Higher nuclearity clusters containing osmium and tin atoms. Synthesis and structure of [(OC)3Os(SnMe2)]3, Os4(SnMe2)4(CO)14, and Os4(μ3-O)2(SnMe2) 4(CO)14

Article abstract of DOI:10.1021/om950670r

Pyrolysis of [(OC)₄Os(SnMe₂)]₂ (1) at 170°C gave [(OC)₃Os(SnMe₂)]₃ (2) as the major product. The structure of 2 reveals a planar triangulated (raftlike) Os₃Sn₃ unit (6 crystallographic symmetry, with Os-Os = 2.974(1) A? and Os-Sn = 2.667(1) and 2.673(1) A?). UV irradiation of 1 in hexane provided the yellow, insoluble Os₄(SnMe₂)₄(CO)₁₄ (3). The structure of 3 shows an essentially planar Os₄Sn₄ skeleton comprised of a central rhomboidal Os₂Sn₂ unit with each Os atom part of two outer Os₂Sn triangles. The Os-Sn bonds of the Os₂Sn₂ unit at 2.760(1) and 2.780(1) A? are significantly longer than the corresponding bonds of the Os₂Sn groups (2.678(1) and 2.727(1) A?); the Os-Os bonds in 3 are long at 3.0414(5) A. From the treatment of 1 in solution with Me₃NO, Os₄(μ₃-O)₂(SnMe₂) ₄(CO)₁₄ (4) was isolated in low yield. The structure of 4 has a central six-membered (OsOSn)₂ ring to which are fused two OsOSnOs rings such that each outer ring shares a common OsO edge with the central ring. The outer rings of 4 are planar, but the central ring has a boat conformation.

Full text of DOI:10.1021/om950670r

1582
Organometallics 1996, 15, 1582-1588
High er Nu clea r ity Clu ster s Con ta in in g Osm iu m a n d Tin
Atom s. Syn th esis a n d Str u ctu r e of [(OC)3Os(Sn Me2)]3,
Os4(Sn Me2)4(CO)14, a n d Os4(µ3-O)2(Sn Me2)4(CO)14
Weng Kee Leong, Frederick W. B. Einstein, and Roland K. Pomeroy*
Department of Chemistry, Simon Fraser University,
Burnaby, British Columbia, Canada V5A 1S6
Received August 28, 1995X
Pyrolysis of [(OC)4Os(SnMe2)]2 (1) at 170 °C gave [(OC)3Os(SnMe2)]3 (2) as the major
product. The structure of 2 reveals a planar triangulated (raftlike) Os3Sn3 unit (6h
crystallographic symmetry, with Os-Os ) 2.974(1) Å and Os-Sn ) 2.667(1) and 2.673(1)
Å). UV irradiation of 1 in hexane provided the yellow, insoluble Os4(SnMe2)4(CO)14 (3). The
structure of 3 shows an essentially planar Os4Sn4 skeleton comprised of a central rhomboidal
Os2Sn2 unit with each Os atom part of two outer Os2Sn triangles. The Os-Sn bonds of the
Os2Sn2 unit at 2.760(1) and 2.780(1) Å are significantly longer than the corresponding bonds
of the Os2Sn groups (2.678(1) and 2.727(1) Å); the Os-Os bonds in 3 are long at 3.0414(5)
Å. From the treatment of 1 in solution with Me3NO, Os4(µ3-O)2(SnMe2)4(CO)14 (4) was
isolated in low yield. The structure of 4 has a central six-membered (OsOSn)2 ring to which
are fused two OsOSnOs rings such that each outer ring shares a common OsO edge with
the central ring. The outer rings of 4 are planar, but the central ring has a boat conformation.
In tr od u ction
known clusters are replaced by ER2 units (E ) Si, Ge,
Sn, Pb; R ) organic group, H, halide). Here we report
our initial foray in this area, namely, attempts to
synthesize the analogue of Os4(CO)15 in which the two
wingtip Os(CO)4 groupings are replaced by SnMe2 units
(i.e., Os2(SnMe2)(CO)7). Iron compounds of formula Fe2-
(ER2)2(CO)7 have been reported.8 They have a geometry
similar to that of Fe2(CO)9, with ER2 units replacing two
of the three bridging carbonyls.8 Bridging carbonyl
ligands in osmium carbonyl cluster chemistry are rare,
however, and it was believed that Os2(SnMe2)2(CO)7, if
it could be prepared, might not contain a bridging
carbonyl. Although we have been unable to achieve the
synthesis of the target molecule, three novel higher
nuclearity clusters containing Os and Sn atoms have
been synthesized and are reported here.
The carbonyl cluster chemistry of osmium is more
extensive than for any other transition metal.1 For
example, there are 13 stable neutral binary carbonyls
of osmium now known,2 whereas at most four neutral
binary carbonyls are known for each of the other
3
transition metals (ruthenium forms Ru(CO)5 and Ru2-
(CO)94 (both of which are unstable), Ru3(CO)12, and the
5
little-studied polymeric [Ru(CO)4]n ). Of the binary
carbonyls of osmium, we have reported the synthesis
and structure of Os4(CO)15.6 This cluster has an un-
usual planar kite structure with adjacent long and short
peripheral Os-Os bonds, which we have rationalized
in terms of three-center, two-electron bonds, so as to
give bond orders of 0.5 and 1.5 for the peripheral metal-
metal bonds.6 More recent molecular orbital calcula-
tions by Mealli and Proserpio, however, do not support
this view.7
Exp er im en ta l Section
We have initiated a program into the synthesis of
clusters in which some of the Os(CO)4 fragments in
Standard Schlenk techniques were employed in the synthe-
ses. Solvents were rigorously dried and stored under nitrogen
before use. The precursor compounds Os3(CO)12 and Me2SnCl2
were obtained from commercial sources. The compound [(OC)4-
Os(SnMe2)]2 (1) was prepared from Na2Os(CO)4 and Me2SnCl2
by the literature method.9 An external, medium-pressure
mercury discharge lamp (200 W, Hanovia Model 654 A36)
contained in a water-cooled quartz jacket was employed in the
UV irradiation experiment; there was ∼5 cm between the UV
source and the edge of the reaction vessel. Infrared spectra
were obtained with a Perkin-Elmer 983 spectrometer. NMR
spectra were recorded on a Bruker SY-100 or WM400 spec-
trometer. Microanalyses were performed by M. K. Yang of the
Microanalytical Laboratory of Simon Fraser University.
X Abstract published in Advance ACS Abstracts, J anuary 1, 1996.
(1) (a) Deeming, A. J . Adv. Organomet. Chem. 1986, 26, 1. (b)
Vargas, M. D.; Nicholls, J . N. Adv. Inorg. Chem. Radiochem. 1986,
30, 123. (c) Cifuentes, M. P.; Humphrey, M. G. In Comprehensive
Organometallic Chemistry II; Wilkinson, G., Stone, F. G. A., Abel, E.
W., Eds.; Pergamon: New York, 1995; Vol. 7, Chapter 16.
(2) (a) Pomeroy, R. K. J . Organomet. Chem. 1990, 383, 387. (b)
Wang, W.; Einstein, F. W. B.; Pomeroy, R. K. J . Chem. Soc., Chem.
Commun. 1992, 1737. (c) Coughlin, D.; Lewis, J .; Moss, J . R.; Edwards,
A. J .; McPartlin, M. J . Organomet. Chem. 1993, 444, C53.
(3) (a) Calderazzo, F.; L’Eplattenier, F. Inorg. Chem. 1967, 6, 1220.
(b) Rushman, P.; van Buuren, G. N.; Shiralian, M.; Pomeroy, R. K.
Organometallics 1983, 2, 693.
(4) Moss, J . R.; Graham, W. A. G. J . Chem. Soc., Dalton Trans. 1977,
95.
(5) (a) Hastings, W. R.; Baird, M. C. Inorg. Chem. 1986, 25, 2913.
(b) Maschiocchi, N.; Moret, M.; Cairati, P.; Ragaini, F.; Sironi, A. J .
Chem. Soc., Dalton Trans. 1993, 471.
(6) (a) J ohnston, V. J .; Einstein, F. W. B.; Pomeroy, R. K. Organo-
metallics 1988, 7, 1867. (b) Einstein, F. W. B.; J ohnston, V. J .; Ma, A.
K.; Pomeroy, R. K. Can. J . Chem. 1995, 73, 1223.
(8) (a) Kummer, D.; Furrer, J . Z. Naturforsch., B 1971, 26, 162. (b)
Marks, T. J .; Grynkewich, G. W. Inorg. Chem. 1976, 15, 1307. (c)
Bonny, A.; MacKay, K. M. J . Chem. Soc., Dalton Trans. 1978, 722. (d)
Corriu, R. J . P.; Moreau, J . J . E. J . Chem. Soc., Chem. Commun. 1980,
278.
(9) George, R. D.; Knox, S. A. R.; Stone, F. G. A. J . Chem. Soc.,
Dalton Trans. 1973, 972.
(7) Mealli, C.; Proserpio, D. M. J . Am. Chem. Soc. 1990, 112, 5484.
0276-7333/96/2315-1582$12.00/0 © 1996 American Chemical Society

Higher Nuclearity Clusters Containing Os and Sn
Organometallics, Vol. 15, No. 6, 1996 1583
Ta ble 1. Su m m a r y of Cr ysta l Da ta a n d Deta ils of In ten sity Collection for [(OC)4Os(Sn Me2)]2 (1),
[(OC)3Os(Sn Me2)]3 (2), Os4(Sn Me2)4(CO)14 (3), a n d Os4(µ3-O)(Sn Me2)4(CO)14‚C7H8 (4‚C7H8)
1
2
3
4
formula
fw
C12H12O8Os2Sn2
902.00
C15H18O9Os3Sn3
1268.96
C22H24O14Os4Sn4
1748.0
C29H32O16Os4Sn4
1872.1
cryst syst
space group
monoclinic
P21/n
hexagonal
P63/m
monoclinic
P21/n
monoclinic
P2/a
a, Å
b, Å
c, Å
9.1465(13)
11.9544(16)
9.8120(10)
95.592(10)
1067.8(2)
30.0-37.0
2
11.007(2)
9.668(2)
17.825(2)
11.203(1)
105.05(1)
1864.4(4)
32.0-40.0
2
13.895(2)
12.550(2)
14.053(2)
113.56(1)
2246.3(6)
40.0-50.0
2
12.818(2)
â, deg
V, Å3
1345.0(4)
29.8-39.1
2
3.134
169.27
0.09 × 0.12 × 0.13
0.196-0.333
2.0-50.0
0.85 + 0.35 tan θ
0.785-3.296
818
2θ range of unit cell, deg
Z
D
calc, g cm-3
2.806
142.29
3.114
162.89
2.768
135.32
µ(Mo KR), cm-1
cryst size, mm
0.09 × 0.06 × 0.09
0.324-0.462
4.0-45.0
0.90 + 0.35 tan θ
0.659-3.30
1386
1034
89
0.024
0.026
0.14 × 0.08 × 0.07
0.357-0.545
4.0-48.0
0.80 + 0.35 tan θ
0.75-3.30
2914
2338
169
0.022
0.024
0.23 x 0.16 × 0.05
0.156-0.706
4.0-50.0
0.85 + 0.35 tan θ
0.96-1.30
3942
3078
200
0.040
0.042
transmission coeff
scan range (2θ), deg
scan width (ω), deg
scan rate (ω), deg min-1
no. of unique rflns
no. of obsd rflnsa
no. of params
635
54
0.022
0.023
Rb
Rw
c
instrument instability factor (k)
extinction
largest shift/esd in final ls cycle
largest positive/negative residual
electron density in final diff map, e Å-3
GOFd
0.00009
0.179(14)
0.02
0.00005
0.415(15)
0.01
0.00005
0.072(12)
0.11
0.00007
0.083(19)
0.07
0.55/-0.43(12)
0.60/-0.49(11)
1.0/-0.6(2)
1.8/-1.3(3)
1.3
1.5
1.3
2.2
F(000)
799.76
1102.53
1543.53
1675.51
a
b
2
2
d
Io > 2.5σ(Io). R ) ∑||Fo| - |Fc||/∑|Fo|. c Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2, w ) 1/(σ2(Fo) + k|Fo| ). GOF ) [∑w(|Fo| - |Fc|)2/(degrees of
freedom)]1/2
.
P r ep a r a t ion of [(OC)3Os(Sn Me2)]3 (2). A Carius tube
(fitted with a Teflon valve) with [(OC)4Os(SnMe2)]2 (1; 55 mg,
0.061 mmol) in hexane (10.0 mL) was cooled to -196 °C and
evacuated. The solution was degassed with three freeze-
pump-thaw cycles; the vessel and its contents were heated
at 170 °C for 3 days, during which time the solution changed
from pale yellow to golden yellow. The tube was cooled and
the solution transferred to a Schlenk flask; the solvent was
removed on the vacuum line and the residue extracted with
hexane (3 × 2 mL) and toluene (5 and 3 mL). The combined
hexane extracts and combined toluene extracts were each
subjected to chromatography on silica and gave the same three
bands. The first band yielded [(OC)3Os(SnMe2)]3 (2) (total
yield 22 mg, 22%). The analytical sample of 2 was obtained
by recrystallization from toluene. As such, two forms of yellow
crystals of 2 were obtained: long needles that contained 0.5
C, 15.12; H, 1.38. Found: C, 15.30; H, 1.41. Compound 3 is
only sparingly soluble in warm CH2Cl2 and CHCl3.
P r ep a r a tion of Os4(µ3-O)2(Sn Me2)4(CO)14 (4). To a solu-
tion of 1 (184 mg, 0.204 mmol) in CH2Cl2 (15.0 mL) at -5 °C
was added dropwise, over ca. 30 min, a solution of freshly
sublimed Me3NO (31 mg, 0.41 mmol) in CH3CN (15.0 mL). The
solution rapidly turned a deeper yellow. The solution was
stirred for 60 min following the addition, after which it was
quickly filtered through a short column of silica (∼1 × 2.5 cm
between layers of Celite); the column was washed with CH2-
Cl2 (2 × 5 mL). The CH2Cl2 solutions were combined and
evaporated to dryness on the vacuum line. The residue was
extracted with hexane (4 × 5 mL). The combined hexane
extracts were filtered, concentrated, and cooled to -20 °C to
afford a precipitate consisting of a yellow powder (identified
by its IR spectrum as 1) along with some orange crystals. The
latter were separated by hand and recrystallized from toluene
to afford yellow crystals of 4 (estimated yield 10%) as the
toluene solvate (presence confirmed by X-ray crystallography)
along with colorless blocks of 1, which were again separated
by hand. Compound 4: IR (hexane) ν(CO) 2088 (w), 2044.5
1
molecule of toluene (confirmed by H NMR spectroscopy) and
hexagonal prisms that did not contain solvent (by X-ray
crystallography). IR (hexane): ν(CO) 2043 (m), 2009.5 (s),
1978 (m) cm-1
.
1H NMR (CDCl3): δ 0.99 (J SnH ) 43.0, 44.4
Hz). Anal. Calcd for C15H18O9Os3Sn3‚0.5C7H8: C, 16.90; H,
1.69. Found: C, 17.11; H, 1.63.
The constituents of the second (red) and third (yellow) bands
that yielded only trace amounts (∼2 mg) of material were not
identified.
(m), 2021 (s), 2012 (vs) 2002 (s), 1968.5 (w) cm-1 1H NMR
;
(CDCl3) δ 0.70, 0.58. Anal. Calcd for C22H24O16Os4Sn4‚C7H8:
C, 18.61; H, 1.72. Found: C, 18.48; H, 1.67.
P r ep a r a tion of Os4(Sn Me2)4(CO)14 (3). A Pyrex Carius
tube fitted with a Teflon valve and containing 1 (220 mg, 0.244
mmol) in hexane (8.0 mL) was evacuated at -196 °C and the
solution degassed with two freeze-pump-thaw cycles. The
solution was subjected to UV photolysis for 14 h; the initially
pale yellow solution turned golden yellow, and a precipitate
formed during the course of the photolysis. An IR spectrum
of the supernatant solution at this stage showed major peaks
due to unreacted 1 and very weak bands at 2085, 1969, and
1953 cm-1. The yellow precipitate was washed with hexane
and dried on the vacuum line to afford analytically pure
Os4(SnMe2)4(CO)14 (65 mg, 30%). IR (CH2Cl2): ν(CO) 2089.5
X-r a y An a lysis of 1-4. Crystals suitable for X-ray crystal-
lography were obtained by recrystallization from the following
solvents: hexane (1), toluene (2, 4), and chloroform (3). (The
nonsolvated form of 2 was used in the X-ray study.) In each
case a crystal was mounted, in air, on an Enraf-Nonius
diffractometer and intensity data were collected with the use
of graphite-monochromated Mo KR radiation. The final unit
cell was determined from 25 well-centered high-angle reflec-
tions that were widely scattered in reciprocal space. Two
intensity standards were measured at intervals of 60 min of
X-ray exposure time. Absorption corrections were made with
either a Gaussian numerical integration (checked against
(m), 2019 (s), 1994.5 (m, sh), 1964.5 (w) cm-1
. IR (Nujol):
ν(CO) 2084 (ms), 2031 (m), 2005 (s), 1989 (ms), 1979.5 (ms),
1968 (w), 1957 (ms) cm-1. Anal. Calcd for C22H24O14Os4Sn4:
(10) Busing, W. R.; Levy, H. A. Acta Crystallogr. 1957, 10, 180.

1584 Organometallics, Vol. 15, No. 6, 1996
Leong et al.
Ta ble 4. F r a ction a l Atom ic Coor d in a tes a n d
Ta ble 2. F r a ction a l Atom ic Coor d in a tes a n d
Isotr op ic or Equ iva len t Isotr op ic Tem p er a tu r e
F a ctor s (Å2) for [(OC)4Os(Sn Me2)]2
Isotr op ic or Equ iva len t Isotr op ic Tem p er a tu r e
F a ctor s (Å2) for [(OC)3Os(Sn Me2)]3
atom
x/a
y/b
z/c
U(iso)
occ
atom
x/a
y/b
z/c
U(iso)
Os(1) 0.58782(5) 0.54045(3) 0.20953(4) 0.0516
Sn(1) 0.32878(8) 0.53075(6) 0.03883(7) 0.0517
0.8921(7)
0.8921(7)
0.8921(7)
0.8921(7)
0.8921(7)
0.8921(7)
Os(1)
Sn(1)
O(11)
O(12)
C(1)
0.54047(4)
0.75249(6)
0.3212(9)
0.5365(5)
0.7879(8)
0.404(1)
0.38156(4)
0.64566(7)
0.4699(9)
0.3841(5)
0.7757(8)
0.437(1)
0.2500
0.2500
0.2500
0.0110(5)
0.1162(7)
0.2500
0.0385
0.0420
0.0915
0.0738
0.0682
0.0665
0.0533
O(11) 0.615(1)
O(12) 0.401(1)
O(13) 0.536(1)
O(14) 0.903(1)
C(11) 0.603(1)
C(12) 0.475(1)
C(13) 0.554(1)
C(14) 0.785(1)
0.7739(6)
0.6141(9)
0.2895(6)
0.5388(7)
0.687(1)
0.589(1)
0.382(1)
0.538(1)
0.6938(9)
0.421(1)
0.0824(9) 0.0879
0.4375(9) 0.1060
0.2451(8) 0.0851
0.355(1)
0.131(1)
0.353(1)
0.232(1)
0.301(1)
0.027(1)
0.123(1)
0.1029
C(11)
C(12)
0.067(3) 0.8921(7)
0.074(3) 0.8921(7)
0.060(3) 0.8921(7)
0.072(3) 0.8921(7)
0.084(4) 0.8921(7)
0.103(4) 0.8921(7)
0.5396(7)
0.3819(7)
0.0985(8)
Ta ble 5. Bon d Len gth s (Å) a n d Selected Bon d
An gles (d eg) for [(OC)3Os(Sn Me2)]3 (2)
C(1)
C(2)
0.228(1)
0.176(1)
Bond Lengths
Os(1)-Os(1′)
Os(1)-Sn(1)
Os(1′)-Sn(1)
Os(1)-C(11)
2.974(1)
2.667(1)
2.673(1)
1.88(1)
Os(1)-C(12)
Sn(1)-C(1)
C(11)-O(11)
C(12)-O(12)
1.94(1)
2.141(7)
1.14(1)
1.12(1)
Os(10) 0.3516(4) 0.4955(3)
Sn(10) 0.6139(7) 0.5871(5)
O(111) 0.5433(4) 0.2946(3)
O(112) 0.4019(4) 0.6261(3)
0.1616(4) 0.0517
0.0961(6) 0.0516
0.2578(4) 0.08(2) 0.1079(7)
0.4326(4) 0.08(2) 0.1079(7)
0.1079(7)
0.1079(7)
O(113) 0.2122(4) 0.6907(3) -0.0062(4) 0.08(2) 0.1079(7)
Bond Angles
Sn(1)-Os(1)-Sn(1′) 172.31(2) Os(1)-Sn(1)-Os(1′)
O(114) 0.0597(4) 0.3737(3)
C(111) 0.4722(4) 0.3687(3)
C(112) 0.3829(4) 0.5774(3)
C(113) 0.2678(4) 0.6229(3)
C(114) 0.1712(4) 0.4189(3)
C(101) 0.7912(7) 0.5368(5)
C(102) 0.6036(7) 0.7692(5)
0.1849(4) 0.08(2) 0.1079(7)
0.2219(4) 0.067(3) 0.1079(7)
0.3355(4) 0.074(3) 0.1079(7)
0.0556(4) 0.060(3) 0.1079(7)
0.1720(4) 0.072(3) 0.1079(7)
0.2412(6) 0.084(4) 0.1079(7)
0.1050(6) 0.103(4) 0.1079(7)
67.69(2)
119.8(2)
Os(1)-Sn(1)-C(1′) 119.9(2)
C(1) -Sn(1)-C(1′) 106.4(5)
Sn(1)-Os(1)-C(11)
Sn(1)-Os(1)-C(12)
Sn(1)-Os(1)-C(12)
C(11)-Os(1)-C(12)
94.7(3)
90.0(2)
90.0(2)
89.6(2)
Os(1)-Sn(1)-C(1)
Ta ble 6. F r a ction a l Atom ic Coor d in a tes a n d
Isotr op ic or Equ iva len t Isotr op ic Tem p er a tu r e
F a ctor s (Å2) for Os4(Sn Me2)4(CO)14
Ta ble 3. Bon d Len gth s (Å) a n d Selected Bon d
An gles (d eg) for [(OC)4Os(Sn Me2)]2 (1)
atom
x/a
y/b
z/c
U(iso)
Bond Lengths
Os(1)
Os(2)
Sn(1)
Sn(2)
O(11)
O(12)
O(13)
O(14)
O(21)
O(22)
O(23)
C(1)
C(2)
C(3)
C(4)
C(11)
C(12)
C(13)
C(14)
C(21)
C(22)
C(23)
1.02359(4)
0.99253(3)
1.23932(6)
1.16434(6)
1.1447(8)
0.7180(8)
0.9633(9)
1.1632(8)
1.1137(8)
0.6940(6)
0.9319(7)
1.412(1)
1.331(1)
1.348(1)
1.242(1)
1.096(1)
0.829(1)
0.982(1)
1.111(1)
0.32479(2)
0.42968(2)
0.35853(3)
0.47662(3)
0.4602(4)
0.3271(5)
0.1938(4)
0.2194(4)
0.5708(3)
0.4398(3)
0.3019(4)
0.4234(6)
0.2726(6)
0.5426(6)
0.3884(5)
0.4098(5)
0.3291(5)
0.2419(5)
0.2579(5)
0.5177(5)
0.4334(4)
0.3485(4)
0.38549(3)
0.16599(3)
0.28569(5)
0.01839(5)
0.5498(6)
0.4195(8)
0.1989(6)
0.5961(6)
0.3139(6)
0.2121(6)
0.0233(6)
0.3966(8)
0.1972(9)
0.1136(8)
-0.080(1)
0.4903(9)
0.4030(9)
0.2686(9)
0.5159(9)
0.2599(8)
0.1991(7)
0.0488(8)
0.0389
0.0308
0.0395
0.0376
0.0765
0.0769
0.0816
0.0724
0.0674
0.0502
0.0622
0.0679
0.0685
0.0650
0.0627
0.056(2)
0.061(3)
0.060(3)
0.059(2)
0.044(2)
0.041(2)
0.045(2)
Os(1)-Sn(1)
Os(1′)-Sn(1)
Os(1)-C(11)
Os(1)-C(12)
Os(1)-C(13)
2.768(1)
2.758(1)
1.93(1)
1.92(1)
1.93(1)
Sn(1)-C(1)
Os(1)-C(14)
Sn(1)-C(2)
C-O
2.15(1)
1.93(1)
2.14(1)
1.13(1)-1.16(1)
Bond Angles
Sn(1)-Os(1)-Sn(1′) 75.32(3) Os(1)-Sn(1)-C(1)
109.3(3)
Os(1′)- Sn(1)-C(1) 112.6(3)
Os(1)-Sn(1)-C(2) 110.1(4)
Os(1′)-Sn(1)-C(2) 113.5(4)
C(1) -Sn(1)-C(2) 106.5(5)
C(12)-Os(1)-C(14) 101.9(5)
C(11)-Os(1)-C(13) 162.8(5)
Sn(1)-Os(1)-C(14) 170.0(4)
Sn(1′)-Os(1)-C(14) 94.7(4)
Os(1)-Sn(1)-Os(1′) 104.68(3) Os(1)-C(11)-O(11) 178.3(11)
æ-scan measurements).10 Data reduction included corrections
for intensity scale variation and for Lorentz and polarization
effects.
The positions of the Os atoms were determined by direct
methods or from Patterson maps. Subsequent electron density
difference syntheses revealed the remaining non-hydrogen
atoms. Hydrogen atoms were generally not located and were
placed in calculated positions (C-H distance 0.96 Å) and given
isotropic temperature factors 10% larger than the thermal
parameter of the carbon atom to which they were attached.
The coordinates of carbon atoms with attached hydrogen atoms
were linked so that the derived coordinates included contribu-
tions from derivatives from the appropriate atom sites. For
all cases an extinction parameter was required in the assign-
ment. Unit weights were employed initially, but at the final
1.0679(9)
0.8071(9)
0.9517(9)
ment were from the NRCVAX12 crystal structure system. The
program suite CRYSTALS13 was employed in the final refine-
ment. All computations were carried out on a MicroVAX-11
computer. Crystallographic data are summarized in Table 1.
Final fractional coordinates for the non-hydrogen atoms of 1-4
are given in Tables 2, 4, 6, and 8, respectively, and bond length
and angle data are in Tables 3, 5, 7, and 9, respectively.
Com p ou n d 1. The two intensity standards showed steady
decay (20-30%) with time. There was a half-molecule in the
asymmetric unit. The final model had the Os, Sn, and O atoms
anisotropic. Two large residual peaks were found in the
difference map, which were interpreted as disordered Os and
Sn atoms; these were located such that the Os and Sn atom
positions were interchanged, with the plane of the disordered
molecule tilted with respect to the main molecule. The
disorder was modeled with a complete, partial-occupancy
molecule as follows: the Os and Sn atoms (of the disordered
molecule) were given anisotropic temperature factors, which
were linked to the corresponding Sn and Os atoms, respec-
tively, of the ordered molecule. The O atoms were given one
common isotropic temperature factor, with the isotropic tem-
perature factors of the C atoms linked to their counterparts
in the main molecule. The Os(CO)4 and SnMe2 fragments were
stage of each refinement
a weighting scheme, based on
counting statistics, was adopted for which w(|Fo| - |Fc|)2 was
near constant as a function of both |Fo| and (sin θ)/λ. Com-
ments on individual structure determinations follow this
section. Complex scattering factors for neutral atoms11 were
employed in the calculation of structure factors. The programs
used for data reduction, structural solution, and initial refine-
(11) International Tables for X-ray Crystallography; Kynoch
Press: Birmingham, England, 1975; Vol. IV, p 99 (present distributor
Kluwer Academic: Dordrecht, The Netherlands).
(12) Gabe, E. J .; LePage, Y.; Charland, J .-P.; Lee, F. L. NRCVAX-
An Interactive Program System for Structural Analysis. J . Appl.
Crystallogr. 1989, 22, 384.
(13) Watkin, D. J .; Carruthers, J . R.; Betteridge, P. W. CRYSTALS;
Chemical Crystallography Laboratory, University of Oxford: Oxford,
England, 1985.

Higher Nuclearity Clusters Containing Os and Sn
Organometallics, Vol. 15, No. 6, 1996 1585
Ta ble 7. Bon d Len gth s (Å) a n d Selected Bon d
An gles (d eg) for Os4(Sn Me2)4(CO)14 (3)
Ta ble 9. Bon d Len gth s (Å) a n d Selected Bon d
An gles (d eg) for Os4(µ3-O)(Sn Me2)4(CO)14 (4)
Bond Lengths
Bond Lengths
Os(1)-Os(2)
Os(1)-Sn(1)
Os(2)-Sn(1)
Os(2)-Sn(2)
Os(2)-Sn(2′)
Os(1)-C(11)
Os(1)-C(12)
Os(1)-C(13)
Os(1)-C(14)
3.0414(5)
2.678(1)
2.727(1)
2.760(1)
2.780(1)
1.93(1)
1.94(1)
1.95(1)
1.91(1)
Sn(1)-C(1)
Sn(1)-C(2)
Sn(2)-C(3)
Sn(2)-C(4)
Os(2)-C(21)
Os(2)-C(22)
Os(2)-C(23)
C-O
2.14(1)
2.14(1)
2.16(1)
2.16(1)
1.92(1)
1.92(1)
1.93(1)
1.14(1)-1.15(1)
Os(1)-Os(2)
Os(1)-Sn(1)
Os(1)-C(11)
Os(1)-C(12)
Os(1)-C(13)
Os(1)-C(14)
Os(2)-C(21)
Os(2)-C(22)
Os(2)-C(23)
2.9702(8)
2.673(1)
1.96(1)
1.95(2)
1.95(2)
1.92(2)
1.93(1)
1.88(1)
1.93(1)
Os(2)-Sn(2)
Os(2)-O(1)
Sn(2)-O(1)
Sn(1)-C(1)
Sn(1)-C(2)
Sn(1)-O(1)
Sn(2)-C(3)
Sn(2)-C(4)
C-O
2.666(1)
2.158(7)
2.051(7)
2.14(1)
2.11(1)
2.034(8)
2.15(1)
2.17(1)
1.10(1)-1.15(1)
Bond Angles
55.00(2) Os(2)-Os(1)-Sn(1)
Os(1)-Os(2)-Sn(2) 136.24(2) Sn(2)-Os(2)-Sn(2′)
Bond Angles
72.40(3) C(21)-Os(2)-C(22)
Os(1)-Os(2)-Sn(1)
56.53(2)
70.72(2)
C(12)-Os(1)-C(14) 101.3(4)
Os(2)-Os(1)-Sn(1)
90.4(5)
C(11)-Os(1)-C(13) 165.7(6)
C(12)-Os(1)-C(14) 100.4(6)
C(21)-Os(2)-C(23) 171.0(6)
C(11)-Os(1)-C(13) 169.2(4)
C(22)-Os(2)-C(23)
91.2(5)
C(21)-Os(2)-C(22)
C(22)-Os(2)-C(23)
Os(1)-Sn(1)-C(1)
Os(1)-Sn(1)-C(2)
C(1) -Sn(1)-C(2)
Os(2)-Sn(2)-C(3)
Os(2)-Sn(2)-C(4)
C(3) -Sn(2)-C(4)
96.1(3)
96.9(3)
C(21)-Os(2)-C(23) 165.4(4)
Os(1)-Sn(1)-O(1)
Os(1)-Sn(1)-C(1)
Os(1)-Sn(1)-C(2)
O(1) -Sn(1)-C(1)
O(1) -Sn(1)-C(2)
C(1) -Sn(1)-C(2)
96.4(2)
120.2(4)
116.2(4)
103.1(4)
104.3(5)
112.5(6)
Os(2)-Sn(2)-O(1′) 112.0(2)
Os(1)-Sn(1)-Os(2)
Os(2)-Sn(1)-C(1)
Os(2)-Sn(1)-C(2)
68.47(2)
119.0(3)
121.3(3)
Os(2)-Sn(2)-C(3)
Os(2)-Sn(2)-C(4)
O(1′) -Sn(2)-C(3)
O(1′) -Sn(2)-C(4)
C(3) -Sn(2)-C(4)
111.2(4)
122.9(4)
101.1(4)
101.7(4)
105.6(5)
117.0(3)
119.6(3)
107.5(4)
114.4(3)
115.3(3)
107.4(4)
Os(2)-Sn(2)-Os(2′) 109.28(2)
Os(2′)- Sn(2)-C(3)
Os(2′)- Sn(2)-C(4)
105.0(2
104.5(3)
Os(1)-Os(2)-Sn(2) 175.89(3) Os(2)-O(1) -Sn(1) 105.7(3)
Os(1)-Os(2)-O(1)
Sn(2)-Os(2)-O(1)
85.5(2)
98.5(2)
Os(2)-O(1) -Sn(2′) 126.0(4)
Sn(1)-O(1) -Sn(2′) 127.3(4)
Ta ble 8. F r a ction a l Atom ic Coor d in a tes a n d
Isotr op ic or Equ iva len t Isotr op ic Tem p er a tu r e
F a ctor s (Å) for Os4(µ3-O)(Sn Me2)4(CO)14
geometry; data for θ >15° were collected with the azimuth
position corresponding to minimum absorption. The two
intensity standards showed a regular 30% decrease over the
period of data collection. A toluene molecule was disordered
about the crystallographic 2-fold axis, with the methyl group
off it. The toluene molecule was modeled with isotropic carbon
and hydrogen atoms, with the phenyl ring carbons regularized
to a hexagon of side 1.39 Å; the C and H atoms were given a
common temperature factor for each atom type. These solvent
molecules were refined as rigid groups pivoted at the ring
centers by dummy atoms. The two partial occupancy mol-
ecules had their total occupancy constrained to fill the site
completely (i.e. 0.5). All non-hydrogen atoms of the cluster
molecule had anisotropic thermal parameters in the final
model.
atom
x/a
y/b
z/c
U(iso)
occ
Os(1) 0.40715(4) 0.18024(4) 0.24854(4) 0.0459
Os(2) 0.38972(4) 0.26702(4) 0.43765(4) 0.0390
Sn(1) 0.20311(6) 0.20582(7) 0.20598(7) 0.0443
Sn(2) 0.38846(6) 0.34108(7) 0.61493(7) 0.0414
O(1)
0.2225(5)
0.2667(6)
-0.0383(8)
0.1747(9)
0.4142(8)
0.0946(9)
0.0486(7)
0.2597(8)
0.5042(7)
0.042(1)
0.178(1)
0.329(1)
0.125(1)
0.128(1)
0.261(1)
0.415(1)
0.070(1)
0.328(1)
0.299(1)
0.508(1)
0.370(2)
0.279(2)
0.179(2)
0.170(2)
0.262(3)
0.362(2)
0.288(4)
0.386(2)
0.335(2)
0.225(2)
0.166(2)
0.217(3)
0.327(3)
0.169(4)
0.3466(6)
0.3306(9)
0.349(1)
0.1747(9)
0.0363(9)
0.5286(8)
0.5455(9)
0.3820(8)
0.303(1)
0.316(1)
0.205(1)
0.115(1)
0.491(1)
0.507(1)
0.401(1)
0.191(1)
0.100(1)
0.745(1)
0.638(1)
0.000(4)
0.057(3)
0.000(4)
-0.033(4)
-0.071(3)
-0.046(4)
0.126(4)
-0.035(4)
0.025(3)
0.019(3)
-0.045(3)
-0.104(3)
-0.099(3)
0.084(4)
0.0416
0.0798
0.0824
0.0784
0.0762
0.0697
0.0709
0.0632
0.0561
0.0724
0.0594
0.0574
0.0517
0.0482
0.0478
0.0658
0.0739
0.0632
0.0607
0.068(6) 0.26(1)
0.068(6) 0.26(1)
0.068(6) 0.26(1)
0.068(6) 0.26(1)
0.068(6) 0.26(1)
0.068(6) 0.26(1)
0.111(6) 0.26(1)
0.068(6) 0.24(1)
0.068(6) 0.24(1)
0.068(6) 0.24(1)
0.068(6) 0.24(1)
0.068(6) 0.24(1)
0.068(6) 0.24(1)
0.111(6) 0.24(1)
O(11) 0.3799(9)
O(12) 0.6489(8)
O(13) 0.3917(9)
O(14) 0.3768(9)
O(21) 0.3709(8)
O(22) 0.6241(7)
O(23) 0.4010(7)
C(11) 0.390(1)
C(12) 0.560(1)
C(13) 0.397(1)
C(14) 0.386(1)
C(21) 0.378(1)
C(22) 0.5364(9)
C(23) 0.3959(9)
Resu lts a n d Discu ssion
[(OC)4Os(Sn Me2)]2 (1). The cluster 1 was prepared,
in only moderate yield, by the standard methodology
shown in eq 1.9,14 In order to compare Os-Sn bond
C(1)
C(2)
C(3)
C(4)
0.105(1)
0.126(1)
0.5298(9)
0.361(1)
8 [Os(CO)4]2- Me SnCl , THF8
Na/NH3(l)
2
2
Os3(CO)12
C(51) 0.750(4)
C(52) 0.717(3)
C(53) 0.750(4)
C(54) 0.797(4)
C(55) 0.825(3)
C(56) 0.800(4)
C(57) 0.658(4)
C(61) 0.776(4)
C(62) 0.730(4)
C(63) 0.719(3)
C(64) 0.753(3)
C(65) 0.799(3)
C(66) 0.810(3)
C(67) 0.669(4)
[(OC)4(SnMe2)]2
(1)
1
lengths with lengths in the higher nuclearity clusters
described below, the structure of 1 was determined.
Unfortunately, as for the Fe analogue,15 the structure
was disordered and therefore of somewhat low quality.
16
A view of 1 is shown in Figure 1. Unlike Os4(CO)16
(to which 1 is an isolobal analogue), the tetrametallic
core of 1 is planar. Most unbridged Os-Sn bonds
reported in the literature are in the range 2.653(1)-
(14) Collman, J . P.; Murphy, D. W.; Fleischer, E. B.; Swift, D. Inorg.
Chem. 1974, 13, 1.
(15) Gilmore, C. J .; Woodward, P. J . Chem. Soc., Dalton Trans. 1972,
1387.
(16) Einstein, F. W. B.; J ohnston, V. J .; Pomeroy, R. K. Organome-
tallics 1990, 9, 2754.
refined as rigid groups by linking their coordinate shifts.
Finally, the total occupancy was constrained to be 1.
Com p ou n d 2. The intensity standards showed random
variations in the range (1%. All non-hydrogen atoms were
anisotropic in the final model.
(17) (a) Adams, R. D.; Katahira, D. A. Organometallics 1982, 1, 460.
(b) Cardin, C. J .; Cardin, D. J .; Parge, H. E.; Power, J . M. J . Chem.
Soc., Chem. Commun. 1984, 609. (c) Wiswanathan, N.; Morrison, E.
D.; Geoffroy, G. L.; Geib, S. J .; Rheingold, A. L. Inorg. Chem. 1986,
25, 3100. (d) Einstein, F. W. B.; Pomeroy, R. K.; Willis, A. C. J .
Organomet. Chem. 1986, 311, 257. (e) Lu, C.-Y.; Einstein, F. W. B.;
J ohnston, V. J .; Pomeroy, R. K. Inorg. Chem. 1989, 28, 4212. (f)
Firfiray, D. B.; Irving, A.; Moss, J . R. J . Chem. Soc., Chem. Commun.
1990, 377.
Com p ou n d 3. The two intensity standards showed random
variation ((2%) over the period of data collection. In the final
model, anisotropic thermal parameters were used for all the
non-hydrogen atoms, except the carbonyl carbon atoms, where
isotropic thermal parameters were employed.
Com p ou n d 4. A thin platelike crystal was used in the
study. Data collection was initially carried out in bisecting

1586 Organometallics, Vol. 15, No. 6, 1996
Leong et al.
F igu r e 1. Molecular structure of [(OC)4Os(SnMe2)]2 (1).
F igu r e 2. Molecular structure of [(OC)3Os(SnMe2)]3 (2).
2.726(5) Å,17 but in Os3(SnR2)(CO)10, where R is the
bulky CH(SiMe3)2 substituent, the Os-Sn distances are
in the range 2.727(7)-2.753(7) Å.18 Some exceptionally
long Os-Sn bonds (2.816(1)-2.873(3) Å) have also been
reported.19 The Os-Sn bond lengths in 1 at 2.758(1)
and 2.767(1) Å are therefore longer than normal. The
Os-Sn lengths in the Os2Sn2 unit of Os4(SnMe2)4(CO)14,
described below, are also long.
Ch a r t 1
The axial carbonyls in 1 show a marked leaning
toward the SnMe2 groups: the C(11)-Os(1)-C(13) angle
is 162.8(5)°. We have observed the same leaning in the
crystal structures of related compounds: for example,
argument is somewhat different from those used previ-
ously where the leaning is attributed to interaction of
the π* MO’s on the carbonyls with the filled M-L σ
bonds (where L is a weak π-acceptor ligand).26
The three most common methods of removing a
carbonyl ligand from a complex is by pyrolysis, UV
photolysis, and oxidation to CO2 by Me3NO (or some
other reagent). The use of these three methods to
remove a carbonyl ligand from 1 and a description of
the resulting products is now described.
20
[(OC)4Os(GeMe2)]2 and Os2(SnMe2)2(CO)7(PMe3).21 It
15
is also found in [(OC)4Fe(SnMe2)]2 and mononuclear
22a
derivatives such as cis-Fe(CO)4(SiMe3)2
and cis-Fe-
(CO)4(SnPh3)2,22b but it is not as pronounced as in cis-
Ru(CO)4(GeCl3)2.22c Given this wide occurrence, we
believe this leaning can be attributed to an inherent
electronic effect rather than packing forces.23 The EMe3
(E ) Si, Sn) ligands are known to be strong σ-donor but
poor π-acceptor ligands24 (in much the same way as
PMe3), whereas the corresponding ECl3 groups are
strong π-acceptor ligands.24,25 In pseudooctahedral
complexes with two cis-orientated EMe2 (or EMe3
ligands) there would be buildup of π-electron density
in the region of these ligands. It would therefore be
expected that the axial carbonyls would lean toward
these regions in order to maximize overlap of this
electron density with the appropriate π* molecular
orbitals on the axial carbonyls as shown in Chart 1. This
[(OC)3Os(Sn Me2)]3 (2). Pyrolysis of 1 in hexane in
an evacuated sealed Carius tube at 170 °C for 3 days
afforded [(OC)3Os(SnMe2)]3 (2) in 22% yield; other minor
products in the reaction were not identified (eq 2). The
1
170 °C, 3 days8 [(OC)3Os(SnMe2)]3
(2)
22%
2
structure of 2 (Figure 2) reveals a planar, raftlike Os3-
Sn3 core similar to that found for [(OC)3M(GeMe2)]3 (M
) Ru,27 Os20,28 ); the molecules are constrained by their
crystallographic site symmetry (6h) to be planar. The
structure of 1 may also be compared to those of Os5(µ-
(18) Cardin, C. J .; Cardin, D. J .; Lawless, G. A.; Power, J . M.;
Hursthouse, M. B. J . Organomet. Chem. 1987, 325, 203.
(19) (a) Cardin, C. J .; Cardin, D. J .; Power, J . M.; Hursthouse, M.
B. J . Am. Chem. Soc. 1985, 107, 505. (b) Bartlett, R. A.; Cardin, C. J .;
Cardin, D. J .; Lawless, G. A.; Power, J . M.; Power, P. P. J . Chem. Soc.,
Chem. Commun. 1988, 312.
2b,c
CO)(CO)17
and Os6(CO)17[P(OMe)3]4,29 which also
have planar triangulated metal skeletons. The struc-
ture of Os6(CO)21, to which 2 is an isolobal analogue,
has not been determined but presumably has an Os6
raft nucleus.30
(20) Leong, W. K.; Einstein, F. W. B.; Pomeroy, R. K. Organome-
tallics 1996, 15, 1589.
(21) Leong, W. K.; Einstein, F. W. B.; Pomeroy, R. K. J . Cluster Sci.,
in press.
(26) (a) Berry, A. D.; Corey, E. R.; Hagen, A. P.; MacDiarmid, A.
G.; Saalfield, F. E.; Wayland, B. B. J . Am. Chem. Soc. 1970, 92, 1940.
(b) Aylett, B. J . Prog. Inorg. Radiochem. 1982, 25, 1. (c) Silvestre, J .;
Albright, T. A. Isr. J . Chem. 1983, 23, 139. (d) Alvarez, S.; Ferrer, M.;
Reina, R.; Rossell, O.; Seco, M.; Solans, X. J . Organomet. Chem. 1989,
377, 291.
(27) (a) Howard, J .; Woodward, P. J . Chem. Soc. A 1971, 3648. (b)
Howard, J .; Knox, S. A. R.; Stone, F. G. A.; Woodward, P. J . Chem.
Soc., Chem. Commun. 1970, 1477.
(28) Knox, S. A. R.; Stone, F. G. A. J . Chem. Soc. A 1971, 2874.
(29) Goudsmit, R. J .; J ohnson, B. F. G.; Lewis, J .; Raithby, P. R.;
Whitmire, K. H. J . Chem. Soc., Chem. Commun. 1982, 640.
(30) Goudsmit, R. J .; J effrey, J . G.; J ohnson, B. F. G.; Lewis, J .;
McQueen, R. C. S.; Sanders, A. J .; Liu, J .-C. J . Chem. Soc., Chem.
Commun. 1986, 24.
(22) (a) Vancea, L.; Bennett, M. J .; J ones, C. E.; Smith, R. A.;
Graham, W. A. G. Inorg. Chem. 1977, 16, 897. (b) Pomeroy, R. K.;
Vancea, L.; Calhoun, H. P.; Graham, W. A. G. Inorg. Chem. 1977, 16,
1508. (c) Ball, R.; Bennett, M. J . Inorg. Chem. 1972, 11, 1806.
(23) Zubieta, J . A.; Zuckerman, J . J . Prog. Inorg. Chem. 1978, 24,
251.
(24) (a) Graham, W. A. G. Inorg. Chem. 1968, 7, 315. (b) Lichten-
berger, D. L.; Rai-Chaudhuri, A. J . Am. Chem. Soc. 1991, 113, 2923
and references therein.
(25) (a) Parshall, G. W. J . Am. Chem. Soc. 1966, 88, 704. (b) J etz,
W.; Graham, W. A. G. J . Am. Chem. Soc. 1967, 89, 2773. (c) Willis, A.
C.; van Buuren, G. N.; Pomeroy, R. K.; Einstein, F. W. B. Inorg. Chem.
1983, 22, 1162.

Higher Nuclearity Clusters Containing Os and Sn
Organometallics, Vol. 15, No. 6, 1996 1587
Sch em e 1
F igu r e 3. Molecular structure of Os4(SnMe2)4(CO)14 (3).
The conversion of 1, with its four-membered Os2Sn2
ring, to 2 upon pyrolysis is consistent with the polyhe-
dral skeletal electron pair theory (PSEPT) view that
metal clusters are most stable when comprised of
triangular (rather than square) metal units.31 The
thermal stability of 1 is, however, quite remarkable
when it is compared to the stability of Os4(CO)16 (which
decomposes in solution at room temperature to Os3-
(CO)12).16
The Os-Sn bond lengths in 2 at 2.667(1) and 2.673(1)
Å are within the normal range, mentioned above, for
such bonds. The Os-Os bond lengths (each at 2.974(1)
Å) are long: osmium-osmium distances in open, low-
nuclearity clusters are usually compared to 2.877(3) Å,
the average Os-Os bond length in Os3(CO)12.32 In Os5-
(µ-CO)(CO)17 the metal-metal bond lengths lie in the
range 2.847(1) Å (Os(µ-CO)Os) to 2.892(1) Å,2b whereas
in Os6(CO)17[P(OMe)3]4 the range is 2.834(2)-2.909(2)
Å.29
length of 3.0414(5) Å is exceptionally long for an
unbridged Os-Os bond of a trinuclear fragment (recall
that the average Os-Os distance in Os3(CO)12 is 2.877-
(3) Å).
The formation of 3 from 1 could be envisaged to
proceed via the stannylene derivative (OC)4Os(SnMe2)-
Os(SnMe2)(CO)3 (3i) as shown in Scheme 1. As a
reviewer has pointed out, there must be a cis to trans
rearrangement of the tin ligands about the Os(CO)3 unit
in 3i before dimerization to give 3. The proposed
intermediate 3i may be considered a resonance form of
Os2(SnMe2)(CO)7, the original target molecule analogous
to Os4(CO)15. It is perhaps relevant to mention here
that ethylene readily undergoes reversible dissociation
from Os2(µ-C2H4)(CO)8.34 In other words, 2 + 2 cycload-
ditions can occur readily if one of the moieties is based
on a transition metal. Furthermore, the iron analogue
of 1, [(OC)4Fe(SnMe2)]2, readily yields the stannylene-
like derivatives Fe(CO)4(SnMe2L) (L ) weak Lewis
base),35 and the iron analogue of 3i has been proposed
as an intermediate in the rearrangement of Fe2(SnR2)2-
(µ-CO)(CO)6 compounds.8b
The reaction depicted in eq 3 and Scheme 1 is easily
reversed by treating 3 in solution at 65 °C with 1 atm
of carbon monoxide. We have also found that treatment
of a solution of 3 at room temperature with PMe3 readily
affords Os2(SnMe2)2(CO)7(PMe3), the derivative of 1, in
which one of the equatorial carbonyls has been replaced
by the phosphine.21 Although we have not studied the
substitution of 2 by PMe3, we have found that the
germanium analogue of 2, [Os(CO)3(GeMe2)]3, does not
readily undergo substitution with PMe3 until 120 °C.
Os4(Sn Me2)4(CO)14 (3). The UV irradiation of 1 in
hexane afforded 3 as a yellow precipitate (eq 3). The
hν
1
30‰8 Os4(SnMe2)4(CO)14
(3)
3
precipitation of the product onto the walls of the reaction
vessel eventually prevented efficient passage of UV light
to the reaction solution, and therefore the reaction was
stopped after about 30% conversion of 1 to 3.
The crystal structure of 3 shows (Figure 3) an Os4-
Sn4 skeleton comprised of a rhomboidal Os2Sn2 unit,
with each Os atom part of two outer Os2Sn triangles.
The molecule has a center of symmetry with the eight
metal atoms essentially in a plane (the dihedral angle
between the Os(1)Sn(1)Os(1′)Sn(1′) and Os(1)Os(2)Sn-
(2) planes is 3.5°). The Os-Sn bonds of the metal
triangles are, at 2.678(1) and 2.727(1) Å, similar to the
Os-Sn lengths in 2 which, as mentioned previously, are
in the normal range for Os-Sn lengths reported in the
literature. On the other hand, the Os-Sn bonds of the
rhomboid are significantly longer at 2.760(1) and 2.780(1)
Å and are similar to the corresponding lengths in 1.
Ring strain in homonuclear cage and cluster com-
pounds of Si, Ge, and Sn are significantly less than in
the corresponding C compounds.32 Nevertheless, the
other structural parameters for the Os2Sn triangle in 3
might be taken to indicate ring strain. The Os(1)-Sn-
(1)-Os(2) angle is 68.47(2)°, a major distortion from the
tetrahedral value; the corresponding angle in the Os2-
Sn2 rhomboid is 109.28(2)°. The Os(1)-Os(2) bond
Os4(µ3-O)2(Sn Me2)4(CO)14 (4). When the reaction
of 1 in CH3CN/CH2Cl2 with 2 equiv of Me3NO was
monitored by infrared spectroscopy, it was apparent
that several products were formed. IR absorptions were
seen to grow at different rates, some of which dimin-
ished in intensity as the reaction progressed. The only
product that could be isolated (in ∼10% yield) was Os4-
(µ3-O)2(SnMe2)4(CO)14 (4), as a yellow crystalline solid
(34) (a) Hembre, R. T.; Scott, C. P.; Norton, J . R. J . Am. Chem. Soc.
1987, 109, 3468. (b) Haynes, A.; Poliakoff, M.; Turner, J . J .; Bender,
B. R.; Norton, J . R. J . Organomet. Chem. 1990, 383, 497. (c) Spetseris,
N.; Norton, J . R.; Rithner, C. D. Organometallics 1995, 14, 603.
(35) Marks, T. J .; Newman, A. R. J . Am. Chem. Soc. 1973, 95, 769.
(36) Alcock, N. W.; Pennington, M.; Willey, G. R. J . Chem. Soc.,
Dalton Trans. 1985, 2683.
(31) (a) Wade, K. Adv. Inorg. Chem. Radiochem. 1976, 18, 1. (b)
Mingos, D. M. P. Acc. Chem. Res. 1984, 17, 311. (c) McPartlin, M.
Polyhedron 1984, 3, 1279. (d) Owen, S. M. Polyhedron 1988, 7, 253.
(32) Churchill, M. R.; DeBoer, B. G. Inorg. Chem. 1977, 16, 878.
(33) Sekiguchi, A.; Sakurai, H. Adv. Organomet. Chem. 1995, 37,
1.

1588 Organometallics, Vol. 15, No. 6, 1996
Leong et al.
41
such as Ru4(µ4-PPh)2(µ-CO)(CO)10 and M4(µ4-Bi)2-
(CO)12 (M ) Ru,42 Os43 ) the group 15 atom is essentially
part of the cluster framework as required by PSEPT.
There are, however, molecules where the bonding of the
main-group element is intermediate and consequently
the bonding is ambiguous. Examples of molecules in
this category are Ru4(µ-PPh2)2(CO)1344 and M4(µ3-PPh)-
(CO)1345 (M ) Ru, Os). Some of the clusters of this type,
as in Ru4(µ-PPh2)(CO)13, Ru4(µ-PPh2)4(CO)14,44 and Os4-
(µ3-S)2(CO)12,46 have unusual metal-metal interac-
tions.7
Of the clusters described in this study, we believe,
given its thermal stability, short Os-Sn bonds, and
resemblance to Os6(CO)19, that in cluster 2 the SnMe2
vertices of the deltahedral Os2Sn units are probably best
considered as part of the cluster framework. The
central rhomboidal Os2Sn2 polygon present in 1 and 3
resembles the Os4 skeleton in Os4(CO)16, which, as
mentioned previously, is unstable in solution at room
temperature with respect to Os3(CO)12.16 We therefore
believe that the four-membered Os2Sn2 rings in 1, 3,
and 4 have at best only partial metal cluster character.
This is in agreement with the view of PSEPT that
triangular metal units are more stable than rhomboidal
units.
F igu r e 4. Molecular structure of Os4(µ3-O)2(SnMe2)4(CO)14
(4).
(eq 4).
1 + Me3NO 10%8 Os4(µ3-O)2(SnMe2)4(CO)14 (4)
4
The X-ray crystal structure of 4 reveals the configu-
ration shown in Figure 4. Cluster 4 may be considered
as derived from 3 by the addition of two oxygens atoms
so as to expand the original three- and four-membered
rings into four- and six-membered rings, respectively.
(It has been found that treatment of 3 with Me3NO does
not yield 4 under the same conditions.) In the solid
state, 4 has a crystallographic 2-fold axis that passes
through the center of the Os2Sn2O2 ring. The four-
membered rings are essentially planar; the dihedral
angle between the Os(2)O(1)Sn(1) and Os(2)Os(1)Sn(1)
planes is 1.5°. The central ring, however, has a boat
conformation; the dihedral angle between the Os(2)Sn-
(2)O(1′) and O(1)Os(2)O(1′)Os(2′) planes is 46.4°. The
non-carbonyl oxygen atoms are planar three-coordinate,
and the coordination of the OOsSn2 group is similar to
that of OSn3 units observed previously;23,36 the O-Sn(1)
and O-Sn(2) lengths are 2.049(7) and 2.031(8) Å,
respectively. The Os(1)-Os(2) bond length in 4 at
2.9706(8) Å, although somewhat long for an Os-Os
single bond, is nevertheless significantly shorter than
the Os-Os bond in 3. The Os-Sn lengths in 4 of 2.666-
(1) Å (Os(1)-Sn(1)) and 2.673(1) Å (Os(2)-Sn(2)) are
typical of Os-Sn single bonds. The Os(1)-O(1) distance
of 2.165(7) Å in 4 may be compared to 2.06(2) Å, the
Os-O length in Os4(µ3-O)4(CO)12,37 and 2.06(2) and 2.07-
(2) Å, the corresponding distances in Os6(µ3-O)(µ3-CO)-
(CO)18.38
The structural motifs exhibited by clusters containing
group 8 and group 14 metal atoms are numerous.23,47
The fused-ring systems found in 3 and 4 are, neverthe-
less, unprecedented and further illustrate the structural
diversity of this class of clusters.
Ack n ow led gm en t. We thank the Natural Sciences
and Engineering Research Council of Canada for finan-
cial support. We also thank Professor D. Kepert (Uni-
versity of Western Australia) for useful discussions.
Su p p or tin g In for m a tion Ava ila ble: Tables of hydrogen
atom coordinates and anisotropic temperature factors for 1-4
(8 pages). Ordering information is given on any current
masthead page.
OM950670R
(39) Bruce, M. I.; Liddell, M. J .; Hughes, C. A.; Skelton, B. W.; White,
A. H. J . Organomet. Chem. 1988, 347, 157.
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tallics 1988, 7, 294.
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Trans. 1988, 1315.
(42) Hay, C. M.; J ohnson, B. F. G.; Lewis, J .; Raithby, P. R.; Whitton,
A. J . J . Chem. Soc., Dalton Trans. 1988, 2091.
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Marder, T. B.; Carty, A. J . J . Chem. Soc., Chem. Commun. 1988, 1570.
(b) Corrigan, J . F.; Doherty, S.; Taylor, N. J .; Carty, A. J . Organome-
tallics 1993, 12, 993.
(45) Cherkas, A. A.; Corrigan, J . F.; Doherty, S.; MacLaughlin, S.
A.; van Gastel, F.; Taylor, N. J .; Carty, A. J . Inorg. Chem. 1993, 32,
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A.; Errington, R. J .; Norman, N. C. Adv. Organomet. Chem. 1990, 31,
91.
Con clu sion s. In transition-metal carbonyl cluster
compounds containing main-group elements (i.e., other
than CO), the question arises as to whether the main-
group element is best considered as part of a simple
ligand or whether it is an essential part of the metal
cluster framework. For example, in compounds such
as Os3(CO)11(PR3)39 and Os4(CO)13(PMe3)40 the phos-
phine is acting as a simple ligand, whereas in clusters
(37) Bright, D. J . Chem. Soc. D 1970, 1169.
(38) Goudsmit, R. J .; J ohnson, B. F. G.; Lewis, J .; Raithby, P. R.;
Whitmire, K. H. J . Chem. Soc., Chem. Commun. 1983, 246.