J O U R N A L O F C H E M I S T R Y Materials Structural complexity and metal coordination flexibility in two acetophosphonates Aurelio Cabeza, Miguel A. G. Aranda and Sebastian Bruque* Departamento de Quý�mica Inorga�nica, Cristalografý� a y Mineralogý�a, Universidad de Ma�laga, 29071 Ma�laga, Spain. E-mail: bruque@uma.es Received 18th June 1998; Accepted 29th July 1998 Two divalent metal acetophosphonates, Pb6(O3PCH2CO2)4 and Mn3(O3PCH2CO2)2, have been synthesised hydrothermally.They crystallise in the triclinic system, space group P19, a=11.0064(1), b=12.3604(1), c=8.9783(1) A° , a=98.632(1), b=90.474(1), c=75.629(1)°, Z=2, for M=Pb, and a=10.0146(5), b=6.3942(4), c=8.4796(6) A° , a=101.452(4), b=106.254(2), c=96.431(4)°, Z=2, forM=Mn. The structures were solved ab initio using direct methods from synchrotron powder diVraction data (l#0.4 A° ) for M=Pb and from laboratory X-ray data for M=Mn.The crystal structure of the Pb compound is very complex with 38 non-hydrogen atoms in general positions (114 refined positional parameters), it had been refined by Rietveld method using soft constraints, and converged to RWP=6.8% and RF=1.6%. The structure forM=Mn has a moderate complexity with 19 nonhydrogen atoms (57 refined positional parameters) which was also refined with soft constraints to RWP=8.3%, RF=3.9%. Both compounds show a framework built of alternate metal oxide inorganic layers, pillared by the organic groups.The metal environments in these materials are very distorted. Manganese atoms present three diVerent distorted oxygen environments: four-, five- and six-coordinate.Thermal and IR data are also reported and discussed. tetrahedral and one octahedral sites for the zinc atoms. As Introduction yet, the structure of Mn3(O3PC2H4CO2)2 has not been solved, The interest in the chemistry of phosphonates has drastically although it seems to be isostructural to the Zn analog.20b The increased in the last twenty years.1 Initially, these compounds synthesis and structure of Co3(O3PC2H4CO2)2·6H2O has very (with phosphonic acid H2O3PR, R=alkyl or aryl group) were recently been reported exhibiting a 3D ‘open’ framework.21 mainly layered with structures very related to that of the In this paper, we report the synthesis, characterisation parent zirconium hydrogen phosphate a-Zr(HPO4)2·H2O.2 and crystal structure of two acetophosphonates, The ability to design structures with specific properties that Pb6(O3PCH2CO2)4 and Mn3(O3PCH2CO2)2.these materials show, as well as their unusual compositional and structural diversity varying from one-dimensional arrange- Experimental ments3,4 to three-dimensional microporous frameworks,5–7 via the most common layered frameworks,8–10 have stimulated Synthesis of Mn3(O3PCH2CO2)2 extensive exploration of their chemistry.In fact, the importance of such systems in several research areas such as electrochemis- Chemicals of reagent quality were obtained from Aldrich and try,11,12 microelectronic,13 photochemical mechanisms14 and used without purification. Manganese(II) acetophosphonate catalysis15,16 has been widely recognised.was synthesised by adding 1.43 mmol manganese(II) acetate Metal phosphonates with 3D frameworks can be synthesised tetrahydrate dissolved in 10 ml distilled water to an aqueous as nanotubular phosphonates or alternatively as pillared lay- solution (10 ml ) containing 7.14 mmol acetophosphonic acid; ered structures (PLS) by using, for example, diphosphonic the resulting Mn5P molar ratio was 155 and the solution has acids H2O3P–R–PO3H2 as pillaring agent.17 Hence, it is poss- a pH of 1.4.No precipitate is formed even on hydrothermally ible to design the interlayer spacing (and chemistry) through heating at 150 °C for one week thus the pH of the solution the shape, size and nature of the organic spacer R. Several was increased by adding 30% aqueous NaOH dropwise up to other ways to obtain PLS materials have also been adopted, pH 4.3.At this point, a precipitate started to develop. e.g. use of carboxyphosphonates,18 or through the reaction of This suspension was heated again in a Teflon-lined autoclave free hydrogen carboxyphosphonate groups with intercalated at 150 °C for 5 days. A single powdered phase was filtered, alkyl diamines H2N–R–NH2 at high temperature which yields washed with water and with acetone, and dried under vacuum.covalent amide links.19 The synthesis and structures of several 2-carboxyethyl- Synthesis of Pb6(O3PCH2CO2)4 phosphonates of divalent and trivalent metals have Lead acetophosphonate was also prepared hydrothermally. been reported. For example, Fe phosphonates,20a 4.08 mmol acetophosphonic acid were dissolved in 10 ml dis- FeIII(HO3PR)3(H2O3PR), FeII(HO3PR)2, FeIII(HO3PR) tilled water.A second solution containing 0.816 mmol of lead (O3PR)·H2O and FeIIIO(HO3PR)·H2O, with R=C2H4CO2H; acetate trihydrate dissolved in 15 ml of water was added slowly Bi phosphonates,18c Bi(O3PC2H4CO2)·H2O and and with constant stirring. The resulting solution has a Pb5P Bi(HO3PC2H4CO2H)(O3PC2H4CO2H); and even bimetalmolar ratio of 155 and a pH of 1.4.Under these conditions, lic phosphonates,20b MnZn2(O3PC2H4CO2)2, as well as no precipitate formed; thus as described above, the pH was Mn(O3PC2H4CO2H)·H2O and Mn3(O3PC2H4CO2)2. The increased up to 1.8, leading to the formation of a white structures of most of these compounds exhibit inorganic layers precipitate.This mixture was heated in a Teflon-lined autoclave formed by the metal cations and the PO3 and CO2 moieties, at 150 °C for 6 days. A single powdered phase was isolated by pillared by the organic groups to yield 3D frameworks. The filtration, washed with water and acetone, and finally dried metal environments are very versatile in these materials as has been shown for Zn3(O3PC2H4CO2)2,18b where there are two under vacuum.J. Mater. Chem., 1998, 8(11), 2479–2485 2479Elemental analysis. Carbon and hydrogen contents were thermal decomposition reactions: determined by elemental chemical analysis on a Perkin-Elmer Mn3(O3PCH2CO2)2+4O2�Mn3(PO4)2+4CO2+2H2O 240 analyser. Analytical data for Mn3(O3PCH2CO2)2: C, Pb6(O3PCH2CO2)4+8O2�2Pb3(PO4)2+8CO2+4H2O 10.54; H, 0.95.Calc.: C, 10.94; H, 0.91%. Analytical data for Pb6(O3PCH2CO2)4: C, 5.20; H, 0.45. Calc.: C, 5.35; H, 0.45%. The thermal decomposition products were identified through the powder patterns collected for the samples heated at 1000 °C. This high temperature was used to increase crystal- Thermal analysis. TGA and DTA data were collected on a linity which helps in the identification procedure.The patterns Rigaku Thermoflex apparatus at a heating rate of 10 K min-1 matched with those present in the PDF database: no. 31-0827 in air with calcined Al2O3 as an internal reference standard. for Mn3(PO4)2 and 24-0585 for Pb3(PO4)2. IR study. IR spectra were recorded on Perkin Elmer 883 IR spectroscopy study spectrometer in the spectral range 4000–400 cm-1, using dry KBr pellets containing 2% of sample.The IR spectra of both compounds are shown in Fig. 2. There are no bands in the O–H stretching region (3500–3000 cm-1), X-Ray powder diVraction. The powder diVraction pattern which is consistent with the absence of water molecules or for Mn3(O3PCH2CO2)2 were collected on a Siemens D-5000, hydrogen phosphonate/carboxylate groups in the structures. automated diVractometer using graphite-monochromated Cu- As it can be observed in Fig. 2, no band is seen at ca. Ka radiation. The sample was diluted and blended with 1715 cm-1 corresponding to n(CNO) for the free acid spherical particles of Cab-O-Sil M-5 (Fluka), to reduce pre- (–COOH). However, there are two pairs of strong bands ferred orientations.22 The angular range scanned was 7–80° centred at 1610, 1550 and 1425, 1380 cm-1, for (2h), with a step size of 0.02° and counting time of 20 s per step.Mn3(O3PCH2CO2)2, and at 1550, 1505 cm-1 and 1420, For Pb6(O3PCH2CO2)4, high resolution synchrotron 1370 cm-1, for Pb6(O3PCH2CO2)4, which are assigned to the powdlected on the diVractometer of the BM16 antisymmetrical and symmetrical stretching vibrations of C–O line of ESRF (Grenoble, France).The sample was loaded in groups when present as COO- moieties.24 There are two set a borosilicate glass capillary (diameter=0.5 mm) and rotated of bands probably due to crystallographically diVerent during data collection. The pattern was collected with l= carboxylic groups coordinated to the metal atoms, as has been 0.399 89(2) A° , in the angular range 1–30° in 2h, for an overall confirmed by XRD.Other bands characteristic of the count time of 10 h. Raw data were normalised and reduced to phosphonate groups are also present in the IR spectra. a constant step size of 0.003° with local software. Further experimental details about data collection and analysis of this Structure determination type of data have been already reported.23 The X-ray laboratory powder pattern for Mn3(O3PCH2CO2)2 was auto-indexed using the TREOR90 program25 giving a Results and discussion triclinic unit cell with a=10.001, b=6.379, c=8.478 A° , a= 101.39, b=106.32, c=96.38°, V=500.8 A° 3, Z=2, Vat (non-H Thermal study atoms)=13.2 A° 3 atom-1, M20=3326 and F20=55 (0.0085, TGA–TDA curves for Mn3(O3PCH2CO2)2 and 43).27 The X-ray synchrotron powder pattern for Pb6(O3PCH2CO2)4 are shown in Fig. 1. Only one exothermic Pb6(O3PCH2CO2)4 was auto-indexed by the TREOR9025 proe Vect, with an abrupt change in the DTA curve, was observed gram in a triclinic unit cell with dimensions: a=11.002, for both compounds. For Mn3(O3PCH2CO2)2 the exotherm b=12.365, c=8.984 A° , a=98.68, b=90.49, c=75.64°, V= takes place at higher temperature (570 °C) than for 1170.0 A° 3, Z=2, Vat=15.38 A° 3 atom-1, M20=4826 and F20= Pb6(O3PCH2CO2)4 (418 °C).This eVect is due to the combus- 161 (0.0048, 26).27 Both crystal structures were solved by ab tion of the acetocarboxylic groups and it has an associated initio procedures. The pattern decomposition option of the mass loss of 18.5 and 11.0%, for M=Mn and Pb, respectively.GSAS package28 was used to extract corrected structure These values are in good agreement with theoretical values factors, using the Le Bail method,29 from a limited region of (19.14 and 9.38%, respectively) calculated for the following the pattern, 14<2h<62° for Mn compound (650 reflections) and 1.5<2h<20.5°, for Pb compound (1500 reflections).The Fig. 1 TGA-DTA curves for (a) Mn3(O3PCH2CO2)2 and (b) Fig. 2 IR spectra for (a) Mn3(O3PCH2CO2)2 and (b) Pb6(O3PCH2CO2)4. Pb6(O3PCH2CO2)4. 2480 J. Mater. Chem., 1998, 8(11), 2479–2485Fig. 3 Observed, calculated and diVerence X-ray powder diVraction profiles for Mn3(O3PCH2CO2)2. The tick marks are calculated 2h angles for Bragg peaks.patterns were fitted without any structural model by refining P–C [1.80(1) A° ], O,O [2.55(1) A° ], O,O [2.73(1) A° ], C–Ccarb [1.50(1) A° ], Ccarb–Ocarb [1.23(1) A° ], C,Ocarb the overall parameters: background, zero-point error, unit cell and peak shape values. A pseudo-Voigt peak shape function30 [2.36(1) A° ] and Ocarb,Ocarb [2.15(1) A° ], to retain a reasonable geometry for the tetrahedral O3PC and carboxylic groups.The corrected for asymmetry31 was used. SIRPOW9232 gave the positions of three manganese atoms and two phosphorus final weights for the soft constraints were -10. The powder pattern collected in h/2h geometry for M=Mn showed a atoms by direct methods. SHELXS8633 gave the positions of the six lead atoms by both Patterson map and direct methods.strong preferred orientation along the [010] and [100] directions, which were corrected using the March–Dollase34 func- For both compounds, the found atoms were included in the Rietveld refinements using the overall parameters obtained in tion with coeYcients of 1.147(7) for [010] and 0.666(6) for [100]. The synchrotron powder pattern collected on a capillary the last cycle of the ab initio refinements. RwP dropped to 23.6% for M=Pb and to 32.0% for M=Mn by refining only for M=Pb did not show preferred orientation.The final refinement for Mn3(O3PCH2CO2)2 converged to RwP=8.29%, the scale factors. Successive diVerence Fourier maps and soft constrained refinements led to the atomic positions of the RP=6.43% and RF=3.91%; and for Pb6(O3PCH2CO2)4 to RwP=6.76%, RP=5.22% and RF=1.64%; R factors are defined remaining atoms.It is worthy to underline that due to the complexity of these structures, the atomic positions were by Rietveld,35 and Larson and Von Dreele.28 The Rietveld plots for Mn and Pb compounds are shown in Fig. 3 and 4, refined using the following soft constraints, P–O [1.53(1) A° ], Fig. 4 Observed, calculated and diVerence synchrotron X-ray (l#0.4 A° ) powder diVraction profiles for Pb6(O3PCH2CO2)4 between 1.5 and 30° (2h).The tick marks are calculated 2h angles for Bragg peaks. J. Mater. Chem., 1998, 8(11), 2479–2485 2481Table 1 Positional parameters for Mn3(O3PCH2CO2)2 in space group respectively. Atomic parameters are presented in Table 1 and P19 bond lengths in Table 2 for M=Mn, and in Table 3 and 4 for M=Pb, respectively.Atom x y z Uiso/A° 2 Attempts to solve the structure of Pb6(O3PCH2CO2)4 from laboratory X-ray powder data were unsuccessful. Thus, a Mn(1) 0.4490(4) 0.0986(9) 0.8271(6) 0.017(2) Mn(2) 0.1209(5) 0.8001(10) 0.5498(8) 0.032(2) synchrotron pattern was collected owing to the high quality Mn(3) 0.3827(5) 0.6098(11) 0.3819(6) 0.022(2) of diVraction data, utilising the very high angular resolution P(1) 0.6856(7) 0.9316(14) 0.6480(8) 0.044(4) and the absence of preferred orientation. Under these con- P(2) 0.3651(7) 0.5789(13) 0.7877(10) 0.027(3) ditions, with better structure factors, such a complex structure O(1) 0.6212(11) 1.1134(19) 0.7346(13) 0.014(2) (38 non-hydrogen atoms in the asymmetric part of the unit O(2) 0.5839(11) 0.7120(17) 0.5985(15) 0.014 cell including six crystallographically independent lead atoms) O(3) 0.7177(13) 0.9879(23) 0.4927(12) 0.014 O(4) 0.2851(11) 0.6070(23) 0.6098(12) 0.014 could be successfully solved from powder diVraction data.O(5) 0.4682(10) 0.4203(18) 0.7756(17) 0.014 O(6) 0.4398(10) 0.8000(15) 0.9083(15) 0.014 Structure description O(7) 0.9902(12) 0.6850(23) 0.6842(22) 0.014 O(8) 0.8228(15) 0.5306(21) 0.7581(22) 0.014 The crystal structure of Mn3(O3PCH2CO2)2 contains 19 O(9) 0.2318(15) 0.0852(20) 0.8128(18) 0.014 non-hydrogen atoms in the asymmetric unit of the unit cell, O(10) 0.0533(12) 0.1953(24) 0.6658(18) 0.014 C(1) 0.8496(10) 0.9099(20) 0.7968(15) 0.008(5) Table 3 Positional parameters for Pb6(O3PCH2CO2)4 in space group C(2) 0.8891(20) 0.6936(19) 0.7397(33) 0.008 P19 C(3) 0.2329(11) 0.4619(18) 0.8705(15) 0.008 C(4) 0.1619(15) 0.2302(19) 0.7876(22) 0.008 Atomx y z Uiso/A° 2 Pb(1) 0.33231(30) 0.29920(27) 0.91369(32) 0.0111(9) Pb(2) -0.00392(28) 0.49459(25) 0.23407(31) 0.0081(9) Pb(3) 0.17993(28) 0.69240(27) 0.50670(31) 0.0055(8) Pb(4) 0.50768(29) 0.50721(25) 0.73390(30) 0.0059(9) Pb(5) 0.39799(28) 0.87470(26) 0.77513(33) 0.0113(9) Pb(6) 0.11856(29) 0.11283(27) 0.08619(31) 0.0204(10) P(1) 0.2555(14) 0.4298(12) 0.5390(15) 0.006(2) P(2) 0.7553(14) 0.4389(12) -0.0656(14) 0.006 P(3) 0.5803(14) 0.0665(13) 0.8220(15) 0.006 P(4) 0.0900(13) 0.0029(11) 0.7295(14) 0.006 O(1) 0.2434(27) 0.4115(21) 0.7048(15) 0.006 O(2) 0.3625(20) 0.4870(22) 0.5195(29) 0.006 O(3) 0.1299(18) 0.5001(20) 0.4887(30) 0.006 O(4) 0.3979(24) 0.3001(33) 0.1981(29) 0.006 O(5) 0.2017(26) 0.3019(34) 0.1846(29) 0.006 O(6) 0.8684(21) 0.4867(23) -0.0129(31) 0.006 O(7) 0.6337(20) 0.5102(20) 1.0190(28) 0.006 O(8) 0.7415(26) 0.4337(20) 0.7620(16) 0.006 O(9) 0.8882(26) 0.3109(33) 0.2086(30) 0.006 O(10) 0.6940(25) 0.3074(34) 0.2191(29) 0.006 O(11) 0.5839(28) 0.1399(21) 0.9763(20) 0.006 O(12) 0.3439(24) 0.0569(14) 0.1757(28) 0.006 O(13) 0.5568(16) 0.9301(26) 0.2210(30) 0.006 O(14) 0.5240(33) 0.3048(22) 0.7667(31) 0.006 O(15) 0.6004(34) 0.2736(22) 0.5403(27) 0.006 O(16) 0.0417(15) 0.9513(23) 0.1959(27) 0.006 O(17) 0.8087(20) 0.0264(23) 0.1525(25) 0.006 O(18) 0.9049(28) 0.1020(15) 0.3916(23) 0.006 O(19) 0.8962(33) 0.7474(24) 0.1525(25) 0.006 O(20) -0.0199(33) 0.6963(21) 0.3555(33) 0.006 C(1) 0.2925(30) 0.2924(14) 0.4223(20) 0.006 C(2) 0.2963(25) 0.305(4) 0.2586(24) 0.006 C(3) 0.7845(29) 0.2963(13) 0.9779(22) 0.006 C(4) 0.7901(27) 0.302(5) 0.1457(23) 0.006 C(5) 0.6523(26) 0.1229(19) 0.6810(30) 0.006 C(6) 0.595(4) 0.2444(21) 0.6650(28) 0.006 C(7) 0.1257(30) 0.1115(15) 0.6344(26) 0.006 Fig. 5 [001] View of the crystal structure of Mn3(O3PCH2CO2)2. C(8) 0.082(5) 0.2308(21) 0.7132(30) 0.006 Table 2 Bond lengths (A° ) for Mn3(O3PCH2CO2)2.Long Mn–O interactions are given in italics Mn(1)MO(1) 2.085(12) Mn(1)MO(6) 2.156(12) Mn(1)MO(9) 2.135(15) Mn(1)MO(5) 2.185(11) Mn(1)MO(6) 2.134(12) Mn(1)MO(3) 2.667(10) Mn(2)MO(3) 2.147(11) Mn(2)MO(7) 2.123(14) Mn(2)MO(9) 2.465(14) Mn(2)MO(4) 2.173(13) Mn(2)MO(10) 2.153(13) Mn(2)MO(10) 2.753(14) Mn(3)MO(1) 2.190(13) Mn(3)MO(4) 2.399(11) Mn(3)MO(3) 2.975(15) Mn(3)MO(2) 2.240(11) Mn(3)MO(5) 2.265(11) Mn(3)MO(2) 2.152(11) Mn(3)MO(8) 2.060(15) P(1)MO(1) 1.550(5) P(2)MO(4) 1.554(5) P(1)MO(2) 1.547(5) P(2)MO(5) 1.535(5) P(1)MO(3) 1.538(5) P(2)MO(6) 1.538(5) C(1)MC(2) 1.506(6) P(1)MC(1) 1.808(5) P(2)MC(3) 1.820(5) C(2)MO(7) 1.232(5) C(2)MO(8) 1.232(5) C(3)MC(4) 1.505(6) C(4)MO(9) 1.240(6) C(4)MO(10) 1.235(6) 2482 J.Mater. Chem., 1998, 8(11), 2479–2485Table 4 Bond lengths (A° ) for Pb6(O3PCH2CO2)4.Long Pb–O interactions are given in italics and the average Pb–O distance for each polyhedron (coordination number as subscript) are also given Pb(1)MO(1) 2.55(2) Pb(1)MO(7) 2.46(3) Pb(1)MO(19) 2.76(4) Pb(1)MO(4) 2.65(3) Pb(1)MO(11) 3.08(3) Pb(1)MO(8) 3.98(2) Pb(1)MO(5) 2.83(3) Pb(1)MO(13) 2.88(3) Pb(1)MO(20) 4.18(3) Pb(1)MO(6) 3.02(3) Pb(1)MO(14) 2.52(3) <Pb(1)MO9> 2.75 Pb(2)MO(1) 2.63(3) Pb(2)MO(6) 2.62(2) Pb(2)MO(8) 3.22(3) Pb(2)MO(3) 2.71(2) Pb(2)MO(6) 2.57(3) Pb(2)MO(9) 3.24(3) Pb(2)MO(3) 2.84(3) Pb(2)MO(20) 2.53(3) Pb(2)MO(19) 4.19(4) Pb(2)MO(5) 2.83(4) Pb(2)MO(9) 2.79(3) <Pb(2)MO8> 2.69 Pb(3)MO(2) 2.84(3) Pb(3)MO(10) 2.82(3) Pb(3)MO(1) 4.04(2) Pb(3)MO(3) 2.55(3) Pb(3)MO(15) 2.60(4) Pb(3)MO(8) 2.69(2) Pb(3)MO(18) 2.51(2) Pb(3)MO(9) 2.68(3) Pb(3)MO(20) 2.57(3) <Pb(3)MO8> 2.66 Pb(4)MO(2) 2.51(3) Pb(4)MO(7) 2.79(2) Pb(4)MO(15) 3.08(3) Pb(4)MO(2) 2.72(2) Pb(4)MO(8) 2.53(3) Pb(4)MO(1) 3.39(3) Pb(4)MO(4) 2.81(4) Pb(4)MO(10) 2.75(4) Pb(4)MO(15) 3.89(2) Pb(4)MO(7) 2.90(3) Pb(4)MO(14) 2.53(3) <Pb(4)MO9> 2.73 Pb(5)MO(4) 2.74(3) Pb(5)MO(17) 2.35(2) Pb(5)MO(12) 3.91(1) Pb(5)MO(10) 2.69(4) Pb(5)MO(15) 3.13(3) Pb(5)MO(11) 2.27(2) Pb(5)MO(12) 3.17(3) Pb(5)MO(13) 2.58(3) Pb(5)MO(18) 3.61(3) <Pb(5)MO5> 2.53 Pb(6)MO(5) 2.74(4) Pb(6)MO(19) 2.93(3) Pb(6)MO(18) 3.67(3) Pb(6)MO(12) 2.56(3) Pb(6)MO(9) 3.13(4) Pb(6)MO(11) 3.91(3) Pb(6)MO(16) 2.67(3) Pb(6)MO(16) 3.19(3) Pb(6)MO(17) 2.54(3) Pb(6)MO(17) 3.67(3) <Pb(6)MO5> 2.69 P(1)MO(1) 1.551(7) P(2)MO(6) 1.547(7) P(3)MO(11) 1.543(7) P(1)MO(2) 1.540(7) P(2)MO(7) 1.541(7) P(3)MO(12) 1.550(7) P(1)MO(3) 1.543(7) P(2)MO(8) 1.548(7) P(3)MO(13) 1.546(7) P(1)MC(1) 1.810(8) P(2)MC(3) 1.813(8) P(3)MC(5) 1.809(7) P(4)MO(16) 1.538(7) C(1)MC(2) 1.502(8) C(3)MC(4) 1.499(8) P(4)MO(17) 1.546(7) C(2)MO(4) 1.233(8) C(4)MO(9) 1.236(8) P(4)MO(18) 1.553(7) C(2)MO(5) 1.235(8) C(4)MO(10) 1.233(8) P(4)MC(7) 1.815(8) C(5)MC(6) 1.506(8) C(6)MO(14) 1.231(8) C(8)MO(19) 1.230(7) C(6)MO(15) 1.233(8) C(7)MC(8) 1.498(8) C(8)MO(20) 1.231(7) Fig. 6 [010] View of the crystal structure of Mn3(O3PCH2CO2)2 with atoms labeled. J. Mater. Chem., 1998, 8(11), 2479–2485 2483be schematically summarised as ,Mn(3)O(1)O(5)- Mn(1)O(6)O(6)Mn(1)O(1)O(5)Mn(3)O(2)O(2)Mn(3),. It is of interest that all these oxygen atoms belong to the phosphonate groups.These chains are interconnected along the a-axis through the carboxy groups and the Mn(2)O4 groups. Fig. 6 shows the crystal structure down to the b-axis from which the links of the chains along the c-axis through the oxygens of the phosphonates defining a layer can be seen (in the bc plane). The structure can be depicted as inorganic layers in the bc-plane formed by the manganese polyhedra sandwiched by acetophosphonate groups in an ordered way such that phosphonate heads always point to the more coordinated manganese groups and the carboxylate tails always point to the four-coordinate manganese atoms.In this sense, it can be conceived as a PLS but with no space between the inorganic layers. There are small cavities where the hydrogens of the CH2 groups [C(1) and C(3)] are located (Fig. 6); there is not enough empty space even for water molecules. The crystal structure of Pb6(O3PCH2CO2)4 contains 38 atoms in the asymmetric of the unit cell, all in general positions and there are six crystallographically independent lead atoms. To define the oxygen polyhedra around these lead atoms is more diYcult than in the Mn case owing to the irregular geometry around Pb2+.It is also important to keep in mind the possible lone-pair eVect of PbII which has very important implications in coordination environment. It has been assumed that Pb–O interactions occur for distances >15% of the Shannon average PbII–O bond distance in an eight-fold oxygen coordination resulting in a limiting Pb–O bond distance of 3.09 A° .Shannon average Pb–O bond distances in 5, 6, 7, 8, 9 and 10 oxygen coordinations are: 2.59, 2.61, 2.63, 2.69, 2.75 and 2.80 A° , respectively. The Pb–O bond distances are given in Table 4. With this criterion, there are two five-, two eightand two nine-coordinated lead atoms. It is of note that both five-coordinated lead atoms have two oxygens at quite short interacting distances of ca. 3.15 A° so they may be conceived as six- or even seven-coordinated (see Table 4). As for the manganese compound, the four phosphonate groups are tetra- Fig. 7 Crystal structure of Pb6(O3PCH2CO2)4 down to the a-axis with hedral and the four carboxy groups are trigonal. the numbering scheme used in Table 3. Only Pb–O bonds shorter than The structure of Pb6(O3PCH2CO2)4 (Fig. 7) is fairly similar 2.95 A° are shown for clarity.to that of the manganese analogue. This is expected as both compounds have the same stoichiometry and the same organoall in general positions. There are three crystallographically inorganic covalent building block [O3PCH2CO2]3-. For M= independent manganese atoms. Shannon average MnII-O bond Pb, there are also two types of lead layers with higher and distances are 2.15 A° for four-fold oxygen coordinations, and lower oxygen coordination numbers.One layer is formed by 2.23 A° for six-fold oxygen coordinations. If it is assumed that Pb(1)MPb(4) which are eight and nine-coordinated. The other Mn–O interactions take place within 15% of the reported type of layer is built up of Pb(5) and Pb(6) which are fiveaverage MnII–O bond distances, then, three types of manganese coordinate.However, the arrangements of the carboxy phoscoexist in this structure. Although somewhat arbitrary, this phonate chains between these layers are diVerent in both assumption allows us to define the coordination polyhedra. materials. To satisfy the coordination requirement around the Hence, Mn(1) is surrounded by five oxygens with bond lead layer with lower coordination number, two carboxy distances ranging between 2.09 and 2.19 A° , with a long inter- phosphonate chains point with the phosphonate heads towards action to a sixth oxygen at 2.68 A° .Mn(2) is surrounded by this layer and the tails to the other type of lead layer. four oxygens with bond distances between 2.12 and 2.17 A° , To summarise, we have studied two acetophosphonates, with two long interactions at 2.47 and 2.75 A° . Mn(3) is six- Mn3(O3PCH2CO2)2 and Pb6(O3PCH2CO2)4, which show high coordinate with bond distances between 2.06 and 2.40 A° .The thermal stability. Although the syntheses were carried out at two phosphonate groups are tetrahedral and the two carboxy low pH (4.3 and 1.8, respectively) they do not result in free groups are trigonal.carboxylic groups which would presumably result in more The crystal structure of Mn3(O3PCH2CO2)2 viewed down open structure. These structures are diVerent and clearly the c-axis is displayed in Fig. 5. Infinite chains of oxide more compact than those shown by their analogous 2-carbmanganese polyhedra [Mn(1) and Mn(3)] run parallel to the oxyethylphosphonates, i.e.Zn3[O3P(CH2)2CO2]218b and b-axis, and share edges. The chains can be described as Co3(O3PC2H4CO2)2·6H2O.21 This is mainly due to the pres- Mn(1)2O8 dimers linked to Mn(3)2O8 dimers by a common ence of an extra methylene group which leads to a more edge formed by O(1) and O(5). The Mn(1)MO(1)MMn(3) hydrophobic region which pillars the metal layers.and Mn(1)MO(5)MMn(3) angles are 106.5 and 100.7°, respectively. Mn(1)2O8 dimers form by sharing of an edge This work was supported by the research grants FQM-113 of with two symmetry equivalent Mn(1)MO(6)MMn(1) angles Junta de Andalucý�a (Spain). We thank Drs. E. Dooryhee, G. of 103.2(4)°. Dimers Mn(3)2O10 also form by sharing an Vaughan and A.Fitch for assistance during data collection on edge with two symmetry equivalent Mn(3)MO(2)MMn(3) angles of 96.4(4)°. These edge-sharing infinite chains can BM16 and to ESRF for the provision of synchrotron facilities. 2484 J. Mater. Chem., 1998, 8(11), 2479–24851993, 32, 1357; (c) G. Alberti, F. Marmottini, S. Murcia-Mascaros References and R. Vivani, Angew. Chem., Int.Ed. Engl., 1994, 33, 1594; (d) M. E. Thompson, Chem.Mater., 1994, 6, 1168; (e) D.M. Poojary, 1 A. Clearfield, Prog. Inorg. Chem., 1998, 47, 371; S. Drumel, B. Zhang, P. Bellinghausen and A. Clearfield, Inorg. Chem., 1996, V. Penicaud, D. Deniaud and B. Bujoli, Trends Inorg. Chem., 35, 5254. 1996, 4, 13. 18 (a) G. Cao, L. K. Rabenberg, C. M. 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