Metallacyclic complexes with ortho-silylated triphenylphosphine ligands, LnOs(κ2(Si,P)-SiMe2C6H 4PPh2), derived from thermal reactions of the coordinatively unsaturated trimethylsilyl, methyl complex, Os(SiMe 3)(Me)(CO)(PPh3)2

Article abstract of DOI:10.1016/j.jorganchem.2005.03.063

Reaction between Os(SiCl₃)Cl(CO)(PPh₃)₂ and five equivalents of MeLi produces a colourless intermediate, tentatively formulated as the lithium salt of the six-coordinate, dimethyl, trimethylsilyl-containing complex anion, Li[Os(SiMe₃)(Me) ₂(CO)(PPh₃)₂]. Reaction of this material with ethanol releases methane and gives the red, coordinatively unsaturated methyl, trimethylsilyl-containing complex, Os(SiMe₃)(Me)(CO)(PPh ₃)₂ (1). An alternative synthesis of 1 is to add one equivalent of MeLi to Os(SiMe₃)Cl(CO)(PPh₃)₂, which in turn is obtained by adding three equivalents of MeLi to Os(SiCl ₃)Cl(CO)(PPh₃)₂. Treatment of 1 with p-tolyl lithium, again gives a colourless intermediate which may be Li[Os(SiMe ₃)(Me)(p-tolyl)(CO)(PPh₃)₂], and reaction with ethanol gives the red complex, Os(SiMe₃)(p-tolyl)(CO)(PPh ₃)₂ (3). Complexes 1 and 3 are readily carbonylated to Os(SiMe₃)(Me)(CO)₂(PPh₃)₂ (2) and Os(SiMe₃)(p-tolyl)(CO)₂(PPh₃)₂ (4), respectively. Heating Os(SiMe₃)Cl(CO)(PPh₃)₂ in molten triphenylphosphine results only in loss of the trimethylsilyl ligand and formation of the previously known complex containing an ortho-metallated triphenylphosphine ligand, Os(κ²(C,P)-C₆H ₄PPh₂)Cl(CO)(PPh₃)₂. In contrast, heating the five-coordinate osmium-methyl complex, Os(SiMe₃)(Me)(CO) (PPh₃)₂ (1), in the presence of triphenylphosphine results mainly, not in tetramethylsilane elimination, but in ortho-silylation as well as ortho-metallation of different triphenylphosphine ligands giving, Os(κ²(Si,P)-SiMe₂C₆H₄PPh ₂)(κ²(C,P)-C₆H₄PPh ₂)(CO)(PPh₃) (5). A byproduct of this reaction is the non-silicon containing di-ortho-metallated complex, Os(κ²(C,P)- C₆H₄PPh₂)₂(CO)(PPh₃) (6). A similar reaction occurs when Os(SiMe₃)(Me)(CO)(PPh ₃)₂ (1) is heated in the presence of tri(N-pyrrolyl) phosphine producing Os(κ²(Si,P)-SiMe₂C ₆H₄PPh₂)(κ²(C,P)-C ₆H₄PPh₂)(CO)[P(NC₄H ₄)₃] (7) but a better synthesis of 7 is to treat 5 directly with tri(N-pyrrolyl)phosphine. Heating the six-coordinate complex, Os(SiMe₃)(Me)(CO)₂(PPh₃)₂ (2), gives two complexes both containing ortho-metallated triphenylphosphine, one with loss of the trimethylsilyl ligand, giving the known complex, Os(κ²(C,P)-C₆H₄PPh₂)H(CO) ₂(PPh₃), and the other with retention of the trimethylsilyl ligand, giving Os(SiMe₃)(κ²(C,P)- C₆H₄PPh₂)(CO)₂(PPh₃) (8). Crystal structure determinations for 5, 6, 7 and 8 have been obtained.

Full text of DOI:10.1016/j.jorganchem.2005.03.063

Journal of Organometallic Chemistry 690 (2005) 3309–3320
www.elsevier.com/locate/jorganchem
Metallacyclic complexes with ortho-silylated
triphenylphosphine ligands, LnOs(j2(Si,P)-SiMe2C6H4PPh2),
derived from thermal reactions of the coordinatively unsaturated
trimethylsilyl, methyl complex, Os(SiMe3)(Me)(CO)(PPh3)2
*
George R. Clark, Guo-Liang Lu, Clifton E.F. Rickard, Warren R. Roper ,
L. James Wright
*
Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand
Received 24 February 2005; accepted 25 March 2005
Available online 3 June 2005
Abstract
Reaction between Os(SiCl3)Cl(CO)(PPh3)2 and five equivalents of MeLi produces a colourless intermediate, tentatively formu-
lated as the lithium salt of the six-coordinate, dimethyl, trimethylsilyl-containing complex anion, Li[Os(SiMe3)(Me)2(CO)(PPh3)2].
Reaction of this material with ethanol releases methane and gives the red, coordinatively unsaturated methyl, trimethylsilyl-contain-
ing complex, Os(SiMe3)(Me)(CO)(PPh3)2 (1). An alternative synthesis of 1 is to add one equivalent of MeLi to Os(SiMe3)Cl
(CO)(PPh3)2, which in turn is obtained by adding three equivalents of MeLi to Os(SiCl3)Cl(CO)(PPh3)2. Treatment of 1 with p-tolyl
lithium, again gives a colourless intermediate which may be Li[Os(SiMe3)(Me)(p-tolyl)(CO)(PPh3)2], and reaction with ethanol gives
the red complex, Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3). Complexes 1 and 3 are readily carbonylated to Os(SiMe3)(Me)(CO)2(PPh3)2 (2)
and Os(SiMe3)(p-tolyl)(CO)2(PPh3)2 (4), respectively. Heating Os(SiMe3)Cl(CO)(PPh3)2 in molten triphenylphosphine results only
in loss of the trimethylsilyl ligand and formation of the previously known complex containing an ortho-metallated triphenylphos-
phine ligand, Os(j2(C,P)-C6H4PPh2)Cl(CO)(PPh3)2. In contrast, heating the five-coordinate osmium-methyl complex, Os(SiMe3)
(Me)(CO)(PPh3)2 (1), in the presence of triphenylphosphine results mainly, not in tetramethylsilane elimination, but in ortho-sily-
lation as well as ortho-metallation of different triphenylphosphine ligands giving, Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-
C6H4PPh2)(CO)(PPh3) (5). A byproduct of this reaction is the non-silicon containing di-ortho-metallated complex, Os(j2(C,P)-
C6H4PPh2)2(CO)(PPh3) (6). A similar reaction occurs when Os(SiMe3)(Me)(CO)(PPh3)2 (1) is heated in the presence of tri(N-pyrr-
olyl)phosphine producing Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)[P(NC4H4)3] (7) but a better synthesis of 7 is to
treat 5 directly with tri(N-pyrrolyl)phosphine. Heating the six-coordinate complex, Os(SiMe3)(Me)(CO)2(PPh3)2 (2), gives two com-
plexes both containing ortho-metallated triphenylphosphine, one with loss of the trimethylsilyl ligand, giving the known complex,
Os(j2(C,P)-C6H4PPh2)H(CO)2(PPh3), and the other with retention of the trimethylsilyl ligand, giving Os(SiMe3)(j2(C,P)-
C6H4PPh2)(CO)2(PPh3) (8). Crystal structure determinations for 5, 6, 7 and 8 have been obtained.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Metallacyclic complex; ortho-Silylation; ortho-Metallation; Osmium; Silyl complexes; Methyl complexes; X-ray crystal structure
1. Introduction
C–Si bond formation, from reductive elimination of
adjacent alkyl and silyl ligands in an alkyl, silyl-metal
species, is widely postulated as one of two likely prod-
*
Corresponding authors. Tel.: + 64 9 373 7999x8320; fax: + 64 9 373
7422.
E-mail address: w.roper@auckland.ac.nz (W.R. Roper).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.03.063

3310
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
PPh3
PPh3
Os
uct-forming steps in metal-catalyzed hydrosilation [1].
There have been studies of this process, both theoretical
[2] and experimental, using isolable alkyl, silyl–platinum
[3] and alkyl, silyl–palladium [4] complexes. Fewer stud-
ies have been made with octahedral metal complexes,
but important results include the observation that elim-
ination of tetramethylsilane from cis-Fe(SiMe3)(Me)-
(CO)4 was facile [5] and the demonstration that C–H
and C–Si reductive elimination could be competitive
for an iridium(III) complex containing hydride, alkyl,
and silyl ligands [6]. We have previously shown that
the coordinatively unsaturated silyl, aryl osmium(II)
complexes, Os[Si(OEt)3](Aryl)(CO)(PPh3)2 (Aryl = Ph,
o-tolyl) are resistant to C–Si reductive elimination even
at elevated temperatures [7]. This is no doubt in part be-
cause of the strong Os–Si bond in these complexes which
is attributable to the electron-withdrawing ethoxy sub-
stituents on the silyl ligand [8]. To determine whether
or not, related five-coordinate compounds bearing the
more weakly-bound trimethylsilyl ligand would undergo
C–Si reductive elimination more readily we set out to
prepare and examine the thermal reactions of complexes
of the type Os(SiMe3)(R)(CO)(PPh3)2. In this paper, we
describe. (i) the reaction between Os(SiCl3)Cl(CO)-
(PPh3)2 and MeLi to give Os(SiMe3)(Me)(CO)(PPh3)2
(1); (ii) the conversion of 1, through reaction with p-tol-
ylLi, to Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3); (iii) the car-
bonylation of 1 and 3 to Os(SiMe3)(Me)(CO)2(PPh3)2
(2) and Os(SiMe3)(p-tolyl)(CO)2(PPh3)2 (4), respectively;
(iv) the thermal reaction of Os(SiMe3)(Me)(CO)(PPh3)2
(1) in the presence of PPh3 to give Os(j2(Si,P)-Si-
Me2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)(PPh3) (5) and
Os(j2(C,P)-C6H4PPh2)2(CO)(PPh3) (6); (v) the thermal
reaction of Os(SiMe3)(Me)(CO)(PPh3)2 (1) in the pres-
ence of P(NC4H4)3 to give Os(j2(Si,P)-SiMe2C6H4PPh2)-
(j2(C,P)-C6H4PPh2)(CO)[P(NC4H4)3] (7); (vi) the
thermal reaction of Os(SiMe3)(Me)(CO)2(PPh3)2 (2)
to give Os(j2(C,P)-C6H4PPh2)H(CO)2(PPh3), and Os-
(SiMe3) (j2(C,P)-C6H4PPh2)(CO)2(PPh3) (8); and (vii)
the crystal structures of 5, 6, 7, and 8.
CO
CO
3 MeLi
Os
Cl
SiCl3
Cl
SiMe3
PPh3
PPh3
1. 5 MeLi
1. 5 MeLi
2. EtOH
3. CO
2. EtOH
CO
MeLi
PPh3
PPh3
CO
CO
SiMe3
OC
Os
Os
Me
SiMe3
Me
PPh3
(2)
PPh3
(1)
1. p-tolylLi
2. EtOH
3. CO
1. p-tolylLi
2. EtOH
PPh3
PPh3
Os
CO
CO
SiMe3
OC
CO
Os
p-tolyl
SiMe3
p-tolyl
PPh3
(3)
PPh3
(4)
Scheme 1. Syntheses of Os(SiMe3)(Me)(CO)(PPh3)2 (1), Os(SiMe3)-
(Me)(CO)2(PPh3)2 (2), Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3), and
Os(SiMe3)(p-tolyl)(CO)2(PPh3)2 (4).
formation of a white precipitate. This precipitate could
not be fully characterized because of its extreme sensitiv-
ity to moisture and other protic solvents, but it was pos-
sible to record an IR spectrum as a Nujol mull. This
revealed a m(CO) band at 1754 cmꢀ1. This extremely
low m(CO) is indicative of an anionic species and accord-
ingly we formulate the white material as the lithium salt,
Li[Os(SiMe3)(Me)2(CO)(PPh3)2] where the osmium cen-
tre is coordinatively saturated and therefore colourless.
This formulation is further supported by reactions de-
picted in Schemes 1 and 2. Thus, addition of ethanol
to the white precipitate brings about dissolution with re-
lease of methane and the formation of a red solution
from which can be isolated the red crystalline solid Os-
(SiMe3)(Me)(CO)(PPh3)2 (1) in good yield (see Schemes
1 and 2). Complex 1 is stable in the solid state but slowly
decomposes over several hours when in solution.
Among the decomposition products is the hydride,
OsHCl(CO)(PPh3)3. Spectral data for 1 and all other
new compounds are collected in Section 4. Compound
1 has m(CO) at 1879 cmꢀ1 (in CH2Cl2), significantly
lower than m(CO) for the precursor Os(SiMe3)Cl
(CO)(PPh3)2, at 1895 cmꢀ1 (in CH2Cl2), as expected.
2. Results and discussion
2.1. Preparation of Os(SiMe3)(Me)(CO)(PPh3)2 (1)
and Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3)
1
We have previously reported that addition of three
equivalents of MeLi to Os(SiCl3)Cl(CO)(PPh3)2 results
in the formation of Os(SiMe3)Cl(CO)(PPh3)2 [8] (see
Scheme 1). Since the Os–Cl bond in five coordinate com-
plexes of this type is labile, it seemed likely that reaction
with excess MeLi would afford Os(SiMe3)(Me)-
(CO)(PPh3)2. In fact, addition of five equivalents of
MeLi to Os(SiCl3)Cl(CO)(PPh3)2 turned the originally
yellow solution first red and then colourless with the
In the H NMR spectrum the Os–Me signal is observed
at 0.12 ppm as a triplet (3JPH = 8.7 Hz). The corre-
sponding 13C resonance is observed at 21.1 ppm as a
triplet (2JPC = 9.6 Hz) and the resonance for the trimeth-
ylsilyl group is at 9.6 ppm. In the 31P NMR spectrum
there is a singlet resonance at 29.19 ppm. All these data
are compatible with the pyramidal geometry shown for
1 in Scheme 1, i.e., mutually trans triphenylphosphine
ligands and with a vacant site trans to the trimethylsilyl

G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
3311
Os(SiMe3)(Me)(CO)(PPh3)2 (1) and Os(SiMe3)(p-tolyl)-
(CO)(PPh3)2 (3) brings about rapid discharge of the
red colour and formation of the colourless, coordin-
atively saturated, complexes Os(SiMe3)(Me)(CO)2-
(PPh3)2 (2) and Os(SiMe3)(p-tolyl)(CO)2(PPh3)2 (4),
respectively, in high yield. Experimentally, it is more
convenient to add CO to red solutions of 1 and 3, pre-
pared in situ, avoiding isolation of the five coordinate
compounds. Compound 2 has limited solution stability
and attempts to grow a single crystal from CH2Cl2 over
several days resulted in the formation of OsCl2-
(CO)2(PPh3)2. The IR spectra of both 2 and 4 show
two m(CO) bands consistent with a cis arrangement of
*
-
PPh3
Os
PPh3
Os
Me
Me
CO
SiMe3
CO
5 MeLi
Cl
SiCl3
PPh3
colourless
PPh3
yellow
EtOH
-MeH
*
-
PPh3
PPh3
Os
p-tolylLi
Me
CO
SiMe3
p-tolyl
Me
CO
Os
SiMe3
PPh3
(1)
red
PPh3
colourless
1
the CO ligands. The H and 13C NMR spectra require
no special comment, all the data being consistent with
the structures depicted in Scheme 1. The 31P NMR spec-
tra show singlet signals with chemical shifts at 4.34 ppm
for 2, ꢀ4.16 ppm for 4, both significantly upfield from
the values observed for the five coordinate precursors
(29.59 ppm for 1, 22.31 ppm for 3).
EtOH -MeH
PPh3
CO
Os
p-tolyl
SiMe3
PPh3
(3)
red
2.3. Thermal reactions of Os(SiMe3)Cl(CO)(PPh3)2
and Os(SiMe3)(Me)(CO)(PPh3)2 (1) and the crystal
structures of Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-
C6H4PPh2)(CO)(PPh3) (5) Os(j2(C,P)-C6H4PPh2)2-
(CO)(PPh3) (6) and Os(j2(Si,P)-SiMe2C6H4PPh2)-
(j2(C,P)-C6H4PPh2)(CO)[P(NC4H4)3] (7)
Scheme 2. Formation of 1 and 3 via postulated anionic intermediates
(compounds marked with an asterisk not fully characterised).
ligand. This same geometry has been verified crystallo-
graphically for numerous other five coordinate silyl
derivatives of osmium(II) [7,8].
Before describing the thermal reactions of the silyl,
methyl-complex, Os(SiMe3)(Me)(CO)(PPh3)2 (1), it is
relevant to consider the thermal reaction of the silyl,
chloride-complex, Os(SiMe3)Cl(CO)(PPh3)2. This is a
very stable compound and it is only after heating in
molten triphenylphosphine at 160 ꢁC for 2 h that
decomposition occurs, the major products being the
ortho-metallated complex, Os(j2(C,P)-C6H4PPh2)Cl-
(CO)(PPh3)2 and OsHCl(CO)(PPh3)3, both products
involving loss of the silyl ligand (see Scheme 3).
Os(j2(C,P)-C6H4PPh2)Cl(CO)(PPh3)2 has been de-
scribed previously as a product from transmetallation
utilising Hg(C6H4PPh2)2 [9].
In marked contrast to the stability of the silyl,
chloride-complex, Os(SiMe3)Cl(CO)(PPh3)2 described
above, the corresponding silyl, methyl-complex,
Os(SiMe3)(Me)(CO)(PPh3)2 (1), shows solution instabil-
ity and as depicted in Scheme 4 readily undergoes a ther-
mal reaction (toluene reflux, 1 h) in the presence of
The red colour of a solution of complex 1 is immedi-
ately discharged by the addition of one or more equiva-
lents of p-tolylLi suggesting that the saturated anion,
[Os(SiMe3)(Me)(p-tolyl)(CO)(PPh3)2]ꢀ, is formed (see
Scheme 2). When ethanol is added to this colourless
solution methane is liberated, the solution becomes red
in colour and the p-tolyl analogue of 1, Os(SiMe3)(p-to-
lyl)(CO)(PPh3)2 (3) can be isolated as a red crystalline
solid. This is stable as a solid but like 1, shows solution
instability. It is interesting, that in the formation of 3
through protonolysis of the postulated anion, it is meth-
ane which is eliminated rather than toluene. The IR
spectrum of 3 shows m(CO) at 1900 cmꢀ1. In the 13C
NMR spectrum the resonance for the trimethylsilyl
group is seen as a triplet at 9.2 ppm (3JPC = 1.9 Hz). In
the 31P NMR spectrum there is a singlet resonance at
22.31 ppm. The geometry depicted for complex 3 in
Schemes 1 and 2 is based upon the known geometry of
other related tolyl, silyl-complexes of osmium(II) [7].
2.2. Carbonylation of Os(SiMe3)(Me)(CO)(PPh3)2
(1) and Os(SiMe3)(p-tolyl)(CO)(PPh3)2 (3) to
Os(SiMe3)(Me)(CO)2(PPh3)2 (2) and Os(SiMe3)-
(p-tolyl)(CO)2(PPh3)2 (4), respectively
Ph2P
PPh3
Os
molten PPh3,
160˚C, 2 hr.
OC
CO
Os
Ph3P
Cl
Cl
SiMe3
PPh3
PPh3
+ OsHCl(CO)(PPh3)3
Like other five coordinate silyl-osmium(II)
complexes, direct admission of CO to red solutions of
Scheme 3. Thermal reaction of Os(SiMe3)Cl(CO)(PPh3)2.

3312
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
c
carbon atom of the carbonyl ligand appears as a multi-
Ph2P
plet at 192.6 ppm, consistent with coupling to three
inequivalent phosphorus atoms. In the 31P NMR spec-
trum, each of the phosphorus atoms appears as a dou-
blet of doublets due to P–P coupling. The assignments
and the accompanying coupling constants are presented
in Section 4.6. The assignment of phosphorus atom (b)
(see Scheme for phosphorus atom labeling) follows from
coupling constants indicative of two cis phosphorus
atoms. Distinction between phosphorus atoms (a) and
(c), which both have one cis and one trans phosphorus
atom, was made on the basis of the distinctly high-field
chemical shift that is typically observed for ortho-metal-
lated triphenylphosphine ligands (see Ref. [9] and the
compounds 6, 7, and 8 described below).
Os
b
CO
Ph2P
a
PPh3
(6)
+
c
PPh3
toluene
reflux, 1 hr.
Ph2P
PPh3
Os
b
Ph3P
CO
Os
Me
Me
OC
Si
Me
SiMe3
a
Ph2P
PPh3
(1)
(5)
P(C4H4N)3
P(C4H4N)3
toluene
reflux, 1 hr.
Although some structural data for complex 5 have
been reported in reference [10] complete X-ray structure
determination for 5 is reported here to provide accurate
bond length data for comparison with the other struc-
ture determinations in this paper. Crystallographic data
for 5 and the other structures reported in this paper are
given in Table 1. The molecular structure of 5 is depicted
in Fig. 1 and selected bond lengths and angles for 5 are
presented in Table 2. The overall geometry about os-
mium is octahedral with the phosphorus atoms of the
two chelating ligands located mutually trans. The triphe-
nylphosphine ligand is trans to the silyl ligand. The lon-
c
Ph2P
b
(C4H4N)3P
Os
Me
Me
OC
Si
a
Ph2P
(7)
Scheme 4. Thermal reactions of Os(SiMe3)(Me)(CO)(PPh3)2 (1) (with
phosphorus atoms labeled for NMR discussion).
triphenylphosphine, to give as major product, the ortho-
silylated as well as ortho-metallated complex, Os(j2-
(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)(PPh3)
(5). This unusual product, which retains the Os–Si bond,
has been observed previously from the reaction of
OsHCl(CO)(PPh3)3 and Hg(SiMe3)2 [10]. The same
ortho-silylated ligand, j2(Si,P)-SiMe2C6H4PPh2, is
formed in the thermal reaction of a base-stabilised silyl-
ene, triphenylphosphine complex of ruthenium(II) [11].
This suggests the possibility of a dimethylsilylene inter-
mediate in the formation of complex 5. Such an interme-
diate could arise from a migration of a methyl group
from the trimethylsilyl ligand to osmium. There is prec-
edent for this sort of process on osmium in that a methyl
group has been observed to migrate to osmium from a
bound trimethylstannyl ligand [12]. However, the details
of the mechanism are unknown and the reaction must be
of some complexity since an ortho-metallated triphenyl-
phosphine ligand is also formed. The focus of this study
was to identify the metal complexes formed rather than
the mechanism of their formation and in view of the
complexity of this reaction, and the vigorous reaction
conditions involved, no effort was made to detect and
identify any gaseous by-products. In the IR spectrum
˚
gest of the three Os–P distances is Os–P(1), 2.4363(11) A
which is expected since P(1) is trans to Si. Os–P(3),
˚
2.3499(12) A, which is part of the unstrained five mem-
bered chelate ring is significantly shorter than Os–P(2),
˚
2.3812(12) A, which is part of the strained four mem-
bered chelate ring. All these Os–P distances are closely
similar to values reported for other related osmium
ortho-metallated complexes [9]. The Os–Si distance is
2.4716(13) A. The average for 10 entries for octahedral
osmium silyl complexes in the Cambridge Crystallo-
˚
˚
graphic Data Base is 2.4499 (SD, 0.0508) A. The Os–
C(52) distance within the four-membered ring is
˚
2.190(5) A.
A minor product from the thermal reaction of the si-
lyl, methyl-complex, Os(SiMe3)(Me)(CO)(PPh3)2 (1) in
the presence of triphenylphosphine does involve loss of
the trimethylsilyl ligand and the methyl ligand giving
eventually Os(j2(C,P)-C6H4PPh2)2(CO)(PPh3) (6) which
contains two ortho-metallated triphenylphosphine li-
gands (see Scheme 4). The IR spectrum of 6 shows
m(CO) at 1888 cmꢀ1. There are no features requiring spe-
cial comment in either the H NMR or the 13C NMR
1
spectra of 6 but the 31P NMR spectrum is interesting.
As for complex 5, there are three inequivalent phospho-
rus atoms in a meridional arrangement and the signal
for each phosphorus appears as a doublet of doublets
due to P–P coupling. The assignments and the accompa-
nying coupling constants are presented in Section 4.7.
The assignment of phosphorus atom (a) follows from
1
of 5, there is a m(CO) at 1906 cmꢀ1. In the H NMR
spectrum, the two methyl groups of the j2(Si,P)-Si-
Me2C6H4PPh2 ligand show separate resonances at
ꢀ1.12 and 0.12 ppm. Likewise, in the 13C NMR
spectrum, the two carbon atoms of these methyl groups
also show separate resonances at ꢀ2.3 and 5.2 ppm. The

G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
3313
Table 1
Data collection and processing parameters for 5, 6, 7 and 8
5 Æ 2H2O
6 Æ 0.5C6H14
7
8
Formula
C
57H49O3OsP3Si
C58H50OOsP3
1046.09
Triclinic
C51H46N3OOsP3Si
1028.11
C41H38O2OsP2Si
842.94
Molecular weight
Crystal system
Space group
1093.16
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/c
ꢀ
P1
Unit cell dimensions
˚
a (A)
˚
11.5539(1)
19.5272(2)
22.7764(1)
90.0
10.7694(2)
12.1558(2)
18.8593(3)
75.886(1)
87.315(1)
69.919(1)
2246.95(7)
84
9.6783(1)
20.6293(1)
22.2438(3)
90.0
10.2287(1)
15.3207(1)
23.3242(2)
90.0
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90.975(1)
90.0
95.610(1)
90.0
96.263(1)
90.0
3
˚
V (A )
5137.96(7)
84
4419.85(8)
150
3633.34(5)
150
T (K)
Z
4
1.413
2
1.546
4
1.545
4
1.541
Dcalc (g cmꢀ3
F(000)
)
2200
2.64
1054
2.99
2064
3.06
1680
3.66
l (mmꢀ1
)
Crystal size (mm)
2h (Min–max) (ꢁ)
Reflections collected
Independent reflections (Rint
Tmin,Tmax
0.46 · 0.15 · 0.04
2.0–27.2
50963
0.32 · 0.30 · 0.22
1.8–26.5
22087
0.36 · 0.22 · 0.20
1.4–25.7
39948
0.24 · 0.22 · 0.16
1.6–25.7
33266
)
11,300 (0.0253)
0.376, 0.902
1.092
9198 (0.0235)
0.448, 0.559
1.061
8389 (0.0253)
0.405, 0.579
1.118
6916 (0.0292)
0.473, 0.592
1.073
Goodness of fit on F2
R (observed data)
R1 = 0.0364
wR2 = 0.1023
R1 = 0.0463
wR2 = 0.1078
R1 = 0.0365,
wR2 = 0.0932
R1 = 0.0437
wR2 = 0.0976
R1 = 0.0230
wR2 = 0.0537
R1 = 0.0271
wR2 = 0.0558
R1 = 0.0192
wR2 = 0.0409
R1 = 0.0247
wR2 = 0.0429
R(all data)
R = RiFoj ꢀ jFci/RjFoj.
2
2
1=2
wR2 ¼ fR½wðF 2o ꢀ F c2Þ ꢁ=R½wðF 2oÞ ꢁg
.
P–P coupling constants indicative of one cis and one
trans phosphorus atom together with a chemical shift
position appropriate for a PPh3 ligand. The phosphorus
atoms of the two ortho-metallated triphenylphosphine li-
gands appear at unusually high-field positions (see dis-
cussion for complex 5) and are distinguished by (b)
having P–P coupling constants appropriate for two cis
phosphorus atoms and by (c) having P–P coupling con-
stants appropriate for one cis and one trans P atoms.
The molecular structure of 6 is depicted in Fig. 2 and
selected bond lengths and angles for 6 are presented
in Table 3. The overall geometry about osmium is
octahedral with the phosphorus atoms of the two
ortho-metallated ligands located mutually cis. The tri-
phenylphosphine ligand is trans to a phosphorus atom
of one of the ortho-metallated ligands. The Os–P dis-
tances in the ortho-metallated ligands (Os–P(1),
˚
2.3786(10) and Os–P(2), 2.3871(11) A) are almost identi-
cal despite one being trans to carbon and the other trans
to phosphorus. The Os–PPh3 distance is slightly shorter
˚
at 2.3454(11) A. The Os–C distances within the four-
membered rings are Os–C(32), 2.133(4) and Os–C(2),
˚
2.149(4) A, are both shorter than the corresponding dis-
˚
tance in 5 (2.190(5) A).
When Os(SiMe3)(Me)(CO)(PPh3)2 (1), undergoes a
thermal reaction (toluene reflux, 1 h) in the presence
of tris(N-pyrrolyl)phosphine instead of triphenylphos-
phine, the tris(N-pyrrolyl)phosphine analogue of 5,
Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)-
Fig. 1. Molecular geometry of Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-
C6H4PPh2)(CO)(PPh3) (5).

3314
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
Table 2
Table 3
˚
˚
Selected bond lengths (A) and angles (ꢁ) for 5
Selected bond lengths (A) and angles (ꢁ) for 6
Bond lengths
Os–Si
Os–P(1)
Bond lengths
Os–P(1)
Os–P(2)
2.4716(13)
2.4363(11)
2.3812(12)
2.3499(12)
1.883(5)
2.3786(10)
2.3871(11)
2.3454(11)
1.897(4)
2.149(4)
2.133(4)
1.816(4)
1.406(6)
1.799(4)
1.401(6)
Os–P(2)
Os–P(3)
Os–P(3)
Os–C
Os–C(2)
Os–C(1)
Os–C(52)
Si–C(2)
2.190(5)
1.886(6)
Os–C(32)
P(1)–C(1)
C(1)–C(2)
P(2)–C(31)
C(31)–C(32)
Si–C(3)
1.891(6)
1.913(5)
Si–C(72)
P(2)–C(51)
C(51)–C(52)
1.801(5)
1.420(7)
Bond angles
Bond angles
P(1)–Os–P(2)
P(1)–Os–P(3)
P(1)–Os–C
100.58(4)
98.09(4)
Si–Os–P(1)
Si–Os–P(2)
178.02(4)
88.92(4)
78.94(4)
101.73(12)
66.47(12)
156.65(12)
158.65(4)
91.86(13)
88.06(12)
66.13(12)
94.41(13)
89.97(12)
92.76(12)
100.4(3)
Si–Os–P(3)
Si–Os–C(1)
P(1)–Os–C(2)
P(1)–Os–C(32)
P(2)–Os–P(3)
P(2)–Os–C
87.83(15)
77.59(12)
92.56(4)
Si–Os–C(52)
P1–Os–P(2)
P1–Os–P(3)
100.03(4)
159.13(4)
66.01(12)
87.14(16)
103.01(16)
105.6(3)
P(2)–Os–C(2)
P(2)–Os–C(32)
P(3)–Os–C
P(2)–Os–P(3)
P(2)–Os–C(52)
Os–P(2)–C(51)
Os–Si–C(72)
Os–C(52)–C(51)
Os–P(3)–C(71)
P(3)–C(71)–C(72)
Si–C(72)–C(71)
P(3)–Os–C(2)
P(3)–Os–C(32)
P(1)–C(1)–C(2)
Os–C(2)–C(1)
P(2)–C(31)–C(32)
Os–C(32)–C(31)
Os–P(2)–C(31)
Os–P(1)–C(1)
109.79(17)
115.3(4)
117.5(4)
107.0(3)
100.6(3)
107.2(3)
85.64(15)
86.04(14)
[P(NC4H4)3] (7), can be detected amongst numerous
uncharacterised products (see Scheme 4). A clean high-
yield preparation of 7 involves direct replacement of
triphenylphosphine in 5 by reaction with tris(N-pyrr-
olyl)phosphine. The IR spectrum of 7 shows m(CO) at
1941 cmꢀ1, a value markedly higher than observed for
5, consistent with the introduction of a very good p-
acceptor ligand (tris(N-pyrrolyl)phosphine) [13]. In the
1H NMR spectrum the two methyl groups of the
j2(Si,P)-SiMe2C6H4PPh2 ligand again show separate
resonances at ꢀ1.15 and 0.13 ppm. Likewise, in the
13C NMR spectrum, the two carbon atoms of these
methyl groups also show separate resonances at ꢀ2.3
and 5.3 ppm. The carbon atom of the carbonyl ligand
appears as a multiplet at 190.1 ppm, consistent with cou-
pling to three inequivalent phosphorus atoms. All these
chemical shifts are close to those observed for complex
5. In the 31P NMR spectrum each of the phosphorus
atoms appears as a doublet of doublets due to P–P cou-
pling. The assignments and the accompanying coupling
constants are presented in Section 4.8. The assignment
of phosphorus atom (b) (P(NC4H4)3) follows from the
very low-field chemical shift (70.15 ppm) [13b] and cou-
pling constants indicative of two cis phosphorus atoms.
Distinction between phosphorus atoms (a) and (c),
which both have a cis and a trans phosphorus atom,
was made on the basis of the distinctly high-field chem-
ical shift that is typically observed for ortho-metallated
triphenylphosphine ligands.
The molecular structure of 7 is depicted in Fig. 3 and
selected bond lengths and angles for 7 are presented in
Table 4. The overall geometry of 7 is the same as that
for 5 with tris(N-pyrrolyl)phosphine replacing triphenyl-
Fig. 2. Molecular geometry of Os(j2(C,P)-C6H4PPh2)2(CO)(PPh3) (6).

G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
3315
˚
phosphine. The Os–P(NC4H4)3 distance is 2.3169(7) A
and this can be compared with the Os–PPh3 distance
˚
in 5 of 2.4363(11) A. This pronounced shortening of
the Os–P bond for the tris(N-pyrrolyl)phosphine ligand
has been observed previously and attributed to the
strong p-accepting capability of this ligand [13]. Accom-
panying this shortening of the Os–P bond is a marked
lengthening of the Os–Si bond in the trans position. In
˚
7 the Os–Si distance is 2.5110(8) A which can be com-
˚
pared with the value for 5 which is 2.4716(13) A.
˚
2.5110(8) A is longer than any recorded Os–Si distance
for an octahedral osmium silyl complex (the average
for 10 entries in the Cambridge Crystallographic Data
˚
Base is 2.4499 (SD, 0.0508) A). The Os–C(72) distance
˚
within the four-membered ring is 2.179(3) A, close to
the corresponding value in 5.
2.4. Thermal reaction of Os(SiMe3)(Me)(CO)2(PPh3)2
(2) and the crystal structure of Os(SiMe3)(j2(C, P)-
C6H4PPh2)(CO)2(PPh3) (8)
Fig. 3. Molecular geometry of Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-
C6H4PPh2)(CO)[P(NC4H4)3] (7).
For comparison with the thermal reactions of the
coordinatively unsaturated Os(SiMe3)(Me)(CO)(PPh3)2
(1) described above the coordinatively saturated dicar-
bonyl complex, Os(SiMe3)(Me)(CO)2(PPh3)2 (2) was
heated under reflux in toluene. Two products were iso-
lated from this reaction after chromatography, the ma-
jor one being Os(SiMe3)(j2(C,P)-C6H4PPh2)(CO)2
(PPh3) (8) (see Scheme 5). Complex 8 retains the
trimethylsilyl ligand and incorporates an ortho-metal-
lated triphenylphosphine. The minor product is
Os(j2(C,P)-C6H4PPh2)H(CO)2(PPh3), with loss of both
the trimethylsilyl and methyl ligands. Os(j2(C,P)-
C6H4PPh2)H(CO)2(PPh3) has also been reported from
the thermal reactions of Os(g2-CH2O)(CO)2(PPh3)2
[14] and Os(Bcat)(o-tolyl)(CO)2(PPh3)2 [15].
Table 4
˚
Selected bond lengths [A] and angles [ꢁ] for 7
Bond lengths
Os–C(1)
Os–C(72)
Os–P(1)
Os–P(2)
Os–P(3)
Os–Si
1.897(3)
2.179(3)
2.3169(7)
2.3338(7)
2.3807(7)
2.5110(8)
1.888(3)
1.893(3)
1.901(3)
1.151(4)
Si–C(2)
Si–C(3)
Si–C(42)
O(1)–C(1)
Bond angles
C(1)–Os–C(72)
C(1)–Os–P(1)
C(72)–Os–P(1)
C(1)–Os–P(2)
C(72)–Os–P(2)
P(1)–Os–P(2)
C(1)–Os–P(3)
C(72)–Os–P(3)
P(1)–Os–P(3)
P(2)–Os–P(3)
C(1)–Os–Si
The IR spectrum of complex 8 shows two m(CO)
bands at 2001 and 1933 cmꢀ1 indicating a cis disposition
1
of these ligands. In the H NMR spectrum the methyl
signal for the trimethysilyl ligand appears as a doublet
161.59(12)
90.20(10)
104.83(7)
93.86(10)
94.22(8)
98.90(3)
102.84(9)
66.00(8)
94.52(3)
toluene
reflux
1 hr.
Ph2P
PPh3
Os
158.51(3)
87.46(10)
78.00(7)
OC
OC
Me
CO
Os
C(72)–Os–Si
P(1)–Os–Si
P(2)–Os–Si
OC
H
SiMe3
176.38(3)
78.53(3)
88.68(3)
PPh3
+
PPh3
(2)
P(3)–Os–Si
C(2)–Si–C(3)
C(2)–Si–C(42)
C(3)–Si–C(42)
C(2)–Si–Os
104.58(17)
102.95(16)
106.32(15)
123.17(11)
115.02(12)
103.02(10)
176.7(3)
Ph2P
Ph3P
OC
Os
SiMe3
C(3)–Si–Os
CO
(8)
C(42)–Si–Os
O(1)–C(1)–Os
Os–P(3)–C(71)
86.88(10)
Scheme 5. Thermal reactions of Os(SiMe3)(Me)(CO)2(PPh3)2 (2).

3316
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
Table 5
at ꢀ0.20 ppm, with weak coupling observed only to the
trans phosphorus atom. In the 13C NMR spectrum the
methyl signal for the trimethylsilyl ligand appears as a
multiplet at 4.8 ppm. The carbon signals for the two car-
bonyl ligands each appear as doublets of doublets, the
CO trans to phosphorus with JPC values of 77.0 and
5.6 Hz, the CO cis to both phosphorus atoms with
JPC values of 8.2 and 5.7 Hz. In the 31P NMR spec-
trum there are two doublet signals. One has a chemical
shift of ꢀ77.10 ppm and this is assigned to the ortho-
metallated triphenylphosphine ligand. All these NMR
spectroscopic data are compatible with the geometry
shown in Scheme 5 and this was confirmed by an X-
ray crystallographic study.
The molecular structure of 8 is depicted in Fig. 4
and selected bond lengths and angles for 8 are pre-
sented in Table 5. The overall geometry about osmium
is octahedral with the phosphorus atoms of the ortho-
metallated ligand and the triphenylphosphine ligand
located mutually cis. The trimethylsilyl ligand is lo-
cated trans to the triphenylphosphine ligand and the
˚
Selected bond lengths [A] and angles [ꢁ] for 8
Bond lengths
Os–C(1)
Os–C(2)
Os–C(12)
Os–P(1)
Os–P(2)
Os–Si
1.894(3)
1.902(3)
2.148(3)
2.4074(6)
2.4230(6)
2.5166(7)
1.888(3)
1.893(3)
1.897(3)
1.155(3)
1.155(3)
Si–C(4)
Si–C(5)
Si–C(3)
O(1)–C(1)
O(2)–C(2)
Bond angles
C(1)–Os–C(2)
C(1)–Os–C(12)
C(2)–Os–C(12)
C(1)–Os–P(1)
C(2)–Os–P(1)
C(12)–Os–P(1)
C(1)–Os–P(2)
C(2)–Os–P(2)
C(12)–Os–P(2)
P(1)–Os–P(2)
C(1)–Os–Si
96.42(12)
93.97(11)
165.04(11)
159.77(9)
103.12(9)
65.86(7)
89.03(8)
91.07(8)
99.85(7)
95.70(2)
˚
Os–Si distance is 2.5166(7) A. This is even longer than
83.83(8)
89.16(8)
the Os–Si distance found in 7 (2.5110(8)). The Os–P
distance in the ortho-metallated ligand, Os–P(1) is
2.4074(6) and the Os–PPh3 distance is slightly longer
C(2)–Os–Si
C(12)–Os–Si
P(1)–Os–Si
P(2)–Os–Si
81.27(7)
91.22(2)
˚
172.84(2)
102.30(14)
102.34(13)
106.58(14)
110.97(10)
114.28(10)
118.55(9)
177.1(3)
at 2.4230(6) A, probably because of the trans trime-
C(4)–Si–C(5)
C(4)–Si–C(3)
C(5)–Si–C(3)
C(4)–Si–Os
thysilyl ligand. The Os–C distance within the four-
membered ring, Os–C(12) is 2.148(3) close in value
to the other corresponding Os–C distances reported
in this paper.
C(5)–Si–Os
C(3)–Si–Os
O(1)–C(1)–Os
O(2)–C(2)–Os
Os–P(1)–C(11)
177.6(3)
85.86(9)
3. Conclusions
It has been demonstrated that introducing a methyl
group into the coordinatively unsaturated, but rather in-
ert complex, Os(SiMe3)Cl(CO)(PPh3)2, to produce
Os(SiMe3)(Me)(CO)(PPh3)2 (1), opens a pathway to a
facile thermal reaction which leads to a product retain-
ing the Os–Si bond in the ortho-silylated as well as
ortho-metallated complex, Os(j2(Si,P)-SiMe2C6H4PPh2)-
(j2(C,P)-C6H4PPh2)(CO)(PPh3) (5). This reaction prod-
uct may indicate the intermediacy of a silylene complex.
Replacement of triphenylphosphine in 5 by the superior
p-bonding ligand tris(N-pyrrolyl)phosphine leads to
Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)-
[P(NC4H4)3] (7). A structural comparison between 5 and
7 reveals that the Os–Si bond is considerably lengthened
by this substitution. Thermal reaction of the coordin-
atively saturated methyl complex, Os(SiMe3)(Me)-
(CO)2(PPh3)2 (2), leads to ortho-metallated products
again, but none of these contain an ortho-silylated
ligand.
Fig. 4. Molecular geometry of Os(SiMe3)(j2(C,P)-C6H4PPh2)(CO)2-
(PPh3) (8).

G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
3317
4. Experimental
3JPH = 8.6 Hz, OsMe) 7.02–7.75 (m, 30H, PPh3). 13C
2
NMR (CDCl3,d): 9.6 (s, SiMe3), 21.1 (t, JPC = 9.6 Hz,
4.1. General procedures and instruments
OsMe), 128.0 (t0 [16], 2,4JPC = 8.6 Hz, o-Ph), 129.8 (s, p-
1,3
Ph), 133.7 (t0,
J
= 10.4 Hz, m-Ph), 194.1 (t, JPC = 8.2 Hz, CO).
= 46.6 Hz, i-Ph), 134.4 (t0,
PC
3,5
2
Standard laboratory procedures were followed as
have been described previously [16]. The compounds
Os(SiCl3)Cl(CO)(PPh3)2 and Os(SiMe3)Cl(CO)(PPh3)2
were prepared according to the literature methods [8].
Infrared spectra (4000–400 cmꢀ1) were recorded as
Nujol mulls between KBr plates on a Perkin–Elmer Para-
gon 1000 spectrometer. NMR spectra were obtained on
either a Bruker DRX 400 or a Bruker Avance 300 at
25 ꢁC. For the Bruker DRX 400, 1H, 13C, and 31P NMR
spectra were obtained operating at 400.1 (1H), 100.6
(13C), and 162.0 (31P) MHz, respectively. For the Bruker
Avance 300, 1H, 13C, and 31P NMR spectra were obtained
operating at 300.13 (1H), 75.48 (13C), and 121.50 (31P)
MHz, respectively. Resonances are quoted in ppm and
1H NMR spectra referenced to either tetramethylsilane
(0.00 ppm) or the proteo-impurity in the solvent
(7.25 ppm for CHCl3). 13C NMR spectra were referenced
to CDCl3 (77.00 ppm), and 31P NMR spectra to 85%
orthophosphoric acid (0.00 ppm) as an external standard.
In recording 13C NMR data the symbol tꢀ is used to indi-
cate a virtual triplet where only three of the expected five
lines in the X part of an AAꢀX system are observed. This is
frequently the case in the spectra of complexes containing
mutually trans bis(triphenylphosphine) ligands [16]. Ele-
mental analyses were obtained from the Microanalytical
Laboratory, University of Otago.
J
PC
13C NMR (C6D6,d): 10.4 (s, SiMe3), 22.1 (t,
2JPC = 9.5 Hz, OsMe), o-Ph obscured by solvent peaks,
1,3
J
130.0 (s, p-Ph), 134.4 (t0,
= 46.8 Hz, i-Ph), 134.8
PC
3,5
2
(t0,
J
= 11.4 Hz, m-Ph), 194.4 (t, JPC = 7.0 Hz, C
PC
O). 31P NMR (CDCl3,d): 29.19 (s). 31P NMR (C6D6,d):
29.59 (s).
4.3. Preparation of Os(SiMe3)(Me)(CO)2(PPh3)2 (2)
CO gas was bubbled through a red solution of Os(Si-
Me3)(Me)(CO)(PPh3)2 (1) (0.166 g, 0.2 mmol) in CH2Cl2
(10 mL) whereupon the solution immediately became
colourless. EtOH (10 mL) was added and the mixture
concentrated to effect the precipitation of pure 2 as a
colourless crystalline solid (0.164 g, 95%). An alternative
procedure involved preparing compound 1 in situ by
adding five equivalents of MeLi to Os(SiCl3)Cl-
(CO)(PPh3)2 followed by addition of ethanol and car-
bonylation. Details of this procedure are as follows:
MeLi (3.75 mL of a 1.28 mol Lꢀ1 solution, 4.8 mmol)
was added dropwise at 0 ꢁC to a yellow-orange solution
of OsCl(SiCl3)(CO)(PPh3)2 (0.730 g, 0.8 mmol) in tolu-
ene (20 mL). The colour of the reaction mixture changed
from orange to red and then to colourless with forma-
tion of a colourless solid. EtOH (1 mL) was added to
this mixture and stirring continued for 30 min at room
temperature to give a red clear solution. CO gas (1 at-
mos.) was then introduced to give immediately a colour-
less solution. All volatiles were removed under reduced
pressure and the residue dissolved in CH2Cl2 and filtered
through a thin layer of Celite. The filtrate was concen-
trated and EtOH was added. Further concentration
yielded pure 2 as a colourless crystalline solid, which
was collected, washed with EtOH and hexane and dried
in vacuo (0.667 g, 97%). Anal. Calc. for C42H42O2OsP2-
Si: C, 58.72; H, 4.93. Found: C, 58.64; H, 4.88%. IR
(cmꢀ1): 1992s, 1927m, 1896s (1985s, 1910s in CH2Cl2)
m(CO). 1H NMR (CDCl3, d): ꢀ0.96 (t, 3H,
3JPH = 7.2 Hz, OsMe), ꢀ0.12 (s, 9H, SiMe3), 7.35–7.65
(m, 30H, PPh3). 13C NMR (CDCl3, d): ꢀ19.8 (t,
4.2. Preparation of Os(SiMe3)(Me)(CO)(PPh3)2 (1)
MeLi (3.5 mL of a 1.28 mol Lꢀ1 in Et2O, 4.5 mmol)
was added dropwise, at 0 ꢁC, to an yellow-orange solution
of Os(SiCl3)Cl(CO)(PPh3)2 (0.821 g, 0.9 mmol) in toluene
(45 mL). During the addition the colour of the reaction
mixture changed from orange to red, and then to colour-
less, with the formation of a white precipitate. (This white
solid is tentatively formulated as Li[Os(SiMe3)(Me)2-
(CO)(PPh3)2] and an IR spectrum recorded as a Nujol
mull shows m(CO) at 1754 cmꢀ1). EtOH (1 mL) was added
to the colourless suspension and the mixture was stirred at
room temperature for 0.5 h to give eventually a clear red
solution. The resulting solution was concentrated to half
volume, and passed down a short (5 cm) silica gel column
under nitrogen using toluene as eluent. The eluent was
concentrated to 2 mL and EtOH (10 mL) was added
and after standing for half an hour a red crystalline solid
formed. This was collected and washed with EtOH and
hexane to give pure 1 (0.530 g, 71%). Anal. Calc. for
C41H42OOsP2Si: C, 59.26; H, 5.09. Found: C, 59.46; H,
5.25%. IR (cmꢀ1): 1893s, 1867s (1879s in CH2Cl2)
3
2JPC = 6.6 Hz, OsMe), 5.5 (t, JPC = 1.8 Hz, SiMe3),
2,4
127.8 (t0,
J
= 9.8 Hz, o-Ph), 129.8 (s, p-Ph), 134.0
PC
3,5
1,3
(t0,
i-Ph), 183.0 (t, JPC = 11.0 Hz,
J
= 10.8 Hz, m-Ph), 134.6 (t0,
J
C O), 188.9 (t,
= 50.6 Hz,
PC
PC
2
2JPC = 9.0 Hz, C O). 31P NMR (CDCl3, d): 4.34 (s).
4.4. Preparation of Os(SiMe3)(p-tolyl)(CO)(PPh3)2
(3)
1
m(CO). H NMR (CDCl3, d): 0.01 (s, 9H, SiMe3), 0.12
(t, 3H, 3JPH = 8.7 Hz, OsMe), 7.32–7.52 (m, 30H, PPh3).
1H NMR (C6D6,d): 0.51 (s, 9H, SiMe3), 0.69 (t, 3H,
p-TolLi (0.50 mL of 0.77 mol Lꢀ1 in Et2O, 0.4 mmol)
was added dropwise at room temperature to a deep red

3318
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
solution of Os(SiMe3)(Me)(CO)(PPh3)2 (1) (0.166 g,
0.20 mmol) in toluene (10 mL) to produce an almost col-
ourless solution. After the mixture had been stirred for
30 min EtOH (1 mL) was added slowly to give a deep
red solution. All volatiles were removed under reduced
pressure and the red residue dissolved in CH2Cl2 and fil-
tered through a thin layer of silica gel (5 cm) under nitro-
gen. The volume of the red filtrate was reduced in vacuo
to ca. 5 mL before EtOH (5 mL) was added. Further
concentration yielded pure 3 as a red crystalline solid,
which was collected and washed with EtOH and hexane
(0.143 g, 79%). Anal. Calc. for C47H46OOsP2Si: C, 62.23;
H, 5.11. Found: C, 62.12; H, 5.09%. IR (cmꢀ1): 1900s
4.6. Thermal reaction of Os(SiMe3)Cl(CO)(PPh3)2
A mixture of Os(SiMe3)Cl(CO)(PPh3)2 (0.082 g,
0.1 mmol), PPh3 (0.079 g, 0.3 mmol) was heated under
nitrogen at 160–200 ꢁC for 2–4 h, during which time the
red oil became almost colourless. After cooling, the result-
ing mixture was re-dissolved in a minimum of CH2Cl2 and
subjected to preparative thin-layer chromatography on
silica gel using CH2Cl2/hexane (v/v = 1:1) as eluent. Form
the first and second major colourless bands were obtained
OsHCl(CO)(PPh3)3 (ca. 50%) and Os(j2(C,P)-
C6H4PPh2)Cl(CO)(PPh3)2 (ca. 40%), respectively. Both
compounds were identified by comparison with reported
IR and NMR spectral data (OsHCl(CO)(PPh3)3
[17];Os(j2(C,P)-C6H4PPh2)Cl(CO)(PPh3)2 [9]).
1
m(CO). H NMR (CDCl3, d): 0.20 (s, 9H, SiMe3), 2.22
(s, 3H, p Me C6H4), 6.59–7.35 (m, 34H, p-MeC6H4 and
3
PPh3). 13C NMR (CDCl3,d): 9.2 (t, JCP = 1.9 Hz,
SiMe3), 21.0 (s, p-MeC6H4), 125.3 (s, p-MeC6H4), 127.8
(br, o-PPh3), 128.2 (s, p-MeC6H4), 129.0 (s, p-MeC6H4),
129.6 (br, p-PPh3), 131.0 (s, p-MeC6H4), 133.5 (br, i-
PPh3), 134.6 (br, m-PPh3), 137.9 (s, p-MeC6H4), 174.0
4.7. Preparation of Os(j2(Si,P)-
SiMe2C6H4PPh2)(j2(C,P)-C6H4PPh2)(CO)(PPh3)
(5)
2
2
(t, JPC = 12.9 Hz, Os–C6H4Me-4), 194.6 (t, JPC
8.6 Hz, CO). 31P NMR (CDCl3,d): 22.31 (s).
=
A
mixture of Os(SiMe3)(Me)(CO)(PPh3)2 (1)
(0.050 g, 0.06 mmol), PPh3 (0.032 g, 0.12 mmol) and tol-
uene (10 mL) was heated under reflux for 1 h during
which time the red solution became almost colourless.
The solvent was removed under reduced pressure and
the resulting residue re-dissolved in a minimum of
CH2Cl2 and subjected to preparative thin-layer chroma-
tography on silica gel using CH2Cl2 and hexane
(v/v = 1:2) as eluent. The fastest moving band is PPh3.
From the second, colourless band, after recrystallisation
from CH2Cl2 and hexane, pure 5 was obtained as a col-
ourless crystalline solid (0.032 g, 50%). (From a third
band was obtained another colourless product, com-
pound 6, see below). Anal. Calc. for C57H49OOsP3-
Si Æ 0.5(C6H14): C, 65.26; H, 5.11. Found: C, 65.17; H,
4.5. Preparation of Os(SiMe3)(p-tolyl)(CO)2(PPh3)2
(4)
p-TolLi (0.50 mL of a 0.77 mol Lꢀ1 solution in Et2O,
0.4 mmol), at room temperature, was added dropwise to
a
deep red solution of Os(SiMe3)Me(CO)(PPh3)2
(0.166 g, 0.20 mmol) in toluene (10 mL) to produce an
almost colourless solution. After the mixture was stirred
for half an hour, EtOH (1 mL) was added slowly to give
a deep red solution. Introduction of CO gas at atmo-
spheric pressure into the reaction solution resulted
immediately in a colourless solution. All the volatiles
were removed under reduced pressure and the residue
dissolved in a minimum volume of CH2Cl2. This solu-
tion was then subjected to flash column chromatog-
raphy on a silica gel support using as eluent CH2Cl2/
n-hexane (v/v = 1:3). The main colourless band from
the column was collected and the solvent removed under
reduced pressure. Recrystallisation of the resulting solid
using CH2Cl2/n-heptane yielded pure 4 as a colourless
crystalline solid (0.156 g, 83%). Anal. Calc. for
C48H46O2OsP2Si: C, 61.65; H, 4.96. Found: C, 61.87;
H, 5.00%. IR (cmꢀ1): 2002, 1925 m(CO). 1H NMR
(CDCl3, d): ꢀ0.04 (s, 9H, SiMe3), 2.13 (s, 3H,
p-MeC6H4), 6.23 (m, 2H, p-MeC6H4), 6.98 (m, 2H,
p-MeC6H4), 7.14–7.29 (m, 30H, 2PPh3). 13C NMR
1
5.12 (the hexane of solvation was seen in both the H
and 13C NMR spectra). The single crystal for X-ray
structural analysis was grown from a different solvent
combination (CH2Cl2 and ethanol) over several days
and proved to solvated with two molecules of water
(see Section 4.10). IR (cmꢀ1): 1906 (s) m(CO). 1H
NMR (CDCl3, d): ꢀ1.12 (s, 3H, SiMe), 0.12 (s, 3H,
SiMe), 5.65–8.34 (m, 43H). 13C NMR (CDCl3, d):
ꢀ2.3 (s, SiMe), 5.2 (br, SiMe), 121.0–157.9 (m, aromatic
carbons), 192.6 (m, CO). 31P NMR (CDCl3, d): [Note:
the phosphorus atom labels are given in Scheme 4]
2
2
29.26 (dd, JP(a)–P(c) = 222.5 Hz, JP(a)–P(b) = 16.1 Hz,
2
2
P(a)), ꢀ6.11 (dd, JP(a)–P(b) = 16.1 Hz, JP(b)–P(c)
=
2
20.5 Hz, P(b)), ꢀ62.46 (dd, JP(a)–P(c) = 222.5 Hz,
(CDCl3, d): 7.6 (s, SiMe3), 20.7 (s, p-MeC6H4), 127.3
2JP(b)–P(c) = 20.5 Hz, P(c)).
2,4
(t0,
J
= 9.7 Hz, o-Ph), 127.8 (s, p-MeC6H4), 129.4
PC
3,5
(s, p-Ph), 134.4 (t0,
J
= 10.3 Hz, m-Ph), 134.5
2
4.8. Preparation of Os(j2(C,P)-C6H4PPh2)2
(CO)(PPh3) (6)
PC
1,3
(t0,
Os–C6H4Me-4), 147.0 (s, p-MeC6H4), 181.0 (t, JPC
J
= 50.8 Hz, i-Ph), 136.2 (t, JPC = 11.9 Hz,
PC
2
=
9.1 Hz, CO), 188.4 (t, JPC = 7.7 Hz, CO). 31P NMR
(CDCl3, d): ꢀ4.16 (s).
From the thermal reaction between Os(SiMe3)(Me)-
(CO)(PPh3)2 and PPh3 in toluene described in detail
2

G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
3319
above (Section 4.6), the third colourless band obtained
from the preparative thin-layer chromatography proce-
dure was collected. This solid was recrystallised from
CH2Cl2/C2H5OH to give pure 6 in low and variable
yield from repeated experiments (ca. 25%). Anal. Calc.
for C55H43OOsP3: C, 65.86; H, 4.32. Found: C, 65.20;
H, 4.67%. The single crystal for X-ray structure determi-
nation was grown from CH2Cl2/C6H14 and proved to be
a 0.5 hexane solvate (see Section 4.10). IR (cmꢀ1): 1888
colourless to red and then to almost colourless. The sol-
vent was removed under reduced pressure and the
resulting residue was dissolved in a minimum of CH2Cl2
and purified by preparative thin-layer chromatography
on silica gel using CH2Cl2 and hexane (v/v = 1:2) as elu-
ent. The second colourless band was collected and from
this was obtained after recrystallisation from CH2Cl2/
EtOH pure 8 as a colourless crystalline solid (0.190 g,
28%). A single crystal for X-ray crystal structure
determination was grown from CH2Cl2/C6H14. Anal.
Calc. for C41H38O2OsP2Si: C, 58.42; H, 4.54. Found:
C, 58.34; H, 4.49%. IR (cmꢀ1): 2001s, 1933s m(CO),
1
m(CO). H NMR (CDCl3, d): 5.87–7.40 (m, 43H, aro-
matic hydrogens). 13C NMR (CDCl3, d): 121.2–160.1
(m, aromatic carbons), 195.5 (m, CO). 31P NMR
(CDCl3, d): [Note: the phosphorus atom labels are given
1
843m (SiMe3). H NMR (CDCl3, d): ꢀ0.20 (apparent
in Scheme 4] 15.16 (dd, 2JP(a)–P(c) = 256.1 Hz, 2JP(a)–P(b)
=
=
4
d, JP(trans)H = 1.2 Hz, 9H, SiMe3), 6.50–7.85 (m, 29H,
8.1 Hz, P(a)), ꢀ72.81 (dd, 2JP(a)–P(b) = 8.5 Hz, 2JP(b)–P(c)
aromatic protons). 13C NMR (CDCl3, d): 4.8 (m,
SiMe3), 121.6–150.7 (m, aromatic carbons), 186.6 (dd,
2
16.8 Hz, P(b)), ꢀ68.78 (dd, JP(a)–P(c) = 256.4 Hz,
2JP(b)–P(c) = 17.1 Hz, P(c)).
2JP(trans)C = 77.0 Hz, JP(cis)C = 5.6 Hz, CO(trans to
phosphorus of ortho-metallated phosphine)), 189.4 (dd,
2
4.9. Preparation of Os(j2(Si,P)-SiMe2C6H4PPh2)-
(j2(C,P)-C6H4PPh2)(CO)[P(NC4H4)3] (7)
2JP(cis)C = 8.2 Hz, and JP(cis)C = 5.7 Hz, CO(cis to both
2
phosphorus atoms)). 31P NMR (CDCl3, d): ꢀ77.10 (d,
2JPP = 27.5 Hz, phosphorus of ortho-metallated phos-
A mixture of Os(j2(Si,P)-SiMe2C6H4PPh2)(j2(C,P)-
C6H4PPh2)(CO)(PPh3) (5) (0.053 g, 0.05 mmol),
P(NC4H4)3 (0.013 g, 0.055 mmol) and benzene (10 mL)
was heated under reflux for 1 h. The solvent was re-
moved under reduced pressure and the resulting residue
was recrystallised from CH2Cl2 and hexane to give pure
7 as a colourless crystalline solid (0.045 g, 88%).
Compound 7 was also detected by 31P NMR spectros-
copy in mixtures obtained from the thermal reaction
of Os(SiMe3)(Me)(CO)(PPh3)2 (1) and P(NC4H4)3 but
a pure sample could not be extracted by this procedure.
Anal. Calc. for C51H46N3OOsP3Si Æ 0.25C6H14: C, 60.07;
H, 4.75; N, 4.00. Found: C, 60.21; H, 4.73; N, 4.10%. 1H
and 13C NMR spectra of the analytical sample con-
firmed the presence of hexane. The single crystal for
X-ray structure determination was grown from CH2Cl2
and hexane over a period of one week and the crystal
did not contain solvent (see Table 1). IR (cmꢀ1): 1941
m(CO). 1H NMR (CDCl3, d): ꢀ1.15 (s, 3H, SiMe),
phine), ꢀ3.38 (d, JPP = 27.5 Hz, PPh3).
2
From the chromatography procedure detailed above
the third colourless band was collected and yielded, after
recrystallisation from CH2Cl2/EtOH, pure Os(j2(C,P)-
C6H4PPh2)H(CO)2(PPh3) as a colourless crystalline so-
lid (0.061 g, 10%) which was identified by comparison
of spectroscopic data reported for an authentic sample
[14,15].
4.11. X-ray crystal structure determinations for
complexes 5, 6, 7, and 8.
X-ray data collections were by a Siemens SMART
diffractometer with a CCD area detector using graph-
˚
ite monochromated Mo Ka radiation (k = 0.71073 A)
at 84 K for 5 and 6, 150 K for 7 and 8. Data were
integrated and corrected for Lorentz and polarisation
effects using SAINT [18]. Semi-empirical absorption cor-
rections were applied based on equivalent reflections
using SADABS [19]. The structures were solved by Patt-
erson or direct methods and refined by full-matrix
least-squares on F2 using programs SHELXS [20] and
SHELXL [21]. All non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were located geomet-
rically and refined using a riding model. Compound 5
contains two molecules of water of crystallization with
4
0.13 (d, JPH = 2.3 Hz, 3H, SiMe), 5.85–8.23 (m, 40H,
Ph and NC4H4). 13C NMR (CDCl3, d): ꢀ2.3 (m, SiMe),
3
5.3 (d, JPC = 6.7 Hz, SiMe), 111.0–156.8 (m, aromatic
carbons), 190.1 (m, CO). 31P NMR (CDCl3, d): [Note:
the phosphorus atom labels are given in Scheme 4]
2
28.53 (dd, JP(a)–P(c) = 208.8 Hz, JP(a)–P(b) = 20.2 Hz,
2
2
P(a)), 70.15 (dd, JP(a)–P(b) = 20.2 Hz, JP(b)–P(c)
2
=
2
25.4 Hz, P(b)), ꢀ64.68 (dd, JP(a)–P(c) = 208.8 Hz,
2JP(b)–P(c) = 25.4 Hz, P(c)).
˚
an O(2) ꢂ ꢂ ꢂ O(3) separation of 2.724 A. There are no
other H-bonding contacts in the crystal structure.
Compound 6 contains 0.5 molecules of hexane of crys-
tallization, for which five carbon atoms were refined
isotropically with no hydrogen atoms included, but
the sixth carbon could not be reliably located. Crystal
data and refinement details for all four structures are
given in Table 1.
4.10. Preparation of Os(SiMe3)(j2(C,P)-C6H4PPh2)-
(CO)2(PPh3) (8)
Os(SiMe3)(Me)(CO)2(PPh3)2 (2) (0.687 g, 0.80 mmol)
in toluene (30 mL) was heated under reflux for 1 h, dur-
ing which time the colour of the solution changed from

3320
G.R. Clark et al. / Journal of Organometallic Chemistry 690 (2005) 3309–3320
[4] Y. Tanaka, H. Yamashita, S. Shimada, M. Tanaka, Organomet-
allics 16 (1997) 3246.
5. Supplementary material
[5] K.C. Brinkman, A.J. Blakeney, W. Krone-Schmidt, J.A. Gladysz,
Organometallics 3 (1984) 1325.
Crystallographic data (excluding structure factors)
for the structures reported have been deposited with
the Cambridge Crystallographic Data Centre as Supple-
mentary Publication Nos. 2632126–263129 for 5, 6, 7
and 8, respectively. Copies of this information can be
obtained free of charge from the Director, CCDC, 12
Union Road, Cambridge, CB2 1EZ, UK (fax: +44-
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or
www: http://www.ccdc.cam.ac.uk).
[6] (a) M. Aizenberg, D. Milstein, Angew. Chem. Int. Ed. Engl. 33
(1994) 317;
(b) M. Aizenberg, D. Milstein, J. Am. Chem. Soc. 117 (1995)
6456.
[7] M. Albrecht, C.E.F. Rickard, W.R. Roper, A. Williamson, S.D.
Woodgate, L.J. Wright, J. Organomet. Chem. 625 (2001) 77.
[8] K. Hubler, P.A. Hunt, S.M. Maddock, C.E.F. Rickard, W.R.
¨
Roper, D.M. Salter, P. Schwerdtfeger, L.J. Wright, Organomet-
allics 16 (1997) 5076.
[9] M.A. Bennett, A.M. Clark, M. Contel, C.E.F. Rickard, W.R.
Roper, L.J. Wright, J. Organomet. Chem. 601 (2000) 299.
[10] G.R. Clark, C.E.F. Rickard, W.R. Roper, D.M. Salter, L.J.
Wright, Pure Appl. Chem. 62 (1990) 1039.
Acknowledgements
[11] H. Wada, H. Tobita, H. Ogino, Organometallics 16 (1997) 3870.
[12] C.E.F. Rickard, W.R. Roper, T.J. Woodman, L.J. Wright, Chem.
Commun. (1999) 1101.
We thank the Marsden Fund, administered by the
Royal Society of New Zealand, for granting a Post Doc-
toral Fellowship to G.-L.L. We also thank The Univer-
sity of Auckland Research Committee for partial
support of this work through grants-in-aid. Dr. D.M.
Salter is thanked for providing some data for complex 5.
[13] (a) K.G. Moloy, J.L. Petersen, J. Am. Chem. Soc. 117 (1995)
7696;
(b) C.E.F. Rickard, W.R. Roper, S.D. Woodgate, L.J. Wright, J.
Organomet. Chem. 643–644 (2002) 168.
[14] G.R. Clark, C.E. Headford, K. Marsden, W.R. Roper, J.
Organomet. Chem. 231 (1982) 335.
[15] C.E.F. Rickard, W.R. Roper, A. Williamson, L.J. Wright,
Organometallics 19 (2000) 4344.
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