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Novel Clusters of Transition Metals and Main Group Oxides in the AlkylamineOxovanadiumBorate System.

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~~
1161 Data obtained for RG, shows a larger error due to the large size of the molecule.
[17] K. Wuttrich, N M R of Proteins and Nucleic Acids, Wiley, New York, 1986,
chap. 6.
[18] For a two-spin system with atoms 1 and 2, the cross relaxation constant r , 2and
rotation correlation time rc are related as in Equation (1). Isotropic tumbling
and pure dipole-dipole relaxation are assumed po = dielectric constant,
,; = gyromagnetic constant, r = distance between atoms 1 and 2. and
w = Larmor frequency. Measurements were conducted with a 400 MHz instrument.
[19] T. L. James, G. B. Matson, I. D. Kuntz, J. Am. Chem Soc. 1978. 100. 35903594.
Novel Clusters of Transition Metals
and Main Group Oxides in the
Alkylamine/Oxovanadium/Borate System
Job T. Rijssenbeek, David J. Rose,
Robert C. Haushalter,* a n d Jon Zubieta*
Dedicated to Professor Hans Georg von Schnering
on the occasion of his 66th birthday
Hydrothermal synthesis is an area of rapidly increasing importance for the synthesis of new and structurally complex,
hybrid, organic-inorganic, solid-state compounds. Utilizing
the ability of polar organic molecules to direct the crystallization of inorganic frameworks by incorporation in a geometrically specific manner through multipoint hydrogen bonding, we
have been able to prepare several new classes of materials. Presynthesized organic molecules were used to imprint structural
information onto inorganic oxide lattices, and microporous
solids with the largest cavities and lowest framework densities
known,['] lamellar transition metal oxides or phosphates with
organic cations[2]or coordination compounds[31between the
layers, polyoxometalates linked by coordination compounds
into 2-D and 3-D
materials with interlaced I-D
organic and inorganic chains,['] and organically templated transition metal halides[61have all been made. Even polyoxometalate metal species,"] including the unusual [H16(V02)16(CH,P0,),]8- ,Is1 have been synthesized by hydrothermal synthesis. We report here the use of this technique for the synthesis
of 1 and 2 (en = ethylenediamine), which represent a novel type
[*] Dr. R. C. Haushalter, J. T. Rijssenbeek
NEC Research Institute
4 Independence Way
Princeton, NJ 08540 (USA)
Fax: Int. code +(609)951-2483
[**I
Prof. J. Zubieta, D. J. Rose
Department of Chemistry
Syracuse University
Syracuse, NY 13244 (USA)
Fax: Int. code +(315)443-4070
e-mail: jazubiet~~marlbox.syr.edu
The work at Syracuse University was supported by the U. S. National Science
Foundation (grant no. 9318824).
1008
0 VCH Verlagsgesellsehaf[mbH. 0-69451 Weinheim, I997
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of clusters of transition metals and main group oxides in the
organic cation/vanadium/borate system and possess unprecedented structures. Although a large number of borate mineral
structures are known,''' and substantial progress has been
made in classifying and understanding their structures, synthetically prepared and structurally characterized examples are
rare.I'o.
111
The general procedure for preparing 1 and 2, as well as other
vanadium borate
consists of concentrated hydrothermal treatment of a vanadium oxide source (V,O, or
V,O,) with B,O, or H,BO, and amine at 170 "C in water. Large,
structurally complicated, highly crystalline clusters spontaneously form in good yield from these simple starting materials
and synthetic conditions.
The structure of the V,,B,, cluster in l [ I 3 ] contains several
highly interesting features, the most extraordinary of which may
be the contorted vanadium oxide ring (Figure la). The ring can
be described as two semicircles of five trans, edge-sharing VO,
square pyramids that partially interpenetrate-like the seams
on a tennis ball. The four ends of the semicircles connect
through two additional VO, units to form a continuous V,, ring
of unprecedented connectivity (Figure lb). All 12 terminal
vanadyl (V=O) groups radiate away from the cluster surface.
The clefts formed by the ring are occupied by two novel B, and
B, polyborate chains (Figure Ic). The B,O,,(OH), chain is
composed of two linked B,O,(OH) FBBs (fundamental building blocks)[71that are capped on each end by a tetrahedral
BO,(OH) group. The second chain, B,O,,(OH),(enH), retains
the approximate shape of the first. However, the OH groups on
the terminal boron atoms have been replaced by a pendant,
planar BO(OH), triangle on one end and an enH+ molecule on
the other to give a tetrahedral BO,N coordination environment
(Figure la). The interior cavity of the cluster is occupied by
poorly defined electron density, probably due to an occluded
H,O molecule. The intercluster space is filled by enH:+ and
water molecules.
The V,,B,, cluster in 2[14] consists of a puckered
B,,O,,(OH), ring sandwiched between two triangles of six alternating cis and trans, edge-sharing vanadium atoms. Each
vertex of this novel triangular metal-0x0 moiety contains a cis,
edge-sharing VO, square pyramid, whereas the midpoint of
each edge is occupied by a trans, edge-sharing VO, polyhedron
(Figure 2a-c). Again, all the vanadyl groups radiate away from
the cluster surface. The BI8ring (Figure 2d,e) is composed of six
B,O,(OH),- FBBs and exists in a cyclohexane-like chair conformation with a B, unit at each of the six vertices. The two V,
triangles are coordinated to each face of the B,, ring through six
"axial" B-0-V bonds and three B2-(p,-O)-V bonds. On average,
ten of the twelve vanadium atoms per cluster are V", and two
are Vv; this accounts for the dark red color of the crystals. The
V oxidation states were determined by considering the other
known charges present in the unit cell and confirmed by valence
bond calculations,[' which show a valence of about + 4.22 for
each V atom. This value is close to the +4.17 expected for a
V" :Vv ratio of 5 : 1, and it appears that each vanadium site has
an equal possibility of containing a Vs+ ion.
Consistent with the fact that borate minerals are often found
in dry 1akebeds,[l61the borate starting material remains in solution if too much water is present during the synthesis of these
oxovanadium borates, and single crystals of layered vanadium
oxidesr2]are formed. We have observed, in this and other hydrothermal metal oxide systems, that the presence of a small
amount of dissolved borate (from B,O, or H,BO,) greatly enhances the dissolution of the starting materials and very favorably affects the subsequent crystallization of the metal oxide.
0570-08331Y7/3609-1008$ I7.50+ .SO10
Angeuz.Chem. Int. Ed. Engl. 1997. 36, No. 9
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Figure 1. Views of cluster 1: a) entire cluster; b) the “contorted’’ V,, ring; c) ball-and-stick model of the two coordinated polyborate chains
Thus, the mineralizing effect of the boron oxides could
lead to larger, more perfect single crystals of such compounds.
The facile, high-yield preparation of these structurally and
compositionally unprecedented vanadium borate clusters again
points out that hydrothermal synthesis is a particularly useful,
and increasingly important, method for preparing new compounds. The two examples discussed here and others“’] show
that novel, unpredicted transition metal 0x0 clusters and main
group polyanions can be easily accessed within this vanadium/
borate system. The ease with which the borates attack and solubilize relatively unreactive transition metal oxides a t low temperatures, combined with the large phase space associated with
the highly specific. structure-directing nature of the organic
cation, portends a very rich chemistry of structurally complex,
kinetically metastable compounds.
Angeii~Clzem. lni. E d D i R I . 1997. 36, N o . 9
Experimental Section
Syntheses were conducted in acid-digestion bombs lined with polytetrafluorethylene
(23 mL) and filled to about 8 % at room temperature. The borate was added first
followed by the vanadium source, water, and the amine. The reaction conditions
typically resulted in a pH value of 8-9.
1: A mixture of B,O, (0.278 g). V,O, (0.075 g), H,O (1 mL). and en (0.061 g) in a
molar ratio of 8 : l : 11 1 :2 was heated at 170°C for 72 h to give a nearly pure phase
of orange crystals. The product was thoroughly cleaned by repeated cycles of immersion in an ultrasonic bath and washing with water. Yield: 0.1316 g.
2: A mixture of H,BO, (0.500 g), V,O, (0.182 g), H,O (1 mL). and en (0.061 g) in
a molar ratio of 8.1 : 55.1 was heated at 170 “C for 190 h t o give a mixture of very
dark red and pale orange crystals (about 20: 1 by visual inspection). The product
was cleaned by repeated cycles of immersion in a n ultrasonic bath and washing with
water. Yield: 0.329 g.
Received: November 4. 1996 [Z97231E]
German version: Angew. Chem. 1997. 1UY. 1049-1052
Keywords: boron - clusters hydrothermal synthesis - polyoxometalates vanadium
VCH Verlugsgesellschafi mbH, D-69451 Wemheim, 1997
0570-0833/97/36OY-l009S. 17.50+ .50/0
1009
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Flgure 2. Views ofcluster 2: a) parallel and b) perpendicular to the noncrystai~ographic,psuedo-threefold axis; c) the V, ring and d) the B,, ring along the pseudo-threefold
axis: e) side view of the B,, ring.
[ I ] M. 1. Khan. L. M. Meyer, R C. Haushalter. A. L. Schweitzer. J Zubieta. J. L.
Dye. Chrin. Muter.. 1996, 8. 43.
[2] Y. Zhang, R C. Haushalter. A. Clearfield. Inorg. Cheni. 1996, 35, 4950; Y.
Zhang. C. J. O‘Connor. A. Clearfield. R. C Haushalter. CIiwn. Mnter 1996.8,
155.
[3] Y. Zhang. J, R. D. DeBord, C. J. OConnor. R. C. Haushalter. A. Clearfield, J.
Zuhieu, A n p n Clrern. 1996. 108, 1067; Angelic Cliem. Inf. E d E i i ~ l 1996.35,
.
989.
[4] Y. Zhang, L. Meyer, R. C. Haushalter, J. Zubieta, Inorg Chim.Acta, in press.
[51 D. Hagrman. C. Zubieta, R. C. Haushalter, J. Zubieta, A n ~ e w .Cbeni. 1997,
109, 904: A n p r . . Chem. Int. Ed. Engl. 1997. 36, 873
[6] J. DeBord. Y.-J. Lu. C. J Warren. R. C. Haushalter. J. Zubieta, Chem. Commw.
submitted.
171 M . T. Pope, A. Miiller. Angeiv Chem 1991, 103. 56, Angew. Clrein. Inf. E d
Engl. 1991. 30. 34.
181 G. H u n , A J. Jacobson. V. W. Day, Angeii,. Chem 1991, 103. 426. A n g w
Chiw?.f n l . EX EngI. 1991. 30, 422.
[9] 1’. C. Burns. J. D Grice. F. C . Hawthorne. Cun. Mineral. 1995. 33,1 1 31. and
references therein.
[lo1 P. 1). Thompson. D. A. Keszler. Clirrn. Muter. 1994, 6,2005: J. R. Cox. D. A.
KesAer. J. Hudng. ihrd. 1994.6.2008. H. Behm, Actn Crwfallogr.SEN C 1985,
41, 64’7. H Behm. ihid 1983. 3Y. 20.
111) C. L. Christ, J. R. Clark, Phqs. Chem. Minerals 1977, 2, 59; G. Heller, J.
Pickardt. 2. Narurforsch. B 1985,40,462; W. T. A. Harrison, T. E. Gier, G. D.
Stucky, Angels. Chem. 1993, 105, 788; Angeiv. Chrm. Int. Ed. Engl. 1993,32,
724.
[12] C. J Warren, J. T Rijssenbeek, D. J. Rose. R. C. Haushalter, J. Zubieta, CIiem.
Conimun. submitted.
1131 Crystal data for 1 [14b]: triclinic, P i , a =12.48110(10), b =13.9567(2), c =
21.8689(2)A, 1 = 97.3211(10), D = 98.4310(2), 7 =114.1520(1)”. Z = 2,
T = 2 0 ’ C , pErlcd= 2.182 gem-'; 9610 reflections with 1>2u(I) and 927
parameters, R = 0.0617.
114) a) Crystal data for 2 : monoclinic, C2/c, a = 22.4213(5), h = 15.3560(3),
c = 22.0391(5) A, D =106.792(1)’, 2 = 4 T = 20°C. pc*tLd
= 2.067 gcm-’;
5195 reflections with I > Z n ( I ) and 479 parameters, R = 0.0625. b) Further
details of the crystal structure investigations may be obtained from the Fachinforrnationszentrum Karlsruhe. D-76344 Eggenstein-Leopoldshafen (Germany). on quoting the depository numbers CSD-406 454 (1) and CSD-406455.
[IS] 1. D. Brown. K. K. Wu, Acra Crmfallogr. Sect. B 1976, 32, 1957.
[I61 W. A. Gale in Boron. Metallo-Boron Compounds, and Boranes (Ed.: M.
Adams). Wiley. New York, 1964, p. 1
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