Gold(I) heteroatom-substituted imido complexes. Amino nitrene loss from [(Lau)3(μ-NNR2)]+

Article abstract of DOI:10.1021/ic990586u

The heteroatom-substituted imido complexes [(LAu)₃(μ-NX)]⁺ (X = NR₂, R = Ph, Me, Bz; X = OH, Cl; L = a phosphine) have been prepared from the reactions of NH₂X with [(LAu)₃(μ-O)]⁺. Thermally unstable [(LAu)₃-(μ-NNMe₂)]⁺ (L = P(p-XC₆H₄)₃, X = H, F, Me, Cl, MeO) decompose to the gold cluster [LAu]₆²⁺ and tetramethyltetrazene Me₂NN=NNMe₂. The decomposition is first-order overall with a rate constant that increases with increasing pK(a) of the phosphine ligand. Activation parameters for the decomposition are ΔH((+)) = 99(4) kJ/mol and ΔS((+)) = 18.5(5) J/K·mol for L = PPh₃ and ΔH((+)) = 78(3) kJ/mol and ΔS((+)) = -47(2) J/K·mol for L = P(p-MeOC₆H₄)₃. The decomposition of analogous [(LAu)₃(μ-NNBz₂)]⁺ produces bibenzyl, indicative of the release of free amino nitrene Bz₂NN.

Full text of DOI:10.1021/ic990586u

602
Inorg. Chem. 2000, 39, 602-608
Gold(I) Heteroatom-Substituted Imido Complexes. Amino Nitrene Loss from
[(LAu)3(µ-NNR2)]+
Bruce W. Flint, Yi Yang, and Paul R. Sharp*
Department of Chemistry, University of MissourisColumbia, Columbia, Missouri 65211
ReceiVed May 20, 1999
The heteroatom-substituted imido complexes [(LAu)3(µ-NX)]+ (X ) NR2, R ) Ph, Me, Bz; X ) OH, Cl; L )
a phosphine) have been prepared from the reactions of NH2X with [(LAu)3(µ-O)]+. Thermally unstable [(LAu)3-
(µ-NNMe2)]+ (L ) P(p-XC6H4)3, X ) H, F, Me, Cl, MeO) decompose to the gold cluster [LAu]6 and
2+
tetramethyltetrazene Me2NNdNNMe2. The decomposition is first-order overall with a rate constant that increases
with increasing pKa of the phosphine ligand. Activation parameters for the decomposition are ∆Hq ) 99(4) kJ/
mol and ∆Sq ) 18.5(5) J/K‚mol for L ) PPh3 and ∆Hq ) 78(3) kJ/mol and ∆Sq ) -47(2) J/K‚mol for L )
P(p-MeOC6H4)3. The decomposition of analogous [(LAu)3(µ-NNBz2)]+ produces bibenzyl, indicative of the release
of free amino nitrene Bz2NN.
Introduction
produced from the substituted hydrazine R2NNH2.9,21 Unlike
the dinitrogen/hydrazido complex, [(LAu)3(µ-NNR2)]+ (R )
alkyl) readily decompose in solution. Although Au is generally
not catalytically active (see refs 22-27 for a growing number
of exceptions), the stability of metal-nitrogen bonds is relevant
to such diverse processes as ammonia oxidation,28-30 NOx and
nitrite reduction,31-33 and nitrogen fixation.34 We have therefore
undertaken a study of the decomposition of [(LAu)3(µ-NNR2)]+
and have examined the influence of the phosphine ligand’s pKa
on the rate and activation parameters for the reaction. We have
also prepared the related isoelectronic complexes [(LAu)3(µ-
NCl)]+ and [(LAu)3(µ-NOH)]+ and briefly examined their
stability.
Gold is exceptional in its ability to form compounds with
unusual structures and properties. This chemistry features
hypercoordinate complexes,1 aurophilic attractions,1-7 numerous
clusters,8-19 and recently a dinitrogen/hydrazido complex.20 This
dinitrogen/hydrazido complex [(LAu)6(µ-N2)]2+, formed from
hydrazine, a common reducing agent, is remarkably stable
despite the notorious susceptibility of Au ions to reduction. The
gold(I) hydrazido complexes [(LAu)3(µ-NNR2)]+ are similarly
(1) Schmidbaur, H. Chem. Soc. ReV. 1995, 24, 391-400.
(2) Zank, J.; Schier, A.; Schmidbaur, H. J. Chem. Soc., Dalton Trans.
1998, 323-324.
(3) Canales, F.; Gimeno, M. C.; Laguna, A.; Jones, P. G. J. Am. Chem.
Soc. 1996, 118, 4839-4845.
Results
(4) Harwell, D. E.; Mortimer, M. D.; Knobler, C. B.; Anet, F. A. L.;
Hawthorne, M. F. J. Am. Chem. Soc. 1996, 118, 2679-2685.
(5) Pyykko¨, P.; Runeberg, N.; Mendizabal, F. Chem. Eur. J. 1997, 3,
1451-1457.
The white to yellow hydrazido complexes [(LAu)3(µ-NNR2)]+
(R ) Ph, L ) PPh3;21 R ) CH2Ph (Bz), L ) PPh3, P(p-
MeOC6H4)3; R ) Me, L ) PPh3,21 PEtPh2, PPriPh2, P(o-tol)3,
P(p-FC6H4)3, P(p-ClC6H4)3, P(p-tol)3, P(p-MeOC6H4)3) are
(6) Veiros, L. F.; Calhorda, M. J. J. Organomet. Chem. 1996, 510, 71-
81.
(7) Grandberg, K. I.; Dyadchenko, V. P. J. Organomet. Chem. 1994, 474,
1-21.
(21) Ramamoorthy, V.; Wu, Z.; Yang, Y.; Sharp, P. R. J. Am. Chem. Soc.
1992, 114, 1526-1527.
(8) Yang, Y.; Sharp, P. R. J. Am. Chem. Soc. 1994, 116, 6983-6984.
(9) Yang, Y.; Wu, Z.; Ramamoorthy, V.; Sharp, P. R. The Chemistry of
the Copper and Zinc Triads; Welch, A. J., Chapman, S. K., Eds.; The
Royal Society of Chemistry: Cambridge, 1993.
(10) Mingos, D. M. P.; Watson, M. J. AdV. Inorg. Chem. 1996, 39, 327-
399.
(22) Haruta, M.; Tsubota, S.; Kobayashi, T.; Kageyama, H.; Genet, M. J.;
Delmon, B. J. Catal. 1993, 144, 175-192.
(23) Hoflund, G. B.; Gardner, S. D.; Schryer, D. R.; Upchurch, B. T.; Kielin,
E. J. Appl. Catal., B 1995, 6, 117-126.
(24) Sakurai, H.; Haruta, M. Appl. Catal. A 1995, 127, 93-105.
(25) Sakurai, H.; Ueda, A.; Kobayashi, T.; Haruta, M. J. Chem. Soc., Chem.
Commun. 1997, 271-272.
(11) Hall, K. P.; Mingos, D. M. P. Prog. Inorg. Chem. 1984, 32, 237-
325.
(12) Laguna, A.; Laguna, M.; Gimeno, M. C.; Jones, P. G. Organometallics
1992, 11, 2759-2760.
(26) Valden, M.; Lai, X.; Goodman, D. W. Science 1998, 281, 1647-
1650.
(13) Copley, R. C. B.; Mingos, D. M. P. J. Chem. Soc., Dalton Trans.
1996, 479-489.
(27) Ueda, A.; Oshima, T.; Haruta, M. Appl. Catal., B 1997, 12, 81-93.
(28) Ishitani, O.; White, P. S.; Meyer, T. J. Inorg. Chem. 1996, 35, 2167-
2168.
(14) Copley, R. C. B.; Mingos, D. M. P. J. Chem. Soc., Dalton Trans.
1996, 491-500.
(29) Carley, A. F.; Davies, P. R.; Roberts, M. W. Chem. Commun. 1998,
1793-1794.
(15) Shan, H.; Sharp, P. R. Angew. Chem., Int. Ed. Engl. 1996, 35, 635-
636.
(30) Trombetta, M.; Ramis, G.; Busca, G.; Montanari, B.; Vaccari, A.
Langmuir 1997, 13, 4628-4637.
(16) Crespo, O.; Gimeno, M. C.; Jones, P. G.; Laguna, A.; Villacampa,
M. D. Angew. Chem., Int. Ed. Engl. 1997, 36, 993-995.
(17) Schmid, G. Chem. ReV. 1992, 92, 1709.
(18) Teo, B. K.; Dang, H.; Campana, C. F.; Zhang, H. Polyhedron 1998,
17, 617-621.
(19) Teo, B. K.; Zhang, H.; Shi, X. Inorg. Chem. 1994, 33, 4086-4097.
(20) Shan, H.; Yang, Y.; James, A. J.; Sharp, P. R. Science 1997, 275,
1460-1462.
(31) Murphy, W. R. Jr.; Takeuchi, K.; Barley, M. H.; Meyer, T. J. Inorg.
Chem. 1986, 25, 1041-1053.
(32) Burch, R.; Fornasiero, P.; Southward, B. W. L. Chem. Commun. 1998,
739-740.
(33) Connerton, J.; Joyner, R. W.; Stockenhuber, M. Chem. Commun. 1997,
185-186.
(34) Hidai, M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115.
10.1021/ic990586u CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/21/2000

Gold(I) Heteroatom-Substituted Imido Complexes
Inorganic Chemistry, Vol. 39, No. 3, 2000 603
Table 1. Crystallographic and Data Collection Parameters for
[{(o-tol)3PAu}3(µ-NOH)]BF4‚3THF and
[(Ph3PAu)3(µ-NNMe2Et)](OTf)2‚3THF
empirical formula C75H88Au3BF4NO4P3 C72H80Au3F6N2O9P3S2
fw
1838.17
P21/n (no. 14)
298
15.813(8)
26.145(4)
17.768(8)
1979.31
P1h (no. 2)
173
space group
T (°C)
a (Å)
b (Å)
c (Å)
12.9750(8)
14.5771(9)
22.0437(14)
71.750(1)
89.420(1)
68.236(1)
3650.7(4)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
96.98(2)
7291(5)
4
1.67
d
calcd (g/cm3)
1.80
λ (Å)
0.7093 (Mo)
6.14
0.0499, 0.1320
0.7093 (Mo)
6.21
0.0513, 0.1079
µ (mm-1
)
R1,a wR2b
Figure 1. ORTEP drawing of the cationic portion of [{(o-tol)3PAu}3-
(µ-NOH)]BF4 with a hydrogen-bonded THF molecule.
2
a R1 ) (∑||Fo| - |Fc||)/∑|Fo|. b wR2 ) [(∑w(Fo - Fc2)2)/
∑w(Fc2)2]1/2 with w ) 1/[σ2(Fo ) + (xP)2]; P ) (Fo + 2Fc2)/3, x )
0.1025 (NOH complex) and 0.0649 (NNMe2Et complex).
2
2
obtained from [(LAu)3(µ-O)]+ and the 1,1-substituted hydrazines
R2NNH2 according to eq 1. Several of these complexes are very
unstable in solution and must be isolated quickly to avoid
decomposition (see below). Once isolated in the solid state, the
complexes are stable.
molecule hydrogen-bonded to the hydrogen atom of the NOH
group. An abbreviated summary of crystal data collection and
processing is given in Table 1. Selected bond distances and
angles are listed in Table 2. The structure of the complex closely
resembles those of the many other [(LAu)3(µ-E)]+ deriva-
tives7,21,35-43 including related [(LAu)3(µ-NOSiMe3)]+.44
The decomposition of the hydrazido complex [(LAu)3(µ-
NNMe2)]+ (L ) PPh3) has been reported to follow eq 3.21
An attempt was also made to prepare [(Ph3PAu)3(µ-NNPri2)]+
according to eq 1 (R ) Pri). A reaction between the oxo complex
and Pri2NNH2 does occur, but the hydrazido complex is not
detected. Instead, the gold cluster11 [(Ph3PAu)6]2+ and Pri2NNd
NNPri2 form as the oxo complex [(Ph3PAu)3(µ-O)]+ is con-
sumed. These are the same types of products produced in the
decomposition of [(Ph3PAu)3(µ-NNMe2)]+ (see below), sug-
gesting that [(Ph3PAu)3(µ-NNPri2)]+ is formed but decomposes
as quickly as it is produced.
Two other gold heteroatom-substituted imido complexes are
prepared in reactions similar to that shown in eq 1. Colorless
[(LAu)3(µ-NOH)]+ is formed by treating [(LAu)3(µ-O)]+ with
hydroxylamine NH2OH (eq 2, X ) OH, L ) PPh3, P(o-tol)3),
Consistent with previous work showing that the nuclearity of
phosphine gold clusters is dependent on the cone angle of the
phosphine ligand,11 this same equation also describes the
decomposition of the dimethylhydrazido [(LAu)3(µ-NNMe2)]+
complexes with L ) a para-substituted arylphosphine ligand
(cone angle 145°, same as for PPh3) or PPh2Pri (cone angle
150°). The product edge-shared bitetrahedral gold clusters
[(LAu)6]2+ are readily identified by their known fluxional
behavior and characteristic UV-vis spectra.11 The fluxional
process involves exchange of the edge-shared positions with
the wing-tip positions and is observed in both proton and 31P
NMR spectra. Ambient-temperature 31P NMR spectra of the
para-substituted aryl phosphine ligand clusters show similar
shifts and fast exchange (single sharp peak) while the PPh2Pri
cluster shows intermediate exchange (very broad peak). Low-
temperature spectra show the expected pair of peaks in a 2:1
and [(LAu)3(µ-NCl)]+ is the product from the reaction of
[(LAu)3(µ-O)]+ with chloramine NH2Cl (eq 2, X ) Cl, L )
PPh3). The triphenylphosphine derivative [(Ph3PAu)3(µ-NOH)]+
is too unstable to isolate in pure form and decomposes cleanly
to the cluster [(Ph3PAu)6]2+. In contrast, the (o-tol)3P derivative
[{(o-tol)3PAu}3(µ-NOH)]+ is stable in solution. [(Ph3PAu)3(µ-
NCl)]+ decomposes over several hours at ambient temperatures
to mixtures of Ph3PAuCl and the nitrido complex [(Ph3-
PAu)5N]+.1 The nitrido complex is also a major decomposition
product of the silyl imido complexes [(LAu)3(µ-NSiR3)]+.35
An X-ray crystal structure determination of [((o-tol)3PAu)3-
(µ-NOH)](BF4) confirms the expected structure. A drawing of
the cationic portion is given in Figure 1 and includes a THF
(36) Nesmeyanov, A. N.; Perevalova, E. G.; Struchkov, Y. T.; Antipin,
M. Y.; Grandberg, K. I.; Dyadchenko, V. P. J. Organomet. Chem.
1980, 201, 343-349.
(37) Ramamoorthy, V.; Sharp, P. R. Inorg. Chem. 1990, 29, 3336-3338.
(38) Yang, Y.; Sharp, P. R. Inorg. Chem. 1993, 32, 1946-1951.
(39) Angermaier, K.; Schmidbaur, H. J. Chem. Soc., Dalton Trans. 1995,
559-564.
(40) Kolb, A.; Bissinger, P.; Schmidbaur, H. Z. Anorg. Allg. Chem. 1993,
619, 1580-1588.
(41) Canales, F.; Gimeno, M. C.; Jones, P. G.; Laguna, A. Angew. Chem.,
Int. Ed. Engl. 1994, 33, 769-770.
(42) Vincente, J.; Chicote, M.-T.; Guerrero, R.; Jones, P. G.; de Arellano,
M. C. R. Inorg. Chem. 1997, 36, 4438-4443.
(43) Kuz’mina, L. G. Zh. Neorg. Khim. 1993, 38, 994-1003.
(44) Tripathi, U. M.; Scherer, W.; Schier, A.; Schmidbaur, H. Inorg. Chem.
1998, 37, 174-175.
(35) Angermaier, K.; Schmidbaur, H. Chem. Ber. 1995, 128, 817-822.

604 Inorganic Chemistry, Vol. 39, No. 3, 2000
Flint et al.
Table 2. Selected Distances (Å) and Angles (deg) for [(LAu)3(µ-NOH)]BF4 (L ) P(o-tol)3)
Au1-Au3
Au1-P1
Au1-N1
O1-N1
3.1412 (7)
2.249 (4)
2.041 (10)
1.421 (13)
Au1-Au2
Au2-P2
Au2-N1
3.1946 (7)
2.251 (3)
2.033 (10)
Au2-Au3
Au3-P3
Au3-N1
3.1767 (7)
2.248 (4)
2.000 (10)
Au3-N1-Au2
Au2-N1-Au1
N1-Au2-P2
N1-Au3-Au1
O1-N1-Au2
103.9 (5)
Au3-N1-Au1
N1-Au1-P1
N1-Au3-P3
O1-N1-Au3
O1-N1-Au1
102.0 (4)
103.3 (5)
177.7 (3)
39.5 (3)
177.2 (3)
177.4 (3)
116.5 (8)
112.8 (8)
116.4 (7)
Table 3. Phosphine pKa Values and Rate Constant Data for
Decomposition of [(LAu)3(µ-NNMe2)]BF4 at 298 K
k (s-1
)
k (s-1
)
L
pKaa
× 103
L
pKaa
× 103
(p-ClC6H4)3P 1.03 0.63(2) (p-tol)3P
3.84 0.22(1)
(p-FC6H4)3P
Ph3P
1.97 0.43(2) (p-MeOC6H4)3P 4.59 0.28(1)
2.73 0.30(1)
a pKa data taken from ref 45.
ratio. Evidently, exchange is more rapid for the clusters with
the smaller cone angle para-substituted arylphosphine ligands
than for the cluster with the slightly larger cone angle phosphine
PPh2Pri.
Figure 2. log of the rate constants (298 K) for the decomposition of
[(LAu)3(µ-NNMe2)]BF4 versus the pKa of L. The line represents the
least-squares fit excluding L ) (p-MeOC6H4)3P.
The known11 larger cluster [(LAu)10Au]3+ and [L2Au]+ are
the gold-containing products with the smaller cone angle
phosphine ligands L ) PMe2Ph (cone angle 122°) and PPh2-
Me (cone angle 136°, eq 4). Again, this is consistent with
previous work showing that the main determinant of the
nuclearity of phosphine gold clusters is the cone angle of the
phosphine ligand.11
indicates a stronger donor ligand, which retards the decomposi-
tion and gives a more stable hydrazido complex.
The temperature dependence of the rate constant was evalu-
ated for L ) PPh3 and P(p-MeOC6H4)3. Data and a plot of ln
k versus 1/T are given in the Supporting Information. Extracted
activation parameters are ∆Hq ) 99(4) kJ/mol and ∆Sq ) 18.5-
(5) J/K‚mol for L ) PPh3 and ∆Hq ) 78(3) kJ/mol and ∆Sq )
-47(2) J/K‚mol for L ) P(p-MeOC6H4)3.
The first-order decomposition of the hydrazido complexes
and the formation of tetramethyltetrazene suggest the formation
and dimerization of the nitrene Me2NN. FAB mass spectral data
for [(LAu)3(µ-NNMe2)]+ (L ) PPh3) are also suggestive of
nitrene loss and show the [(LAu)3]+ cluster as the major mass
peak above 1000. Experiments designed to trap free nitrene in
the decomposition were unsuccessful probably due to the low
reactivity of amino nitrenes.51 As an alternative approach, the
hydrazido complexes [(LAu)3(µ-NNBz2)]+ (L ) PPh3, P(p-
MeOC6H4)3) were prepared as described above, and their
decompositions were examined. These compounds are more
stable than the dimethyl analogues and decompose over several
days to bibenzyl and [(LAu)6]2+ (eq 5). Tetrabenzyltetrazene
is not detected. The formation of bibenzyl is indicative of free
Bz2NN, where the stability of the benzyl radical permits
decomposition of the nitrene to bibenzyl and dinitrogen before
dimerization.51
In an earlier communication the kinetics for the reaction in
eq 3 for L ) PPh3 were reported to be second order.21
Subsequent reaction studies cast doubt on this result, and a re-
evaluation of the previous experiments revealed a systematic
error in the measurements that incorrectly led to this assignment.
Kinetic measurements have been repeated here for the PPh3
complex and completed for several para-substituted arylphos-
phine ligand complexes. The decomposition of eq 3 is first order
in all cases studied.
First-order plots are given as Supporting Information. Rate
constants and pKa values for the phosphine ligands (taken from
ref 45) are listed in Table 3, and a plot of log k versus the pKa
of the phosphine ligand is shown in Figure 2. A similar plot
(Supporting Information) but with an opposite slope is obtained
when log k is plotted against the phosphine ligand electronic
parameter ø.46,47 An inverse relationship between the pKa and
ø values of the phosphine ligand is expected with this set of
isosteric, σ-donor ligands.48-50 With the exception of L ) P(p-
MeOC6H4)3, a linear relationship (r2 ) 0.988) is observed with
larger pKa values, giving smaller k values. A larger pKa value
The likely involvement of the hydrazido nitrogen lone pair
in the decomposition of [(LAu)3(µ-NNR2)]+ prompted us to
investigate the reaction of [(LAu)3(µ-NNR2)]+ with alkylating
(48) Liu, H.-Y.; Eriks, K.; Prock, A.; Giering, W. P. Organometallics 1990,
9, 1758-1766.
(45) Rahman, Md. M.; Liu, H. Y.; Prock, A.; Giering, W. P. Organome-
tallics 1987, 6, 650-658.
(46) Tolman, C. A. Chem. ReV. 1977, 77, 313-348.
(47) Bartik, T.; Himmler, T.; Schulte, H.; Seevogel, K. J. J. Organomet.
Chem. 1984, 272, 29.
(49) Rahman, Md. M.; Liu, H. Y.; Prock, A.; Giering, W. P. Organome-
tallics 1989, 8, 1-7.
(50) Hudson, R. H. E.; Poe¨, A. J. Organometallics 1995, 14, 3238-3248.
(51) Loffe, B. V. Russ. Chem. ReV. 1972, 41, 131.

Gold(I) Heteroatom-Substituted Imido Complexes
Inorganic Chemistry, Vol. 39, No. 3, 2000 605
complex to Au(0). The general trend of greater stability of
[(LAu)3(µ-NNR2)]+ with more strongly donating L is consistent
with this process, where greater donation from L stabilizes the
Au(I) centers to reduction. The deviation of the L ) P(p-
MeOC6H4)3 derivative is unusual. Linear relationships between
the log of reaction rate constants and phosphine ligand pKa
values (or the phosphine ligand electronic parameter, ø) have
been found for other systems, and para-substituted triarylphos-
phines have generally fallen on the linear line.54 The deviation
of the L ) P(p-MeOC6H4)3 derivative is discussed below in
conjunction with the activation parameters.
The qualitatively decreasing stability of the complexes [(Ph3-
PAu)3(µ-NNR2)]+, R ) Ph > Bz > Me > Pri, is also consistent
with reduction of the gold(I) centers in the rate-determining step
and follows the expected increasing reducing strength of the
hydrazido unit. Steric factors in this sequence are unlikely to
be significant as the R groups are fairly far removed from the
Au centers. This is supported by an examination of the structure
of [(Ph3PAu)3(µ-NNMe2Et)]2+, which does not show any close
intracation contacts involving the NNMe2Et group.
Although the comparison is less direct, [(Ph3PAu)3(µ-NOH)]+
is much less stable than its closest analogue [(Ph3PAu)3(µ-
NNMe2)]+ and decomposes to give reduced Au centers. This
suggests that the HON group is more strongly reducing than
the R2NN group, which is inconsistent with the expected greater
donor strength of R2N over HO. However, we do not know the
decomposition mechanism of the hydroxylamine complex,
where factors such as hydrogen bonding (see Figure 1) may be
involved. The Me3SiON complex is apparently stable,44 but the
Me3Si group is electron withdrawing, and the Me3SiON group
is expected to be less reducing than the HON group. Investiga-
tion of the O-methylhydroxylamine complex would be informa-
tive.
Further support for amino nitrene loss is the positive ∆Sq for
the decomposition of [(Ph3PAu)3(µ-NNMe2)]+. Positive values
for ∆Sq are indicative of “loose” or simple fission transition
states55 such as that expected in the rupture of the Au-N bonds.
The relatively large negative value of ∆Sq for the L ) P(p-
MeOC6H4)3 derivative is in sharp contrast and suggests a more
ordered transition state. The ∆Hq values also differ significantly.
Consistent with the unexpectedly facile decomposition of the
L ) P(p-MeOC6H4)3 derivative, the transition state for the L
) P(p-MeOC6H4)3 derivative is 20 kJ/mol more accessible than
that for the L ) PPh3 derivative. These differences do not affect
the products of the decomposition, and evidence for free nitrene
(formation of bibenzyl) is found for both phosphine ligand
derivatives.
The results for the P(p-MeOC6H4)3 derivative suggest that
the complex is able to achieve a configuration or conformation
where the Au(I) centers are more easily reduced than expected
from the pKa value of P(p-MeOC6H4)3. This in turn suggests
that the phosphine ligand can transiently become a weaker
donor. The p-MeO group is unique in the series studied here in
that the effect of this para-substituent primarily involves
resonance donation into the phenyl ring (Scheme 2). (In fact,
the weaker inductive effect of the MeO substituent is opposite
and withdraws electron density from the ring.) Maximum
resonance donation requires that the MeO group lie in the plane
of the phenyl ring. Rotation of the MeO group out of optimum
donation reduces the phosphine donor strength. This process,
Figure 3. ORTEP drawing of the cationic portion of [(Ph3PAu)3(µ-
NNMe2Et)](OTf)2.
reagents. Addition of methyl or ethyl triflate to a decomposing
solution of [(Ph3PAu)3(µ-NNMe2)]+ results in a stable solution
of [(Ph3PAu)3(µ-NNRMe2)]2+ (R ) Me, Et, eq 6). The alkylated
complexes are much more stable than the parent hydrazido
complexes and solutions remain unchanged for days. Related
[(LAu)3(µ-NPR3)]2+ are also known to be very stable.52,53
An X-ray crystal structure determination of [(Ph3PAu)3(µ-
NNEtMe2)](OTf)2 confirms the expected structure. A drawing
of the cationic portion is given in Figure 3. An abbreviated
summary of crystal data collection and processing is given in
Table 1. Selected bond distances and angles are listed in Table
4. As with the hydroxylamine complex, the structure closely
resembles those of the many other [(LAu)3(µ-E)]+ deriva-
tives.7,21,35-44
Discussion
A proposed mechanism for the decomposition of [(LAu)3-
(µ-NNR2)]+, consistent with the evidence of free nitrene, mass
spectral data, and the first-order reaction rate, is given in Scheme
1. The rate-determining step involves the release of the stabilized
amino nitrene NNR2 (see resonance forms) from the three gold
centers of [(LAu)3(µ-NNR2)]+. The amino nitrene NNR2 may
than follow two paths (A and B). A review of the chemistry of
N-nitrenes by Loffe51 discusses various studies of substituted
hydrazine oxidation and the fate of the resulting amino nitrenes.
Amino nitrenes containing R groups with relatively stable
radicals (such as benzyl, allyl, and nitrile groups) favor
decomposition to R2 and N2, while those containing R groups
with less stable radicals (such as Me and Pri) survive long
enough to dimerize to the tetrazene (Scheme 1, path A). The
observation of tetrazine for R ) Me and Pri and bibenzyl for R
) Bz in the decomposition of [(LAu)3(µ-NNR2)]+ is indicative
of the formation of free amino nitrenes.
The rate-determining step in Scheme 1 involves the formal
reduction of two of the three Au(I) centers of the hydrazido
(52) Bauer, A.; Gabbai, F.; Schier, A.; Schmidbaur, H. Philos. Trans. R.
Soc. London, Ser. A 1996, 354, 381-394.
(53) Bauer, A.; Mitzel, N. W.; Schier, A.; Rankin, D. W. H.; Schmidbaur,
H. Chem. Ber. 1997, 130, 323.
(54) Golovin, M. N.; Rahman, M. M.; Belmonte, J. E.; Giering, W. P.
Organometallics 1985, 4, 1981-1991.
(55) Gilbert, R. Theory of Unimolecular Recombination Reactions; Black-
well Scientific: Oxford, England, 1990.

606 Inorganic Chemistry, Vol. 39, No. 3, 2000
Flint et al.
Table 4. Selected Distances (Å) and Angles (deg) for [(Ph3PAu)3(µ-NNMe2Et)](OTf)2
Au1-Au3
2.9813 (5)
2.246 (2)
2.082 (6)
1.456 (9)
95.8 (3)
Au1-Au2
Au2-P2
Au2-N1
3.0669 (5)
2.239 (2)
2.052 (7)
Au2-Au3
Au3-P3
Au3-N1
3.1626 (5)
2.241 (2)
2.084 (6)
Au1-P1
Au1-N1
N1-N2
Au2-N1-Au1
Au1-N1-Au3
N1-Au2-P2
N2-N1-Au1
N2- N1-Au3
Au2-N1-Au3
N1-Au1-P1
N1-Au3-P3
N2-N1-Au2
99.8 (3)
91.4 (2)
171.93 (18)
170.69 (19)
122.3 (5)
169.76 (18)
121.1 (5)
119.8(5)
Scheme 1
important in the stability of these complexes. This is shown
most clearly by the qualitatively greater stability of the L )
(o-tol)3P over the L ) (p-tol)3P derivatives despite a lower pKa
value for (o-tol)3P (3.08 versus 3.84). We have previously noted
a phosphine ligand steric effect in the structures of the oxo
complexes [(LAu)3(µ-O)]+, where the Au3O tetrahedron expands
at the Au3 base with an increase in the phosphine ligand’s cone
angle.38 This results in longer Au-Au distances, which could
be an important parameter here as the release of the nitrene is
expected to be accompanied by the formation of cluster Au-
Au bonds. This implies that the “aurophilic” interaction1-7 is a
vital component in the decomposition reaction.
Scheme 2
Finally, we come to the question of why the hydrazido
complexes [(LAu)3(µ-NNR2)]+ are less stable than the dinitrogen
complex [(LAu)3(µ-N2)(AuL)3]2+. Given the decomposition
mechanism of Scheme 1, it is apparent that the stabilization of
the nitrene by the lone pair on the amino group is critical. Such
a lone pair is absent in the dinitrogen complexes. Elimination
of the nitrogen lone pair of [(LAu)3(µ-NNMe2)]+ by alkylation
does effectively halt decomposition in the product [(LAu)3(µ-
NNRMe2)]2+ (R ) Me, Et).
occurring on one or more of the rings of the phosphine ligands,
would lead to an easier than expected reduction of the Au(I)
centers and, as a more organized configuration, a negative ∆Sq.
As a transient kinetic effect this would not contribute signifi-
cantly to pKa and other thermodynamic measurements.56-60 It
may not have been observed in other kinetic studies50,61-74 either
because the reactions are relatively insensitive to electronic
contribution or because reaction acceleration occurs with
increasing phosphine ligand donor strength (e.g., oxidative
addition and nucleophilic attack by phosphines), opposite that
with the hydrazido complexes here.
Conclusions
We have reported the synthesis and characterization of a series
of heteroatom-substituted gold imido complexes including the
novel complex [(LAu)3(µ-NCl)]+. We have demonstrated that,
with the exception of L ) P(p-MeOC6H4)3, the stability of the
[(LAu)3(µ-NNR2)]+ has a linear free energy relationship with
the donor strength (pKa) of the phosphine ligand L. The
decomposition of [(LAu)3(µ-NNR2)]+ involves the release of a
free nitrene NNR2 with, for L ) PPh3, a “loose” transition state.
A more ordered transition state and a faster than expected
decomposition rate for L ) P(p-MeOC6H4)3 are attributed to
resonance donation loss in the phosphine ligand by rotation of
the MeO group out of the phenyl ring plane. Decomposition is
blocked by alkylation of the hydrazido ligand, thereby eliminat-
ing the stabilizing nitrogen lone pair. Larger phosphine ligands
retard the decomposition, suggesting that Au-Au interactions
are also important in the transition state.
Somewhat surprisingly, considering the low coordination
number of gold(I), phosphine ligand steric factors appear to be
(56) Li, C.; Nolan, S. P. Organometallics 1995, 14, 1327-1332.
(57) Serron, S. A.; Luo, L. B.; Li, C. B.; Cucullu, M. E.; Stevens, E. D.;
Nolan, S. P. Organometallics 1995, 14, 5290-5297.
(58) Serron, S. A.; Nolan, S. P. Organometallics 1995, 14, 4611-4616.
(59) Serron, S.; Nolan, S. P.; Moloy, K. G. Organometallics 1996, 15,
4301-4306.
(60) Haar, C. M.; Nolan, S. P.; Marshall, W. J.; Moloy, K. G.; Prock, A.;
Giering, W. P. Organometallics 1999, 18, 474-479.
(61) Chalk, K. L.; Pomeroy, R. K. Inorg. Chem. 1984, 23, 444-449.
(62) Chen, L.; Poe¨, A. J. Inorg. Chem. 1989, 28, 3641-3647.
(63) Wilson, M. R.; Woska, D. C.; Prock, A.; Giering, W. P. Organome-
tallics 1993, 12, 1742-1752.
(64) Wilson, M. R.; Liu, H.; Prock, A.; Giering, W. P. Organometallics
1993, 12, 2044.
(65) Bartholomew, J.; Fernandez, A. L.; Lorsbach, B. A.; Wilson, M. R.;
Prock, A.; Giering, W. P. Organometallics 1996, 15, 295-301.
(66) Fernandez, A.; Reyes, C.; Wilson, M. R.; Woska, D. C.; Prock, A.;
Giering, W. P. Organometallics 1997, 16, 342-348.
(67) Fernandez, A.; Reyes, C.; Prock, A.; Giering, W. P. Organometallics
1998, 17, 2503-2509.
Experimental Section
General Procedures. Unless otherwise stated, the reactions were
performed under a nitrogen atmosphere using a VAC drybox or Schlenk
techniques. Dry THF, toluene, diethyl ether, CH2Cl2, and hexane were
obtained by passing the solvent down an activated alumina column.
Non-chlorine-containing solvents were stored over Na shavings. Me2-
NNH2 and Ph2NNH2‚HCl were purchased from Aldrich Chemical Co.
and used as received. [(LAu)3(µ-O)]X (X ) BF4, OTf),36,38,40 1,1-
dibenzylhydrazine,75 1,1-diisopropylhydrazine,76 hydroxylamine,77 and
chloroamine78 were prepared according to literature procedures. Infrared
(68) Neubrand, A.; Poe¨, A. J.; Vaneldik, R. Organometallics 1995, 14,
3249-3258.
(69) Chen, L. Z.; Poe¨, A. J. Coord. Chem. ReV. 1995, 143, 265-295.
(70) Farrar, D. H.; Hao, J. B.; Poe¨, A. J.; Stromnova, T. A. Organometallics
1997, 16, 2827-2832.
(71) Romeo, R.; Plutino, M. R.; Scolaro, L. M.; Stoccoro, S. Inorg. Chim.
Acta 1997, 265, 225-233.
(72) Romeo, R.; Alibrandi, G. Inorg. Chem. 1997, 36, 4822-4830.
(73) Bessel, C. A.; Margarucci, J. A.; Acquaye, J. H.; Rubino, R. S.;
Crandall, J.; Jircitano, A. J.; Takeuchi, K. J. Inorg. Chem. 1993, 32,
5779.
(74) Moreno, C.; Delgado, S.; Macazaga, J. M. Organometallics 1991, 10,
1124.
(75) Dewar, M. J. S. J. Am. Chem. Soc. 1973, 95, 1562.
(76) Lemal, D. M.; Menger, F.; Coats, E. J. Am. Chem. Soc. 1964, 86,
2395.
(77) Hurd, C. D. Inorg. Synth. 1973, 1, 87-89.
(78) Coleman G. H.; Johnson, H. L. Inorg. Synth. 1973, 1, 59-62.

Gold(I) Heteroatom-Substituted Imido Complexes
Inorganic Chemistry, Vol. 39, No. 3, 2000 607
spectra were obtained with a Nicolet Magna-550 spectrometer. UV-
vis absorption spectra were recorded on a Hewlett-Packard 8452A
diode-array spectrophotometer. NMR spectra were recorded on a Bruker
ARX-250 NMR or a Bruker AMX-500 instrument at ambient temper-
ature unless otherwise indicated. 1H and 31P chemical shifts are reported
in parts per million and are referenced to TMS (internal) and 85% H3-
PO4 (external) standards, respectively. FAB mass spectra were collected
on a VG ZAB-SE spectrometer with a glycerin/3-nitrobenzyl alcohol
matrix. Desert Analysis, Oneida Research Services, Inc., National
Chemical Consulting, Inc., or Chemisar Laboratories Inc. performed
the elemental analyses.
Preparation of Ph2NNH2. NaOH (150 mg, 3.75 mmol) was
dissolved in 100 mL of water. This solution was added dropwise with
stirring to 500 mg (2.27 mmol) of Ph2NNH2‚HCl. The mixture was
stirred for 1.5 h, transferred to a separatory funnel, and extracted three
times with CH2Cl2 (3 × 2 mL). The CH2Cl2 solution was dried with
CaSO4. The dry solution was separated from the CaSO4, and all volatiles
were removed in vacuo. Crystallization of the resulting oily residue
was achieved by dissolving the oil in a minimum amount of hexane
and cooling overnight at -30 °C. The product was isolated by decanting
the mother liquor and drying the pale yellow crystals in vacuo. Yield:
200 mg (48%). Mp 33-35 °C.
(250 MHz, CDCl3): δ 7.01-7.33 (m, 36H, Ph), 2.84 (s, 6H, N-CH3),
2.34 (s, 27H, ring-CH3).
L ) PPh3. This complex was prepared by a procedure analogous to
that used for L ) P(o-tol)3 and was isolated in an 92% yield as a pale
brown solid. Anal. calcd (found) for C56H51Au3BF4N2P3: C, 44.17
(44.30); H, 3.38 (3.37); N, 1.84 (1.80). 31P NMR (250 MHz, CDCl3):
1
δ 29.2 (s). H NMR (250 MHz, CDCl3): δ 7.25-7.48 (m, 45H, Ph),
2.82 (s, 6H, N-CH3). FAB MS: m/z 1435 ([(LAu)3(µ-NNMe2)]+), 1377
([(LAu)3]+), 721 ([L2Au]+), 459 ([LAu]+).
L ) PEtPh2. This complex was prepared by a procedure analogous
to that used for L ) P(o-tol)3 and was isolated in an 85% yield as a
pale brown solid. 31P NMR (101 MHz, CD2Cl2): δ 29.8 (s). 1H NMR
(250 MHz, CD2Cl2): δ 7.97-7.02 (m, 30H, Ph), 2.84 (s, 6H, NMe2),
2.45 (dq, JH-H ) 7.6 Hz, JH-P ) 10.4 Hz, 6H, CH2CH3), 1.17 (dt,
JH-P ) 21.3 Hz, 9H, CH2CH3).
L ) PPriPh2. This complex was prepared by a procedure analogous
to that used for L ) P(o-tol)3 and was isolated in an 80% yield as a
pale brown-yellow solid. 31P NMR (101 MHz, CD2Cl2): δ 43.3 (s).
1H NMR (250 MHz, CD2Cl2): δ 7.85-7.11 (m, 30H, Ph), 2.93 (s,
6H, NMe2), 2.91 (dsept, JH-H ) 6.8 Hz, JH-P ) 12.6 Hz, 3H,
CH(CH3)2), 1.18 (dd, JH-P ) 19.5 Hz, 18H, CH(CH3)2).
[(LAu)3(µ-NOH)]BF4. L ) P(o-tol)3. NH2OH (5 mg, 0.2 mmol)
was added to a CH2Cl2 (1 mL) solution of [(LAu)3(µ-O)]BF4 (50 mg,
0.031 mmol). After 10 min, the product was precipitated with diethyl
ether as a white solid. Yield: 93%. White crystals suitable for X-ray
analysis were obtained from concentrated THF solutions at room
[(Ph3PAu)3(µ-NNPh2)]BF4. Ph2NNH2 (9.2 mg, 0.05 mmol) was
added to a stirred solution of [(Ph3PAu)3(µ-O)]BF4 (74 mg, 0.05 mmol)
in CH2Cl2 (0.5 mL). The solution immediately turned bright yellow.
After about 10 min, excess ether was added. The resulting yellow solid
was isolated by filtration, washed with ether, and dried in vacuo.
1
temperature. 31P NMR (101 MHz, CD2Cl2): δ 6.5 (s). H NMR (250
1
Yield: 70 mg (85%). 31P NMR (101 MHz, CD2Cl2): δ 28.7 (s). H
MHz, CD2Cl2): δ 6.84-7.53 (m, 36H, Ph), 4.76 (q, JP-H ) 2.13 Hz,
1H, OH), 2.39 (s, 27H, CH3). IR (mineral oil, cm-1): 3437 m (νOH).
L ) PPh3. This complex was prepared by a procedure analogous to
that used for L ) P(o-tol)3. However, the complex is very unstable in
solution (complete decomposition to [(LAu)6]2+ after 20 min at ambient
temperatures) and could not be isolated in pure form. 31P NMR (101
NMR (250 MHz, CD2Cl2): δ 6.85-7.45 (m, Ph). The crystal structure
of this complex has been reported.21
[(LAu)3(µ-NNBz2)]BF4. L ) PPh3. Dibenzylhydrazine (0.17 g, 2.9
mmol) was dissolved in 1 mL of CH2Cl2. An aliquot of this solution
(0.23 mL, 0.068 mmol) was added dropwise with stirring to [(Ph3-
PAu)3(µ-O)]BF4 (0.10 g, 0.068 mmol) dissolved in 5 mL of CH2Cl2 at
0 °C. After 0.5 h at 0 °C, the product was precipitated with diethyl
ether as a light brown solid. Yield: 94 mg (92%). 31P NMR (250 MHz,
1
MHz, CD2Cl2): δ 29 (s). The H NMR spectrum shows a quartet for
the NOH group similar to that for the L ) P(o-tol)3 derivative.
[(AuPPh3)3NCl](BF4). [(Ph3PAu)3(µ-O)]BF4 (100 mg, 0.062 mmol)
was dissolved in 10 mL of CH2Cl2. The solution was cooled to 0 °C,
and freshly prepared chloroamine (ca. 1 M in diethyl ether) was added
until 31P NMR spectra of the reaction mixture showed complete
consumption of the oxo complex (24 ppm). The product was precipi-
tated with diethyl ether as a white solid. Yield: 56 mg (56%). 31P NMR
(250 MHz, CH2Cl2): δ 29.1. Anal. calcd (found) for C54H45Au3BClF4-
NP3: C, 42.8 (43.1); H, 2.97 (3.01); N, 0.92 (0.74).
[(LAu)6](BF4)2. L ) P(p-ClC6H4)3. [(LAu)3(µ-NNMe2)]BF4 (55 mg,
0.03 mmol) was dissolved in THF with stirring. A deep red solution
was generated in 1 h. Excess ether was added. The red-brown solid
product was isolated by filtration, washed with ether, and dried in vacuo.
Yield: 48.4 mg (91%). 31P NMR (101 MHz, CD2Cl2): δ 57.6 (s). UV-
vis (THF): λmax (nm) 408, 295, 252. Anal. calcd (found) for C108H72-
Au6B2F8Cl18N2: C, 36.55 (36.12); H, 2.04 (2.03).
L ) PPriPh2. [(LAu)3(µ-NNMe2)]BF4 (56.8 mg, 0.04 mmol) was
dissolved in THF with stirring. A cloudy solution formed after 0.5 h.
The reaction mixture was stirred for 2 days. The resulting precipitate
was recovered by filtration, washed with THF, and dried in vacuo.
Yield: 39.2 mg (72%). The NMR spectra are exchange-broadened at
ambient temperatures (see the text). 31P NMR (101 MHz, CD2Cl2): δ
71.1 (br s, ν1/2 ) 2500 Hz). 31P NMR (-50 °C, 202 MHz, CD2Cl2):
δ 78.1 (s, 2P), 67.6 (s, 4P). 1H NMR (500 MHz, CD2Cl2): δ 3.6 (br s,
ν1/2 ) 37.5 Hz), 2.91 (br s, ν1/2 ) 31.3 Hz), 1.2 (br s, ν1/2 ) 37.5 Hz),
1.03 (br s, ν1/2 ) 37.5 Hz). UV-vis (CH2Cl2): νmax (nm) 474, 446,
310, 280, 268, 234. A similar procedure gives the known PPh3 (96%)
and P(p-tol)3 derivatives.11
[(Au11(PPh2Me)10](BF4)3. Me2NNH2 (3 mg, 0.05 mmol) was added
to a white suspension of [(Ph2MePAu)3(µ-O)]BF4 (66.8 mg, 0.05 mmol)
in THF (2 mL) with stirring. A homogeneous red solution rapidly
formed. After the solution was stirred for 2 h, a red precipitate along
with a deep red solution had formed. All volatiles were removed in
vacuo, and the red residue was dissolved in 2 mL of CH2Cl2. The CH2-
Cl2 solution was filtered through Celite, and excess ether was added.
The resulting red solid was isolated by filtration, washed with ether,
and dried in vacuo. Yield: 48.7 mg (88.0%). A similar procedure gives
1
CD2Cl2): δ 29.4 (s). H NMR (250 MHz, CD2Cl2): δ 6.8-7.4 (m,
55H, Ph), 4.18 (s, 4H, CH2Ph).
L ) P(p-MeOC6H4)3. This complex was prepared by a procedure
analogous to that used for L ) Ph3P and was isolated in an 86% yield
1
as a pale brown solid. 31P NMR (101 MHz, CD2Cl2): δ 25.4 (s). H
NMR (250 MHz, CD2Cl2): 6.6-7.4 (m, 46H, Ph), 4.16 (s, 4H, CH2-
Ph), 3.73 (s, 27H, OCH3). FAB MS: m/z 1857 ([(LAu)3(µ-NNBz2)]+),
1647 ([(LAu)3]+), 901 ([L2Au]+), 549 ([LAu]+).
[(LAu)3(µ-NNMe2)]BF4. L ) P(o-tol)3. Me2NNH2 (5.3 µL, 0.068
mmol) was added to a stirred CH2Cl2 (2 mL) solution of [(LAu)3(µ-
O)]BF4 (109 mg, 0.068 mmol). The solution rapidly turned from
colorless to pale yellow. After 5 min, the off-white product was
precipitated with diethyl ether, recovered by filtration, washed with
ether, and dried in vacuo. Yield: 102 mg (91%). 31P NMR (101 MHz,
1
CD2Cl2): δ 9.6 (s). H NMR (250 MHz, CD2Cl2): δ 6.82-7.61 (m,
36H, Ph), 2.37 (s, 27H, tol-CH3), 2.62 (s, 6H, NMe2).
L ) P(p-ClC6H4)3. This complex was prepared by a procedure
analogous to that used for L ) P(o-tol)3 and was isolated in an 85%
yield as a pale brown solid. 31P NMR (101 MHz, CD2Cl2): δ 28.4 (s).
1H NMR (250 MHz, CD2Cl2): δ 6.64-7.75 (m, 36H, Ph), 2.78 (s,
6H, N-CH3).
L ) P(p-MeOC6H4)3. This complex was prepared by a procedure
analogous to that used for L ) P(o-tol)3 and was isolated in an 88%
yield as a pale brown solid. 31P NMR (250 MHz, CDCl3): δ 25.9 (s).
1H NMR (250 MHz, CDCl3): δ 6.74-7.39 (m, 36H, Ph), 2.85 (s, 6H,
N-CH3), 3.78 (s, 27H, O-CH3).
L ) P(p-FC6H4)3. This complex was prepared by a procedure
analogous to that used for L ) P(o-tol)3 and was isolated in an 83%
yield as a pale brown solid. 31P NMR (250 MHz, CDCl3): δ 27.5 (s).
1H NMR (250 MHz, CDCl3): δ 6.76-7.50 (m, 36H, Ph), 2.89 (s, 6H,
N-CH3).
L ) P(p-tol)3. This complex was prepared by a procedure analogous
to that used for L ) P(o-tol)3 and was isolated in an 78% yield as a
1
pale brown solid. 31P NMR (250 MHz, CDCl3): δ 27.9 (s). H NMR

608 Inorganic Chemistry, Vol. 39, No. 3, 2000
Flint et al.
the PMe2Ph derivative. Spectroscopic data (NMR and UV-vis) for
both derivatives agree with literature values.11
Method 2. Solid [(LAu)3(µ-NNMe2)]BF4 (15 mg) was mixed with
[PMe2Ph2]BF4 (5 mg) in a 5 mm NMR tube. CH2Cl2 (0.50 mL) was
added, and the sample was transferred to the NMR probe set at the
desired temperature. The sample was scanned every 2 min for a total
time of about 40 min, depending on the half-life of the compound.
Early time points (1-5 min), where the sample was thermally
equilibrating with the probe, were discarded. The signal from PMe2-
[(Ph3PAu)3(µ-NNEtMe2)](OTf)(BF4). Ethyl triflate (0.05 mmol, 8.0
mL) was added to a CH2Cl2 (2 mL) solution of [(Ph3PAu)3(µ-NNMe2)]-
BF4 (0.033 mmol, 50 mg). After 2 min, the yellow solid product was
precipitated with diethyl ether. Yield: 45 mg (88%). 31P NMR (250
1
MHz, CD2Cl2): δ 29.6 (s). H NMR (250 MHz, CD2Cl2): δ 7.25-
+
7.53 (m, 45H, Ph), 4.11 (q, JH-H ) 7.1 Hz, 2H, NCH2CH3), 1.80 (t,
3H, NCH2CH3), 3.66 (s, 6H, NMe2).
Ph2 was used as an internal integration standard for the reacting
hydrazido complex. This method gave results identical to those of
method 1 (L ) PPh3), indicating that the internal standard does not
alter the decomposition of the complex.
[(Ph3PAu)3(µ-NNRMe2)](OTf)2. R ) Et. This complex was
prepared in a manner similar to that of [(Ph3PAu)3(µ-NNEtMe2)](OTf)-
(BF4) above by using [(Ph3PAu)3(µ-NNMe2)]OTf in place of [(Ph3-
PAu)3(µ-NNMe2)]BF4. Yield: 95%. NMR spectroscopic data were
identical to those of the mixed salt above. Anal. calcd (found) for
C60H56Au3F6N2O6P3S2: C, 40.9 (41.6); H, 3.2 (3.2); N, 1.6 (1.6).
Crystals for the X-ray diffraction study were grown from a THF solution
layered with Et2O (-20 °C).
Acknowledgment. We thank the Division of Chemical
Sciences, Office of Basic Energy Sciences, Office of Energy
Research, U.S. Department of Energy (Grant DF-FG02-
88ER13880) for support of this work. Grants from the National
Science Foundation provided a portion of the funds for the
purchase of X-ray (CHE-9011804) and NMR (PCM-8115599
and CHE 89-08304) equipment. The University of Missouri
Research Council Board provided funding for upgrading the
data acquisition system of the mass spectrometer. We thank
Amanda Crawford for preliminary work on the decomposition
kinetics, Dr. Visalakshi Ramamoorthy for early synthetic work,
and Dr. D. Zagorevski for the mass spectral measurements.
R ) Me. This complex was prepared in a manner similar to that of
[(Ph3PAu)3(µ-NNEtMe2)](OTf)(BF4) above by using [(Ph3PAu)3(µ-
NNMe2)]OTf in place of [(Ph3PAu)3(µ-NNMe2)]BF4 and methyl triflate
in place of ethyl triflate. Yield: 95%. 31P NMR (250 MHz, CD2Cl2):
1
δ 29.7 (s). H NMR (250 MHz, CDCl3): δ 7.26-7.50 (m, 45H, Ph),
3.84 (s, 9H, NMe2).
Kinetic Measurements. Method 1 (L ) PPh3 Only). [(Ph3PAu)3-
(µ-NNMe2)]BF4 (5.8 mg) was dissolved in 0.70 mL of CH2Cl2. The
reaction was followed by monitoring the decrease in integrated 31P NMR
intensity of the resonance of the starting complex [(AuPPh3)3(µ-
NNMe2)]BF4 with respect to the increase in intensity of the resonance
of the product [(AuPPh3)6](BF4)2. 31P NMR spectra were recorded every
6 min for 1 h. The temperature was maintained at 298 K.
Supporting Information Available: Kinetic and Arrhenius plots
and tables and two X-ray crystallographic files, in CIF format. This
material is available free of charge via the Internet at http://pubs.acs.org.
IC990586U