Heterodimetallic germanium(IV) complex structures with transition metals

Article abstract of DOI:10.1021/ic700507j

The hydrothermal synthesis and structural characterization of a number of complex compounds containing the divalent tris(oxalato-O,O′)germanate anion, [Ge(C₂O₄)₃]^2-, or the neutral bis(oxalate-O,O′)germanium fragment, [Ge(C₂O₄) ₂], with transition-metal (M) cationic complexes of 1,10′-phenanthroline (phen) is reported: [M(phen)₃]-[Ge(C ₂O₄)₃]·-xH₂O [where M ²⁺ = Cu²⁺ (1a and 1b), Fe²⁺ (2a and 2b), Ni²⁺ (3), Co²⁺ (4); x = 0.2 for 2b], [MGe(phen) ₂(μ₂-OH)₂(C₂O₄) ₂] [where M²⁺ = Cd²⁺ (5) and Cu²⁺ (6)]. The isolation of two polymorphs with Cu²⁺ (1a and 1b) and other pseudo-polymorphs for Fe²⁺ (2a and 2b) was rationalized based on slightly different molar ratios for the starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basis of single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series of compounds was discussed on the basis of the various intermolecular interactions present (strong C-H...π and weak C-H...O hydrogen-bonding interactions, C-H...π and π-π contacts).

Full text of DOI:10.1021/ic700507j

Inorg. Chem. 2007, 46, 6502−6515
Heterodimetallic Germanium(IV) Complex Structures with Transition
Metals
Fa-Nian Shi,† Lu´ıs Cunha-Silva,† Michaele J. Hardie,‡ Tito Trindade,† Filipe A. Almeida Paz,† and
Joa˜o Rocha*,†
Department of Chemistry, UniVersity of AVeiro, CICECO, 3810-193 AVeiro, Portugal and School
of Chemistry, UniVersity of Leeds, Leeds LS2 9JT, United Kingdom
Received March 15, 2007
The hydrothermal synthesis and structural characterization of a number of complex compounds containing the
divalent tris(oxalato-O,O )germanium fragment,
)germanate anion, [Ge(C2O4)3]2-, or the neutral bis(oxalate-O,O
[Ge(C2O4)2], with transition-metal (M) cationic complexes of 1,10 -phenanthroline (phen) is reported: [M(phen)3]-
′
′
′
+
+
+
+
+
[Ge(C2O4)3]
‚
xH2O [where M2
)
Cu2 (1a and 1b), Fe2 (2a and 2b), Ni2 (3), Co2 (4); x
)
0.2 for 2b], [MGe-
+
+
+
+
(phen)2(
µ
2-OH)2(C2O4)2] [where M2
)
Cd2 (5) and Cu2 (6)]. The isolation of two polymorphs with Cu2 (1a and
1b) and other pseudo-polymorphs for Fe2 (2a and 2b) was rationalized based on slightly different molar ratios for
the starting materials. All compounds have been characterized using EDS, SEM, vibrational spectroscopy (FT-IR
and FT-Raman), thermogravimetry, and CHN elemental composition and their structure determined on the basis
of single-crystal X-ray diffraction studies. The crystal packing of the different chemical moieties for each series of
+
compounds was discussed on the basis of the various intermolecular interactions present (strong C
−H‚‚‚π and
weak C ‚‚‚O hydrogen-bonding interactions, C ‚‚‚π and π−π contacts).
−H
−H
Introduction
these materials find interesting potential applications arising
from their peculiar architectures such as zeolite-like frame-
works13 and the inherent properties of the metallic centers,
for example, photoluminescence arising from the presence
of lanthanides.14
In recent years, research on crystalline organic-inorganic
hybrid oxalates has gained great interest in materials science
due to the structural diversity of these compounds which
range from discrete complexes1-4 to 1D chains,5-7 2D
layers,8,9 and 3D open frameworks.10-12 Moreover, some of
Following our ongoing research on crystalline the hybrid
materials,15-25 we recently focused our attention on the use
* To whom correspondence should be addressed. Phone: (+351) 234
370730. Fax: (+351) 234 370084. E-mail: rocha@dq.ua.pt.
† University of Aveiro.
(11) Mohanu, A.; Brouca-Cabarrecq, C.; Trombe, J. C. J. Solid State Chem.
2006, 179, 3-17.
‡ University of Leeds.
(12) Chapelet-Arab, B.; Nowogrocki, G.; Abraham, F.; Grandjean, S. J.
Solid State Chem. 2005, 178, 3055-3065.
(1) Cangussu, D.; Stumpf, H. O.; Adams, H.; Thomas, J. A.; Lloret, F.;
Julve, M. Inorg. Chim. Acta 2005, 358, 2292-2302.
(2) Armentano, D.; De Munno, G.; Lloret, F.; Julve, M. CrystEngComm
2005, 7, 57-66.
(3) Carranza, J.; Grove, H.; Sletten, J.; Lloret, F.; Julve, M.; Kruger, P.
E.; Eller, C.; Rillema, D. P. Eur. J. Inorg. Chem. 2004, 4836-4848.
(4) Vaidhyanathan, R.; Natarajan, S.; Rao, C. N. R. Dalton Trans. 2001,
699-706.
(5) Zhang, Q. Z.; Yang, W. B.; Lu, C. Z. J. Chem. Crystallogr. 2006, 36,
225-228.
(6) Yang, S. H.; Li, G. B.; Tian, S. J.; Liao, F. H.; Lin, J. H. Eur. J.
Inorg. Chem. 2006, 2850-2854.
(7) Garcia-Couceiro, U.; Castillo, O.; Luque, A.; Garcia-Teran, J. P.;
Beobide, G.; Roman, P. Eur. J. Inorg. Chem. 2005, 4280-4290.
(8) Zhang, L.; Ge, Y. Y.; Peng, F.; Du, M. Inorg. Chem. Commun. 2006,
9, 486-488.
(13) Mahe, N.; Audebrand, N. Solid State Sci. 2006, 8, 988-999.
(14) Song, J. L.; Mao, J. G. Chem. Eur. J. 2005, 11, 1417-1424.
(15) Soares-Santos, P. C. R.; Paz, F. A. A.; Ferreira, R. A. S.; Klinowski,
J.; Carlos, L. D.; Trindade, T.; Nogueira, H. I. S. Polyhedron 2006,
25, 2471-2482.
(16) Shi, F. N.; Paz, F. A. A.; Girginova, P.; Rocha, J.; Amaral, V. S.;
Klinowski, J.; Trindade, T. J. Mol. Struct. 2006, 789, 200-208.
(17) Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T.; Shi, F. N.; Mafra,
L. Prog. Solid State Chem. 2005, 33, 113-125.
(18) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Nogueira, H. I. S.; Rocha,
J.; Amaral, V. S.; Klinowski, J.; Trindade, T. J. Solid State Chem.
2006, 179, 1497-1505.
(19) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Amaral, V. S.; Rocha, J.;
Klinowski, J.; Trindade, T. Inorg. Chim. Acta 2006, 359, 1147-1158.
(20) Mafra, L.; Paz, F. A. A.; Shi, F. N.; Fernandez, C.; Trindade, T.;
Klinowski, J.; Rocha, J. Inorg. Chem. Commun. 2006, 9, 34-38.
(21) Shi, F. N.; Paz, F. A. A.; Girginova, P. I.; Mafra, L.; Amaral, V. S.;
Rocha, J.; Makal, A.; Wozniak, K.; Klinowski, J.; Trindade, T. J. Mol.
Struct. 2005, 754, 51-60.
(9) Manna, S. C.; Zangrando, E.; Drew, M. G. B.; Ribas, J.; Chaudhuri,
N. R. Eur. J. Inorg. Chem. 2006, 481-490.
(10) Tsao, C. P.; Sheu, C. Y.; Nguyen, N.; Lii, K. H. Inorg. Chem. 2006,
45, 6361-6364.
6502 Inorganic Chemistry, Vol. 46, No. 16, 2007
10.1021/ic700507j CCC: $37.00
© 2007 American Chemical Society
Published on Web 07/10/2007

Heterodimetallic Germanium(IV) Complex Structures
Scheme 1
Scheme 2
of germanium centers.26,27 These often exhibit two distinct
oxidation states, +2 and +4, with the latter being the most
stable at ambient conditions and commonly appearing in
inorganic compounds (such as GeO2) and germanate frame-
works.28,29 In addition, Ge4+ centers exhibit a number of
distinct coordination numbers and environments, namely,
four (often tetrahedral),30-32 five (square pyramidal or
trigonal bipyramidal),31,33-36 and six (often octahedral),37,38
a crucial feature in order to achieve topological diversity for
the frameworks.
which is instead connected by two µ2-bridging hydroxyl
groups to a cationic [M(phen)2]2+ fragment, [MGe(phen)2-
(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)]
(Scheme 2). For the former series of compounds, two
polymorphs for Cu2+, and a pseudo-polymorph for Fe2+
could be isolated by employing slightly different synthetic
procedures. Remarkably, searches in the literature and the
Cambridge Structure Database (CSD, Version 5.28 Nov
2006)39,40 reveal that only a handful of structures containing
Here we wish to report the first complex-based heterodi-
metallic crystalline compounds containing the divalent tris-
(oxalato-O,O′)germanate anion crystallizing with a number
of transition-metal (M) complexes with 1,10′-phenanthroline
(phen) organic residues, [M(phen)3][Ge(C2O4)3]‚xH2O [where
[Ge(C2O4)3-x]
2(x-1) moieties are known to date, all comprising
small organic molecules or K+ as the counterions.41-44
Experimental Section
M
2+ ) Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), Co2+
General. Chemicals were readily available from commercial
sources and used as received without further purification: amor-
phous germanium(IV) oxide (GeO2, 99.99+%, Aldrich), oxalic acid
dihydrate (H2C2O4‚2H2O, g99%, Panreac), 1,10′-phenanthroline
monohydrate (phen, C12H8N2‚H2O, g99.0%, Fluka), copper(II)
acetate monohydrate (CuC4H6O4‚H2O, 98%, Panreac), nickel(II)
acetate tetrahydrate (NiC4H6O4‚4H2O, g99%, Riedel-deHae¨n),
cobalt(II) acetate tetrahydrate (CoC4H6O4‚4H2O, 98%, Panreac),
cadmium(II) acetate dihydrate (CdC4H6O4‚2H2O, 98%, Fluka),
ammonium ferrous sulfate hexahydrate [(NH4)2Fe(SO4)2‚6H2O,
99%, Merck], and potassium ferric oxalate [KFe(C2O4)2, 99%,
Ventron].
Instrumentation. Elemental analyses for C, H, and N were
performed in a CHNS-932 elemental analyzer in the Microanalysis
Laboratory of the University of Aveiro.
Thermogravimetric analyses (TGA) were carried out using a
Shimadzu TGA 50 with a heating rate of 5 °C/min under a
continuous flow of air with rate of 20 cm3/min.
(4); x ) 0.2 for 2b (Scheme 1). Furthermore, the first
examples of binuclear complexes containing the neutral bis-
(oxalate-O,O′)germanium fragment [Ge(C2O4)2] are reported,
(22) Shi, F. N.; Paz, F. A. A.; Rocha, J.; Klinowski, J.; Trindade, T. Inorg.
Chim. Acta 2005, 358, 927-932.
(23) Girginova, P. I.; Paz, F. A. A.; Nogueira, H. I. S.; Silva, N. J. O.;
Amaral, V. S.; Klinowski, J.; Trindade, T. Polyhedron 2005, 24, 563-
569.
(24) Paz, F. A. A.; Klinowski, J. J. Solid State Chem. 2004, 177, 3423-
3432.
(25) Paz, F. A. A.; Shi, F. N.; Klinowski, J.; Rocha, J.; Trindade, T. Eur.
J. Inorg. Chem. 2004, 2759-2768.
(26) Mafra, L.; Paz, F. A. A.; Shi, F. N.; Rocha, J.; Trindade, T.; Fernandez,
C.; Makal, A.; Wozniak, K.; Klinowski, J. Chem. Eur. J. 2005, 12,
363-375.
(27) Mafra, L.; Almeida Paz, F. A.; Shi, F. N.; Sa´ Ferreira, R. A.; Carlos,
L. D.; Trindade, T.; Fernandez, C.; Klinowski, J.; Rocha, J. Eur. J.
Inorg. Chem. 2006, 47-41-4751.
(28) Greenwood, N. N.; Earnshaw, A. Chem. Elements, 2nd ed.; Butter-
worth-Heinemann: Oxford, U.K., 1997.
Scanning electron microscopy (SEM) and energy dispersive
analysis of X-rays spectroscopy (EDS) were performed using a
Hitachi S-4100 field emission gun tungsten filament instrument
working at 25 kV. Samples were prepared by deposition on
aluminum sample holders and were carbon coated.
(29) Cotton, F. A.; Wilkinson, G. AdVanced Inorganic Chemistry, 5th ed.;
John Wiley & Sons: New York, 1988.
(30) Karlov, S. S.; Lermontova, E. K.; Zabalov, M. V.; Selina, A. A.;
Churakov, A. V.; Howard, J. A. K.; Antipin, M. Y.; Zaitseva, G. S.
Inorg. Chem. 2005, 44, 4879-4886.
(31) Schnepf, A. Eur. J. Inorg. Chem. 2005, 2120-2123.
(32) Iwamoto, T.; Masuda, H.; Ishida, S.; Kabuto, C.; Kira, M. J. Am. Chem.
Soc. 2003, 125, 9300-9301.
FT-IR spectra were collected from KBr pellets (Aldrich, 99%+,
FT-IR grade) on a Mattson 7000 FT-IR spectrometer. Fourier
(33) Chen, L.; Chen, J. X.; Sun, L. J.; Xie, Q. L. Appl. Organomet. Chem.
2005, 19, 1038-1042.
Transform Raman (FT-Raman) spectra (range 4000-100 cm-1
)
(34) Khrustalev, V. N.; Portnyagin, I. A.; Borisova, I. V.; Zemlyansky, N.
N.; Ustynyuk, Y. A.; Antipin, M. Y.; Nechaev, M. S. Organometallics
2006, 25, 2501-2504.
(39) Allen, F. H. Acta Crystallogr., Sect. B 2002, 58, 380-388.
(40) Allen, F. H.; Motherwell, W. D. S. Acta Crystallogr., Sect. B 2002,
58, 407-422.
(35) Takeuchi, Y.; Tanaka, K.; Tanaka, K.; Ohnishi-Kameyama, M.;
Kalman, A.; Parkanyi, L. Chem. Commun. 1998, 2289-2290.
(36) Holmes, R. R.; Day, R. O.; Sau, A. C.; Poutasse, C. A.; Holmes, J.
M. Inorg. Chem. 1985, 24, 193-199.
(41) Seiler, O.; Burschka, C.; Penka, M.; Tacke, R. Z. Anorg. Allg. Chem.
2002, 628, 2427-2434.
(42) Dean, P. A. W.; Dance, I. G.; Craig, D. C.; Scudder, M. L. Acta
Crystallogr., Sect. C 2001, 57, 1030-1031.
(37) Shen, X.; Nakashima, A.; Sakata, K.; Hashimoto, M. Inorg. Chem.
Commun. 2004, 7, 621-624.
(38) Krivokapic, A.; Anderson, H. L.; Bourhill, G.; Ives, R.; Clark, S.;
McEwan, K. J. AdV. Mater. 2001, 13, 652-656.
(43) Martin, L.; Turner, S. S.; Day, P.; Guionneau, P.; Howard, J. A. K.;
Uruichi, M.; Yakushi, K. J. Mater. Chem. 1999, 9, 2731-2736.
(44) Jorgensen, N.; Weakley, T. J. R. Dalton Trans. 1980, 2051-2052.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6503

Shi et al.
were recorded on a Bruker RFS 100 spectrometer with a Nd:YAG
coherent laser (λ ) 1064 nm).
Selected FT-IR and Raman (inside parentheses and in italics) data
(in cm-1): ν(C-H, aromatic) ) 3076w, (3076); ν(uncoordinated
carbonyl groups) ) 1734s, (1763); νasym(-CO2-) ) 1671m, 1631w,
1577w, (1632, 1602, 1580); ν(C-C, skeletal vibrations) ) 1512w,
1494w, (1513, 1454); δ(C-H) ) 1425s, (1431); νsym(-CO2-) )
1425s, 1363w, 1328s, (1431, 1345, 1304); ν(C-N, heteroaromatic
amines) ) 1328s, (1304); ν(C-O) ) 1227s, 1197m, 1140w, (1208,
1142, 1105); ν(C-C skeletal stretching mode) ) 1096w, 1054w,
(1055); ν(C-H) ) 987w, (911); ν(C-C and Ge-O) ) 892m, 842s,
819s, (877); δ(CO2-) ) 771w, 721s, (739); γ(C-H) ) 645w, 595w,
532w, (646); ν(M-N) and F(CO2-) ) 470m, (439).
Synthesis of [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b). The syn-
thetic procedure used to isolate this hydrated polymorph of [Fe-
(phen)3][Ge(C2O4)3] is identical to that described for 1a but using
instead (NH4)2Fe(SO4)2‚6H2O as the Fe2+ source. The reaction
mixture contained 0.050 g of GeO2, 0.180 g of H2C2O4‚2H2O,
0.130 g of (NH4)2Fe(SO4)2‚6H2O, 0.200 g of phen, and 15 g of
H2O (approximate molar composition of 1GeO2:3H2C2O4:2/3(NH4)2-
Fe(SO4)2‚6H2O:2phen). Yield 53.5% based on (NH4)2Fe(SO4)2‚
6H2O.
Calculated elemental composition (based on single-crystal data
for C42H24.40N6O12.20FeGe, MW 936.72; %): C 53.85, N 8.97, H
2.63. Found (%): C 53.12, N 8.68, H 2.64. TGA data (weight losses
inside parentheses): 30-268 °C (-0.8%); 268-342 °C (-59.8%);
342-599 °C (-18.8%). Selected FT-IR and Raman (inside
parentheses and in italics) data (in cm-1): ν(C-H, aromatic) )
3071m, (3071); ν(uncoordinated carbonyl groups) ) 1740s, (1765,
1727); νasym(-CO2-) ) 1672s, 1614s, (1630, 1600, 1580);
ν(C-C, skeletal vibrations) ) 1517m, 1494w, (1513, 1453);
δ(C-H) ) 1424s, (1427); νsym(-CO2-) ) 1424s, 1358m, 1313s,
(1427, 1341, 1299); ν(C-N, heteroaromatic amines) ) 1313s,
(1299); ν(C-O) ) 1218m, 1186w, 1141w, (1206, 1141); ν(C-C
skeletal stretching mode) ) 1105w, (1106, 1056); ν(C-C and Ge-
O) ) 893m, 849m, 817s, (875); δ(CO2-) ) 725s, (741); γ(C-H)
) 646w, 596w, 530w, (647, 596); ν(M-N) and F(CO2-) ) 470m,
420w, (437).
Synthesis of [Ni(phen)3][Ge(C2O4)3] (3). The synthetic proce-
dure used to isolate [Ni(phen)3][Ge(C2O4)3] is identical to that
described for 1a but using instead NiC4H6O4‚4H2O as the Ni2+
source. The reaction mixture contained 0.050 g of GeO2, 0.180 g
of H2C2O4‚2H2O, 0.080 g of NiC4H6O4‚4H2O, 0.200 g of phen,
and 15 g of H2O (approximate molar composition of 1GeO2:
3H2C2O4:2/3NiC4H6O4:2phen). Yield 53.5% based on NiC4H6O4‚
4H2O.
Synthesis of [Cu(phen)3][Ge(C2O4)3] (1a). A mixture containing
0.06 g of GeO2, 0.18 g of H2C2O4‚2H2O, 0.10 g of CuC4H6O4‚
H2O, and 0.20 g of phen was mixed in ca. 15 g of distilled water
and stirred at ambient temperature for 30 min. The resulting
homogeneous suspension, with approximate molar composition of
1:3:1:2, respectively, was transferred to an autoclave (ca. 40 mL)
and heated at 100 °C for 72 h. Large single crystals of [Cu(phen)3]-
[Ge(C2O4)3] were directly obtained from the autoclave contents
along with some small impurities (later identified as compound 6,
see below) which could not be eliminated by physical separation.
The sample was washed with copious amounts of distilled water,
filtrated, and air-dried under ambient conditions (yield 49.0% based
on CuC4H6O4‚H2O).
Calculated elemental composition (based on single-crystal data
for C42H24N6O12CuGe, MW 940.80; %): C 53.62, N 8.93, H 2.57.
Found for the as-synthesized bulk material (%): C 49.49,
N 8.39, H 2.41. TGA data (weight losses inside parentheses):
205-341 °C (-40.7%); 341-599 °C (-35.3%). Selected FT-IR
and Raman (inside parentheses and in italics) data (in cm-1):
ν(C-H, aromatic) ) 3068w, 2933w, (3073); ν(uncoordinated
carbonyl groups) ) 1735s; νasym(-CO2-) ) 1676s, 1627m, 1588w,
(1606, 1545); ν(C-C, skeletal vibrations) ) 1518m, 1497w, (1446);
δ(C-H) ) 1428s, (1411); νsym(-CO2-) ) 1428s, 1362s, 1330s,
(1411); ν(C-N, heteroaromatic amines) ) 1330s; ν(C-O) )
1226m, 1198w, 1146w, (1296); ν(C-C skeletal stretching mode)
) 1105w, (1054); ν(C-H) ) 992w; ν(C-C and Ge-O) ) 893w,
845m, 819s, (807); δ(CO2-) ) 775w, 725s, (721); γ(C-H) )
644w, 595w; ν(M-N) and F(CO2-) ) 470m, 426w, (427).
Synthesis of [Cu(phen)3][Ge(C2O4)3] (1b). The synthetic pro-
cedure used to isolate this polymorph is identical to that described
for 1a but using instead a reaction mixture containing 0.050 g of
GeO2, 0.180 g of H2C2O4‚2H2O, 0.095 g of CuC4H6O4‚H2O,
0.300 g of phen, and 15 g of H2O (approximate molar composition
of 1GeO2:3H2C2O4:1CuC4H6O4:3phen). Yield 95.6% based on
CuC4H6O4‚H2O.
Calculated elemental composition (based on single-crystal data
for C42H24N6O12CuGe, MW 940.80; %): C 53.62, N 8.93, H 2.57.
Found (%): C 53.50, N 8.72, H 2.54. TGA data (weight losses
inside parentheses): 201-343 °C (-48.0%); 343-599 °C (-31.9%).
Selected FT-IR and Raman (inside parentheses and in italics) data
(in cm-1): ν(C-H, aromatic) ) 3059w, (3069); ν(uncoordinated
carbonyl groups) ) 1737s; νasym(-CO2-) ) 1669w, 1621w, 1588w,
(1624, 1605, 1586); ν(C-C, skeletal vibrations) ) 1515m, 1493w,
(1449); δ(C-H) ) 1425m, (1416); νsym(-CO2-) ) 1425m, 1318s,
(1416, 1307); ν(C-N, heteroaromatic amines) ) 1318s, (1307);
ν(C-O) ) 1225m, 1191w, 1139w; ν(C-C skeletal stretching
mode) ) 1102w, (1053); ν(C-H) ) 1000w, 965w; ν(C-C and
Ge-O) ) 892m, 853m, 821s; δ(CO2-) ) 778w, 724m, (735);
γ(C-H) ) 645w, 593w; ν(M-N) and F(CO2-) ) 470m, 420w,
(425).
Synthesis of [Fe(phen)3][Ge(C2O4)3] (2a). The synthetic pro-
cedure used to isolate [Fe(phen)3][Ge(C2O4)3] is identical to that
described for 1a with the reaction mixture containing instead
0.050 g of GeO2, 0.140 g of H2C2O4‚2H2O, 0.110 g of KFe(C2O4)2,
0.200 g of phen, and 15 g of H2O (approximate molar composition
of 1GeO2:2H2C2O4:2/3KFe(C2O4)2:2phen). Yield 58.1% based on
KFe(C2O4)2.
Calculated elemental composition (based on single-crystal data
for C42H24N6O12NiGe, MW 935.97; %): C 53.90, N 8.98, H 2.58.
Found (%): C 52.98, N 9.01, H 2.55. TGA data (weight losses
inside parentheses): 280-374 °C (-44.9%); 374-599 °C (-34.5%).
Selected FT-IR and Raman (inside parentheses and in italics) data
(in cm-1): ν(C-H, aromatic) ) 3073w, (3079); ν(uncoordinated
carbonyl groups) ) 1737s, (1759, 1721); νasym(-CO2-) ) 1676s,
1627m, 1588w, (1627, 1611, 1588); ν(C-C, skeletal vibrations)
) 1518m, 1497w, (1517, 1461); δ(C-H) ) 1428s, (1423);
ν
sym(-CO2-) ) 1428s, 1362s, 1330s, (1423, 1362, 1345, 1322,
1311); ν(C-N, heteroaromatic amines) ) 1330s, (1322, 1311);
ν(C-O) ) 1226m, 1198w, 1146w, (1258, 1206, 1146); ν(C-C
skeletal stretching mode) ) 1105w, (1056); ν(C-H) ) 992w, (905);
ν(C-C and Ge-O) ) 893w, 845m, 819s, (872); δ(CO2-) ) 775w,
725s, (733); γ(C-H) ) 644w, 595w, (597, 560); ν(M-N) and
F(CO2-) ) 470m, 426w, (514, 485, 426).
Synthesis of [Co(phen)3][Ge(C2O4)3] (4). The synthetic proce-
dure used to isolate [Co(phen)3][Ge(C2O4)3] as a microcrystalline
light-yellow powder is identical to that described for 1a but using
Calculated elemental composition (based on single-crystal data
for C42H24N6O12FeGe, MW 933.11; %): C 54.06, N 9.01, H 2.59.
Found (%): C 53.70, N 8.76, H 2.49. TGA data (weight losses
inside parentheses): 277-353 °C (-59.0%); 353-598 °C (-21.0%).
6504 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
Table 1. Crystal Data Collection and Refinement Details for [M(phen)3][Ge(C2O4)3]‚xH2O [where M2+ ) Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+
(3); x ) 0.2 for 2b] and [MGe(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)]
1a
1b
2a
2b
formula
mol wt
cryst description
cryst size/mm
temp/K
instrument
cryst syst
space group
a/Å
C42H24N6O12CuGe
940.80
blue-green prisms
0.28 × 0.16 × 0.15
100(2)
Smart 1000
monoclinic
P21/n
9.4730(19)
20.528(4)
19.029(4)
90
96.19(3)
90
C42H24N6O12CuGe
940.80
blue-green prisms
0.16 × 0.15 × 0.13
150(2)
Bruker X8
monoclinic
P21/c
14.1076(9)
12.9140(8)
20.8073(13)
90
97.982(3)
90
3754.1(4)
4
1.665
1900
1.445
C42H24N6O12FeGe
933.11
red needles
0.32 × 0.12 × 0.10
150(2)
Bruker X8
monoclinic
P21/n
9.3425(5)
20.6117(9)
19.1881(9)
90
C42H24.40N6O12.20FeGe
936.72
red needles
0.30 × 0.07 × 0.02
150(2)
Bruker X8
triclinic
P1h
11.3137(5)
12.0536(5)
16.0827(11)
109.059(4)
94.664(4)
111.536
1877.10
b/Å
c/Å
R/deg
â/deg
95.410(2)
90
3678.5
γ/deg
vol./Å3
Z
3678.90(13)
4
1.699
1900
1.475
4
2
F
calcd/g cm-3
F(000)
1.685
1888
1.291
1.657
948
1.266
µ/mm-1
θ range/deg
index ranges
3.68 - 28.40
-12 e h e 12
-27 e k e 27
-25 e l e 24
65 748
1.98-25.12
-15 e h e 16
-15 e k e 15
-24 e l e 24
66 242
1.45-30.21
-13 e h e 9
-29 e k e 28
-26 e l e 26
75 853
3.59-29.13
-15 e h e 15
-16 e k e 16
-22 e l e 22
32 834
reflns collected
independent reflns
final R indices [I > 2σ(I)]
9202 (Rint ) 0.0797)
R1 ) 0.0386
wR2 ) 0.0721
R1 ) 0.0755
wR2 ) 0.0850
0.487 and -0.489
6659 (Rint ) 0.0699)
R1 ) 0.0309
wR2 ) 0.0672
R1 ) 0.0458
wR2 ) 0.0744
0.389 and -0.452
10399 (Rint ) 0.0400)
R1 ) 0.0335
wR2 ) 0.0793
R1 ) 0.0546
wR2 ) 0.0896
0.408 and -0.634
9906 (Rint ) 0.0646)
R1 ) 0.0418
wR2 ) 0.0826
R1 ) 0.0860
wR2 ) 0.0981
0.691 and -0.717
final R indices (all data)
largest diff. peak and hole/e Å3
3
5
6
formula
mol wt
cryst description
cryst size/mm
temp/K
instrument
cryst syst
space group
a/Å
C42H24N6O12NiGe
935.97
pink prisms
0.12 × 0.05 × 0.05
110(2)
Kappa FR591 2000
monoclinic
P21/n
9.4060(19)
20.647(4)
19.022(4)
90
95.09(3)
90
3679.6(13)
4
1.690
C28H18N4O10CdGe
755.45
C28H18N4O10CuGe
706.59
green prisms
0.31 × 0.20 × 0.18
100(2)
Smart 1000
orthorhombic
Pnna
15.250(3)
12.032(2)
13.582(3)
90
90
90
2492.1(9)
4
1.883
colorless prisms
0.20 × 0.12 × 0.08
150(2)
Bruker X8
monoclinic
C2/c
12.7304(2)
17.0619(3)
12.1242(2)
90
100.729(1)
90
2587.40(7)
8
1.939
1496
2.056
b/Å
c/Å
R/deg
â/deg
γ/deg
vol./Å3
Z
F
calcd/g cm-3
F(000)
1896
2.329
1420
2.134
µ/mm-1
θ range/deg
index ranges
3.83 - 27.52
-9 e h e 9
0 e k e 21
0 e l e 20
21 054
3.70 - 27.48
-16 e h e 16
-22 e k e 22
-15 e l e 15
41 597
3.70 - 26.39
-19 e h e 15
-15 e k e 15
-16 e l e 16
21 786
reflns collected
independent reflns
final R indices [I > 2σ(I)]
4523 (Rint ) 0.0531)
R1 ) 0.0522
wR2 ) 0.1382
R1 ) 0.0531
wR2 ) 0.1397
0.667 and -0.771
2956 (Rint ) 0.0273)
R1 ) 0.0153
wR2 ) 0.0392
R1 ) 0.0176
wR2 ) 0.0401
0.361 and -0.247
2557 (Rint ) 0.0975)
R1 ) 0.1050
wR2 ) 0.2622
R1 ) 0.1387
wR2 ) 0.2798
0.901 and -0.999
final R indices (all data)
largest diff. peak and hole/e Å3
instead CoC4H6O4‚4H2O as the Co2+ source. The reaction mixture
contained 0.050 g of GeO2, 0.180 g of H2C2O4‚2H2O, 0.080 g of
CoC4H6O4‚4H2O, 0.200 g of phen, and 15 g of H2O (approximate
molar composition of 1GeO2:3H2C2O4:2/3CoC4H6O4:2phen). Yield
83.1% based on CoC4H6O4‚4H2O.
Calculated elemental composition (for C42H24N6O12CoGe, MW
936.21; %): C 53.88, N 8.98, H 2.58. Found (%): C 52.00, N 8.63,
H 2.54. TGA data (weight losses inside parentheses): 272-360 °C
(-46.7%); 360-598 °C (-33.3%). Selected FT-IR and Raman
(inside parentheses and in italics) data (in cm-1): ν(C-H, aromatic)
) 3061w, 2925w, (3081); ν(uncoordinated carbonyl groups) )
1735s, (1763, 1721); νasym(-CO2-) ) 1672m, 1624w, 1605w,
1583w, (1626, 1604, 1586); ν(C-C, skeletal vibrations) ) 1517m,
1496w, (1517, 1453); δ(C-H) ) 1426s, (1422); νsym(-CO2-) )
1426s, 1316s, (1422, 1362, 1345, 1306); ν(C-N, heteroaromatic
amines) ) 1316s, (1306); ν(C-O) ) 1227m, 1197w, 1187w,
1141w, (1259, 1145); ν(C-C skeletal stretching mode) ) 1104w,
(1054); ν(C-H) ) 992w, 952w, (901); ν(C-C and Ge-O) )
Inorganic Chemistry, Vol. 46, No. 16, 2007 6505

Shi et al.
δ(CO2-) ) 724s, (736); γ(C-H) ) 647w, 574w, (560); ν(M-N)
and F(CO2 out-of-plane) ) 483m, 429w, (432).
Table 2. Selected Bond Lengths (Å) for the Octahedral {MN6} and
{GeO6} Coordination Environments Present in Compounds 1-3 (M2+
-
)
Cu2+, Fe2+, or Ni2+
)
Single-Crystal X-ray Diffraction. Crystals of compounds
[M(phen)3][Ge(C2O4)3]‚xH2O [where M2+ ) Cu2+ (1a and 1b), Fe2+
(2a and 2b), Ni2+ (3); x ) 0.2 for 2b] and [MGe(phen)2(µ2-OH)2-
(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+ (6)] suitable for single-
crystal X-ray diffraction analysis were manually harvested from
the reaction vials and mounted on glass fibers using FOMBLIN Y
perfluoropolyether vacuum oil (LVAC 25/6) purchased from
Aldrich.45 Data were collected in Nonius-based Kappa Bruker
diffractrometers equipped with charge-coupled device (CCD) area
detectors and Mo KR (λ ) 0.7107 Å) or Cu KR (λ ) 1.54180 Å)
(for 3) radiation. Data were corrected for Lorenztian and polarization
effects. Absorption corrections were applied using the multiscan
semiempirical method implemented in SADABS.46 Structures were
solved using the direct methods of SHELXS-97,47 which
allowed immediate location of the heaviest atoms. The re-
maining non-hydrogen atoms were located from difference
Fourier maps calculated from successive full-matrix least-squares
refinement cycles on F2 using SHELXL-97.48 All non-hydrogen
atoms were successfully refined using anisotropic displacement
parameters.
1a (Cu2+
)
1b (Cu2+
)
2a (Fe2+
)
2b (Fe2+
)
3 (Ni2+
)
M(1)-N(1)
M(1)-N(2)
M(1)-N(3)
M(1)-N(4)
M(1)-N(5)
M(1)-N(6)
Ge(1)-O(1)
Ge(1)-O(3)
Ge(1)-O(5)
Ge(1)-O(7)
Ge(1)-O(9)
2.049(2)
2.025(2)
2.316(2)
2.059(2)
2.042(2)
2.275(2)
1.883(2)
1.886(2)
1.875(2)
1.876(2)
1.876(2)
2.374(2) 1.992(2)
2.031(2) 1.974(2)
2.021(2) 1.984(2)
2.317(2) 1.978(2)
2.048(2) 1.990(2)
2.056(2) 1.978(1)
1.889(2) 1.891(1)
1.872(2) 1.892(1)
1.974(2) 2.091(3)
1.986(2) 2.081(3)
1.985(2) 2.088(3)
1.985(2) 2.076(3)
2.002(2) 2.097(3)
1.972(2) 2.085(3)
1.897(2) 1.865(2)
1.894(2) 1.880(2)
1.870(2) 1.888 (1) 1.893(2) 1.871(2)
1.879(2) 1.878(1)
1.895(2) 1.884(1)
1.888(2) 1.878(1)
1.890(2) 1.879(2)
1.881(2) 1.886(3)
1.890(2) 1.881(2)
Ge(1)-O(11) 1.870(2)
892w, 867w, 845m, 819s, (869); δ(CO2-) ) 772w, 725s, (733);
γ(C-H) ) 644w, 602w, (640, 598, 558); ν(M-N) and F(CO2
) 470m, 425w, (425).
-
)
Synthesis of [CdGe(phen)2(µ2-OH)2(C2O4)2] (5). The synthetic
procedure used to isolate [CdGe(phen)2(µ2-OH)2(C2O4)2] as a
colorless single-crystalline phase is identical to that described for
1a but using instead CdC4H6O4‚2H2O as the Cd2+ source. The
reaction mixture contained 0.100 g of GeO2, 0.360 g of H2C2O4‚
H2O, 0.080 g of CdC4H6O4‚2H2O, 0.200 g of phen, and 15 g of
H2O (approximate molar composition of 1GeO2:3H2C2O4:1/
3CdC4H6O4‚2H2O:1phen). Yield 88.2% based on CdC4H6O4.
Calculated elemental composition (for C28H18N4O10CdGe, MW
755.45, %): C 44.52, N 7.42, H 2.40. Found (%): C 43.78, N
7.29, H 2.71. TGA data (weight losses inside parentheses): 30-
260 °C (-0.6%); 260-343 °C (-36.4%); 343-598 °C (-29.1%).
Selected FT-IR and Raman (inside parentheses and in italics) data
(in cm-1): ν(O-H as bridging ligand) ) 3321m; νasym(C-H,
aromatic rings) ) 3074w, (3080, 3052); ν(uncoordinated carbonyl
groups) ) 1723s; νasym(-CO2-) ) 1680s, 1621m, 1597m, (1606);
ν(C-C, heteroaromatic amines) ) 1517m, (1452); δ(C-H) )
1428s, (1412); νsym(-CO2-) ) 1428s, 1359s, (1412, 1375, 1345,
1305); ν(C-N, heteroaromatic amines) ) 1359s; (1345, 1305);
ν(C-O) ) 1246m, 1225m, 1138w, (1257, 1196, 1156); ν(C-C
Hydrogen atoms bound to carbon were located at their idealized
positions by employing the HFIX 43 instruction in SHELXL-9748
and included in subsequent refinement cycles in riding motion
approximation with isotropic thermal displacement parameters (Uiso)
fixed at 1.2Ueq of the carbon atom to which they were attached. In
compounds 5 and 6 the hydrogen atoms associated with the µ2-
bridging hydroxyl groups were markedly visible in the last
difference Fourier maps synthesis. These atoms have been included
in the final structural models with the O-H distances restrained to
0.95(1) Å in order to ensure a chemically reasonable geometry for
these moieties, and with Uiso fixed at 1.5Ueq of the parent oxygen
atom.
In compound 2b a partially occupied water molecule of crystal-
lization [O(1W)] was directly located from difference Fourier maps
and refined using an isotropic displacement parameter and a fixed
partial site occupancy of 20% (determined previously by unre-
strained refinement of this variable). Even though hydrogen atoms
belonging to this chemical moiety could not be directly located
from difference Fourier maps and no attempt was made to place
these in approximate calculated positions, they have been included
in the empirical formula of the compound. As mentioned in the
previous section, crystals of 6 were obtained as a minor phase in
the synthesis of 1a. Crystals systematically showed poor quality
associated with diffuse scattering at high angle (therefore, the high
Rint; see Table 1).
skeletal stretching mode) ) 1100w, (1109); ν(C-H) ) 1053w,
(1055); ν(C-C and Ge-O) ) 894w, 853s, 808m, (865); δ(CO2
-
)
) 773w, 726s, (728, 711); γ(C-H) ) 642m, 597m, (583, 556);
ν(M-N) and F(CO2-) ) 476m, 420w, (422).
Synthesis of [CuGe(phen)2(µ2-OH)2(C2O4)2] (6). [CuGe(phen)2-
(µ2-OH)2(C2O4)2] was initially isolated from the reaction vials of
1a as a minor impurity. The pure phase was isolated using the same
synthetic procedure with a reaction mixture composed of 0.050 g
of GeO2, 0.120 g of H2C2O4‚H2O, 0.100 g of CuC4H6O4‚H2O,
0.200 g of phen, and 15 g of H2O (approximate molar composition
of 1GeO2:2H2C2O4:1CuC4H6O4:2phen). Yield 70.8% based on
CuC4H6O4‚H2O.
Calculated elemental composition (for C28H18N4O10CuGe, MW
706.59; %): C 47.60, N 7.93, H 2.57. Found (%): C 47.96,
N 7.90, H 2.55. TGA data (weight losses inside parentheses):
105-197 °C (-0.5%); 197-342 °C (-31.6%); 342-599 °C
(-42.4%). Selected FT-IR and Raman (inside parentheses and in
italics) data (in cm-1): ν(O-H as bridging ligand) ) 3396m;
Information concerning the crystallographic data collection and
structure refinement are collected in Table 1. Selected bond lengths
and angles for compounds 1 to 3 are summarized in Tables 2 and
3, respectively, while for compounds 5 and 6 they are collected in
Table 9. Geometrical details on the weak C-H‚‚‚O hydrogen-
bonding interactions interconnecting cationic [M(phen)3]2+ and
anionic [Ge(C2O4)3]2- moieties in compounds 1-3 are collected
ν
asym(C-H, aromatic rings) ) 3086w, (3078); ν(uncoordinated
carbonyl groups) ) 1719s; νasym(-CO2-) ) 1660s, 1597s, (1607);
ν(C-C, heteroaromatic amines) ) 1519m, (1457); δ(C-H) )
1428s, (1429); νsym(-CO2-) ) 1428s, 1363s, (1429, 1310);
ν(C-N, heteroaromatic amines) ) 1363s; (1310); ν(C-O) )
1296m, 1248m, 1145w; ν(C-C skeletal stretching mode) ) 1107w,
(1050); ν(C-H) ) 1034w; ν(C-C and Ge-O) ) 854m, 808m;
(45) Kottke, T.; Stalke, D. J. Appl. Crystallogr. 1993, 26, 615-619.
(46) Sheldrick, G. M. SADABS V.2.01, Bruker/Siemens Area Detector
Absorption Correction Program; Bruker AXS: Madison, WI, 1998.
(47) Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, 1997.
(48) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, 1997.
6506 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
Table 3. Octahedral Angles (deg) for {MN6} and {GeO6} Coordination Environments Present in Compounds 1-3 (M2+ ) Cu2+, Fe2+, or Ni2+
)
1a (Cu2+
)
1b (Cu2+
)
2a (Fe2+
)
2b (Fe2+
)
3 (Ni2+
)
N(1)-M(1)-N(2)
N(1)-M(1)-N(3)
N(1)-M(1)-N(4)
N(1)-M(1)-N(5)
N(1)-M(1)-N(6)
N(2)-M(1)-N(3)
N(2)-M(1)-N(4)
N(2)-M(1)-N(5)
N(2)-M(1)-N(6)
N(3)-M(1)-N(4)
N(3)-M(1)-N(5)
N(3)-M(1)-N(6)
N(4)-M(1)-N(5)
N(4)-M(1)-N(6)
N(5)-M(1)-N(6)
O(1)-Ge(1)-O(3)
O(1)-Ge(1)-O(5)
O(1)-Ge(1)-O(7)
O(1)-Ge(1)-O(9)
O(1)-Ge(1)-O(11)
O(3)-Ge(1)-O(5)
O(3)-Ge(1)-O(7)
O(3)-Ge(1)-O(9)
O(3)-Ge(1)-O(11)
O(5)-Ge(1)-O(7)
O(5)-Ge(1)-O(9)
O(5)-Ge(1)-O(11)
O(7)-Ge(1)-O(9)
O(7)-Ge(1)-O(11)
O(9)-Ge(1)-O(11)
81.32(9)
99.39(9)
174.52(9)
94.85(9)
91.42(9)
93.74(9)
95.65(9)
171.50(9)
94.49(9)
76.18(9)
94.37(9)
167.28(8)
88.75(9)
93.37(9)
77.95(9)
85.83(9)
87.10(8)
172.12(8)
90.29(8)
93.86(9)
93.72(9)
90.45(9)
173.86(8)
88.92(9)
86.21(8)
90.83(9)
177.25(9)
93.97(8)
93.01(9)
86.59(8)
75.98(8)
105.32(8)
173.47(8)
89.81(8)
84.19(8)
92.17(9)
98.11(8)
165.61(8)
94.70(9)
77.42(8)
93.83(8)
169.42(9)
95.96(8)
93.63(8)
81.38(9)
86.52(8)
89.49(8)
175.57(8)
88.28(8)
95.29(8)
95.83(8)
92.43(8)
171.66(8)
88.16(8)
86.33(8)
90.64(8)
173.95(8)
93.24(8)
88.98(8)
85.82(8)
82.58(6)
96.45(6)
177.27(6)
93.83(6)
89.55(6)
92.65(6)
94.93(6)
174.87(6)
93.38(6)
82.51(6)
91.40(6)
172.00(6)
88.72(6)
91.73(6)
82.89(6)
85.90(6)
87.01(6)
172.11(6)
90.09(6)
94.15(6)
93.75(6)
90.83(6)
173.93(6)
89.28(6)
86.04(6)
90.59(6)
176.83(6)
93.70(6)
92.98(6)
86.47(6)
83.09(9)
93.25(9)
174.41(9)
97.32(9)
91.98(9)
92.12(9)
92.93(9)
177.43(9)
94.83(9)
82.94(9)
90.38(9)
171.75(9)
86.82(9)
92.26(9)
82.63(9)
85.64(8)
88.12(9)
170.87(9)
92.15(9)
95.06(9)
93.89(9)
88.05(9)
173.83(9)
88.82(9)
85.72(9)
91.79(9)
175.97(9)
94.77(9)
91.40(9)
85.63(9)
80.14(10)
95.43(10)
172.97(10)
91.81(10)
88.78(10)
90.98(10)
94.51(10)
168.24(10)
91.84(10)
80.01(10)
98.36(10)
175.28(10)
94.14(10)
95.99(11)
79.34(10)
86.57(10)
93.26(10)
177.28(10)
88.78(11)
93.81(11)
93.64(10)
90.86(10)
173.54(10)
89.92(10)
86.04(10)
91.09(10)
172.26(10)
93.86(10)
87.04(10)
85.93(10)
Table 4. Geometrical Parameters for the Possible Weak C-H‚‚‚O
Hydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anions
and [Cu(phen)3]2+ Cations in the Polymorphic Structure of Compound
1aa
Table 5. Geometrical Parameters for the Possible Weak C-H‚‚‚O
Hydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anions
and [Cu(phen)3]2+ Cations in the Polymorphic Structure of Compound
1ba
C-H‚‚‚O
d
C‚‚‚O (Å)
(CHO) (deg)
C-H‚‚‚O
d
C‚‚‚O (Å)
(CHO) (deg)
C(7)-H(7)‚‚‚O(6)i
3.229(4)
3.245(4)
3.192(4)
2.997(3)
3.296(4)
3.502(4)
3.147(3)
3.266(4)
3.163(4)
3.375(4)
3.125(4)
3.515(4)
125
132
115
109
138
153
126
117
129
141
130
150
C(7)-H(7)‚‚‚O(1)i
3.339(3)
3.393(3)
3.577(3)
3.081(3)
3.400(4)
3.235(3)
3.158(3)
3.182(3)
3.244(3)
3.362(3)
3.360(4)
3.117(4)
3.269(4)
3.273(3)
143
161
166
116
131
115
115
111
137
135
142
130
116
143
C(8)-H(8)‚‚‚O(8)i
C(9)-H(9)‚‚‚O(8)ii
C(14)-H(14)‚‚‚O(10)ii
C(18)-H(18)‚‚‚O(4)
C(20)-H(20)‚‚‚O(12)iii
C(21)-H(21)‚‚‚O(11)iii
C(28)-H(28)‚‚‚O(1)iv
C(29)-H(29)‚‚‚O(2)
C(30)-H(30)‚‚‚O(2)
C(33)-H(33)‚‚‚O(4)i
C(38)-H(38)‚‚‚O(6)v
C(41)-H(41)‚‚‚O(10)vi
C(14)-H(14)‚‚‚O(9)iii
C(15)-H(15)‚‚‚O(6)ii
C(15)-H(15)‚‚‚O(10)iii
C(18)-H(18)‚‚‚O(7)iv
C(19)-H(19)‚‚‚O(10)i
C(20)-H(20)‚‚‚O(10)i
C(21)-H(21)‚‚‚O(10)v
C(27)-H(27)‚‚‚O(7)vi
C(31)-H(31)‚‚‚O(12)vii
C(40)-H(40)‚‚‚O(2)viii
C(41)-H(41)‚‚‚O(2)vi
C(42)-H(42)‚‚‚O(12)ix
a Symmetry transformations used to generate equivalent atoms: (i) 1/2
- x, -1/2 + y, 1.5 - z; (ii) -1.5 + x, 1/2 - y, -1/2 + z; (iii) -x, -y, 2
- z; (iv) 1 - x, -y, 2 - z; (v) 1.5 - x, -1/2 + y, 1.5 -z; (vi) -1/2 + x,
1/2 - y, -1/2 + z.
a Symmetry transformations used to generate equivalent atoms: (i) 1 -
x, 1/2 + y, 1/2 - z; (ii) 1 - x, 1 - y, -z; (iii) -1 + x, 1/2 - y, -1/2 +
z; (iv) 1 - x, -y, -z; (v) -1 + x, y, z; (vi) 1 - x, -1/2 + y, 1/2 - z;
(vii) 1 - x, 1/2 + y, 1/2 - z; (viii) 1 - x, 1/2 + y, 1/2 - z; (ix) 1 - x, -y,
-z.
in Tables 4-8. Schematic drawings for all structures have been
prepared using Crystal Diamond49 and the X-seed software
platform.50,51
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre (CCDC) as supplementary
publication numbers: CCDC-627717 to -627721 (compounds
1-3), -628767 and -628768 (compounds 5 and 6, respectively).
Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 2EZ, U.K. [FAX: (+44)
1223 336033; e-mail: deposit@ccdc.cam.ac.uk].
Powder X-ray Diffraction. PXRD data of [Co(phen)3][Ge-
(C2O4)3] (4) were collected at ambient temperature on a X’Pert
MPD Philips diffractometer (Cu KR X-radiation, λ ) 1.54060 Å)
equipped with a X’Celerator detector, a curved graphite-mono-
chromated radiation, and a flat-plate sample holder in a Bragg-
Brentano para-focusing optics configuration (40 kV, 50 mA).
Intensity data were collected in continuous scanning mode in the
range ca. 4 e 2θ° e 55.
The PXRD pattern was indexed with the routines provided with
the program DICVOL0452 using the first 20 well-resolved reflec-
(49) Brandenburg, K. DIAMOND, Version 3.1d; Crystal Impact GbR:
Bonn, Germany, 2006.
(50) Barbour, L. J. J. Supramol. Chem. 2001, 1, 189-191.
(51) Atwood, J. L.; Barbour, L. J. Cryst. Growth Des. 2003, 3, 3-8.
(52) Boultif, A.; Louer, D. J. Appl. Crystallogr. 2004, 37, 724-731.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6507

Shi et al.
Le Bail whole-powder-diffraction-pattern profile fitting58 (see Figure
S1 in the Supporting Information) was performed with the
FullProf.2k software package,53,54 employing a typical pseudo-Voigt
peak-shape function, and in the last stages of the fitting process
the unit cell parameters and typical profile parameters, such as scale
factor, zero shift, Caglioti function values, and two asymmetry
parameters were allowed to refine freely. Fixed background points
were employed. The refined unit cell parameters converged to a )
19.204(2) Å, b ) 20.839(2) Å, c ) 9.511(1) Å, and â ) 95.066-
(6)° (RBragg ) 1.06% and ø2 ) 3.79)
Table 6. Geometrical Parameters for the Possible Weak C-H‚‚‚O
Hydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anions
and [Fe(phen)3]2+ Cations in 2aa
C-H‚‚‚O
d
C‚‚‚O (Å)
(CHO) (deg)
C(7)-H(7)‚‚‚O(6)i
3.187(2)
3.294(4)
3.028(2)
3.369(3)
3.551(3)
3.146(2)
3.186(2)
3.388(3)
3.157(3)
3.246(2)
3.564(3)
124
135
105
128
163
126
108
137
125
118
156
C(8)-H(8)‚‚‚O(8)i
C(18)-H(18)‚‚‚O(4)
C(20)-H(20)‚‚‚O(12)ii
C(21)-H(21)‚‚‚O(11)ii
C(28)-H(28)‚‚‚O(2)iii
C(30)-H(30)‚‚‚O(2)
C(33)-H(33)‚‚‚O(4)i
C(38)-H(38)‚‚‚O(6)iv
C(39)-H(39)‚‚‚O(6)iv
C(41)-H(41)‚‚‚O(10)v
Results and Discussion
A series of highly crystalline heterodimetallic complexes
composed of tris(oxalato-O,O′)germanate anions and cationic
complexes of transition metals (M) coordinated to 1,10′-
phenanthroline (phen) residues have been isolated using mild
hydrothermal synthesis, from reaction mixtures containing
germanium(IV) oxide, oxalic acid, phen, and various M salts
(see Experimental Section for details). Compounds have been
a Symmetry transformations used to generate equivalent atoms: (i) 1.5
- x, -1/2 + y, 1.5 - z; (ii) 2 - x, -y, 1 - z; (iii) 1 - x, -y, 1 - z;
(iv) 1/2 - x, -1/2 + y, 1.5 - z; (v) 1/2 + x, 1/2-y, 1/2 + z.
Table 7. Geometrical Parameters for the Possible Weak C-H‚‚‚O
Hydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anions
and [Fe(phen)3]2+ Cations in the Solvate Structure of Compound 2ba
formulated as [M(phen)3][Ge(C2O4)3]‚xH2O [where M2+
)
C-H‚‚‚O
d
C‚‚‚O (Å)
(CHO) (deg)
Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), and Co2+ (4);
x ) 0.2 for compound 2b] on the basis of single-crystal or
powder X-ray diffraction studies and elemental analysis. EDS
studies provided information on (1) the presence of Ge and
the metallic centers on individual crystals of each compound
and (2) the ratios of Ge:M, typically 1:1.
C(14)-H(14)‚‚‚O(4)i
C(15)-H(15)‚‚‚O(5)i
C(16)-H(16)‚‚‚O(6)ii
C(20)-H(20)‚‚‚O(2)iii
C(30)-H(30)‚‚‚O(7)iv
C(31)-H(31)‚‚‚O(9)v
C(32)-H(32)‚‚‚O(10)vi
C(39)-H(39)‚‚‚O(2)
C(40)-H(40)‚‚‚O(4)vii
C(41)-H(41)‚‚‚O(4)vii
C(42)-H(42)‚‚‚O(3)iv
C(42)-H(42)‚‚‚O(4)iv
3.362(4)
3.417(4)
3.513(4)
3.335(5)
3.196(4)
3.205(5)
3.225(4)
3.110(3)
3.117(3)
3.181(4)
3.037(3)
3.468(3)
131
160
162
133
127
142
120
122
120
117
102
146
Crystalline phases were directly isolated from the autoclave
contents in generous yields and usually as large single
crystals, except for 4 which could only be synthesized as a
microcrystalline powder (Figure 1). Phase purity and ho-
mogeneity of the bulk samples of 1b and 2-4 have been
confirmed by comparing the experimental powder X-ray
diffraction patterns with simulations based on single-crystal
data. Compound 1a was systematically isolated with a small
amount of compound 6 which could not be eliminated either
at the synthesis stage or after. Nevertheless, according to
the CHN elemental composition of several representative
bulk samples of 1a we determined that the amount of this
impurity was quite small. However, during our synthetic
attempts to eliminate this second-phase (by varying the
composition of the reaction mixture used to isolate 1a) a
second polymorphic (and pure) phase was isolated for a
slightly higher amount of phen in the reaction mixture (see
Experimental Section for details on the synthetic procedures).
It is also of considerable interest to mention that for Fe2+
two structures could also be isolated, [Fe(phen)3][Ge(C2O4)3]
(2a) and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b), with the latter
a Symmetry transformations used to generate equivalent atoms: (i) 2 -
x, 2 - y, z; (ii) 2 + x, 1 + y, z; (iii) 2 - x, 2 - y, 1 - z; (iv) 1 + x, 1 +
y, z; (v) 1 + x, y, z; (vi) 1 - x, 2 - y, 1 - z; (vii) 1 - x, 2 - y, z.
Table 8. Geometrical Parameters for the Possible Weak C-H‚‚‚O
Hydrogen-Bonding Interactions Interconnecting [Ge(C2O4)3]2- Anions
and [Ni(phen)3]2+ Cations in 3a
C-H‚‚‚O
C(9)-H(9)‚‚‚O(10)i
d
C‚‚‚O (Å)
(CHO) (deg)
3.358(4)
3.129(4)
3.211(4)
3.295(4)
3.183(5)
3.045(5)
3.313(5)
3.510(5)
3.148(5)
3.650(5)
3.159(5)
137
128
127
132
115
112
133
158
126
173
131
C(14)-H(14)‚‚‚O(8)ii
C(19)-H(19)‚‚‚O(8)i
C(20)-H(20)‚‚‚O(6)i
C(26)-H(26)‚‚‚O(4)iii
C(30)-H(30)‚‚‚O(10)iv
C(32)-H(32)‚‚‚O(2)v
C(33)-H(33)‚‚‚O(1)v
C(40)-H(40)‚‚‚O(11)v
C(40)-H(40)‚‚‚O(12)vi
C(42)-H(42)‚‚‚O(12)iv
a Symmetry transformations used to generate equivalent atoms: (i) 1.5
- x, -1/2 + y, 1.5 - z; (ii) 1/2 - x, -1/2 + y, 1.5 - z; (iii) 1/2 - x, 1/2
- y, -1/2 - z; (iv) -1 + x, y, -1 + z; (v) 2 - x, -y, 1-z; (vi) 1 - x, -y,
1-z.
(54) Roisnel, T.; Rodriguez-Carvajal, J. WinPLOTR [June 2005]-A Win-
dows Tool for Powder Diffraction Pattern Analysis. Materials Science
Forum, Proceedings of the Seventh European Powder Diffraction
Conference (EPDIC 7); Delhez, R., Mittenmeijer, E. J., Eds.; 2000,
pp 118-123.
(55) Boultif, A.; Louer, D. J. Appl. Crystallogr. 1991, 24, 987-993.
(56) Louer, D. In Automatic Indexing: Procedures and Applications,
Accuracy in Powder Diffraction II; Gaithersburg, MD, 1992; pp 92-
104.
(57) Laugier, J.; Bochu, B. CHECKCELL-A Software Performing Automatic
Cell/Space Group Determination, Collaborative Computational Project
Number 14 (CCP14), Laboratoire des Mate´riaux et du Ge´nie Physique
de l’Ecole Supe´rieure de Physique de Grenoble (INPG), France, 2000.
(58) LeBail, A.; Duroy, H.; Fourquet, J. L. Mater. Res. Bull. 1988, 23,
447-452.
tions (located using the derivative-based peak search algorithm
provided with Fullprof.2k)53,54 and a fixed absolute error on each
line of 0.03° 2θ. Initial unit cell metrics were obtained with
reasonable figures-of-merit: M(20)55 ) 12.5 and F(20)56 ) 30.2;
zero shift of -0.0436°. Analysis of the systematic absences using
CHECKCELL57 unambiguously confirmed space group P21/n. A
(53) Rodriguez-Carvajal, J. FULLPROF-A Program for RietVeld Refinement
and Pattern Matching Analysis, Abstract of the Satellite Meeting on
Powder Diffraction of the XV Congress of the IUCR, Toulouse,
France, 1990; p 127.
6508 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
Figure 1. SEM images of [M(phen)3][Ge(C2O4)3] crystals with M2+ ) Ni2+ (3) (right) and Co2+ (4) (left).
Table 9. Selected Bond Lengths (Å) and Angles (deg) for the Octahedral {MN4O2} and {GeO6} Coordination Environments Present in Compounds 5
a
and 6 (M2+ ) Cd2+ or Cu2+
)
bond lengths (Å)
5 (Cd2+ 6 (Cu2+
bond angles (deg)
)
)
5 (Cd2+
)
6 (Cu2+
)
M(1)-N(1)
M(1)-N(2)
M(1)-O(5)
2.311(1)
2.339(1)
2.297(1)
1.989(1)
2.138(1)
2.206(9)
N(1)-M(1)-N(2)
N(1)-M(1)-O(5)
N(1)-M(1)-N(1)i
N(1)-M(1)-N(2)i
N(1)-M(1)-O(5)i
N(2)-M(1)-O(5)
N(2)-M(1)-N(2)i
N(2)-M(1)-O(5)i
O(5)-M(1)-O(5)i
O(1)-Ge(1)-O(3)
O(1)-Ge(1)-O(5)
O(1)-Ge(1)-O(1)i
O(1)-Ge(1)-O(3)i
O(1)-Ge(1)-O(5)i
O(3)-Ge(1)-O(5)
O(3)-Ge(1)-O(3)i
O(3)-Ge(1)-O(5)i
O(5)-Ge(1)-O(5)i
72.32(4)
88.63(4)
157.40(6)
93.03(4)
110.67(4)
97.08(4)
100.39(6)
162.11(4)
65.81(5)
83.89(4)
92.18(5)
89.19(6)
87.14(4)
175.64(4)
97.12(5)
167.40(6)
92.04(5)
86.75(7)
81.4(4)
89.2(4)
170.2(6)
93.2(4)
98.9(4)
89.3(3)
112.7(5)
158.0(3)
68.8(4)
83.8(4)
175.7(4)
89.2(5)
87.5(4)
92.4(4)
92.2(4)
167.8(5)
96.7(4)
86.3(6)
Ge(1)-O(1)
Ge(1)-O(3)
Ge(1)-O(5)
1.941(1)
1.899(1)
1.817(1)
1.951(8)
1.898(8)
1.823(8)
a Symmetry transformation used to generate equivalent atoms: (i) -x, y, 1.5 - z.
being a solvate of the former and typically obtained for a
slightly higher concentration of oxalic acid in the reaction
mixture (see Experimental Section). This extra partially
occupied water molecule of crystallization induces long-range
structural modifications in the crystal packing, namely, a
reduction in crystal symmetry from the monoclinic to the
triclinic crystal systems (see structural details in the following
paragraphs).
Structural Details of the [Ge(C2O4)3]2- Anion. The
chemical moiety common to structures 1-4 is the divalent
tris(oxalate-O,O′)germanate anion, [Ge(C2O4)3]2- (Figure 2
and Scheme 1). A search in the literature and in the CSD39,40
reveals only a handful of crystallographic reports41-44
describing this anion which, invariably, shows identical
coordination geometry for all compounds, including those
reported herein. The Ge4+ center appears coordinated to three
oxalate anions (coordinated via a typical anti,anti-chelate
bidentate fashion), describing a slightly distorted {GeO6}
octahedral coordination fashion as depicted in Figure 2. The
Ge-O bonds (for all five crystal structure determinations
reported here) are found in the 1.865(2)-1.897(2) Å (Table
2), while the cis and trans O-Ge-O octahedral angles are
instead in the 85.64(8)-95.83(8)° and 170.87(9)-177.28-
(10)° ranges, respectively (Table 3). These values are in good
agreement with those described for the aforementioned
related compounds available in the literature, which show
an average Ge-O bond length of ca. 1.88 Å plus average
cis (or chelate bite angle) and trans O-Ge-O octahedral
angles of 85.7° and 173.6°, respectively.41-44
Crystal Structure Description of [Cu(phen)3][Ge-
(C2O4)3] (1a and 1b). Two crystalline forms of [Cu(phen)3]-
[Ge(C2O4)3], 1a and 1b, have been isolated from hydrother-
mal synthesis (see Experimental Section), crystallizing in the
P21/n and P21/c monoclinic space groups, respectively. For
both crystalline materials the asymmetric unit comprises two
discrete (and charged) crystallographically independent
divalent residues: one [Cu(phen)3]2+ cation plus one
[Ge(C2O4)3]2- anion (Figure 3).
The crystallographically independent Cu2+ centers in 1a
and 1b are coordinated by three phen organic ligands via a
typical N,N-chelating coordination fashion, leading to dis-
torted {CuN6} octahedral coordination geometries evidencing
the typical Jahn-Teller distortion expected for these d9
metallic centers: while the equatorial Cu-N bond lengths
are found in the 2.021(2)-2.059(2) Å range, the apical
interactions are much longer and within the 2.275(2)-
2.374(2) Å range (Table 2), thus leading to a tetragonal
distortion of the {CuN6} octahedra. The former bond lengths
are well within the expected values, as revealed by a search
in the CSD for structures containing [Cu(phen)3]2+ cations
(15 entries; range 2.01-2.34 Å), however, the latter values
are slightly longer, in particular for 1b (see Table 2). Such
abnormal long Cu-N interactions with phen residues can
be rationalized by taking into account intermolecular interac-
Inorganic Chemistry, Vol. 46, No. 16, 2007 6509

Shi et al.
intermolecular C-H‚‚‚O weak hydrogen bonds (not shown;
Tables 4 and 5 collect some geometrical details of the most
relevant and chemically feasible interactions) plus interac-
tions of the C-H‚‚‚π type and π-π stacking between
neighboring phen residues belonging to distinct cationic
residues (Figure 4).59 These supramolecular networks of weak
intermolecular interactions establish physical connections
between individual moieties and are responsible for com-
pletely distinct packing arrangements, as shown in Figure
5. Moreover, these interactions are ultimately the main reason
responsible for the isolation of two distinct crystalline forms.
In 1a the [Cu(phen)3]2+ cationic residues pack in chain-like
arrangements along the [100] and [001] crystallographic
directions (Figure 4a and 4b). While down the [100] direction
adjacent [Cu(phen)3]2+ cations interact only via C-H‚‚‚π
contacts [see Figure 4a; π represents the centroid of the
neighboring adjacent aromatic ring; approximate C‚‚‚π
distances: H(19) 3.34 Å, H(20) 3.22 Å, H(40) 3.31 Å, H(41)
3.36 Å], along the [001] direction connections between
neighboring complexes alternate between π-π stacking and
C-H···π interactions [C(8)-H(8)‚‚‚π with C‚‚‚π distance of
3.22 Å; see Figure 4b]. In 1b only one structurally relevant
C-H‚‚‚π interaction was observed along the [001] direction
of the unit cell [Figure 4c; C(29)sH(29)‚‚‚π with C‚‚‚π
average distance of 3.20 Å]. Noteworthy is the fact that this
contact seems to promote the unusually long Cu-N bonds
discussed above. Indeed, in order to maximize the geometry
associated with this C-H‚‚‚π interaction, one coordinated
phen residue needs to be slightly rotated. This leads, on one
hand, to longer bond lengths (because of the structural
rigidity of this organic ligand) and, on the other, to the large
cis octahedral angles (see above). It is also of considerable
importance to mention that adjacent phen residues in 1b are
too far apart (average distance of ca. 4.3 Å), thus invalidating
the occurrence of π-π stacking (as also depicted in Figure
4c).
Figure 2. Anionic [Ge(C2O4)3]2- fragment common to structures 1-4.
The represented structure was taken from the structure of complex 1b and
is represented with thermal ellipsoids drawn at the 50% probability level
and showing the labeling scheme for all atoms. For selected bond lengths
and angles related to this moiety in structures 1-3 see Tables 2 and 3,
respectively.
Crystal Structure Description of [Fe(phen)3][Ge-
(C2O4)3] (2a) and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O (2b).
When Fe2+ is included in the reaction mixtures (see
Experimental Section) two pseudo-polymorphic crystalline
forms could be isolated with empirical formulas [Fe(phen)3]-
[Ge(C2O4)3] and [Fe(phen)3][Ge(C2O4)3]‚0.2H2O for com-
pounds 2a and 2b, respectively. Pseudo-polymorphism is
defined as crystalline forms of a given compound (host) that
differ in the chemical nature or stoichiometry of the included
solvent molecules (guest) and refers to crystalline forms with
solvent molecules as structurally relevant features of the
structure (isolated lattice sites, lattice channels, or metal-
ion-coordinated solvates).60,61
Figure 3. Two crystallographic independent chemical moieties, [M(phen)3]2+
and [Ge(C2O4)3]2-, composing the crystal structures of 1-3 {from the
refined structure of polymorph [Cu(phen)3][Ge(C2O4)3] (1b)} and showing
the labeling scheme for all non-hydrogen atoms. Atoms are drawn as thermal
ellipsoids at the 50% probability level, and hydrogen atoms have been
omitted for clarity. For selected bond lengths and angles see Tables 2 and
3, respectively.
The striking difference between these two compounds is
the presence of one partially occupied (1/5) water molecule
of crystallization in the asymmetric unit of 2b, a unique
feature among the series of compounds reported here. It is
tions, in particular the weak C-H‚‚‚O interactions which
lead to local distortions in order to promote a more effective
close packing (see following paragraphs). Structural distor-
tions associated with 1b are particularly well demonstrated
by the cis octahedral angles whose range is the largest of all
related structures reported herein (see Table 3).
(59) Russell, V.; Scudder, M.; Dance, I. Dalton Trans. 2001, 789-799.
(60) Robin, A. Y.; Fromm, K. M. Coord. Chem. ReV. 2006, 250, 2127-
2157.
(61) Bernstein, J. Organic Solid State Chemistry. In Studies in Organic
Chemistry; Desiraju, G. R., Ed.; Elsevier: Amsterdam, 1987; Vol.
32.
The most remarkable structural feature which differentiates
1a and 1b structures concerns the number and type of
6510 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
Figure 4. Close packing of cationic [Cu(phen)3]2+ fragments along the (a) [100] and (b) [001] crystallographic directions of polymorph 1a and along the
(c) [001] direction for polymorph 1b, emphasizing the C-H‚‚‚π and π-π interactions (dashed lines) interconnecting these moieties. For clarity, only the
hydrogen atoms involved in the represented interactions are shown. Geometrical details (approximate C‚‚‚π distances) on structurally relevant C-H‚‚‚π
interactions (π represents the centroid of the aromatic ring): C(19)-H(19)‚‚‚π 3.34 Å; C(20)-H(20)‚‚‚π 3.22 Å, C(40)-H(40)‚‚‚π 3.31 Å,
C(41)-H(41)‚‚‚π 3.36 Å; C(8)-H(8)‚‚‚π 3.22 Å; C(29)-H(29)‚‚‚π 3.20 Å.
also of considerable interest to note that this occurrence
seems to be the promoting structural reason for the decrease
of crystal symmetry: 2b crystallizes in the triclinic P1h space
group, while 2a (as for all remaining heterometallic complex
structures) is monoclinic (in this case described in the P21/n
space group) or higher. Disregarding the presence of water,
the asymmetric units of 2a and 2b share many similarities
with those described for the two previous compounds,
comprising two crystallographically independent and charged
ions: [Fe(phen)3]2+ and [Ge(C2O4)3]2-. The Fe2+ centers
exhibit an almost regular {FeN6} octahedral coordination
environment with the Fe-O bond lengths and cis- and trans-
N-Fe-N octahedral angles being found in the 1.972(2)-
2.002(2) Å (Table 2) and 82.58(8)-97.32(9)° and 171.75-
(9)-177.43(10)° (Table 3) ranges, respectively. These values
are in agreement with those found in similar structures
containing [Fe(phen)3]2+ complexes, as revealed by a search
in the CSD and in the literature.
interactions occur in symmetry-related pairs with the two
water molecules being separated by 4.004(2) Å. The motif
4
can be described by the R4 (16) graph set notation.62
As for 1a and 1b (see previous subsection), the crystal
structure of these two pseudo-polymorphic compounds is
assembled by extensive networks of weak CsH‚‚‚O interac-
tions involving the charged species. Chemically (and struc-
turally) possible C‚‚‚O intermolecular distances span from
3.028(2) to 3.564(3) Å for 2a (Table 6) and from 3.037(3)
to 3.513(4) Å for 2b (Table 7). In the same way as for 1a,
in 2a intermolecular interactions are composed of both Cs
H‚‚‚π and π-π contacts between phen molecules belonging
to neighboring [Fe(phen)3]2+ complexes. While along the
[100] direction connections are assured by only Cs H‚‚‚π
interactions (as in Figure 4a), parallel to the [001] direction
an alternation between CsH‚‚‚π and π-π contacts is
registered (as in Figure 4b).59 In 2b only C-H‚‚‚π interac-
tions (running parallel to the [100] crystallographic direction)
are structurally relevant as physical connections between
adjacent cationic residues (Figure 7).
The partially occupied water molecule of crystallization
[O(1W)] is strongly hydrogen bonded to two neighboring
divalent [Ge(C2O4)3]2- anionic fragments, establishing a
connection between these two moieties (Figure 6): O(1W)
donates its two hydrogen atoms to O(7) and O(10) from
distinct anions, with dO‚‚‚O of 3.031(2) and 2.881(1) Å,
respectively. As also depicted in Figure 6, these bonding
The presence of the extra solvent molecule in 2b also
induces a completely distinct packing arrangement. While
(62) Bernstein, J.; Davis, R. E.; Shimoni, L.; Chang, N. L. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1555-1573.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6511

Shi et al.
Figure 6. O-H‚‚‚O hydrogen-bonding interactions (dashed blue lines)
involving the partially occupied water molecule of crystallization in pseudo-
polymorph 2b, [Fe(phen)3][Ge(C2O4)3]‚0.2H2O, interconnecting neighboring
[Ge(C2O4)3]2- anionic fragments and leading to formation of a R4 (16) graph
4
set motif. Geometrical aspects of the represented hydrogen bonds:
O(1W)i‚‚‚O(7)iii with dO‚‚‚O of 3.031(2) Å; O(1W)i‚‚‚O(10) with dO‚‚‚O of
2.881(1) Å. Symmetry transformations used to generate equivalent atoms:
(i) 1 - x, 2 - y, 1 - z; (ii) -1 +x, y, z; (iii) -x, 2 - y, 1 - z.
with 1a and 2a from powder X-ray diffraction studies (see
details in the Experimental Section).
Crystal Structure Description of [MGe(phen)2(µ2-OH)2-
(C2O4)2] (where M2+ ) Cd2+ and Cu2+ for 5 and 6). The
neutral hetero-binuclear compounds formulated as [MGe-
(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5) and Cu2+
(6)] represent, to the best of our knowledge, the first
examples of binuclear complexes containing a neutral bis-
(oxalate-O,O′)germanium fragment, [Ge(C2O4)2], connected
by two µ2-bridging hydroxyl groups to a cationic [M(phen)2]2+
fragment (Figure 9). Moreover, a search in the literature
reveals that these two isostructural complexes are also the
first examples of hydroxyl-bridged [M(phen)2]2+ fragments,
and only a handful of structures are known to contain µ2-
oxo bridges involving this fragment.63-75
The neutral bis(oxalate-O,O′) germanium fragment, [Ge-
(C2O4)2], shares structural similarities with the [Ge(C2O4)3]2-
complex discussed above and present in structures 1-4.
However, in 5 and 6 the Ge4+ center is only coordinated to
Figure 5. Schematic representations of the crystal packing of (a) 1a (along
the [100] direction) and (b) 1b (along the [010] direction). Hydrogen atoms
have been omitted for clarity.
(63) Xiao, D. R.; Xu, Y.; Hou, Y.; Wang, E. B.; Wang, S. T.; Li, Y. G.;
Xu, L.; Hu, C. W. Eur. J. Inorg. Chem. 2004, 1385-1388.
(64) Qi, Y. J.; Wang, Y. H.; Li, H. M.; Cao, M. H.; Hu, C. W.; Wang, E.
B.; Hu, N. H.; Jia, H. Q. J. Mol. Struct. 2003, 650, 123-129.
(65) Devi, R. N.; Burkholder, E.; Zubieta, J. Inorg. Chim. Acta 2003, 348,
150-156.
for 2a the crystal packing is identical to that previously
described for 1a (as in Figure 5a), in 2b [Fe(phen)3]2+ cations
alternate along the [010] direction of the unit cell with
[Ge(C2O4)3]2- anions, almost perfectly aligned in a typical
eclipsed fashion (Figure 8). Interstitial spaces are occupied
by the hydrogen-bonded water molecules of crystallization.
Crystallographic Aspects of [Ni(phen)3][Ge(C2O4)3] (3)
and[Co(phen)3][Ge(C2O4)3] (4). [Ni(phen)3][Ge(C2O4)3] (3)
crystallizes in the monoclinic P21/n space group, as revealed
by single-crystal X-ray diffraction (Table 1), and its molec-
ular structure shares striking resemblances with those previ-
ously described for compounds 1a and 2a (see previous
sections for details on the crystal structure). Relevant
geometrical details associated with the Ge4+ and Ni2+
coordination environments of 3 are collected in Tables 2
and 3.
(66) Liu, C. M.; Zhang, D. Q.; Xiong, M.; Dai, M. Q.; Hu, H. M.; Zhu, D.
B. J. Coord. Chem. 2002, 55, 1327-1335.
(67) Lu, Y.; Wang, E. B.; Yuan, M.; Li, Y. G.; Xu, L.; Hu, C. W.; Hu, N.
H.; Jia, H. Q. Solid State Sci. 2002, 4, 449-453.
(68) Lu, Y.; Wang, E. B.; Yuan, M.; Li, Y. G.; Hu, C. W.; Hu, N. H.; Jia,
H. Q. J. Mol. Struct. 2002, 607, 189-194.
(69) Liu, C. M.; Hou, Y. L.; Zhang, J.; Gao, S. Inorg. Chem. 2002, 41,
140.
(70) Zhang, X. M.; Tong, M. L.; Chen, X. M. Chem. Commun. 2000,
1817-1818.
(71) Mizutani, M.; Tomosue, S.; Kinoshita, H.; Jitsukawa, K.; Masuda,
H.; Einaga, H. Bull. Chem. Soc. Jpn. 1999, 72, 981-988.
(72) Xu, J. Q.; Wang, R. Z.; Yang, G. Y.; Xing, Y. H.; Li, D. M.; Bu, W.
M.; Ye, L.; Fan, Y. G.; Yang, G. D.; Xing, Y.; Lin, Y. H.; Jia, H. Q.
Chem. Commun. 1999, 983-984.
(73) Reddy, K. R.; Rajasekharan, M. V.; Arulsamy, N.; Hodgson, D. J.
Inorg. Chem. 1996, 35, 2283-2286.
(74) Vincent, J. M.; Menage, S.; Latour, J. M.; Bousseksou, A.; Tuchagues,
J. P.; Decian, A.; Fontecave, M. Angew. Chem., Int. Ed. Engl. 1995,
34, 205-207.
The compound with Co2+, formulated as [Co(phen)3][Ge-
(C2O4)3] (4) on the basis of elemental analysis (and other
supporting techniques), was also found to be isostructural
(75) Tokii, T.; Ide, K.; Nakashima, M.; Koikawa, M. Chem. Lett. 1994,
441-444.
6512 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
Figure 7. Close packing of cationic [Cu(phen)3]2+ fragments in 2b along the [100] crystallographic direction, emphasizing the C-H‚‚‚π interactions
between neighboring residues. For clarity, only the hydrogen atoms involved in the represented interactions are shown. Geometrical details (approximate
C‚‚‚π distances) on structurally relevant C-H‚‚‚π interactions (π represents the centroid of the aromatic ring): C(38)-H(38)‚‚‚π 3.39 Å; C(40)-H(40)‚‚‚π
3.66 Å.
two O,O-chelate oxalate anions, with the two remaining
vacant positions in the coordination sphere being occupied
by two µ2-bridging hydroxyl groups (Figure 9). The coor-
dination environment of Ge4+ centers can thus be envisaged
as distorted octahedra, {GeO6}, with the Ge-O bonds being
found (for the two complexes) between 1.8166(10) and
1.951(8) Å while the cis and trans O-Ge-O angles are in
the 83.8(4)-97.12(5)° and 167.40(6)-175.7(4)° ranges,
respectively (Table 9). The presence of µ2-bridging hydroxyl
groups induces in the Ge4+ centers octahedral distortions
greater than those observed for the [Ge(C2O4)3]2- anions
(Table 3) with this being essentially attributed to the stronger
bonding nature of these chemical moieties. Consequently,
the registered Ge-OH bond distances are statistically smaller
(below ca. 1.82 Å) than those with oxalate anions (always
greater than ca. 1.90 Å; Table 9), even though they compare
Figure 8. Ball-and-stick packing arrangement of 2b viewed along the
crystallographic [010] direction. Hydrogen atoms have been omitted for
clarity.
well with the only report in the literature containing a Ge-
(OH)-M bridge (d(Ge-OH) of about 1.78 Å) and present
in an open-framework containing germanium clusters.76
The close packing in the solid state of individual [MGe-
Moreover, the trans effect of these µ2-OH groups in the
{GeO6} octahedra is also markedly present with the opposite
Ge-Ooxalate bonds [1.9413(10) and 1.951(8) Å for 5 and 6,
respectively] being the longest among all the structures
(phen)2(µ2-OH)2(C2O4)2] complexes is mediated by a number
of intermolecular interactions, in particular strong and highly
directional O-H‚‚‚O hydrogen bonds involving anionic [Ge-
(µ2-OH)2(C2O4)2]2- fragments belonging to neighboring
reported here.
complexes: µ2-bridging hydroxyl groups donate their hy-
The M centers exhibit distorted octahedral coordination
drogen atoms to neighboring oxalate anions [O(5)s
geometries composed by two symmetry-related N,N-chelating
H(5A)‚‚‚O(2)i; for 5, d(O‚‚‚O) ) 2.7699(15) Å with (OHO)
phen ligands plus two symmetry-related µ2-bridging hydroxyl
) 170.3(2)°; for 6, d(O‚‚‚O) ) 2.7791(13) Å with (OHO)
groups, {MN4O2} (Figure 9): the M-(N,O) bond lengths
) 168.0(1)°; symmetry operation (i) -x, -y, 1 - z], leading
are found in the 2.2967(10)-2.3385(12) and 1.989(10)-
2.206(9) Å ranges for 5 and 6, respectively; cis and trans
internal octahedral angles can be found in the 65.81(5)-
100.39(6) and 157.40(6)-162.11(4)° (for 5) and in the 68.8-
(4)-112.7(5)° and 158.0(3)-170.2(6)° ranges, respectively
(see Table 9 for details). Noteworthy is the fact that for 6
the {CuN4O2} coordination environment is not as signifi-
cantly distorted as those registered for 1a and 1b, and
consequently the Jahn-Teller distortion is not so markedly
visible. It is feasible to assume that this smaller tetragonal
distortion for 6 seems to arise mainly due to the presence of
three crystallographically independent Cu-(N,O) bond lengths,
which are all statistically distinct as summarized in Table 9.
The intermetallic Ge(1)‚‚‚M(1) separations across the hy-
droxyl µ2 bridge are 3.2487(3) and 3.1510(27) Å for 5 (Cd)
and 6 (Cu), respectively.
to formation of a R2 (12) graph set motif.62 The reciprocity
2
of these hydrogen-bonding interactions leads to formation
of 1D supramolecular tapes, ∞2[MGe(phen)2(µ2-OH)2(C2O4)2],
as depicted in Figure 10a. Interactions between adjacent tapes
are assured by cooperative π-π stacking involving the phen
residues coordinated to the M centers (Figure 11).
Thermal Analysis. The thermal stability (under a continu-
ous air flow) of [M(phen)3][Ge(C2O4)3]‚xH2O [with M2+
)
Cu2+ (1a and 1b), Fe2+ (2a and 2b), Ni2+ (3), and Co2+ (4)]
and [MGe(phen)2(µ2-OH)2(C2O4)2] [where M2+ ) Cd2+ (5)
and Cu2+ (6)] was investigated between ambient temperature
and ca. 600 °C with the registered thermograms (see Figure
S2) clearly evidencing a similar behavior for all compounds
belonging to a given family.
This study was particularly informative regarding the
subtle composition difference between pseudo-polymorphs
[Fe(phen)3][Ge(C2O4)3] (2a) and [Fe(phen)3][Ge(C2O4)3]‚
0.2H2O (2b). Indeed, for the latter compound between
(76) Lin, Z. E.; Zhang, J.; Zheng, S. T.; Yang, G. Y. Microporous
Mesoporous Mater. 2004, 74, 205-211.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6513

Shi et al.
Figure 10. (a) Schematic representation of the parallel packing of
individual [MGe(phen)2(µ2-OH)2(C2O4)2] complexes mediated by
O-H‚‚‚O hydrogen bonds (dashed blue lines) and leading to formation of
Figure 9. Schematic representation of the binuclear [CdGe(phen)2(µ2-
OH)2(C2O4)2] (5) complex, showing the atom labeling for selected atoms
and emphasizing the distorted octahedral coordination environments for the
Cd2+ and Ge4+ metal centers. Non-hydrogen atoms composing the asym-
metric unit are represented with thermal ellipsoids drawn at the 50%
probability level. Hydrogen atoms were omitted for clarity. For selected
bond lengths and angles for compounds 5 and 6 see Table 9. Symmetry
transformation used to generate equivalent atoms: (i) -x, y, 1.5 - z.
a one-dimensional supramolecular tape: 2[MGe(phen)2(µ2-OH)2(C2O4)2].
∞
(b) Magnification of a portion of the supramolecular tape emphasizing the
R2 (12) graph set motif formed between two neighboring complexes and
2
involving the µ2-bridging hydroxyl groups and coordinated oxalate anions.
Geometrical details on O(5)sH(5A)‚‚‚O(2)i: for 5, d(O‚‚‚O) ) 2.7699-
(15) Å with (OHO) ) 170.3(2)°; for 6, d(O‚‚‚O) ) 2.7791(13) Å with
(OHO) ) 168.0(1)°. Symmetry transformation used to generate equivalent
atoms: (i) -x, -y, 1 - z. For clarity, only hydrogen atoms involved in
hydrogen-bonding interactions are represented.
ambient temperature and ca. 268 °C a small continuous
weight loss of about 0.8% confirms the presence of a small
amount of water present in the structure (calculated 0.4 per
formula unit), which agrees with the structural assumptions
deduced during the single-crystal X-ray diffraction studies.
Neglecting the initial weight loss of compound 2b the
thermal decomposition of all compounds can be roughly
divided in two major stages: the first corresponds to release
of a variable amount of phen ligands, and the second is
attributed to decomposition of the [Ge(C2O4)3]2- anions. It
is noteworthy to mention that the first thermal decomposition
starts to settle in for compounds 1a and 1b at a lower
temperature (around 205 and 201 °C, respectively) than for
the remaining materials (between 268 and 280 °C) with this
phenomenon being ascribed to the stronger oxidizing proper-
ties of Cu2+ when compared with the remaining transition-
metal centers. Nevertheless, in the 200-280 °C temperature
range all materials release some phen ligands, usually
between 2 and 3 molecules (1a ca. 2.1; 1b ca. 2.5; 3 ca. 2.3;
4 ca. 2.4). In the case of the Fe2+ compounds all phen
molecules are thermally removed. Upon thermal decomposi-
tion of the [Ge(C2O4)3]2- anions, which usually starts to settle
in around 300 °C, the obtained residues are composed of a
mixture of metallic oxides which, except for 1a (due to the
presence of a small impurity in the as-synthesized material),
are in good agreement with the expected stoichiometric
quantities: for 1b, CuO + GeO2 (calculated 19.6%, observed
20.1%); for 2a and 2b, Fe2O3 + GeO2 (calculated 19.8%
and 19.7%, observed 20.0% and 20.6%, respectively); for
Figure 11. π-π Interactions (dashed green lines) interconnecting
neighboring ∞2[MGe(phen)2(µ2-OH)2(C2O4)2] supramolecular tapes. Hydrogen-
bonding interactions are represented as dashed blue lines, and hydrogen
atoms belonging to the phen residues have been omitted for clarity.
3, NiO + GeO2 (calculated 19.2%, observed 19.6%); for 4,
CoO + GeO2 (calculated 19.2%, observed 20.0%).
The thermal decomposition of compounds 5 and 6 starts
with initial residual weight losses of about 0.6% and 0.5%,
respectively, which agrees well with the release of two water
molecules per formula unit (calculated values of ca. 0.5%).
This can be attributed to destruction of the µ2 bridges which
interconnecting the metals within the complex which, as
clearly observed in the thermograms, occurs at a significantly
higher temperature for 5 than for 6. Interestingly, the same
is observed for the decomposition of the organic components
of these compounds: while for 6, at 600 °C, all the material
was entirely converted into the expected stoichiometric
6514 Inorganic Chemistry, Vol. 46, No. 16, 2007

Heterodimetallic Germanium(IV) Complex Structures
amount of CuO + GeO2 (observed residual of 25.5%,
calculated of about 26.06%), for 5 the decomposition is still
occurring. The different kinetics associated with the thermal
decomposition of 5 and 6 can be ascribed to the distinct
physical-chemical properties of the M metals composing the
bimetallic complexes with Cu2+ clearly promoting the
decomposition.
above 3300 cm-1 (centered at ca. 3321 cm-1 for 5 and ca.
3396 cm-1 for 6) and attributed to the characteristic ν(O-
H) stretching vibrational band associated with the µ2-bridging
hydroxyl groups involved in hydrogen bonds, in accord with
the crystal structure.77
Concluding Remarks
Vibrational Spectroscopy. FT-IR and Raman spectra are
particularly informative regarding the presence of the primary
building blocks of the complexes, showing the characteristic
bands of phen and oxalate organic ligands, hence fully
supporting the chemical composition and structural details
determined from the single-crystal X-ray diffraction studies.77
Specific band assignments for the most intense and diagnostic
bands are collected in the Experimental Section, while the
FT-IR spectra are provided as Supporting Information (Figure
S3).
The preparation, via typical hydrothermal approaches, of
the first bimetallic complexes containing either [Ge(C2O4)3]2-
or [Ge(C2O4)2] with M cationic complexes of 1,10′-phenan-
throline (phen) and their full structural description based on
single-crystal X-ray diffraction investigations has been
described. It was shown that the large chemical species
composing each complex structure close pack in the solid
state mediated by extensive subnetworks of intermolec-
ular interactions which include, among others, strong
O-H‚‚‚O and weak C-H‚‚‚O hydrogen-bonding interac-
tions, C-H‚‚‚π and π-π contacts.
A number of bands located between 810 and 900 cm-1
are diagnostic of the presence of coordinated oxalate anions
Acknowledgment. We are grateful to FEDER, POCI
2010, and Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT,
Portugal) for their generous financial support, funding toward
the purchase of the single-crystal diffractometer, and also
postdoctoral research grants (no. SFRH/BPD/9309/2002 (to
F.-N.S.) and SFRH/BPD/14410/2003 (to L.C.-S.)). We also
thank the EPSRC (U.K.) and the University of Leeds for
equipment funding.
to Ge4+ and attributed to the ν(C-C) and ν(Ge-Ooxalate
)
stretching vibrational modes. Several intense bands found
in the ca. 1100-1520 cm-1 spectral region are characteristic
of a number of vibrational modes of phen. A strong band
centered at ca. 1735 cm-1, particularly evident in all spectra,
strongly supports the existence of uncoordinated (and
terminal) CdO groups arising from the coordinated oxalate
anions. Moreover, the νasym(-CO2-) and νsym(-CO2-) stretch-
ing vibrational bands of oxalate groups appear in the 1676-
1580 and 1430-1310 cm-1 spectral regions, respectively,
which correspond to ∆ values between 246 and 270 cm-1,
in good agreement with the observed anti,anti-chelate
bidentate coordination fashion for these anionic moieties (see
crystallographic description of the structures).78,79
Supporting Information Available: Crystallographic informa-
tion as CIF files; Le Bail whole-powder-diffraction-pattern profile
fitting of [Co(phen)3][Ge(C2O4)3]; thermograms and FT-IR spectra
for all compounds. This material is available free of charge via the
Internet at http://pubs.acs.org.
IC700507J
In the case of 5 and 6, a broad band is markedly visible
(78) Oldham, C. Carboxylates, Squarates and Related Species. In Com-
prehensiVe Coordination Chemistry, 1st ed.; Wilkinson, S. G., Ed.;
Pergamon Press: New York, 1987; Vol. 2, pp 435-459.
(77) Socrates, G. Infrared Characteristic Group Frequencies-Tables and
Charts, 2nd ed.; John Wiley & Sons Ltd.: Baffins Lane, Chichester,
1994.
(79) Deacon, G. B.; Phillips, R. J. Coord. Chem. ReV. 1980, 33, 227-250.
Inorganic Chemistry, Vol. 46, No. 16, 2007 6515