Diphosphine and diarsine complexes of Germanium(II) halides-preparation, spectroscopic, and structural studies

Article abstract of DOI:10.1021/ic902068z

The Ge(II) halide complexes [GeX₂(L-L)] (L-L =o-C ₆H₄(PPh₂)₂, o-C₆H ₄(PMe₂)₂, Me₂P(CH₂) ₂PMe₂; X = Cl, Br, I. L-L = Et₂P(CH ₂)₂PEt₂; X = Cl or Br. L-L = o-C ₆H₄(AsMe₂)₂; X = Br or I) and [GeCI(L-L)][GeCl₃] (L-L = c-C₆H₄(AsMe ₂)₂) have been prepared and characterized by IR, ¹H and ³¹P(¹H) NMR spectroscopy, and microanalyses. The crystal structures of [GeX₂{o-C₆H ₄(PPh₂)₂}] (X = Cl, Br, I) reveal discrete mononuclear units with a very asymmetric bidentate o-C₆H ₄(PPh₂)₂ ligand and a bent GeX₂ unit. Those of [GeX₂{o-C₆H₄(PMe ₂)₂}] show symmetrically coordinated dlphosphlne with loosely associated dimer arrangements, formed through long Ge - X bridges between adjacent monomer units. [GeX₂{R₂P(CH ₂)₂PR₂}] (R = Me; X = Cl, Br, I. R = Et; X = Cl, Br) all show discrete monomer structures with 2-fold crystallographic symmetry and based upon four-coordinate Ge, with the dlphosphine chelating and approximately linear GeX₂ units. [Gel₂{c-C ₆H₄(AsMe₂)₂}] involves significant interinolecular Ge - I interactions, giving rise to a zigzag polymer chain. Finally, the structure of [GeCl{o-C₆H₄(AsMe ₂)₂}][GeCI₃] shows pyramidal cations and anions both with crystallographic mirror symmetry, with the diarsine symmetrically chelating, and long Ge - Cl interactions give a loosely associated chain polymer with alternating cations and anions. Comparisons across this series of structurally diverse complexes are discussed.

Full text of DOI:10.1021/ic902068z

752 Inorg. Chem. 2010, 49, 752–760
DOI: 10.1021/ic902068z
Diphosphine and Diarsine Complexes of Germanium(II) Halides
;Preparation,
Spectroscopic, and Structural Studies
Fei Cheng, Andrew L. Hector, William Levason, Gillian Reid,* Michael Webster, and Wenjian Zhang
School of Chemistry, University of Southampton, Southampton, United Kingdom SO17 1BJ
Received October 20, 2009
The Ge(II) halide complexes [GeX2(L-L)] (L-L = o-C6H4(PPh2)2, o-C6H4(PMe2)2, Me2P(CH2)2PMe2; X = Cl, Br, I.
L-L = Et2P(CH2)2PEt2; X = Cl or Br. L-L = o-C6H4(AsMe2)2; X = Br or I) and [GeCl(L-L)][GeCl3] (L-L =
o-C6H4(AsMe2)2) have been prepared and characterized by IR, 1H and 31P{1H} NMR spectroscopy, and
microanalyses. The crystal structures of [GeX2{o-C6H4(PPh2)2}] (X = Cl, Br, I) reveal discrete mononuclear units
with a very asymmetric bidentate o-C6H4(PPh2)2 ligand and a bent GeX2 unit. Those of [GeX2{o-C6H4(PMe2)2}] show
symmetrically coordinated diphosphine with loosely associated dimer arrangements, formed through long Ge
X
3 3 3
bridges between adjacent monomer units. [GeX2{R2P(CH2)2PR2}] (R = Me; X = Cl, Br, I. R = Et; X = Cl, Br) all show
discrete monomer structures with 2-fold crystallographic symmetry and based upon four-coordinate Ge, with the
diphosphine chelating and approximately linear GeX2 units. [GeI2{o-C6H4(AsMe2)2}] involves significant intermole-
cular Ge I interactions, giving rise to a zigzag polymer chain. Finally, the structure of [GeCl{o-C6H4(AsMe2)2}]-
[GeCl3] shows pyramidal cations and anions both with crystallographic mirror symmetry, with the diarsine
3 3 3
symmetrically chelating, and long Ge Cl interactions give a loosely associated chain polymer with alternating
3 3 3
cations and anions. Comparisons across this series of structurally diverse complexes are discussed.
Introduction
The majority of germanium coordination complexes are
based upon the Ge(IV) oxidation state.3 We and others have
examined the chemistry of the tetrahalides with both hard N/
O- and soft P/S-donor ligands, including the first [GeF4-
(diphosphine)] and [GeF4(dithioether)] complexes.3-5 On
the other hand, the tetrahalides GeBr4 and GeCl4 do not form
complexes with thioether ligands, and they are reduced to
[R3PX][GeX3] by phosphines.5,6 However, two examples of
Ge(IV) arsine complexes have been structurally characterized,
trans-[GeCl4(AsR3)2] (R = Me or Et), although curiously no
adduct formation was observed with o-C6H4(AsMe2)2.5,6
Reports of the coordination chemistry of Ge(II) halides
The chemistry of germanium compounds is a very topical
area of research at present, with major activity in organo-
germanium chemistry and germanium coordination chemistry,
including for example the development of low-valent com-
pounds, such as, germylenes, multiply bonded species, radicals
and clusters, stabilization of germanium cations, and new
reagents for Ge-containing materials.1,2
*To whom correspondence should be addressed. E-mail: gr@soton.ac.uk.
(1) (a) Marygaryan, A. M. Photodetectors and Fiber Optics; Academic
Press: San Diego, CA, 2001; pp 369-458. (b) Shemkunas, M. P.; Petuskey, W. T.;
Chizmeshya, A. V. G.; Leinenweber, K.; Wolf, G. H. J. Mater. Res. 2004, 19,
1392–1399.
with neutral ligands are relatively few;structural data are
now available for several series of complexes with O- and
N-donor ligands and macrocycles, including neutral,7 mono-
cationic,8 and dicationic species8,9 in which the coordination
number at Ge(II) varies between three and eight, as well as
(2) For example, see: (a) Parr, J. In Comprehensive Coordination Chem-
istry II; McCleverty, J. A., Meyer, T. J., Eds.; Elsevier: Oxford, 2004; Vol 3,
pp 545-608. (b) Power, P. P. Organometallics 2007, 26, 4362–4372. (c) Power,
P. P. Appl. Organometal. Chem. 2005, 19, 488–493. (d) Spike, G. H.; Power,
P. P. Chem. Commun. 2007, 85–87. (e) Richards, A. F.; Brynda, M.; Olmstead,
M. M.; Power, P. P. Organometallics 2004, 23, 2841–2844. (f ) Richards, A. F.;
Hope, H.; Power, P. P. Angew. Chem., Int. Ed. 2003, 42, 4071–4074. (g) Dias,
H. V. R.; Wang, Z.; Jin, W. Coord. Chem. Rev. 1998, 176, 67–86. (h) Braunschweig,
H.;Hitchcock, P. B.; Lappert, M. F.;Pierssens, L. J. M.Angew. Chem., Int. Ed.1994,
33, 1156–1158. (i) Saur, I.; Garcia Alonso, S.; Barrau, J. Appl. Organometal. Chem.
2005, 19, 414–428. ( j) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Chem. Rev. 2009,
109, 3479–3511.
(4) Davis, M. F.; Levason, W.; Reid, G.; Webster, M.; Zhang, W. Dalton
Trans. 2008, 533–538.
(5) Davis, M. F.; Levason, W.; Reid, G.; Webster, M. Dalton Trans. 2008,
2261–2269.
(6) Godfrey, S. M.; Mushtaq, I; Pritchard, R. G. Dalton Trans. 1999,
1319–1323.
(3) (a) Willey, G. R.; Somasundaram, U.; Aris, D. R.; Errington, W.
Inorg. Chim. Acta 2001, 315, 191–195. (b) Adley, A. D.; Bird, P. H.; Fraser,
A. R.; Onyszchuk, M. Inorg. Chem. 1972, 11, 1402–1409. (c) Ejfler, J.; Szafert,
S.; Jiao, H.; Sobota, P. New J. Chem. 2002, 26, 803–805. (d) Cheng, F.; Davis,
M. F.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.; Zhang, W. Eur. J. Inorg.
Chem. 2007, 2488–2495. (e) Cheng, F.; Davis, M. F.; Hector, A. L.; Levason, W.;
Reid, G.; Webster, M.; Zhang, W. Eur. J. Inorg. Chem. 2007, 4897–4905.
(7) (a) Denk, M. K.; Khan, M.; Lough, A. J.; Shuchi, K. Acta Crystal-
logr., Sect. C 1998, 54, 1830–1832. (b) Leites, L. A.; Zabula, A. V.; Bukalov,
S. S.; Korlyukov, A. A.; Koroteev, P. S.; Maslennikova, O. S.; Egorov, M. P.;
Nefedov, O. M. J. Mol. Struct. 2005, 750, 116–122. (c) Tian, X.; Pape, T.; Mitzel,
N. W. Heteroatom Chem. 2005, 16, 361–363. (d) Cheng, F.; Dyke, J. M.;
Ferrante, F.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.; Zhang, W. Dalton
Trans. 2010, DOI: 10.1039/b911016j.
r
pubs.acs.org/IC
Published on Web 12/17/2009
2009 American Chemical Society

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 753
N-heterocyclic carbene complexes.8d,e In terms of soft phos-
phine and arsine ligands, only the structures of the very
distorted monomer, [GeCl2{Ph2P(CH2)2PPh2}],10 and two
pyramidal complexes, [GeX2(PPh3)] (X = Cl or I), have been
reported,7b,11 and there are early reports of the preparations
of GeI2 complexes with some tertiary and secondary phos-
phine ligands, including the diphosphine complexes, [GeI2-
{Ph2P(CH2)2PPh2}] and [(GeI2)2{Ph2P(CH2)2PPh2}],12a and
GeCl2 complexes with AsPh3 and AstBu3, albeit without
structural data.12b We reported a series of Ge(II) complexes
with (soft) macrocyclic thioethers, which show extended
chain and network structures based upon distorted six-
coordinate geometries at germanium through Ge-X (X =
Cl or Br) and long Ge-S bonds to S atoms of bridging
(exodentate) thiacrowns.13
Table 1. 31P{1H} NMR Spectroscopic Dataa
complex
δ31P{1H}/ppm
Δ/ppmb
[GeCl2{o-C6H4(PPh2)2}]
[GeBr2{o-C6H4(PPh2)2}]
[GeI2{o-C6H4(PPh2)2}]
þ4.5 (183 K: þ3.2)
-4.8 c
þ17.5
þ8.7
-10.5 (183 K: -7.2)
þ21.6 (193 K: þ22.4)
þ13.2 (193 K: þ14.4)
þ0.4 (183 K: þ2.5)
þ17.4 (193 K: þ20.5)
þ11.8 (193 K: þ13.0)
þ0.7 (183 K: þ1.5)
þ35.7 (183 K: þ37.2)
þ29.4 (193 K: þ29.3)
þ2.5
[GeCl2{o-C6H4(PMe2)2}]
[GeBr2{o-C6H4(PMe2)2}]
[GeI2{o-C6H4(PMe2)2}]
[GeCl2{Me2P(CH2)2PMe2}]
[GeBr2{Me2P(CH2)2PMe2}]
[GeI2{Me2P(CH2)2PMe2}]
[GeCl2{Et2P(CH2)2PEt2}]
[GeBr2{Et2P(CH2)2PEt2}]
þ76.6
þ68.3
þ55.5
þ65.4
þ59.8
þ48.7
þ55.0
þ48.7
a Spectra recorded in a CH2Cl2 solution at 298 K. b Δ = δ(complex) -
δ(ligand) at 298 K. c Significantly broadened but unshifted at 223 K; no
resonance observed at 183 K.
We describe here a systematic study of the synthesis and
structural properties of Ge(II) halide (chloride, bromide, and
iodide) complexes with neutral diphosphine and diarsine
ligands, all of which can form five-membered chelate rings
but have quite different steric and electronic properties. In
comparison to complexes of the transition metal ions, within
the p block it is much less well understood how small
variations in ligand architecture, steric requirements, and
donor properties influence their coordination complexes. For
example, acceptors such as GaX3 and InX3 (X = Cl, Br, or I)
form a diverse range of structure types with closely related
diphosphine and diarsine ligands such as o-C6H4(ER2)2 (E =
P or As; R = Me; E = P; R = Ph) and R2P(CH2)2PR2 (R =
Me or Et).14
(CH2)2PMe2, Et2P(CH2)2PEt2, or o-C6H4(AsMe2)2. X = I;
L-L = C6H4(PPh2)2, o-C6H4(PMe2)2, Me2P(CH2)2PMe2,
or o-C6H4(AsMe2)2) were also isolated as white or light-
yellow solids in good yield by the direct reaction of GeBr2 or
GeI2 with the ligand in anhydrous MeCN. On the other
hand, Ph2As(CH2)2AsPh2 does not displace dioxane from
[GeCl2(dioxane)] in anhydrous CH2Cl2, consistent with the
much weaker σ-donor properties of the Ph-substituted dia-
rsine, although we note that the corresponding diphosphine
gives [GeCl2{Ph2P(CH2)2PPh2}].10 The complexes [GeX2{o-
C6H4(PPh2)2}] (X = Cl, Br, I) and [GeCl2{Et2P(CH2)2PEt2}]
(X = Cl, Br) arereadily soluble innon-donor solvents such as
CH2Cl2, whereas [GeX2{Me2P(CH2)2PMe2}] (X = Cl, Br, I)
are only moderately soluble, and for [GeX2{o-C6H4-
(PMe2)2}] (X = Cl, Br, I), [GeX2{o-C6H4(AsMe2)2}] (X =
Br, I), and [GeCl{o-C6H4(AsMe2)2}][GeCl3], the solubility in
CH2Cl2 is poor.
Results and Discussion
The reaction of [GeCl2(dioxane)] with 1 mol equiv of the
neutral P- or As-donor ligand L-L (L-L = o-C6H4(PPh2)2,
o-C6H4(PMe2)2, Me2P(CH2)2PMe2, or Et2P(CH2)2PEt2) in
an anhydrous CH2Cl2 solution resulted in the formation of
the neutral [GeCl2(L-L)] as moisture-sensitive white solids
in good yield. The reaction of [GeCl2(dioxane)] with
o-C6H4(AsMe2)2 in a 2:1 ratio gives the ionic [GeCl{o-C6H4-
(AsMe2)2}][GeCl3] in high yield, and this is also the product
isolated from a 1:1 molar ratio (contrast reaction of GeBr2 or
GeI2 with o-C6H4(AsMe2)2, which gives the neutral [GeX2(o-
C6H4(AsMe2)2)], below).
1
The H NMR spectra of these new complexes (CD2Cl2)
are simple, with resonances to high frequency of uncom-
plexed L-L, and consistent with symmetrical coordination
of the diphosphine or diarsine. Variable-temperature 31P-
{1H} NMR spectroscopic measurements on the diphos-
phine complexes (Table 1) show a singlet resonance to high
frequency of the ligand itself, and in all cases this is
essentially unchanged on cooling to below 200 K. All of
the ligands investigated involve a C2-linking group between
the P atoms and, hence, if bidentate in solution, would give
rise to a five-membered chelate ring. The magnitude of the
coordination shifts, Δ, (Table 1) varies considerably with
the nature of the phosphine, with the largest Δ values
observed for the stronger σ-donor phosphines with terminal
alkyl substituents. This suggests that, for L-L = o-C6H4-
(PMe2)2, Me2P(CH2)2PMe2, and Et2P(CH2)2PEt2, the solu-
tion structures of [GeX2(L-L)] involve chelating L-L,
whereas for L-L = o-C6H4(PPh2)2, the ligand is probably
monodentate in solution and undergoing rapid exchange of
the “free” and coordinated P atoms even at 200 K (the
31P{1H} NMR spectrum of the reported [GeCl2-
{Ph2P(CH2)2PPh2}], which involves very asymmetric
diphosphine coordination in the solid state is also a single
resonance, attributed to fast equilibration of the P atoms in
solution).10 Large, positive shifts are frequently (although
not always) observed for diphosphine complexes contain-
ing five-membered chelate rings.15 Consistent with this
(although not definitive evidence), variable-temperature
The Ge(II) bromo and iodo complexes, [GeX2(L-L)]
(X = Br; L-L = o-C6H4(PPh2)2, o-C6H4(PMe2)2, Me2P-
(8) (a) Rupar, P. A.; Staroverov, V. N.; Ragogna, P. J.; Baines, K. M.
J. Am. Chem. Soc. 2007, 129, 15138–15139. (b) Reger, D. L.; Coan, P. S. Inorg.
Chem. 1996, 35, 258–260. (c) Rupar, P. A.; Bandyopadhyay, R.; Cooper, B. F. T.;
Stinchcombe, M. R.; Ragogna, P. J.; Macdonald, C. L. B.; Baines, K. M. Angew.
Chem., Int. Ed. 2009, 48, 5155–5158. (d) Rupar, P. A.; Jennings, M. C.; Baines,
K. M. Organometallics 2008, 27, 5043–5051. (e) Arduengo, A. J., III; Dim,
H. V. R.; Calabrese, J. C; Davidson, F. Inorg. Chem. 1993, 32, 1541–1542.
(9) (a) Rupar, P. A.; Staroverov, V. N.; Baines, K. M. Science 2008, 322,
1360–1363. (b) Cheng, F.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.;
Zhang, W. Angew. Chem., Int. Ed. 2009, 48, 5152–5154.
(10) Bruncks, N.; Du Mont, W. W.; Pickardt, J.; Rudolph, G. Chem. Ber.
1981, 114, 3572–3580.
(11) Inoguchi, Y.; Okui, S.; Mochida, K.; Itai, A. Bull. Chem. Soc. Jpn.
1985, 974–977.
(12) (a) King, R. B. Inorg. Chem. 1963, 2, 199–200. (b) du Mont, W.-W.;
Rudolph, G. Z. Naturforsch., B 1981, 36, 1215–1218.
(13) Cheng, F.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.;
Zhang, W. Chem. Commun. 2008, 5508–5510.
(14) (a) Cheng, F.; Davis, M. F.; Hector, A. L.; Levason, W.; Reid, G.;
Webster, M.; Zhang, W. Inorg. Chem. 2007, 46, 7215–7223. (b) Cheng, F.;
Friend, S. I.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.; Zhang, W. Inorg.
Chem. 2008, 47, 9691–9700.
(15) Garrou, P. Chem. Rev. 1981, 81, 229–266.

754 Inorganic Chemistry, Vol. 49, No. 2, 2010
Cheng et al.
˚
Table 2. Selected Bond Lengths [A] and angles [deg] for [GeX2{o-C6H4(PPh2)2}]
(X = Cl, Br, I)
compound
X = Cl
X = Br
X = I
Ge1-P1
2.5153(13)
3.1958(15)
2.2753(15)
2.3195(16)
66.58(4)
89.47(5)
90.12(5)
95.82(5)
83.49(5)
156.67(5)
2.5259(13)
3.1167(14)
2.4635(7)
2.5057(8)
67.15(3)
89.09(3)
92.92(3)
97.36(3)
85.45(3)
159.89(3)
2.511(2)
3.068(2)
2.6733(11)
2.7663(11)
68.40(6)
90.03(6)
93.74(6)
97.55(3)
85.61(5)
161.93(5)
Ge1-P2
Ge1-X1
Ge1-X2
P1-Ge1-P2
X1-Ge1-P1
X2-Ge1-P1
X1-Ge1-X2
X1-Ge1-P2
X2-Ge1-P2
The complexes [GeX2{o-C6H4(PPh2)2}] (X = Cl, Br,
or I) adopt very similar structures (although only for X =
Br and I are they isomorphous), based upon discrete
mononuclear units (Figures 1 and 2, Table 2) with two
halide ligands and a very asymmetric bidentate o-C6H4-
(PPh2)2 ligand, with the Ge-P distance differing by ca.
Figure 1. View of the structure of the [GeCl2{o-C6H4(PPh2)2}] mono-
mer with the atom numbering scheme adopted. Phenyl rings are num-
bered cyclically starting at the ipso C atom. Ellipsoids are drawn at the
30% probability level, and H atoms are omitted for clarity.
˚
0.6 A. Alternatively, the structure may be described as a
pyramidal PX2 coordination environment at Ge(II), with
the diphosphine effectively monodentate, with the second
P-donor atom interacting weakly, giving [3 þ 1] coordi-
nation. [In this work, we use the notation [X þ Y]
coordination to differentiate between short and long
contacts; for example, [3 þ 1] means three short and
one long Ge-L bond.] The P-Ge P chelate angles are
3 3 3
very acute, 66.58(4)° (Cl), 67.15(3)° (Br), and 68.40(6)°
(I), with the GeX2 unit bent, 95.82(5)° (Cl), 97.36(3)° (Br),
and 97.55(3)° (I). The P P distance in [GeX2{o-C6H4-
3 3 3
˚
(PPh2)2}] does not vary significantly with X (ca. 3.18 A),
and two of the Ph rings (one on each P) are nearly parallel
(angles between the C6 planes = 15.4(1) (X = Cl), 4.8(2)
(X = Br), and 3.2(4)° (X = I)). The distances between the
C atoms of one ring and the best plane through the other
C6 ring also vary with X (3.42-4.22 (X = Cl), 3.21-3.48
Figure 2. View of the structure of the [GeBr2{o-C6H4(PPh2)2}] mono-
mer with the atom numbering scheme adopted. Phenyl rings are num-
bered cyclically starting at the ipso C atom. Ellipsoids are drawn at the
50% probability level, and H atoms are omitted for clarity. The same
atom numbering scheme applies for [GeI2{o-C6H4(PPh2)2}].
˚
(X = Br),; 3.21-3.39 A (X = I)).
Many complexes involving the o-phenylene diphos-
phine, o-C6H4(PPh2)2, have been described and invari-
ably involve essentially symmetric chelation. Therefore,
the very asymmetric chelation (or pseudo-monodentate
coordination) as in the Ge(II) complexes in this work is
extremely unusual.
[GeCl2{o-C6H4(PMe2)2}], which incorporates the less
sterically demanding and much stronger σ-donor diphos-
phine, shows (Figure 3, Table 3) a loosely associated
dimer, having 2-fold crystallographic symmetry, formed
31P{1H} NMR spectra of [GeBr2{o-C6H4(PPh2)2}] with
added o-C6H4(PPh2)2 show a broad singlet resonance
even at 200 K, consistent with rapid ligand exchange. In
contrast, those of [GeCl2{o-C6H4(PMe2)2}] and [GeCl2-
{Et2P(CH2)2PEt2}] with added ligand show broad, aver-
aged resonances at 298 K, which separate on cooling
(by 243 K) into two sharp singlets with chemical shifts
identical to those of the individual [GeCl2(L-L)] and “free”
L-L. These proposed solution structures are also consistent
with the structures observed in the solid state (X-ray
crystallography), below.
X-Ray Crystallographic Studies. In view of the paucity
of structural data available for Ge(II) halide complexes
with phosphines (vide supra) and the absence of any
structurally characterized Ge(II) arsine complexes in the
literature, we have undertaken crystal structure determi-
nations on a series of the new complexes reported herein,
including examples with each ligand type. These are
described below and followed by a comparison of the
structures observed: the effect of halide type, P versus As
donor ligands, aryl versus alkyl substituents, and satu-
rated versus aromatic interdonor linkages.
through long Ge Cl bridges between adjacent mono-
3 3 3
mer units. Notably, the Ge atom is coordinated to an
approximately symmetrically chelating diphosphine
˚
(P-Ge-P = 80.01(4)°), one terminal Cl2 (2.704(1) A),
and two asymmetrically bridging Cl atoms (Ge1-Cl1 =
˚
2.494(1), Ge1 Cl1a = 3.481(1) A, where a = 1 - x, y,
3 3 3
3/2 - z). The Ge1 Ge1a distance across the Ge2Cl2 unit
is 3.64 A, considerably shorter than twice the van der
3 3 3
˚
Waals radius for Ge (4.0 A),16 and the Ge2Cl2 unit is not
˚
planar (the angle between the two GeCl2 planes is
104.04(3)°). The bromo analog, [GeBr2{o-C6H4(PMe2)2}]
(16) See the Web site www.ccdc.cam.ac.uk/products/csd/radii/ for values
ꢀ
used by the CCDC and literature references: Cordero, B.; Gomez, V.;
ꢀ
ꢀ
Platero-Prats, A. E.; Reves, M.; Echeverria, J.; Cremades, E.; Barragan,
F.; Alvarez, S. Dalton Trans. 2008, 2832-2838.

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 755
Figure 4. Viewofthe structure of[GeI2{o-C6H4(PMe2)2}] with the atom
numbering scheme adopted and showing the long Ge I contacts
between the adjacent monomer units. Ellipsoids are drawn at the 50%
probability level, and H atoms are omitted for clarity. Symmetry opera-
tion: a = 1 - x, -y, 1 - z.
Figure 3. View of the structure of the weakly associated [GeCl2{o-
C6H4(PMe2)2}]2 dimer with the atom numbering scheme adopted. Ellip-
soids are drawn at the 50% probability level, and H atoms are omitted for
clarity. Symmetry operation: a = -x, y, 1/2 - z.
3 3 3
˚
Table 3. Selected Bond Lengths [A] and Angles [deg] for [GeX2{o-C6H4(PMe2)2}]
(X = Cl, Br, I)
compound
X = Cl
X = Br
X = I
Ge1-P1
2.4709(11)
2.4390(11)
2.4942(11)
2.7040(11)
80.01(4)
164.35(4)
88.99(4)
79.86(4)
2.4805(9)
2.4498(10)
2.6521(6)
2.8529(6)
80.19(3)
166.513(17)
89.58(3)
80.69(3)
2.481(2)
2.456(2)
2.8211(12)
3.0749(12)
79.79(7)
172.31(4)
89.44(6)
83.28(6)
94.71(6)
81.57(6)
Ge1-P2
Ge1-X1
Ge1-X2
P1-Ge1-P2
X1-Ge1-X2
P1-Ge1-X1
P1-Ge1-X2
P2-Ge1-X1
P2-Ge1-X2
87.66(4)
79.66(4)
88.83(3)
80.37(3)
(Table 3), is isomorphous with the chloride complex, with
˚
Ge1 Br1a = 3.539(1) and Ge1 Ge1a = 3.818(1) A.
3 3 3
3 3 3
The iodo complex [GeI2{o-C6H4(PMe2)2}] shows (Figure 4,
Table 3) a similar monomer unit with the o-C6H4(PMe2)2
chelating and the GeI2 unit essentially linear (172.31(4)°);
however, while the adjacent monomers align to give a
precisely planar rhombic Ge2I2 arrangement, the inter-
Figure 5. View of the structure of [GeBr2{Me2P(CH2)2PMe2}] with the
atom numbering scheme adopted. Ellipsoids are drawn at the 50%
probability level, and H atoms are omitted for clarity. The atom number-
ing scheme used is the same for [GeCl2{Me2P(CH2)2PMe2}]. Symmetry
operation: a = -x, y, 1/2 - z.
˚
molecular Ge1 I1a distance is 3.92 A, just within the
3 3 3
16
˚
sum of the van der Waals radii (3.98 A).
˚
Table 4. Selected Bond Lengths [A] and Angles [deg] for [GeX2{Me2P(CH2)2-
PMe2}] (X = Cl, Br)
The crystals of [GeX2{Me2P(CH2)2PMe2}] (X = Cl or
Br) are isomorphous and show (Figure 5, Table 4) a
discrete monomer structure with 2-fold crystallographic
symmetry and based upon four-coordinate Ge, with the
diphosphine chelating (P-Ge-P ca. 80°), and approxi-
mately linear GeX2 units (168.79(3)° (Cl), 171.81(2)° (Br),
174.57(3)° (I)).
While not isomorphous with the chloro and bromo
analogs, the structure of [GeI2{Me2P(CH2)2PMe2}]
shows a similar coordination environment at Ge. Closer
inspection of the packing in the unit cell reveals the very
weakly associated centrosymmetric dimer shown in Figure 6
(Table 5), similar to that in [GeI2{o-C6H4(PMe2)2}] above;
compound
X = Cl
X = Br
Ge1-P1
2.4495(6)
2.5858(7)
81.63(3)
83.69(2)
87.83(2)
168.79(3)
2.4628(7)
2.7335(5)
81.56(3)
89.091(19)
84.702(19)
171.806(16)
Ge1-X1
P1-Ge1-P1aa
P1-Ge1-X1
P1-Ge1-X1aa
X1-Ge1-X1aa
a Symmetry operation: a = -x, y, 1/2 - z.
The crystal structure of [GeI2{o-C6H4(AsMe2)2}]
(Figure 8a and b, Table 7) shows that the monomer
unit has a similar arrangement as in [GeI2{o-C6H4-
(PMe2)2}] above, with I1-Ge1-I2 = 165.88(3)° and
As1-Ge1-As2 = 79.75(3)°, although closer inspection
of the crystal packing reveals significant intermolecular
˚
while the Ge1 I1a distance (3.851(1) A) is at the upper
limit for an interaction (sum of the van der Waals radii of Ge
3 3 3
and I = 3.98 A),16 the directionality of the rhombic Ge2I2
˚
core does suggest that this is a genuine, albeit weak, inter-
molecular interaction.
˚
˚
Ge1 I1b (3.476(1) A) and Ge1 I2a (3.352(1) A)
3 3 3
3 3 3
The compounds [GeX2{Et2P(CH2)2PEt2}] (X = Cl or
Br) are isomorphous, and their molecular structures
(Figure 7, Table 6) are based upon discrete monomer
units with 2-fold crystallographic symmetry, which are
very similar to those of their methyl analogues,
[GeX2{Me2P(CH2)2PMe2}] (X = Cl or Br) above, again
with the diphosphine approximately symmetrically che-
lating and with nearly linear GeX2 units.
interactions, giving rise to a zigzag polymer chain,
as illustrated in Figure 8b, and a highly distorted [As2I2
þ I2] donor set at each Ge atom. A similar polymeric
chain structure is present in [GeCl2(2,20-bipy)]n and
[GeBr2(1,10-phen)]n.7d
The structure of [GeCl{o-C6H4(AsMe2)2}][GeCl3]
shows (Figure 9a, Table 8) pyramidal cations and anions,
both with crystallographic mirror symmetry, and with the

756 Inorganic Chemistry, Vol. 49, No. 2, 2010
Cheng et al.
Figure 6. View of the structure of the very weakly associated
[GeI2{Me2P(CH2)2PMe2}]2 dimer with the atom numbering scheme
adopted. Ellipsoids are drawn at the 50% probability level, and H atoms
are omitted for clarity. Symmetry operation: a = 1 - x, 2 - y, -z.
˚
Table 5. Selected Bond Lengths [A] and Angles [deg] for [GeI2{Me2P(CH2)2-
PMe2}]
Ge1-P1
2.463(2)
2.8685(12)
80.95(7)
87.63(6)
88.19(6)
Ge1-P2
2.514(2)
3.0787(13)
91.40(6)
84.52(5)
174.57(3)
Ge1-I1
Ge1-I2
P1-Ge1-P2
P2-Ge1-I1
P2-Ge1-I2
P1-Ge1-I1
P1-Ge1-I2
I1-Ge1-I2
Figure 8. (a) View of the structure of [GeI2{o-C6H4(AsMe2)2}] showing
the numbering scheme adopted. Ellipsoids are drawn at the 50% prob-
ability level, and H atoms are omitted for clarity. (b) View of the chain
structure of [GeI2{o-C6H4(AsMe2)2}]n formed through long Ge
contacts. Turquoise = Ge; pink = I; teal = As; gray = C.
I
3 3 3
˚
Table 7. Selected Bond Lengths [A] and Angles [deg] for [GeI2{o-C6H4(AsMe2)2}]
Ge1-I1
2.8763(10)
2.6210(11)
79.75(3)
89.85(3)
80.14(3)
Ge1-I2
3.0888(10)
2.6313(11)
87.32(3)
81.15(3)
165.88(3)
Ge1-As1
Ge1-As2
As1-Ge1-As2
As2-Ge1-I1
As2-Ge1-I2
As1-Ge1-I1
As1-Ge1-I2
I1-Ge1-I2
coordination at Ge1 (Figure 9b). These are the first
reported examples of arsine complexes of germanium(II).
Structural Comparisons. Structural data are presented
here for several series of Ge(II) halide complexes with
diphosphine and diarsine ligands, allowing quite detailed
comparisons to be made. In terms of coordination num-
ber and environments present in [GeX2(L-L)], we find
[3 þ 1] coordination (PX2 þ P) for L-L = o-C6H4(PPh2)2
irrespective of X (likely due to the steric requirements
of the Ph rings); essentially [4] coordination (P2X2) for
L-L = R2P(CH2)2PR2 (R = Me or Et) irrespective of
X and for [GeI2{o-C6H4(PMe2)2}]; and [4 þ 2] coordina-
tion (P2X2 þ X2) for [GeX2{o-C6H4(PMe2)2}] (X = Cl,
Br), which form weak halide-bridged dimers, and for
[GeI2{o-C6H4(AsMe2)2}], which forms a zigzag chain
structure. For a given diphosphine, the Ge-P bond
distances are essentially independent of the halide, indi-
cating very similar Lewis acidities for the GeX2 frag-
ments. In the discrete monomer structures, [GeX2{o-
C6H4(PPh2)2}], we observe a bent X-Ge-X unit result-
ing from the pyramidal GeX2P core, whereas in the four-
coordinate [GeX2{R2P(CH2)2PR2}], the X-Ge-X are
approximately linear.
Figure 7. View of the structure of [GeCl2{Et2P(CH2)2PEt2}] with the
atom numbering scheme adopted. Ellipsoids are drawn at the 50%
probability level, and H atoms are omitted for clarity. Symmetry opera-
tion: a = -x, y, 1/2 - z. The atom numbering scheme used is the same for
[GeBr2{Et2P(CH2)2PEt2}].
˚
Table 6. Selected Bond Lengths [A] and Angles [deg] for [GeX2{Et2P(CH2)2-
PEt2}] (X = Cl, Br)
compound
X = Cl
X = Br
Ge1-P1
2.4672(5)
2.5803(5)
81.55(2)
87.100(15)
81.768(15)
165.30(2)
2.4694(5)
2.7340(4)
81.60(3)
88.107(15)
83.276(15)
168.619(14)
Ge1-X1
P1-Ge1-P1aa
P1-Ge1-X1
P1-Ge1-X1aa
X1-Ge1-X1aa
a Symmetry operation: a = -x, y, 1/2 - z.
diarsine symmetrically chelating (cation, Ge1-Cl1 = 2.373-
˚
(1) A, Ge1-As1 = 2.5847(5), As1-Ge1-As1a = 80.75-
˚
(2)°; anion, Ge-Cl = 2.311(2), 2.294(1) A). Atoms Cl3 and
Cl3b also exhibit weak interactions with Ge1 (3.44 A),
˚
giving a loosely associated chain polymer with alternating
cations and anions, and leading to an overall [As2Cl þ Cl2]

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 757
shows that the difference is essentially as expected on the
basis of the donor covalent radii.16
The only other structurally characterized germanium
arsine complexes are trans-[GeCl4(AsR3)2] (R = Me or
Et),5,6 for which Ge-As = 2.472(1) (Me) and 2.4904(9) A
˚
˚
(Et) and Ge-Cl = 2.307(4) and 2.341(4) A (Me) and
˚
2.330(2) and 2.323(1) A (Et). Thus, both Ge-As and
Ge-Cl are slightly longer in the Ge(II) species. Similarly,
while we cannot compare GeCl4 phosphine complexes
with the Ge(II) systems here, since none have been
structurally characterized (due to their rapid decomposi-
tion into Ge(II) and chlorophosphonium(V) salts),6
structural data are available for [GeF4{o-C6H4(PMe2)2}]
˚
(Ge-P = 2.427(1) A), which compares with the range
˚
2.4390(11)-2.481(2) A in the [GeX2{o-C6H4(PMe2)2}].
Conclusions
This work presents the first extended series of Ge(II) halide
complexes involving neutral diphosphine and diarsine li-
gands. The structural studies have identified the range of
motifs present which appear to be subtly dependent upon the
ligand donor type and steric and electronic properties,
although mostly independent of the halide present. The
diversity of the structures and coordination numbers
observed within this quite closely related series of diphos-
phine and diarsine ligands suggests that the germanium
center does not have a strong stereochemical preference;
hence, small differences in steric and electronic properties
and possibly crystal packing may play a significant role in
determining the geometries adopted. We have not found
evidence for more than one structure type for a specific L-L
and X. In view of the larger energy gap between the s and p
orbitals in germanium compared to silicon and carbon,17 the
observed structures can be rationalized using germanium 4p
orbitals and a three-center-four-electron bonding model,
leaving the Ge-based “lone pair” occupying the stabilized 4s
orbital.
Figure 9. (a) View of the structure of the cation in [GeCl{o-C6H4-
(AsMe2)2}][GeCl3] with the atom numbering scheme adopted. Ellipsoids
are drawn at the 50% probability level, and H atoms are omitted for
clarity. The cation (and the anion) has crystallographic mirror symmetry.
Symmetry operation: a = x, 1/2 - y, z. (b) View of the chain structure
showing alternating, weakly associated [GeCl{o-C6H4(AsMe2)2}]þ ca-
tions and [GeCl3]- anions. Turquoise = Ge; green = Cl; teal = As;
gray = C.
˚
Table 8. Selected Bond Lengths [A] and Angles [deg] for [GeCl{o-C6H4-
(AsMe2)2}][GeCl3]
Ge1-As1
2.5847(5)
2.3734(13)
80.75(2)
Ge2-Cl2
2.3108(15)
2.2941(10)
95.46(5)
Ge1-Cl1
Ge2-Cl3
As1-Ge1-As1aa
Cl1-Ge1-As1
Cl3-Ge2-Cl3ba
Cl3-Ge2-Cl2
88.21(3)
94.73(4)
a Symmetry operations: a = x, 1/2 - y, z; b = x, 3/2 - y, z.
The series [GeX2{o-C6H4(PPh2)2}] (X = Cl, Br, I)
adopts a very similar structure to that of [GeCl2-
{Ph2P(CH2)2PPh2}],10 involving the much more flexible
Ph2P(CH2)2PPh2 ligand, which shows Ge-Cl=2.236(2)
˚
and 2.332(2) A, although the shorter of the two Ge-P
˚
distances in that complex (2.314(2) A) is ca. 0.2 A shor-
˚
Experimental Section
˚
ter than those in [GeX2{o-C6H4(PPh2)2}] (ca. 2.52 A),
[GeCl2(1,4-dioxane)] was prepared by the literature meth-
od,18 and GeBr2 and GeI2 were obtained from Aldrich and
used as received. The ligands Me2P(CH2)2PMe2 and
Et2P(CH2)2PEt2 were obtained from Aldrich, while o-C6-
H4(PPh2)2, o-C6H4(PMe2)2, o-C6H4(AsMe2)2, and Ph2As-
(CH2)2AsPh2 were made according to literature methods
and stored under N2 in a glovebox.19-21 All reactions were
conducted using Schlenk, vacuum line, and glovebox techni-
ques and under a dry dinitrogen atmosphere. IR spectra were
recorded from Nujol mulls on a Perkin-Elmer Spectrum 100
spectrometer and Raman spectra using a Perkin-Elmer FT
Raman 2000R with a Nd:YAG laser. The bands below
360 cm-1 in each complex are listed below. 1H NMR spectra
were recorded from solutions in CDCl3 or CD2Cl2 solutions
on a Bruker AV300 and 31P{1H} NMR spectra on a Bruker
DPX400 and referenced to 85% H3PO4. Microanalytical
results were from Medac Ltd.
˚
while the long Ge P distance (3.340(2) A) is ca. 0.2 A
˚
3 3 3
longer, possibly a consequence of the difference in flexibility
of the ligand backbones. The Ge-P distances also compare
well with those for [GeX2(PPh3)] (X = Cl, 2.51 A; X = I,
˚
˚
2.503(4), 2.510(5) A for the two independent molecules).
The Ge-P distances show a greater dependence
upon the nature of the terminal substituent. Most not-
ably, comparing the series [GeX2{o-C6H4(PPh2)2] with
[GeX2{o-C6H4(PMe2)2}], we find a decrease in Ge-P in
˚
the latter by ca. 0.05 A (despite the increased coordination
number which, in the absence of other factors, would
usually lead to lengthening of the bond). This is consistent
with the increased σ-donor ability of the Me-substituted
phosphine. The same pattern is observed in the structures
of [GeX2{R2P(CH2)2PR2}], which also contain alkyl-
substituted (strong σ-donor) phosphines.
Uniquely for the GeCl2/o-C6H4(AsMe2)2 system, only
the ionic [GeCl{o-C6H4(AsMe2)2}][GeCl3] was obtained,
although it may simply be the least soluble species in the
(labile) reaction system.
(17) See: Nagendran, S.; Roesky, H. W. Organometallics 2008, 27,
457-492 and references therein.
(18) Denk, M. K.; Herrman, W. A. German Patent DE 4214281 A1, 1993.
(19) McFarlane, H. C. E.; McFarlane, W. Polyhedron 1983, 2, 303–304.
(20) Kyba, E. P.; Liu, S. T.; Harris, R. L. Organometallics 1983, 2,
1877–1879.
A comparison of the Ge-P versus Ge-As distances in
the direct analogs [GeI2{o-C6H4(EMe2)2}] (E = P or As)
(21) Feltham, R. D.; Nyholm, R. S.; Kasenally, A. J. Organomet. Chem.
1967, 7, 285–288.

758 Inorganic Chemistry, Vol. 49, No. 2, 2010
Cheng et al.
[GeCl2{o-C6H4(PPh2)2}]. 1,2-Bis(diphenylphosphino)benzene
(0.223 g, 0.50 mmol) was added to a solution of [GeCl2(1,4-
dioxane)] (0.115 g, 0.50 mmol) in CH2Cl2 (15 mL) at room
temperature with stirring, giving a clear solution. After 30 min,
the solvent was removed in vacuo to leave a white solid which was
washed with diethyl ether and dried in vacuo. Colorless crystals
were obtained by slow evaporation of the solvent from the
dichloromethane solution. Yield: 0.28 g, 95%. Anal. Calcd for
C30H24Cl2GeP2: C, 61.1; H, 4.1. Found: C, 60.7; H, 4.0. 1H NMR
(CD2Cl2, 298 K): δ 7.28-7.55 (m). 31P{1H} NMR (CD2Cl2, 298
K): δ 4.5 (s). IR (Nujol, cm-1): 317(s), 269(s, br), 240(sh). Raman
(cm-1): 318(s), 262(s), 217(s).
(m, [12H], Me). 31P{1H} NMR (CD2Cl2, 298 K): δ 35.7 (br s).
IR (Nujol, cm-1): 282(w), 233(m), 229(m).
[GeBr2{Et2P(CH2)2PEt2}]. The same method as for [GeBr2-
{o-C6H4(PPh2)2}] above is used, but using Et2P(CH2)2PEt2,
yielding a white solid. Yield: 0.20 g, 93%. Colorless crystals
were obtained by slow evaporation of the solvent from an
acetonitrile solution. Anal. Calcd for C10H24Br2GeP2: C, 27.4;
H, 5.5. Found: C, 27.5; H, 5.5. 1H NMR (CD2Cl2, 298 K): δ 2.23
(m, [8H], CH2), 1.15 (m, [12H] Me). 31P{1H} NMR (CD2Cl2,
298 K): δ 29.4 (s). IR (Nujol, cm-1): 278(w), 226(w).
[GeCl2{Me2P(CH2)2PMe2}]. The same method as for
[GeCl2{o-C6H4(PPh2)2}] above is used, but using Me2P-
(CH2)2PMe2, yielding a white solid. Yield: 0.13 g, 90%. Color-
less crystals were obtained by slow evaporation of the solvent
from a dichloromethane solution. Anal. Calcd for C6H16-
[GeBr2{o-C6H4(PPh2)2}]. 1,2-Bis(diphenylphosphino)benzene
(0.223 g, 0.50 mmol) was added to a solution of GeBr2 (0.115 g,
0.50 mmol) in CH3CN (15 mL) at room temperature with stirring,
which gave a clear solution. After 30 min, the solvent was removed
in vacuo to leave a white solid, which was washed with diethyl ether
and dried in vacuo. Colorless crystals were obtained by slow
evaporation of the solvent from an acetonitrile solution. Yield:
0.30 g, 88%. Anal. Calcd for C30H24Br2GeP2: C, 53.1; H, 3.6.
Found: C, 52.9; H, 3.8. 1H NMR (CD2Cl2, 298 K): δ 7.20-7.55
(m). 31P{1H} NMR (CD2Cl2, 298 K): δ -4.8. IR (Nujol, cm-1):
327(m), 289(w), 257(w).
Cl2GeP2 1/2CH2Cl2: C, 23.2; H, 5.2. Found: C, 23.1; H, 5.0.
3
1H NMR (CD2Cl2, 298 K): δ 2.26 (d, [4H] 2JP,H = 12 Hz, CH2),
1.72 (d, [12H] 2JP,H =12Hz, Me). 31P{1H} NMR (CD2Cl2, 298K):
δ 17.4 (s). IR (Nujol, cm-1): 350(m), 327(w), 309(m), 265(br m).
[GeBr2{Me2P(CH2)2PMe2}]. The same method as for
[GeBr2{o-C6H4(PPh2)2}] above is used, but using Me2P-
(CH2)2PMe2, yielding a white solid. Yield: 0.16 g, 88%. Color-
less crystals were obtained by slow evaporation of the solvent
from an acetonitrile solution. Attempts to obtain satisfactory
microanalytical data on different samples consistently gave %C
and %H values lower than expected, possibly due to some
ligand loss during drying of the samples in vacuo. However,
the spectroscopic and crystallographic data provide unambig-
uous evidence for the existence of this compound and strongly
suggest only one phosphine-containing species is produced. 1H
[GeI2{o-C6H4(PPh)2}]. The same method as for [GeBr2{o-
C6H4(PPh2)2}] above is used, yielding a pale yellow solid. Yield:
0.35 g, 91%. Pale yellow crystals were obtained by slow eva-
poration of the solvent from a dichloromethane solution. Anal.
Calcd for C30H24GeI2P2: C, 46.5; H, 3.1. Found: C, 46.7; H, 3.1.
1H NMR (CD2Cl2, 298 K): δ 7.15-7.55 (m). 31P{1H} NMR
(CD2Cl2, 298 K): δ -10.5.
[GeCl2{o-C6H4(PMe2)2}]. The same method as for [GeCl2-
{o-C6H4(PPh2)2}] above is used, but using o-C6H4(PMe2)2,
yielding a white solid. Yield: 0.14 g, 85%. Colorless crystals
were obtained by slow evaporation of the solvent from
an acetonitrile solution. Anal. Calcd for C10H16Cl2GeP2: C,
35.4; H, 4.2. Found: C, 35.0; H, 4.6. 1H NMR (CD2Cl2, 298 K):
δ 7.76 (m, [4H], o-C6H4), 2.02 (d, [12H] J = 12 Hz, Me). 31P{1H}
NMR (CD2Cl2, 298 K): δ 21.6 (s). IR (Nujol, cm-1):
341(m), 302(s), 281(w), 225(m). Raman (cm-1): 342(s), 250(s),
217(s).
2
NMR (CD2Cl2, 298 K): δ 2.27 (d, [4H] JP,H = 12 Hz, CH2),
1.83 (d, [12H] 2JP,H = 12 Hz, Me). 31P{1H} NMR (CD2Cl2, 298
K): δ 11.8 (s). IR (Nujol, cm-1): 345(m), 264(m).
[GeI2{Me2P(CH2)2PMe2}]. 1,2-Bis(dimethylphosphino)ethane
(0.075 g, 0.50 mmol) was added to a solution of GeI2 (0.163 g,
0.50 mmol) in CH3CN (5 mL) at room temperature. After stirring
for 30 min, the volatiles were removed in vacuo to leave the white
residue. Yield: 0.19 g, 92%. Colorless crystals were obtained by
slow evaporation of the solvent from an acetonitrile solution. Anal.
Calcd for C6H16GeI2P2: C, 15.1; H, 3.4. Found: C, 15.4; H, 3.6. 1H
NMR (CD2Cl2, 298 K): δ 2.31 (d, [4H] 2JP,H = 12 Hz, CH2), 1.97
(d, [12H] 2JP,H = 12 Hz, Me). 31P{1H} NMR (CD2Cl2, 298 K): δ
0.7 (s). IR (Nujol, cm-1): 320(br w).
[GeBr2{o-C6H4(PMe2)2}]. The same method as for [GeBr2{o-
C6H4(PPh2)2}] above is used, but using o-C6H4(PMe2)2; the
white precipitate was collected by filtration and washed with
CH2Cl2. Yield: 0.15 g, 71%. Anal. Calcd for C10H16Br2-
[GeCl{o-C6H4(AsMe2)2}][GeCl3]. 1,2-Bis(dimethylarsino)-
benzene (0.140 g, 0.50 mmol) was added to a solution of
[GeCl2(1,4-dioxane)] (0.230 g, 1.00 mmol) in CH2Cl2 (15 mL)
at room temperature with stirring, which gave precipitation
of a white solid. After stirring for 30 min, the solvent was
removed in vacuo. The white solid residue was washed with
diethyl ether and dried in vacuo. Yield: 0.22 g, 75%. Colorless
crystals were obtained by slow evaporation of the solvent
GeP2 CH2Cl2: C, 25.6; H, 3.5. Found: C, 25.4; H, 3.8. 1H
3
NMR (CD2Cl2, 298 K): δ 7.68 (m, [4H], o-C6H4), 2.04 (d,
[12H] J = 12 Hz, Me). 31P{1H} NMR (CD2Cl2, 298 K): δ
13.2 (s). IR (Nujol, cm-1): 339(m), 302(s), 288(w). Colorless
crystals were obtained by slow evaporation of the solvent from
an acetonitrile solution.
[GeI2{o-C6H4(PMe2)2}]. 1,2-Bis(dimethylphosphino)benzene
(0.100 g, 0.50 mmol) was added to a solution of GeI2 (0.163 g,
0.50 mmol) in CH3CN (3 mL) at room temperature with stirring,
which immediately precipitated a white solid. After stirring for
30 min, the solid was collected by filtration, washed with a small
amount of CH3CN solvent, and dried in vacuo. Yield: 0.18 g, 70%.
Colorless crystals were obtained by slow evaporation of the solvent
from an acetonitrile solution. Anal. Calcd for C10H16GeI2P2: C,
22.8; H, 3.1. Found: C, 22.8; H, 3.1. 1H NMR (CD2Cl2, 298 K): δ
7.69 (m, [4H], o-C6H4), 2.18 (d, [12H] J = 12 Hz, Me). 31P{1H}
NMR (CD2Cl2, 298 K): δ 0.4 (s). IR (Nujol, cm-1): 338(w),
301(m), 234(w).
from a dichloromethane solution. Anal. Calcd for C10H16
-
As2Cl4Ge2: C, 21.0; H, 2.8. Found: C, 21.6; H, 2.8. 1H NMR
(CD2Cl2, 298 K): δ 7.44 (m, [2H] o-C6H4), 7.31 (m, [2H]
o-C6H4), 1.30 (s, [12H] Me). IR (Nujol, cm-1) 343(m),
329(m),* 309(w), 271(vs)*. Raman (cm-1): 355(m), 328(m),*
305(m), 255(s),* 216(m) (*= [GeCl3]-).
[GeBr2{o-C6H4(AsMe2)2}]. The same method as for
[GeBr2{o-C6H4(PPh2)2}] above is used, but using o-C6H4-
(AsMe2)2, yielding a white solid. Yield: 0.18 g, 72%. Colorless
crystals were obtained by slow evaporation of the solvent from a
CH2Cl2 solution. Anal. Calcd for C10H16As2Br2Ge CH2Cl2: C,
3
21.9; H, 3.0. Found: C, 21.7; H, 3.3. 1H NMR (CD2Cl2, 298 K): δ
7.51 (m, [2H] o-C6H4), 7.44 (m, [2H] o-C6H4), 1.54 (s, [12H] Me).
IR (Nujol, cm-1): 356(s), 270(s), 253(s).
[GeCl2{Et2P(CH2)2PEt2}]. The same method as for
[GeCl2{o-C6H4(PPh2)2}] above is used, but using Et2P-
(CH2)2PEt2, yielding a white solid. Yield: 0.16 g, 92%. Color-
less crystals were obtained by slow evaporation of the solvent
[GeI2{o-C6H4(AsMe2)2}].
1,2-Bis(dimethylarsino)benzene
from
C
a
10H24Cl2GeP2 1/4CH2Cl2: C, 33.2; H, 6.7. Found: C, 33.5;
dichloromethane solution. Anal. Calcd for
(0.140 g, 0.50 mmol) was added to a solution of GeI2 (0.163 g,
0.50 mmol) in CH3CN (3 mL) at room temperature with stirring,
which gave precipitation of a white solid and a solution color
3
H, 7.1. 1H NMR (CD2Cl2, 298 K): δ 2.20 (m, [8H], CH2), 1.15

Article
Inorganic Chemistry, Vol. 49, No. 2, 2010 759
Table 9. Crystallographic Parametersa
compound
formula
M
[GeCl2{o-C6H4(PPh2)2}] [GeBr2{o-C6H4(PPh2)2}] [GeI2{o-C6H4(PPh2)2}] [GeCl2{o-C6H4(PMe2)2}] [GeBr2{o-C6H4(PMe2)2}]
C
30H24Cl2GeP2
C30H24Br2GeP2
678.84
monoclinic
P21/n (no. 14)
10.578(3)
14.164(3)
18.588(3)
90
C30H24GeI2P2
772.82
monoclinic
P21/n (no. 14)
11.0465(18)
14.192(3)
18.503(3)
90
C10H16Cl2GeP2
341.66
monoclinic
C2/c (no. 15)
28.542(4)
7.4696(10)
14.101(3)
90
C10H16Br2GeP2
430.58
monoclinic
C2/c (no. 15)
29.441(4)
7.5466(10)
14.395(2)
90
589.92
orthorhombic
P212121 (no. 19)
10.438(3)
14.335(4)
18.996(5)
90
cryst syst
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
90
90
98.068(15)
90
97.270(12)
90
109.928(10)
90
110.646(7)
90
3
˚
U [A ]
2842.1(13)
4
1.396
2757.4(10)
4
4.143
2877.5(9)
4
3.339
2826.3(8)
8
2.740
2992.9(7)
8
7.571
Z
μ(Mo KR) [mm-1
total no. reflns
Rint
]
]
]
27455
0.095
6451
317
0.052
0.116
0.091
0.109
36845
0.108
6287
316
0.048
0.094
0.096
0.111
30988
0.084
6526
316
0.068
0.095
0.143
0.160
15378
0.073
3243
140
0.046
0.068
0.092
0.104
18434
0.050
3413
140
0.032
0.041
0.062
0.066
unique reflns
no. of params
R1 [Io>2σ(Io)]
R1 [all data]
wR2 [Io>2σ(Io)]
wR2 [all data]
compound
[GeI2{o-C6H4(PMe2)2}]
[GeCl2{Me2P(CH2)2PMe2}]
[GeBr2{Me2P(CH2)2PMe2}]
[GeI2{Me2P(CH2)2PMe2}]
formula
M
C
10H16GeI2P2
C6H16Cl2GeP2
293.62
monoclinic
C2/c (no. 15)
9.7602(15)
10.533(2)
12.113(2)
90
110.909(10)
90
1163.3(3)
4
3.313
7459
0.042
1345
53
0.024
0.028
0.052
0.054
C6H16Br2GeP2
382.54
monoclinic
C2/c (no. 15)
9.809(2)
10.834(3)
12.324(3)
90
109.803(3)
90
1232.2(5)
4
9.180
6301
0.027
1402
53
0.019
0.023
0.047
0.049
C6H16GeI2P2
476.52
triclinic
P1 (no. 2)
7.586(2)
7.648(2)
12.419(4)
74.683(15)
81.153(15)
74.691(15)
667.5(3)
2
7.113
12806
0.050
3042
104
0.045
0.056
0.098
0.104
524.56
monoclinic
P21/c (no. 14)
15.369(3)
7.717(2)
14.814(3)
90
116.741(10)
90
1569.0(5)
4
6.064
15015
0.048
3569
140
0.053
0.070
0.110
0.119
cryst syst
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
3
˚
U [A ]
Z
μ(Mo KR) [mm-1
total no. reflns
Rint
unique reflns
no. of params
R1 [Io>2σ(Io)]
R1 [all data]
wR2 [Io>2σ(Io)]
wR2 [all data]
compound
[GeCl2{Et2P(CH2)2PEt2}]
[GeBr2{Et2P(CH2)2PEt2}]
[GeI2{o-C6H4(AsMe2)2}]
[GeCl{o-C6H4(AsMe2)2}][GeCl3]
formula
M
C
10H24Cl2GeP2
C10H24Br2GeP2
438.64
monoclinic
C2/c (no. 15)
12.343(2)
10.339(2)
13.732(2)
90
C10H16As2GeI2
612.48
monoclinic
P21/n (no. 14)
9.1163(10)
8.8655(10)
20.265(3)
90
C10H16As2Cl4Ge2
573.05
orthorhombic
Pnma (no. 62)
18.572(2)
9.8246(10)
9.9071(10)
90
349.72
monoclinic
C2/c (no. 15)
12.116(1)
10.146(1)
13.548(1)
90
cryst syst
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
114.188(1)
90
114.261(2)
90
101.324(7)
90
90
90
3
˚
U [A ]
1519.2(2)
4
2.550
1597.6(5)
4
7.093
1606.0(3)
4
9.815
1807.6(3)
4
7.532
Z
μ(Mo KR) [mm-1
total no. reflns
Rint
10691
0.026
1740
69
0.022
0.025
0.051
0.053
8945
0.024
1830
69
0.019
0.021
0.044
0.045
19228
0.057
3679
140
0.045
0.063
0.084
0.094
16937
0.026
2167
90
0.029
0.031
0.077
0.078
unique reflns
no. of params
R1 [Io>2σ(Io)]
R1 [all data]
wR2 [Io>2σ(Io)]
wR2 [all data]
P
P
P
P
a
Common items: temperature = 120 K; wavelength (Mo KR) = 0.71073 A; θ(max) = 27.5°; R1 = ||Fo| - |Fc||/ |Fo|; wR2 = [ w(Fo2 - Fc2)2/
˚
4 1/2
wFo ] .

760 Inorganic Chemistry, Vol. 49, No. 2, 2010
Cheng et al.
change from yellow to pale pink. After stirring for 30 min, the
solvent was removed by filtration. The white solid residue was
washed with a small amount of CH3CN and dried in vacuo. Yield:
0.19 g, 63%. Colorless crystals were obtained by slow evaporation
of the solvent from an acetronitrile solution. Anal. Calcd for
C10H16As2GeI2: C, 19.6; H, 2.6. Found: C, 18.9; H, 2.6. 1H
NMR (CD2Cl2, 298 K): δ 7.51 (m, [4H] o-C6H4), 1.69
(s, [12H] Me). IR (Nujol, cm-1): 355(m), 248(w), 223(w).
stream. Structure solution and refinement were mostly straight-
forward (except as described below),22-24 with H atoms intro-
duced into the models in idealized positions using the default
C-H distance. The fit to the data for [GeCl2{o-C6H4(PPh2)2}] in
the noncentrosymmetric space group was slightly improved by
the inclusion of the SHELX TWIN/BASF commands in the
model. Selected bond lengths and angles are given in
Tables 2-8.
CCDC 724637-724641 and CCDC 749461-749468 contain
the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
X-Ray Crystallography. Details of the crystallographic data
collection and refinement parameters are given in Table 9.
Crystals suitable for single-crystal X-ray analysis were obtained
as described above. Data collections used a Bruker-Nonius
Kappa CCD diffractometer fitted with Mo KR radiation (λ =
˚
0.71073 A) and either a graphite monochromator or con-
focal mirrors, with the crystals held at 120 K in a nitrogen gas
Acknowledgment. We thank RCUK (EP/C006763/1) for
support.
€
€
(22) Sheldrick, G. M. SHELXS-97; University of Gottingen: Gottingen,
Germany, 1997.
Supporting Information Available: CIF files for the crystal
structures described. This material is available free of charge via
the Internet at http://pubs.acs.org.
€
€
(23) Sheldrick, G. M. SHELXL-97; University of Gottingen: Gottingen,
Germany, 1997.
(24) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876–879.