Structural motifs in (t-butoxy)zirconium phosphinates, arsinates, and phosphates

Article abstract of DOI:10.1021/ic034458o

Reaction of zirconium tetrakis(tert-butoxide) (1) with dicylohexylphosphinic acid in toluene leads to the dinuclear compound [Zr(μ,μ′-O₂P(cycl-C₆H₁₁) ₂)(O-t-Bu)₃]₂ (2) in which the zirconium is pentacoordinated. An analogous reaction using diphenylphosphinic acid in tetrahydrofuran also leads to a dinuclear complex [Zr(μ,μ′-O ₂PPh₂)(THF)((O-t-Bu)₃]₂· C₆H₅CH₃ (3·C₆H ₅CH₃), in which zirconium is hexacoordinated. A novel exchange of tert-butoxy and phenoxy groups occurs when 1 is treated with diphenyl phosphate [(PhO)₂PO₂H] leading to the isolation of the exchange product [Zr{μ,μ′-O₂P(O-t-Bu)(OPh)}(μ -OPh)(O-t-Bu)₂]₂ (4). In contrast to the above, trinuclear zirconium compounds Zr₃(μ,μ′-O ₂AsMe₂)₂(μ₂,μ′-O ₂AsMe₂)(O-t-Bu)₇(μ-O-t-Bu)₂ (5) and Zr₃(μ,μ′-O₂P(O-t-Bu)₂) ₅(O-t-Bu)₇·1/2C₆H₅CH ₃ (6·1/2C₆H₅CH₃) have been isolated from the reaction of 1 with cacodylic acid and di-tert-butyl phosphate, respectively. The X-ray structures of 2, 3, 5, and 6 have been determined; although the X-ray structural analysis of 4 could not be satisfactorily finished, it reveals the disposition of the substituents. The solution state NMR data suggest that these compounds undergo structural changes in solution. Possible relationships among the various structures are discussed.

Full text of DOI:10.1021/ic034458o

Inorg. Chem. 2003, 42, 5837
Structural Motifs in (t-butoxy)Zirconium Phosphinates, Arsinates,
and Phosphates†
,‡
,§
K. C. Kumara Swamy,* Michael Veith,* Volker Huch,§ and Sanjay Mathur
School of Chemistry, UniVersity of Hyderabad, Hyderabad- 500046, India, Anorganische Chemie,
Fachbereich 8.11, UniVersita¨t des Saarlandes, Geba¨ude 23, Postfach 151150,
D-66041 Saarbru¨cken, Germany, and CVD DiVision, Institut fu¨r Neue Materialien, Im Stadtwald,
Geba¨ude 43, 151150, D-66041 Saarbru¨cken, Germany
Received April 30, 2003
Reaction of zirconium tetrakis(tert-butoxide) (1) with dicylohexylphosphinic acid in toluene leads to the dinuclear
compound [Zr(µ,µ′-O P(cycl-C H ) )(O-t-Bu)3]2 (2) in which the zirconium is pentacoordinated. An analogous reaction
2
6 11 2
using diphenylphosphinic acid in tetrahydrofuran also leads to a dinuclear complex [Zr(µ,µ′-O PPh2)(THF)((O-t-
2
Bu)3]2‚C H CH (3‚C H CH ), in which zirconium is hexacoordinated. A novel exchange of tert-butoxy and phenoxy
6
5
3
6
5
3
groups occurs when 1 is treated with diphenyl phosphate [(PhO)2PO H] leading to the isolation of the exchange
2
product [Zr{µ,µ′-O P(O-t-Bu)(OPh)}(µ-OPh)(O-t-Bu)2]2 (4). In contrast to the above, trinuclear zirconium compounds
2
Zr3(µ,µ′-O AsMe2)2(µ2,µ′-O AsMe2)(O-t-Bu)7(µ-O-t-Bu)2 (5) and Zr3(µ,µ′-O P(O-t-Bu)2)5(O-t-Bu)7‚1/2C H CH (6‚1/
2
2
2
6
5
3
2C H CH ) have been isolated from the reaction of 1 with cacodylic acid and di-tert-butyl phosphate, respectively.
6
5
3
The X-ray structures of 2, 3, 5, and 6 have been determined; although the X-ray structural analysis of 4 could not
be satisfactorily finished, it reveals the disposition of the substituents. The solution state NMR data suggest that
these compounds undergo structural changes in solution. Possible relationships among the various structures are
discussed.
Introduction
characterized by X-ray crystallography. On the basis of NMR
studies, it has been suggested that the structure of I is
dynamic in solution although the exact nature of the species
In recent years there has been a burgeoning interest in
molecular alkoxy-titanium and -zirconium phosphates and
phosphonates which in part is due to the possible use of these
compounds as precursors to solid-state materials.1,2 The
usefulness of metal alkoxides/phosphates as relevant to
material science is well-known,3 and in this connection we
have been looking for the possibility of using some of these
products in chemical vapor deposition (cvd) processes.4 Two
reactions which attracted our attention were those of Ti(O-
i-Pr)4 with (t-BuO)2P(O)OH1f and Zr(O-i-Pr)4(i-PrOH)2 with
Ph2P(O)OH5 wherein compounds I and II, respectively, were
(1) (a) Inorganic Ion Exchange Materials; Clearfield, A., Ed.; CRC
Press: Boca Raton, FL, 1982. (b) Alvarez, C.; Llavona, R.; Garcia, J.
R.; Suarez, M.; Rodriguez, J. Inorg. Chem. 1987, 26, 1045. (c)
Errington, R. J.; Ridland, J.; Willett, K. J.; Clegg, W.; Coxall, R. A.;
Heath, S. L. J. Organomet. Chem. 1998, 550, 473. (d) Wang, B.;
Greenblatt, M.; Wang, S.; Hwu, S. Chem. Mater. 1992, 5, 32. (e)
Thorn, D. L.; Harlow, R. L. Inorg. Chem. 1992, 31, 1138. (f) Lugmair,
C. G.; Tilley, T. D. Inorg. Chem. 1998, 37, 1821. (g) Guerrero, G.;
Mehring, M.; Mutin, P. H.; Dahan, F.; Vioux, A. J. Chem. Soc., Dalton
Trans. 1999, 1537. (h) Guerrero, G.; Mutin, P. H.; Vioux, A. Chem.
Mater. 2000, 12, 1268. (i) Clearfield, A.; Sharma, C. V. K.; Zhang,
B. (P) Chem. Mater. 2001, 13, 3099 (review).
(2) (a) Clearfield, A. Chem. Mater. 1998, 10, 2801. (b) Horne, J. C.;
Huang, Y.; Liu, G.-Y.; Blanchard, G. J. J. Am. Chem. Soc. 1999, 121,
4419. (c) Horne, J. C.; Blanchard, G. J. J. Am. Chem. Soc. 1999, 121,
4427.
(3) Selected recent references: (a) Lugmair, C. G.; Tilley, T. D.;
Rheingold, A. L. Chem. Mater. 1999, 11, 1615. (b) Yonezawa, T.;
Matsune, H.; Kunitake, T. Chem. Mater. 1999, 11, 33. (c) Murugavel,
R.; Sathiyendran, M.; Walawalkar, M. G. Inorg. Chem. 2001, 40, 427.
(d) Fujdala, K. L.; Tilley, T. D. J. Am. Chem. Soc. 2001, 123, 10133.
(e) Sathiyendiran, M.; Murugavel, R. Inorg. Chem. 2002, 41, 6404.
* Corresponding authors. K.C.K.S.: e-mail, kckssc@uohyd.ernet.in; fax,
+91-40-3012460. M.V.: e-mail, veith@mx.uni-saarland.de; fax, 0681-302-
3995.
† The synthetic part (K.C.K.S.) of the experimental work was done at
Saarbru¨cken (University of Saarlandes) during May-August 2000 with
support from the Alexander von Humboldt foundation.
‡ University of Hyderabad.
§ Universita¨t des Saarlandes.
Institut for Neue Materialien.
10.1021/ic034458o CCC: $25.00 © 2003 American Chemical Society
Published on Web 08/19/2003
Inorganic Chemistry, Vol. 42, No. 19, 2003 5837

Kumara Swamy et al.
could not be ascertained. The zirconium compound II might
be considered to be an intermediate in the formation of the
dimer [Zr(µ,µ′-O2PPh2)(O-i-Pr)3]2, a species analogous to I.
Thus, even in the 1:1 stoichiometric reaction of M(OR)4 [M
) Ti, Zr, Hf] with monobasic phosphinic/arsinic acids of
type R2P(O)OH or R2As(O)OH depending on steric and
electronic requirements, it is likely that diverse products
could be obtained and it is this aspect which we planned to
address in our studies. This is also in consonance with the
experience in the chemistry of tin(IV), an element of group
14, wherein subtle variations in the substituents on phosphorus/
arsenic stabilized different structural forms like cubane,
hexagonal prismane (drum), O-capped trinuclear clusters,
etc., for the monorganotin(oxo) phosphinates/phosphates/
arsinates, suggesting that structural analogies could be
productive in developing the cage chemistry of Ti and Zr,
which belong to group 4.6 In this paper, we report charac-
terization of compounds [Zr(µ,µ′-O2P(cycl-C6H11)2P)(O-t-
Bu)3]2 (2), [Zr(µ,µ′-O2PPh2)(THF)(O-t-Bu)3]2‚C6H5CH3 (3‚
C6H5CH3), [Zr{µ,µ′-O2P(O-t-Bu)(OPh)}(µ-OPh)(O-t-Bu)2]2
(4), and Zr3(µ,µ′-O2AsMe2)2(µ2,µ′-O2AsMe2)(O-t-Bu)7(µ-O-
t-Bu)2 (5), all of which contain an equal number of zirconium
and phosphorus/arsenic centers, but provide a structural
variety that should be useful in further analyzing their
hydrolysis/thermolysis products for future applications. In
addition, we also report the synthesis and structure of Zr3-
(µ,µ′-O2P(O-t-Bu)2)5(O-t-Bu)7 (6‚1/2C6H5CH3). All of these
have been prepared by starting with Zr(O-t-Bu)4 (1).4b,7
Whereas 2 has a structure analogous to the titanium
compound I, compound 3 has hexacoordinated zirconium
atoms with two symmetrically bridging diphenylphosphinate
residues unlike structure II. Compounds 5 and 6 are unique
in that they are trinuclear with unsymmetrical arsinate/
phosphate bridges, albeit the fact that the empirical formula
is still retained. In 4, although we started with diphenyl
phosphate, there has been an exchange of one of the phenoxy
groups on phosphorus by a tert-butoxy group with concomi-
tant transfer of the phenoxy group to zirconium.
reference compound, it was not possible to predict the
exchange of the phenoxy and tert-butoxy groups by means
of the spectral features. Exchange of phenoxy groups in
(PhO)2PO2H with tert-butoxy groups did not take place in
the presence of catalytic amounts of Zr(O-t-Bu)4. Thus, it
appears that initially a dimer similar to 2 had formed which
then underwent ligand reorganization; species III is a
possible intermediate.
Results and Discussion
The reaction of 1 with (C6H11)2PO2H, Ph2PO2H, (PhO)2-
PO2H, or Me2AsO2H gave products 2-5, all with 1:1 ratios
of Zr:P or Zr:As. The spectra recorded in C6D6 solutions
changed over a period of several days, suggesting that there
is a dynamic equilibrium in solution as observed for I by
Tilley and co-workers.1f In the case of 4, due to lack of a
(4) (a) Veith, M. J. Chem. Soc., Dalton Trans. 2002, 2423. (b) Veith,
M.; Mathur, S.; Huch, V.; Decker, T. Eur. J. Inorg. Chem. 1998, 1327
(µ2- and µ3-tert-butoxy-bridged zirconium compounds).
(5) Chakraborty, D.; Chandrasekhar, V.; Bhattacharjee, M.; Kra¨tzner, R.;
Roesky, H. W.; Noltemeyer, M.; Schmidt, H.-G. Inorg. Chem. 2000,
39, 23.
(6) (a) Holmes, R. R. Acc. Chem. Res. 1989, 22, 190. (b) Burton, S. D.;
Kumara Swamy, K. C.; Holmes, R. R.; Day, R. O. Phosphorus Sulfur
Silicon 1989, 41, 467 (from proceedings of Fifth International
Conference on Inorganic Ring Systems, Amherst, MA, 1988). (c)
Kumara Swamy, K. C.; Schmid, C. G.; Day, R. O.; Holmes, R. R. J.
Am. Chem. Soc. 1990, 112, 223. (d) Kumara Swamy, K. C.; Day, R.
O.; Holmes, R. R. Inorg. Chem. 1992, 31, 4184. (e) Kumara Swamy,
K. C.; Said, M. A.; Nagabrahmanandachari, S.; Poojary, D. M.;
Clearfield, A. J. Chem. Soc., Dalton Trans. 1998, 1645.
In the synthesis of di-tert-butyl phosphate compound 6‚
1/2C6H5CH3, during the process of workup, some insoluble
material was also obtained; this is most likely the reason for
the observed zirconium-to-phosphate ratio of 3:5 in this
5838 Inorganic Chemistry, Vol. 42, No. 19, 2003

Zirconium Phosphinates, Arsinates, and Phosphates
Figure 1. ORTEP drawing of 2. Hydrogen atoms are omitted and only
selected atoms labeled.
Figure 3. ORTEP drawing of 4. Hydrogen atoms are omitted and only
selected atoms labeled.
Figure 4. ORTEP drawing of 5. Hydrogen atoms as well as the terminal
tert-butoxy carbon atoms are omitted and only selected atoms labeled.
Figure 2. ORTEP drawing of 3‚C6H5CH3. Hydrogen atoms as well as
the solvent are omitted and only selected atoms labeled.
derivative. The solution state NMR spectra of this compound
also changed with time, hampering a detailed assignment of
the signals.
Compounds 2-4 exhibit a single peak in the 31P NMR
(immediately upon dissolution) consistent with the solid-state
structure; in the case of 6, three major signals (∼2:2:1 ratio)
are observed showing that the phosphates are in different
environments, but the exact assignment is difficult. In the
13C NMR of 2 and 3 only one CMe3 signal is observed, as
expected. For 5, the peaks for AsMe2 and C(Me)3 signals
Figure 5. ORTEP drawing of 6‚1/2C6H5CH3. Hydrogen atoms, terminal
tert-butoxy carbon atoms, and the solvent are omitted and only selected
atoms labeled.
1
for 5 are close together both in H and 13C NMR; out of a
maximum of nine OCMe3 signals possible, six distinct peaks
of differing intensities are observed in the 13C NMR for this
compound. This is most likely due to the equivalence of some
of the tert-butoxy groups on the terminal zirconium atoms.
reasonable, as the oxygen bonded to phosphorus is involvedin
further “mesomeric” bonding [i.e. the phosphorus also
competes with Zr for the electron density of oxygen at
P-O(Zr) bond, and hence, the corresponding Zr-O(P) bond
is longer] in contrast to the oxygen connected to the tert-
butyl group. Compound 3 is also a dimer, but here zirconium
is hexacoordinate with the sixth position occupied by a THF
molecule. The Zr-O(THF) distance is longer than Zr-
O(phosphinate) which itself is longer than Zr-O(tert-butoxy)
The molecular structures of 2-6, as revealed by X-ray
crystallography, are shown in Figures 1-5, respectively. In
the case of 4, the structural features are clear despite the
poor quality of the crystals. Compound 2 is a dimer similar
to the titanium compound I, but it should be noted that for
zirconium hexa- or higher coordination is more common and
pentacoordinate compounds with five surrounding oxygens
are rare.8 The geometry around zirconium is that of a heavily
distorted trigonal bipyramid with O(1) and O(4) at the apical
positions. The Zr-O distances to the phosphinate oxygens
are longer than those to the tert-butoxy oxygens. This is
(7) Bradley, D. C.; Thomas, I. M. J. Chem. Soc. 1960, 3857.
(8) Examples in which zirconium is surrounded by only five oxygen are
reported in: (a) Terry, K. W.; Lugmair, C. G.; Tilley, T. D. J. Am.
Chem. Soc. 1997, 119, 9745. (b) Chisholm, M. H.; Huang, J.-H.;
Huffman, J. C.; Streib, W. E.; Tiedtke, D. Polyhedron 1997, 16, 2941.
Inorganic Chemistry, Vol. 42, No. 19, 2003 5839

Kumara Swamy et al.
Table 1. Selected Bond Distances and Angles with Esd’s for Compounds 2-4
3‚C6H5CH3
2
4
Zr-O(1)
Zr-O(2)
Zr-O(3)
Zr-O(4)
Zr-O(5)
1.9700(13)
1.9505(13)
1.9225(15)
2.1656(13)
2.1413(12)
Zr-O(1)
Zr-O(2)
Zr-O(3)
Zr-O(4)
Zr-O(5)
Zr-O(6)
2.2132(18)
2.1836(18)
2.3726(16)
1.9486(17)
1.9522(18)
1.9677(18)
Zr-O(1)
Zr-O(1)′
Zr-O(2)
Zr-O(3)
Zr-O(4)
Zr-O(5)
2.227(4)
2.225(4)
1.918(5)
2.178(5)
2.183(4)
1.920(5)
2
3‚C6H5CH3
4
O(1)-Zr-O(2)
O(1)-Zr-O(3)
O(1)-Zr-O(4)
O(1)-Zr-O(5)
O(2)-Zr-O(3)
O(2)-Zr-O(4)
O(2)-Zr-O(5)
O(3)-Zr-O(4)
O(3)-Zr-O(5)
O(4)-Zr-O(5)
95.89(6)
112.99(6)
87.20(6)
129.91(6)
99.15(6)
166.18(5)
87.11(5)
91.97(6)
115.82(6)
80.64(5)
O(1)-Zr-O(2)
O(1)-Zr-O(3)
O(1)-Zr-O(4)
O(1)-Zr-O(5)
O(1)-Zr-O(6)
O(2)-Zr-O(3)
O(2)-Zr-O(4)
O(2)-Zr-O(5)
O(2)-Zr-O(6)
O(3)-Zr-O(4)
O(3)-Zr-O(5)
O(3)-Zr-O(6)
O(4)-Zr-O(5)
O(4)-Zr-O(6)
O(5)-Zr-O(6)
80.16(6)
81.88(6)
96.15(8)
87.41(7)
162.86(7)
78.61(7)
94.12(7)
161.55(7)
90.55(7)
172.68(7)
86.23(8)
82.18(7)
100.76(9)
98.88(8)
97.78(8)
O(1)-Zr-O(1)′
O(1)-Zr-O(2)
O(1)-Zr-O(3)
O(1)-Zr-O(4)
O(1)-Zr-O(5)
O(1)′-Zr-O(2)
O(1)′-Zr-O(3)
O(1)′-Zr-O(4)
O(1)′-Zr-O(5)
O(2)-Zr-O(3)
O(2)-Zr-O(4)
O(2)-Zr-O(5)
O(3)-Zr-O(4)
O(3)-Zr-O(5)
O(4)-Zr-O(5)
74.16(18)
91.47(19)
80.49(17)
79.38(17)
167.57(19)
164.79(19)
78.69(17)
80.36(17)
93.44(19)
94.3(2)
102.26(19)
101.0(2)
154.17(18)
98.2(2)
97.9(2)
distances. Although zirconium in 4 is also hexacoordinate,
the sixth coordination site is provided by the µ2-OPh group.
Structures analogous to 4 are also observed in tin chemistry;
an example is [n-BuSn(OH)(O2P(C6H11)2)2]2 (IV).6c
H] (V) which also have three zirconium atoms in the
skeleton.9c,9d However, a part of the skeleton present in 5
may be generated quite readily from V (R ) t-Bu) as shown
in Va. Three arsinates need to replace an oxide and a tert-
butoxy group followed by coordination adjustments to form
5 from Va.
Compound 5 is a trinuclear zirconium cluster with all the
zirconium atoms being hexacoordinate, but the structural
motif is much different from that observed in 2 or 3. The
Zr-O(t-Bu) distance at the central zirconium Zr(2) is the
shortest, followed by the nonbridging Zr-O(t-Bu) bonds to
the Zr(1) and Zr(3). The Zr-O distances involving bridging
arsinate/tert-butoxy are the longest. To our knowledge, this
is the first structurally characterized Zr-O-As bridged
compound. While there are three bridging arsinate ligands
between Zr(1) and Zr(3), two bridging tert-butoxy and an
arsinate ligand connect Zr(1) and Zr(2); only one of the
arsinate oxygens on As(1) coordinates to the two zirconium
atoms. It appears that lesser steric hindrance by the methyl
groups in this arsinate ligand is responsible for this unique
structural feature. It can however be noted that multiple oxy
To summarize, new structural forms for (tert-butoxy)-
zirconium phosphinates/arsinates and phosphates that are
(10) We have isolated another compound with three bridging di(tert-
butoxy)phosphates formulated as Zr2(O-t-Bu)5(HO-t-Bu)(µ,µ′-O2P(O-
t-Bu)2)3 (7), thus showing that such a feature is perhaps common for
arsinates/phosphates. Compound 7 was obtained from a 1:2 stoichio-
metric reaction of 1 to di-tert-butyl phosphate in hexane, but no
warming of the solution was done. Crystals were obtained from hexane
at -10 °C. 1H NMR: 1.41, 1.59, 1.70. 31P NMR (C6D6): -21.56.
13C NMR: 31.15, 31.23, 32.22, 33.59, 73.64, 79.70, 79.85. The spectra
changed over a period of several hours and hence an exact assignment
was not made. Other details including a Platon drawing are available
as Supporting Information.
9
or alkoxy bridging is not uncommon for zirconium.4(b),
Although formation of 5 looks serendipitous, a similar triply
bridged structural motif is also observed in the di-tert-butyl
phosphate species 6. The two bridging tert-butoxy groups
corresponding to O(8) and O(9) in 6 are replaced by the
phosphates corresponding to P(1) and P(2); the type of
additional coordination of As-O oxygen to Zr(1) is absent
in the phosphate structure which leaves Zr(1) pentacoordi-
nate.10
It can be noted that the structures of 5 and 6 are more
open compared to that of Zr3(O)(O-t-Bu)9(OR) [R ) t-Bu,
(9) (a) Teff, D. J.; Huffman, J. C.; Caulton, K. G. Inorg. Chem. 1994, 33,
6289. (b) Teff, D. J.; Huffman, J. C.; Caulton, K. G. J. Am. Chem.
Soc. 1996, 118, 4030. (c) Evans, W. J.; Ansari, M. A.; Ziller, J. W.
Polyhedron 1998, 17, 869. (d) Starikova, Z. A.; Turevskya, E. P.;
Kozlova, N. I.; Turova, N. Ya, Berdyev, D. V.; Yanovsky, A. I.
Polyhedron 1999, 18, 941. (e) Fleeting, K. A.; O′Brien, P.; Jones, A.
C.; Otway, D. J.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton
Trans. 1999, 2853.
5840 Inorganic Chemistry, Vol. 42, No. 19, 2003

Zirconium Phosphinates, Arsinates, and Phosphates
Table 2. Selected Bond Distances and Angles with Esd’s for
Compounds 5 and 6
dynamic in solution are prepared in this study. Even in the
1:1 stoichiometric reactions, the structure of the final products
formed would depend on the steric bulk as well as presence/
absence of a coordinating solvent like THF (compounds 2
and 3). It also appears that substitution of one alkoxy group
by an arsinate/phosphate would make that particular zirco-
nium center more prone for further attack (cf. compounds 5
and 6). Reaction of Zr(O-t-Bu)4 with diphenyl phosphate
involves a unique ligand exchange between P-OPh and Zr-
O-t-Bu groups (e.g., compound 4). It would be interesting
to see whether these multinuclear zirconium compounds (e.g.,
6) could be useful in the MOCVD process.
5
6‚1/2C6H5CH3
Zr(1)-O(1)
Zr(1)-O(2)
Zr(1)-O(3)
Zr(1)-O(8)
Zr(1)-O(9)
Zr(1)-O(10)
Zr(2)-O(4)
Zr(2)-O(8)
Zr(2)-O(9)
Zr(2)-O(10)
Zr(2)-O(12)
Zr(2)-O(14)
Zr(3)-O(5)
Zr(3)-O(6)
Zr(3)-O(7)
Zr(3)-O(11)
Zr(3)-O(13))
Zr(3)-O(15)
1.967(4)
1.945(4)
1.937(4)
2.326(4)
2.303(4)
2.328(4)
1.918(4)
2.154(4)
2.131(4)
2.278(3)
2.071(4)
2.067(4)
1.958(4)
1.996(5)
1.949(4)
2.187(4)
2.227(4)
2.228(4)
Zr(1)-O(1)
1.922(5)
1.920(4)
1.947(4)
2.146(4)
2.191(4)
1.918(4)
2.133(3)
2.141(3)
2.107(3)
2.103(3)
2.150(4)
1.953(4)
1.954(4)
1.959(5)
2.240(4)
2.237(4)
2.239(4)
Zr(1)-O(2)
Zr(1)-O(3)
Zr(1)-O(8)
Zr(1)-O(12)
Zr(2)-O(4)
Zr(2)-O(9)
Zr(2)-O(13)
Zr(2)-O(16)
Zr(2)-O(20)
Zr(2)-O(24)
Zr(3)-O(5)
Zr(3)-O(6)
Zr(3)-O(7)
Zr(3)-O(17)
Zr(3)-O(21)
Zr(3)-O(25)
Experimental Section
All operations were carried out under a dry nitrogen atmosphere
using standard vacuum line techniques. Solvents were purified
according to standard procedures and preserved over sodium wire.11
Diphenyl phosphate, diphenyl phosphinic acid, and cacodylic acid
were procured from Aldrich. Dicyclohexylphosphinic acid and di-
tert-butyl phosphate were prepared according to literature proce-
dures.12 1H, 13C and 31P NMR spectra were recorded on Bruker
200 MHz spectrometers with chemical shifts referenced to TMS
(1H, 13C) or 85% H3PO4 (31P). Elemental analyses were obtained
using a LECO CHN 900 or a Perkin-Elmer 240C CHN analyzer.
Syntheses. Compound 2. To Zr(O-t-Bu)4 (1)4(b), 7 (0.304 g, 0.792
mmol) in toluene (8 mL) was added predried (0.1 mm/70 °C/3 h)
dicyclohexylphosphinic acid (0.182 g, 0.792 mmol) slowly over a
period of 5 min using a glass transfer tube with continuous stirring;
the residual solid adhering to the transfer tube after dissolving in
toluene (7 mL) was also transferred to the reaction flask. The
contents were heated with continuous stirring at 70 °C for 24 h.
After cooling, the solvent was completely removed in a vacuum
and the solid obtained was dissolved in diethyl ether (ca. 4 mL).
Cooling the solution to 0 °C afforded 2 as a crystalline solid after
5
6‚1/2C6H5CH3
O(1)-Zr(1)-O(2)
O(1)-Zr(1)-O(3)
O(1)-Zr(1)-O(8)
O(1)-Zr(1)-O(9)
O(1)-Zr(1)-O(10)
O(2)-Zr(1)-O(3)
O(2)-Zr(1)-O(8)
O(2)-Zr(1)-O(9)
O(2)-Zr(1)-O(10)
O(3)-Zr(1)-O(8)
O(3)-Zr(1)-O(9)
O(3)-Zr(1)-O(10)
O(8)-Zr(1)-O(9)
O(8)-Zr(1)-O(10)
O(9)-Zr(1)-O(10)
O(4)-Zr(2)-O(8)
O(4)-Zr(2)-O(9)
O(4)-Zr(2)-O(10)
O(4)-Zr(2)-O(12)
O(4)-Zr(2)-O(14)
O(8)-Zr(2)-O(9)
O(8)-Zr(2)-O(10)
O(8)-Zr(2)-O(12)
O(8)-Zr(2)-O(14)
O(9)-Zr(2)-O(10)
O(9)-Zr(2)-O(12)
O(9)-Zr(2)-O(14)
O(10)-Zr(2)-O(12)
O(10)-Zr(2)-O(14)
O(12)-Zr(2)-O(14)
O(5)-Zr(3)-O(6)
O(5)-Zr(3)-O(7)
O(5)-Zr(3)-O(11)
O(5)-Zr(3)-O(13)
O(5)-Zr(3)-O(15)
O(6)-Zr(3)-O(7)
O(6)-Zr(3)-O(11)
O(6)-Zr(3)-O(13)
O(6)-Zr(3)-O(15)
O(7)-Zr(3)-O(11)
O(7)-Zr(3)-O(13)
O(7)-Zr(3)-O(15)
O(11)-Zr(3)-O(13)
O(11)-Zr(3)-O(15)
O(13)-Zr(3)-O(15)
95.89(6)
95.89(6)
95.89(6)
95.89(6)
95.89(6)
O(1)-Zr(1)-O(2)
O(1)-Zr(1)-O(3)
O(1)-Zr(1)-O(8)
O(1)-Zr(1)-O(12)
O(2)-Zr(1)-O(3)
95.89(6)
95.89(6)
95.89(6)
95.89(6)
95.89(6)
101.32(19) O(2)-Zr(1)-O(8)
95.25(16) O(2)-Zr(1)-O(12)
96.59(15) O(3)-Zr(1)-O(8)
160.73(15) O(3)-Zr(1)-O(12)
157.83(16) O(8)-Zr(1)-O(12)
93.69(18) O(4)-Zr(2)-O(9)
92.50(16) O(4)-Zr(2)-O(13)
69.67(14) O(4)-Zr(2)-O(16).
68.26(13) O(4)-Zr(2)-O(20)
68.91(13) O(4)-Zr(2)-O(24)
102.28(18) O(9)-Zr(2)-O(13)
101.65(19) O(9)-Zr(2)-O(16)
172.79(15) O(9)-Zr(2)-O(20)
95.93(19) O(9)-Zr(2)-O(24)
146.5(2)
87.52(17)
88.11(17)
160.7(2)
80.07(14)
90.94(16)
93.80(15)
93.08(15)
94.98(16)
178.06(15)
87.67(13)
90.69(13)
173.71(15)
87.20(14)
1
6 d. Yield: 0.256 g (60%). Mp: 265-270 °C. H NMR (C6D6):
δ 1.49 (s, 54 H, t-BuH), 1.00-2.20 (br m, 44 H, cyclohexyl-H).
13C NMR (C6D6): δ 25.41, 25.47, 26.41, 26.50, 26.79, 33.26, 34.34,
36.28, 74.71 (br). 31P NMR (C6D6): δ 42.64. The spectra changed
over a period of 1 d, and in the 31P NMR, an additional peak at
53.30 ppm was noticed. Anal. Calcd for C48H98O10P2Zr2: C, 53.41;
H, 9.08. Found: C, 52.82; H, 9.92.
96.4(2)
O(13)-Zr(2)-O(16) 172.95(14)
76.22(15) O(13)-Zr(2)-O(20)
72.14(14) O(13)-Zr(2)-O(24)
160.99(16) O(16)-Zr(2)-O(20)
94.23(16) O(16)-Zr(2)-O(24)
72.83(14) O(20)-Zr(2)-O(24)
94.94(16) O(5)-Zr(3)-O(6)
161.02(15) O(5)-Zr(3)-O(7)
89.25(15) O(5)-Zr(3)-O(17)
88.71(14) O(5)-Zr(3)-O(21)
89.06(16) O(5)-Zr(3)-O(25)
98.99(19) O(6)-Zr(3)-O(7)
101.17(19) O(6)-Zr(3)-O(17)
91.41(17) O(6)-Zr(3)-O(21)
165.53(17) O(6)-Zr(3)-O(25)
87.23(18) O(7)-Zr(3)-O(17)
89.83(13)
86.70(13)
91.10(14)
86.38(13)
86.90(14)
99.0(2)
96.6(2)
Compound 3‚C6H5CH3. The reaction was performed by a
procedure analogous to that for 2 using 1 (0.926 g, 2.41 mmol) in
THF (10 mL) and predried (0.1 mm/70 °C/3 h) diphenyl phosphinic
acid (0.53 g, 2.41 mmol). After cooling, the volatiles were
completely removed in a vacuum and the residue was redissolved
in a mixture of toluene and THF (10:1). Insolubles (ca. 0.3 g) were
removed by filtration. The residue upon keeping at 0 °C for 3 d
gave 3‚2THF‚2C6H5CH3 as thick needles. Yield: 0.72 g (40%).
Mp: sweats at around 80 °C and completely melts at ∼200 °C. 1H
NMR (C6D6): δ 1.11-1.13 (m, 8 H, CCH2), 1.54 (s, 54 H, t-BuH),
2.11 (s, ca. 6H, Ar-CH3), 3.81 (m, 8 H, OCH2), 6.95-7.20 (m,
ca. 22H, Ar-H), 8.38-8.47 (m, 8H, Ar-H). Since the crystals lost
toluene quickly, this part of the integration could not be obtained
accurately; the crystals had to be mounted along with some mother
liquor for X-ray data collection. 13C NMR (C6D6): δ 21.13, 24.67,
33.36, 70.19 (THF), 73.88, 125.39, 126.95, 127.27, 127.76, 129.04,
169.12(17)
90.2(2)
91.13(19)
97.3(2)
88.95(17)
167.33(17)
90.07(18)
89.69(18)
90.2(2)
168.4(2)
80.86(16)
81.40(15)
81.02(17)
97.6(2)
O(7)-Zr(3)-O(21)
88.46(16) O(7)-Zr(3)-O(25)
89.82(17) O(17)-Zr(3)-O(21)
169.57(16) O(17)-Zr(3)-O(25)
164.96(18) O(21)-Zr(3)-O(25)
88.93(17)
89.35(19)
77.27(15)
83.00(15)
82.49(15)
130.54, 132.43, 132.64, 135.93, 138.81. 31P NMR (C6D6): δ 13.33.
The spectra changed over a period of several days and in the 31P
NMR, a broad featureless peak in the region 15-28 ppm was
noticed. Anal. Calcd for C63H98O12P2Zr2: C, 58.52; H, 7.58.
Found: C, 59.12; H, 7.27.
(11) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, England, 1986.
(12) (a) Peppard, D. F.; Mason, G. W.; Andrejasich, C. M. J. Inorg. Nucl.
Chem. 1965, 27, 697. (b) Zwierzak, A.; Kluba, M. Tetrahedron 1971,
27, 3163.
Inorganic Chemistry, Vol. 42, No. 19, 2003 5841

Kumara Swamy et al.
Table 3. Crystal Data for Compounds 2, 3, 5, and 6
compound
emp formula
fw
cryst syst
space group
A (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
2
3‚C6H5CH3
C63H98O12P2Zr2
1291.79
triclinic
P1h
12.326(2)
12.423(2)
13.696(3)
67.00(3)
71.89(3)
67.50(3)
1751.2(6)
1
5
6‚1/2C6H5CH3
C48H98O10P2Zr2
1079.64
monoclinic
P21/c
10.273(2)
11.148(2)
25.830(5)
90
98.10(3)
90
2928.6(10)
2
C42H99As3O15Zr3
1342.63
monoclinic
P21/n
20.329(4)
12.025(2)
27.685(6)
90
109.50(3)
90
6380(2)
4
C71.50H157O27P5Zr3
1877.48
monoclinic
P21/n
19.096(4)
20.631(4))
26.855(5)
90
92.43(3)
90
10571(4)
4
Z
D
calcd (g cm-3
)
1.224
0.457
1152
1.225
0.396
682
1.398
2.076
2760
1.180
0.426
3988
µ (mm-1
F(000)
)
no of data/restraints/param
S
4294/0/280
1.062
0.0232
0.0610
0.334/-0.239
5024/13/388
1.045
0.0301
0.0846
0.762/-0.335
9897/0/577
1.008
0.0510
0.1394
0.974/--1.315
15851/14/953
1.007
0.0547
0.1624
0.850/-0.713
R1 [I > 2σ(I)]a
wR2 [all data]a
max/min residual electron dens (e Å-3
)
2
2
4
a R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) [Σw(Fo - Fc )2/∑wFo ]0.5
.
Compound 4. The procedure was analogous to that for 2 using
1 (0.611 g, 1.59 mmol) in toluene (10 mL) and predried diphenyl
phosphate (0.400 g, 1.59 mmol). After cooling, the volatiles were
completely removed in a vacuum and the residue was dissolved in
hexane (6 mL). Upon preservation at -10 °C, a microcrystalline
solid was obtained (ca. 0.35 g). This upon redissolving in a mixture
of hexane and diethyl ether (10:1, ca. 5 mL) and preserving at -10
°C afforded 5 as hexagonal shaped crystals (0.15 g) after 7 d. [There
were also a few rhombus-shaped crystals that could not be analyzed
satisfactorily (by spectroscopy) because of the smaller amount.]
We were not able to get more of 4 by further concentrating the
mother liquor after removal of the microcrystalline solid. Yield:
vacuo at 40 °C. The crystalline material was redissolved in toluene
(3 mL) with slight warming; a small amount of insoluble material
(ca. 0.05 g) was again filtered off. Crystals of 6‚1/2C6H5CH3
appeared after 12 h. Mp: >270 °C (loss of crystallinity at 210
1
°C). H NMR: 1.53, 1.54, 1.57, 1.66, 1.69, 1.77; the spectrum of
the crystal without drying showed a peak at 2.1 ppm due to toluene.
31P NMR (C6D6): -23.12, -23.06, -21.20 (∼2:2:1 ratio). 13C
NMR: 31.38 (br), 33.35, 34.10, 73.50, 75.85. The spectra changed
over a period of several hours, and hence, an exact assignment was
difficult. Anal. Calcd for C68H153O27P5Zr3 (after drying in vacuo
for 2 h): C, 44.60; H, 8.42. Found: C, 45.15; H, 8.54.
1
All the above compounds (2-6) were unstable toward moisture;
however, 2 could be handled for a few minutes in air.
0.15 g (17%). Mp: >280 °C. H NMR (C6D6): δ 0.95 (s, 18H,
PO-t-BuH), 1.00-1.60 (br, ca. 36 H, ZrO-t-BuH), 6.80-7.50 (br,
ca. 10H, ArH. 13C NMR (C6D6): δ 29.98, 31.23, 127.00, 128.28
(other signals were of low intensity and buried in the noise). 31P
NMR (C6D6): δ -14.08. Anal. Calcd for C48H74O14P2Zr2: C, 51.50;
H, 6.62. Found: C, 51.15; H, 6.52.
X-ray Crystallography. Single crystals were selected from the
bulk samples of compounds 2 and 4-6 and sealed in Lindemann
capillaries under an atmosphere of nitrogen. For 3‚C6H5CH3, a small
amount of the solution of crystallization was also inserted inside
the capillary before sealing. Data were collected using a Stoe IPDS
diffractometer. Numerical absorption corrections were applied. The
structures were solved by direct methods and refined by standard
procedures.13 The quality of the crystals (and hence the X-ray data)
of 4 was not good despite repeated attempts and hence high
residuals of 2.4 e Å-3 were observed close to zirconium; however,
there was no ambiguity regarding the connectivity of the atoms.
We have also tried to make a correction using Difabs, but the two
ghost-peaks did not disappear.14 In the case of 5 one of the methyl
carbons of a tert-butoxy group [C(36)] is disordered. In 6‚1/2C6H5-
CH3, the solvent toluene was heavily disordered, and hence, these
carbon atoms were refined isotropically; the rest of the non-
hydrogen atoms were refined anisotropically. Crystal data for 2, 3,
5, and 6 are provided in Table 3.
Compound 5. The procedure was analogous to that for 2 using
1 (0.658 g, 1.70 mmol) in toluene (10 mL) and predried (0.1 mm/
70 °C/3 h) cacodylic acid (0.237 g, 1.70 mmol) [CAUTION!
Cacodylic acid (dimethylarsinic acid) and its derivatives have to
be handled with care inside an efficient hood and with sufficient
protection]. After cooling, the volatiles were completely removed
in a vacuum and the residue was dissolved in hexane (5 mL).
Insolubles (ca. 0.05 g) were removed by filtration and the clear
solution upon preserving at -10 °C gave 5 as irregular shaped
crystals; more crystals were obtained after removing the first batch.
1
Yield: 0.80 g (69%). Mp: >250 °C. H NMR (C6D6): δ 1.33,
1.40, 1.45, 1.47, 1.60, 1.62, 1.64, 1.67 (s each, together 93 H,
AsCH3 + t-BuH), 2.19 (s, 6 H, AsCH3). 13C NMR (C6D6): δ 19.46,
19.59, 21.71, 30.20, 32.15, 33.24, 33.55, 33.65, 33.73, 33.79, 33.93,
72.57, 73.01, 74.89, 75.61, 76.57, 76.89. The spectra changed over
a period of several days, and after 10 days, the tert-butyl protons
appeared as a broad peak and the As-CH3 protons appeared
essentially as a single peak at 1.14 ppm. Anal. Calcd for C42H99O15-
As3P3Zr3: C, 37.57; H, 7.38. Found: C, 37.16; H, 7.37.
Compound 6‚1/2C6H5CH3. A solution of (t-BuO)2POOH (0.476
g, 2.27 mmol; dried in a vacuum for 6 h at 0.1 mmHg) in hexane
(10 mL) was added dropwise (ca. 10 min) to a solution of 1 (0.869
g, 2.27 mmol) and the contents stirred overnight. Insoluble material
(ca. 0.2 g) was filtered off and the solvent completely removed in
(13) Sheldrick, G. M. SHELX-97: Programs for Crystal Structure Solution
and Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(14) Relevant crystal data for 4: Emperical formula C48H74O14P2Zr2,
formula weight 1119.45, monoclinic, C2/c, a ) 21.387(4) Å, b )
20.372(4) Å, c ) 13.294(3) Å, â ) 95.98(3)°, V ) 5761(2) Å3, Z )
4, Dcalcd ) 1.291 g cm-3, µ ) 0.473 mm-1, F(000) ) 2336, no. of
data/restraints/parameters ) 4468/0/307. S ) 1.021, R1 [I > 2σ(I)]
) 0.0920, wR2 [all data] ) 0.2050, maximum/minimum residual
electron density ) 2.435/-01.339 e Å-3. Further data are available
from the authors.
5842 Inorganic Chemistry, Vol. 42, No. 19, 2003

Zirconium Phosphinates, Arsinates, and Phosphates
Platon drawing of 7 with cell and bond parameters, and text giving
crystal data for 7. This material is available free of charge via the
Internet at http://pubs.acs.org.
Acknowledgment. K.C.K.S. thanks the Alexander von
Humboldt Foundation for financial support under the revisit
program as well as for equipment.
Supporting Information Available: X-ray structure determi-
nation and crystal data for 2, 3, 5, and 6 as CIF files, Figure 5, a
IC034458O
Inorganic Chemistry, Vol. 42, No. 19, 2003 5843