(η5-C5H5)(CO)2MoGeC6H3-2,6-Mes2: A transition-metal germyly ne complex

Full text of DOI:10.1021/ja963132u

11966
J. Am. Chem. Soc. 1996, 118, 11966-11967
(η5-C5H5)(CO)2MoGeC6H3-2,6-Mes2: A
Transition-Metal Germylyne Complex
Richard S. Simons and Philip P. Power*
Department of Chemistry, UniVersity of California
DaVis, California 95616
ReceiVed September 6, 1996
Triple bonding between transition elements is a feature
commonly encountered in several classes of dimetal complexes.1
For the most part such bonding is homonuclear, whereas
heteronuclear triple bonding is generally confined to species
with bonds to first row main group elements, as exemplified in
carbyne2 or nitrido complexes.3 Rare exceptions to this
generalization are the recently reported phosphido derivatives
Mo(P)(NRAr)34 (R ) -C(CD3)2CH3, Ar ) 3,5-(CH3)2C6H3-)
and W(P)(NN3)5 (NN3 ) {(Me3SiNCH2CH2)3N}3-) which
feature formal triple bonds between phosphorus and molybde-
num or tungsten. Despite the existence of the donor stabilized
silylyne complex [(η5-C5Me5)(Me3P)2RuSi{(bipy)(SC6H4-4-
Me)}][OTf]2,6 in which the silicon is four-coordinate, no
transition complexes featuring triple bonds to the heavier
elements of the carbon group (i.e., Si, Ge, Sn, or Pb) have been
isolated as stable molecules. In this paper the synthesis and
characterization of (η5-C5H5)(CO)2MoGeC6H3-2,6-Mes2 (1),
which contains a molybdenum-germanium triple bond, is now
described.
Figure 1. Thermal ellipsoid plot (30%) of 1 with hydrogen atoms not
shown. Selected bond distances (Å) and angles (deg) are as follows:
Mo-Ge ) 2.271(1), Mo-C(25) ) 2.379(12), Mo-C(26) ) 2.34(1),
Mo-C(27) ) 2.31(1), Mo-C(28) ) 2.30(1), Mo-C(29) ) 2.34(1),
Mo-C(30) ) 1.950(9), Mo-C(31) ) 1.960(13), Ge-C(1) ) 1.933-
(7), C(30)-O(1) ) 1.165(10), C(31)-O(2) ) 1.174(13), Mo-Ge-
C(1) ) 172.2(2)°, Ge-Mo-C(30) ) 88.2(2), Ge-Mo-C(31) )
86.6(3), Mo-C(30)-O(1) ) 177.2(7), Mo-C(31)-O(2) ) 173.8(9),
Ge-C(1)-C(2) ) 120.6(5), Ge-C(1)-C(6) ) 117.9(6).
The compound (1) was synthesized7 in THF solution by
treatment of Na[Mo(η5-C5H5)(CO)3] with 2,6-Mes2C6H3GeCl
(generated in situ) as shown in eq 1
characterization. The X-ray crystal structure8 (Figure 1) reveals
an almost linear coordination (Mo-Ge-C ) 172.2(2)°) at the
germanium and a short Mo-Ge bond length of 2.271(1) Å.
There are no other close interatomic contacts involving germa-
nium, and the shortest GesCO distances are greater than 2.9
Å. Thus, the carbonyls are terminal and not semibridging as
they are in the related dimer [Mo(η5-C5H5)(CO)2]2,9 which fea-
tures Mo-Mo triple bonds. The Mo-Ge distance may be com-
pared to the single bond length (2.62 Å) predicted from the
sum of the covalent radii10 of Mo (1.4 Å) and Ge (1.22 Å) and,
in addition, the Mo-Ge single bond lengths in (η5-C5H5)(CO)2-
Mo(GePh3){C(OEt)Ph}11 (2.658(2) Å) and (η5-C5H5)(η3-C6H11)-
Na[Mo(η5-C5H5)(CO)3] + 2,6-Mes2C6H3GeCl THF, 50 °C8
-CO
(η5-C5H5)(CO)2MoGeC6H3-2,6-Mes2 + NaCl (1)
(1)
The formula of 1 was established by spectroscopic and structural
(1) Cotton, F. A.; Walton, R. A. Multiple Bonds between Metal Atoms,
2nd ed.; Clarendon, Oxford, 1993. Chisholm, M. H. Acc. Chem. Res. 1990,
23, 419.
(2) Fischer, H.; Hofmann, P.; Kreissl, F. R.; Schrock, R. R.; Schubert,
U.; Weiss, K. Carbyne Complexes; VCH: Weinheim, Germany, 1988.
(3) (a) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds: The
Chemistry of Transition Metal Complexes Containing Oxo, Nitrido, Imido
Alkylidene or Alkylidyne Ligands; Wiley: New York, 1988. (b) Scheer,
M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1987.
12
(NO)MoGePh3 (2.604(2) Å). Clearly, the shortening13 seen
in 1 is of the order of 0.35 Å and is consistent with the presence
of a Mo-Ge triple bond between the 15-electron (η5-C5H5)(CO)2-
Mo fragment and the GeC6H3-2,6-Mes2 moiety.
Most of the remaining structural features of the molecule are
not unusual and are consistent with previously published data.
The Mo-CO bonds 1.950(9) and 1.960(10) Å are slightly (ca.
0.01 Å) longer than those in the phosphenum ion-Mo complex
(4) Laplaza, C. E.; Davis, W. M.; Cummins, C. C. Angew. Chem., Int.
Ed. Engl. 1995, 34, 2042.
(5) Zanetti, N. C.; Schrock, R. R.; Davis, W. M. Angew. Chem., Int. Ed.
Engl. 1995, 34, 2044.
(6) Grumbine, S. D.; Chadha, R. K.; Tilley, T. D. J. Am. Chem. Soc.
1992, 114, 1518.
(7) (a) All manipulations were carried out under anaerobic and anhydrous
conditions. Na[Mo(η5-C5H5)(CO)3] (2 mmol), prepared in THF solution
(20 mL) by a literature procedure,7b was added by cannula to a rapidly
stirred THF solution (20 mL) of 2,6-Mes2C6H3GeCl, prepared in situ from
2,6-Mes2C6H3Li7c (0.64 g, 2.0 mmol) and GeCl2‚dioxane7d (0.46 g, 2.0
mmol), at room temperature. The solution was heated to ca. 50 °C and
stirred for 2 h. The volatile materials were then removed under reduced
pressure. The dark red residue was extracted with hexane (50 mL) and
filtered through Celite. The filtrate was concentrated to incipient crystal-
lization and stored in a -20 °C freezer for 1 day to give (η5-C5H5)(CO)2-
MoGeC6H3-2,6-Mes2 (1) as red crystals. Yield: 0.41 g, 0.68 mmol, 34%;
mp 165 °C. IR (Nujol, cm-1): 1930, 1872 (CO). UV (λmax, ꢀ: 353 nm,
6400). 1H NMR (C6D6): δ 2.17 (s, 12H, o-CH3), 2.22 (s, 6H, p-CH3),
4.70 (s, 5H, η5-C5H5), 6.86 (d, 2H, JHH ) 7.5 Hz, m-C6H3), 6.92 (s, 4H,
m-Mes), 7.14 (tr, 1H, JHH ) 7.2 Hz, p-C6H3). 13C NMR (C6D6): δ 20.94
(o-CH3), 21.16 (p-CH3), 86.27 (η5-C5H5), 128.13 (m-Mes), 129.26 (m-C6H3),
131.35 (p-C6H3), 135.81 (p-Mes), 137.02 (o-Mes), 138.48 (o-C6H3), 144.35
(i-Mes), 165.03 (i-C6H3), 231.02 (CO). Anal. Calcd for C31H30GeMoO2:
C, 61.73, H, 5.01. Found C, 61.48, H, 4.98. (b) Hayter, R. G. Inorg. Chem.
1963, 2, 1031. (c) Ruhlandt-Senge, K.; Ellison, J. J.; Wehmschulte, R. J.;
Pauer, F.; Power, P. P. J. Am. Chem. Soc. 1993, 115, 11353. (d) Fjelberg,
T.; Haaland, A.; Schilling, B. E. R.; Lappert, M. F.; Thorne, A. J. J. Chem.
Soc., Dalton Trans. 1986, 1551.
(η5-C5H5(CO)2MoPNMe(CH2)2NMe featuring a Mo-P multiple
bond.14 The Mo-C(η5-C5H5) distances are also very similar,
but the Mo-C(25) and C(26) bonds nearest the large -C6H3-
(8) Crystal data for 1 at 130 K with Mo KR (λ ) 0.71073 Å) radiation:
a ) 13.185(3) Å, b ) 14.891(3) Å, c ) 15.576(3) Å, â ) 114.28(3)°, Z )
4, monoclinic, space group P21/n, R1 ) 0.069 for 3698 (I > 2σ(I)) data.
(9) Klinger, R. J.; Butler, W. M.; Curtis, M. D. J. Am. Chem. Soc. 1978,
100, 5034. Morris-Sherwood, B. J.; Powell, C. B.; Hall, M. B. J. Am. Chem.
Soc. 1984, 106, 5079.
(10) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Clarendon,
Oxford, 1984; pp 1279 and 1288.
(11) Chan, L. Y. Y.; Dean, W. K.; Graham, W. A. G. Inorg. Chem.
1977, 16, 1067.
(12) Carre´, F.; Colomer, E.; Corriu, R. J. P.; Vioux, A. Organometallics
1984, 3, 970.
(13) Unfortunately, no molybdenum germylene structures, possessing a
formal Mo-Ge double bond, appear to be available for comparison. For
other transition metal germylene complexes, see: Barrau, J.; Escudie´, J.;
Satge´, J. Chem. ReV. 1990, 90, 283. Jutzi, P.; Schmidt, H.; Neumann, B.;
Stammler, H.-G. Organometallics 1996, 15, 741.
S0002-7863(96)03132-0 CCC: $12.00 © 1996 American Chemical Society

Communications to the Editor
J. Am. Chem. Soc., Vol. 118, No. 47, 1996 11967
2,6-Mes2 group are slightly longer (ca. 0.1 Å) than the others
(Mo-C(27-29)). This is consistent with the greater steric
congestion imposed by the germanium substituent. The Ge-C
bond length, 1.933(7) Å, is at the shorter end of the range of
Ge-C distances,15 perhaps as a result of the approximate sp
hybridization of the Ge-C bonding orbital. There is little
distortion apparent in the geometry of the 2,6-Mes2C6H3-
ligand, and the plane of the central aromatic ring approximately
bisects the angle between the carbonyl groups.
bonding: e.g., 1947 and 1873 cm-1 found for (η5-C5H5)(CO)2-
16b
MoAs(t-Bu)2 or 1920 and 1856 cm-1 for (η5-C5H5)(CO)2-
Mo(NCPh2).16c
The facile synthesis and the stability of 1 may be attributed
to the stabilizing properties of the 2,6-Mes2C6H3- substituent17
which affords the germanium sufficient steric protection and
facilitates the elimination of CO under mild conditions to afford
the Mo-Ge triply bonded product. The complex 1 is unique
not only because it is the first stable transition metal germylyne
complex but also it appears to be the first species in which a
heavier group 14 element forms a triple bond in a compound
that is stable at room temperature. Investigations of the
chemical properties of 1 and the synthesis of related heavier
main group 14 analogues are currently underway.
1
The solution H and 13C NMR spectra of 1 are consistent
with the structure established by X-ray crystallography. No
dynamic behavior could be detected at temperatures as low as
-90 °C. The IR spectrum of 1 (Nujol mull) displayed the
expected two stretching absorptions in the carbonyl region. The
observed stretching frequencies, 1930 and 1872 cm-1, do not
suggest the unusually high π-acceptor properties seen in many
carbynes:2 e.g., 1992 and 1919 cm-1 in Mo(η5-C5H5)-
(CO)2{C(C6H4-2,6-Me2)}.16a Instead the frequencies resemble
those in other (η5-C5H5)(CO)2Mo fragments involved in multiple
Acknowledgment. We thank the National Science Foundation for
financial support.
Supporting Information Available: Tables of data collection
parameters, atom coordinates, bond distances, angles, anisotropic
thermal parameters and hydrogen coordinates (9 pages). See any
current masthead page for ordering and Internet access instructions.
(14) Hutchins, L. D.; Paine, R. T.; Campana, C. F. J. Am. Chem. Soc.
1980, 102, 4521.
JA963132U
(15) Rivie`re, P.; Rivie`re-Baudet, M.; Satge´, J. ComprehensiVe Organo-
metallic Chemistry; Pergamon: Oxford, 1984; Vol. 2, Chapter 10. Glock-
ling, F. Gmelin Handbook of Inorganic Chemistry: Organogermanium
Compounds; Springer: Berlin, 1988, 1989, 1993; Vols. 1-3. Jutzi, P.;
Becker, A.; Leue, C.; Stammler, H.-G.; Neumann, B.; Hursthouse, M. B.;
Karaulov, A. Organometallics 1991, 10, 3838.
(16) (a) Dossett, S. J.; Hill, A. F.; Jeffrey, J. C.; Marken, F.; Sherwood,
P.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1988, 2453. (b) Mahmoud,
K. A.; Rest, A. J.; Luksza, M.; Jo¨rg, K.; Malisch, W. Organometallics 1984,
3, 501. (c) Farmery, K.; Kilner, M.; Midcalf, C. J. Chem. Soc. (A) 1970,
2279.
(17) Du, C. F.; Hart, H.; Ng, K. D. J. Org. Chem. 1986, 51, 3162.