Group VI metal carbonyl complexes of Bis((diphenylphosphino)methyl) diphenylborate and an assessment of their utility for template ligand syntheses

Article abstract of DOI:10.1021/om5001056

Zerovalent group VI metal chemistry of anionic bis((diphenylphosphino) methyl)diphenylborate (Ph₂BP₂) offers some surprises in comparison to the chemistry of analogous complexes of neutral bidentate phosphines. The enhanced donor abi

Full text of DOI:10.1021/om5001056

Article
pubs.acs.org/Organometallics
Group VI Metal Carbonyl Complexes of
Bis((diphenylphosphino)methyl)diphenylborate and an Assessment
of Their Utility for Template Ligand Syntheses
Paul J. Fischer,* Laura Avena, Trent D. Bohrmann, Michelle C. Neary,† Grace K. Putka,
and Kevin P. Sullivan‡
Department of Chemistry, Macalester College, Saint Paul, Minnesota 55105-1899, United States
S
* Supporting Information
ABSTRACT: Zerovalent group VI metal chemistry of anionic bis-
((diphenylphosphino)methyl)diphenylborate (Ph2BP2) offers some sur-
prises in comparison to the chemistry of analogous complexes of neutral
bidentate phosphines. The enhanced donor ability of Ph2BP2 relative to
related bis-PPh2 ligands is confirmed by IR spectral analysis of
[ASN][M(CO)4(Ph2BP2)] (ASN = 5-azoniaspiro[4.4]nonane; M = Cr,
Mo, W). The mononitriles [ASN][fac-M(CO)3(RCN)(Ph2BP2)] (M = Cr,
R = Me; M = Mo, R = Et; M = W, R = Et) are useful reagents for the
introduction of sulfur dioxide and isocyanides to the π-basic M-
(CO)3(Ph2BP2) fragment. While the fundamental coordination chemistry
of this anionic fragment mostly mirrors that of its conventional neutral
cousins, the electronic impact of Ph2BP2 leads to divergent reactivity in some cases. For example, the sulfur dioxide complexes
[ASN][mer-M(CO)3(SO2)(Ph2BP2)] (M = Mo, W) are unreactive toward CH2N2, dramatically different from the case for mer-
M(CO)3(SO2)(L2) (L2 = dppm, dppe, dppp). The spectral data of [ASN][Mo(CO)3(CNC6H4(2-NH2))(Ph2BP2)] and
[ASN][Mo(CO)3(CNCH2CH2NH2)(Ph2BP2)], salts containing the first anions of 2-aminophenyl isocyanide and 2-aminoethyl
isocyanide, respectively, indicate that the anionic M(CO)3(Ph2BP2) fragment may be more useful than neutral M(CO)3(dppe)
for the π-back-bonding induced stabilization of ligands prepared via template syntheses.
precatalyst [Ph2BP2]Rh(CH3CN)2 for hydroacylation of 4-
methyl-4-pentenal is markedly higher than that of [L2Rh-
(CH3CN)2][PF6] (L2 = dppe, dppp, Ph2SiP2), with [Ph2BP2]-
Rh(CH3CN)2 exhibiting higher activities for this trans-
formation in donor solvents relative to its less tolerant cationic
cousins.5 The impact of the enhanced Ph2BP2 donor capability
on metal complex photophysical properties has motivated
syntheses of Cu(I)6 and Ir(III)7 Ph2BP2 complexes. The
stabilization of coordinatively unsaturated [Ph2BP2]Ru(BQA)
(BQA = bis(8-quinolinyl)amido) highlights the versatility of
Ph2BP2.8 The application of Ph2BP2 to stabilize P(I) centers
within zwitterionic phosphanide metal carbonyl complexes
vitally depends on the anionic borate in the ligand backbone.9
Neutral bidentate phosphines play pivotal roles in low-valent
group VI metal chemistry, with metal-based reactivity often
modulated via introduction of L2 with varying steric and
electronic profiles. In this regard, it is striking that only one
such bis(phosphino)borate complex, [ASN][Mo-
(CO)4(Ph2BP2)] (ASN = 5-azoniaspiro[4.4]nonane), has
been prepared to date.2a While Peters spectroscopically
characterized this salt to support enhanced Ph2BP2 donation
to the Mo(CO)4 fragment relative to dppp and Ph2SiP2,
INTRODUCTION
■
The development of reliable syntheses of a family of
bis(phosphino)borates, ligands similar to conventional neutral
bidentate phosphines yet rendered anionic by virtue of a borate
charge incorporated into the alkyl chain of the ligand backbone,
has expanded the range of steric and electronic properties
offered by readily accessible bidentate phosphines.1 The
prototy pical ligand within this fam ily, bis-
((diphenylphosphino)methyl)diphenylborate, [Ph2B-
(CH2PPh2)2]− (abbreviated as Ph2BP2), has found numerous
applications. The comparison of zwitterionic transition-metal
Ph2BP2 complexes to their cationic analogues (containing, for
example, 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis-
(diphenylphosphino)propane (dppp), or bis-
((diphenylphosphino)methyl)diphenylsilane (Ph2SiP2)) is a
theme of these studies. Zwitterionic charge-neutral [Ph2BP2]-
Pt(Me)(THF) engages benzene C−H activation faster, via an
alternate mechanism, relative to [(dppp)Pt(CH3)(THF)][B-
(C6F5)4].2 The zwitterionic Pd(II) complex [Ph2BP2]Pd(Me)-
(THF) exhibits similar activity toward catalytic copolymeriza-
tion of CO and ethylene to that of [(dppp)Pd(Me)(THF)]-
[B(C6F5)4].3 The related [(Ph2BP2)Pd(THF)2][OTf] activates
the C−H bond adjacent to the nitrogen atom of trialkylamines,
affording η2-iminium complexes; (Ph2SiP2)Pd(OTf)2 affords
similar palladacycles.4 The activity afforded by the Rh(I)
Received: January 28, 2014
Published: February 24, 2014
© 2014 American Chemical Society
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[ASN][Mo(CO)4(Ph2BP2)] X-ray crystallographic character-
ization was not reported. As anionic Ph2BP2 is considered for
group VI metal chemistry applications, further comparisons
between M(CO)4 and related complexes containing conven-
tional neutral bidentate phosphines and Ph2BP2 are necessary.
Herein we report complete synthesis and characterization
details for [ASN][M(CO)4(Ph2BP2)] (M = Cr, Mo, W) and
compare these data to those of related M(CO)4L2 complexes.
Metal-template-controlled stabilization of kinetically and
thermodynamically unstable molecules at π-basic M(CO)3L2
(M = Mo, W; L2 = neutral bidentate phosphine) fragments is a
useful synthetic strategy. Schenk prepared mer-M(CO)3L2{η2-
(S,C)-H2CSO2} via reactions of mer-M(CO)3L2(SO2) and
diazomethane; the η2-CH2SO2 sulfene ligand, unknown as a
free species, is stabilized via π back-bonding from the
sufficiently electron rich M(CO)3L2 fragments.10 Hahn
employed the fac-M(CO)3(dppe) fragment to prepare 2-
aminoethyl isocyanide and 2-aminophenyl isocyanide, respec-
tively, both also unknown as free species, as ligands.11 When
they are prepared on M(CO)5 fragments, these isocyanides
spontaneously cyclize by intramolecular nucleophilic attack of
the primary amine at the isocyanide carbon to afford N-
heterocyclic carbene ligands.12 Extensive π back-bonding from
the fac-M(CO)3(dppe) fragment attenuates the susceptibility of
the isocyanide carbon of these 2-amino-functionalized ligands
with respect to intramolecular attack. Bis(phosphino)borates
seem particularly well-suited for metal-template-controlled
stabilization reactions, since template-synthesized ligands are
often increasingly stabilized via stronger donation from the π-
basic metal fragment. To ascertain the utility of Ph2BP2 in
supporting this class of reactions, we have explored the
feasibility of synthesizing group VI metal carbonyl Ph2BP2
complexes containing sulfene, 2-aminophenyl isocyanide, or 2-
aminoethyl isocyanide.
Table 1. Infrared Carbonyl Frequencies for M(CO)4L2 in
Solution
a
M(CO)4L2
ν(CO) (cm−1
2008, 1900, 1880
)
Cr(CO)4(dppe)
Cr(CO)4(dppp)
Cr(CO)4(dppb)
1
2005, 1914, 1885
2005, 1913, 1886
1990, 1921, 1882, 1874
2040, 1956, 1932, 1924, 1900
2030, 1932, 1906
Mo(CO)4(dppe)
Mo(CO)4(dppp)
Mo(CO)4(dppb)
2
2022, 1916, 1900, 1884
2004, 1943, 1886, 1860
2017, 1902, 1878
W(CO)4(dppe)
W(CO)4(dppp)
W(CO)4(dppb)
3
2013, 1914, 1887
2014, 1912, 1888
2000, 1890, 1877, 1855
a
THF solutions of 1−3; CH2Cl2 solutions of other complexes.
singlets for 1−3 in CD2Cl2 (1, δ 47.7; 2, δ 29.1; 3, δ 12.1) are
nearly indistinguishable from those of their M(CO)4(dppb)
analogues in CDCl3 (M = Cr, δ 46.9; M = Mo, δ 29.2; M = W,
δ 12.4).14 The similarity of these resonances is unexpected and
speaks to the unique nature of Ph2BP2, on the basis of the
reported relationship between 31P{1H} NMR chemical shifts
and chelate ring size in bis(diphenylphosphino) M(CO)4
complexes.16 In this regard, the 31P{1H} resonances of 1−3
(with six-membered chelate rings) would be expected to be
upfield from those of their M(CO)3(dppb) analogues (with
seven-membered chelate rings) and most similar to those of
M(CO)4(dppp) (in CDCl3: M = Cr, δ 40.3; M = Mo, δ 22.3;
M = W, δ 0.6).14 Complexes 1−3 were characterized by X-ray
crystallography to examine whether this apparent anomaly
could be rationalized via structural parameters. Thermal
ellipsoid drawings depicting the mildly distorted octahedral
geometries of the metal centers of 1·THF, 2, and 3·THF are
displayed in Figures S1−S3 (Supporting Information),
respectively. It is noteworthy that the chelate bite angles
P(1)−M−P(2) of 1 (88.08(3)°), 2 (86.39(2)°), and 3
(85.68(3)°) are slightly more acute than those defining the
related six-membered chelate rings of Cr(CO)4(dppp)
(89.12(2)°)17 and Mo(CO)4(dppp) (89.74(4)°).18 The bulk
associated with the diphenylborate unit in the Ph2BP2 backbone
(relative to the corresponding methylene unit of dppp)
apparently exerts only a modest compression on this angle.
The significant difference between these angles of 1−3 relative
to those of M(CO)4(dppb) (M = Cr,19 93.29(5)°; M = Mo,18
91.65(4)°; M = W,19 91.75(5)°), with seven-membered
bis(phosphine) chelate rings, suggests that the 31P{1H}
resonances of 1−3 are not similarly related to the P(1)−M−
P(2) angle as proposed in neutral M(CO)4L2 (L2 = dppm
(bis(diphenylphosphino)methane), dppe, dppp, dppb).16 The
molecular structures of 1−3 feature nonbonding metal−boron
separations that range from 4.1 to 4.3 Å.
RESULTS AND DISCUSSION
■
[ASN][M(CO)4(Ph2BP2)]. Straightforward ligand substitu-
tion reactions provided microcrystalline [ASN][M-
(CO)4(Ph2BP2)] (M = Cr (1), Mo (2), W (3)). While
Mo(CO)6 seems to be the optimum precursor for 2, as
reported by Peters,2a the best yields of 1 and 3 were obtained
from M(CO)4(C8H12). Salts 1−3 permit further evaluation of
the electronic and steric impact of anionic Ph2BP2 on the
M(CO)4 fragment of group VI metals relative to conventional
neutral bidentate phosphines.13 The IR ν(CO) spectral data
(Table 1) support enhanced donation of Ph2BP2 toward
M(CO)4 relative to dppe, dppp, and 1,4-bis-
(diphenylphosphino)butane (dppb).14 The highest frequency
CO stretching vibration is considered to be most diagnostic of
relative bidentate ligand donation in M(CO)4L2 complexes.15
These presumed a1 vibrations are significantly shifted to lower
energies in 1−3 (by 14−18 cm−1) in comparison to those of
the corresponding M(CO)4(dppb) complexes. The lowest
energy CO vibrations of 1−3 are similarly red-shifted relative to
those of M(CO)4(dppe), M(CO)4(dppp), and M(CO)4(dppb)
for each metal. Increased electron-releasing character for
Ph2BP2 relative to dppp has also been established via
comparison of IR ν(CO) data for [Ph2BP2]Pt(Me)(CO)
(2094 cm−1) and [(dppp)Pt(Me)(CO)][B(C6F5)4] (2118
cm−1).1 While Ph2BP2 is undoubtedly a stronger donor toward
M(CO)4 fragments relative to dppb, 31P{1H} NMR does not
discriminate among 1−3 and their corresponding M-
(CO)4(dppb) analogues; the chemical shifts of the 31P{1H}
Precursors for Metal-Template-Controlled Ligand
Syntheses. Mononitrile complexes of the general formula
[ASN][M(CO)3(RCN)(Ph2BP2)] were targeted as labile
sources of the anionic M(CO)3(Ph2BP2) fragment. Reactions
of [ASN][Ph2BP2] and M(CO)3(RCN)3 (R = Me, Et) in THF
resulted in mixtures containing the desired complexes and
presumed dinuclear species with μ-Ph2BP2 ligands. Fortunately,
combining these reagents in nitrile solvents resulted in exclusive
formation of yellow microcrystalline [ASN][fac-M-
(CO)3(RCN)(Ph2BP2)] (M = Cr, R = Me (4); M = Mo, R
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Figure 1. Molecular structure of the anion of 5·THF (50% thermal ellipsoids). Selected bond lengths (Å) and angles (deg): Mo−P(1) = 2.5611(6),
Mo−P(2) = 2.5627(6), Mo−C(1) = 1.942(2), Mo−C(2) = 1.956(2), Mo−C(3) = 1.965(2), Mo−N(1) = 2.210(2); P(1)−Mo−P(2) = 85.105(19),
P(2)−Mo−C(3) = 93.10(7), C(3)−Mo−C(1) = 84.11(9), C(1)−Mo−P(1) = 88.22(7), C(2)−Mo−C(3) = 87.36(10), C(2)−Mo−C(1) =
87.70(10), N(1)−Mo−P(2) = 83.92(5), N(1)−Mo−C(3) = 92.64(8), N(1)−Mo−P(1) = 94.91(5), C(2)−Mo−N(1) = 94.73(9), C(2)−Mo−P(1)
= 94.62(7), C(1)−Mo−P(2) = 93.67(7).
= Et (5); M = W, R = Et (6)) in high yields. The IR ν(CO)
and 31P{1H} NMR spectral data of 5 and 6 exhibit the same
trends relative to fac-M(CO)3(EtCN)(dppp) (M = Mo, W)10
as those described above for 1−3 relative to their neutral dppp
analogues. Specifically, the highest and lowest energy ν(CO)
absorptions of 5 and 6 are shifted to lower energies relative to
those of these dppp complexes. The 31P{1H} singlets for 5 (δ
29.1) and 6 (δ 18.7) in CD2Cl2 occur downfield from those of
fac-Mo(CO)3(EtCN)(dppp) (δ 22.0) and fac-W-
(CO)3(EtCN)(dppp) (δ 7.6), respectively, in the same solvent,
and are presumably similar to those of the unreported fac-
M(CO)3(EtCN)(dppb) analogues. Salts 4−6 were character-
ized by X-ray crystallography; thermal ellipsoid drawings of the
mildly distorted octahedral metal centers of the anions of 4, 5·
THF, and 6·THF are displayed in Figure S4 (Supporting
Information), Figure 1, and Figure S5 (Supporting Informa-
tion), respectively. The P(1)−Mo−P(2) chelate bite angles of
4 (86.79(2)°), 5 (85.105(19)°), and 6 (85.23(3)°) are each
slightly more acute (by ∼0.5−1.3°) than the corresponding
angles in 1−3. The anion of 4 joins fac-Cr(CO)3(CH3CN)-
{Ph2PN(iPr)P(Ph)NH(iPr)} as the only other structurally
characterized Cr(CO)3(RCN)L2 (L = phosphine) complex.20
The anions of 5 and 6 exhibit coordination spheres similar to
those of the recently structurally characterized tris-
(diphenylphosphino)methane complexes fac-M(CO)3(EtCN)-
(η2-(Ph2P)3CH) (M = Mo, W).21
W; L2 = bis(phosphine))10 in that the instantaneously formed
facial isomer kinetic products completely rearrange in situ to
the meridional isomer thermodynamic products. No attempts
were made to isolate the facial isomers of 7−9. Exclusive
isolation of meridional isomers was confirmed in solution by
31P{1H} NMR spectroscopy; two doublets (that integrate to a
1:1 ratio) were observed for the diastereotopic Ph2BP2
phosphorus atoms of 7−9. The structures of 8 and 9 were
probed by X-ray crystallography; thermal ellipsoid drawings
that reveal the η1(S) SO2 coordination mode are displayed in
Figure S6 (Supporting Information; 8) and Figure 2 (9),
respectively.22 The slightly distorted octahedral W center of 9
features a P(1)−W−P(2) bite angle of 87.06(6)°; the angle
that deviates most from ideality among the 12 angles that
define the edges of the approximate octahedron is P(1)−W−S
(100.84(2)°), enforced by steric bulk between the SO2 and the
Ph2P(1) fragment. The W−S distance in 9 (2.238(2) Å) is
nearly identical with the W−S distance in mer-W(CO)3(SO2)-
(dppe) (2.258(1) Å).10 While the differing trans influence of
CO relative to that of SO2 was invoked to rationalize the
statistically different W−P distances in mer-W(CO)3(SO2)-
(dppe) (2.525(2), 2.500(1) Å), the corresponding lengths in 9
are statistically indistinguishable (2.5281(19), 2.5252(19) Å).
To confirm the anticipated utility of anionic M-
(CO)3(Ph2BP2) π-basic fragments to coordinate isocyanides
as a prerequisite for metal-template-controlled isocyanide
syntheses, nitrile substitution reactions of 5 and 6 were carried
out to provide yellow microcrystalline [ASN][fac-M-
(CO)3(CNR)(Ph2BP2)] (R = cyclohexyl, M = Mo (10), W
(11); R = 2,6-dimethylphenyl, M = Mo (12), W (13)) in
moderate to high yields (65−86%). These anions are the only
known complexes of general formula M(CO)3(CNR)L2 (R =
cyclohexyl, 2,6-dimethylphenyl; L = phosphine). Solutions of
Salts 4−6 are unsurprisingly excellent sources of the
M(CO)3(Ph2BP2) fragment. Saturation of dichloromethane
solutions of 4−6 with sulfur dioxide results in rapid RCN
displacement and subsequent isomerization, affording orange
[ASN][mer-M(CO)3(SO2)(Ph2BP2)] (M = Cr (7), Mo (8), W
(9)) in moderate (60−75%) yields. These substitution
reactions mirror those of fac-M(CO)3(EtCN)L2 (M = Mo,
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Figure 2. Molecular structure of the anion of 9 (50% thermal
ellipsoids). Selected bond lengths (Å) and angles (deg): W−S =
2.238(2), W−P(1) = 2.5281(19), W−P(2) = 2.5252(19), W−C(1) =
2.033(8), W−C(2) = 2.018(8), W−C(3) = 2.013(7); O(4)−S−O(5)
= 111.7(4), P(1)−W−P(2) = 87.06(6), P(1)−W−C(3) = 82.8(2),
P(2)−W−C(3) = 99.24(19), P(2)−W−C(2) = 85.3(2), P(1)−W−S
= 100.84(7), S−W−C(2) = 88.7(2), S−W−C(3) = 89.9(2), S−W−
C(1) = 87.8(2), C(1)−W−C(2) = 96.9(3), C(2)−W−C(3) =
86.0(3), C(1)−W−P(2) = 83.3(2), C(1)−W−P(1) = 94.7(2).
Figure 3. Molecular structure of the anion of 11·THF with the second
position of the disordered cyclohexyl isocyanide group omitted for
clarity (50% thermal ellipsoids). Selected bond lengths (Å) and angles
(deg): W(1A)−C(1A) = 1.989(4), W(1A)−C(2A) = 1.966(4),
W(1A)−C(3A) = 1.964(4), W(1A)−C(4A) = 2.123(4), W(1A)−
P(1A) = 2.5379(10), W(1A)−P(2A) = 2.5276(10); C(3A)−W(1A)−
C(2A) = 87.00(18), C(3A)−W(1A)−C(1A) = 85.43(16), C(2A)−
W(1A)−C(1A) = 90.63(16), C(3A)−W(1A)−C(4A) = 94.04(16),
C(2A)−W(1A)−C(4A) = 88.87(16), C(3A)−W(1A)−P(2A) =
93.16(12), C(1A)−W(1A)−P(2A) = 92.10(12), C(4A)−W(1A)−
P(2A) = 88.39(10), C(2A)−W(1A)−P(1A) = 94.97(13), C(1A)−
W(1A)−P(1A) = 98.34(11), C(4A)−W(1A)−P(1A) = 82.20(11),
P(2A)−W(1A)−P(1A) = 84.69(3).
10−13 contain exclusively facial isomers on the basis of IR
(ν(CO) and ν(CN)) and NMR spectral data; each complex
exhibits only one singlet (excluding 31P−183W satellites) in its
31P{1H} spectrum in THF (10, δ 30.1; 11, δ 11.0; 12, δ 28.1;
13, δ 10.9). Salts 10 and 11 were characterized by X-ray
crystallography. Isostructural 10·THF and 11·THF each feature
two formula units per asymmetric unit, with noticeable disorder
of the cyclohexyl isocyanide ligand in one anion but not the
other. This disorder was successfully refined into two CNCy
fragments with a relative occupancy of 53:47 for both 10·THF
and 11·THF. Thermal ellipsoid drawings of the anions of 10·
THF and 11·THF with the minor position of the disordered
isocyanide ligands omitted for clarity are displayed in Figure S7
(Supporting Information) and Figure 3, respectively. The
mildly distorted octahedral metal centers of the unique anions
of 10 and 11 within their respective asymmetric units feature
statistically indistinguishable Ph2BP2 chelate bite angles (10A,
84.59(2)°; 10B, 84.53(3)°; 11A, 84.69(3)°; 11B, 84.61(3)°)
that are slightly more acute than those in related 5 and 6.
Similar propionitrile substitution reactions of 5 and 6 with 2-
nitrophenyl isocyanide resulted in [ASN][M-
(CO)3(CNC6H4(2-NO2))(Ph2BP2)] (M = Mo (14), W
(15)) as purple microcrystals. The enhanced π acidity of 2-
nitrophenyl isocyanide relative to 2,6-dimethylphenyl isocya-
nide results in partial isomerization of the facial isomers of 14
and 15 to the corresponding meridional isomers; infrared
spectral data (both ν(CO) and ν(CN)) of reaction mixtures
indicate two isomers in solution immediately after 2-nitro-
phenyl isocyanide addition to facial isomers 5 and 6. These
infrared spectra remain unchanged for at least 16 h at ambient
temperature. While equilibrium is apparently achieved very
quickly at ambient temperature, the influence of temperature
on the equilibria between these geometric isomers of 14 and
15, respectively, has not been investigated. It is noteworthy that
Hahn did not observe analogous isomerization during the
synthesis of M(CO)3(CNC6H4(2-NO2))(dppe) from facial
precursors; only facial 2-nitrophenyl isocyanide complexes were
obtained.11 This difference is likely linked to the stronger donor
ability of Ph2BP2 relative to that of dppe, which may increase
the driving force for placing 2-nitrophenyl isocyanide trans to a
Ph2BP2 phosphorus atom relative to a dppe phosphorus atom.
This fac/mer isomerization is related to that of Mo(CO)3(P-
(OiPr)3)(dppe).23 The 31P{1H} NMR spectra of 14 and 15 in
THF-d8 each exhibit two singlets (excluding 31P−183W satellites)
(14, δ 29.9 (s, fac), 29.0 (s, mer); 15, δ 12.6 (s, fac), 11.9 (s,
mer)) that integrate to fac:mer ratios of approximately 85:15
(14) and 70:30 (15) that remain unchanged for at least 1 week
at ambient temperature. The broader 31P{1H} singlets for these
isomers of 14 and 15, respectively, relative to those of the facial
isomers of 10−13, and no observed doublet of doublets for the
meridional isomers of 14 and 15 suggest fac/mer isomerization
of these 2-nitrophenyl isocyanide complexes in THF with rates
that rival the NMR time scale at ambient temperature.24 The
greater Ph2BP2 donor ability relative to that of dppe is apparent
via comparison of the IR ν(CN) spectral data of 14 (in Nujol;
2049, 2028 cm−1), 15 (in Nujol; 2049, 2028 cm−1), and
M(CO)3(CNC6H4(2-NO2))(dppe) (in KBr; M = Mo, 2063
cm−1; M = W, 2059 cm−1).11
The distorted-octahedral metal centers of the isostructural
facial anions of 14 and 15·CH3CN are displayed as thermal
ellipsoid drawings in Figure 4 and Figure S8 (Supporting
Information), respectively. These are the first anions containing
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at −70 °C as solids; mer-W(CO)3{η2-(S,C)-H2CSO2}-
(dppm) was characterized by X-ray crystallography.10 The
robustness of the metal−sulfene interaction was attributed to
the ability of these mer-M(CO)3L2 fragments to engage the
sulfene ligand in π back-bonding. The inability of the less π-
basic W(CO)4(PR3) fragment to afford sulfene complexes
supports this claim. In this regard, our anionic M-
(CO)3(Ph2BP2) fragments seemed ideal candidates to support
sulfene ligands and perhaps permit the first structural
characterization of a Mo sulfene. Indeed, the IR ν(CO)
absorptions of 8 (in CH2Cl2; 2015 (w), 1982 (w), 1908 (s)
cm−1) and 9 (in CH2Cl2; 2010 (w), 1978 (w), 1896 (s) cm−1)
indicate metal centers more electron rich than in all the mer-
M(CO)3(SO2)(L2) complexes that form stable sulfenes; the
lowest energy IR ν(CO) stretching band within this set of
complexes is in mer-W(CO)3(SO2)(chir) (in CH2Cl2; 2015
(w), 1949 (m), 1916 (s) cm−1).10 Surprisingly, 8 and 9 are
apparently unreactive toward diazomethane. For example,
CH2N2 addition to 9 (5 or 25 equiv), modeled after the
procedure developed by Schenk, resulted in no color change
and spectral identification of 9 as the only carbonyl complex in
solution after extended reaction times. Schenk’s M(CO)3{η2-
(S,C)-H2CSO2}L2 syntheses proceeded essentially instanta-
neously upon CH2N2 addition. The sulfur centers of 8 and 9
are apparently rendered insufficiently electrophilic to react with
the diazomethane; the anionic M(CO)3(Ph2BP2) fragments are
too π basic to permit sulfene ligand formation. The asymmetric
and symmetric IR ν(SO) stretching frequencies (in Nujol) of 8
(1202, 1063 cm−1) and 9 (1199, 1061 cm−1) are red-shifted
relative to the corresponding absorptions of mer-W-
(CO)3(SO2)(dppe) (1224, 1065 cm−1)27 and [CpRu(SO2)-
(dppe)]+ (1296, 1117 cm−1).28 The last two complexes rapidly
react with diazomethane to afford sulfene complexes; the lower
energy ν(SO) stretching frequencies of 8 and 9 are indicative of
less electrophilic η1-SO2 ligands. The inability of Ph2BP2 to
support sulfene complexes analogous to mer-M(CO)3{η2-
(S,C)-H2CSO2}L2 provides a cautionary tale as chemistry
is developed to leverage the enhanced donor capability of this
anionic ligand relative to neutral bidentate phosphines.
Metal-Template-Controlled Stabilization of β-Func-
tionalized Isocyanides. Highly reactive and spectroscopically
unobserved intermediates containing 2-aminoethyl isocyanide
are useful precursors to NH,NH-stabilized N-heterocyclic
carbene complexes.12a,29 Benzannulated N-heterocyclic carbene
ligands are accessible via similarly thermodynamically unstable
2-aminophenyl isocyanide complexes.12b,c,30 Identification of π-
basic metal fragments that stabilize these putative isocyanide
ligands via sufficient π back-bonding to render the isocyanide
carbon resistant to nucleophilic attack by the amino function
informs these studies. To this end, Hahn reported inaugural
examples of isolable 2-aminophenyl isocyanide and 2-amino-
ethyl isocyanide complexes via employment of the M-
(CO)3(dppe) fragment (M = Mo, W).11 The anionic
Mo(CO)3(Ph2BP2) fragment also stabilizes these isocyanides
in [ASN][fac-Mo(CO)3(CNC6H4(2-NH2))(Ph2BP2)] (16)
and [ASN][fac-Mo(CO)3(CNCH2CH2NH2)(Ph2BP2)]
(17).31 Reduction of the nitro function of 14 by Raney
nickel/hydrazine hydrate provides 16 as yellow microcrystals
(Scheme 1). It is noteworthy that the reaction of fac/mer
isomeric mixtures of 14 exclusively affords facial 16.
Propionitrile displacement from 5 by 2-azidoethyl isocyanide
provides [ASN][Mo(CO)3(CNCH2CH2N3)(Ph2BP2)], which
reacts via Staudinger conditions to afford 17 as tan micro-
Figure 4. Molecular structure of the anion of fac-14 (50% thermal
ellipsoids). Selected bond lengths (Å) and angles (deg): Mo−C(1) =
2.023(8), Mo−C(2) = 1.962(6), Mo−C(3) = 1.968(7), Mo−C(4) =
2.052(8), Mo−P(1) = 2.5587(14), Mo−P(2) = 2.5375(14), C(4)−
N(1) = 1.191(9); N(1)−C(4)−Mo = 177.3(5), C(4)−N(1)−C(5) =
176.7(7), C(1)−Mo−C(2) = 85.8(3), C(1)−Mo−C(3) = 91.1(3),
C(2)−Mo−C(3) = 90.2(3), C(2)−Mo−C(4) = 89.7(3), C(3)−Mo−
C(4) = 89.8(3), C(3)−Mo−P(2) = 90.84(19), C(1)−Mo−P(2) =
87.69(18), C(4)−Mo−P(2) = 96.78(17), C(2)−Mo−P(1) = 94.0(2),
C(1)−Mo−P(1) = 98.64(17), C(4)−Mo−P(1) = 80.79(17), P(2)−
Mo−P(1) = 86.05(4).
2-nitrophenyl isocyanide, but the M−CNR distances do not
definitively indicate the greater π basicity of the M-
(CO)3(Ph2BP2) fragment relative to the M(CO)3(dppe)
fragment that is clearly communicated by the IR ν(CN)
spectral data. For example, while the metal−isocyanide carbon
bond length in 14 (2.052(8) Å) is 5.8σ shorter than the
corresponding distance in Mo(CO)3(CNC6H4(2-NO2))(dppe)
(2.098(2) Å) (consistent with the trend predicted on the basis
of more extensive π back-bonding in 14), the isocyanide C−N
bond distance in 14 (1.191(9) Å) is not statistically longer (by
only 2.2σ) than that in Mo(CO)3(CNC6H4(2-NO2))(dppe)
(1.171(2) Å).11 The differences between these metrical
parameters of the tungsten analogues (15, W−C(N) =
2.062(7) Å, C−N = 1.171(9) Å; W(CO)3(CNC6H4(2-
NO2))(dppe), W−C(N) = 2.080(3) Å, C−N = 1.173(4) Å)
are also not statistically significant.11
Metal-Template-Controlled Sulfene Ligand Stabiliza-
tion. Methylene transfer from diazomethane to cationic half-
sandwich ruthenium sulfur dioxide complexes [CpRu-
(R3P)2(η1-SO2)]+ affords the cationic sulfene complexes
[CpRu(R3P)2{η2-(S,C)-H2CSO2}]+, which function as elec-
trophiles to facilitate C−C coupling reactions with enamines
and enolates.25 Schenk showed that neutral mer-Mo-
(CO)3(SO2)(L2) (L2 = dppm, dppe) and mer-W(CO)3(SO2)-
(L2) (L2 = dppm, dppe, dppp, chir26) are sufficiently
electrophilic at sulfur to react with diazomethane to provide
mer-M(CO)3{η2-(S,C)-H2CSO2}L2. These W complexes are
more thermally stable (with decomposition points ranging from
96 to 118 °C) than their Mo analogues, which require storage
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Scheme 1
Figure 5. Molecular structure of the anion of 16·THF (50% thermal
ellipsoids). Selected bond lengths (Å) and angles (deg): Mo−C(1) =
1.998(4), Mo−C(2) = 1.978(5), Mo−C(3) = 1.974(5), Mo−C(4) =
2.101(5), Mo−P(1) = 2.5513(11), Mo−P(2) = 2.5482(11), C(4)−
N(1) = 1.165(5); N(1)−C(4)−Mo = 176.6(4), C(4)−N(1)−C(5) =
175.4(5), C(1)−Mo−C(2) = 88.51(17), C(1)−Mo−C(3) =
88.72(17), C(2)−Mo−C(3) = 92.04(19), C(2)−Mo−C(4) =
89.27(17), C(3)−Mo−C(4) = 90.83(17), C(3)−Mo−P(2) =
93.95(13), C(1)−Mo−P(2) = 82.01(12), C(4)−Mo−P(2) =
100.26(11), C(2)−Mo−P(1) = 90.77(14), C(1)−Mo−P(1) =
95.94(12), C(4)−Mo−P(1) = 84.61(12), P(2)−Mo−P(1) =
84.06(3).
crystals (Scheme 1).32 The extent of π back-bonding into the
isocyanide ligands, on the basis of IR ν(CN) spectral data, is
expectedly greater in 16 (in Nujol; 2069 cm−1) relative to that
in M(CO)3(CN(C6H4(2-NH2))(dppe) (in KBr; M = Mo,
2097 cm−1; M = W, 2093 cm−1) and in 17 (in Nujol, 2116
cm−1) relative to that in M(CO)3(CNCH2CH2NH2)(dppe) (in
KBr; M = Mo, 2133 cm−1; M = W, 2126 cm−1). Formation of
the first anions containing 2-aminophenyl isocyanide and 2-
aminoethyl isocyanide was confirmed by X-ray crystallography;
thermal ellipsoid drawings of the modestly distorted octahedral
Mo centers of the anions of 16·THF and 17 are displayed in
Figures 5 and 6, respectively. The most germane structural
parameters to access the spectroscopically evident increased π
acidity of 2-aminophenyl isocyanide in 16 relative to that in
Mo(CO)3(CN(C6H4(2-NH2))(dppe) are the M−CNR dis-
tances and the CNR angles. The greater donation of Ph2BP2
relative to dppe is manifested by a statistically shorter Mo−
C(4) distance in 16 (2.101(5) Å) relative to that in
Mo(CO)3(CNC6H4(2-NH2))(dppe) (2.129(2) Å). The iso-
cyanide angle in 16 (C(4)−N(1)−C(5) = 175.4(5)°) is
modestly more acute than, but not statistically different from,
the corresponding angle in Mo(CO)3(CNC6H4(2-NH2))-
(dppe) (176.0(2)°). These trends are not internally consistent
upon comparison of 17 to Mo(CO)3(CNCH2CH2NH2)(dppe)
(18). Statistically significant contraction of the Mo−CNR
length in 17 (2.138(4) Å) relative to that in 18 (2.157(2) Å) is
not concomitant with a more acute isocyanide angle in 17
(C(4)−N(1)−C(5) = 178.1(4)°) relative to that in 18
(171.4(4)°). The primacy of IR ν(CN) data relative to these
metric parameters in assessing π back-bonding into isocyanide
ligands has been noted.33 These spectroscopic data are
consistent with both the 2-aminophenyl isocyanide and 2-
aminoethyl isocyanide ligands serving as stronger π-acceptor
ligands in 16 and 17, respectively, relative to their electronic
roles in Hahn’s dppe analogues. An assessment of the
hypothesized lower susceptibilities of the Ph2BP2 complexes
16 and 17 (relative to their dppe complexes) to engage in
intramolecular cyclization reactions to afford N-heterocyclic
carbene complexes would be interesting to explore.
CONCLUSION
■
Anionic bis((diphenylphosphino)methyl)diphenylborate, a
stronger donor relative to bis-PPh2 bidentate phosphines
(dppe, dppp, etc.), seems generally applicable for the syntheses
of more electron rich analogues of group VI metal carbonyl
complexes of these neutral phosphines. While the fundamental
coordination chemistry of Ph2BP2 for the anionic complexes
reported herein predictably mirrors that of their neutral
analogues, the Ph2BP2 electronic impact results in reactivity
not always analogous to that of their neutral cousins.
Application of the π-basic Mo(CO)3(Ph2BP2) fragment
predictably results in an even greater degree of stabilization
of 2-aminophenyl isocyanide (in 16) and 2-aminoethyl
isocyanide (in 17) ligands relative to that provided by the
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(app t, JCP = 4.9 Hz, ortho P(C6H5)2), 128.0 (s, meta B(C6H5)2), 127.4
(app t, JCP = 3.9 Hz, meta P(C6H5)2), 126.3 (s, para P(C6H5)2), 122.1
(s, para B(C6H5)2), 63.8 (s, br, (CH2CH2)2N), 22.5 (s, (CH2CH2)2N)
ppm.
[ASN][Mo(CO)4(Ph2BP2)] (2). Yield: 71%. Anal. Calcd for
C54H58O5BMoNP2 (as a 1:1 THF solvate): C, 66.88; H, 6.03; N,
1.44. Found: C, 66.35; H, 5.88; N, 1.45. Mp: 184−185 °C dec. IR
(THF): ν(CO) 2004 (m), 1943 (w), 1886 (s), 1860 (m) cm−1. IR
(Nujol): ν(CO) 2070 (w), 2001 (s), 1946 (w), 1870 (s), 1835 (s, sh)
cm−1. 31P{1H} NMR (121 MHz, CD2Cl2): δ 29.1 (s) ppm. 13C{1H}
NMR (75 MHz, CD2Cl2): δ 219.9 (m, COeq), 213.3 (t, 2JPC = 9.0 Hz,
COax), 143.1 (m, ipso P(C6H5)2), 133.1 (s, ortho B(C6H5)2), 132.7
(app t, JCP = 5.9 Hz, ortho P(C6H5)2), 127.9 (s, meta B(C6H5)2), 127.5
(app t, JCP = 3.9 Hz, meta P(C6H5)2), 126.2 (s, para P(C6H5)2), 122.1
(s, para B(C6H5)2), 63.8 (m, (CH2CH2)2N), 22.5 (s, (CH2CH2)2N)
ppm.
[ASN][W(CO)4(Ph2BP2)] (3). Yield: 85%. Anal. Calcd for
C54H58O5BNP2W (as a 1:1 THF solvate): C, 61.32; H, 5.53; N,
1.32. Found: C, 61.63; H, 5.70; N, 1.31. Mp: 218−220 °C dec. IR
(THF): ν(CO) 2000 (m), 1890 (m, sh), 1877 (s), 1855 (m) cm−1. IR
(Nujol): ν(CO) 1999 (m), 1875 (s), 1844 (s, sh) cm−1. 31P{1H}
NMR (121 MHz, CD2Cl2): δ 12.1 (s, 31P−183W satellites: 13.0, 11.2, J
= 209 Hz) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 211.3 (m,
COeq), 206.3 (m, COax), 142.5 (m, ipso P(C6H5)2), 133.1 (s, ortho
B(C6H5)2), 132.8 (app t, JCP = 5.9 Hz, ortho P(C6H5)2), 128.2 (s, meta
B(C6H5)2), 127.5 (app t, JCP = 3.9 Hz, meta P(C6H5)2), 126.3 (s, para
P(C6H5)2), 122.2 (s, para B(C6H5)2), 63.8 (m, (CH2CH2)2N), 22.5 (s,
(CH2CH2)2N) ppm.
[ASN][fac-Cr(CO)3(CH3CN)(Ph2BP2)] (4). Yield: 64%. Anal. Calcd
for C51H53O3BCrN2P2: C, 70.67; H, 6.16; N, 3.23. Found: C, 71.16;
H, 6.38; N, 3.17. Mp: 188−190 °C dec. IR (CH3CN) ν(CO) 1904
(s), 1798 (m), 1779 (s, sh) cm−1. IR (Nujol): ν(CO) 1994 (w), 1899
(s), 1832 (w) cm−1. 31P{1H} NMR (121 MHz, CD3CN): δ 47.1 (s)
ppm. 13C{1H} NMR (75 MHz, CD3CN): δ 233.5 (app t, JCP = 5.8 Hz,
COeq), 231.9 (t, JCP = 13.6 Hz, COax), 144.2 (app t, JCP = 15.6 Hz, ipso
P(C6H5)2), 143.6 (app t, JCP = 8.8 Hz, ipso P(C6H5)2), 133.5−133.9
(m, ortho B(C6H5)2 and P(C6H5)2), 127.7−128.0 (m, meta B(C6H5)2
and P(C6H5)2), 127.0 (s, para P(C6H5)2), 126.4 (s, para P(C6H5)2),
122.8 (s, para B(C6H5)2), 122.3 (s, para B(C6H5)2), 63.8 (m,
(CH2CH2)2N), 23.3 (m, Ph2B(CH2PPh2)2), 22.7 (s, br,
(CH2CH2)2N) ppm. C-13 resonances for coordinated CH3CN were
not observed, mostly likely due to rapid CD3CN exchange.
[ASN][fac-Mo(CO)3(CH3CH2CN)(Ph2BP2)] (5). CH3CH2CN (80
mL) was added to Mo(CO)3(CH3CH2CN)3 (1.000 g, 2.900 mmol)
and [ASN][Ph2BP2] (2.000 g, 2.900 mmol). The solution was stirred
(2 h) and subsequently filtered through alumina. Removal of the
solvent in vacuo resulted in a yellow oil. The addition of Et2O (60 mL)
resulted in a sticky solid that was rendered a powder by trituration.
This solid was isolated by filtration, washed with Et2O (4 × 10 mL),
and dried in vacuo. Et2O diffusion into a CH3CN solution provided
yellow microcrystals (2.38 g, 89%). Anal. Calcd for
C52H55O3BMoN2P2: C, 67.54; H, 6.00; N, 3.03. Found: C, 68.02;
H, 6.34; N, 2.93. Mp: 71−74 °C dec. IR (CH3CH2CN): ν(CO) 1913
(s), 1808 (m), 1794 (m, sh) cm−1. IR (Nujol): ν(CO) 1904 (s), 1797
(s, sh), 1771 (s) cm−1. 31P{1H} NMR (121 MHz, CD2Cl2): δ 29.1 (s)
ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 217.5 (m, COeq), 217.3
(app t, J = 5.9 Hz, COax), 143.0 (m, ipso P(C6H5)2), 141.7 (m, ipso
P(C6H5)2), 133.1−133.5 (m, ortho B(C6H5)2) and P(C6H5)2), 127.7
(s, CH3CH2CN), 127.2−127.4 (m, meta B(C6H5)2 and P(C6H5)2),
126.5 (s, para P(C6H5)2), 125.9 (s, para P(C6H5)2), 122.4 (s, para
B(C6H5)2), 121.9 (s, para B(C6H5)2), 63.6 (m, (CH2CH2)2N), 22.5
(m, Ph2B(CH2PPh2)2), 22.4 (s, br, (CH2CH2)2N), 15.6 (s,
CH3CH2CN), 12.6 (s, CH3CH2CN) ppm.
Figure 6. Molecular structure of the anion of 17 (50% thermal
ellipsoids). Selected bond lengths (Å) and angles (deg): Mo−C(1) =
1.951(4), Mo−C(2) = 1.971(4), Mo−C(3) = 1.977(4), Mo−C(4) =
2.138(4), Mo−P(1) = 2.5487(11), Mo−P(2) = 2.5277(11), C(4)−
N(1) = 1.161(5); N(1)−C(4)−Mo = 174.4(3), C(4)−N(1)−C(5) =
178.1(4), C(1)−Mo−C(2) = 89.72(17), C(1)−Mo−C(3) =
88.36(17), C(2)−Mo−C(3) = 88.44(16), C(1)−Mo−C(4) =
91.98(16), C(2)−Mo−C(4) = 86.08(15), C(1)−Mo−P(2) =
89.27(13), C(3)−Mo−P(2) = 90.05(12), C(4)−Mo−P(2) =
95.44(11), C(2)−Mo−P(1) = 97.08(13), C(3)−Mo−P(1) =
97.70(12), C(4)−Mo−P(1) = 82.62(10), P(2)−Mo−P(1) =
84.08(3).
Mo(CO)3dppe fragment. However, the dramatic inertness of 8
and 9 toward diazomethane relative to M(CO)3(SO2)(L2) (L2
= dppm, dppe, dppp, chir) and apparently different fac/mer
isomerization barriers of 14 and 15 relative to those of
M(CO)3(CNC6H4(2-NO2))(dppe) highlight the surprises that
Ph2BP2 may offer in tuning the reactivity of low-valent group VI
metal complexes. Efforts to uncover more novel properties
engendered by Ph2BP2 are underway in this laboratory.
EXPERIMENTAL SECTION
■
Similar procedures were conducted to synthesize 1−3, 4−6, 7−9, and
10−15. Representative procedures for 1, 5, 8, and 10 are provided
below. General procedures and complete characterization details
(including 1H NMR spectral data) are given in the Supporting
Information.
[ASN][Cr(CO)4(Ph2BP2)] (1). THF (40 mL) was added to
[ASN][Ph2BP2] (0.500 g, 0.725 mmol) and Cr(CO)4(C8H12)
(0.197 g, 0.725 mmol). The orange solution was refluxed (16 h)
and subsequently filtered through Celite. Most of the solvent from the
resulting yellow solution was removed in vacuo. Addition of Et2O (40
mL) affected the precipitation of a yellow powder that was isolated by
filtration, washed with Et2O (3 × 10 mL), and dried in vacuo. Pentane
diffusion into a THF solution provided pale yellow microcrystals
(0.551 g, 89%). Anal. Calcd for C54H58O5BCrNP2 (as a 1:1 THF
solvate): C, 70.06; H, 6.31; N, 1.51. Found: C, 70.10; H, 6.41; N, 1.42.
Mp: 194−195 °C dec. IR (THF): ν(CO) 1990 (m), 1892 (s), 1875
(s), 1855 (s) cm−1. IR (Nujol): ν(CO) 1990 (s), 1921 (m), 1882 (s),
1874 (s, sh), 1844 (s), 1827 (s) cm−1. 31P{1H} NMR (121 MHz,
CD2Cl2): δ 47.7 (s) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 230.2
[ASN][fac-W(CO)3(CH3CH2CN)(Ph2BP2)] (6). Yield: 80%. Anal.
Calcd for C52H55O3BN2P2W: C, 61.68; H, 5.47; N, 2.77. Found: C,
61.98; H, 5.92; N, 2.86. Mp: 97−99 °C dec. IR (CH3CH2CN) ν(CO)
1906 (s), 1800 (s) cm−1. IR (Nujol): ν(CO) 1898 (s), 1789 (s, sh),
1766 (s) cm−1. 31P{1H} NMR (121 MHz, CD2Cl2): δ 18.7 (s,
31P−183W satellites: 19.9, 17.9, J = 219 Hz) ppm. 13C{1H} NMR (75
MHz, CD2Cl2): δ 225.6 (app t, JCP = 3.6 Hz, COax), 223.6 (m, COeq),
2
2
(app t, JCP = 9.7 Hz, COeq), 224.3 (t, JCP = 13.7 Hz, COax), 143.2
(app t, JCP = 15.6 Hz, ipso P(C6H5)2), 133.0 (s, ortho B(C6H5)2), 132.7
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143.6 (m, ipso P(C6H5)2), 142.5 (m, ipso P(C6H5)2), 133.2−133.4 (m,
ortho P(C6H5)2 and B(C6H5)2), 128.0 (s, meta B(C6H5)2), 127.9 (s,
meta B(C6H5)2), 127.6 (s, CH3CH2CN), 127.1−127.4 (m, meta
P(C6H5)2), 126.5 (s, para P(C6H5)2), 126.0 (s, para P(C6H5)2), 122.4
(s, para B(C6H5)2), 121.9 (s, para B(C6H5)2), 63.7 (s, br,
(CH2CH2)2N), 22.5 (m, Ph2B(CH2Ph2)2), 22.5 (s, (CH2CH2)2N),
15.7 (s, CH3CH2CN), 12.6 (s, CH3CH2CN) ppm.
C56H61BMoN2O3P2 (as a 1:1 THF solvate): C, 68.57; H, 6.62; N,
2.67. Found: C, 68.24; H, 6.98; N, 2.45. Mp: 178−179 °C. IR (THF):
ν(CO) 1916 (s), 1828 (s) cm−1, ν(CN) 2116 (w) cm−1. IR (Nujol):
ν(CO) 1914 (m), 1826 (m, sh), 1813 (m, sh), 1793 (m) cm−1; ν(CN)
2144 (w), 2125 (w, sh) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ
30.1 (s) ppm. 13C{1H} NMR (101 MHz, THF-d8): δ 222.1 (m,
COeq), 219.6 (app t, JCP = 8.7 Hz, COax), 166.0 (m, NC), 144.0 (m,
ipso P(C6H5)2), 133.0 (s, br, ortho B(C6H5)2), 132.5 (m, ortho
P(C6H5)2), 126.2 (m, meta P(C6H5)2 and meta B(C6H5)2), 125.2 (s,
para P(C6H5)2), 125.1 (s, para P(C6H5)2), 121.0 (s, para B(C6H5)2),
120.8 (s, para B(C6H5)2), 62.7 (m, (CH2CH2)2N), 53.2 (s, C6H11),
32.6 (s, C6H11), 25.1 (s, C6H11), 23.1 (s, C6H11), 21.8 (s,
(CH2CH2)2N) ppm.
[ASN][mer-Cr(CO)3(SO2)(Ph2BP2)] (7). Yield: 74%. Anal. Calcd
for C49H50BCrNO5P2S: C, 66.15; H, 5.66; N, 1.57. Found: C, 65.90;
H, 5.79; N, 2.68. IR (CH3CN): ν(CO) 2001 (w), 1901 (s) cm−1;
ν(SO) 1066 (m) cm−1. IR (Nujol): ν(CO) 2009 (m), 1924 (m, sh),
1910 (s, sh), 1890 (s), 1869 (m, sh) cm−1; ν(SO) 1059 (m) cm−1.
2
31P{1H} NMR (121 MHz, CD3CN): δ 48.7 (d, JPP = 44.1 Hz), 41.1
(d, 2JPP = 44.7 Hz) ppm. 13C{1H} NMR (75 MHz, CD3CN): δ 230.4
(m, COeq), 220.7 (app t, JCP = 13.7 Hz, COax), 140.8 (d, JCP = 33.2
Hz, ipso P(C6H5)2), 139.7 (d, JCP = 33.2 Hz, ipso P(C6H5)2), 132.3 (s,
ortho B(C6H5)2), 131.3−131.4 (m, ortho P(C6H5)2), 128.3 (m, meta
B(C6H5)2), 127.3−127.4 (m, meta P(C6H5)2), 125.7 (s, para
P(C6H5)2), 121.7 (s, para B(C6H5)2), 61.9 (s, (CH2CH2)2N), 21.7
(m, Ph2B(CH2Ph2)2), 21.6 (s, (CH2CH2)2N) ppm.
[ASN][fac-W(CO)3(CNC6H11)(Ph2BP2)] (11). Yield: 65%. Anal.
Calcd for C60H69BWN2O4P2 (as a 1:1 THF solvate): C, 63.28; H,
6.11; N, 2.46. Found: C, 63.09; H, 6.46; N, 2.32. Mp: 203−205 °C
dec. IR (THF): ν(CO) 1908 (s), 1822 (s) cm−1; ν(CN) 2112 (w)
cm−1. IR (Nujol): ν(CO) 1912 (s), 1823 (s, sh), 1796 (s) cm−1;
ν(CN) 2116 (m) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ 11.0 (s,
31P−183W satellites: 11.6, 10.4, J = 211 Hz) ppm. 13C{1H} NMR (101
MHz, THF-d8): δ 212.1 (m, COeq), 210.4 (app t, JCP = 6.8 Hz, COax),
157.4 (m, NC), 141.6 (m, ipso P(C6H5)2), 131.1 (s, ortho B(C6H5)2),
130.7 (m, ortho P(C6H5)2), 124.62 (s, meta B(C6H5)2), 124.55 (s, meta
B(C6H5)2), 124.3 (m, meta P(C6H5)2), 123.3 (s, para P(C6H5)2),
123.2 (s, para P(C6H5)2), 119.2 (s, para B(C6H5)2), 119.0 (s, para
B(C6H5)2), 60.9 (m, (CH2CH2)2N), 51.5 (s, C6H11), 30.8 (s, C6H11),
21.6 (s, C6H11), 21.3 (s, C6H11), 19.9 (s, (CH2CH2)2N) ppm.
[ASN][fac-Mo(CO)3(CNC6H3(2,6-CH3))(Ph2BP2)] (12). Yield:
85%. Anal. Calcd for C58H59BN2O3P2Mo: C, 69.61; H, 5.94; N,
2.80. Found: C, 70.13; H, 6.37; N, 2.60. Mp: 249−251 °C. IR (THF):
ν(CO) 1912 (s), 1837 (s) cm−1; ν(CN) 2056 (w) cm−1. IR (Nujol):
ν(CO) 1902 (s), 1836 (m, sh), 1813 (s) cm−1; ν(CN) 2063 (m), 2002
(w, sh) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ 28.1 (s) ppm.
13C{1H} NMR (101 MHz, THF-d8): δ 219.7 (m, COeq), 217.3 (app t,
JCP = 8.6 Hz, COax), 180.6 (app t, J = 10.3 Hz, CN), 163.8 (m, ipso
B(C6H5)2), 141.6 (m, ipso P(C6H5)2), 132.7 (s, para CNC6H3(2,6-
Me)), 131.0 (s, ortho B(C6H5)2), 130.9 (s, ortho B(C6H5)2), 130.6 (m,
ortho P(C6H5)2), 127.7 (s, ipso CNC6H3(2,6-Me)), 125.2 (s, meta
B(C6H5)2), 124.5 (s, meta CNC6H3(2,6-Me)), 124.4 (m, meta
P(C6H5)2), 124.1 (s, ortho CNC6H3(2,6-Me)), 123.4 (s, para
P(C6H5)2), 123.2 (s, para P(C6H5)2), 119.1 (s, para B(C6H5)2),
118.9 (s, para B(C6H5)2), 60.8 (m, (CH2CH2)2N), 19.9 (s,
(CH2CH2)2N), 16.7 (s, CNC6H3(2,6-Me)) ppm.
[ASN][fac-W(CO)3(CNC6H3(2,6-CH3))(Ph2BP2)] (13). Yield: 86%.
Anal. Calcd for C58H59BN2O3P2W: C, 63.99; H, 5.46; N, 2.57. Found:
C, 64.56; H, 5.65; N, 2.37. Mp: 230−233 °C dec. IR (THF): ν(CO)
1904 (s), 1832 (s) cm−1; ν(CN) 2050 (w) cm−1. IR (Nujol): ν(CO)
1893 (s), 1828 (m, sh), 1808 (s) cm−1; ν(CN) 2054 (m) cm−1.
31P{1H} NMR (162 MHz, THF-d8): δ 10.9 (s, 31P−183W satellites:
11.5, 10.2, J = 212 Hz) ppm. 13C{1H} NMR (101 MHz, THF-d8): δ
214.2 (m, COeq), 213.2 (app t, JCP = 6.7 Hz, COax), 176.8 (app t, J =
9.2 Hz, CN), 166.5 (m, ipso B(C6H5)2), 143.8 (m, ipso P(C6H5)2),
135.5 (s, para CNC6H3(2,6-Me)), 133.8 (s, ortho B(C6H5)2), 133.7 (s,
ortho B(C6H5)2), 133.4 (m, ortho P(C6H5)2), 130.9 (s, ipso
CNC6H3(2,6-Me)), 128.0 (s, meta CNC6H3(2,6-Me)), 127.54 (s,
meta B(C6H5)2), 127.50 (s, ortho CNC6H3(2,6-Me)), 127.2 (m, meta
P(C6H5)2), 126.2 (s, para P(C6H5)2), 126.1 (s, para P(C6H5)2), 122.0
(s, para B(C6H5)2), 121.7 (s, para B(C6H5)2), 63.6 (m,
(CH2CH2)2N), 22.7 (s, (CH2CH2)2N), 19.6 (s, CNC6H3(2,6-Me))
ppm.
[ASN][mer-Mo(CO)3(SO2)(Ph2BP2)] (8). CH2Cl2 (20 mL) was
added to 5 (0.462 g, 0.500 mmol), and the yellow solution was cooled
to 0 °C. The solution became red-orange upon its saturation in SO2
and was stirred at ambient temperature (8 h). Removal of volatiles in
vacuo (trap-to-trap transfer) resulted in an orange solid to which
CH2Cl2 (60 mL) was added. An orange solution was obtained by
filtration through Celite that was subsequently concentrated in vacuo.
Addition of Et2O (60 mL) resulted in a pale orange powder that was
isolated via filtration, washed with Et2O (3 × 15 mL), and dried in
vacuo. Et2O diffusion into a CH3CN solution provided pale yellow
microcrystals (0.292 g, 63%). Anal. Calcd for C49H50O5BMoNP2S: C,
63.03; H, 5.40; N, 1.50. Found: C, 62.70; H, 5.54; N, 1.43. Mp: 164−
165 °C dec. IR (CH2Cl2): ν(CO) 2015 (w), 1982 (w), 1908 (s) cm−1;
ν(SO) 1060 (m) cm−1. IR (Nujol): ν(CO) 2022 (m), 1984 (w), 1936
(m, sh), 1920 (s), 1897 (s, sh), 1871 (m, sh) cm−1; ν(SO) 1202 (w),
1063 (m) cm−1. 31P{1H} NMR (121 MHz, CD2Cl2): δ 32.9 (d, 2JPP
=
2
33.0 Hz), 26.0 (d, JPP = 33.0 Hz) ppm. 13C{1H} NMR (75 MHz,
2
2
CD2Cl2): δ 218.0 (dd, JCP(trans) = 23.1 Hz, JCP(cis) = 13.6 Hz, COeq),
209.6 (app t, JCP = 8.8 Hz, COax), 140.6 (d, JCP = 33.2 Hz, ipso
P(C6H5)2), 139.8 (d, JCP = 35.2 Hz, ipso P(C6H5)2), 132.2 (s, ortho
B(C6H5)2), 131.3−131.5 (m, ortho P(C6H5)2), 128.4 (s, meta
B(C6H5)2), 128.2 (s, meta B(C6H5)2), 127.4−127.5 (m, meta
P(C6H5)2), 125.6 (s, para P(C6H5)2), 121.7 (s, para B(C6H5)2),
61.8 (s, (CH2CH2)2N), 21.2 (s, (CH2CH2)2N) ppm.
[ASN][mer-W(CO)3(SO2)(Ph2BP2)] (9). Yield: 69%. Anal. Calcd for
C49H50O5BNP2SW: C, 57.61; H, 4.93; N, 1.37. Found: C, 57.61; H,
5.08; N, 1.34. Mp: 168−169 °C dec. IR (CH2Cl2): ν(CO) 2010 (w),
1978 (w), 1896 (s) cm−1; ν(SO) 1059 (m) cm−1. IR (Nujol): ν(CO)
2016 (m), 1981 (w), 1957 (w), 1929 (m, sh), 1911 (s, sh), 1888 (s),
1866 (m, sh) cm−1; ν(SO) 1199 (w), 1061 (m) cm−1. 31P{1H} NMR
2
(121 MHz, CD2Cl2): δ 14.0 (d, JPP = 25.2 Hz, 31P−183W satellites:
15.0, 14.8, 13.1, 12.9, J = 233 Hz, 2JPP = 24.3 Hz), 10.9 (d, 2JPP = 24.6
2
Hz, 31P−183W satellites: 11.9, 11.7, 10.0, 9.8, J = 227 Hz, JPP = 24.8
Hz) ppm. 13C{1H} NMR (75 MHz, CD2Cl2): δ 209.2 (m, COeq),
203.1 (m, COax), 140.2 (d, JCP = 38.1 Hz, ipso P(C6H5)2), 139.4 (d,
JCP = 40.0 Hz, ipso P(C6H5)2), 132.2 (s, ortho B(C6H5)2), 131.4−131.6
(m, ortho P(C6H5)2), 128.6 (s, meta B(C6H5)2), 128.5 (s, meta
B(C6H5)2), 127.5 (s, meta P(C6H5)2), 127.3 (s, meta P(C6H5)2), 125.6
(s, para P(C6H5)2), 121.7 (s, para B(C6H5)2), 61.8 (s, (CH2CH2)2N),
21.6 (s, (CH2CH2)2N) ppm.
[ASN][fac-Mo(CO)3(CNC6H11)(Ph2BP2)] (10). THF (30 mL) was
added to 5 (0.300 g, 0.324 mmol). An aliquot (1 mL) of a cyclohexyl
isocyanide stock solution (1.053 g of C6H11NC in 27.0 mL of CH2Cl2;
1 mL contains 0.357 mmol of C6H11NC) was added dropwise. The
solution turned from bright yellow to colorless upon stirring (1 h).
The solution was filtered through Celite and concentrated to ∼6 mL
in vacuo. Addition of Et2O (35 mL) resulted in the precipitation of a
white powder that was isolated by filtration, washed with Et2O (3 × 10
mL), and dried in vacuo. Et2O diffusion into a THF solution provided
pale yellow needles (0.236 g, 74%). Anal. Calcd for
[ASN][Mo(CO)3(CNC6H4(2-NO2))(Ph2BP2)] (14). Yield: 87%.
Anal. Calcd for C60H62BMoN3O6P2 (as a 1:1 THF solvate): C,
66.12; H, 5.73; N, 3.86. Found: C, 66.47; H, 5.74; N, 3.80. Mp: 153−
155 °C dec. IR (THF): ν(CO) 2004 (w) 1907 (s), 1870 (m, sh), 1851
(m, sh) cm−1; ν(CN) 2046 (w), 2021 (w, sh) cm−1. IR (Nujol):
ν(CO) 1897 (s), 1857 (m), 1830 (s) cm−1; ν(CN) 2049 (m), 2028
(w, sh) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ 29.9 (s, fac), 29.0
(s, mer) ppm. The fac:mer ratio on the basis of these peak areas was
∼85:15. The mer isomer concentration was sufficiently low that only
C-13 resonances assigned to the fac isomer are reported. 13C{1H}
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NMR (101 MHz, THF-d8): δ 220.7 (m, COeq), 217.4 (m, COax),
143.2 (m, ipso P(C6H5)2), 142.0 (s, C-2, CNC6H4(2-NO2)), 133.6 (s,
C-5, CNC6H4(2-NO2)), 133.0 (s, ortho B(C6H5)2), 132.9 (s, ortho
B(C6H5)2), 132.5 (app t, J = 5.8 Hz, ortho P(C6H5)2), 132.3 (app t, J =
5.8 Hz, ortho P(C6H5)2), 130.8 (s, C-6, CNC6H4(2-NO2)), 126.7 (s,
C-4, CNC6H4(2-NO2)), 126.49 (s, meta P(C6H5)2), 126.45 (s, meta
B(C6H5)2), 126.39 (s, meta P(C6H5)2), 126.3 (s, meta B(C6H5)2),
125.3 (s, para B(C6H5)2), 125.2 (s, br, para P(C6H5)2), 125.1 (s, br,
para P(C6H5)2), 124.7 (s, para B(C6H5)2), 120.89 (s, C-3, CNC6H4(2-
NO2)), 120.85 (s, C-1, CNC6H4(2-NO2)), 62.7 (m, (CH2CH2)2N),
22.2 (s, Ph2B(CH2PPh2)2), 21.8 (s, (CH2CH2)2N) ppm.
[ASN][W(CO)3(CNC6H4(2-NO2))(Ph2BP2)] (15). Yield: 88%. Anal.
Calcd for C60H62BMoN3O6P2 (as a 1:1 THF solvate): C, 61.17; H,
5.31; N, 3.57. Found: C, 61.24; H, 5.58; N, 3.55. Mp: 149−151 °C
dec. IR (THF): ν(CO) 2000 (w), 1899 (s), 1876 (s, sh), 1854 (s, sh)
cm−1; ν(CN) 2047 (w, sh), 2022 (w, sh) cm−1. IR (Nujol): ν(CO)
1897 (s), 1857 (m), 1830 (s) cm−1; ν(CN) 2049 (m), 2028 (w, sh)
cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ 12.6 (s, 31P−183W
satellites: 13.2, 11.9, J = 215 Hz, fac), 11.9 (s, 31P−183W satellites: 12.5,
11.2, J = 219 Hz, mer) ppm. The fac:mer ratio on the basis of these
peak areas was ∼70:30. The mer isomer concentration was sufficiently
low that only C-13 resonances assigned to the fac isomer are reported,
with the exception of the 13CO resonances. 13C{1H} NMR (101 MHz,
THF-d8): δ 212.4 (m, fac, COeq), 210.6 (m, fac, COax), 209.9 (m, mer,
COeq), 205.6 (m, mer, COax), 190.4 (m, CN), 142.5 (m, ipso
P(C6H5)2), 141.9 (s, C-2, CNC6H4(2-NO2)), 133.6 (s, C-5,
CNC6H4(2-NO2)), 132.8 (m, ortho B(C6H5)2), 132.4 (m, ortho
P(C6H5)2), 130.7 (s, C-6, CNC6H4(2-NO2)), 127.0 (s, C-4,
CNC6H4(2-NO2)), 126.8 (s, meta B(C6H5)2), 126.7 (s, meta
B(C6H5)2), 126.5 (app t, J = 4.6 Hz, meta P(C6H5)2), 125.2 (s, br,
para P(C6H5)2), 124.9 (s, para B(C6H5)2), 124.8 (s, para B(C6H5)2),
121.02 (s, C-3, CNC6H4(2-NO2)), 120.99 (s, C-1, CNC6H4(2-NO2)),
62.7 (m, (CH2CH2)2N), 21.8 (s, (CH2CH2)2N) ppm.
[ASN][fac-Mo(CO)3(CNCH2CH2NH2)(Ph2BP2)] (17). An aliquot
(2.0 mL) of a 2-azidoethyl isocyanide stock solution in CH2Cl2 (stock
solution composition: 0.4825 g of CNCH2CH2N3 in 14.0 mL of
CH2Cl2; 2 mL delivers 0.714 mmol of isocyanide) was added to a
solution of 5 (0.600 g, 0.648 mmol) in THF (40 mL). The mixture
was stirred for 1 h. An infrared spectrum of the solution indicated
complete consumption of 5 and formation of [ASN][Mo-
(CO)3(CNCH2CH2N3)(Ph2BP2)] (IR (THF): ν(CO) 1920 (s),
1832 (m); ν(CN) 2120 (w), ν(N3) 2098 (w) cm−1). The solution
was filtered through Celite, and the filtrate was concentrated to ∼5
mL. The addition of Et2O (40 mL) resulted in an oily brown
precipitate. The Et2O-rich mother liquor was removed via cannula, and
more Et2O (40 mL) was added. The mixture was stirred (1 h) before
the solvent was removed via cannula. Upon drying in vacuo (15 min)
the residue changed to a tan powder that was subsequently dissolved
in THF (40 mL). An aliquot (2.0 mL) of a stock solution of PMe3 in
THF (stock solution composition 1.0 mL of PMe3 in 24.0 mL of THF;
2 mL delivers 0.778 mmol of PMe3) was added, and the solution was
stirred (5 h). An IR spectrum (IR (THF): ν(CO) 1917 (s), 1827 (m);
ν(CN) 2128 (w) cm−1) indicated complete consumption of the azido
complex to afford a presumed iminophosphorane intermediate.
Degassed H2O (0.15 mL) was added, and the solution was stirred
for 10 h. The solution (IR (THF): ν(CO) 1919 (s), 1827 (m); ν(CN)
2119 cm−1) was filtered through Celite and concentrated to ∼5 mL in
vacuo. The addition of Et2O (35 mL) resulted in a brown oil. The
mother liquor was removed via cannula, and Et2O was added (40 mL).
The oil changed to a tan powder with stirring (2 h). This solid was
isolated by filtration, washed with Et2O (3 × 10 mL) and dried in
vacuo. Et2O diffusion into a THF solution provided tan microcrystals
(0.434 g, 71%). Anal. Calcd for C56H64BMoN3O4P2 (as a 1:1 THF
solvate): C, 66.47; H, 6.38; N, 4.15. Found: C, 66.53; H, 6.48; N, 3.90.
Mp: 185−187 °C. IR (THF): ν(CO) 1918 (s), 1829 (s) cm−1; ν(CN)
2119 (w) cm−1. IR (Nujol): ν(CO) 1914 (s), 1835 (m, sh), 1791 (s)
cm−1; ν(CN) 2116 (m) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ
[ASN][fac-Mo(CO)3(CNC6H4(2-NH2))(Ph2BP2)] (16). A slurry of
aqueous Raney nickel (∼0.5 mL, estimated on the tip of a spatula) was
added to a solution of 14 (0.600 g, 0.588 mmol) in THF (40 mL).
The suspension was cooled to 0 °C prior to addition of hydrazine
hydrate (0.600 mL of 50−60% hydrazine hydrate solution). The
solution was removed from the ice bath and stirred (105 min). The
color changed from dark purple to yellow within 30 min. The
suspension was filtered through Celite, and the yellow filtrate was
concentrated to ∼4 mL in vacuo. The addition of Et2O (35 mL)
resulted in the precipitation of a yellow solid that was isolated by
filtration, washed with Et2O (3 × 15 mL), and dried in vacuo. Et2O
diffusion into a THF solution provided yellow needles (0.438 g, 74%)
Anal. Calcd for C60H64BMoN3O4P2 (as a 1:1 THF solvate): C, 67.99;
H, 6.09; N, 3.96. Found: C, 68.06; H, 6.16; N, 3.71. Mp: 213−214 °C
dec. IR (THF): ν(CO) 1914 (s), 1835 (m) cm−1; ν(CN) 2068 (w)
cm−1. IR (Nujol): ν(CO) 1911 (m), 1840 (m, sh), 1818 (m) cm−1;
ν(CN) 2069 (w) cm−1. 31P{1H} NMR (162 MHz, THF-d8): δ 27.9
1
30.4 (s) ppm. H NMR (400 MHz, THF-d8): δ 7.38−7.41 (m, 8H,
ortho P(C6H5)2), 7.01 (m, 2H, ortho B(C6H5)2), 6.80−6.94 (m, 14H,
ortho B(C6H5)2, meta P(C6H5)2, meta B(C6H5)2), 6.66 (app t, J = 5.8
Hz, 2H, para P(C6H5)2), 6.57 (app t, J = 7.1 Hz, 1H, para B(C6H5)2),
6.48 (app t, J = 6.8 Hz, 2H, P(C6H5)2), 6.41 (app t, J = 7.0 Hz, 1H,
B(C6H5)2), 3.12 (m, 10H, (CH2CH2)2N and CNCH2), 2.54 (t, J = 6.0
Hz, 2H, CH2NH2), 1.96 (s, br, 4H, Ph2B(CH2PPh2)2), 1.91 (m, 8H,
(CH2CH2)2N), 0.99 (s, br, 2H, NH2) ppm. Varying quantities of THF
(with one molecule per formula unit the maximum) were observed in
samples of 17. 13C{1H} NMR (101 MHz, THF-d8): δ 222.1 (m,
COeq). 219.4 (app t, J = 8.8 Hz, COax), 168.0 (m, CN), 143.9 (m, ipso
P(C6H5)2), 133.03 (s, ortho B(C6H5)2), 132.94 (s, ortho B(C6H5)2),
132.5 (app t, ortho P(C6H5)2), 126.2−126.3 (m, meta P(C6H5)2 and
meta B(C6H5)2), 125.3 (s, para P(C6H5)2), 125.0 (s, para P(C6H5)2),
121.0 (s, para B(C6H5)2), 120.8 (s, para B(C6H5)2), 62.7 (m,
(CH2CH2)2N), 47.3 (s, CH2NC), 41.7 (s, CH2NH2), 21.8 (s,
(CH2CH2)2N) ppm.
1
(s) ppm. H NMR (400 MHz, THF-d8): δ 7.36−7.42 (m, 8H, ortho
P(C6H5)2), 6.97 (m, 2H, ortho B(C6H5)2), 6.83−6.94 (m, 14H, ortho
B(C6H5)2, meta P(C6H5)2, meta B(C6H5)2), 6.72 (dd, J = 7.9 Hz, J =
1.4 Hz, 1H, H-4, CNC6H4(2-NH2)), 6.62 (dd, 8.2 Hz, J = 1.1 Hz, 1H,
H-3, CNC6H4(2-NH2)), 6.42−6.60 (m, 8H, para P(C6H5)2, para
B(C6H5)2, H-5/6 CNC6H4(2-NH2)), 4.31 (s, 2H, NH2), 3.15 (m, 8H,
(CH2CH2)2N), 1.93 (m, br, 12H, Ph2B(CH2PPh2)2 and
(CH2CH2)2N) ppm. Varying quantities of THF (with one molecule
per formula unit the maximum) were observed in samples of 16.
13C{1H} NMR (101 MHz, THF-d8): δ 219.7 (m, COeq), 216.9 (app t,
J = 8.8 Hz, COax), 179.4 (app t, J = 11.0 Hz, CN), 142.2 (s, C-2,
CNC6H4(2-NH2)), 141.8 (m, ipso P(C6H5)2), 131.2 (s, ortho
B(C6H5)2), 131.1 (s, ortho B(C6H5)2), 130.5 (m, ortho P(C6H5)2),
125.7 (s, C-4, CNC6H4(2-NH2)), 124.4−124.6 (m, meta P(C6H5)2
and meta B(C6H5)2), 123.8 (s, C-4, CNC6H4(2-NH2)), 123.4 (s, para
P(C6H5)2), 123.2 (s, para P(C6H5)2), 119.1 (s, para B(C6H5)2), 119.0
(s, para B(C6H5)2), 114.2 (s, C-3, CNC6H4(2-NH2)), 113.7 (s, C-1,
CNC6H4(2-NH2)), 112.5 (s, C-5, CNC6H4(2-NH2)), 60.8 (m,
(CH2CH2)2N), 19.9 (s, (CH2CH2)2N) ppm.
X-ray Crystallography. X-ray-quality crystals were obtained by
diffusion of pentane into THF solutions (1−3), Et2O into THF
solutions (10, 11, 16, 17), Et2O into CH3CN solutions (4−6, 8, 9,
15), and Et2O into a CH2Cl2 solution (14). Crystals were selected
from the mother liquor in a N2-filled glovebag. Details regarding the
data collection, structure solution, and refinement for each of these
single-crystal X-ray studies are provided in the Supporting
Information.
ASSOCIATED CONTENT
■
S
* Supporting Information
Text, figures, tables, and CIF files giving complete experimental
details and characterization data, thermal ellipsoid drawings,
details of crystallographic data collection, solution, and
refinement, and crystallographic data. This material is available
free of charge via the Internet at http://pubs.acs.org.
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(19) Ueng, C.-H.; Shih, G.-Y. Acta Crystallogr., Sect. C 1992, C48,
988.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for P.J.F.: fischer@macalester.edu.
(20) Aluri, B. R.; Peulecke, N.; Pietz, S.; Spannenberg, A.; Muller, B.
̈
H.; Schulz, S.; Drexler, H.-J.; Heller, D.; Al-Hazmi, M. H.; Mosa, F. M.;
Wohl, A.; Muller, W.; Rosenthal, U. Dalton Trans. 2010, 39, 7911.
(21) Mrutu, A.; William, W. N.; Kemp, R. A. Inorg. Chem. Commun.
2012, 18, 110.
(22) While the crystal data and structure refinement details of 8 (R1
= 0.0663, wR2 = 0.1365 (all data)) are sound, the SO2 ligand of 8
exhibits anomalously high displacements that could not be improved
via disorder modeling. Consequently, only the metrical parameters of
isostructural 9 are discussed herein.
̈
̈
Present Addresses
†Department of Chemistry, Columbia University, MC3134,
3000 Broadway, New York, NY 10027, USA.
‡Department of Chemistry, Emory University, 1515 Dickey
Drive, Atlanta, GA 30322, USA
Notes
The authors declare no competing financial interest.
(23) Rousche, J.-C.; Dobson, G. R. Inorg. Chim. Acta 1978, 28, L139.
(24) This apparent fac/mer isomerization that appears rapid in
solution on the NMR time scale at ambient temperature has prompted
VT NMR studies of 14, 15, and related M(CO)3(CNC6H4(2-NO2))
(L2) complexes containing bidentate phosphine ligands with varying
electronic profiles.
(25) (a) Schenk, W. A.; Urban, P. J. Organomet. Chem. 1991, 411,
C27. (b) Schenk, W. A.; Urban, P.; Dombrowski, E. Chem. Ber. 1993,
126, 679.
(26) The abbreviation chir or (S,S)-chiraphos is for (2S,3S)-
(−)-bis(diphenylphosphino)butane, a dppe analogue with methyl
substituents on each carbon of the ligand backbone.
(27) Schenk, W. A.; Baumann, F.-E. Chem. Ber. 1982, 115, 2615.
(28) Schenk, W. A.; Karl, U.; Horn, M. R. Z. Naturforsch., B 1989, 44,
1513.
ACKNOWLEDGMENTS
■
The National Science Foundation supported this research
under Macalester College grants CHE-1011800 and DBI-
1039655. The latter award purchased a 400 MHz NMR
spectrometer. P.J.F. thanks Victor G. Young, Jr. (University of
Minnesota X-ray Crystallographic Laboratory), for his expertise
and persistence. A new diffractometer with a Cu X-ray source in
Dr. Young’s laboratory was purchased through a NSF grant
(MRI-1224900) and funding from the University of Minnesota.
P.J.F. is indebted to Rebecca C. Hoye and Robert C. Rossi for
helpful discussions and to Macalester College endowed funds
for two summer undergraduate research stipends (K.P.S.
(2011), L.A. (2013)).
(29) (a) Liu, C.-Y.; Chen, D.-Y.; Lee, G.-H.; Peng, S.-M.; Liu, S.-T.
Organometallics 1996, 15, 1055. (b) Kaufhold, O.; Stasch, A.; Edwards,
P. G.; Hahn, F. E. Chem. Commun. 2007, 1822. (c) Kaufhold, O.;
Flores-Figueroa, A.; Pape, T.; Hahn, F. E. Organometallics 2009, 28,
896. (d) Kaufhold, O.; Stasch, A.; Pape, T.; Hepp, A.; Edwards, P. G.;
Newman, P. D.; Hahn, F. E. J. Am. Chem. Soc. 2009, 131, 306.
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̈
(31) Both 2-aminoethyl isocyanide and 2-aminophenyl isocyanide are
similarly stabilized by the analogous W(CO)3(Ph2BP2) fragment on
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(Ph2BP2)] and [ASN][W(CO)3(CNC6H4(2-NH2))(Ph2BP2)] have
been elusive to date. Only the molybdenum complexes are discussed
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̈
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dx.doi.org/10.1021/om5001056 | Organometallics 2014, 33, 1300−1309