The first areneosmium(II) complexes with diarylcarbenes as ligands

Article abstract of DOI:10.1021/om0007062

Using [(η⁶-mes)Os(κ¹-O₂CCF ₃)(κ²-O₂CCF₃)] (1) and diaryldiazomethanes as the starting materials, the half-sandwich-type carbeneosmium(II) complexes [[(η⁶-mes)Os(κ

Full text of DOI:10.1021/om0007062

Organometallics 2000, 19, 4687-4689
4687
Th e F ir st Ar en eosm iu m (II) Com p lexes w ith
Dia r ylca r ben es a s Liga n d s
Birgit Weberndo¨rfer, Gerhard Henig, and Helmut Werner*
Institut fu¨r Anorganische Chemie, Universita¨t Wu¨rzburg, Am Hubland,
D-97074 Wu¨rzburg, Germany
Received August 14, 2000
Summary: Using [(η6-mes)Os(κ1-O2CCF3)(κ2-O2CCF3)]
Sch em e 1
(1) and diaryldiazomethanes as the starting materials,
the half-sandwich-type carbeneosmium(II) complexes
[(η6-mes)Os(κ1-O2CCF3)2(dCR2)] (2a -c; R ) p-C6H4X
with X ) H, Me, Cl) were prepared. The dichloro
derivatives [(η6-mes)OsCl2(dCR2)] (3a ,b), obtained from
2a ,b and Me3SiCl, react with PPh3 in the presence of
AgPF6 to form the cationic compounds [(η6-mes)OsCl-
(dCR2)(PPh3)]PF6 (5a ,b); moreover, the π-allyl complex
[(η6-mes)OsBr(η3-CH2CHCPh2)] (4) was prepared from
2a and CH2dCHMgBr.
In the context of our investigations on the reactivity
of carbenemetal complexes, in which a non-Fischer-type
carbene ligand is coordinated to an electron-rich metal
center, we recently observed that for the preparation
of diarylcarbeneruthenium(II) compounds of the general
composition [(η5-C5H5)RuX(dCRR′)(PPh3)] (R ) R′ )
aryl; X ) Cl, CH3CO2) the use of the acetato derivative
[(η5-C5H5)Ru(κ2-O2CCH3)(PPh3)] as the starting mate-
rial is the method of choice. It reacts with diaryldiazo-
methanes in toluene at room temperature via elimina-
tion of N2 to give the compounds [(η5-C5H5)Ru-
(κ1-O2CCH3)(dCRR′)(PPh3)], which upon treatment with
[Et3NH]Cl are converted into the more stable chloro
derivatives [(η5-C5H5)RuCl(dCRR′)(PPh3)].1 By taking
into consideration that attempts to obtain half-sandwich-
type carbeneosmium(II) complexes [(η6-mes)OsCl2-
(dCRR′)] from [(η6-mes)OsCl2]n (mes ) 1,3,5-C6H3Me3)
and diazomethanes RR′CN2 failed,2 we decided to apply
the corresponding bis(trifluoracetate) 1 as the precursor.
From previous work it was known that compound 1
(which was prepared from [(η6-mes)OsCl2]n and 2n equiv
of CF3CO2Ag) reacts with CO and various phosphines
to give the corresponding 1:1 adducts [(η6-mes)Os-
(κ1-O2CCF3)2(L)], thereby converting one of the trifluor-
acetato ligands from a κ2- to a κ1-bonding mode.3
We have now discovered (see Scheme 1) that a similar
reaction of 1 takes place with diaryldiazomethanes.
Upon treatment of a solution of 1 in benzene with a
solution of R2CN2 in the same solvent at room temper-
ature, a rapid evolution of gas (N2), accompanied by a
change of color from brown to green, occurred. Removal
of the solvent and recrystallization of the residue from
toluene-hexane (1:20) gave dark green or olive green,
only moderately air-sensitive solids [(η6-mes)Os(κ1-
O2CCF3)2(dCR2)] (2a -c) in good to excellent yield.4 The
most typical spectroscopic feature of 2a -c is the signal
for the carbene carbon atom in the 13C NMR spectra at
δ 306-310, which is considerably shifted to lower field
compared with [(η6-mes)OsPh2{dC(NHMe)Ph}] (δ 222).5
For the 13C nuclei of the aryl groups of 2a -c only a
single set of signals is observed, indicating that at room
temperature the rotation around the Os-C(carbene)
bond is not hindered on the NMR time scale.6
The X-ray crystal structure analysis of 2b (Figure 1)7
confirms the anticipated piano-stool configuration of the
molecule. The Os-C1 distance of 1.957(7) Å is almost
identical to that in the five-coordinate osmium(0) com-
pound [OsCl(dCF2)(NO)(PPh3)2] (1.967(4) Å)8 and in the
six-coordinate osmium(II) complexes [OsHCl(dCHR)-
(4) 2a : yield 91%, dark green solid, mp 89 °C dec. 2b: yield 71%,
olive green solid, mp 107 °C dec. 2c: yield 58%, olive green solid, mp
118 °C dec. 3a : yield 79%, olive green solid, mp 126 °C dec. 3b: yield
87%, olive green solid, mp 153 °C dec. 4: yield 61%, yellow solid, mp
94 °C dec. 5a : yield 96%, dark green solid, mp 136 °C dec, Λ (CH3-
NO2) 67 cm2 Ω-1 mol-1. 5b: yield 93%, dark green solid, mp 151 °C
dec, Λ (CH3NO2) 71 cm2 Ω-1 mol-1
.
(5) Werner, H.; Wecker, U.; Peters, K.; von Schnering, H. G. J .
Organomet. Chem. 1994, 469, 205-212.
(6) Selected spectroscopic data for 2a -c, 3a ,b, 4, and 5a ,b (omitting
the 1H and 13C NMR data for the mesitylene ligand and the aryl groups
as well as the 19F and 31P NMR data for the PF6 anion) are as follows.
2a : 13C NMR (CD2Cl2, 50.3 MHz) δ 310.3 (s, OsdC), 161.7 (q, J (FC) )
36.9 Hz, CF3CO2), 114.3 (q, J (FC) ) 290.7 Hz, CF3CO2); 19F NMR (CD2-
Cl2, 188.3 MHz) δ -73.4 (s). 2b: 13C NMR (CD2Cl2, 100.6 MHz) δ 307.9
(s, OsdC), 161.9 (q, J (FC) ) 36.9 Hz, CF3CO2), 114.6 (q, J (FC) ) 291.1
Hz, CF3CO2); 19F NMR (CD2Cl2, 376.5 MHz) δ -75.3 (s). 2c: 13C NMR
(CD2Cl2, 100.6 MHz) δ 305.9 (s, OsdC), 162.1 (q, J (FC) ) 37.2 Hz,
CF3CO2), 114.5 (q, J (FC) ) 290.7 Hz, CF3CO2); 19F NMR (CD2Cl2,
376.5 MHz) δ -75.2 (s). 3a : 13C NMR (CD2Cl2, 100.6 MHz) δ 299.2 (s,
OsdC). 3b: 13C NMR (CD2Cl2, 50.3 MHz) δ 302.8 (s, OsdC). 4: 1H
NMR (C6D6, 400 MHz) δ 5.00 (dd, J (HH) ) 8.8 and 6.7 Hz, 1H, Ph2-
CCHCH2), 2.75 (dd, J (HH) ) 6.7 and 1.5 Hz, 1H, Ph2CCHCH2), 2.42
(dd, J (HH) ) 8.8 and 1.5 Hz, 1H, Ph2CCHCH2); 13C NMR (C6D6, 100.6
MHz) δ 74.5 (s, CH2CHCPh2), 66.1 (s, CH2CHCPh2), 33.8 (s, CH2-
CHCPh2). 5a : 13C NMR (CD2Cl2, 75.5 MHz) δ 292.3 (d, J (PC) ) 11.3
Hz, OsdC). 5b: 13C NMR (CD2Cl2, 50.3 MHz) δ 291.2 (d, J (PC) ) 11.4
Hz, OsdC).
(1) Braun, T.; Gevert, O.; Werner, H. J . Am. Chem. Soc. 1995, 117,
7291-7292.
(2) Henig, G. Dissertation, Universita¨t Wu¨rzburg, 1997.
(3) Werner, H.; Stahl, S.; Kohlmann, W. J . Organomet. Chem. 1991,
409, 285-298.
10.1021/om0007062 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 10/21/2000

4688 Organometallics, Vol. 19, No. 23, 2000
Communications
Sch em e 2
Sch em e 3
F igu r e 1. ORTEP diagram of compound 2b. Selected bond
distances (Å) and angles (deg): Os-O1, 2.108(4); Os-O4,
2.096(4); Os-C1, 1.957(7); Os-C30, 2.197(6); Os-C31,
2.328(6); Os-C32, 2.342(6); Os-C33, 2.207(6); Os-C34,
2.214(5); Os-C35, 2.265(5); C1-Os-O1, 85.0(2); C1-Os-
O4, 95.1(2); O1-Os-O2, 81.8(2).
(CO)(PiPr3)2] (R ) CO2Et: 1.949(2) Å; R ) SiMe3:
1.965(5) Å) and [OsCl2(dCHPh)(CO)(PiPr3)2] (1.95(2)
Å);9 it is, however, slightly shorter than in the above-
mentioned species [(η6-mes)OsPh2{dC(NHMe)Ph}]
(1.992(5) Å) with a Fischer-type carbene ligand.5 The
two bond angles C1-Os-O1 and C1-Os-O4 differ by
about 10°, which is presumably due to steric hindrance
between one of the tolyl rings and the mesitylene unit.
Treatment of 2a or 2b with a 3-fold excess of
Me3SiCl in CH2Cl2 at -78 °C results in a gradual
change of color and affords after warming of the solution
to room temperature, evaporation of the solvent, and
recrystallization of the residue from toluene-hexane
(1:2) the dichloro derivatives 3a and 3b in, respectively,
79% and 87% yield (Scheme 2). The 13C NMR spectra
of 3a and 3b display the carbene carbon resonance at δ
299.2 (3a ) and 302.8 (3b) and thus at somewhat higher
field compared with the CF3CO2 analogues.
η1/η3 allyl rearrangment, could also be considered.
1
Although on the basis of the H and 13C NMR data it
cannot be decided whether the CH2CHCPh2 ligand of 4
is linked in exo or endo position to the (η6-mes)OsBr
fragment, there is no doubt that in contrast with the
cyclopentadienylruthenium compounds [(η5-C5H5)Ru(η3-
CH2CHCR2)(PPh3)] (R ) p-C6H4X)1 only one isomer is
present. In analogy with the structurally characterized
2-methylallyl complex [(η6-mes)OsCl(η3-CH2CMeCH2)]10
we assume that the exo isomer is thermodynamically
preferred.
By attempting to further modify the coordination
sphere of osmium(II) in the half-sandwich-type com-
pounds [(η6-mes)OsXY(dCR2)], we also prepared cat-
ionic species via displacement of one of the chloro
ligands in 3a ,b by triphenylphosphine. The PF6 salts
5a ,b (Scheme 3) were obtained upon treatment of a
solution of 3a ,b in THF with PPh3 in the presence of
AgPF6 at -78 °C. After separation of AgCl, removal of
the solvent, and recrystallization from CH2Cl2-hexane
(1:7.5) dark green solids were isolated; they were
characterized by elemental analysis, conductivity mea-
surements, and spectroscopic techniques.
The reaction of 2a with the vinyl Grignard reagent
CH2dCHMgBr leads, in THF at low temperature, to the
displacement of both trifluoracetate groups and to the
formation of the π-allyl complex 4, containing an
unsymmetrical 1,1-diphenylallyl ligand. It is conceivable
that a carbene(η1-vinyl)metal species is formed as an
intermediate, which by intramolecular C-C coupling
rearranges to the final product. An alternative pathway,
addition of the C-nucleophile to the carbene carbon
The molecular structure of the cation of 5b is shown
in Figure 2.11 While the Os-C(ring) distances in the
half-sandwich-type cation are somewhat longer than in
the neutral complex 2b, the Os-C1 distance of 1.93(1)
Å is nearly identical to that in 2b . Two of the bond
-
followed by elimination of CF3CO2 with concomitant
(7) Crystal data for 2b: monoclinic, P21/c (No. 14), a ) 11.989(1) Å,
b ) 11.998(1) Å, c ) 19.542(2) Å, â ) 106.35(1)°, V ) 2695.1(4) Å3, Z
) 4, Dcalcd ) 1.801 g cm-3, T ) 173(2) K, µ(Mo KR) ) 4.814 cm-1; data
collected on a Stoe IPDS diffractometer using Φ scan mode (2θmax
)
(10) Wecker, U.; Werner, H.; Peters, K.; von Schnering, H. G. Chem.
Ber. 1994, 127, 1021-1029.
54.12°); 25 917 reflections scanned, 5880 unique, 3482 observed (I >
2σ(I)); 385 parameters refined to give R ) 3.72% and Rw ) 7.80% with
(11) Crystal data for 5b‚0.85 CH2Cl2: monoclinic, P21 (No. 4), a )
9.876(1) Å, b ) 22.627(2) Å, c ) 10.416(1) Å, â ) 117.63(1)°, V ) 2062.2-
(4) Å3, Z ) 2, Dcalcd ) 1.642 g cm-3, T ) 193(2) K, µ(Mo KR) ) 4.814
cm-1; data collected on a Stoe IPDS diffractometer using Φ scan mode
(2θmax ) 50.02°); 12 498 reflections scanned, 6665 unique, 5001
observed (I > 2σ(I)); extinction parameter 0.0010(2), Flack parameter
-0.024(10), 503 parameters refined to give R ) 4.26% and Rw ) 6.96%
with a reflex-parameter ratio of 13.2 and a residual electron density
a
reflex-parameter ratio of 15.3 and
a residual electron density
+0.761/-1.442 e Å-3
.
(8) (a) Hill, A. F.; Roper, W. R.; Waters, J . M.; Wright, A. H. J . Am.
Chem. Soc. 1983, 105, 5939-5940. (b) Roper, W. R. J . Organomet.
Chem. 1986, 300, 167-190.
(9) Werner, H.; Stu¨er, W.; Wolf, J .; Laubender, M.; Weberndo¨rfer,
B.; Herbst-Irmer, C.; Lehmann, C. Eur. J . Inorg. Chem. 1999, 1889-
1897.
+1.303/-1.039 e Å-3
.

Communications
Organometallics, Vol. 19, No. 23, 2000 4689
In conclusion, we have shown that by using 1 as the
starting material the preparation of areneosmium(II)
complexes with diarylcarbene ligands can be achieved.
Moreover, from the neutral precursors 3a ,b related
cationic species 5a ,b can be generated. Although various
osmium(0) and osmium(II) compounds containing an
OsdCR2 unit are already known,8,9,12,13 to the best of
our knowledge 2a -c, 3a ,b, and 5a ,b are the first half-
sandwich-type osmium complexes with a non-Fischer-
type carbene ligand.
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support from the Deutsche Forschungsgemein-
schaft (Grant No. SFB 347), the Fonds der Chemischen
Industrie, and the BASF AG.
Su p p or tin g In for m a tion Ava ila ble: A table with the
elemental analysis of compounds 2a -c, 3a ,b, 4, and 5a ,b as
well as fully labeled diagrams and tables of crystallographic
data, data collection, and solution and refinement details,
positional and thermal parameters, and both distances and
angles for 2b and 5b. This material is available free of charge
via the Internet at http://pubs.acs.org.
F igu r e 2. ORTEP diagram of the cation of 5b. Selected
bond distances (Å) and angles (deg): Os-P1, 2.377(2); Os-
C1, 2.384(2); Os-C1, 1.93(1); Os-C30, 2.305(9); Os-C31,
2.35(1); Os-C32, 2.40(1); Os-C33, 2.26(1); Os-C34, 2.325-
(10); Os-C35, 2.27(1); C1-Os-P1, 93.4(3); C1-Os-C1,
98.1(4); P1-Os-C1, 81.54(9).
OM0007062
(12) Brothers, P. J .; Roper, W. R. Chem. Rev. 1988, 88, 1293-1326.
(13) (a) Werner, H.; Weber, B.; Nu¨rnberg, O.; Wolf, J . Angew. Chem.
1992, 104, 1105-1107; Angew. Chem., Int. Ed. Engl. 1992, 31, 1025-
1026. (b) Esteruelas, M. A.; Lahoz, F. J .; Onate, E.; Oro, L. A.; Zeier,
B. Organometallics 1994, 13, 4258-4265. (c) Esteruelas, M. A.; Lahoz,
F. J .; Onate, E.; Oro, L. A.; Valero, C.; Zeier, B. J . Am. Chem. Soc.
1995, 117, 7935-7942.
angles of the OsL1L2L3 fragment, C1-Os-P1 (93.4(3)°)
and C1-Os-C1 (98.1(4)°), are considerably larger than
the third one (P1-Os-C1 ) 81.54(9)°), which we as-
sume is due to the steric demand of the carbene ligand.