1634 Inorganic Chemistry, Vol. 14, No. 7 , 1975 (14) D. T. Cromer and J . T. Waber, Acta Crystallogr., 18. 104 (1965). (15) R. F. Stwart. J. T. Davidson, and W.T. Simpson, J . Chem. Phys., 42, 117s .. . (196s). \ - - --,.
(16) “International Tables for X-Ray Crystallography”, Vol. 11, Kyncch Press, Birmingham. England, p 202. ( 1 7 ) G. J. Visser, G . J. Heeres, J. Walters, and A. Vos, Acta Crysrallogr., Sect. 5, 24, 467 (1968). (18) Supplementary material. (19) D. W. J. Cruickshank et al., “Computing Methods and the Phase Problem in X-Ray Crystal Analysis”, R. Pepinsky et al., Ed., Pergamon Press. Oxford. 1961. (20) E. M. Bradley. J. Chatt, R. L.Richards, and G. A. Sim, J . Chem. Soc. D, 1322 (1969). (21) C. Panattoni, R. Bombiere, E. Forsellini, B. Crocioni, and V. Belluco, J . Chem. Soc. D, 187 (1969). (22) B. M. Craver, and D.Hall, Acta Crystallogr., 21, 177 (1966). (23) D. Moros, J . Dehand, and R. Weiss, C. R. Hebd. Seances Acad. Sei.. Ser. C , 276, 1471 (1968). (24) V. G. Albano, P. L. Bellon. and M.Sansori. Inorg. Chem., 8, 298 (1969),
and references contained therein.
(25) W. Eventoff, Ph.D. Thesis, tiniversity of Michigan, 1972.
Banks, Chianelli, and Korenstein (26) F. Basolo and R. G. Pearson. “Mechanisms of Inorganic Substitution”, Wilcy. Yew York, h-,Y,, 1967. pp 351-375. (27) G . H. Stout and L. H. Jensen, “X-Ray Structure Determination”, Macmillan. New York. V.Y.. 1968. pp 421-425. (28) F. A. Cotton and G . Wilkinson, “Advanced Inorganic Chemistry”, 2nd ed, Interscience, New York. Y.Y., 1967, pp 45. 115. (29) h-.C. Stephenson. J . Inorg. h’uci. Chem.. 24, 791 (1962). (30) J . P. Beale and N. C. Stephenson, Acta Crjstailogr.. Sect. E. 27, 73 (1971). (3 1) “International Tables for X-Ray Crystallography”, Vol. 11, Kynoch Press, Birmingham. England, 1962, p 276. (32) W. R. Mason. 111, and H. B. Gray, J . Am. Chem. Soc.. 90, 5721 (1968). (33) J. Chatt. G . A. Gamelin, and L. E. Orgel, J . Chem. Soc., 486 (1958). (34) J. R. Preer and H. B. Gray, J . A m . Chem. Soc., 92, 7306 (1970). (35) G . Dolcetti, A. Peloso. and L. Sindarelli, Garz. Chim. Itul., 96, 1948 (1966). 1361 A. R. Katritzkv and A. P. Ambler. “Phvrical Methods in Heterocvclic Chemistry”, Vbl. 2, A . R. Katritzky, Ed., Academic Press, New York, N.Y., 1963, pp 205-208. ( 3 7 ) 0 . H. S. Greer, W . Kynaston, and H. M. Paisley, Spectrochim. Acta, 19. 549 (1963). \
,
Contribution from the Department of Chemistry, Polytechnic Institute of New York, Brooklyn, New York 11201
Crystal Chemistry of Struvite Analogs of the Type M g M P 0 4 . 6 H 2 8 (M+ = K+, Rb+, Cs+, T1+, N H 4 + ) 1 E. BANKS,* R. CHIANELL1,Za and R . KORENSTEINZb AIC4063 1 G
Received S e p t e m b e r 4 , I974
T h e crystallographic properties and the infrared absorption spectra of the struvite analogs of the type MgMP04.6Hz0 where M + = K+, R b f , C s f , T1+. or h-H4+ are reported. The relative stabilities of the struvite analogs are discussed in terms of the radii of the univalent ions.
I. Introduction The mineral struvite (MgNH4P04-6H20) is often found associated with living or decomposing organisms. It has been described in ref 3 as being found in dung, putrescent matter, canned foods, and bladder or kidney concretions. The crystal structure was solved with a crystal obtained from a tin of salmon. This structure was based on the earlier work of Bland and Basinski4 and Whitaker and Jeffery.536 The analogous compound MgKP04.6H2O was reported as forming an isomorphous series with struvite by Lehr et al.7 The infrared spectra, X-ray diffraction patterns, and optical and crystallographic properties of struvite and the potassium analog were also reported. Struvite has been compared to the related compound CaKAs04.8HzO,* and their biological importance as possible precursors of nuclei of crystallization has been noted. The apparently related materials MgCsP04.6H20 and MgCsAsOc6HzO have also been reported by Ferrari et al.93’0 It is the purpose of this report to study the substitution of alkali metals and “pseudoalkali” cations in the struvite crystal structure. 11. Experimental Section All crystals were grown by means of the gel diffusion technique. The growth of struvite by the gel diffusion method has been reported by Banks et a1.11,12 An aqueous solution of 0.05 M M g S 0 4 and 0.04-0.02 M MzEDTA (EDTA = ethylenediaminetetraacetate) was adjusted to pH 10 with M O H . Eastman Kodak “ultrapure” calfskin gelatin was dissolved in the resulting solution (55 g/l.) and allowed to set. Before setting, several drops of formaldehyde were added to strengthen the gel and to prevent growth of molds. Generally 100 ml of gel was set in a 250-1111 electrolytic beaker. When the gel had set an equivalent amount of a solution of 0.05 M M z H P 0 ~ x H z 0 which had been adjusted to p H 10.0 with MOH was carefully poured over the gel. The beaker was covered and the crystal growth proceeded at the gel-liquid interface and into the gel. Experiments were complete within several weeks and the crystals were harvested. Photographs of the resulting crystals may be seen in Figure 1.
All reagents used were Baker Analyzed reagents except the Eastman Kodak calfskin gelatin. Rubidium and cesium phosphates were prepared by neutralizing H3P04 with an equivalent amount of R b O H or C s O H in situ. Rubidium, ammonium, potassium, and cesium salts of EDTA were prepared by neutralizing HzEDTA with an equivalent amount of R b O H or C s O H also in situ. In the case of the thallium salt T I N 0 3 was used as a source of thallium and Xa2EDTA and N a O H were used. The presence of sodium did not interfere with the growth of MgTlP04-6HzO or any of the other struvite analogs and Na2EDTA can replace the MzEDTA. X-Ray powder patterns were taken on a Norelco powder diffractometer with monochromated C u KO. radiation with KC1 as an internal standard. Infrared spectra were taken on a Perkin-Elmer Model 521 spectrometer with the sample in a KBr disk. Crystal densities were measured either by pycnometric means or by the sink-float method.13 Chemical analyses were performed by Galbraith Laboratories Inc., Knoxville, Tenn. Crystal size and perfection can be optimized by varying the conditions described above. Table I shows the best conditions tried for each material and the results obtained.
111. Crystallographic Properties
Crystals of struvite occurred in both wedge-shaped prisms and needles. Twins on (001) such as described by Palache et al.3 are frequently seen. Both M g K P 0 ~ 6 H 2 0and MgRbP04.6H20 were seen only in needle form. MgTlP04.6H20 grew in wedge-shaped, distinctly struvite-like crystals and in other shapes. Crystals of MgCsPOk6H20 were capped hexagonal prisms or trigonal pyramids as described by Ferrari et al.9,lO All crystals were stable for short periods when taken from their moJher liquor except MgRbP04.6H20 which clouded easily. Struvite crystals may be stored in a capped bottle indefinitely but all other crystals showed a tendency to hydrolyze to a greater or lesser extent over long periods of time. However, the NH4+, T1+, and Cs+ crystals showed a greater degree of stability than the K+ or Rb+ crystals. Table I1
Inorganic Chemistry, Vol. 14, No. 7, 1975 1635
Crystal Chemistry of Struvite Analogs Table 1 Compd
Gel s o h
Top soln
0.05 M MgSO, 0.04 M K,EDTA pH 10 KOH 0.010 M MgSO, 0.005 M Rb,EDTA pH 10 RbOH 0.05 M MgSO, 0.02 M Cs,EDTA pH 10 CsOH 0.05 M MgSO, 0.04 M (“,),EDTA pH 10 ”,OH 0.05 M MgSO, 0.04 M Na,EDTA pH 10 NaOH
MgKP04.6H, 0 Mg RbPO, .6 H, 0 MgCsPO,.GH,O MgNH,PO, .6H, 0 MgT1P0,.6H2 0
Remarks
0.05 M K,HPO, pH 10 KOH
Needles up to 1 cm
0.010 M Rb,HPO, pH 10 RbOH
Needles up to 1 cm
0.05 M Cs,HPO, pH 1 0 CsOH
Hexagonal pyramids or pyramidal prisms up t o several mlllimeters Needles up to 3 ern or prisms up to 5 mm
0.05 M (NH,),HPO, pH 10 “,OH 0.05 M Na,HPO, 0.05 M TlNO, pH 10 NaOH
Wedge-shaped prism up to 5 mm
Table 11. Crystallographic Properties
Compd
System
a, A
b, A
c, A
2
Ionic radius ofM+? A
MgKP0;6HZO MgT1POd.6H,0 Mg(NH, jPO,-.6H, 0
Orthorhombic Orthorhombic Orthorhombic
6.16’ 6.135 6.14 (6.14)‘ 6.177
1.33 1.44 1.48
1.88 3.00 1.71
1.91’ 2.99
Pm2,n Pm2, n ~m2;n
Orthorhombic (triclinic?) Hexagonal
11.09’ 11.35 11.21 (11.21)‘ 11.27
2 2 2
MgRbP0,.6H,O
6.87’ 6.861 6.95 (6.945)‘ 6.852
2
1.48
2.18
2.15
Pm2,n?
11.99 (11.99)d
2
1.69
2.40
2.42 (2.43)d
P 6 rnc
MgCsPO, .6H, 0
Cubic
6.899 (6.939)d 10.02
4
hkl
do
d,
III,
hkl
do
001 110 020 011 101 111 021 121 200 130 031 012 131 211 040 102 022 221 041
6.16 5.88 5.70 5.42 4.58 4.24 4.17 3.56 3.43 3.31 3.22 2.964 2.928 2.893 2.838 2.801 2.701 2.647 2.569
6.14 5.87 5.68 5.40 4.57 4.24 4.17 3.56 3.43 3.31 3.22 2.961 2.915 2.895 2.838 2.800 2.699 2.648 2.575
10 100 10 60 50 55 60 65 10 50 20 30 10 25 10 10 20 10 3
122 141 032 231 212 240 150 051 003 151 321 232 023 060 331 160 061 203 133
2.510 2.409 2.380 2.348 2.239 2.181 2.151 2.128 2.045 2.031 2.004 1.954 1.925 1.891 1.860 1.824 1.804 1.756 1.740
d,
2.511 2.411 2.383 2.348 2.241 2.187 2.155 2.129 2.045 2.033 2.005 1.957 1.924 1.892 1.865 1.824 1.808 1.757 1.740
Space group
d,,gml-’
2.38
a A. F. Wells, “Structural Inorganic Chemistry”, 3rd ed, Oxford University Press, London 1967, p 71. card 20-685. References 9 and 10. JCPDS powder diffraction file card 15-762.
Table 111. Powder Diffraction Data for MgT1P0,.6H,0a
d,,! ml-
F43m
’JCPDS powder diffraction file
Table IV. Powder Diffraction Data for MgRbP0,.6H,0a
I/Io
hkl
do
d,
10 5 5 5 10 3 3 3 3 5 5 10 5 3 3 3 3 3 3
110 020 011 101 111 021 121 200 130 031 012 211 040 022 221 041 122
5.87 5.62 5.43 4.60 4.25 4.17 3.56 3.43 3.30 3.22 2.974 2.897 2.824 2.710 2.645 2.569 2.517
5.86 5.64 5.42 4.59 4.25 4.16 3.56 3.43 3.29 3.21 2.979 2.896 2.818 2.708 2.645 2.563 2.519
Orthorhombic: a = 6.861 (5), b = 11.35 (2), c = 6.135 (5) A .
compiles the crystallographic properties of the struvite analogs as determined in this work and elsewhere. Struvite and M g K P 0 ~ 6 H 2 gave 0 X-ray powder patterns which agree well with JCPDS powder diffraction cards 15-762 and 20-685, respectively. M g T l P 0 4 ~ 6 H 2 0gave a powder pattern which can be indexed on an orthorhombic cell with a = 6.861, b = 11.35, and c = 6.135 A as s h o w n in Table 111. Table IV shows the powder pattern obtained for MgRbPOb6H20 which can also be indexed on an orthorhombic cell with u = 6.852, b = 11.27, and c = 6.177 A. Some very weak ( I l l 0 < 5) lines were seen which could not be indexed on this cell indicating either a second phase such as Mg3(P04)24HzO or a lower symmetry for M g R b P 0 ~ 6 H 2 0 .The latter explanation is supported by infrared evidence discussed later on.
III, 15 5 30 40 100 80 25 35 40 15 35 100 70 50 35 5 30
,
hkl
do
d,
111,
141 032 231 132 003 013 232 060 123, 331 242 213 400 350 261 162,170 024 153
2.402 2.386 2.341 2.247 2.059 2.028 1.954 1.878 1.862 1.785 1.742 1.713 1.603 1.589 1.565 1.489 1.484
2.401 2.386 2.342 2.248 2.059 2.026 1.958 1.878 1.861 1.779 1.744 1.713 1.604 1.591 1.563 1.489 1.484
10 10 10 10 5 10 15 5 10 5 10 5 5 5 5 5 5
a Orthorhombic: a = 6.852 (5), b = 11.27 (2), c = 6.177 (5) A An unindexed weak line(s) appears at d = 4.04 A which can be attributed t o Mg,(PO,), .4H,O.
Table V. Powder Diffraction Data for Hexagonal MgCsP0,.6H,0a hkl
do
d,
III,
hkl
do
010 011 012 110 111 020 021 022 023 120 121
5.99 5.36 4.23 3.46 3.32 2.984 2.904 2.671 2.390 2.259 2.220
5.98 5.35 4.23 3.45 3.32 2.988 2.899 2.675 2.394 2.259 2.220
20 100 40 70 40 60 20 30 10 10 10
122 030 031 025 220 034 132 133 224 134 231
2.11 1.993 1.963 1.865 1.725 1.658 1.595 1.529 1.493 1.448 1.360
“ a = 6 . 8 9 9 (5),c=11.99 (2)A.
d,
2.114 1.992 1965 1.871 1.725 1.659 1.598 1.531 1.495 1.451 1.362
III, 5 10 20 20 10 5 10 3 3 3 3
1636 Inorganic Chemistry, Vol. 14, No. 7 , 1975
Banks, Chianelli, and Korenstein
Table VI. Powder Diffraction Data for Cubic MgCsP0,.6H20 hkl
do
d,
IiI,
hkl
do
d,
111,
111 200 220 300 311
5.80 5.01 3.55 3.26 3.03
5.78 5.01 3.54 3.34 3.02
30 100 35 10 40
400 331 442 511,333 440
2.504 2.305 2.046 1.929 1.776
2.504 2.298 2.045 1.928 1.771
100 10 5 10 5
Table VII. Chemical Analyses MErTI0.3, MgTlPO,. (NH,)0,65P04. 6H,O 6H,O ___Theor Exptl Theor Exptl Theor Exptl Theor Exptl
MgKPO,, 6H,O
MgRbPO,. 6H,O
9.13 9.32 7.78 7.69 5.65 5.35 7.74 6.92 14.68 14.87 27.33 27.14 47.22 42.15 23.03 21.75 %P 11.63 11.74 9.91 9.79 7.18 8.63 11.29 9.51 %H,O 40.54 39.35 34.53 33.90 25.00 24.95 40.65 37.92
%Mg
%M
Table VIII. Infrared Spectra of Struvite MgNH4PO;6H,0 Band. cm-’ 3700-2500 3500
Intens
Assignment
1800-1500
Strong, broad Water vI -up symPeak on 3700-2500 cm-l, antisym str, NH,’ broad ul - u j sym-antisym str Peak on 3700-2500 a n - ’ , broad Peak on 3700-2500 cm“, broad Medium, broad Water-phosphate H bonding Weak. broad Water u,(H-0-H) def +
1410 1430 1390 1010 880
Weak, sharp Medium, sharp Shoulder Very strong, sharp Weak, broad
3250 2900
MgRb PO4 6 H20 I
2500-2200
v2 (SH,*)
MgCsP04 6H2O
750 570 450
MgTIP04 6 H z O
Figure 1. Crystals of struvite MgNH,PO4,6H,O and its Rb, Cs, and T1 analogs.
Table V lists the powder pattern for MgCsPOk6H20 which can be indexed on a hexagonal cell with a = 6.899 and c = 11.99 8,. The a axis is somewhat smaller than that reported by Ferrari et a1.9.10 The first product of the MgCsPOc6H20 crystal growth experiments yielded a powder pattern composed of the lines reported in Table V plus the lines reported in Table VI. When the experiment was periormed at 4’ only the lines appearing in Table V were seen. Subtracting the lines for the hexagonal MgCsP04.6H20 resulted in the powder diffraction pattern appearing in Table VI. This pattern could be indexed on a cubic cell with a = 10.02 ( 2 ) 8,. The cubic MgCsP04.6H20 is the analog of MgCsAsOc6HzO with a = 10.18 (1) 8, which was reported by Ferrari et al.9.10 They also discussed the structure of this cubic material which has the As043- group located on the body diagonal of the cube. The conditions for obtaining the pure cubic form have not been established but it appears to be a higher temperature form. The structural relation between struvite-like materials has
Weak, sharp Strong, sharp Weak
been discussed by Dickens et a1.8 The structures of the orthorhombic, hexagonal, and cubic materials discussed above are closely related. The magnesium atom is surrounded by an octahedron of water molecules. The difference in the lattice types of these materials is governed by the size of the alkali or “pseudoalkali” ion. For K, T1: and NH4 the orthorhombic struvite structure is the most stable. For cesium the higher symmetry hexagonal and cubic structures are preferred. The lower stability and more complex powder pattern of the R b analog suggest that it has a transitional structure of perhaps lower symmetry. The possibility of mixed-alkali struvite analogs seems likely and this has been confirmed for the ammonium ion, as discussed below. Polarizing microscope studies confirmed the crystallographic assignments described above. S H G (second harmonic generation) measurements with a neodymium glass laser gave positive results indicating acentric space groups for all the struvite analogs. This is in agreement with the X-ray and piezoelectric results of Whitaker and Jeffery,5,6 who reported an acentric space group for struvite. ___ __ .--7
~-
Figure 2. Infrared spectrum of MgNH,PO4.6H,0.
NH,’ v q asym bending split by “restrictive rotation” u , ( P O , ~ - ) antisym str Ammonium-water H-bonding? Water-water H bonding u4(POq3-)P - 0 bend v2 PO,^-)
8
9 10 -__
12
15
._.___.. --i+II-IT--T-
7
20 7
30 40 ~. ,a .
Inorganic Chemistry, Vol. 14, No. 7 , 1975 1637
Crystal Chemistry of Struvite Analogs WAVELENGTH MICRONS
3
25
5
4
7
6
8
9 1 0
12
20
15
3040
I
I
I
I
' --I
d I
.
.
,
I
- 4
I
L
_ I
-
--
. Thrasher, Tenn. Val. Auth., Chem. Eng. Bull., No. 6 (1967). B. Dickens and W. E. Brown, Acta Crystallogr., Sect. B, 25, 1159 (1972). A . Ferrari, L. Cavalca, and M. Nardelli, G a m Chim. Ital., 85, 169 (1955). A. Ferrari, L. Cavalca. and M. Nardelli, Gazz. Chim. Ital., 85, 1232 ( 1955). E. Banks, R. Chianelli, and F. Pintchovsky, J. Cryst. Growth, 18, 195 (197.3).
E. Banks and R.Chianelli, J . Appl. Crystallogr., 7, 301 (1974). “International Tables for X-Ray Crystallography”, Vol. JII, Kynoch Press, Birmingham, England, 1968, pp 17-1 9. R. C. Plumb and D. F. Hornig, J. Chem. Phys., 21, 366-367 (1953). H. A. Levy and S. W. Peterson, J. Chem. Phys., 21, 366 (1953).
Contribution from the Laboratorio C N R and Istituto $i Chimica Generale e Inorganica dell’universita di Firenze, 501 32 Florence Italy
Single-Crystal Polarized Electronic Spectra of the Pentakis( 2-picoline N-oxide)cobalt(II) Perchlorate Complex I. BERTINI,* P. D A P P O R T O , D. G A T T E S C H I , and A. S C O Z Z A F A V A Received M a y 29, 1974 AIC403455 Single-crystal polarized electronic spectra of the pentakis(2-picoline N-oxide)cobalt(II) perchlorate complex, [Co(C6H7NO)s](C104)z, have been recorded for a crystal modification, the structure of which has been determined. The crystals are monoclinic, space group P 2 1 / c ,with cell dimensions a = 10.223 (3) A,b = 9.659 (3) A,c = 38.195 (12) A,p = 107.92 ( 3 ) O , and Z = 4. The structure was refined to an R factor of 0.076. Assignment of the transitions on the basis of a C2> symmetry is proposed and the energies of the electronic levels are discussed in terms of ligand field and angular overlap parameters.
Introduction I n the framework of a research program based on single-crystal spectra tending to test the validity of ligand field models for low-symmetry chromophoresl-3 it seemed interesting to investigate the pentakis(2-picoline N-oxide)cobalt(II)
perchlorate complex4 ( c o o s ) which is reported to be approximately trigonal bipyramidal.5 The fact that the donor atoms are five oxygens belonging to five equal ligands should simplify the problem of interpreting the spectra and should therefore give more information on the ligand ability of pyridine
