 4 ]4~ ions and linear gold atoms. K 3 CeP 2 S 8 ,166 La 8 Ti 10 S 24 O 4 ,167 and La 5 Ti 6 S 3 Cl 3 O 15 168 serve as a small memorial to the work of Jean Rouxel, and contain interesting structural features such as PS 4 tetrahedra166 and distorted TiO 5 S and TiO 5 Cl octahedra.168 7 Nitrides, phosphides, borides Reaction of the elements have led to Ba 3 N, a new binary nitride crystallising in the anti-TiI 3 structure.169 The exotic reaction medium of liquid sodium was used to prepare the complex phase Sr 39 Co 12 N 31 .170 It contains novel, linear CoN 2 units, with Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 423Fig. 10 ORTEP representation of the unit cell of Rb 4 Sn 2 Ag 4 P 6 Se 18 viewed down the b-axis.Rb` cations have been omitted for clarity. Tin and silver atoms are shown as octant-shaped ellipses, selenium as open cllipses, and phosphorus as crossed ellipses with no shading (90% thermal ellipsoids). (Reproduced by permission from Inorg. Chem., 1998, 37, 2848.) a formal cobalt valence of 1.5. SrTiN 2 , which represents only the third example of a ternary nitride containing titanium,171 was prepared by solid-state methods from the binary nitrides and is isostructural with KCoO 2 . TiN 5 square based pyramids are a feature of this phase.Members of the solid solution BaHf 1~xZrxN 2 172 adopt the same structure and show a paramagnetic to superconducting transition at ca. 8 K. The MnMo 3 N series (M\Fe, Co, n\3; M\Ni, n\2)173 can be obtained by ammonolysis of the metal molybdate precursors MMoO 4 ·nH 2 O at relatively low temperatures (\1200 K) for this type of synthesis. The cubic Ni 2 Mo 3 N structure was Annu.Rep. Prog. Chem., Sect. A, 1999, 95, 409–429 424determined ab initio from powder data. La 3 Br 6 N contains174 isolated bitetrahedral La 6 N 2 units (i.e, a pair of edge-sharing NLa 4 units) bridged by bromide ions into a three-dimensional network.SrSiAl 2 O 3 N 2 175 (Fig. 9) is a new SIALON-type phase containing corner-sharing SiON 3 , AlO 3 N, and AlO 2 N 2 tetrahedra, with the N and O atoms showing perfect long-range order. The new phosphide ScNiP cannot be described176 by a simple ionic model. It contains Sc–Sc bonds and is weakly metallic, in agreement with extended Hu� ckel calculations.Sr 3 Sn 2 P 4 is metallic177 and contains the new cyclic [Sn 12 P 24 ]36~ ion, with six phosphide ions coordinating each Sr2` cation. Cd 4 P 2 Cl 3 is based on fcc packing of cadmium atoms,178 with the tetrahedral holes occupied by Cl, P or P–P pairs. The compound previously known as ‘NaB 6 ’ is actually Na 3 B 20 and contains a novel B 7 pentagonal bipyramidal cluster unit.179 Sr 13 Mg 2 Si 20 contains sheets of silicon atoms in which the novel naphthalene-like Si 10 10~ unit can be identified.180 Rb 12 Nb 6 Se 35 is the first niobium polyselenide181 built up from infinite chains, which are constructed from NbSe 7 , Se 2 2~, Se 3 2~ groups, and the unprecedented Se 3 4~ unit.Cs 2 PdSe 8 was prepared182 solvothermally using ethylenediamine as solvent.The crystal structure contains a novel double helical arrangement of chains built up from [Pd(Se 4 ) 2 ]2~ ions. The layered ternary manganese tellurides AMnTe 2 (A\Li, Na) can be described183 as wurtzite superstructures. The sodium phase was prepared from the lithium material by ion exchange in molten NaCl. The group of Corbett have continued their extensive investigations of the structures and properties of intermetallic and metal rich phases.A key feature of their studies is the comprehensive rationalisation of crystal structures in terms of atomic sizes and bonding e§ects, as applied to, for example, Sc 8 Te 3 ,184 K 2 La 6 I 12 Os,185 and Ca 6.2 Mg 3.8 Sn 7 .186 Ba 3 AlO 4 H may be rationalised187 in terms of Ba2` cations and AlO 4 5~ and H~ anions. HBa 6 octahedra link together by corners into a threedimensional framework containing voids occupied by the aluminate ions.This network can be visualised as an inverse perovskite. Ba 3 TO (T\Ge, Si) are also inverse perovskite types,188 crystallising in the same orthorhombic space group as GdFeO 3 type phases. La 2 INi 2 contains189 graphite-like hexagonal layers of nickel.Chondroudis and Kanatzidis have reported a number of novel selenophosphosphate phases containing various [PySez]n~ groupings. 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