Synthesis of and small molecule coordination to highly electrophilic cationic manganese (I) and rhenium(I) carbonyl complexes with tied-back phosphites

Article abstract of DOI:10.1021/om0004693

Formally 16e highly electrophilic fragments [Mn(CO)₄(L)][BAr_F] with a tied-back phosphite (L = P(OCH₂)₃CMe) coordinate Et₂O (5b) or cis-cyclooctene (5c) and are prepared by reaction of the neutral methyl complex Mn(Me)(CO)₄(L) with [H(OEt₂)₂][BAr_F] or [Ph₃C][BAr_F] in the presence of cis-cyclooctene (cco), respectively. The solvent-bound rhenium complexes [Re(CO)₄(L)(CH₂Cl₂)][BAr_F] (6a) and [Re(CO)₃(L)₂(CH₂Cl₂)][BAr _F] (7a) are prepared similarly by reaction of the respective neutral precursors with [Ph₃C][BAr_F] in CH₂Cl₂. The CH₂Cl₂ molecule binds tightly to the Re(I) center and could not be removed under high vacuum for hours. However, the CH₂Cl₂ is readily displaced by Et₂O, cco, and Et₃SiH to afford ether-, olefin-, and silane-coordinated complexes 6b-d and 7b-d, respectively. While the η²-(HSiEt₃)-coordinated 7d is stable in solution at room temperature and is a rare example of an isolable cationic silane complex, the more electrophilic analogue 6d readily decomposes at room temperature to give the hydride-bridged complex {[cis-Re(L)(CO)₄]₂(μ-H)}{BAr_F} (10). Solid-state structures of 5c, 10, and 7b have been determined by single-crystal X-ray structural analysis.

Full text of DOI:10.1021/om0004693

Organometallics 2000, 19, 4141-4149
4141
Syn th esis of a n d Sm a ll Molecu le Coor d in a tion to High ly
Electr op h ilic Ca tion ic Ma n ga n ese(I) a n d Rh en iu m (I)
Ca r bon yl Com p lexes w ith Tied -Ba ck P h osp h ites
Xinggao Fang, Brian L. Scott, Kevin D. J ohn, and Gregory J . Kubas*
Chemistry Division, MS J 514, Los Alamos National Laboratory,
Los Alamos, New Mexico 87545
Received J une 2, 2000
Formally 16e highly electrophilic fragments [Mn(CO)4(L)][BArF] with a tied-back phosphite
(L ) P(OCH2)3CMe) coordinate Et2O (5b) or cis-cyclooctene (5c) and are prepared by reaction
of the neutral methyl complex Mn(Me)(CO)4(L) with [H(OEt2)2][BArF] or [Ph3C][BArF] in
the presence of cis-cyclooctene (cco), respectively. The solvent-bound rhenium complexes [Re-
(CO)4(L)(CH2Cl2)][BArF] (6a ) and [Re(CO)3(L)2(CH2Cl2)][BArF] (7a ) are prepared similarly
by reaction of the respective neutral precursors with [Ph3C][BArF] in CH2Cl2. The CH2Cl2
molecule binds tightly to the Re(I) center and could not be removed under high vacuum for
hours. However, the CH2Cl2 is readily displaced by Et2O, cco, and Et3SiH to afford ether-,
olefin-, and silane-coordinated complexes 6b-d and 7b-d , respectively. While the η2-(H-
SiEt3)-coordinated 7d is stable in solution at room temperature and is a rare example of an
isolable cationic silane complex, the more electrophilic analogue 6d readily decomposes at
room temperature to give the hydride-bridged complex {[cis-Re(L)(CO)4]2(µ-H)}{BArF} (10).
Solid-state structures of 5c, 10, and 7b have been determined by single-crystal X-ray
structural analysis.
In tr od u ction
interactions to the metals that can be displaced by the
H2 ligand. However, other weak ligands such as the
solvent molecules CH2Cl2 and Et2O do not bind, possibly
because of the bulky environment around the metals.
Albertin et al. recently reported the analogous anion-
coordinated phosphite complex 3 and its Re(I) analogue.6
Studies on the coordination and activation of small
molecules such as H2 and silanes onto electrophilic
transition-metal complexes with formally 16e configura-
tions have been an important research theme.1 The
coordination properties of small molecules such as
silanes, olefins, and alkanes are clearly determined by
the subtle balance of the steric and electronic environ-
ments around the metals.2 In particular, we have been
interested in electrophilic Mn(I) complexes such as 13
and 2,4 where the counteranion is the weakly coordinat-
ing BArF (Chart 1).5 In these complexes and their Re(I)
analogues,2b the phosphine ligand exhibits agostic C-H
-
Apparently the anion CF3SO3 binds to the in situ
generated Mn(I) cation, preventing coordination of
neutral solvent molecules. It is reasonable to assume
that the phosphite would exhibit agostic binding to Mn-
(I) if a noncoordinating anion such as BArF were used.
A series of tetracarbonyl complexes of the type [cis-
Mn(CO)4(P)(L′)][BF4] with stronger σ donors L′ such as
H2O, R2S, and NCMe (P ) PR3, PPh(OMe)2) has also
been reported.7 Here the L′ ligands bind to this elec-
trophilic metal cation rather than the BF4, which is a
known coordinating anion.
We felt it was of interest to study metal complexes
based on tied-back phosphites incapable of forming
agostic interactions, thus eliminating competition from
entropically favored intramolecular C-H interactions
for binding of external ligands. This could be very
important for the coordination of weak external ligands
such as alkanes. A 31P NMR handle would still be
retained, along with the steric stabilization provided by
large ligands. Phosphites are also much less basic than
phosphines and are moderate π-acceptors, thus allowing
* To whom correspondence should be addressed. E-mail: kubas@
lanl.gov.
(1) (a) J essop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992, 121,
289. (b) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1992, 32, 789.
(c) Heinekey, D. M.; Oldham, J . W., J r. Chem. Rev. 1993, 93, 913. (d)
Schneider, J . J . Angew. Chem., Int. Ed. Engl. 1996, 35, 1068. (e) Corey,
J . Y.; Braddock-Wilking, J . Chem. Rev. 1999, 99, 175.
(2) For selected recent examples, see: (a) Vigalok, A.; Ben-David,
Y.; Milstein, D. Organometallics 1996, 15, 1839. (b) Heinekey, D. M.;
Radzewich, C. E.; Voges, M. H.; Schomber, B. M. J . Am. Chem. Soc.
1997, 119, 4172. (c) Schlaf, M.; Lough, A. J .; Morris, R. H. Organo-
metallics 1997, 16, 1253. (d) Martelletti, A.; Gramlich, V.; Zurcher,
F.; Mezzetti, A. New J . Chem. 1999, 199. (e) Barthazy, P.; Worle, M.;
Mezzetti, A. J . Am. Chem. Soc. 1999, 121, 480. (f) Albertin, G.;
Antoniutti, S.; Bordignon, E.; Carlon, M. Organometallics 1999, 18,
2052. (g) Becker, T. M.; Krause-Bauer, J . A.; Homrighausen, C. L.;
Orchin, M. Polyhedron 1999, 18, 2563. (h) Butts, M. D.; Kubas, G. J .;
Luo, X.-L.; Bryan, J . C. Inorg. Chem. 1997, 36, 3341. (i) Huhmann-
Vincent, J .; Scott, B. L.; Kubas, G. J . J . Am. Chem. Soc. 1998, 120,
6808. (j) Huhmann-Vincent, J .; Scott, B. L.; Kubas, G. J . Inorg. Chem.
1999, 38, 115. (k) Huhmann-Vincent, J .; Scott, B. L.; Kubas, G. J . Inorg.
Chim. Acta. 1999, 294, 240.
(5) Brookhart, M.; Grant, B.; Volpe, A. F., J r. Organometallics 1992,
11, 3920.
(6) (a) Albertin, G.; Antoniutti, S.; Bettiol, M.; Bordignon, E.;
Busatto, F. Organometallics 1997, 16, 4959. (b) Albertin, G.; Antoniutti,
S.; Garcia-Fontan, S.; Carballo, R.; Padoan, F. J . Chem. Soc., Dalton
Trans. 1998, 2071.
(3) (a) King, W. A.; Luo, X.-L.; Scott, B. L.; Kubas, G. J .; Zilm, D.
W. J . Am. Chem. Soc. 1996, 118, 6782. (b) King, W. A.; Scott, B. L.;
Eckert, J .; Kubas, G. J . Inorg. Chem. 1999, 38, 1069.
(4) Toupadakis, A.; Kubas, G. J .; King, W. A.; Scott, B. L.; Huhmann-
Vincent, J . Organometallics 1998, 17, 5315.
(7) Harris, P. J .; Knox, S. A. R.; McKinney, R. J .; Stone, F. G. A. J .
Chem. Soc., Dalton Trans. 1978, 1009.
10.1021/om0004693 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 09/01/2000

4142 Organometallics, Vol. 19, No. 20, 2000
Fang et al.
Ch a r t 1
Ch a r t 2
the design of highly Lewis acidic centers (“superelec-
trophiles”) to attract the electron density of C-H bonds.
The cationic metal center (with low-interacting anion)
thus could mimic the H+ of a superacid (with similarly
low-interacting anion), and metallocarbocation-like spe-
cies, e.g. [LnMCH4]+, could be isolable. Such transient
species have been implicated in the nonradical mecha-
nisms of oxidase enzymes such as certain methane
monooxygenases (MMO), where M is high-valent Fe-
(IV).8 Furthermore, in LnM(CH4)+ the alkane proton
should become very acidic and the extremely mobile H+
can transfer very rapidly to a nearby cis-ligand or an
external base:
Such heterolytic cleavage of a σ-bonded molecule (H2,
hydrocarbons, etc.) is undoubtedly the key step in many
catalyses, including biocatalytic splitting of H2 in
hydrogenases,2k yet it has not been extensively studied
except for intramolecular proton exchange processes in
MH(η2-H2) systems.
Sch em e 1
We have synthesized the Mn(I) precursor complex 4
with three COand twotied-back phosphites,P(OCH2)3CMe
(L), as ligands and an easily displaceable solvent
molecule, CH2Cl2, as the sixth ligand.9 The phosphite
L originally prepared by Verkade10 is not only a weaker
σ donor and stronger π acceptor than respective phos-
phines but is also more compact, thus affording a more
electrophilic M(I) cationic center with more open space
for the coordination of silanes, olefins, or other sixth
ligands, possibly alkanes.9 Here we wish to report on
the synthesis and small molecule binding properties of
the related five-coordinate fragments 5-7 using the
same phosphite L on Re as well as Mn (Chart 2). 5-7
bind either a solvent molecule or small molecules such
as silanes and olefins, and the counteranion is nonco-
ordinating BArF. There are significant differences in the
stability and stereochemistry of the first-row versus
third-row metal systems, e.g. the cis-phosphite config-
uration in 7 versus trans in 4. The latter relates to the
smaller size of Mn, which would lead to increased steric
repulsions between cis phosphites, which are favored
electronically (Chart 2).
(8) (a) Feig, A. L.; Lippard, S. J . Chem. Rev. 1994, 94, 759. (b)
Valentine, A. M.; Stahl, S. S.; Lippard, S. J . J . Am. Chem. Soc. 1999,
121, 3876. (c) Choi, S.-Y.; Eaton, P. E.; Kopp, D. A.; Lippard, S. J .;
Newcomb, M.; Shen, R. J . Am. Chem. Soc. 1999, 121, 12198.
(9) Fang, X.-G.; Huhmann-Vincent, J .; Scott, B. L.; Kubas, G. J . J .
Organomet. Chem., in press.
Resu lts a n d Discu ssion
[cis-Mn (L)(CO)4(solven t)][BAr F] (5). Derivatives of
complex 5 are prepared in the same manner as that for
(10) Verkade, J . G.; Huttemann, T. J .; Fung, M. K. Inorg. Chem.
1965, 4, 83.

Mn and Re Complexes with Tied-Back Phosphites
Organometallics, Vol. 19, No. 20, 2000 4143
Ta ble 1. IR a n d 31P NMR Sp ectr a l Da ta for
Com p lexes 4-11
31P (CD2Cl2,
room temp; δ)
complex
IR (CD2Cl2; νCO, cm-1
2096 w, 2025 vs, 2004 s
2123 m, 2039 s, 2011 s
2115 m, 2057 s, 2040 s
2139 m, 2049 vs, 2019 s
2131 m, 2033 vs, 2001 s
2130 m, 2056 s, 2042 vs, 2027 s
2088 s, 2025 s, 1991 s
2078 s, 2009 s, 1971 s
)
4a
5b
5c
6a
6b
6c
7a
7b
7c
7d
8
155.2
149.0
151.2
103.9
107.1
98.6
108.1
111.4
102.3
106.6
162.5c
99.8c
97.8
2081 s, 2018 s, 2003 s
2080 s, 2044 s, 2015 s, 1751 mb
2073 m, 1982 s, 1952 s
9
10
11
2090 m, 1986 vs, 1944 s
2132 w, 2115 s, 2047 vs, 2025 s, 2009 s
2035 s, 1964 s, 1915 s
102.4
a
b
CH2Cl2 coordinated.9 Re-H-Si stretch. c Solvent is CDCl3.
the synthesis of 4 as shown in Scheme 1. Reaction of
Mn(CO)5Me11 with 1 equiv of L10 in refluxing toluene
affords the known neutral methyl precursor 8.12 Unfor-
tunately, attempted extraction of the methyl group by
reaction of 8 with [Ph3C][BArF]13 in CH2Cl2 gives only
a mixture of products from which no single compound
could be isolated. It is possible that the expected CH2-
Cl2 complex 5a is not as stable as the analogous CH2-
Cl2-bound 4a , containing two phosphite groups, because
of its more electrophilic nature. However, if the reaction
is carried out in the presence of cis-cyclooctene (cco) at
low temperature, the olefin-bound complex 5c could be
isolated as yellow crystals in 46% yield. In addition, the
methyl group in 8 could be protonated off with H(OEt2)2-
BArF to afford the ether-bound complex 5b as colorless
crystals (Scheme 1). The Et2O and cco molecules in 5b,c
are tightly bound to the Mn(I) center and cannot be
removed under high vacuum for hours. The bound Et2O
has a 1H NMR signal at 3.52 ppm (OCH2) and a 13C
NMR signal at 77.0 ppm (OCH2), both shifted downfield
relative to the free ether (δ 3.27 (OCH2), 65.6 (OCH2)).
This is clearly consistent with the transfer of electron
density from the oxygen atom of the ether to the highly
electrophilic Mn(I). The bound cco molecule has NMR
signals for the olefinic group (δ 4.94 (CH) and 101.8
(CH)) shifted upfield from those of the free cco (δ 5.69
(CH) and 130.2 (CH)), which is quite typical for olefin
bound to a transition metal. The CO stretching frequen-
cies for 5b,c (Table 1) are consistent with electrophilic
metal centers (see below) and are comparable to those
for [Mn(CO)4(H2O){PPh(OMe)2}][BF4].7 P(OR)3 deriva-
tives of the latter could not be isolated, however.
F igu r e 1. Drawing of [cis-Mn(L)(CO)4(cis-cyclooctene)]-
[BArF] (5c) (thermal ellipsoids are drawn at the 35% level).
Selected bond distances (Å) and angles (deg): Mn-C(1),
2.3966(40); Mn-C(2), 2.4032(41); C(1)-C(2), 1.3582(54);
Mn-P, 2.2510(12); Mn-C(11), 1.8277(53); Mn-C(9), 1.8578-
(51); Mn-C(10), 1.8585(52); Mn-C(12), 1.8577(52); C(9)-
Mn-P, 177.80(0.15); C(10)-Mn-C(12), 173.91(0.21).
Ta ble 2. Cr ysta llogr a p h ic Da ta for Com p ou n d s 5c,
10, a n d 7ba
5cb
10c
7bd
empirical
formula
fw
space group
λ (Å)
temp (K)
a (Å)
b (Å)
C49H27BF24
MnO7P
1280.43
P21/n
0.710 73
230(2)
18.1505(9)
14.6079(7)
21.074(1)
90
101.339(1)
90
-
C50H31BF24
-
C49H40BF24-
O10P2Re
1503.76
P1h
0.710 73
203(2)
12.9841(9)
14.202(1)
16.321(1)
91.325(1)
98.447(1)
102.836(2)
2897.8(4)
2
O
14P2Re2
1756.90
C2/c
0.710 73
203(2)
19.707(1)
16.5848(8)
18.538(1)
90
94.600(1)
90
6039.5(5)
4
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
5478.6(5)
4
1.552
Z
Fcalcd (g cm-3
)
1.932
0.4193
1.732
0.2283
µ (cm-1
)
0.0400
final R indices
R1
wR2
0.0602
0.1761
0.0277
0.0811
0.0644
0.1152
R1 ) ∑||Fo| - |Fc||/∑|Fo| and wR2 ) [∑[w(Fo - Fc2)2]/
a
2
∑[w(Fo2)2]]1/2
.
The parameter w ) 1/[σ2(Fo2) + (0.1289P)2]. c The
b
Solid-state structures of 5b,c have been obtained from
single-crystal X-ray structural analysis. While the struc-
ture of 5b is highly disordered, the structure of 5c is
well-determined (Figure 1). The crystallographic data
are listed in Table 2. The complex 5c shows an octahe-
dral structure around Mn(I). The Mn-C(1) and Mn-
C(2) distances are 2.3966(40) and 2.4032(41) Å, respec-
tively. These distances are significantly longer than
those of 2.233 and 2.229 Å found in [Mn2(µ-PPh2CHd
CH2)(CO)7(PEt3)], one of the closest structurally char-
parameter w ) 1/[σ2(Fo2) + (0.0458P)2. The parameter w )
d
1/[σ2(Fo2) + (0.0372P)2].
acterized Mn-olefin analogues in the Cambridge Crys-
tal Structure Database.14 More interestingly, the olefinic
C(1)-C(2) distance of 1.3582(54) Å is very close to the
distance of a free double bond at 1.34 Å. This indicates
there is very little π back-donation from Mn(I) to the
coordinated double bond. Accordingly, the Mn-C(11)
distance trans to the bound cco, 1.8277(53) Å, is shorter
than all other Mn-C distances of Mn-C(9), Mn-C(10),
and Mn-C(12) at 1.8578(51), 1.8585(52), and 1.8577-
(11) Closson, R. D.; Kozikowski, J .; Coffield, T. H. J . Org. Chem.
1957, 22, 598.
(12) Green, M.; Hancock, R. I.; Wood, D. C. J . Chem. Soc. A 1968,
2718.
(13) Bahr, S. R.; Boudjouk, P. J . Org. Chem. 1992, 57, 5545.
(14) Henrick, K.; McPartlin, M.; Iggo, J . A.; Kemball, A. C.; Mays,
M. J .; Raithby, P. R. J . Chem. Soc., Dalton Trans. 1987, 2669.

4144 Organometallics, Vol. 19, No. 20, 2000
Fang et al.
Sch em e 2
Sch em e 3
(52) Å, respectively. The C(9)-Mn-P angle of 177.80-
(0.15)° is almost linear, while the C(10)-Mn-C(12)
angle of 173.91(0.21)° slightly deviates from linearity,
bent away from the bound cco. Another interesting
feature of the structure 5c is that the olefin double bond
is perpendicular to the P-Mn-C(9) axis, even though
a parallel orientation was usually observed in similar
complexes for effective π-bonding between the two
fragments, e.g. ReH3(PMe2Ph)3(η2-C5H8)15a and ReH3-
(C2H4)2(PiPr2Ph)2.15b Apparently the parallel orientation
here would generate an unfavorable steric interaction
of the olefin with the phosphite. Electronically the
phosphite is not a strong donor like a phosphine but is
more like a CO; therefore, there is probably not a strong
electronic preference and even a small steric effect can
dictate the olefin orientation (Table 2 and Figure 1).
[cis-Re(L)(CO)4(solven t)][BAr F ] (6). We hypoth-
esize that the unsuccessful isolation of 5a is due to the
highly electrophilic nature of the Mn(I) complex, which
might cause cleavage of bound CH2Cl2. A Re(I) complex
bound to CH2Cl2 should be more electron-rich and might
be more stable, similar to the analogous phosphine
complex [Re(CO)4(PR3)(CH2Cl2)]+, which can be isolated
but is subject to nucleophilic attack by OEt2 to give {[Re-
(CO)4(PR3)]2(µ-Cl)}+.2j We have thus similarly synthe-
sized the solvent CH2Cl2 bound Re(I) complex 6a
(Scheme 2), which is indeed more stable and is isolated
as brick-shaped light yellow crystals.
In analogy to 4, the CH2Cl2 molecule binds tightly to
the Re(I) center in 6a and could not be removed under
high vacuum for hours. While 6a is not as electrophilic
as the unseen Mn(I) congener, it appears to be more
electrophilic than the Mn(I) complex 4 with two phos-
phites. This is evidenced by the higher νCO (cm -1) values
of 6a at 2139 m, 2049 vs, and 2019 s in comparison to
those of 4 at 2096 w, 2025 vs, and 2004 s (Table 1).
Unfortunately, the X-ray structure of 6a could not be
determined because it is highly disordered.
The bound CH2Cl2 in 6a can readily be displaced by
ether, cco, and silanes to give 6b-d , respectively
(Scheme 3). As observed for the analogous adducts of
5, the NMR signals of bound Et2O, δ 3.99 (OCH2) and
80.2 (OCH2), shift downfield relative to those of free
Et2O; the signals corresponding to the olefinic group of
bound cco at δ 5.15 (CH) and 97.6 (CH) shift upfield in
relation to free cco.
1
The H NMR spectrum of the η2-H-SiEt3 ligand in
6d shows a broad peak at -10.68 ppm, corresponding
to the Si-H proton. This new signal is similar to those
for the silane σ ligands in 4-SiHEt39 and [Re(CO)4(PR3)-
(SiHEt3)]+ 2k detected at low temperature. Similar to
4-SiHEt3, 6d is thermally unstable. Unlike 4-SiHEt3,
which did not yield an isolable complex after decomposi-
tion, 6d decomposes at room temperature within 10 min
to give the hydride-bridged dimer 10, which is isolated
as stable colorless crystals in 36% yield via crystalliza-

Mn and Re Complexes with Tied-Back Phosphites
Organometallics, Vol. 19, No. 20, 2000 4145
Re-H distance demonstrates stronger Re-H bonding,
which is consistent with a more electron deficient Re(I)
cationic center due to the weaker electron donating
ability of phosphite in relation to PPh3. In addition, the
Re1-H-Re1A angle of 156.5° is also significantly larger
than the 124.4° found in the above phosphine analogue.
This structural feature is consistent with a two-electron,
three-atom bonding mode around Re1-H-Re1A (Figure
2).
[fa c-Re(L)2(CO)3(solven t)][BAr F ] (7). Two tied-
back phosphite coordinated Re(I) complexes, analogues
of 4, have also been synthesized, as shown in Scheme
4. The Et2O-bound 7b is prepared by reacting the
neutral precursor 11 with H(OEt2)2BArF in 82% yield.
7b could also be prepared by reaction of 7a with Et2O.
Interestingly, the phosphites in 7 adopt a cis orientation
to each other instead of the trans orientation as found
for the P(OEt)3 analogue {ReH(CO)3[P(OEt3)2]}7 and the
Mn(I) analogue 4. The cis orientation is evidenced by
-1
its CO IR stretching pattern. For instance, νCO (cm
)
of 7a shows three strong adsorption peaks at 2088 s,
2025 s, and 1991 s, which is a typical pattern for this
type of configuration. This cis orientation is likely
determined by a favorable electronic factor without
significant steric interference. On the other hand, for
the Mn(I) complex 4, a cis orientation would cause a
repulsive interaction between the two phosphites be-
cause of the smaller size of Mn(I) in relation to Re(I).
Complex fragment 7 is the least electrophilic among
all four cationic fragments 4-7 in this study, as can be
seen by the IR data in Table 1. However, it still binds
the solvent molecule CH2Cl2 very tightly. The bound
CH2Cl2 cannot be removed under high vacuum for
hours. As usual, the CH2Cl2 can be readily displaced
by Et2O, cco, and Et3SiH to afford 7b-d , respectively
(Scheme 5). In contrast to the previously observed
heterolytic H-Si bond cleavage in 6d , the σ-coordinated
silane in 7d is stable both in the solid state and in
solution, similar to the structurally characterized neu-
tral complex Mo(CO)(η2-H-SiH2Ph)(Et2PC2H4PEt2)2.17
An IR band for the Re-H-Si stretch in 7d is observed
at 1751 cm-1, comparable to that for the Mo complex
(1742 cm-1). The solution 1H NMR spectrum of 7d
suggests that the Si-H binds strongly to the cationic
Re(I) center. The Si-H signal shows a triplet at δ
-10.43 with J PH ) 12.7 Hz. The signal is blanketed by
a Si-H sideband with a J SiH value of 66 Hz, much
smaller than the 177 Hz value found in free Et3SiH,
clearlyindicatingthat the Si-H bond is highlystretched.1e
The solid-state structure of 7d could not be obtained,
because the X-ray structure is highly disordered.
The cis orientation of the two phosphites in 7 is
confirmed by an X-ray single-crystal structure analysis
of 7b (Figure 3). The crystallographic data are listed in
Table 2. The structure adopts an overall octahedral
configuration around Re(I). The Re-O(10) distance is
2.331(81) Å, which is slightly longer than the distance
of 2.254(11) Å found in [Re(CO)4(PPh3)(OEt2)][BArF].2i
The respective Re-P(1) and Re-P(2) distances, 2.3746-
(29) and 2.3816(29) Å, are similar to those found in 10.
The average Re-C distance trans to the phosphite is
1.9824(130) Å, which is longer than the Re-C distance
F igu r e 2. Drawing of {[cis-Re(L)(CO)4]2(µ-H)}{BArF} (10)
(thermal ellipsoids are drawn at the 35% level). Selected
bond distances (Å) and angles (deg): Re(1)-H, 1.7617(185);
Re(1)-C(6), 1.9406(64); Re(1)-C(7), 1.9919(65); Re(1)-C(8),
1.9880(52); Re(1)-P(1), 2.3735(12); Re(1)-H-Re(1A), 156.5;
Re(1)-C(6)-H, 171.64(2.90); H-Re(1)-C(7), 96.09(2.78);
H-Re(1)-C(8), 92.30(0.74); H-Re(1)-C(9), 80.59(2.84);
H-Re(1)-P(1), 85.85.
tion from CH2Cl2/hexane. Heterolytic cleavage of the
Si-H bond presumably occurs as for the phosphine
1
system. The H NMR spectrum of 10 displays a triplet
at δ -18.23 for the µ-H ligand, with a J PH value of 12.2
Hz, comparable to the signals for the phosphine ana-
logues {[Re(CO)4(PR3)]2(µ-H)}+: δ -17.59 (J PH ) 7.8)
for R ) Cy and δ -15.56 (J PH ) 10.0) for R ) Ph.2k GC-
MS analysis of the volatiles of the reaction mixture
shows Et3SiCl and (Et3Si)2O as major components,
indicating solvent CH2Cl2 might attack the highly
activated silicon atom of the bound silane to cause H-Si
cleavage. (Et3Si)2O is presumably generated from the
reaction of Et3SiCl and/or Et3Si+ with adventitious
moisture as for 4-SiHEt3,9 [Re(CO)4(PR3)(SiHEt3)]+,2k
and [CpFe(CO)(PPh3)(SiHR3)]+.16
Single crystals of 10 suitable for X-ray structural
analysis are grown from the solvent mixture CH2Cl2/
hexane at -30 °C, and the solid-state structure is solved
by single-crystal structural analysis (Figure 2). The
crystallographic data are listed in Table 2. The structure
shows the hydrogen atom on the 2-fold rotation axis of
the two Re(I) fragments, where each fragment is octa-
hedral around the Re(I) center. This orientation is in
contrast with that of the PPh3 analogue {[cis-Re(PPh3)-
(CO)4]2(µ-H)}{BArF},2k where the two Re(I) fragments
are located on the same side. The position of the hydride
is refined, and the average Re-H distance is 1.7617-
(185) Å, which is considerably shorter than the 1.91 Å
found in the above phosphine analogue. The shorter
(15) (a) Green, M. A.; Huffman, J . C.; Caulton, K. G.; Rybak, W. K.;
Ziolkowski, J . J . J . Organomet. Chem. 1981, 218, C39. (b) Hazel, N.
J .; Howard, J . A. K.; Spencer, J . L. J . Chem. Soc., Chem. Commun.
1984, 1663.
(16) (a) Scharrer, E.; Chang, S.; Brookhart, M. Organometallics
1995, 14, 5686. (b) Chang, S.; Scharrer, E.; Brookhart, M. J . Mol. Catal.
A 1998, 130, 107.
(17) Luo, X.-L.; Kubas, G. J .; Bryan, J . C.; Burns, C. J .; Unkefer, C.
J . J . Am. Chem. Soc. 1994, 116, 10312.

4146 Organometallics, Vol. 19, No. 20, 2000
Fang et al.
Sch em e 4
Sch em e 5
opposite to the bound ether, 1.8579(142) Å. The P(1)-
Re(1)-P(2) angle is 93.27(10)°, slightly larger than 90°.
The average of the P(1)-Re(1)-C(13) and P(2)-Re(1)-
C(11) angles is 87.94(33)°. The C(14)-O(10)-C(16)
angle, 111.12(1.04)°, is typical of other M-Et2O struc-
tures.18
CO stretching frequencies (Table 1) increase in the order
4 < 5b < 5c, indicating that the electrophilicity of the
Mn(I) center increases in the same order, 4 < 5b < 5c.
The third-row complexes with two phosphites, [Re(L)2-
(CO)3(L′)][BArF] (7), have the least electrophilic centers.
Thus, while 7d (L′ ) η2-H-SiEt3) is stable in solution
at room temperature, the more electrophilic analogue
6d readily heterolytically cleaves the bound silane at
room temperature to give net elimination of SiEt3+ and
formation of 10. The Si center is more electropositive
(δ+) in the tetracarbonyl 6d than in the tricarbonyl 7d .
It is somewhat surprising that 7d is stable, since
isolable cationic silane complexes are very rare because
the Si atom of the Si-H bond is highly activated toward
nucleophilic attack.
Com p a r ison of P h osp h ite to P h osp h in e Com -
p lexes a n d Su m m a r y. The tied-back phosphite com-
plexes are clearly more electrophilic than corresponding
phosphine complexes, including triphenylphosphine
systems. Table 3compares IR data, and in all cases the
νCO values are higher for the phosphite systems, con-
sistent with a more electron-poor metal center (lower
MfCO back-donation). This extends to the hydride-
bridged dinuclear phosphite complex 10, which has a
slightly higher νCO value (10-20 cm-1) than {[cis-Re-
(PR3)(CO)4]2(µ-H)}{BArF}.2k The cationic Re complexes
have higher frequencies than the neutral Re-Me com-
plexes. The Mn complexes have slightly higher νCO
values than the Re analogues because first-row metals
are less electron rich than third-row metals. Thus, the
[Mn(L)(CO)4(L′)][BArF] species 5b (L′ ) Et2O) and 5c
(L′ ) cco) have the most electrophilic metal centers. The
None of these cationic fragments bind N2, as was also
the case for the phosphine fragments [Re(CO)4(PR3)]-
[BArF] and [Mn(CO)3(PR3)2][BArF]. As previously dis-
cussed, there is not enough back-donation from the
metal to N2 to stabilize binding (N2 is a very poor σ
donor, weaker than even CH2Cl2, and relies on good
back-donation to bind to metal centers).4 H2 and σ H-X
bonded ligands in general bind more strongly relative
to N2 as the electrophilicity of the metal center in-
creases. This is important in biological systems such as
hydrogenase enzymes, where H2 preferentially binds to
and is activated on iron centers that, significantly,
(18) (a) Yi, C. S.; Wodka, D.; Rheingold, A. L.; Yap, G. P. A.
Organometallics 1996, 15, 2. (b) Rix, F. C.; Brookhart, M.; White, P.
S. J . Am. Chem. Soc. 1996, 118, 2436. (c) Solari, E.; Musso, F.; Gallo,
E.; Gloriani, C. R. N.; Chiesi-Villa, A.; Rizzoli, C. Organometallics 1995,
14, 2265.

Mn and Re Complexes with Tied-Back Phosphites
Organometallics, Vol. 19, No. 20, 2000 4147
While binding of Et3SiH to 7a affords stable Si-H
σ-coordinated 7d , binding to the more electrophilic 6a
leads to thermally unstable 6d from which the hydride-
bridged dimer 10 forms via heterolytic Si-H cleavage.
It should be noted that in order to observe binding of
extremely weak ligands such as alkanes to these highly
electrophilic 16e metal centers, a ligand system must
be designed such that the resulting complexes are
soluble in hydrocarbons rather than polar solvents.
Another approach would be to sterically protect the
metal with bulky ligands to inhibit coordination of bulky
polar molecules that could be used as the solvent for
cationic complexes. Work in these directions is in
progress in our laboratory.
Exp er im en ta l Section
All manipulations were performed either under a helium
atmosphere in a Vacuum Atmospheres drybox or under an
argon atmosphere using standard Schlenk techniques unless
otherwise specified. Toluene and hexane were purified by
passing through columns of activated alumina and activated
Cu-0226 S copper catalyst (Engelhard), and CH2Cl2 was
distilled under Ar from P2O5. Starting materials (Mn(CO)5Me,11
Re(CO)5Me,19 phosphite,10 and H(Et2O)2BArF5) were prepared
according to literature methods. The reagents used for this
and for other procedures were purchased from Aldrich, Acros,
F igu r e 3. Drawing of [fac-Re(L)2(CO)3(OEt2)][BArF] (7b)
(thermal ellipsoids are drawn at the 35% level). Selected
bond distances (Å) and angles (deg): Re(1)-O(10), 2.2331-
(81); Re(1)-P(1), 2.3746(29); Re(1)-P(2), 2.3816(29); Re-
(1)-C(11), 1.9640(133); Re(1)-C(12), 1.8579(142); O(10)-
C(14), 1.5720(172); O(10)-C(16), 1.4565(177); O(10)-Re(1)-
C(12), 178.40(0.42); C(13)-Re(1)-P(2), 177.40(0.34); P(2)-
Re(1)-P(1), 93.27(0.10); P(2)-Re(1)-C(11), 87.79(0.34);
C(14)-O(10)-C(16), 111.12(1.04).
1
or Strem Chemical Co. and used as received. H, 31P, 13C, and
11B NMR spectra were recorded on a Varian Unity 300
spectrometer with field strengths of 300, 121, 75, and 96 MHz,
respectively. 1H and 13C chemical shifts were referenced to the
residual solvent resonance relative to TMS; 31P and 11B
chemical shifts were referenced to external 85% H3PO4 and
BF3/Et2O, respectively. The BArF peaks are not reported in
the 13C NMR data and are virtually identical with those
previously reported, regardless of the cationic fragment.20
Infrared spectra were recorded on a Nicolet Avator 360 FT-
IR spectrometer. Elemental analyses were performed in house
on a Perkin-Elmer Series II CHNS/O Model 2400 analyzer.
Ta ble 3. Com p a r ison of νCO Va lu es for Tied -Ba ck
P h osp h ite (L) a n d P h osp h in e Com p lexes
complex
ν
CO, cm-1
[Mn(L)(CO)4(Et2O)]+
[Re(L)(CO)4(Et2O)]+
[Re(PPh3)(CO)4(Et2O)]+
[Re(PCy3)(CO)4(Et2O)]+
Re(Me)(L)(CO)4
2123 m, 2039 s, 2011 s
2131 m, 2033 vs, 2001 s
2118 m, 2010 vs, 1988 s
2111 m, 1999 vs, 1974 s
2090 m, 1986 vs, 1944 s
2077 m, 1973 vs, 1935 s
2070 m, 1969 vs, 1924 s
Re(Me)(PPh3)(CO)4
Re(Me)(PCy3)(CO)4
cis-Mn (L)(CO)4(Me) (8). A mixture of Mn(CO)5Me (1.05
g, 5.00 mmol) and L (0.74 g, 2.10 mmol) in toluene (40 mL)
was refluxed for ca. 16 h under an Ar atmosphere. All volatiles
were removed under vacuum to give an off-white solid. The
solid was purified in air by flash silica gel column chromatog-
raphy, with hexane and CH2Cl2 as eluent to give the product
contain CO ligands to increase the electrophilicity of Fe
and also facilitate reversible binding of H2.2k Because
of their strong trans influence, CO ligands almost
invariably weaken the binding of σ ligands such as H2
trans to them because H2 and X-H ligands are good π
acceptors that also need back-donation (though not as
much as N2). Conversely, the binding of normally weak
pure σ donors such as Et2O and CH2Cl2 are greatly
enhanced on electrophilic centers with CO trans to
them. The coordination to the fragments 5-7 and also
[Re(PR3)(CO)4]+ is irreversible, although the more elec-
tron rich species [Mn(PR3)2(CO)3]+ (2) and also 1 do not
bind these ligands. However, the latter have competing
internal agostic C-H interactions that are entropically
favored over weak external ligand binding; therefore,
it is difficult to sort out the effects here. Thus, the tied-
back phosphite ligands that cannot give agostic interac-
tions are clearly advantageous for studying extremely
weak ligand coordination.
1
(1.40 g, 85%) as a white solid. H NMR (CD2Cl2): δ -0.38 (d,
3H, J ) 8.6 Hz), 0.79 (s, 3H), 4.23 (d, 6H, J ) 4.2 Hz). 13C
NMR (CD2Cl2): δ -20.0, 15.4, 76.2. Anal. Calcd for C10H12O7-
PMn: C, 36.36; H, 3.64. Found: C, 36.42; H, 3.84.
Rea ction of 8 w ith [P h 3C][BAr F ]. To a mixture of 8 (4
mg) and [Ph3C][BArF] (24 mg) in a 5 mm NMR tube was added
CD2Cl2 (0.5 mL) at room temperature to afford a yellow
solution. NMR spectra were recorded. 1H NMR (CD2Cl2): δ
0.81 (s, 1.5 H), 0.87 (s, 1.5 H), 4.27 (d, 3H), J ) 4.4 Hz), 4.38
(d, 3H, J ) 4.2 Hz), 7.57 (s, 4H), 7.73 (s, 8H). 31P NMR (CD2-
Cl2): δ 150.0, 156.1.
[cis-Mn (L)(CO)4(Et2O)][BAr F ] (5b). To a mixture of 8
(33.0 mg, 0.10 mmol) and H(Et2O)2BArF (101.2 mg, 0.10 mmol)
was added Et2O (6 mL) at room temperature. The solution was
stirred at room temperature for 30 min, and then hexane (12
mL) was layered on top of Et2O. The mixture was cooled to
-30 °C for ca. 16 h to give 5b (100.0 mg, 80%) as colorless
crystals. 1H NMR (CD2Cl2): δ 0.89 (s, 3H), 1.19 (t, 6H, J )
8.0 Hz), 3.52 (q, 4H, J ) 8.0 Hz), 4.44 (d, 6H, J ) 4.1 Hz),
7.58 (s, 4H), 7.73 (s, 8H). 13C NMR (CD2Cl2): δ 13.1, 15.1, 77.0
In summary, the highly electrophilic cationic Mn(I)
and Re(I) complexes 5-7 with tied-back phosphite
ligands and a noncoordinating BArF anion have been
synthesized. These complexes are more electrophilic and
sterically less congested than the analogous phosphine
complexes, which favors strong binding of weak solvento
ligands, e.g. CH2Cl2 and Et2O, and also cis-cycloolefin.
(19) Beck, W.; Raab, K. Inorg. Synth. 1990, 28, 15.
(20) Butts, M. D.; Scott, B. L.; Kubas, G. J . J . Am. Chem. Soc. 1996,
118, 11831.

4148 Organometallics, Vol. 19, No. 20, 2000
Fang et al.
(OCH2), 77.9 (d, J ) 6.7 Hz). Anal. Calcd for C45H31BF24O8-
PMn: C, 43.13; H, 2.48. Found: C, 43.17; H, 2.49.
atures from -80 °C to room temperature. The NMR spectra
below -40 °C corresponded to that for the sum of the two
reagents, indicating that no reaction occurred. At 0 °C, a new
1H NMR peak at -10.68 ppm (br) as well as a new 31P NMR
signal at 102.5 ppm started to show up. These new NMR
signals were presumably due to the η2-H-SiEt3 σ complex 6d .
As the temperature was raised to 25 °C, the intensity of the
-10.68 ppm signal slowly decreased while the signal corre-
sponding to the hydride complex 10 appeared. The σ-complex
signal disappeared completely within 10 min at 25 °C. Volatiles
of the reaction mixture were subjected to GC-MS detection,
which showed Et3SiCl and (Et3Si)2O as two major components.
fa c-Re(L)2(CO)3Me (11). A mixture of Re(CO)5Me (0.628
g, 2.00 mmol) and L (0.592 g, 4.00 mmol) in toluene (12 mL)
was refluxed for 20 h under an Ar atmosphere to give a
yellowish suspension. Volatiles were then removed, and the
residue was purified by flash silica gel column chromatogra-
phy, with CH2Cl2 as eluent to give 11 (0.690 g, 59%) as a white
[cis-Mn (L)(CO)4(cis-cycloocten e)][BAr F ] (5c). To a solu-
tion of 8 (66.0 mg, 0.20 mmol) and cis-cyclooctene (cco, 0.20
mL, excess) in CH2Cl2 (3 mL) at -78 °C was added [Ph3C]-
[BArF] (221.2 mg, 0.20 mmol) in CH2Cl2 (4 mL). The mixture
was stirred for 40 min at -78 °C and 1 h at room temperature
to give a yellow suspension. The mixture was filtered through
Celite and dried under vacuum to afford a yellow solid residue.
The residue was crystallized from mixed CH2Cl2/toluene/
hexane (8 mL/8 mL/4 mL) at -30 °C to give the product (0.120
1
g, 46%) as yellow crystals. H NMR (CD2Cl2): δ 0.84 (s, 3H),
1.59 (m, 6H), 1.94 (m, 4H), 2.56 (m, 2H), 4.29 (d, 6H, J ) 4.8
Hz), 4.94 (m, 2H), 7.57 (s, 4H), 7.72 (s, 8H). 13C NMR (CD2-
Cl2): δ 14.9, 26.0, 29.9, 31.3, 78.1 (d, J ) 6.6 Hz), 101.8 (CH).
Anal. Calcd for C49H35BF24O7PMn: C, 45.65; H, 2.72. Found:
C, 46.07; H, 2.67.
cis-Re(L)(CO)4Me (9). A mixture of Re(CO)5Me (0.170 g,
0.50 mmol) and L (0.074 g, 0.50 mmol) in toluene (15 mL) was
refluxed for 20 h under an Ar atmosphere to give a yellowish
suspension. Volatiles were then removed, and the residue was
purified by flash silica gel column chromatography, with CH2-
Cl2/hexane (2/1) as eluent to give 9 (0.221 g, 96%) as a white
1
solid. H NMR (CD2Cl2): δ -0.62 (t, 6H, J ) 9.0 Hz), 0.76 (s,
6H), 4.20 (t, 12H, J ) 2.9 Hz). 13C NMR (CD2Cl2): δ -38.2 (d,
J ) 11.1 Hz), 15.8, 32.7, 76.1 (d, J ) 6.5 Hz). Anal. Calcd for
C
14H21O9P2Re: C, 28.91; H, 3.61. Found: C, 28.63; H, 3.74.
[fa c-Re(L)2(CO)3(CH2Cl2)][BAr F ] (7a ). A mixture of 9
1
solid. H NMR (CDCl3): δ -0.38 (d, 3H, J ) 8.6 Hz), 0.83 (s,
(0.0581 g) and [Ph3C][BArF] (0.1106 g) in CH2Cl2 (4 mL) was
stirred at room temperature for 20 min. Hexane (15 mL) was
then layered on top of the CH2Cl2 solution, and the mixture
was cooled at -30 °C to give a yellowish oil. The oil was
triturated with hexane to give 7a (0.1001 g, 66%) as a
yellowish solid. 1H NMR (CD2Cl2): δ 0.85 (s, 6H), 4.34 (t, 12H,
J ) 1.3 Hz), 7.57 (s, 4H), 7.72 (s, 8H). 13C NMR (CD2Cl2): δ
15.5, 77.0. Anal. Calcd for C46H32BCl2F24O9P2Re: C, 36.46; H,
2.11. Found: C, 36.72; H, 2.12.
[fa c-Re(L)2(CO)3(OEt2)][BAr F ] (7b). A mixture of 11
(0.044 g, 0.076 mmol) and H(OEt2)2BArF (0.077 g, 0.076 mmol)
was dissolved in mixed Et2O (1.5 mL) and CH2Cl2 (1.5 mL)
solvents to give a colorless solution. The solution was stirred
at room temperature for 30 min. Volatiles were then removed,
and the resulting residue was crystallized from Et2O/hexane
at room temperature to give 7b (0.090 g, 79%) as brick-shaped
colorless crystals. 1H NMR (CD2Cl2): δ 0.83 (s, 6H), 1.16 (t,
6H, J ) 7.0 Hz, OCH2CH3), 3.93 (q, 4H, J ) 7.0 Hz, OCH2CH3),
4.33 (d, 12H, J ) 1.7 Hz), 7.57 (s, 4H), 7.72 (s, 8H). 13C NMR
(CD2Cl2): δ 13.2, 15.5, 76.8, 78.4 (OCH2CH3). Anal. Calcd for
C49H40BF24O10P2Re: C, 39.12; H, 2.66. Found: C, 39.29; H,
2.83. Complex 7b can also be prepared by addition of Et2O to
complex 7a in CH2Cl2.
3H), 4.24 (d, 6H, J ) 4.6 Hz). 13C NMR (CD2Cl2): δ -38.7 (t,
J ) 4.0 Hz), 15.9, 32.7, 75.8. Anal. Calcd for C10H12O7PRe: C,
26.03; H, 2.60. Found: C, 26.20; H, 2.80.
[cis-Re(L)(CO)4(CH2Cl2)][BAr F ] (6a ). CH2Cl2 (6 mL) was
added to a mixture of 9 (0.139 g, 0.30 mmol) and [Ph3C][BArF]
(0.354 g, 0.32 mmol) to give a yellowish solution. The mixture
was stirred for 20 min at room temperature. Then (Me3Si)2O
(6 mL) was added. The resulting mixture was cooled to -30
°C to give 6a (0.310 g, 74%) as light yellow brick-shaped
1
crystals. H NMR (CDCl3): δ 0.79 (s, 3H), 4.29 (d, 6H, J ) 4.6
Hz), 5.31 (s, 2H, CH2Cl2), 7.54 (s, 4H), 7.70 (s, 8H). 13C NMR
(CD2Cl2): δ 15.1, 77.4 (d, J ) 6.2 Hz). Anal. Calcd for C42H23
-
BCl2F24O7PRe: C, 36.15; H, 1.65. Found: C, 36.71; H, 1.81.
[cis-Re(L)(CO)4(OEt2)][BAr F ] (6b). Et2O (3 mL) was
added to 6a (prepared in situ from 9 (0.037 g, 0.080 mmol) in
CH2Cl2) to give a yellowish solution. Hexane was added, and
the mixture was cooled to -30 °C to give 6b (0.060 g, 54%) as
colorless crystals. 1H NMR (CD2Cl2): δ 0.88 (s, 3H), 1.24 (t,
6H, J ) 7.0 Hz), 3.99 (4H, J ) 7.0 Hz), 4.41 (d, 6H, J ) 4.6
Hz), 7.57 (s, 4H), 7.72 (s, 8H). 13C NMR (CD2Cl2): δ 13.7, 15.4,
77.4 (d, J ) 5.9 Hz), 80.2. Anal. Calcd for C45H31BF24O8PRe:
C, 39.04; H, 2.24. Found: C, 39.22; H, 2.11.
[fa c-Re(L)2(CO)3(cis-cycloocten e)][BAr F ] (7c). cis-Cy-
clooctene (0.15 mL) was added to a solution of 7a (prepared
in situ from 11 (0.0555 g, 0.096 mmol)) in a mixture of PhCl
(2 mL) and toluene (10 mL). CH2Cl2 (1.5 mL) was then added,
followed by hexane. The solution was cooled to -30 °C to give
[cis-R e(L)(CO)4(cis-cyclooct en e)][BAr F ] (6c). cis-Cy-
clooctene (0.15 mL) was added to a solution of 6a (prepared
in situ from 9 (0.042 g, 0.91 mmol) in CH2Cl2 (3 mL) at room
temperature to give a yellow solution. The solution was stirred
for 30 min at room temperature. Hexane (10 mL) was then
added, and the mixture was cooled to -30 °C to give 6c (0.091
1
7c (0.121 g, 82%) as light yellow crystals. H NMR (CD2Cl2):
1
δ 0.80 (s, 6H), 1.55 (m, 6H), 1.82 (m, 2H), 1.99 (m, 2H), 2.68
(dd, 2H, J ) 13.5, 3.4 Hz), 4.30 (t, 12H, J ) 1.4 Hz), 4.86 (t,
2H, J ) 5.6 Hz), 7.58 (s, 4H), 7.74 (s, 8H). 13C NMR (CD2Cl2):
g, 66%) as yellow crystals. H NMR (CD2Cl2): δ 0.82 (s, 3H),
1.57 (m, 6H), 1.90 (m, 2H), 2.14 (m, 2H), 2.71 (d, 2H, J ) 13.1
Hz), 4.33 (d, 6H, J ) 4.4 Hz), 5.15 (m, 2H), 7.58 (s, 4H), 7.74
(s, 8H). 13C NMR (CD2Cl2): δ 15.3, 26.0, 30.7, 32.7, 77.7, 97.6.
Anal. Calcd for C49H35BF24O7PRe: C, 41.44; H, 2.47. Found:
C, 41.58; H, 2.50.
{[cis-Re(L)(CO)4]2(µ-H)}{BAr F } (10). Et3SiH (0.15 mL)
was added to 6a (0.200 g, 0.14 mmol) in CH2Cl2 (4 mL) at room
temperature. The solution was then stirred for 30 min at room
temperature. Hexane was added, and the mixture was cooled
to -30 °C to give 10 (0.091 g, 36%) as colorless crystals. 1H
NMR (CD2Cl2): δ -18.23 (t, 1H, J ) 12.2 Hz), 0.83 (s, 6H),
4.32 (d, 12H, J ) 4.8 Hz), 7.58 (s, 4H), 7.74 (s, 8H). 13C NMR
(CD2Cl2): δ 15.4, 33.3, 77.1 (d, J ) 6.0 Hz). Anal. Calcd for
δ 15.4, 26.0, 30.1, 32.7, 77.0, 93.4. Anal. Calcd for C53H44
-
BF24O9P2Re: C, 41.32; H, 2.86. Found: C, 40.98; H, 2.85.
[fa c-Re(L)2(CO)3(η2-H-SiEt3)][BAr F ] (7d ). Et3SiH (0.15
mL) was added to complex 7a (prepared in situ from complex
11 (0.136 g, 0.234 mmol)) in CH2Cl2 (5 mL) at room temper-
ature to give a colorless solution. The solution was allowed to
stand for 30 min at room temperature; hexane was then added.
The mixture was cooled to -30 °C to give 7d (0.250 g, 69%)
1
as colorless crystals. H NMR (CD2Cl2): δ -10.43 (t, 1H, J PH
) 12.7 Hz, J SiH ) 66 Hz), 0.80 (s, 6H), 1.06 (m, 15H), 4.29 (t,
12H, J ) 1.5 Hz), 7.58 (s, 4H), 7.75 (s, 8H). 13C NMR (CD2-
C
50H31BF24O14P2SiRe: C, 34.17; H, 1.76. Found: C, 34.44; H,
1.67.
In another NMR scale reaction, Et3SiH (3 µL, ca. 2 equiv)
Cl2): δ 6.6, 7.3, 15.4, 33.4, 76.8. Anal. Calcd for C51H46-
BF24O10P2SiRe: C, 39.61; H, 2.98. Found: C, 39.39; H, 2.97.
X-r a y Str u ctu r e Deter m in a tion of 5c, 10, a n d 7b.
Crystals of 5c, 10, and 7b were mounted from a matrix of
mineral oil under argon gas flow. The crystal was immediately
was added to 6a (0.0130 g) in CD2Cl2 (ca. 0.5 mL) in a 5 mm
NMR tube at -78 °C. NMR spectra were recorded at temper-

Mn and Re Complexes with Tied-Back Phosphites
Organometallics, Vol. 19, No. 20, 2000 4149
placed on a Bruker P4/CCD/PC diffractometer and cooled to
203 K using a Bruker LT-2 temperature device. The data were
collected using a sealed, graphite-monochromated Mo KR X-ray
source. A hemisphere of data was collected using a combination
of æ and ω scans, with 30 s frame exposures and 0.3° frame
widths. Data collection and initial indexing and cell refinement
was handled using SMART21 software. Frame integrations and
final cell parameter calculations were carried out using
SAINT22 software. The data were corrected for absorption
using the SADABS23 program. Decay of reflection intensity was
not observed.
The structures were solved in space groups P21/n (5c), C2/c
(10), and P1h (7b) using direct methods and difference Fourier
techniques. The initial solution revealed the majority of all
non-hydrogen atom positions. The remaining atomic positions
were determined from subsequent Fourier synthesis. Hydrogen
atom positions were fixed (C-H ) 0.93 Å for aromatic, 0.96 Å
for methyl, and 0.97 Å for methylene). The hydrogen atoms
were refined using the riding model, with isotropic tempera-
ture factors fixed to 1.5 (methyl) or 1.2 (all other) times the
equivalent isotropic U value of the carbon atom they were
bound to. For structure 5c, due to disorder, several BArF
fluorine and two cco methylene atoms were refined in two half-
occupancy positions. The final refinement included anisotropic
temperature factors on all non-hydrogen atoms and converged
with final residuals of R1 ) 0.0602 and wR2 ) 0.1761. For
structure 10, the bridging hydride position was found on the
difference map and refined with isotropic temperature factors
set to 0.08 Å2. The final refinement included anisotropic
temperature factors on all non-hydrogen atoms and converged
to R1(I > 2σ(Ι)) ) 0.0277 and wR2 ) 0.0811. For structure
7b, the final refinement4 included anisotropic temperature
factors on all non-hydrogen atoms and converged with final
residuals of R1(I > 2σ(I)) ) 0.0644 and wR2 ) 0.1152. For all
complexes, structure solution, refinement, graphics, and cre-
ation of publication materials were performed using SHELXTL
NT.24 Additional details of the data collection and structure
refinement are listed in Table 2.
Ack n ow led gm en t. This work was supported by the
Department of Energy, Office of Basic Energy Sciences,
Chemical Science Division. We thank Dr. J ohn G.
Watkin for many helpful discussions.
Su p p or tin g In for m a tion Ava ila ble: X-ray crystallo-
graphic data for the structures of compounds 5c, 7b, and 10.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(21) SMART, version 4.210; Bruker Analytical X-ray Systems, Inc.,
6300 Enterprise Lane, Madison, WI 53719, 1996.
(22) SAINT, version 4.05; Bruker Analytical X-ray Systems, Inc.,
Madison, WI 53719, 1996.
OM0004693
(23) Sheldrick, G. M. SADABS, first release; University of Go¨ttingen,
Go¨ttingen, Germany.
(24) SHELXTL NT, version 5.10; Bruker Analytical X-ray Instru-
ments, Inc., Madison, WI 53719, 1997.