[(2-(Diphenylphosphino)ethyl)cyclopentadienyl]tricarbonylmetalates: Supporting ligands for reactions at group VI metal-copper bonds

Article abstract of DOI:10.1021/om700861r

Salts of [(2-(diphenylphosphino)ethyl)cyclopentadienyl]tricarbonylmetalates react with CuCl to afford useful intermediates that permit installation of phosphines at copper(I), in a rare instance of nucleophilic attack at heterobimetallic M-Cu bonds without concomitant heterolytic cleavage.

Full text of DOI:10.1021/om700861r

Organometallics 2007, 26, 6669–6673
6669
[(2-(Diphenylphosphino)ethyl)cyclopentadienyl]tricarbonylmetalates:
Supporting Ligands for Reactions at Group VI Metal-Copper
Bonds
Paul J. Fischer,*,† Aaron P. Heerboth,† Zoey R. Herm,† and Benjamin E. Kucera‡
Department of Chemistry, Macalester College, Saint Paul, Minnesota 55105-1899, and Department of
Chemistry, X-ray Crystallographic Laboratory, UniVersity of Minnesota,
Minneapolis, Minnesota 55455-0431
ReceiVed August 28, 2007
Salts of [(2-(diphenylphosphino)ethyl)cyclopentadienyl]tricarbonylmetalates react with CuCl to afford
useful intermediates that permit installation of phosphines at copper(I), in a rare instance of nucleophilic
attack at heterobimetallic M-Cu bonds without concomitant heterolytic cleavage.
units due to the high affinity of copper(I) for sulfur, by stepwise
incorporation of neutral and cationic copper(I) fragments into
the edges of these tetrahedral anions.2a,9
Introduction
Heterobimetallic complexes containing transition-metal-
copper(I) bonds are of fundamental organometallic and bioi-
norganic interest. The promise of novel reactivity afforded by
synergistic and cooperative properties of early/late transition-
metal bonds has motivated these studies for catalyst develop-
ment.1 The importance of bimetallic active sites containing
copper in metalloenzymes has stimulated the synthesis of
heterobimetallic model complexes.2 The application of bridging
Two general synthetic strategies have been employed to
establish copper ligand environments in these heterobimetallics.
Either a labile source of Cu(I) (e.g., [Cu(NCCH3)4]+) introduces
the ion to a pre-established tethered coordination environment
in close proximity to a metal or a donor-stabilized copper(I)
halide derivative (e.g., [Cu(PPh3)Cl]4) is used where the donor
ligand remains bound to copper(I) in the resulting heterobime-
tallic. Few examples of ligand substitution at copper that leave
transition-metal-copper bonds intact have been reported in
heterobimetallics. Salts of [Cu(M′(CO)3(η5-Cp))2]- (M′ ) Mo,
W) react with PPh3, [CN]-, and 1,10-phenanthroline, resulting
in [M′(CO)3(η5-Cp)]-via heterolytic M′-Cu cleavage.10 The
lability of Cu(I)-Ge(II) bonds in LMe2CuGe[(NMes)2(CH)2] and
ligands is
a common strategy to stabilize transition-
metal-copper(I) bonds, and these bonds are often imposed by
molecular architecture that places the copper(I) center in close
proximity to the transition metal. Dative metal-copper(I) bonds
have been stabilized by bridging bidentate phosphines,3 2-(N-
diphenylphosphinomethyl-N-cyclohexyl)aminopyridine,4 2-(diphe-
nylphosphino)pyridine,5 and (2-oxazoline-2-ylmethyl)diphe-
nylphosphine6 and thiolates.7 Cotton showed that pendant imino
groups of the deprotonated 2,6-(diphenylimino)piperidine ligand
(DPhIP) create a pocket for copper(I) ion capture with con-
comitant coordination to quadruply bonded dichromium and
dimolybdenum units.8 Thiometalates of molybdenum and
tungsten, [M′O4-nSn]2- (M′ ) Mo, W; n ) 1–4), have been
used extensively for the construction of Mo-Cu and W-Cu
L
Me2CuGe[N(SiMe3)2]2 (LMe2 ) the ꢀ-diketiminate derived
from 2-(2,6-dimethylphenyl)amino-4-(2,6-dimethylphenyl)imino-
2-pentene) toward PPh3-promoted heterolytic cleavage was
exploited by Tolman to afford free germylenes and Cu(I)-PPh3
adducts.11 Substitution at a thiometalate-enforced Mo-Cu bond
was recently reported; [O2MoS2CuCN]2- reacts with KSAr (Ar
) Ph, o-Tol, p-Tol) to afford [O2MoS2CuSAr]2- 2a
The Cu(I)
.
center of the thiolato-bridged [Cp2Ti(µ-SMe)2Cu(CH3CN)2]PF6
reacts with phosphines (L ) PMe3, PCy3) to afford [Cp2Ti(µ-
SMe)2CuL]PF6, but the suggested dative CufTi interaction is
also strictly enforced by the thiolate ligands.7a
* To whom correspondence should be addressed. E-mail: fischer@
macalester.edu.
† Macalester College.
The discovery of a ligand platform that could accommodate
general substitution at M-Cu bonds of heterobimetallics would
permit facile variation of the steric and electronic environment
at the Cu(I) center, a necessary requirement to rationally
‡ University of Minnesota.
(1) Wheatley, N.; Kalak, P. Chem. ReV. 1999, 99, 3379.
(2) (a) Takuma, M.; Ohki, Y.; Tatsumi, K. Inorg. Chem. 2005, 44, 6034.
(b) Guo, J.; Sheng, T.; Zhang, W.; Wu, X.; Lin, P.; Wang, Q.; Lu, J. Inorg.
Chem. 1998, 37, 3689. (c) Lin, P.; Wu, X.; Huang, Q.; Wang, Q.; Sheng,
T.; Zhang, W.; Guo, J.; Lu, J. Inorg. Chem. 1998, 37, 5672.
(3) (a) Xia, B.-H.; Zhang, H.-X.; Che, C.-M.; Leung, K.-H.; Phillips,
D. L.; Zhu, N.; Zhou, Z.-Y. J. Am. Chem. Soc. 2003, 125, 10362. (b)
Braunstein, P.; Knorr, M.; Schubert, U.; Lanfranchi, M.; Tiripicchio, A.
J. Chem. Soc., Dalton Trans. 1991, 1507. (c) Hutton, A. T.; Pringle, P. G.;
Shaw, B. L. Organometallics 1983, 2, 1889. (d) Blagg, A.; Hutton, A. T.;
Shaw, B. L.; Thornton-Pett, M. Inorg. Chim. Acta 1985, 100, L33.
(4) Cui, D.-J.; Li, Q.-S.; Xu, F.-B.; Leng, X.-B.; Zhang, Z.-Z. Orga-
nometallics 2001, 20, 4126.
(8) Cotton, F. A.; Murillo, C. A.; Roy, L. E.; Zhou, H.-C. Inorg. Chem.
2000, 39, 1743.
(9) (a) Klepp, K. O.; Boller, H.; Rahman, A. B. M. S. Inorg. Chim.
Acta 2000, 305, 91. (b) Zhang, C.; Song, Y.; Jin, G.; Fang, G.; Wang, Y.;
Raj, S. S. S.; Fun, H.-K.; Xin, X. J. Chem. Soc., Dalton Trans. 2000, 1317.
(c) Zhang, C.; Song, Y.; Jin, G.; Fang, G.; Wang, Y.; Fun, H.; Xin, X.
Inorg. Chim. Acta 2000, 311, 25. (d) Huang, Q.; Wu, X.; Wang, Q.; Sheng,
T.; Lu, J. Inorg. Chem. 1996, 35, 893. (e) Huang, Q.; Wu, X.; Sheng, T.;
Wang, Q. Polyhedron 1996, 15, 3405. (f) Sécheresse, F.; Bernés, S.; Robert,
F.; Jeannin, Y. J. Chem. Soc., Dalton Trans. 1991, 2875. (g) Potvin, C.;
Manoli, J.-M.; Sécheresse, F.; Marzak, S. Inorg. Chem. 1987, 26, 4370.
(10) Hackett, P.; Manning, A. R. J. Chem. Soc., Dalton Trans. 1975,
1606.
(5) Song-Lin, Li.; Mak, T. C. W.; Zhang, Z.-Z. J. Chem. Soc., Dalton
Trans. 1996, 3475.
(6) Braunstein, P.; Clerc, G.; Morise, X. New J. Chem. 2003, 27, 68.
(7) (a) Wark, T. A.; Stephan, D. W. Inorg. Chem. 1990, 29, 1731. (b)
White, G. S.; Stephan, D. W. Inorg. Chem. 1985, 24, 1499. (c) Dias, A. R.;
Garcia, M. H.; Villa de Brito, M. J.; Galvão, A. J. Organomet. Chem. 2001,
632, 75. (d) Nadasdi, T. T.; Stephan, D. W. Inorg. Chem. 1994, 33, 1532.
(11) York, J. T.; Young, V. G., Jr.; Tolman, W. B. Inorg. Chem. 2006,
45, 4191.
10.1021/om700861r CCC: $37.00
2007 American Chemical Society
Publication on Web 11/27/2007

6670 Organometallics, Vol. 26, No. 26, 2007
Fischer et al.
modulate complex reactivity. Since the most promising hetero-
bimetallic catalyst candidates containing copper(I) feature early
transition metals, the optimum heterodifunctional ligand for
stabilizing M-Cu bonds should combine substituents that form
robust bonds to metals of contrasting hardness. The (2-
(diphenylphosphino)ethyl)cyclopentadienyl (CpPPh) ligand12
seemed ideally suited to this task; η5-Cp forms strong bonds to
early transition metals in a variety of oxidation states, and
phosphines form robust interactions with soft Cu(I) ions. As a
proof of concept for the general viability of this ligand
application, we chose to investigate reactions of CuCl with salts
of [M(CO)3(η5-CpPPh)]- (M ) Cr, Mo, W). Heterobimetallics
with dative d6-d10 M-Cu bonds supported by only weak
semibridging carbonyl interactions have been synthesized with
[M(CO)3(η5-Cp)]-.13 Due to the relatively robust nature of the
M-Cu bonds in these complexes, we hypothesized that ap-
plication of [M(CO)3(η5-CpPPh)]- offered an excellent inaugural
system to explore the possibility of reactions at related dative
M-Cu bonds supported by the CpPPh ligand.
Figure 1. Molecular structure of 1 (50% thermal ellipsoids).
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å)
and angles (deg): Cr-C(1) ) 1.793(3), Cr-C(2) ) 1.801(3),
Cr-C(3) ) 1.805(3), Cr-C(O) (av) ) 1.80(1), Cr-C(4) )
2.257(3), Cr-C(5) ) 2.224(3), Cr-C(6) ) 2.210(3), Cr-C(7) )
2.209(3), Cr-C(8) ) 2.235(3), Cr-C(dienyl) (av) ) 2.23(2),
C(1)-C(O) ) 1.184(4), C(2)-O(2) ) 1.177(4), C(3)-O(3) )
1.176(4), C-O (av) ) 1.179(4); C(1)-Cr(1)-C(2) ) 86.46(14),
C(1)-Cr(1)-Cr(3) ) 85.80(15), C(2)-Cr(1)-C(3) ) 87.65(14),
(O)C-Cr-C(O) (av) ) 87(1), O(1)-C(1)-Cr ) 175.3(3),
O(2)-C(2)-Cr ) 178.2(3), O(3)-C(3)-Cr ) 176.8(3), O-C-Cr
(av) ) 177(1).
Results and Discussion
Synthesis and Characterization of [K(18C6)][M(CO)3(η5-
CpPPh)]. Bullock recently reported that LiCpPPh and
Mo(CO)3(diglyme) react to give Li[Mo(CO)3(η5-CpPPh)], which
was protonated to afford MoH(CO)2(η5:η1-CpPPh).14 This hy-
dride was employed for catalytic hydrogenation of ketones. The
importance of [Mo(CO)3(η5-CpPPh)]- as a catalyst precursor
prompted us to isolate and crystallographically characterize
[K(18C6)][M(CO)3(η5-CpPPh)] (M ) Cr (1), Mo (2), W(3)).15
Reactions of M(CO)3(RCN)3 (M ) Cr, R ) Me; M ) Mo, W,
R ) Et) and KCpPPh, followed by 18C6 complexation, provided
the analytically pure salts 1–3. The three-legged piano-stool
structures of 1–3 are displayed in Figure 1 and Figures S1 and
S2 (Supporting Information), respectively. The η5-CpPPh ring
is oriented such that C(4) nearly eclipses the carbonyl defined
by C(1),16 and the pendant phosphines engage in no significant
interaction with the [K(18C6)] cations. Important average
lengths and angles that define the geometries of the C3V M(CO)3
fragments of 1–3 (M-C(O), C-O, (O)C-M-C(O), O-C-M;
averages given in the captions of Figure 1 and Figures S1 and
S2) are statistically indistinguishable from those of [PPN]-
[M(CO)3(η5-CpN)],17 respectively. The average M-C(dienyl)
lengths of 1-3 (given in the figure captions) are also statistically
identical with the corresponding values of [PPN][M(CO)3(η5-
CpN)], respectively. The potassium of the [K(18C6)] cation
engages in an ion-pairing interaction via the carbonyl ligand
defined by C(1) of 1–3 in the solid state. The K-O(1) distances
in 1–3 (1, 2.910(3) Å; 2, 2.958(3) Å; 3, 2.944(6) Å) are
statistically insignificant from, although slightly longer than, the
average K-O lengths within the [K(18C6)] cations (1, 2.84(4)
Å; 2 and 3, 2.85(4) Å). The essentially linear O(1)-C(1)-M
angles in 1–3 underscore the nearly imperceptible impact of
this interaction on these anions. This interaction is insignificant
in THF and CH3CN on the basis of the ν(CO) IR absorptions
of 1–3, which indicate unperturbed C3V M(CO)3 units in solution.
Reactions at Group VI Metal-Copper(I) Bonds. While
[M(CO)3(η5-Cp)]- instantaneously reduces CuCl to metallic
copper in THF, Na[M(CO)3(η5-CpPPh)] reacts with CuCl in this
solvent, resulting in salt elimination and metal–carbonyl prod-
ucts. Although these isolable bright yellow solids have proved
difficult to characterize, M-Cu bonding is strongly suggested
on the basis of their ν(CO) IR absorptions,18a which are nearly
indistinguishable from those of M{CuPPh3}(CO)3(µ-η5:η1-
CpPPh) (vide infra). The 31P{1H} NMR spectra of these
[M(CO)3(η5-CpPPh]-/CuCl reaction products exhibit two coupled
doublets,18b suggesting two η5-CpPPh phosphines coordinated
to each Cu(I) center, possibly resulting in an oligomeric
structure.18c Single crystals of these apparently amorphous
substances18d could not be obtained, and 1H NMR spectra
suggest fluxional behavior in solution that has been not been
unambiguously characterized. Heterobimetallic oligomers and
polymers containing Cu(I) have been proposed;7d,10 the pro-
pensity of Cu(I) to form aggregates through bridging interactions
has long been known.19 The series of related tetranuclear cyclic
complexes [{(CO)3M(µ,η5-C5H4PPh2)}2M′M′′] (M ) Cr, Mo,
W, M′ ) M′′ ) Ag; M ) Cr, Mo, M′ ) M′′ ) Au; M ) Mo,
M′ ) Ag, M′′ ) Au) have been thoroughly characterized.20
(12) Synthesis of KCpPPh: Graham, T. W.; Llamazares, A.; McDonald,
R.; Cowie, M. Organometallics 1999, 18, 3490.
(13) (a) Carlton, L.; Lindsell, W. E.; McCullough, K. J.; Preston, P. N.
J. Chem. Soc., Dalton Trans. 1984, 1693. (b) Doyle, G.; Eriksen, K. A.;
Van Engen, D. Organometallics 1985, 4, 2201.
(14) Kimmich, B. A. F.; Fagan, P. J.; Hauptman, E.; Marshall, W. J.;
Bullock, R. M. Organometallics 2005, 24, 6220.
(15) 18C6 ) 1,4,7,10,13,16-hexaoxacyclooctadecane.
(16) Drawings illustrating the near eclipse of C(4) and C(1) in 1–3, as
well as angles between planes that quantify the orientation of the Cp rings
relative to the M(CO)3 fragments, are provided in the Supporting Informa-
tion.
These intermediates readily react with phosphines to afford
analytically pure heterobimetallic monomers (Scheme 1); nu-
cleophilic attack occurs at Cu(I) without concomitant M-Cu
cleavage. While this method is seemingly general for tertiary
(17) Fischer, P. J.; Krohn, K. M.; Mwenda, E. T.; Young, V. G., Jr.
Organometallics 2005, 24, 1776. CpN ) (2-(dimethylamino)ethyl)cyclo-
pentadienyl. [PPN]+ ) [N(PPh3)2]+.

Reactions at Group VI Metal–Copper Bonds
Organometallics, Vol. 26, No. 26, 2007 6671
Scheme 1
Scheme 2
Figure 2. Molecular structure of 4 (50% thermal ellipsoids).
Selected bond lengths (Å) and angles (deg): Cr-Cu ) 2.5943(4),
Cr-C(1) ) 1.8384(18), Cr-C(2) ) 1.8285(19), Cr-C(3) )
1.8218(19), Cr-C(O) (av) ) 1.830(8), Cr-C(4) ) 2.2353(17),
Cr-C(5) ) 2.2166(18), Cr-C(6) ) 2.2012(18), Cr-C(7) )
2.2012(18), Cr-C(8) ) 2.2090(18), Cr-C(dienyl) (av) ) 2.21(1),
O(1)-C(1) ) 1.171(2), O(2)-C(2) ) 1.171(2), O(3)-C(3) )
1.161(2), C-O (av) ) 1.168(6), Cu-C(1) ) 2.3156(17), Cu-C(2)
) 2.2585(18), Cu-P(1) ) 2.2427(5), Cu-P(2) ) 2.2533(5);
O(1)-C(1)-Cr ) 172.67(16), O(2)-C(2)-Cr ) 171.38(17),
O(3)-C(3)-Cr)178.45(19),C(3)-Cr-C(1))85.19(8),C(3)-Cr-
C(2) ) 84.12(8), C(1)-Cr-C(2) ) 104.65(8), C(3)-Cr-Cu )
114.48(6), C(1)-Cr-Cu ) 60.15(5), C(2)-Cr-Cu ) 58.39(6),
phosphines, attempts to introduce other nucleophiles have been
unsuccessful. Excess pyridine (10 equiv) and AsPh3 (5 equiv)
(L) were required to obtain analogous M-Cu derivatives in
solution on the basis of IR spectroscopy, but attempts to isolate
these apparent M{CuL}(CO)3(µ-η5:η1-CpPPh) complexes, with
ether extraction of excess L, resulted in quantitative formation
of species spectroscopically identical with those present before
pyridine and AsPh3 addition, respectively. The bridging η5-CpPPh
ligand is apparently unable to support M-Cu bonds of cuprates;
instantaneous heterolytic M-Cu bond cleavage occurs upon
addition of n-butyllithium, [Bu4N][CN], and [PPN]Cl, affording
[M(CO)3(η5-CpPPh)]-. Heterolytic cleavage promoted by [PP-
N]Cl underscores the importance of salt elimination to kineti-
cally stabilize M-Cu bonds. However, these intermediates are
inert toward triflates and tosylates. Although M{Cu(tmeda)}-
(CO)3(η5-Cp) is known,13b analogous reactions of [M(CO)3(η5-
CpN)]- and CuCl were not useful to obtain pure Cu(I)
derivativeswithabridgingη5-CpN ligand.However,M′{CuPPh3}-
(CO)3(µ-η5:η1-CpN) (M ) Cr (13), Mo (14)) were obtained via
[M(CO)3(η5-CpN)]- and [Cu(PPh3)Cl]4 (Scheme 2).21 Com-
plexes 13 and 14 are kinetic products whose solutions deposit
metallic copper. The kinetic stability of these complexes
decreases down the triad with increasing [M(CO)3(η5-CpN)]-
reducing ability; the analogous W-Cu derivative could not be
isolated without significant precipitation of copper metal.
Solutions of 4–12 are stable indefinitely toward this decomposi-
tion pathway.
P(1)-Cu-P(2)
) 121.07(2), P(1)-Cu-Cr ) 112.057(16),
P(2)-Cu-Cr ) 126.657(17).
are displayed in Figure 2 and Figures S3–S8 (Supporting
Information), respectively. Complexes 4 and 6 are the first
structurally characterized heterobimetallics with only one Cr-Cu
bond (Cr-Cu: 4, 2.5943(4) Å; 6, 2.6092(5) Å).22 These
distances are only slightly shorter than the separation between
Cu(I) and the chromium of the quadruply bonded dichromium
unit in [Cr2Cu2(DPhIP)4](CuCl2)2 (2.628(2) Å).8 The M′-Cu
bonds (M′ ) Mo, W) of 7, 9–11, and 14 range from 2.6423(7)
to 2.7428(5) Å, similar to the corresponding lengths in the
isomers of W{Cu(PPh3)2}(CO)3(η5-Cp) (2.721(1), 2.771(1)
Å),13a Mo{Cu(tmeda)}(CO)3(η5-Cp) (2.592(1) Å)13b and slightly
longer than the Cu-Mo separation (2.6149(4) Å) in
[Mo2Cu2(DPhIP)4](CuCl2)2.8 The P(2)-Cu-M and P(1)-Cu-M
angles are statistically more flexible relative to P(1)-Cu-P(2)
to accommodate phosphines of varying steric bulk in 4, 6, 7,
and 9–11. The P(2)-Cu-M angles in these complexes range
from 125.04(3)° (11) to 135.13(3)° (9) (average 129(4)°), while
the P(1)-Cu-M angles range from 103.19(3)° (9) to 112.057(16)
(4) (average 109(3)°). The average P(1)-Cu-P(2) angle in these
η5-CpPPh complexes is 121(2)°. These complexes permit the
extent of semibridging carbonyl-copper interactions to be
examined with analogues featuring modulated electronic envi-
ronments at Cu(I). The closest such separations (Cu-C(2)) in
7 (2.310(2) Å), 9 (2.338(3) Å), and 10 (2.277(3) Å) only vary
by ∼0.06 Å, despite the varying σ-donor abilities of PMe3, PCy3,
and PPh3, respectively. The corresponding O(2)-C(2)-Mo
angles (7, 172.4(2)°; 9, 171.7(3)°; 10, 172.7(2)°) exhibit only
very small deviations from linearity. These observations are
consistent with molecular orbital calculations by Hall which
indicated that back-donation from Cu(I) to semibridging car-
Characterization of Supported M-Cu Complexes. The
four-legged piano-stool structures of 4, 6, 7, 9–11, and 14
containing substituted η5-Cp ligands and trigonal-planar Cu(I),
(18) (a) IR ν(CO) spectral data for [M(CO)3(η5-CpPPh)]-/CuCl reaction
products in THF: M ) Cr, 1910 (s), 1813 (s), 1779 (s) cm-1; M ) Mo,
1917 (s), 1816 (s), 1786 (s) cm-1; M ) W, 1912 (s), 1810 (s), 1779 cm-1
.
These complexes exhibit nearly indistinguishable IR ν(CO) spectra in
CH3CN. Ambient-temperature THF and CH3CN solutions of these com-
plexes are stable indefinitely under a purified Ar atmosphere. (b) For
example: 31P {1H} NMR (121 MHz) spectral data for the [Mo(CO)3(η5-
CpPPh)]-/CuCl reaction product in C4D8O: δ -3.5 (d, 2JPP ) 130 Hz), -13.8
(d, 2JPP ) 130 Hz). (c) A postulated structure of these products is provided
in the Supporting Information. (d) These bright yellow solids invariably
exhibited a glassy appearance; microcrystalline samples could not be
obtained.
(19) Holleman, A. F.; Wiberg, E. Inorganic Chemistry, 34th ed.;
Academic Press: San Diego, CA, 2001; p 1253.
(20) Poilblanc, R.; Dahan, F.; Brumas-Soula, B. New. J. Chem. 1998,
1067.
(22) Clusters with more than one Cr-Cu bond have been structurally
characterized. For example, see: Klüfers, P.; Wilhelm, U. J. Organomet.
Chem. 1991, 421, 39.
(21) Complexes 6, 10, and 12 can be synthesized via analogous reactions
of [M(CO)3(η5-CpPPh)]- and [Cu(PPh3)Cl]4.

6672 Organometallics, Vol. 26, No. 26, 2007
Fischer et al.
Cr{CuPMe3}(CO)3(µ-η5:η1-CpPPh) (4). THF (50 mL) was
added to Cr(CO)3(CH3CN)3 (0.345 g, 1.33 mmol) and NaCpPPh
(0.400 g, 1.33 mmol); the yellow solution was refluxed for 1 h.
This solution was added to solid CuCl (0.132 g, 1.33 mmol); the
[Cr(CO)3(η5-CpPPh)]- was consumed within 30 min. A 1.0 M
solution of PMe3 in THF (1.4 mL, containing 0.11 g, 1.4 mmol of
PMe3) was added; the resulting yellow solution was stirred for 30
min prior to filtration through alumina. The filtrate was concentrated
in vacuo until ∼2 mL remained. Addition of pentane (50 mL)
resulted in the precipitation of a bright yellow solid that was isolated
by filtration, washed with pentane (4 × 10 mL), and dried in vacuo.
Recrystallization from THF/pentane provided bright yellow, mod-
erately air sensitive microcrystals (0.400 g, 61%). Anal. Calcd for
C25H27O3P2CrCu: C, 54.30; H, 4.92. Found: C, 54.29; H, 5.19. Mp:
176–179 °C dec. IR (THF): ν(CO) 1905 (s), 1808 (s), 1771 (s)
cm-1. IR (Nujol): ν(CO) 1902 (s), 1797 (s), 1759 (s), 1709 (s, sh)
bonyls of the Mo(CO)3(η5-Cp) fragment was very small.23 This
electronic insulation between Cu(I) and the Mo(CO)3(η5-Cp)
fragment is further supported on the basis of ν(CO) IR spectral
data, as the lowest energy ν(CO) absorptions of 7, 9, and 10
only vary by 5 cm-1
.
Concluding Remarks. The discovery of new ligand plat-
forms that support transition-metal-copper bonds has provided
opportunities for new synthetic and catalytic investigations. The
η5-CpPPh ligand simultaneously offers binding sites appropriate
for essentially all transition metals (Cp) and soft Cu(I) ions
(tethered 2-(diphenylphosphino)ethyl group). This ligand suf-
ficiently stabilizes group VI metal-copper bonds to permit rare
nucleophilic attack at Cu(I) in heterobimetallics without con-
comitant heterolytic M-Cu bond cleavage. Since ligand sub-
stitution is a key step in most stoichiometric and catalytic
organometallic reactions, application of η5-CpPPh may offer
reaction pathways previously inaccessible with M-Cu hetero-
bimetallics. Further studies of transition-metal complexes
containing CpPPh, CpN, and related ligands are underway in this
laboratory.
cm-1 1H NMR (C4D8O, 300 MHz) δ 7.66–7.41 (m, 10H, Ph),
.
4.59 (app t, J ) 2.1 Hz, 2H, Cp), 4.48 (app t, J ) 2.1 Hz, 2H, Cp),
2
2.58–2.44 (m, 4H, CH2CH2), 1.20 (d, JPH ) 6.0 Hz, 9H, CH3).
13C{1H} NMR (C4D8O, 75 MHz): δ 242.6 (s, CO). 31P{1H} NMR
(C4D8O, 121 MHz): δ -11.4 (s, br, PPh2), -38.4 (s, br, PMe3).
Cr{CuPCy3}(CO)3(µ-η5:η1-CpPPh) (5). Yield: 51%. Anal.
Calcd for C40H51O3P2CrCu: C, 63.44; H, 6.79. Found: C, 63.60;
H, 6.68. Mp: 171–172 °C dec. IR (THF): ν(CO) 1904 (s), 1806
(s), 1769 (s) cm-1. IR (Nujol): ν(CO) 1905 (s), 1793 (s), 1754 (s),
1730 (m, sh) cm-1. 1H NMR (C4D8O, 300 MHz): δ 7.64–7.42 (m,
10H, Ph), 4.55 (app t, J ) 2.1 Hz, 2H, Cp), 4.45 (app t, J ) 2.1
Experimental Section
Similar procedures were conducted to synthesize 1–3, 4–12, and
13 and 14, respectively. Representative procedures for 1, 4, and
13 are provided below. General procedures, complete experimental
details for 1, 2, and 5–14, and all 13C NMR spectral data for 1–14
are given in the Supporting Information.
Hz, 2H, Cp), 2.46-2.29 (m, 4H, CH2CH2P), 1.79–1.08 (m, 33H,
3
PCy3). 13C{1H} NMR (C4D8O, 75 MHz): δ 243.8 (app t, JPC
)
)
2.9 Hz, CO). 31P{1H} NMR (C4D8O, 121 MHz): δ 17.3 (d, 2JPP
[K(18C6)][Cr(CO)3(η5-CpPPh)] (1). THF (125 mL) was added
to Cr(CO)3(CH3CN)3 (0.500 g, 1.93 mmol) and KCpPPh (0.732 g,
2.31 mmol). The yellow solution was refluxed for 1.5 h. The
solution was filtered at -10 °C through Celite. The yellow filtrate
was stirred with 18C6 (0.561 g, 2.12 mmol) for 2 h at ambient
temperature prior to filtration through Celite. The THF was removed
in vacuo until ∼5 mL remained. Addition of Et2O (70 mL)
precipitated a pale yellow solid that was washed with Et2O (4 ×
30 mL) and dried in vacuo. Recrystallization (THF/Et2O) provided
pale yellow, air-sensitive microcrystals (1.04 g, 75%). Anal. Calcd
for C34H42CrKO9P: C, 56.97; H, 5.91. Found: C, 57.15; H, 5.96.
2
113 Hz, PPh2), -14.3 (d, JPP ) 113 Hz, PCy3).
Cr{CuPPh3}(CO)3(µ-η5:η1-CpPPh) (6). Yield: 55%. Anal.
Calcd for C40H33O3P2CrCu: C, 65.00; H, 4.50. Found: C, 65.46;
H, 4.91. Mp: 183–184 °C dec. IR (THF): ν(CO) 1905 (s), 1811
(s), 1775 (s) cm-1. IR (Nujol): ν(CO) 1890 (s), 1797 (m, sh), 1765
(s), 1738 (s, sh), 1717 (s, sh) cm-1. 1H NMR (CD2Cl2, 300 MHz):
δ 7.40–7.16 (m, 25H, Ph), 4.70 (app t, J ) 2.1 Hz, 2H, Cp), 4.62
(app t, J ) 2.1 Hz, 2H, Cp), 2.62–2.40 (m, 4H, CH2CH2). 13C{1H}
NMR (CD2Cl2, 75 MHz): δ 242.9 (s, CO). 31P{1H} NMR (CD2Cl2,
2
2
121 MHz): δ 4.8 (d, JPP ) 120 Hz, PPh3), -13.0 (d, JPP ) 120
Mp: 136–137 °C dec. IR (THF): ν(CO) 1890 (s), 1778 (s) cm-1
.
Hz, PPh2).
IR (Nujol): ν(CO) 1879 (s), 1772 (s, sh), 1759 (s) cm-1. 1H NMR
(CD3CN, 300 MHz): δ 7.51–7.33 (m, 10H, Ph), 4.39 (app t, J )
2.1 Hz, 2H, Cp), 4.29 (app t, J ) 2.1 Hz, 2H, Cp), 3.57 (s, 24 H,
18C6), 2.35–2.20 (m, 4H, CH2CH2). 13C{1H} NMR (CD3CN, 75
MHz): δ 246.9 (s, CO). 31P{1H} NMR (CD3CN, 121 MHz): δ
-15.06 (s, PPh2).
Mo{CuPMe3}(CO)3(µ-η5:η1-CpPPh) (7). Yield: 67%. Anal.
Calcd for C25H27O3P2CuMo: C, 50.30; H, 4.56. Found: C, 50.71;
H, 4.54. Mp: 163–164 °C dec. IR (THF): ν(CO) 1914 (s), 1813
(s), 1780 (s) cm-1. IR (Nujol): ν(CO) 1889 (m), 1790 (s), 1762
(s), 1737 (s), 1716 (s) cm-1 1H NMR (C4D8O, 300 MHz): δ
.
7.64–7.40 (m, 10H, Ph), 5.24 (app t, J ) 2.4 Hz, 2H, Cp), 5.04
(app t, J ) 2.4 Hz, 2H, Cp), 2.66–2.46 (m, 4H, CH2CH2), 1.17 (d,
2JPH ) 6.3 Hz, 9H, PMe3). 13C{1H} NMR (C4D8O, 75 MHz): δ
232.4 (s, CO). 31P{1H} NMR (C4D8O, 121 MHz): δ -11.8 (d,
[K(18C6)][Mo(CO)3(η5-CpPPh)] (2). Yield: 64%. Anal. Calcd
for C34H42KMoO9P: C, 53.68; H, 5.57. Found: C, 53.92; H, 5.75.
Mp: 149–152 °C dec. IR (THF): ν(CO) 1894 (s), 1781 (s) cm-1
.
1
IR (Nujol): ν(CO) 1886 (s), 1763 (s) cm-1. H NMR (CD3CN,
300 MHz): δ 7.48–7.33 (m, 10H, Ph), 5.04 (app t, J ) 2.4 Hz, 2H,
Cp), 4.92 (app t, J ) 2.4 Hz, 2H, Cp), 3.56 (s, 24 H, 18C6),
2.32–2.28 (m, 4H, CH2CH2). 13C{1H} NMR (CD3CN, 75 MHz):
δ 236.6 (s, CO). 31P{1H} NMR (CD3CN, 121 MHz): δ -15.06 (s,
PPh2).
2
2JPP ) 100 Hz, PPh2), -37.8 (d, JPP ) 100 Hz, PMe3).
Mo{CuPEt3}(CO)3(µ-η5:η1-CpPPh) (8). Yield: 65%. Anal.
Calcd for C28H33O3P2CuMo: C, 52.63; H, 5.21. Found: C, 52.97;
H, 4.99. Mp: 169–170 °C dec. IR (THF): ν(CO) 1913 (s), 1812
(s), 1779 (s) cm-1. IR (Nujol): ν(CO) 1896 (s), 1792 (s), 1768 (s),
1733 (s), 1717 (s) cm-1. 1H NMR (C4D8O, 300 MHz): δ 7.64–7.38
(m, 10H, Ph), 5.23 (app t, J ) 2.1 Hz, 2H, Cp), 5.04 (app t, J )
[K(18C6)][W(CO)3(η5-CpPPh)] (3). Yield: 67%. Anal. Calcd
for C34H42KO9PW: C, 48.12; H, 4.99. Found: C, 48.33; H, 5.29.
2.1 Hz, 2H, Cp), 2.58–2.42 (m, 4H, CH2CH2), 1.50 (dq, JPH
)
Mp: 156–158 °C dec. IR (THF): ν(CO) 1888 (s), 1777 (s) cm-1
.
14.1 Hz, JHH ) 7.2 Hz, 6H, CH3CH2P), 0.89 (dt, JPH ) 15.3 Hz,
IR (Nujol): ν(CO) 1880 (s), 1766 (s, sh) 1759 (s) cm-1. 1H NMR
(CD3CN, 300 MHz): δ 7.50–7.33 (m, 10H, Ph), 5.07 (app t, J )
2.1 Hz, 2H, Cp), 4.96 (app t, J ) 2.1 Hz, 2H, Cp), 3.57 (s, 24 H,
18C6), 2.43–2.26 (m, 4H, CH2CH2). 13C{1H} NMR (CD3CN, 75
JHH ) 7.5 Hz, 9H, CH3CH2P). 13C{1H} NMR (C4D8O, 75 MHz):
3
3
δ 232.8 (dd, JPC ) 12 Hz, JPC ) 2.4 Hz, CO). 31P{1H} NMR
2
(C4D8O, 121 MHz): δ -5.3 (d, JPP ) 130 Hz, PPh2), -13.3 (d,
2JPP ) 130 Hz, PEt3).
1
MHz): δ 227.4 (s, CO, 183W-13C satellites 228.76, 226.13, JWC
Mo{CuPCy3}CO)3(µ-η5:η1-CpPPh) (9). Yield: 63%. Anal.
Calcd for C40H51O3P2CuMo: C, 59.96; H, 6.42. Found: C, 60.36;
H, 6.23. Mp: 183–184 °C dec. IR (THF): ν(CO) 1912 (s), 1810
(s), 1778 (s) cm-1. IR (Nujol): ν(CO) 1914 (s), 1798 (s), 1763 (s)
) 198 Hz). 31P{1H} NMR (CD3CN, 121 MHz): δ -15.11 (s, PPh2).
(23) Sargent, A. L.; Hall, M. B. J. Am. Chem. Soc. 1989, 111, 1563.

Reactions at Group VI Metal–Copper Bonds
Organometallics, Vol. 26, No. 26, 2007 6673
1
cm-1. H NMR (C4D8O, 300 MHz): δ 7.65–7.40 (m, 10H, Ph),
yellow, moderately air sensitive microcrystals (0.652 g, 61%). Anal.
Calcd for C30H29O3NPCuCr: C, 60.25; H, 4.88; N, 2.34. Found: C,
60.29; H, 4.82; N, 2.40. Mp: 163–164 °C dec. IR (THF): ν(CO)
1906 (s), 1808 (s), 1773 (s) cm-1. IR (Nujol): ν(CO) 1885 (s),
5.20 (app t, J ) 2.1 Hz, 2H, Cp), 5.03 (app t, J ) 2.1 Hz, 2H, Cp),
2.52–2.35 (m, 4H, CH2CH2P), 1.90–1.05 (m, 33H, PCy3). 13C{1H}
3
NMR (C4D8O, 75 MHz): δ 233.7 (app t, JPC ) 3.9 Hz, CO).
31P{1H} NMR (C4D8O, 121 MHz): δ 18.0 (d, 2JPP ) 110 Hz, PPh2),
1
1798 (m), 1791 (m), 1773 (s), 1760 (s) cm-1. H NMR (CD3CN,
2
-15.0 (d, JPP ) 110 Hz, PCy3).
300 MHz): δ 7.50–7.27 (m, 15H, Ph), 4.64 (app t, J ) 2.1 Hz, 2H,
Cp), 4.52 (app t, J ) 2.1 Hz, 2H, Cp), 2.44–2.39 (m, 4H, CH2CH2),
2.19 (s, 6H, CH3). 13C{1H} NMR (CD3CN, 75 MHz): δ 242.5 (s,
CO). 31P{1H} NMR (CD3CN, 121 MHz): δ -1.7 (s, br, PPh3).
Mo{CuPPh3}(CO)3(µ-η5:η1-CpN) (14). Yield: 79%. Anal.
Calcd for C30H29O3NPCuMo: C, 56.12; H, 4.55; N, 2.18. Found:
C, 55.79; H, 4.55; N, 2.06. Mp: 130–131 °C dec. IR (THF): ν(CO)
1914 (s), 1813 (s), 1782 (s) cm-1. IR (Nujol): ν(CO) 1894 (s),
1794 (s), 1766 (s) cm-1. 1H NMR (CD3CN, 300 MHz): δ 7.48–7.24
(m, 15H, Ph), 5.23 (app t, J ) 2.1 Hz, 2H, Cp), 5.07 (app t, J )
2.1 Hz, 2H, Cp), 2.50 – 2.35 (m, 4H, CH2CH2), 2.17 (s, 6H, CH3).
13C{1H} NMR (CD3CN, 75 MHz): d 232.6 (s, CO). 31P{1H} NMR
(CD3CN, 121 MHz): δ 4.3 (s, br, PPh3).
Mo{CuPPh3}(CO)3(µ-η5:η1-CpPPh) (10). Yield: 74%. Anal.
Calcd for C40H33O3P2CuMo: C, 61.35; H, 4.25. Found: C, 61.56;
H, 4.48. Mp: 191–192 °C dec. IR (THF): ν(CO) 1916 (s), 1815
(s), 1783 (s) cm-1. IR (Nujol): ν(CO) 1897 (s), 1801 (s, sh), 1773
(s), 1717 (s, sh) cm-1. 1H NMR (CD2Cl2, 300 MHz): δ 7.37–7.17
(m, 25H, Ph), 5.32 (app t, J ) 2.1 Hz, 2H, Cp), 5.16 (app t, J )
2.1 Hz, 2H, Cp), 2.64–2.42 (m, 4H, CH2CH2). 13C{1H} NMR
(CD2Cl2, 75 MHz): δ 233.1 (s, CO). 31P{1H} NMR (CD2Cl2, 121
2
2
MHz): δ 5.1 (d, JPP ) 119 Hz, PPh3), -13.5 (d, JPP ) 119 Hz,
PPh2).
W{CuPMe3}(CO)3(µ-η5:η1-CpPPh) (11). Yield: 46%. Anal.
Calcd for C25H27O3P2CuW: C, 43.85; H, 3.97. Found: C, 44.27;
H, 3.99. Mp: 188–189 °C dec. IR (THF): ν(CO) 1909 (s), 1808
(s), 1774 (s) cm-1. IR (Nujol): ν(CO) 1892 (s), 1786 (s), 1757 (s)
X-ray Crystallographic Characterization of 1–4, 6, 7, 9–
11, and 14. X-ray-quality crystals of 1, 3, 4, 6, 7, 10, 11, and 14
were obtained by diffusion of pentane into a THF solution of each
compound. Crystals of 2 were obtained by diffusion of Et2O into
a THF solution of the compound. Crystals of 9 were obtained by
diffusion of pentane into a Et2O/THF solution of the compound.
These crystals were selected from the mother liquor in a N2-filled
glovebag.
1
cm-1. H NMR (C4D8O, 300 MHz): δ 7.64–7.42 (m, 10H, Ph),
5.30 (app t, J ) 2.1 Hz, 2H, Cp), 5.08 (app t, J ) 2.1, 2H, Cp),
2
2.74–2.47 (m, 4H, CH2CH2), 1.18 (d, JPH ) 6.0 Hz, 9H, PMe3).
13C{1H} NMR (C4D8O, 75 MHz): δ 222.6 (s, CO, 183W-13C
satellites 223.78, 221.41, JWC ) 178 Hz). 31P{1H} NMR (C4D8O,
121 MHz): δ -8.8 (d, 2JPP ) 108 Hz, PPh2), -35.3 (d, 2JPP ) 104
Hz, PMe3).
W{CuPPh3}(CO)3(µ-η5:η1-CpPPh) (12). Yield: 71%. Anal.
Calcd for C40H33O3P2CuW: C, 55.15; H, 3.82. Found: C, 55.30;
H, 4.11. Mp: 198–199 °C dec. IR (THF): ν(CO) 1910 (s), 1809
(s), 1777 (s) cm-1. IR (Nujol): ν(CO) 1900 (s), 1777 (s, sh), 1746
(s), 1715 (s, sh) cm-1. 1H NMR (CD2Cl2, 300 MHz): δ 7.40–7.16
(m, 25H, Ph), 5.36 (app t, J ) 2.4 Hz, 2H, Cp), 5.19 (app t, J )
2.4 Hz, 2H, Cp), 2.73–2.41 (m, 4H, CH2CH2). 13C{1H} NMR
(CD2Cl2, 75 MHz): δ 223.6 (s, CO). 31P{1H} NMR (CD2Cl2, 121
Acknowledgment. The donors of the Petroleum Research
Fund, administered by the American Chemical Society (Grant
No. ACS-PRF 46626-B), and an award from Research
Corporation (Grant No. CC5932) supported this research.
We are grateful to these agencies and Macalester College.
We are indebted to Dr. Victor G. Young, Jr. (X-ray
Crystallographic Laboratory). P.J.F. thanks Dr. Letitia Yao
(University of Minnesota) and Dr. John Matachek (Hamline
University) for facilitating 31P NMR access.
2
2
MHz): δ 6.2 (d, JPP ) 121 Hz, PPh3), -10.4 (d, JPP ) 121 Hz,
PPh2).
Cr{CuPPh3}(CO)3(µ-η5:η1-CpN) (13). THF (70 mL) was added
to Cr(CO)3(CH3CN)3 (0.465 g, 1.79 mmol) and NaCpN (0.300 g,
1.88 mmol); the yellow solution was refluxed for 1.5 h. A
suspension of [CuPPh3Cl]4 (0.648 g, 0.449 mmol) in THF (30 mL)
was added; the [Cr(CO)3(η5-CpN)]- was consumed within 20 min.
The resulting yellow solution was filtered through Celite. The filtrate
was concentrated in vacuo until ∼2 mL remained. Addition of
pentane (40 mL) resulted in the precipitation of a pale yellow solid
that was isolated by filtration, washed with pentane (3 × 30 mL),
and dried in vacuo. Recrystallization (THF/Et2O) provided pale
Supporting Information Available: Text, figures, and tables
giving additional experimental details, 13C NMR spectral data, and
crystallographic data as well as data collection, solution, and
refinement information for 1–4 , 6, 7, 9–11, and 14; crystallographic
data are also given as CIF files. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM700861R