Some organometallic chemistry of molybdenum complexes that contain the [HIPTN3N]3- triamidoamine ligand, {[3,5-(2,4,6.i.Pr 3C6H2)2C6H 3NCH2CH2]3N}3-

Article abstract of DOI:10.1021/om050373e

Reactions between [HIPTN₃N]Mo(N₂) and ethylene, acetylene, or CO yield Mo(η²-C₂H₄), Mo(η²-C₂H₂), and Mo(CO), respectively ([HIPTN₃N]^3- = [3,5-(2,4,6-i-Pr₃C ₆H₂)₂C₆H₃NCH _2- CH₂]₃N^3-; HIPT = hexaisopropylterphenyl; [HIPTN₃N]Mo = Mo). All are paramagnetic C₃ symmetric species. Attempts to prepare Mo(CO) through reduction of MoCl with Na/Hg in THF under carbon monoxide yielded [Mo(CO)]Na, in which the sodium ion is believed to be bound within the HIPT aryl system. Addition of a variety of acids such as [Et₃NH]BAr′₄ to [Mo(CO)]Na led to formation of the carbonyl hydride, Mo(CO)H, which also could be prepared by treating MoH with CO. Reactions between MoH and ethylene, 1-hexene, or 1-octene in benzene yield paramagnetic, red Mo(CH₂R) complexes (CH₂R = ethyl, hexyl, or octyl). MoMe could be prepared by treating MoCl with AlMe₃ at room temperature over a period of 2 days. Treatment of MoH with acetylene affords yellow diamagnetic Mo(η²- CHCH2) plus polyacetylene. The MoCH₂R complexes decompose at ～150 °C to yield the alkylidyne complexes, Mo=CR, quantitatively. No change was observed upon heating a toluene solution of MoCH3 to 160 °C for 24 h. However, Mo=CH could be prepared from a mixture of MoCl, 3 equiv of dichloromethane, and a large excess of magnesium powder in THF under argon at 90 °C. Although we have seen no evidence of thermal rearrangement of Mo(η²-CHCH₂) to Mo=CCH₃, that rearrangement is readily catalyzed by [2,6-LutH]BAr′4. Attempts to prepare Mo-C=CH from [Mo(NH₃)]BAr′ ₄ and NaC=CH led to formation of a yellow crystalline compound that was shown in an X-ray study to be one in which the acetylide had inserted into an ortho C-H bond in the phenyl ring attached to the amido nitrogen. Orange paramagnetic MoCN can be isolated in good yield from the reaction between [Mo(NH₃)]BPh₄ and [Bu₄N]CN in fluorobenzene. Electrochemical studies in 0.1 M [Bu ₄N]BAr′ ₄ in PhF at room temperature revealed reversible couples for Mo(C₂H₄)^+/0 and Mo(C₂H₂)^+/0 at -0.42 and -0.94 V, respectively, while Mo(CN) exhibits two redox processes at -0.27 and -1.61 V that we assign to the Mo(CN)^+/0 and Mo(CN)^0/- redox couples, respectively. Addition of [Cp₂Fe]BAr′ ₄ to a solution of Mo(η₂-C₂H₂) in C ₆D₆ produces diamagnetic [Mo(η²-C ₂H₂)]BAr′ ₄, while addition of [Cp ₂Fe]BAr'4 to a C₆D₆ solution of Mo(η²C₂H₄) led to formation of diamagnetic [Mo(C₂H₄)]BAr′ ₄. Structures of Mo(C ₂H₄), [Mo(C₂H₄)]BAr′ ₄, Mo(CH₂CH₃), and Mo(C=CH) were determined through X-ray studies.

Full text of DOI:10.1021/om050373e

Organometallics 2005, 24, 4437-4450
4437
Some Organometallic Chemistry of Molybdenum
Complexes that Contain the [HIPTN3N]3- Triamidoamine
Ligand, {[3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2CH2]3N}3-
Matthew J. Byrnes, Xuliang Dai, Richard R. Schrock,* Adam S. Hock, and
Peter Mu¨ller
Department of Chemistry 6-331, Massachusetts Institute of Technology,
Cambridge, Massachusetts 02139
Received May 10, 2005
Reactions between [HIPTN3N]Mo(N2) and ethylene, acetylene, or CO yield Mo(η2-C2H4),
Mo(η2-C2H2), and Mo(CO), respectively ([HIPTN3N]3- ) [3,5-(2,4,6-i-Pr3C6H2)2C6H3NCH2-
CH2]3N3-; HIPT ) hexaisopropylterphenyl; [HIPTN3N]Mo ) Mo). All are paramagnetic C3
symmetric species. Attempts to prepare Mo(CO) through reduction of MoCl with Na/Hg in
THF under carbon monoxide yielded [Mo(CO)]Na, in which the sodium ion is believed to be
bound within the HIPT aryl system. Addition of a variety of acids such as [Et3NH]BAr′4 to
[Mo(CO)]Na led to formation of the carbonyl hydride, Mo(CO)H, which also could be prepared
by treating MoH with CO. Reactions between MoH and ethylene, 1-hexene, or 1-octene in
benzene yield paramagnetic, red Mo(CH2R) complexes (CH2R ) ethyl, hexyl, or octyl). MoMe
could be prepared by treating MoCl with AlMe3 at room temperature over a period of 2
days. Treatment of MoH with acetylene affords yellow diamagnetic Mo(η2-CHCH2) plus
polyacetylene. The MoCH2R complexes decompose at ∼150 °C to yield the alkylidyne
complexes, MotCR, quantitatively. No change was observed upon heating a toluene solution
of MoCH3 to 160 °C for 24 h. However, MotCH could be prepared from a mixture of MoCl,
3 equiv of dichloromethane, and a large excess of magnesium powder in THF under argon
at 90 °C. Although we have seen no evidence of thermal rearrangement of Mo(η2-CHCH2)
to MotCCH3, that rearrangement is readily catalyzed by [2,6-LutH]BAr′4. Attempts to
prepare Mo-CtCH from [Mo(NH3)]BAr′4 and NaCtCH led to formation of a yellow
crystalline compound that was shown in an X-ray study to be one in which the acetylide
had “inserted” into an ortho C-H bond in the phenyl ring attached to the amido nitrogen.
Orange paramagnetic MoCN can be isolated in good yield from the reaction between
[Mo(NH3)]BPh4 and [Bu4N]CN in fluorobenzene. Electrochemical studies in 0.1 M [Bu4N]-
BAr′4 in PhF at room temperature revealed reversible couples for Mo(C2H4)+/0 and
Mo(C2H2)+/0 at -0.42 and -0.94 V, respectively, while Mo(CN) exhibits two redox processes
at -0.27 and -1.61 V that we assign to the Mo(CN)+/0 and Mo(CN)0/- redox couples,
respectively. Addition of [Cp2Fe]BAr′4 to a solution of Mo(η2-C2H2) in C6D6 produces
diamagnetic [Mo(η2-C2H2)]BAr′4, while addition of [Cp2Fe]BAr′4 to a C6D6 solution of Mo(η2-
C2H4) led to formation of diamagnetic [Mo(C2H4)]BAr′4. Structures of Mo(C2H4), [Mo(C2H4)]-
BAr′4, Mo(CH2CH3), and “Mo(CtCH)” were determined through X-ray studies.
Introduction
Mo(N2), Mo-NdNH, [ModN-NH2]+, MotN, [Mo(NH3)]+,
and MoH), a proton source ([2,6-lutidinium]BAr′4 where
Ar′ ) 3,5-(CF3)2C6H3), and an electron source (e.g.,
decamethylchromocene).3,6 Steric protection of partially
reduced nitrogen entities within the trigonally sym-
metric pocket against bimolecular decomposition reac-
tions is believed to be one of the reasons why many
potential intermediates can be prepared and why cata-
lytic reduction of dinitrogen to ammonia is possible at
a single metal center. However, it should be noted that
analogous hexamethylterphenyl and hexa-tert-butylter-
phenyl derivatives yield little or no ammonia (respec-
tively) from dinitrogen under the same conditions as the
hexaisopropylterphenyl derivatives,4 so proper tuning
of the steric protection is crucial.
We have been studying chemistry of Mo and W
complexes that contain the triamidoamine ligand
[HIPTN3N]3- (where [HIPTN3N]3- ) [3,5-(2,4,6-i-Pr3-
C6H2)2C6H3NCH2CH2]3N3-; HIPT ) hexaisopropylter-
phenyl; [HIPTN3N]Mo ) Mo), which is relevant to the
reduction of dinitrogen to ammonia.1-6 We have shown
that dinitrogen can be reduced catalytically to ammonia
in heptane in the presence of Mo complexes (e.g.,
(1) Yandulov, D. V.; Schrock, R. R. J. Am. Chem. Soc. 2002, 124,
6252.
(2) Yandulov, D. V.; Schrock, R. R.; Rheingold, A. L.; Ceccarelli, C.;
Davis, W. M. Inorg. Chem. 2003, 42, 796.
(3) Yandulov, D. V.; Schrock, R. R. Science 2003, 301, 76.
(4) Ritleng, V.; Yandulov, D. V.; Weare, W. W.; Schrock, R. R.; Hock,
A. R.; Davis, W. M. J. Am. Chem. Soc. 2004, 126, 6150.
(5) Yandulov, D. V.; Schrock, R. R. Can. J. Chem. 2005, 83, 341.
(6) Yandulov, D. V.; Schrock, R. R. Inorg. Chem. 2005, 44, 1103.
Although this is the first time that dinitrogen has
been reduced catalytically in a relatively well-defined
10.1021/om050373e CCC: $30.25 © 2005 American Chemical Society
Publication on Web 08/02/2005

4438 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
manner,7 it is not known whether these observations
have any bearing on the question as to how dinitrogen
is reduced to ammonia by molybdenum-containing
nitrogenases.8-22 Although dinitrogen almost certainly
is reduced at a MoFe7S9 cluster within the enzyme, the
detailed structure of which has been elucidated in
considerable detail in the past decade,11,16-18,23-25 it is
fair to say that we still do not know exactly how
dinitrogen is reduced in the MoFe nitrogenase.
The MoFe nitrogenase is known to reduce many
substrates besides dinitrogen, among them acetylene
and isonitriles.9,22,26 Therefore we have the opportunity
to determine to what extent certain organometallic Mo
derivatives will serve as catalyst precusors for formation
of ammonia, and whether and how substrates other
than dinitrogen might be reduced. This is one reason
we have begun to explore some simple organometallic
chemistry of Mo. Another reason is that we have
explored a good deal of relatively simple organometallic
chemistry of triamidoamine ([RN3N]3- ) [(RNCH2CH2)3-
N]3-) complexes of Mo and W (where R is trimethyl-
silyl or pentafluorophenyl)27-33 as well as [Me3SiN3N]3-
complexes of tantalum34-36 in the past decade. Although
we have shown that many new and interesting species
can be prepared and new reactions carried out within
the trigonal coordination pocket, complexes that contain
the [HIPTN3N]3- ligand are likely to be much more
stable against various decomposition reactions than
complexes that contain [TMSN3N]3- or [C6F5N3N]3-
ligands. For example, in [TMSN3N]W complexes both
silyl migration and CH activation in a silyl methyl group
have been observed.32 Therefore it will be of interest to
determine what type of organometallic chemistry will
be possible in relatively robust Mo systems compared
with that observed in other [RN3N]Mo systems.
Results and Discussion
Reactions that Involve Replacement of Dinitro-
gen from [HIPTN3N]Mo(N2). Ethylene (1 atm) reacts
with Mo(N2) (Mo ) [HIPTN3N]Mo) in benzene at room
temperature over a period of 2 days to yield rose-red
paramagnetic Mo(C2H4). The reaction proceeds much
more readily at 60 °C under 1 atm of ethylene. However,
the most convenient and most direct synthesis of
Mo(C2H4) consists of the reduction of MoCl with an
excess of 0.5% Na amalgam in THF under an ethylene
atmosphere (eq 1). The corresponding 13C-labeled com-
(7) The only other known catalytic reduction of dinitrogen was
discovered by Shilov over twenty years ago (Shilov, A. E. Russ. Chem.
Bull. Int. Ed. 2003, 52, 2555). This system requires and is catalytic
with respect to Mo, employs a strong reducing agent and methanol as
the solvent, and yields a mixture of ammonia and hydrazine in which
ammonia constitutes <10% (1 part in 11) of the mixture. The amount
of dihydrogen produced is not known, and the mechanism of reduction
has not been elucidated.
(8) Burgess, B. K. Chem. Rev. 1990, 90, 1377.
(9) Burgess, B. K.; Lowe, D. J. Chem. Rev. 1996, 96, 2983.
(10) Rees, D. C.; Howard, J. B. Curr. Opin. Chem. Biol. 2000, 4,
559.
plex was prepared readily in a similar manner. The
proton NMR spectrum of Mo(C2H4) shows no resonances
for the backbone or ethylene methylene groups, only
broad resonances at 7.18, 2.88, and 1.34 ppm for
aromatic, isopropyl methine, and isopropyl methyl
groups, respectively. Upfield-shifted ligand backbone
methylene resonances also have not been observed in
other ethylene complexes in this general category, e.g.,
[TMSN3N]Mo(C2H4) and [C6F5N3N]Mo(C2H4).31
(11) Rees, D. C.; Chan, M. K.; Kim, J. Adv. Inorg. Chem. 1996, 40,
89.
(12) Eady, R. R. Chem. Rev. 1996, 96, 3013.
(13) Howard, J. B.; Rees, D. C. Chem. Rev. 1996, 96, 2965.
(14) Kim, J.; Rees, D. C. Nature 1992, 360, 553.
(15) Kim, J.; Woo, D.; Rees, D. C. Biochemistry 1993, 32, 7104.
(16) Bolin, J. T.; Ronco, A. E.; Morgan, T. V.; Mortenson, L. E.;
Xuong, L. E. Proc. Nat. Acad. Sci. 1993, 90, 1078.
(17) Chen, J.; Christiansen, J.; Campobasso, N.; Bolin, J. T.;
Tittsworth, R. C.; Hales, B. J.; Rehr, J. J.; Cramer, S. P. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 1592.
An X-ray study showed the ethylene complex to have
the expected structure (Figure 1, Tables 1 and 2). The
ethylene is oriented approximately perpendicular to the
Mo-N(3) vector. The Mo-C bond lengths are 2.190(7)
and 2.196(7) Å, while the C(1)-C(2) bond length is
1.369(10) Å. The Mo-Namido bond lengths are all near
2.00 Å, and the Mo-Namine bond length is 2.211(5) Å;
all are typical for compounds of this general type. The
only slight lengthening of the C(1)-C(2) bond from what
it is in free ethylene suggests that Mo(η2-C2H4) is best
viewed as a low-spin Mo(III) ethylene complex with
three electrons in the frontier π orbitals (dxz and dyz),
instead of a molybdacyclopropane (Mo(V)) complex. This
compound should be compared to other ethylene com-
plexes in the general class of triamidoamine complexes
of Ta,34 Mo,31 and W,31 although Mo(C2H4) is the only
derivative whose structure has been determined in an
X-ray study.
(18) Einsle, O.; Tezcan, F. A.; Andrade, S. L. A.; Schmid, B.; Yoshida,
M.; Howard, J. B.; Rees, D. C. Science 2002, 297, 1696.
(19) Hardy, R. W. F.; Bottomley, F.; Burns, R. C. A Treatise on
Dinitrogen Fixation; Wiley-Interscience: New York, 1979.
(20) Christiansen, J.; Dean, D. R.; Seefeldt, L. C. Annu. Rev. Plant.
Physiol. Plant. Mol. Biol. 2001, 52, 269.
(21) Dos Santos, P. C.; Igarashi, R. Y.; Lee, H.; Hoffman, B. M.;
Seefeldt, L. C.; R., D. D. Acc. Chem. Res. 2005, 38, 208.
(22) Burgess, B. K. In Molybdenum Enzymes; Spiro, T. G., Ed.;
Wiley: New York, 1985; p 161.
(23) Kim, J.; Rees, D. C. Science 1992, 257, 1677.
(24) Chan, M. K.; Kim, J. S.; Rees, D. C. Science 1993, 260, 792.
(25) Grossmann, J. G.; Hasnain, S. S.; Yousafzai, F. K.; Smith, B.
E.; Eady, R. R.; Schindelin, H.; Kisker, C.; Howard, J. B.; Tsuruta, H.;
Muller, J.; Rees, D. C. Acta Crystallogr. Sect. D: Biol. Crystallogr. 1999,
55, 727.
(26) Burgess, B. K. ACS Symp. Ser. 1993, 535, 144.
(27) Shih, K.-Y.; Totland, K.; Seidel, S. W.; Schrock, R. R. J. Am.
Chem. Soc. 1994, 116, 12103.
(28) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Shih, K.-Y.;
O’Donoghue, M. B.; Davis, W. M.; Reiff, W. M. J. Am. Chem. Soc. 1997,
119, 11876.
(29) Seidel, S. W.; Schrock, R. R.; Davis, W. M. Organometallics
1998, 17, 1058.
(30) Schrock, R. R.; Rosenberger, C.; Seidel, S. W.; Shih, K.-Y.; Davis,
W. M.; Odom, A. L. Organometallics 2001, 617-618, 495.
(31) Greco, G. E.; O’Donoghue, M. B.; Seidel, S. W.; Davis, W. M.;
Schrock, R. R. Organometallics 2000, 19, 1132.
(32) Schrock, R. R.; Seidel, S. W.; Mo¨sch-Zanetti, N. C.; Dobbs, D.
A.; Shih, K.-Y.; Davis, W. M. Organometallics 1997, 16, 5195.
(33) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9.
(34) Freundlich, J. S.; Schrock, R. R.; Davis, W. M. J. Am. Chem.
Soc. 1996, 118, 3643.
Reaction of Mo(N2) with 2-10 equiv of dry and
oxygen-free acetylene affords paramagnetic, emerald
green Mo(C2H2) in good yield (eq 2) along with an
(35) Freundlich, J. S.; Schrock, R. R.; Davis, W. M. Organometallics
1996, 15, 2777.
(36) Freundlich, J.; Schrock, R. R.; Cummins, C. C.; Davis, W. M.
J. Am. Chem. Soc. 1994, 116, 6476.

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4439
Table 1. Crystal Data and Structure Refinement for [HIPTN3N]Mo(C2H4), [HIPTN3N]Mo(CH2CH3),
a
“[HIPTN3N]Mo(CCH)”, and {[HIPTN3N]Mo(C2H4)}BAr′4
Mo(C2H4)
Mo(CH2CH3)
“Mo(CCH)”
[Mo(C2H4)]+
empirical formula
fw
C119.50H167MoN4
1755.51
C119.50H171.50MoN4
1760.05
C122.75H173.50MoN4
1801.10
C153H186.50BF24MoN4
2644.31
temp (K)
193(2)
100(2)
100(2)
100(2)
cryst syst
space group
unit cell dimens (Å, deg)
monoclinic
P2(1)/c
monoclinic
P2(1)/c
trigonal
P3hc1
monoclinic
C2/c
a ) 16.063(4)
b ) 19.355(5)
c ) 35.056(9)
R ) 90
a ) 16.1387(7)
b ) 19.6879(10)
c ) 34.1544(17)
R ) 90°
a ) 43.616(3)
b ) 43.616(3)
c ) 24.703(3)
R ) 90
a ) 51.612(3)
b ) 19.3084(10)
c ) 32.2092(17)
R ) 90
â ) 91.478(8)
γ ) 90
â ) 93.147(2)
γ ) 90
â ) 90
γ ) 120
â ) 111.507(2)
γ ) 90
volume (Å3)
10895(5)
10835.8(9)
4
40697(7)
12
29863(3)
Z
4
8
density (calcd; Mg/m3)
1.070
1.079
0.882
1.176
absorp coeff (mm-1
F(000)
)
0.167
0.168
0.136
0.166
3816
3834
11760
11164
cryst size (mm3)
θ range (deg)
index ranges
0.20 × 0.15 × 0.10
1.16 to 20.81
-16 e h e 16
-19 e k e 19
-30 e l e 35
36 731
0.25 × 0.20 × 0.10
1.58 to 26.02
-19 e h e 19
-24 e k e 24
-41 e l e 42
189 662
0.20 × 0.15 × 0.10
1.65 to 18.00
-32 e h e 0
0 e k e 37
0 e l e 21
246 843
0.37 × 0.25 × 0.20
1.60 to 24.71
-60 e h e 56
0 e k e 22
0 e l e 37
234 477
no. of reflns collected
no. of indep reflns
compl to θ ) 20.81° (%)
max. and min. transmn
11 392 [R(int) ) 0.0995] 21 355 [R(int) ) 0.0968] 9347 [R(int) ) 0.1405] 25 477 [R(int) ) 0.0495]
100.0
0.9835 and 0.96730
100.0
99.9
100.0
.9834 and 0.9591
21 355/487/1177
1.034
0.9866 and 0.9734
9347/1689/1210
2.411
0.9676 and 0.9411
25 477/5569/2246
1.053
no. of data/restraints/params 11 392/1550/1211
goodness-of-fit on F2
1.027
final R indices [I>2σ(I)]
R1 ) 0.0668
wR2 ) 0.1584
R1 ) 0.1217
wR2 ) 0.1858
0.775 and -0.511
R1 ) 0.0473
wR2 ) 0.1061
R1 ) 0.0778
wR2 ) 0.1191
0.912 and -0.588
R1 ) 0.1178
wR2 ) 0.3227
R1 ) 0.1382
wR2 ) 0.3300
1.215 and -0.434
R1 ) 0.0849
wR2 ) 0.2135
R1 ) 0.1216
wR2 ) 0.2594
2.110 and -1.700
R indices (all data)
peak and hole (e Å-3
)
a In all cases the wavelength was 0.71073 Å, the refinement method was full-matrix least-squares on F2,and the absorption correction
was semiempirical from equivalents. [BAr′4]- ) {B[3,5-(CF3)2C6H3]4}-.
in a similar manner. No residual Mo(N2) can be detected
in IR spectra (as Nujol mulls). In Mo(C2H2) a relatively
weak absorption at 1637 cm-1 is assigned as the νCC
stretch of the coordinated alkyne on the basis of the
absence of this absorption in the 13C-labeled compound
and a new shoulder at 1582 cm-1 that is close to the
calculated νCC frequency of 1578 cm-1 expected in
the13C-labeled species. As in Mo(C2H4), upfield-shifted
ligand backbone methylene resonances are not observed.
An attempted X-ray structure of Mo(C2H2) showed the
acetylene to be bonded to the metal in the expected
fashion (η2-C2H2), although the acetylene was disordered
over three orientations within the coordination pocket.
The disorder was not resolved satisfactorily, and there-
fore the structure will not be discussed in detail. In
[TMSN3N]Ta(η2-C2H2) the acetylene was found to line
up approximately along one of the Ta-N bond vectors.34
Figure 1. Molecular structure of [HIPTN3N]Mo(C2H4).
The Mo atom and all atoms directly bonded to it are drawn
in their 50% thermal ellipsoid representations, with the
other atoms as circles of arbitrary radius. Hydrogen atoms,
disorders of isopropyl groups, and solvent molecules have
been omitted for clarity.
A solution of Mo(C2H4) in C6D6 was exposed to several
equivalents of C2H2 in a J-Young tube. Polyacetylene
formed over a period of 5 min, and the 1H NMR
spectrum indicated that virtually all of the acetylene
had been consumed. However, no Mo(C2H2) or free C2H4
could be detected. Apparently ethylene is not replaced
by acetylene rapidly under these conditions. The mech-
anism through which acetylene is polymerized in these
systems is not known. Propagation must be fast com-
pared to initiation, since little Mo(C2H4) appears to be
consumed in the process.
insoluble purple-black solid that we assume to be
polyacetylene. This reaction, unlike the reaction be-
When a solution of Mo(N2) in benzene was exposed
to CO (1 atm) and heated to ∼60 °C overnight, the color
changed from brown to red. Upon removal of all volatiles
in vacuo, red Mo(CO) could be isolated virtually quan-
tween Mo(N2) and ethylene, is rapid (seconds) at room
temperature. The 13C-labeled compound can be prepared

4440 Organometallics, Vol. 24, No. 18, 2005
Table 2. Selected Bond Distances (Å) and Angles (deg) for [HIPTN3N]Mo(C2H4),
Byrnes et al.
{[HIPTN3N]Mo(C2H4)}BAr′4, “[HIPTN3N]Mo(CCH)”, and [HIPTN3N]Mo(CH2CH3)
Mo(C2H4)
[Mo(C2H4)]+
“Mo(CCH)”
Mo(CH2CH3)
Mo-N(1)
1.989(5)
2.000(4)
1.979(5)
2.211(5)
2.190(7)
2.196(7)
1.369(10)
114.66(19)
115.7(2)
79.1(2)
118.82(19)
79.14(18)
78.52(19)
72.0(4)
71.6(4)
36.4(3)
1.958(4)
1.991(5)
1.965(4)
2.262(4)
2.155(7)
2.250(6)
1.315(10)
111.93(18)
121.09(16)
76.42(14)
111.72(16)
78.67(16)
75.51(15)
76.6(4)
1.968(9)
1.965(9)
1.996(8)
2.263(9)
1.924(11)
2.232(12)
1.429(15)
115.8(4)
118.1(3)
78.8(4)
1.9804(19)
1.9826(19)
1.9828(18)
2.276(2)
Mo-N(2)
Mo-N(3)
Mo-N(4)
Mo-C(1)
2.179(3)
Mo-C(2)
C(1)-C(2)
1.514(3)
N(1)-Mo-N(2)
N(1)-Mo-N(3)
N(1)-Mo-N(4)
N(2)-Mo-N(3)
N(2)-Mo-N(4)
N(3)-Mo-N(4)
C(2)-C(1)-Mo
C(1)-C(2)-Mo
C(1)-Mo-C(2)
119.31(8)
115.51(8)
79.57(8)
116.5(3)
78.5(3)
115.22(8)
78.93(8)
79.65(8)
120.91(17)
99.13(9)a
178.25(9)b
81.5(3)
82.1(7)
68.7(4)
58.6(6)
34.7(2)
39.3(4)
a N(3)-Mo-C(1). b C(1)-Mo-N(4).
titatively. A sharp, strong absorption was found at 1892
cm-1 in the IR spectrum (in Nujol), which is close to
the νCO value reported for [C6F5N3N]Mo(CO) (νCO(Nujol)
Na or [Mo(CO)]Na(18-C-6), the color changed to yellow
and a new diamagnetic compound could be isolated
along with small amounts of free ligand and Mo(CO).
) 1889 cm-1 31
)
and slightly greater than that for
A
13C{1H} NMR spectrum of the 13CO derivative re-
[TMSN3N]Mo(CO) (νCO(Nujol) ) 1841 and 1832 cm-1).31
Broad resonances in the 1H NMR spectrum of Mo(CO)
at +19.79 and -30.12 ppm are assigned to the ligand
backbone (NCH2) resonances. These should be compared
with backbone methylene resonances at 13.17 and
-38.04 ppm in [TMSN3N]Mo(CO) and 12.85 and -23.90
ppm in [C6F5N3N]Mo(CO).31
vealed a singlet at 200.5 ppm which appeared as a
doublet in the proton-coupled 13C NMR spectrum with
a C-H coupling of 24.5 Hz. A doublet that we assign to
the MoH proton was also found in the 1H NMR
spectrum at -0.08 ppm with a C-H coupling value of
24.3 Hz. This diamagnetic product is believed to be the
hydrido-carbonyl complex Mo(H)(CO), as shown in eq
4, rather than MotCOH, on the basis of comparison of
NMR and IR data with data for [TMSN3N]W(H)(CO),
whose structure has been determined in an X-ray
study.37 The IR spectrum of Mo(H)(CO) shows a νCO
An attempt to prepare Mo(CO) through reduction of
MoCl with 0.5% Na/Hg in THF under carbon monoxide
yielded [Mo(CO)]Na as a yellow-orange crystalline solid
after recrystallization from either heptane or pentane
1
(eq 3). Since there are no resonances in the H NMR
spectrum for THF, the sodium ion is likely to be
coordinated to the oxygen and to the aromatic rings of
HIPT in a manner similar to that found in {[HIPTN3N]-
WN2}K.5 The 13C-labeled analogue, [Mo(13CO)]Na, dis-
played a singlet at +232.5 ppm in the 13C{1H} NMR
spectrum. This chemical shift should be compared to
stretch at 1853 cm-1 (in C6D6), which shifts to 1810 cm-1
(in C6D6) in the 13CO derivative. No Mo-H stretches
are obvious in IR spectra. The CO stretch in [TMSN3-
N]W(H)(CO) is found at 1766 cm-1. The hydride reso-
nance in [TMSN3N]W(H)(CO) was located at 2.80 ppm
in the 1H NMR spectrum with JHCR ) 12 Hz (in the 13C-
labeled compound) and JWCR ) 15.6 Hz. In the tungsten
13C-labeled complex the CO stretch was found at 1727
cm-1 and the chemical shift in the 13C{1H} NMR spec-
trum was 209 ppm with JWC ) 133 Hz. Mo(H)(CO) also
can be prepared by treating MoH (see below) with CO.
Reactions that Involve [HIPTN3N]MoH. The re-
action between MoH and ethylene in benzene yields
paramagnetic, red Mo(CH2CH3) quantitatively (eq 5).
that found for the carbonyl carbon in {[C6F5N3N]Mo-
(CO)}Na(15-crown-5) (226.7 ppm) and {[C6F5N3N]W-
(CO)}Na(15-crown-5) (224.2 ppm).31 The “oxycarbyne”
description shown in eq 3 is of course an extreme, but
it is consistent with the relatively low energy νCO
observed in [Mo(CO)]Na and [Mo(13CO)]Na at 1632 and
1601 cm-1, respectively. These values are lower than
those reported for {[C6F5N3N]Mo(CO)}Na(15-crown-5)
(1701 cm-1) and {[C6F5N3N]W(CO)}Na(THF)3 (1726
cm-1), but similar to that reported for {[C6F5N3N]W-
(CO)}Na(15-crown-5) (1628 cm-1).31 Attempts to prepare
[TMSN3N]Mo(CO) or [C6F5N3N]Mo(CO) directly through
reduction of [TMSN3N]MoCl or [C6F5N3N]MoCl under
CO with strong reducing agents (e.g., sodium amalgam)
also led to formation of {[RN3N]Mo(CO)}- species.
Upon addition of 1 equiv of [H(Et2O)2]BAr′4, [3,5-
LutH]BAr′4, or [Et3NH]BAr′4 to a solution of [Mo(CO)]-
(37) Dobbs, D. A.; Schrock, R. R.; Davis, W. M. Inorg. Chim. Acta
1997, 263, 171.

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4441
assigned to the alkylidene-like η2-HCCH2 proton of the
“η2-vinyl” group. The resonance due to the HCCH2
protons is obscured by one of the broad triplets ascribed
to the methylene backbone protons at 2.90 ppm. In the
proton NMR spectrum of the 13C-labeled analogue two
broad doublets are observed at 13.02 ppm (JCH ) 192
Hz) and 2.93 ppm (JCH ) 160 Hz) for the HCCH2 and
HCCH2 protons, respectively, while doublets are ob-
served at 272.18 and 44.78 ppm (JCC ) 41 Hz) in the
13C{1H} NMR spectrum for the HCCH2 and HCCH2
carbon atoms of the η2-vinyl group, respectively. These
values should be compared with those known for
[TMSN3N]W(PhCCH2) (3.65 ppm for WCPhCH2, 242.5
ppm for WCPhCH2, and 56.58 ppm for WCPhCH2). The
connectivity in Mo(η2-CHCH2) has been confirmed in
an X-ray crystallographic study, although the presence
of Mo(C2H2) as a cocrystallized impurity prevented a
high-quality solution. The observed C3 symmetry in
Mo(η2-CHCH2) and [TMSN3N]W(η2-PhCCH2) and simi-
lar species on the NMR time scale can be ascribed to
the degeneracy of the dxz and dyz orbitals involved in
bonding of the η2-vinyl ligand to the metal and therefore
facile “rotation” of the η2-vinyl group about the z axis.
(It is not necessary to postulate an η2-vinyl to η1-vinyl
interconversion, although that possibility cannot be
excluded.) It is normal to observe C3 symmetry in d0
compounds in this general category, e.g., even in
[TMSN3N]W(cyclopentylidene)H.32
Figure 2. Molecular structure of [HIPTN3N]Mo(CH2CH3).
The Mo atom and all atoms directly bonded to it are drawn
in their 50% thermal ellipsoid representations, with the
other atoms as circles of arbitrary radius. Hydrogen atoms,
disorders of isopropyl groups, and solvent molecules have
been omitted for clarity.
Upfield resonances characteristic of methylene backbone
protons in Mo(IV) complexes of this general type (e.g.,
[TMSN3N]MoR where R ) Me, Et, Bu, CH2Ph, CH2-
SiMe3, etc.28) were found in the proton NMR spectrum
at -25.89 and -75.90 ppm. The relative areas of the
-75.90 ppm resonance versus the -25.89 ppm reso-
nance suggest that the ethyl’s methyl resonance is
coincident with a -75.90 ppm resonance. In [TMSN3-
N]Mo(CH2CH3) the ligand backbone methylene reso-
nances were found at -25.05 and -60.0 ppm, with the
ethyl’s methyl resonance at -51.5 ppm.28 No resonances
for the ethyl carbons in Mo(CH2CH3) could be observed
in the 13C NMR spectrum of Mo(13CH213CH3).
Alkylidynes. Upon heating a toluene solution of
Mo(CH2CH3) (generated in situ by reacting Mo-H with
excess ethylene) to 160 °C in a closed flask, it decom-
poses smoothly to give MotCCH3 in 63% isolated yield.
An NMR scale reaction carried out in toluene-d8 showed
that conversion of MotCCH3 to Mo(CH2CH3) was
quantitative (eq 7). NMR spectra of MotCCH3 are
An X-ray structure of Mo(CH2CH3) (Figure 2 and
Tables 1 and 2) showed it to contain a normal ethyl
ligand, as shown by the Mo-C(1) bond length (2.179(3)
Å), the C(1)-C(2) bond length (1.514(3) Å), and the Mo-
C(1)-C(2) angle (120.91(17)°). Therefore we believe any
R or â agostic interaction is unlikely. Agostic interac-
tions also seem unlikely since only two orbitals (dxz and
dyz) are available for either interaction and one electron
is present in each of these orbitals. The structure of
Mo(CH2CH3) should be compared to the structures of
[TMSN3N]Mo(CD3) and [TMSN3N]Mo(cyclohexyl).28
Analogous reactions between MoH and 1-hexene or
1-octene yield Mo(hexyl) and Mo(octyl), respectively. We
assume that the alkyls are terminal, although we cannot
exclude the possibility that they are internal on the
basis of the information in hand. As expected, both
compounds are paramagnetic, exhibiting backbone
methylene resonances around -10 and -68 ppm in 1H
NMR spectra in C6D6. In both compounds a very broad
peak at -52 ppm is observable, which we believe to be
a resonance either for a methylene group in the alkyl
chain or for the methyl group at the end of the chain.
The reaction of MoH with 2-5 equiv of acetylene
affords yellow diamagnetic Mo(η2-CHCH2) (eq 6). A
purple-black solid is also formed, which we again believe
straightforward and typical of Mo(VI) or W(VI) alkyli-
dyne complexes.38 The alkylidyne carbon resonance was
found at 299.3 ppm in C6D6. The rate of formation of
MotCCH3 was determined by observing the growth of
resonances in the proton NMR spectrum at 3.68 and
2.32 ppm in C6D6, which correspond to one set of
methylene backbone protons and the methyl protons of
the ethylidyne ligand, respectively. A plot of ln(1-F) vs
time (where F is the fraction of alkylidyne formed versus
time) showed the reaction to be first order in Mo with
rate constants 2.76(26) × 10-5 s-1 (using the 3.68 ppm
resonance) and 2.36(7) × 10-5 s-1 (using the 2.32 ppm
resonance), or k ≈ 2.5 × 10-5 s-1 (half-life ∼460 min)
1
to be polyacetylene. The H NMR spectrum of Mo(η2-
CHCH2) is characteristic of a diamagnetic compound
with C3 symmetry analogous to [TMSN3N]W(η2-Ph-
CCH2) and [TMSN3N]W(η2-PhCCHPh).37 A triplet reso-
nance at 13.03 ppm corresponds to one proton and is
(38) Murdzek, J. S.; Schrock, R. R. In Carbyne Complexes; VCH:
New York, 1988.

4442 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
at 145 °C. Evolution of dihydrogen from Mo and
(primarily) W alkyl complexes in an R,R dehydrogena-
tion reaction is well-documented for [TMSN3N]MCH2R
species27,28,32 and to a lesser extent for [C6F5N3N]-
MCH2R species (M ) Mo or W).29 However, the only
[TMSN3N]Mo(n-alkyl) species that evolves dihydrogen
cleanly is [TMSN3N]Mo(neopentyl), since neopentyl
most easily undergoes processes that involve one or
more R hydrogen atoms(R abstraction, R elimination, or
R,R dehydrogenation).39 In other [TMSN3N]Mo(n-alkyl)
complexes decomposition takes place before, or in
competition with, loss of dihydrogen. The stability of the
[HIPTN3N]3- system toward intermolecular decomposi-
tion reactions and intramolecular decomposition reac-
tions (e.g., CH cleavage32) therefore allows the relatively
high temperature to be reached that is required for the
R,R dehydrogenation reaction in [RN3N]Mo(n-alkyl)
complexes to take place without complications. R,R
Dehydrogenation reactions for [TMSN3N]W(CH2R) com-
plexes are believed to be orders of magnitude faster than
for [TMSN3N]Mo(CH2R) complexes, so much so that
[TMSN3N]W(CH3) is the only observable [TMSN3N]W-
(CH2R) species. (R,R Dehydrogenation in methyl species
is believed to be the slowest by orders of magnitude.)
Unfortunately no direct comparison of the rates for Mo
and W have been possible to date. Addition of ethylene
to [TMSN3N]WH is known to lead to [TMSN3N]Wt
CCH3 at room temperature, presumably via formation
of [TMSN3N]WCH2CH3 followed by loss of dihydrogen.37
First-order decompositions of Mo(CH2CH3) and Mo-
(hexyl) were followed side by side in C6D5CD3 at 152 (
1 °C in sealed J-Young tubes with triphenylmethane as
the internal standard. The rates of formation of Mot
CCH3 and MotCC5H11 were determined by observing
the growth of a resonance for the methylene backbone
protons in the proton NMR spectra of the alkylidyne
complexes near 3.7 ppm. The rate constants were found
to be 1.00(3) × 10-4 and 1.20(5) × 10-4 s-1, respectively.
Decomposition of [HIPTN3N]Mo(hexyl) in the pres-
ence of 5 equiv of 1-octene led to formation of a statis-
tical mixture of [HIPTN3N]MotCC5H11 and [HIPTN3N]-
MotCC7H15 (∼1:6), according to carbon NMR spectra
of the resulting mixture. Therefore it appears that â
hydride elimination to form the olefin and MoH is fast
relative to R,R dehydrogenation to give the alkylidyne
species, although that equilibrium lies far to the side
of the alkyl complexes.
[N(t-Bu)Ar]3MotCCH2SiMe3 (Ar ) 3,5-Me2C6H3) and
their conversion to (AdO)3MotCR species upon treat-
ment with 1-adamantanol.40 In 1999, Fu¨rstner reported
that Mo[N(t-Bu)Ar]3 reacted readily at room tempera-
ture with CH2Cl2 to produce a mixture of [N(t-Bu)-
Ar]3MoCl and [N(t-Bu)Ar]3MotCH.41 In 2003 Moore42
reported that compounds of the type [N(t-Bu)Ar]3Mot
CR (R ) H, Me, Et) could be prepared readily in good
yield from [N(t-Bu)Ar]3Mo or [N(t-Bu)Ar]3MoCl in the
presence of magnesium and RCH2Cl2 in THF and that
these species could be used as precursors to triphenoxide
alkylidyne complexes of the type that are known to
metathesize alkynes.38,43,44 Therefore, to synthesize
[HIPTN3N]MotCH, we adopted a strategy analogous
to that employed by Moore.
A mixture of MoCl, 3 equiv of dichloromethane, and
a large excess of magnesium powder in THF was heated
at 90 °C in vacuo in a sealed tube for 16 h. A proton
NMR spectrum showed that MoCl had been consumed
completely and MotCH had formed in good yield (eq
8). (Dinitrogen must be avoided in order to prevent
formation of magnesium derivatives of {Mo-NdN}-.2,6
)
The yield of yellow MotCH is ∼65%, although the high
solubility of this compound in pentane is at least
partially responsible for the modest isolated yield. The
details of how such reactions proceed are not known.
The NMR spectrum of MotCH is unremarkable. The
methylidyne proton resonance is found at 4.46 ppm,
while the alkylidyne carbon resonance is found at 288.4
ppm. For comparison the proton and carbon methyli-
dyne resonances in [TMSN3N]MotCH are found at 5.54
and 284.3 ppm,28 respectively, and in [(3,5-Me2C6H3)(t-
Bu)N]3MotCH at 5.66 and 287.5 ppm,45,46 respectively.
An attempt to prepare MotCMe under analogous
conditions from MeCHCl2 and MoCl gave <5% of Mot
CMe. The sterically crowded nature of the [HIPTN3N]3-
ligand is likely to be a significant factor preventing
ready formation of MotCMe.
As in the case of [TMSN3N]Mo(CH3),28 all attempts
to promote loss of hydrogen from Mo(CH3) (see below
for the synthesis) did not produce MotCH. No change
was observed upon heating a toluene solution of MoCH3
to 160 °C for 24 h. However, since [TMSN3N]MotCH
could be prepared by heating [TMSN3N]Mo(cyclo-
propyl),28 we might expect MotCH also to be a stable
species. But in view of the difficulties associated with
preparing alkyls in reactions between [HIPTN3N]MoCl
and alkylating agents (see later), it seems doubtful that
we would be able to prepare Mo(cyclopropyl) and
ultimately MotCH in this manner.
Addition of [2,6-LutH]BAr′4 to samples of MotCH
and MotCMe in C6D6 led to no reaction, even after
heating the samples at 120 °C for 2 days. When Mot
CR was mixed with both [2,6-LutH]BAr′4 and Cp*2Cr
(40) Tsai, Y. C.; Diaconescu, P. L.; Cummins, C. C. Organometallics
2000, 19, 5260.
(41) Fuerstner, A.; Mathes, C.; Lehmann, C. W. J. Am. Chem. Soc.
1999, 121, 9453.
(42) Zhang, W.; Kraft, S.; Moore, J. S. Chem. Commun. 2003, 832.
(43) McCullough, L. G.; Schrock, R. R.; Dewan, J. C.; Murdzek, J.
S. J. Am. Chem. Soc. 1985, 107, 5987.
In the last several years, a new approach to alkylidyne
triamido complexes has been discovered. Cummins
devised a synthesis of alkylidyne complexes of the type
(44) Schrock, R. R. Acc. Chem. Res. 1986, 19, 342.
(45) Peters, J. C.; Odom, A. L.; Cummins, C. C. Chem. Commun.
1997, 1995.
(39) Schrock, R. R. In Reactions of Coordinated Ligands; Braterman,
P. R., Ed.; Plenum: New York, 1986.
(46) Greco, J. B.; Peters, J. C.; Baker, T. A.; Davis, W. M.; Cummins,
C. C.; Wu, G. J. Am. Chem. Soc. 2001, 123, 5003.

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4443
in C6D6, no reaction involving MotCR again was
observed; only H2 was generated.
cies, a circumstance that is likely to inhibit nucleophilic
attack at the metal center and favor electron transfer.
In view of the stability of MotCCH3, and the many
rearrangements reported for W triamidoamine alkyl
complexes,32 we were curious as to whether Mo(η2-
CHCH2) would rearrange to MotCCH3 upon heating.
However, we saw no evidence for such a rearrangement
in C6D6 at 80 °C after 2 h; only decomposition was
observed. On the other hand, in the process of exploring
the potential protonation of Mo(η2-CHCH2) by [2,6-
LutH]BAr′4 to yield [Mo(η2-CH2CH2)]+, a known com-
pound (see below), we noticed that Mo(η2-CHCH2)
rearranged to MotCCH3. Kinetic studies were carried
out in C6D6 with Ph3CH as the internal standard;
disappearance of the triplet resonance at 13.03 ppm
corresponding to the η2-CHCH2 proton of the vinyl group
was monitored. The isomerization is first order in Mo
in the presence of [2,6-LutH]BAr′4 (2.57 mM) with
kobs ) 1.10(5) × 10-5 s-1. Upon doubling the concentra-
tion of [2,6-LutH]BAr′4, kobs ) 2.00(4) × 10-5 s-1, which
suggests that the reaction is first order in [2,6-LutH]-
BAr′4. If we assume that d[Mo(η2-CHCH2)]/dt ) -k[Mo-
(η2-CHCH2)][LutHBAr′4], then the calculated second-
order rate constants are 4.27(20) × 10-3 and 3.89(8) ×
10-3 M-1 s-1 for these two runs. We propose that a
proton is delivered to the CH2 carbon atom in Mo(η2-
CHCH2) by [2,6-LutH]BAr′4 to form intermediate
[ModCHCH3]+, from which 2,6-lutidine then removes
the R proton to yield MotCCH3 (eq 9).
and MoCl
The reaction between 1.2 equiv of AlMe3
(∼0.1 M) in C6D6 led to the disappearance of MoCl and
formation of MoMe after 40 h at 22 °C. MoMe was
prepared and isolated in 28% yield by stirring a mixture
of MoCl with 2-3 equiv of AlMe3 in benzene for 2 days.
(Like all compounds in this general category, MoMe is
highly soluble in saturated hydrocarbons and therefore
cannot be isolated in high yield on relatively small
1
scales.) The H NMR spectrum of MoMe exhibits two
ligand backbone CH2 resonances at -14.8 and -66.3
ppm in C6D6. For comparison, the proton NMR spec-
trum of [TMSN3N]MoMe in C6D6 contains resonances
for the backbone methylene protons at -25.00 and
-83.24 ppm.28 These should be compared with backbone
resonances at -25.89 and -75.90 ppm in Mo(ethyl) and
-10 and -68 ppm in Mo(hexyl) and Mo(octyl).
Attempts to prepare MoEt in a reaction between
AlEt3 and MoCl under conditions similar to those used
to prepare MoMe led to formation of MoEt in a yield of
∼25% mixed with Mo(C2H4) and other unidentified
species. Heating a mixture of MoEt and AlEt3 under
the same conditions led to consumption of MoEt, so it
is possible that MoEt is in fact the primary product,
but it reacts further with AlEt3 to give Mo(C2H4). In
any case, the reaction between MoH and ethylene is
clearly a superior method of preparing MoEt.
We felt that we might be able to prepare Mo-CtCR
derivatives since [TMSN3N]Mo-CtCR species can be
prepared readily if R is not a proton.48 Attempts to make
[TMSN3N]Mo-CtCH led to the formation of the “tail-
to-tail” acetylide coupling product, [TMSN3N]MotC-
CHdCH-CtMo[TMSN3N].48 Therefore steric hindrance
might prevent a similar coupling between Mo-CtCH
species. Examples of acetylide coupling in related tria-
mido species have been reported.49
Heating a mixture of [Mo(NH3)]BAr′4 and NaCtCH
in fluorobenzene to 90 °C for 3 h led to formation of a
yellow crystalline compound in 57% isolated yield. The
proton NMR spectrum of this compound suggests that
it is diamagnetic and that it has no symmetry. Therefore
is unlikely to be Mo-CtCH, which should be paramag-
netic, or MotC-CHdCH-CtMo[HIPTN3N], which is
expected to be diamagnetic and to have C3 symmetry
on the NMR time scale. Reactions between MoCl and
NaCtCH in C6D5Cl at 80 °C for several hours did not
lead to the yellow product, only to apparent decomposi-
tion.
A difficult X-ray structural determination of the
yellow product showed that the acetylide has “inserted”
into an ortho C-H bond in the phenyl ring attached to
the amido nitrogen (eq 10; Figure 3 and Tables 1 and
2). The C-C bond distance is 1.429(15) Å, while the
Mo-C distances are 1.924(11) and 2.232(12) Å. There-
fore this compound can be placed in the category of an
η2-vinyl complex, similar to Mo(η2-CHCH2) described
above. The “alkylidene” proton resonance was found at
13.50 ppm, while the other proton resonance in the η2-
vinyl moiety could be observed at 4.69 ppm; these two
Attempts to Prepare [HIPTN3N]MoX Complexes
(X ) alkyl, cyanide, acetylide). Alkylation of MoCl
with LiMe under a variety of conditions gave a mixture
of unreacted MoCl, Mo(N2) (the major product), and
other unidentified products, either at room temperature
or at -35 °C. Treatment of a mixture of H3[HIPTN3N]
and MoCl4(THF)2 with LiMe at -35 °C in THF, a type
of reaction that led to [ArN3N]MoMe (where Ar is a
simple aryl group),47 affords the same mixture of
products as reactions between MoCl and LiMe. Appar-
ently the major reaction is reduction of MoCl by LiMe
to “[MoCl]-”, which then loses chloride and binds dini-
trogen to yield Mo(N2). A reaction between [Mo(NH3)]-
BAr′4 and LiMe in THF again led to primarily Mo(N2),
again by reduction of Mo(IV) to Mo(III). An important
difference between MoCl and [TMSN3N]MoCl, for ex-
ample, where [TMSN3N]MoR complexes are prepared
readily (R ) Me, Et, Bu, CH2Ph, CH2SiMe3, etc.28), is a
greater degree of steric crowding in [HIPTN3N]M spe-
(48) Shih, K.-Y.; Schrock, R. R.; Kempe, R. J. Am. Chem. Soc. 1994,
116, 8804.
(49) Blackwell, J. M.; Figueroa, J. S.; Stephens, F. H.; Cummins,
C. C. Organometallics 2003, 22, 3351.
(47) Greco, G. E.; Schrock, R. R. Inorg. Chem. 2001, 40, 3850.

4444 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
protons are coupled with JHH ) 2.4 Hz. In the 13C NMR
spectrum, the two η2-vinyl carbon resonances were
found at 287.6 and 65.4 ppm with C-H coupling
constants of 189.3 and 162.9 Hz, respectively. The
product of the reaction between [Mo(NH3)]BAr′4 and
NaCtCD in fluorobenzene does not have the “alkyli-
dene” HR resonance at 13.50 ppm. Therefore it appears,
at least in the absence of a double labeling experiment,
that the “alkylidene proton” comes from the acetylide
and the benzylic proton from the phenyl ring as a
consequence of “insertion” of the acetylide into the ortho
C-H bond of the phenyl ring bound to the amido
nitrogen. At this stage we assume that Mo-CtCH
forms, but is unstable. The mechanism of conversion of
Mo-CtCH into observed products is not known. At face
value one could be tempted to ascribe some carbenoid
character to the R carbon atom in the intermediate
acetylide complex.
Figure 3. Molecular structure of “[HIPTN3N]Mo(CCH)”.
The Mo atom, all atoms directly bonded to it, and C(320)
are drawn in their 50% thermal ellipsoid representations,
with the other atoms as circles of arbitrary radius. Hydro-
gen atoms and solvent molecules have been omitted for
clarity.
Table 3. Cyclic Voltammetric and Differential
Pulse Voltammetric Data Obtained for Various
Compounds Based on [HIPTN3N]Mo and
Referenced to the Cp2Fe+/0 Couplea
redox couple
E1/2 (V vs Cp2Fe)
ref
[HIPTN3N]Mo(N2)0/-
[HIPTN3N]Mo(NH3)+/0
[HIPTN3N]Mo(N2)+/0
[HIPTN3N]Mo(CN)+/0
[HIPTN3N]Mo(CN)0/-
[HIPTN3N]Mo(C2H4)+/0
[HIPTN3N]Mo(C2H2)+/0
[HIPTN3N]Mo(η2-CHCH2)+/0
Cp2Co+/0
-2.01
-1.63
-0.66
-0.27
-1.61
-0.42
-0.94
6
6
6
Orange paramagnetic MoCN can be isolated in good
2
yield from the reaction between [Mo(NH3)]BPh4 and
this work
this work
this work
this work
this work
6
[Bu4N]CN in fluorobenzene. During the course of the
reaction, colorless crystals of [Bu4N]BPh4 were depos-
ited. No absorption in the IR spectrum of MoCN that
could be attributed to the νCN stretch is observed, a
situation that is analogous to that reported for crystal-
lographically characterized [TMSN3N]MoCN.31 At-
tempts to prepare MoCN via the reaction between MoCl
with Me3SiCN failed; the reaction was slow even at
temperatures above 100 °C, and when neat Me3SiCN
was employed at these temperatures, an unidentified
yellow solid precipitated from solution. The reaction
between MoCl with Me3SiCN was not studied further.
Addition of B(C6F5)3 to MoCN in C6D6 resulted in the
formation of a green solution that we propose contains
a B(C6F5)3 adduct of MoCN, namely, MoCNfB(C6F5)3.
This assignment is based upon a strong absorption in
the IR spectrum at 2184 cm-1 that we assign to the νCN
+0.54 (Epa
)
-1.33
Cp*2Cr+/0
-1.63
6
6
Cp*2Co+/0
-2.01
a Cyclic voltammetry at 1.6 mm Pt working electrode or 3.0 mm
glassy carbon working electrode at 22 °C in 0.1 M [Bu4N]BAr′4 in
PhF at scan rates of 10-200 mV/s.
we have employed these conditions in relatively routine
electrochemical (CV) studies.
No reductions were observed for Mo(C2H4), Mo(C2H2),
or Mo(η2-CHCH2) in the region -1.5 to -2.7 V (vs
Cp2Fe+/0). However, Mo(C2H4)+/0 and Mo(C2H2))+/0 re-
dox couples can be observed at -0.42 and -0.94 V,
respectively, which are reversible on the CV time scale
(50 mV s-1), while Mo(CN) exhibits two redox processes
at -0.27 and -1.61 V that we assign to the Mo(CN)+/0
and Mo(CN)0/- redox couples, respectively. The Mo(CN)
couples should be compared with those at -0.66 V for
1
stretch, as well as 19F and H NMR spectroscopic data
that are consistent with this proposal. Apparently the
substantial change in dipole moment makes the CN
stretch in MoCNfB(C6F5)3 readily observable. Unfor-
tunately, all attempts to obtain crystals of MoCNf
B(C6F5)3 from heptane led only to re-formation of MoCN
and B(C6F5)3.
Electrochemical Studies and Syntheses of Cat-
ionic Species. Electrochemical studies50 on several of
the compounds reported here were carried out in 0.1 M
[Bu4N]BAr′4 (where Bu is n-butyl) in PhF at room
temperature (Table 3). The advantages of relatively
inert electrolytes and solvents were demonstrated more
than a decade ago51 and have been featured in several
studies by Geiger in the last few years.52-56 Therefore
Mo(N2)+/0 and at -2.01 V for Mo(N2)0/- 6
that is,
;
Mo(CN) is harder to oxidize but easier to reduce than
Mo(N2), which can be rationalized on the basis of the
metal’s oxidation state in each circumstance (formally
Mo(IV) in Mo(CN) vs Mo(III) in Mo(N2)). The Mo(CN)0/-
couple (-1.61 V) is found at almost the same potential
as that for Mo(NH3)+/0 (-1.63 V).6
(52) LeSuer, R. J.; Geiger, W. E. Angew. Chem., Int. Ed. 2000, 39,
248.
(53) Ohrenberg, C.; Geiger, W. E. Inorg. Chem. 2000, 39, 2948.
(54) Camire, N.; Mueller-Westerhoff, U. T.; Geiger, W. E. J. Orga-
nomet. Chem. 2001, 637-639, 823.
(55) Camire, N.; Nafady, A.; Geiger, W. E. J. Am. Chem. Soc. 2002,
124, 7260.
(50) Connelly, N. G.; Geiger, W. E. Chem. Rev. 1996, 96, 877.
(51) Hill, M. G.; Lamanna, W. M.; Mann, K. R. Inorg. Chem. 1991,
30, 4687.
(56) Trupia, S.; Nafady, A.; Geiger, W. E. Inorg. Chem. 2003, 42,
5480.

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4445
Upon addition of a slight excess of [Cp2Fe]BAr′4 to a
solution of Mo(η2-C2H2) in C6D6, ferrocene was formed
along with the diamagnetic [Mo(η2-C2H2)]BAr′4 (eq 11).
Figure 4. Molecular structure of {[HIPTN3N]Mo(C2H4)}-
BAr′4. The Mo atom and all atoms directly bonded to it are
drawn in their 50% thermal ellipsoid representations, with
the other atoms as circles of arbitrary radius. Hydrogen
atoms, solvent molecules, and the anion have been omitted
for clarity.
The relatively sharp 1H NMR resonances associated
with the acetylene in [Mo(η2-C2H2)]BAr′4 are found at
11.34 ppm. The proton resonances in [Mo(η2-13C2H2)]-
BAr′4 appear as a complex second-order splitting pattern
centered around 11.3 ppm, whereas in the 13C{1H} NMR
spectrum the resonance assigned to the acetylene
carbon atoms appears as a singlet at 214.6 ppm. In the
proton-coupled 13C NMR spectrum a second-order pat-
tern again was found that was similar to the pattern
C6D6) and the ethylene carbon resonance appears at
62.6 ppm.34
We do not know why the ethylene proton resonance
in Mo(C2H4)+ is broad. One possibility is electron
transfer between Mo(C2H4)+ and a trace of residual
Mo(C2H4) (either a self-exchange or one that includes
Cp2Fe0/+). Another possibility is that the ground state
of {[HIPTN3N]Mo(C2H4)}+ is a singlet, but a triplet is
thermally accessible. Studies aimed at resolving this
issue are ongoing.
1
found in the H NMR spectrum.
Addition of [Cp2Fe]BAr′4 to a C6D6 solution of Mo(η2-
C2H4) led to formation of ferrocene and [Mo(C2H4)]BAr′4
(eq 12). Both 1H and 13C{1H} NMR spectra for [Mo(C2-
An X-ray structure of [Mo(C2H4)]BAr′4 was completed
(Figure 4, Tables 1 and 2), although it was complicated
by a (resolved) disorder involving the BAr′4- anion. (See
Experimental Section.) The Mo-C(1) and Mo-C(2) bond
distances in [Mo(C2H4)]BAr′4 are essentially the same
as they are in Mo(C2H4). The C(1)-C(2) distance is
shorter than what it is in Mo(C2H4), consistent with a
lesser degree of back-bonding to ethylene, although even
that difference is only marginal.
H4)]BAr′4 and [Mo(13C2H4)]BAr′4 (prepared in situ)
suggest that the cation is diamagnetic. However, the
ethylene proton resonance, which appears at 5.14 ppm
(a doublet in the 13C-labeled complex), and the ethylene
carbon atom resonance, which appears at 84.3 ppm, are
Conclusions
Organometallic complexes that contain the [HIP-
TN3N]3- ligand appear to be much more robust than
those that contain trimethylsilyl- or pentafluorophenyl-
based ligands. However, the crowded nature of [HIP-
TN3N]3- ligands slows reactions at the metal center in
many cases. The [HIPTN3N]3- systems are not com-
pletely robust, as evidenced by the complication ob-
served in the attempt to prepare an acetylide derivative.
Nevertheless, [HIPTN3N]3- ligands would appear to be
more robust in general than other triamidoamine
ligands employed to date. Studies concerning the use
of several of the species reported here as catalyst
precursors for the reduction of dinitrogen to ammonia
will be reported in due course elsewhere.
1
both quite broad. When the H NMR sample is cooled,
the 5.14 ppm resonance shifts upfield, and when the
sample is heated, the ethylene resonance shifts down-
field. There is no exchange of the coordinated ethylene
with free ethylene in [Mo(C2H4)]+ on the NMR time
scale.
For comparison, it should be noted that oxidation of
compounds of the type [RN3N]M(C2H4) (where R )
SiMe3, M ) Mo; R ) C6F5, M ) W) have been reported
in the literature. Oxidation of [TMSN3N]Mo(C2H4) with
[Cp2Fe]OTf in CH2Cl2 yields [TMSN3N]Mo(OTf) (in 6 h
at 22 °C),28 whereas oxidation of [C6F5N3N]W(C2H4)
yields {[C6F5N3N]W(C2H4)}OTf.31 Presumably, ethylene
in {[TMSN3N]Mo(C2H4)}OTf is readily replaced by
triflate, whereas ethylene in {[C6F5N3N]W(C2H4)}OTf
is not, even in the presence of the more electron-
withdrawing [C6F5N3N]3- ligand. In {[C6F5N3N]W-
(C2H4)}[OTf] (in CDCl3)31 the ethylene protons appear
as a singlet at 3.10 ppm. In [TMSN3N]Ta(C2H4) the
ethylene proton resonance appears at 2.15 ppm (in
Experimental Section
General Procedures. All experiments were conducted
under nitrogen in a Vacuum Atmospheres drybox or using
standard Schlenk techniques. Glassware was dried at ∼190
°C overnight. Pentane was washed with HNO3/H2SO4 (5/95
v/v), sodium bicarbonate, and water, dried with CaCl2, and
then sparged with nitrogen and passed through alumina

4446 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
columns. Dry and deoxygenated benzene was purchased from
Aldrich and passed through Q5 and alumina columns. Dry and
deoxygenated THF was purchased from Aldrich and passed
through an alumina column. Toluene was sparged with
nitrogen, passed through alumina columns, and vacuum-
transferred from sodium benzophenone ketyl. Fluorobenzene
was dried by vigorous stirring over P2O5 and then vacuum
distilled followed by degassing by three freeze-pump-thaw
cycles. Benzene-d6 was degassed (freeze-pump-thaw) and
vacuum-transferred from sodium benzophenone ketyl. Tetra-
methylsilane was purchased from Lancaster and vacuum-
transferred from Na3K benzophenone.
and the solution was cooled to -40 °C. A fine crystalline
sample of [HIPTN3N]Mo(C2H4) was isolated (∼100 mg).
Method B. A 2.00 g sample of [HIPTN3N]MoCl was placed
in a 250 mL flask along with a glass stir bar, and 100 mL of
THF was added. Sodium amalgam (0.5%, ∼8 mL) was added,
and the solution was degassed with three freeze-pump-thaw
cycles. Ethylene (1 atm) was then introduced, and the reaction
mixture was stirred overnight. The color of the solution
changed slowly from orange to red. All solvents were then
removed in vacuo to afford a red residue that was dissolved
in pentane. The red solution was filtered through Celite and
concentrated in vacuo to yield a finely crystalline, rose-red
solid; yield 1.43 g (72%): 1H NMR δ 7.18 (s, aromatic CH),
2.88 (m, CH(CH3)2), 1.34 (br s, CH(CH3)2). Anal. Calcd for
MoCl, MoN2, [Mo(NH3)]BPh4, and MoH were prepared
according to published procedures,2,6 as were NaBAr′4 and
57
[Cp2Fe]BAr′4.58 Calcium carbide, 2,6-lutidine, anhydrous 1 M
HCl in diethyl ether, NaBPh4, Cp2Fe, ethylene, CO, 13C2H2 and
13C2H4, 1-hexene, and 1-octene were purchased from com-
mercial sources and used as received. Acetylene (BOC, Grade
2.6) was purified by slowly bubbling it through a fine frit in a
trap containing concentrated H2SO4 (after previously passing
nitrogen through the H2SO4 for several hours) and then a dry
ice/acetone trap to remove water and dissolved acetone. A large
Schlenk flask containing 3 Å molecular sieves was carefully
backfilled with acetylene (1 atm). This flask was then im-
mersed in a liquid-N2/Et2O slush bath and a vacuum applied
in an attempt to remove any oxygen impurities. Acetone was
dried over 4 Å molecular sieves and vacuum transferred onto
4 Å molecular sieves. This was repeated three times.
Dry and oxygen-free acetylene was prepared by adding
water to CaC2. Typically powdered CaC2 (∼1.3 g) was added
via an addition tube to a three-necked 1 L flask containing
benzene (10 mL) in ∼0.6 mL of water that had been degassed
via several freeze-pump-thaw cycles and still under vacuum.
After all visible signs of gas evolution had ceased (several
hours), the flask was then placed in a dry ice/acetone cooling
bath for ∼10 min and the contents of the headspace trans-
ferred to a 500 mL Schlenk flask fitted with a Kontes Teflon
plug (containing some anhydrous CaCl2) immersed in liquid
N2. The receiving flask was then sealed and allowed to warm
to room temperature, during which time the solid acetylene
vaporized. The pressure of acetylene was kept slightly below
1 atm.
C116H163MoN4: C, 81.50; H, 9.61; N, 3.28. Found: 81.39; H,
9.50; N, 3.18.
Preparation of [HIPTN3N]Mo(C2H2). A sample of [HIP-
TN3N]Mo(N2) (300 mg) was placed in a 50 mL Schlenk flask
along with 5 mL of benzene. The flask was then degassed three
times (freeze-pump-thaw cycles) before adding dry and
oxygen-free acetylene (5-10 equiv). Over a period of 1 h at
room temperature the color of the solution changed to olive
green and a purple-black precipitate formed. All volatiles were
removed in vacuo, and the residue was dissolved in heptane.
The solution was filtered through Celite in order to remove
the purple solid. The emerald green solution was then con-
centrated to ∼1 mL and placed in the -40 °C freezer overnight.
An emerald green crystalline solid was isolated, washed with
heptane, and dried in vacuo; yield 234 mg (78%): 1H NMR
(C6D6, 20 °C) δ 7.22 (s), 5.75 (v br s), 2.91 (br m), 1.33 (br s),
1.25 (br s). No other resonances were observed. Anal. Calcd
for C116H161MoN4: C, 81.60; H, 9.50; N, 3.28. Found: C, 81.43;
H, 9.36; N, 3.11.
[HIPTN3N]Mo(13C2H2). In a J-Young NMR tube ∼50 mg
of [HIPTN3N]MoN2 was dissolved in C6D6 (0.5 mL). This
solution was then degassed by three freeze-pump-thaw cycles
and several equivalents of 13C2H2 were then added. The
solution was then allowed to thaw with the solution turning
emerald green. Some purple solid precipitated from the
solution after 10 min. The 1H NMR spectrum was then
recorded and indicated that most of the dinitrogen complex
had been consumed. The solution was then filtered through
Celite to remove the solid and then stripped to dryness. The
green residue was then redissolved in the minimum amount
of heptane from which crystals grew via slow evaporation of
the solvent. Anal. Calcd for C11413C2H161MoN4: C, 81.62; H,
9.50; N, 3.28. Found: C, 81.47; H, 9.28; N, 3.18.
Routine 1H NMR spectra were recorded on either a Varian
Unity or a Mercury 300 MHz spectrometer at room temper-
ature. Data are listed in parts per million downfield from
tetramethylsilane and referenced either to internal tetra-
methylsilane or to the resonance for C6D5H at 7.16 ppm. 13C
NMR spectra were recorded at 75.5 MHz and referenced to
the residual solvent peak. Infrared spectra were recorded on
a Nicolet Avatar 360 FT-IR spectrometer either as a Nujol mull
(KBr plates) or in a demountable solution cell (0.2 mm Teflon
spacer, KBr plates). Electrochemical measurements were
carried out with a BAS CV-50W potentiostat. Platinum disk
(1.6 mm dia) or a glass carbon disk (3 mm dia), a platinum
wire, and a silver wire submerged in a solution of 0.1 M [Bu4N]-
BAr′4 in PhF were used as working, auxiliary, and reference
electrodes, respectively. All measurements were done in 0.1
M [Bu4N]BAr′4 in PhF and referenced externally and/or
internally to Cp2Fe or Cp2Co.
[HIPTN3N]Mo(CO). [HIPTN3N]Mo(N2) (200 mg) was dis-
solved in benzene (5 mL), and the solution was degassed twice
(freeze-pump-thaw) before CO (1 atm) was introduced. The
solution was then heated to 60 °C overnight, during which time
the color changed to red. All solvents were removed in vacuo
to leave a red residue. Pentane (1-2 mL) was added, and the
reddish-brown product was isolated and dried in vacuo for
several hours: 1H NMR δ 20.15 (br s, 6H, NCH2), 6.95 (s, 12H,
3,5,3′′,5′′-H), 2.86 (sept, JHH ) 6.3 Hz, 6H, 4′,4′′-CH(CH3)2),
1.84 (br s, 36 H, 2,6,2′′,6′′-CH(CH3)2), 1.44 (br s, 12H, 4′,4′′-
CH(CH3)2), 1.26 (d, JHH ) 6.6 Hz, 36H, 4′,4′′-CH(CH3)2), 1.02
(br s, 36H, 2,6,2′′,6′′-CH(CH3)2), -1.85 (s, 3H, 4-H), -8.21 (br
s, 6H, 4′,6′-H), -30.50 (br s, 6H, NCH2); IR (Nujol) cm-1 1892
(νCO), (C6D6) 1888 (νCO). Anal. Calcd for C115H159MoN4O: C,
80.80; H, 9.37; N, 3.28. Found: C, 80.71; H, 9.34; N, 3.14.
[HIPTN3N]Mo(13CO) was prepared similarly. IR (C6D6)
[HIPTN3N]Mo(C2H4). Method A. A 250 mg sample of
[HIPTN3N]Mo(N2) was dissolved in benzene (10 mL) in a
Schlenk flask. The flask was then evacuated and filled with
ethylene (1 atm), and the solution was heated to 60 °C for 21
h. All solvents were removed from the reddish solution to
afford a red solid. Pentane (5 mL) was added to the residue,
cm-1 1845 (ν13CO), 1802(ν13C18O). Anal. Calcd for C11413CH159
-
MoN4O: C, 80.76; H, 9.42; N, 3.27. Found: C, 80.64; H, 9.26;
N, 3.12.
(57) Reger, D. L.; Little, C. A.; Lamba, J. J. S.; Brown, K. J.;
Krumper, J. R.; Bergman, R. G.; Irwin, M.; Fracker, J. P., Jr. Inorg.
Synth. 2004, 34, 5.
(58) Chavez, I.; Alvarez-Carena, A.; Molins, E.; Roig, A.; Maniuk-
iewicz, W.; Arancibia, A.; Arancibia, V.; Brand, H.; Manuel Manriquez,
J. J. Organomet. Chem. 2000, 601, 126.
Preparation of [HIPTN3N]Mo(CO)Na. A solution of 210
mg of [HIPTN3N]Mo(CO) in THF (5 mL) containing ∼5 g of
0.5% Na/Hg was stirred in a vial containing a glass-coated
stirrer bar. After 1 h the solution was filtered through Celite
and all volatiles were removed in vacuo. The orange solid was

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4447
then dissolved in heptane (4-5 mL), and the solution was
filtered through Celite. Removal of all solvents yielded 185 mg
of the orange product (87% yield): 1H NMR (C6D6) δ 7.70 (br
to afford 89 mg (28%) of the microcrystalline product: 1H NMR
(C6D6, 20 °C) δ 12.0 (br s, 6H, 4′,6′-H), 7.24 (br s, 12H, 3,5,3′′,5′′-
H), 3.13 (br s, 12H, 2,6,2′′,6”-CHMe2), 2.99 (br m, 6H, 4,4′′-
CHMe2), 1.37 (d, JHH ) 6.3 Hz, 72H, CH(CH3)2), 1.33 (br s,
36H, CH(CH3)2), -14.8 (br s, 6H, NCH2), -66.3 (br s, 6H,
NCH2). Anal. Calcd for C115H162MoN4: C, 81.42; H, 9.62; N,
3.30. Found: C, 81.26; H, 9.68; N, 3.18.
s, 6H, 2′,6′-H), 7.19 (s, 12H, 3′,5′,3′,5′′-H), 6.50 (t, 3H, JHH
)
1.5 Hz, 4-H), 3.78 (br t, 6H, NCH2), 3.39 (sept, JHH ) 7.0 Hz,
12H, CH(CH3)2), 2.86 (sept, JHH ) 7.0 Hz, 6H, CH(CH3)2), 2.04
(br s, 6H, NCH2), 1.31 (d, JHH ) 7.0 Hz, 36H, CH(CH3)2), 1.23
(d, JHH ) 7.0 Hz, 36H, CH(CH3)2), 1.13 (d, JHH ) 7.0 Hz, 36H,
CH(CH3)2); IR (C6D6) cm-1 1632 (νCO).
[HIPTN3N]Mo13CH213CH3. (HIPTN3N)MoH (155 mg) was
dissolved in C6H6 (10 mL) in a Schlenk flask. The headspace
was evacuated via three freeze-pump-thaw cycles, and 13C2H4
(ca, 360 Torr in 40 mL) was added. The solution color changed
immediately from brick-red to red upon thawing the sample.
All volatiles were removed after 1 h, and the red residue was
redissolved in heptane (1-2 mL). A red crystalline solid was
isolated (93 mg, 59% yield): 1H NMR (C6D6, 20 °C) δ 7.24 (br
s, 12H, 3′,5′,3′′,5′′-H), 3.12 (br s, 12H, 2,6,2′′,6′′-CH(CH3)2), 2.98
(br m, 6H, 4,4′′-CH(CH3)2), 1.39 (d, JHH ) 6.3 Hz, 36H, CH-
(CH3)2), 1.33 (br s, 80H, CH(CH3)2 and 2,2′′-H), -2.09 (br, 6H,
2′,6′-H?), -25.89 (br, 6H, NCH2), -75.90 (br, >6H, NCH2 and
13CH213CH3). Anal. Calcd for C11413C2H164MoN4: C, 81.47; H,
9.65; N, 3.27. Found: C, 81.65; H, 9.46; N, 3.17.
[HIPTN3N]Mo(13CO)Na. A solution of 103 mg of [(HIPTN3-
N)Mo(13CO)] in THF (20 mL) and 7 g of 0.5% Na/Hg was
stirred in a vial containing a glass-coated stirrer bar for several
hours. The solution was filtered through Celite, and then all
solvents were removed in vacuo. The yellow-orange residue
was then redissolved in heptane and refiltered through Celite
to afford a clear-yellowish solution. This solution was reduced
in volume in vacuo and left to stand to yield 60 mg of an orange
solid (58% yield): 1H NMR (C6D6) δ 7.68 (br s, 6H, 2′,6′-H),
7.14 (s, 12H, 3′,5′,3′′,5′′-H), 6.47 (t, 3H, JHH ) 1.5 Hz, 4-H),
3.76 (br t, 6H, NCH2), 3.36 (sept, JHH ) 7.0 Hz, 12H,
CH(CH3)2), 2.84 (sept, JHH ) 7.0 Hz, 6H, CH(CH3)2), 2.01 (br
s, 6H, NCH2), 1.28 (d, JHH ) 7.0 Hz, 36H, CH(CH3)2), 1.21 (d,
JHH ) 7.0 Hz, 36H, CH(CH3)2), 1.11 (d, JHH ) 7.0 Hz, 36H,
CH(CH3)2); 13C{1H} NMR (partial spectrum) δ 232.5 (s); IR
Unlabeled samples were prepared similarly.
[HIPTN3N]Mo(n-hexyl). A benzene solution of [HIPTN3N]-
MoH (180 mg, 107 µmol) containing 1-hexene (51 mg, 607
µmol) was stirred at room temperature for 24 h. All volatile
components were removed in vacuo, and the residue was
extracted with 5 mL of heptane. The extracts were combined
and filtered through Celite. The filtrates were concentrated
and cooled to -35 °C for several days. The resulting brown-
red crystals were collected by filtration, washed with cold
pentane, and dried in vacuo to afford 136 mg (72% yield) of
microcrystalline product: 1H NMR (C6D6, 20 °C) δ 10.0 (br s,
6H, 4′,6′-H), 7.32 (s, 12H, 3,5,3′′,5′′-H), 5.00 (br s, 6H, Mo-
CH2(CH2)3CH2CH3), 3.21 (br s, 12H, 2,6,2′′,6′′-CHMe2), 2.99
(br m, 6H, 4,4′′-CHMe2), 2.40 ((br s, 2H, Mo-CH2(CH2)3CH2-
CH3), 1.42 (d, JHH ) 5.7 Hz, 36H, CH(CH3)2), 1.33 (br s, 36H,
CH(CH3)2), 1.25 (br s, 36H, CH(CH3)2), -9.9 (br s, 6H, NCH2),
-52 (br s, 2H, Mo-CH2(CH2)4CH3), -68.4 (br s, 6H, NCH2).
Anal. Calcd for C120H172MoN4: C, 81.58; H, 9.81; N, 3.17.
Found: C, 81.34; H, 9.75; N, 3.12.
[HIPTN3N]Mo(n-octyl). A procedure analogous to that
used to synthesize [HIPTN3N]Mo(hexyl) was followed, starting
from [HIPTN3N]MoH (195 mg, 116 µmol) and 1-octene (42 mg,
375 µmol); yield 129 mg (62%) of microcrystalline brown-red
crystals: 1H NMR (C6D6, 20 °C) δ 9.90 (br s, 6H, 4′,6′-H), 7.32
(s, 12H, 3,5,3′′,5′′-H), 5.20 (br, s, 6H, Mo-CH2(CH2)6CH3), 3.21
(br s, 12H, 2,6,2′′,6′′-CHMe2), 3.03 (br m, 6H, 4,4′′-CHMe2),
2.40 (br s, 2H, Mo-CH2(CH2)6CH3), 1.42 (d, JHH ) 4.5 Hz, 36H,
CH(CH3)2), 1.34 (br s, 36H, CH(CH3)2), 1.25 (br s, 36H, CH-
(CH3)2), 0.78 (br s, 3H, Mo-CH2(CH2)6CH3), -10.2 (br s, 6H,
NCH2), -52.3 (br s, 2H, Mo-CH2(CH2)6CH3), -68.5 (br s, 6H,
NCH2). Anal. Calcd for C122H176MoN4: C, 81.65; H, 9.88; N,
3.12. Found: C, 81.48; H, 9.79; N, 3.04.
(C6D6) cm-1 1601 (ν CO). Anal. Calcd for C11413CH159MoN4-
13
ONa: C, 79.74; H, 9.25; N, 3.28. Found: C, 79.62; H, 9.30; N,
3.06.
Preparation of [HIPTN3N]Mo(CO)H. Method A. [HIP-
TN3N]Mo(CO)Na (150 mg) was dissolved in C6H6 (2 mL), and
[Et3NH][BAr′4] (100 mg) was added. The color changed im-
mediately from orange to yellow. The reaction mixture was
allowed to stir for 1 h and then filtered through Celite. All
solvents were removed in vacuo, and the solid was redissolved
in heptane; 90 mg of yellow crystals was isolated: 1H NMR δ
7.20 (s, 12H, 3′,5′,3′′,5′′-H), 7.18 (s, 6H, 2′,6′-H), 6.64 (s, 3H,
4-H), 3.64 (br t, 6H, NCH2), 3.11 (sept, JHH ) 6.6 Hz, 12H,
CH(CH3)2), 2.94 (sept, JHH ) 6.9 Hz, 6H, CH(CH3)2), 2.10 (br
s, 6H, NCH2), 1.38 (d, JCH ) 6.9 Hz, 36H, CH(CH3)2), 1.26 (d,
JCH ) 6.9 Hz, 36H, CH(CH3)2), 1.14 (d, JCH ) 6.9 Hz, 36H,
CH(CH3)2), -0.08 (d, JCH ) 24.3 Hz, 1H). Anal. Calcd for C,
80.75; H, 9.43; N, 3.28. Found: C, 80.66; H, 9.38; N, 3.18.
Method B. [HIPTN3N]Mo(13CO)H. In a J-Young NMR
tube 15 mg of [HIPTN3N]MoH was dissolved in C6D6 (0.5 mL).
The NMR tube was then degassed via three freeze-pump-
thaw cycles, and ∼1 atm of 13CO was added to the frozen
solution. Upon thawing the sample, the color of the solution
changed immediately from brick-red to bright yellow. The
reaction appears to be quantitative by 1H NMR spectroscopy:
1H NMR δ 7.20 (s, 12H, 3′,5′,3′′,5′′-H), 7.18 (s, 6H, 2′,6′-H),
6.64 (s, 3H; 4-H), 3.64 (br t, 6H, NCH2), 3.11 (sept, JHH ) 6.6
Hz, 12H, CH(CH3)2), 2.94 (sept, JHH ) 6.9 Hz, 6H, CH(CH3)2),
2.10 (br s, 6H, NCH2), 1.38 (d, JCH ) 6.9 Hz, 36H, CH(CH3)2),
1.26 (d, JCH ) 6.9 Hz, 36H, CH(CH3)2), 1.14 (d, JCH ) 6.9 Hz,
36H, CH(CH3)2), -0.08 (d, JCH ) 24.3 Hz, 1H); 13C{1H} NMR
(partial spectrum) δ 200.5 (JCH ) 24.4 Hz); IR (C6D6) cm-1 1810
Preparation of [HIPTN3N]Mo(η2-CHCH2). [HIPTN3N]-
MoH (85 mg) was dissolved in 2 mL of C6H6 in a 25 mL
Schlenk flask. The flask was then degassed several times
(freeze-pump-thaw). Dry and oxygen-free C2H2 (5-10 equiv)
was then added to the flask and the solution left to stir for 1
h at room temperature. During this time, the color of the
solution changed to yellow and a purple precipitate formed.
All volatiles were then removed in vacuo. The residue was
redissolved in heptane, and the mixture was filtered through
Celite to remove the purple solid. The solvents were removed
in vacuo to yield a total of 70 mg of product: 1H NMR (C6D6,
20 °C) δ 13.03 (t, JHH ) 3.4 Hz, 1H, CH-CH2), 7.19 (s, 12H,
3′,5′,3′′,5′′-H), 6.76 (d, JHH ) 1.4 Hz, 6H, 2′,6′-H), 6.56 (br t,
JHH ) 1.2 Hz, 3H, 4-H), 3.75 (br t, 6H, NCH2), 3.07 (sept,
JHH ) 6.9 Hz, 12H, CH(CH3)2), 2.90 (sept, JHH ) 6.9 Hz, 6H,
CH(CH3)2, CH-CH2 obscured), 2.25 (br s, 6H, NCH2), 1.34 (d,
JHH ) 6.9 Hz, 36H, CH(CH3)2), 1.26 (d, JHH ) 6.9 Hz, 36H,
CH(CH3)2), 1.15 (d, JHH ) 6.6 Hz, 36H, CH(CH3)2). Anal. Calcd
13
(ν CO).
In a J-Young NMR tube 23 mg of [HIPTN3N]Mo(13CO)Na
was dissolved in C6D6 (∼0.5 mL) and a slight excess of [Et3-
NH]BAr′4 was added. A slightly lighter yellow solution was
formed along with some colorless crystals. The 1H NMR
spectrum was essentially identical to that reported above.
[HIPTN3N]MoMe. A mixture of [HIPTN3N]MoCl (325 mg,
189 µmol), AlMe3 (210 µmL, 2 M in heptane, 420 mmol), and
benzene (5 mL) was sealed in an Schlenk bulb, and the solution
was stirred for 2 days. All volatile components were removed
in vacuo, and the residue was extracted with 10 mL of pentane.
The extracts were filtered through Celite, and the pentane was
removed in vacuo. Approximately 3 mL of SiMe4 was added
in order to dissolve the residue, and the solution was cooled
to -35 °C overnight. The brown-red crystals that formed were
collected by filtration and recrystallized twice from heptane

4448 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
for C116H162MoN4: C, 81.55; H, 9.56; N, 3.28. Found: C, 81.38;
H, 9.44; N, 3.14.
[HIPTN3N]Mot13C13CH3. 1H NMR δ 7.45 (d, JCH ) 1.2 Hz,
6H, 2.06 (br s, 6H, NCH2), 1.36 (d, JHH ) 7.2 Hz, 36H, CH-
(CH3)2), 1.23 (d, JHH ) 6.9 Hz, 36H, CH(CH3)2), 1.13 (d, JHH
6.9 Hz, 36H, CH(CH3)2).
Formation of [HIPTN3N]Mo(η2-CHCH2) from {[HIPTN3N]-
Mo(C2H2)}BAr′4 was also observed. {[HIPTN3N]Mo(C2H2)}-
BAr′4 (16 mg) was dissolved in ∼0.4 mL of C6D6 in a J-Young
NMR tube, and 6 µL of LiBEt3H (1M in THF) was added via
a microsyringe. The tube was sealed and shaken to ensure
complete mixing. The color changed rapidly from green to
yellow, and a white precipitate formed. The 1H NMR spectrum
of this solution indicated that [HIPTN3N]Mo(η2-CHCH2) had
formed quantitatively.
)
[HIPTN3N]MotCC5H11. A C6D5CD3 (0.5 mL) solution of
[HIPTN3N]Mo(hexyl) (∼40 mg) was sealed in a J-Young NMR
tube and heated to 165 °C for 4 h: 1H NMR (C6D5CD3, 20 °C)
δ 7.26 (s, 6H, 4′,6′-H), 7.18 (s, 12H, 3,5,3′′,5′′-H), 6.58 (s, 3H,
2′-H), 3.63 (br t, 6H, NCH2), 3.04 (sept, JHH ) 6.6 Hz, 12H,
2,6,2′′,6′′-CHMe2), 2.91 (sept, JHH ) 6.6 Hz, 6H, 4,4′′-CHMe2),
2.64 (br s, 2H, MotC(CH2)4CH3), 2.20 (br t, 6H, NCH2), 1.99
(br s, 2H, MotC(CH2)4CH3), 1.36 (d, JHH ) 6.9 Hz, 36H, 4,4′′-
CH(CH3)2), 1.25 (br s, 36H, 2,6,2′′,6′′-CH(CH3)2), 1.19 (br s,
36H, 2,6,2′′,6′′-CH(CH3)2); several hexyl proton peaks overlap
with isopropyl resonances; 13C NMR (C6D5CD3 20 °C, partial)
δ 305.5 (MotC), 59.1 (NCH2), 51.8 (NCH2), 46.8 (MotCCH2).
[HIPTN3N]MotCC7H15. A C6D5CD3 (0.5 mL) solution of
[HIPTN3N]Mo(octyl) (∼70 mg) was sealed in a J-Young NMR
tube and heated to 155 °C for 4 h: 1H NMR (C6D5CD3, 20 °C)
δ 7.24 (s, 6H, 4′,6′-H), 7.15 (s, 12H, 3,5,3′′,5′′-H), 6.58 (s, 3H,
2′-H), 3.63 (br t, 6H, NCH2), 3.04 (septet, JHH ) 6.5 Hz, 12H,
2,6,2′′,6′′-CHMe2), 2.92 (septet, JHH ) 6.5 Hz, 6H, 4,4′′-CHMe2),
2.54 (br t, 2H, MotC(CH2)4CH3), 2.21 (br t, 6H, NCH2), 1.96
(br m, 4H, MotC(CH2)4CH3), 1.35 (d, JHH ) 6.9 Hz, 36H, 4,4′′-
CH(CH3)2), 1.25 (br s, 36H, 2,6,2′′,6′′-CH(CH3)2), 1.19 (br s,
36H, 2,6,2′′,6′′-CH(CH3)2); several octyl proton peaks overlap
with isopropyl resonances; 13C NMR (C6D5CD3 20 °C, partial)
δ 305.3 (MotC), 59.3 (NCH2), 51.9 (NCH2), 47.1 (MotCCH2).
Decomposition of [HIPTN3N]Mo(hexyl) in the Pres-
ence of 1-Octene. A mixture of [HIPTN3N]Mo(hexyl) (75.0
mg, 42.5 µmol) and 1-octene (27.0 mg, 220.9 µmol) was sealed
in a J-Young NMR tube and heated to 155 °C for 4 h; 13C NMR
(C6D5CD3 20 °C, partial) δ 305.4 (MotC, weak and broad
peak), 59.3 (NCH2 of [HIPTN3N]MotCC7H15), 59.1 (NCH2 of
[HIPTN3N]MotCC5H11), 52.0 (NCH2 of [HIPTN3N]MotCC7H15),
51.9 (NCH2 of [HIPTN3N]MotCC5H11), 47.1 (MotCCH2 of
[HIPTN3N]MotCC7H15), 46.8 (MotCCH2 of [HIPTN3N]Mot
CC5H11).
Preparation of {[HIPTN3N]Mo(C2H4)}BAr′4. A sample
of [HIPTN3N]Mo(C2H4) (200 mg, 0.117 mmol) was dissolved
in 10 mL of C6H6, and 126 mg of [Cp2Fe]BAr′4 (0.120 mmol)
was added. This solution was stirred for 30 min, during which
time most of the solids had dissolved and the solution had
turned orange-brown. All of the volatiles were removed in
vacuo to afford a brown solid. The solid was then heated to
∼40 °C under high vacuum in order to remove Cp2Fe. Crystals
were grown from a heptane solution stored at -35 °C: 1H
NMR (C6D6, 20 °C) δ 8.37 (br s, 8H, C6H3-3,5-(CF3)2), 7.68 (br
s, 4H, C6H3-3,5-(CF3)2), 7.12 (s, 12H, 3′,5′,3′′,5′′-H), 6.70 (s, 3H;
4′-H), 6.45 (s, 6H, 4′,6′-H), 5.05 (br s, 4H, C2H4), 3.24 (br t,
6H, NCH2), 2.86 (sept, JHH ) 6.6 Hz, 6H; 4,4′′-CH(CH3)2), 2.64
(sept, JHH ) 7.2 Hz, 12H, 2,6,2′′,6′′-CH(CH3)2 plus the other
NCH2 resonance), 1.30 (d, JHH ) 6.6 Hz, 36H, CH(CH3)2), 1.11
(d, JHH ) 6.6 Hz, 36H, CH(CH3)2), 1.04 (d, JHH ) 6.9 Hz, 36H,
CH(CH3)2); 19F{1H} NMR (C6D6, 20 °C) δ -61.9 (s). Anal. Calcd
for C148H175BF24MoN4: C, 69.09; H, 6.86; N, 2.18. Found: C,
68.79; H, 6.80; N, 2.06.
Preparation of [HIPTN3N]Mo(η2-13CH13CH2). In a J-
Young NMR tube 15 mg of [HIPTN3N]MoH was dissolved in
C6D6 (0.5 mL). The NMR tube was then degassed via three
freeze-pump-thaw cycles, and then 3 equiv of 13C2H2 was
added to the frozen solution. Upon thawing the sample, the
color of the solution changed immediately from brick-red to
yellow and insoluble polyacetylene formed. The reaction ap-
1
pears to be quantitative by H NMR spectroscopy: 1H NMR
(C6D6, 20 °C) δ 13.02 (br d, JCH ) 191.9 Hz, 1H, 13CH-13CH2),
7.19 (s, 12H, 3′,5′,3′′,5′′-H), 6.76 (s, 6H, 2′,6′-H), 6.56 (s, 3H,
4-H), 3.75 (br t, 6H, NCH2), 3.07 (sept, JHH ) 6.6 Hz, 12H,
CH(CH3)2), 2.93 (d, JCH ) 160.1 Hz, 2H, 13CH-13CH2), 2.90
(sept, JHH ) 6.9 Hz, 6H, CH(CH3)2), 2.25 (br s, 6H, NCH2),
1.34 (d, JHH ) 6.9 Hz, 36H, CH(CH3)2), 1.26 (d, JHH ) 6.9 Hz,
36H, CH(CH3)2), 1.15 (d, JHH ) 6.9 Hz, 36H, CH(CH3)2); 13C-
{1H} NMR (C6D6, 20 °C) (partial) 272.18 (d, JCC ) 41 Hz,
Mo13CH13CH2) and 44.78 (d, JCC ) 41 Hz, Mo13CH13CH2).
[HIPTN3N]MotCH. A THF (25 mL) solution of [HIPTN3N]-
MoCl (1.176 g, 0.264 685 µmol) was treated with CH2Cl2 (150
mg, 1.76 mmol) and Mg (148 mg, 6.17 mmol) in a Schlenk
flask. The resulting mixture was freeze-pump-thaw degassed
five times, and the flask was heated to 90 °C for 16 h. Volatiles
were removed in vacuo, and the residue was extracted with
25 mL of pentane. The extracts were filtered through Celite,
and the filtrate was concentrated and cooled to -35 °C
overnight. The yellow microcrystals that formed were recrys-
tallized from pentane and were collected by filtration in three
crops, washed with cold pentane, and dried in vacuo to afford
760 mg of product (yield 65%): 1H NMR (C6D6, 20 °C) δ 7.73
(s, 6H, 4′,6′-H), 7.20 (s, 12H, 3,5,3′′,5′′-H), 6.55 (s, 3H, 2′-H),
4.47 (s, 1H, CH), 3.65 (br t, 6H, NCH2), 3.12 (sept, JHH ) 6.9
Hz, 12H, 2,6,2′′,6′′-CHMe2), 2.92 (sept, JHH ) 6.9 Hz, 6H, 4,4′′-
CHMe2), 1.92 (br t, 6H, NCH2), 1.36 (d, JHH ) 6.9 Hz, 36H,
4,4′′-CH(CH3)2), 1.23 (d, JHH ) 6.9 Hz, 36H, 2,6,2′′,6′′-CH-
(CH3)2), 1.11 (br d, JHH ) 6.9 Hz, 36H, 2,6,2′′,6′′-CH(CH3)2);
13C NMR (C6D6 20 °C) δ 288.4 (MotC), 162.1, 148.3, 147.3,
140.9, 138.7, 126.0, 120.9, 119.9 (phenyl-C), 57.1 (NCH2), 51.1
(NCH2), 35.3 (CHMe2), 31.2 (CHMe2), 25.1 (CH(CH3)2), 25.0
(CH(CH3)2). Anal. Calcd for C115H160N4Mo: C, 81.51; H, 9.52;
N, 3.31. Found: C, 81.59; H, 9.40; N, 3.26.
Preparation of [HIPTN3N]MotCCH3. A solution of
[HIPTN3N]MoH (510 mg, 303 µmol) in 15 mL of toluene in a
25 mL Schlenk flask was degassed several times (freeze-
pump-thaw). Dry and oxygen-free C2H4 (∼5 equiv) was then
added to the flask and the solution left to stir overnight at
room temperature. The excess ethylene was removed under
partial vacuum, and the resulting red solution was heated at
160-165 °C for 4 h. The solution color changed to yellow-
brown. All volatiles were then removed in vacuo, the residue
was extracted with 10 mL of pentane, and the mixture was
filtered through Celite. The resulting solution was concen-
trated in vacuo and cooled at -35 °C overnight to afford 320
mg (62% yield) of yellow microcrystalline product: 1H NMR
(C6D6, 20 °C) δ 7.45 (d, JCH ) 1.2 Hz, 6H, 2′,6′-H), 7.24 (br s,
12H, 3′,5′,3′′,5′′-H), 6.67 (br t, 3H, 4-H), 3.68 (br t, 6H, NCH2),
2.06 (br s, 6H, NCH2), 1.36 (d, JHH ) 7.2 Hz, 36H, CH(CH3)2),
1.23 (d, JHH ) 6.9 Hz, 36H, CH(CH3)2), 1.13 (d, JHH ) 6.9 Hz,
36H, CH(CH3)2); 13C NMR (C6D6 20 °C, partial) δ 299.3 (Mot
C), 57.7 (NCH2), 51.2 (NCH2). Anal. Calcd for C116H162N4Mo:
C, 81.55; H, 9.56; N, 3.28. Found: C, 81.32; H, 9.61; N, 3.22.
In Situ Preparation of [(HIPTN3N)Mo(13C2H4)]BAr′4.
[HIPTN3N]Mo(η2-13C2H4)] (50 mg, 0.029 mmol) was dissolved
in ∼0.6 mL of C6D6 in a J-Young NMR tube. [Cp2Fe]BAr′4 (32
mg, 0.120 mmol) was added and the tube shaken after sealing.
The NMR tube was then centrifuged to remove all of the solid
to the top of the tube: 1H NMR (C6D6, 20 °C) δ 8.37 (br s, 8H,
C6H3-3,5-(CF3)2), 7.70 (br s, 4H, C6H3-3,5-(CF3)2), 7.14 (s, 12H,
3′,5′,3′′,5′′-H), 6.69 (s, 3H, 4′-H), 6.44 (s, 6H, 4′,6′-H), 5.40 (br
s, 2H, 13C2H4), 4.91 (br s, 2H, 13C2H4), 3.21 (br t, 6H, NCH2),
2.88 (sept, JHH ) 6.6 Hz, 6H, 4,4′′-CH(CH3)2), 2.65 (sept,
JHH ) 7.2 Hz, 12H, 2,6,2′′,6′′-CH(CH3)2 plus the other NCH2
resonance), 1.31 (d, JHH ) 6.6 Hz, 36H, CH(CH3)2), 1.12 (br s,
36H, CH(CH3)2), 1.05 (br s, 36H, CH(CH3)2); 13C{1H} NMR
spectrum (C6D6, 20 °C, partial) δ 84.3 (br s).

Molybdenum Complexes with Triamidoamine Ligands
Organometallics, Vol. 24, No. 18, 2005 4449
{[HIPTN3N]Mo(C2H2)}BAr′4. [HIPTN3N]Mo(C2H2) (175
mg, 0.102 mmol) was dissolved in 10 mL of C6H6. To this
emerald green solution was added 108 mg of [Cp2Fe]BAr′4
(0.103 mmol), and the solution was stirred for 30 min, during
which the color changed to dark green. All volatiles were
removed in vacuo, and the green residue was redissolved in
the minimum amount of heptane. After several days, a green
crystalline solid was isolated and was then placed on a high-
vacuum line to remove Cp Fe; the yield was essentially
quantitative: 1H NMR (C6D6, 20 °C) δ 11.34 (s, 2H, C2H2), 8.39
(br s, 8H, C6H3-3,5-(CF3)2), 7.65 (br s, 4H, C6H3-3,5-(CF3)2), 7.13
(s, 12H, 3′,5′,3′′,5′′-H), 6.54 (t, JHH ) 1.4 Hz, 3H; 4′-H), 6.45
(d, JHH ) 1.1 Hz, 6H; 4′,6′-H), 3.82 (br t, 6H, NCH2), 2.87 (sept,
JHH ) 6.9 Hz, 6H; 4,4′′-CH(CH3)2), 2.60 (sept, JHH ) 6.9 Hz,
12H, 2,6,2′′,6′′-CH(CH3)2 + the other NCH2 resonance), 1.31
(d, JHH ) 6.6 Hz, 36H, CH(CH3)2), 1.12 (d, JHH ) 6.9 Hz, 36H,
CH(CH3)2), 1.03 (d, JHH ) 6.9 Hz, 36H, CH(CH3)2); 19F{1H}
NMR (C6D6, 20 °C) δ -61.95 (s). Anal. Calcd for C148H173BF24-
MoN4: C, 69.15; H, 6.78; N, 2.18. Found: C, 68.87; H, 6.69;
N, 2.10.
NCH2), 3.12 (br m, 18H, Ar-CHMe2), 2.36 (br m, 2H, NCH2),
2.12 (br m, 3H, NCH2), 1.96 (br m, 1H, NCH2), 1.46 (d, JHH
)
6.9 Hz, 36H, 4,4′′-CH(CH3)2), 1.32 (d, JHH ) 6.9 Hz, 36H,
2,6,2′′,6′′-CH(CH3)2), 1.24 (br d, JHH ) 5.7 Hz, 36H, 2,6,2′′,6′′-
CH(CH3)2); 13C NMR (C6D6, 20°C, partial) δ 288.4 (JCH ) 287.6
Hz, ModCH), 159.0, 157.6, 152.6, 147.7, 147.6, 147.4, 147.3,
147.2, 146.9, 141.5, 140.4, 139.3, 138.4, 138.1, 137.8, 137.7,
127.1, 125.7, 120.5, 120.3, 108.5, 65.4 (JCH ) 162.9 Hz, NCH2),
54.0 (NCH2), 53.5 (NCH2), 52.3 (NCH2), 51.9 (NCH2), 35.0
(CHMe2), 32.2 (CHMe2), 30.9 (CHMe2), 29.4 (CHMe2), 25.7,
24.8, 24,7, 24.6, 24.5, 23.1. Anal. Calcd for C116H160MoN4: C,
81.64; H, 9.45; N, 3.28. Found: C, 81.83; H, 9.52; N, 3.17.
Preparation of NaCtCD. Solid CaC2 (1.3 g, 20.3 mmol)
was added via an addition tube to a three-neck 1 L flask
containing a solution of benzene (10 mL) and D2O (0.6 mL,
33.3 mol) that had been previously degassed in several freeze-
pump-thaw cycles and still under vacuum. The mixture was
stirred for several hours, and the flask was then placed in a
dry ice/acetone cooling bath for about 20 min. The contents of
the headspace was transferred to a 500 mL Schlenk flask
containing some anhydrous CaCl2 immersed in liquid N2. The
receiving flask was then sealed and allowed to warm to room
temperature.
{[HIPTN3N]Mo(13C2H2)}BAr′4 was prepared similarly. The
proton resonance at 11.30 ppm was part of a complex second-
order pattern. The 13C{1H} resonance at 214.6 ppm was a
singlet that in the proton-coupled spectrum became a second-
order pattern.
After the acetylene was dried overnight over anhydrous
CaCl2, it was transferred into another 500 mL flask containing
sodium sand (0.35 g) and THF (20 mL). The flask was then
sealed and the reaction mixture was stirred overnight and
heated to 45-50 °C for 2 h. The white slurry was carefully
decanted out and filtered through a frit to afford 0.225 g of
white powder. No further purification was required. Na13Ct
13CH was prepared by the same procedure from H13Ct13CH
and sodium sand in THF.
Reaction of {[HIPTN3N]Mo(NH3)}BAr′4 with NaCtCD.
A procedure analogous to reaction of {[HIPTN3N]Mo(NH3)}-
BAr′4 with NaCtCH was followed, starting from {[HIPTN3N]-
Mo(NH3)}BAr′4 (210 mg, 82 µmol) and NaCtCD (40 mg, 816
µmol); yield 89 mg (64%) yellow crystals.
[HIPTN3N]MoCN. A sample of {[HIPTN3N]Mo(NH3)}BPh4
(600 mg) was dissolved in PhF (20 mL), and [Bu4N]CN (77
mg) was added. After 5 min stirring the solution had changed
color from red to orange and colorless crystals of [Bu4N]BPh4
had formed. The solution was stirred for a further 1 h, and
then all of the volatiles were removed in vacuo. The orange
residue was triturated with pentane (10 mL), and the orange
solid was filtered off. The orange solid was separated from the
colorless crystals by adding the minimum amount of C6H6 and
filtering the solution through Celite. The benzene was removed
in vacuo, and 1-2 mL of pentane was added to the residue.
Crystals of orange [HIPTN3N]MoCN were collected in three
crops; yield 352 mg (72%): 1H NMR (C6D6, 20 °C) δ 7.23 (br s,
12H, 3′,5′,3′′,5′′-H), 3.59 (br s, 12H, 2,6,2′′,6′′-CH(CH3)2), 2.98
(sept, JHH ) 6.3 Hz, 6H, 4,4′′-CH(CH3)2), 1.45 (br s, 72H,
2,6,2′′,6′′-CH(CH3)2), 1.38 (d, JHH ) 6.3 Hz, 36H, 4,4′′-CH-
(CH3)2), 1.25 (s, 6H, 4′,6′-H), -1.93 (s, 3H, 2’-H), -26.89 (br s,
Reaction of {[HIPTN3N]Mo(NH3)}BAr′4 with Na13Ct
13CH. A procedure analogous to the reaction of {[HIPTN3N]-
Mo(NH3)}BAr′4 with Na13Ct13CH was followed, starting from
{[HIPTN3N]Mo(NH3)}BAr′4 (212 mg, 82.8 µmol) and Na13Ct
13CH (48 mg, 960 µmol). The resulting pentane extract was
dried in vacuo and dissolved in C6D6. 1H NMR (C6D6, 20 °C) δ
13.82 (d, ModC-H), 13.19 (d, ModC-H), 4.97 (s, Mo-C-H), 4.423
6H, NCH2), -33.13 (br s, 6H, NCH2). Anal. Calcd for C115H159
-
MoN5: C, 80.89; H, 9.39; N, 4.10. Found: C, 81.06; H, 9.46;
N, 3.97.
(s, Mo-C-H); 13C NMR (C6D6, 20 °C, partial) δ 287.6 (d, JCC
38.1 Hz, ModCH), 65.4 (d, JCC ) 38.1 Hz, Mo-CH).
)
In Situ Observation of [HIPTN3N]MoCNrB(C6F5)3).
[(HIPTN3N)MoCN] (20 mg) in a J-Young NMR tube was
dissolved in ∼0.6 mL of C6D6, and B(C6F5)3 (∼6 mg) was added.
After 12 h the color of the solution had changed from orange
to green: 1H NMR (C6D6, 20 °C) δ 7.23 (br s, 12H, 3′,5′,3′′,5′′-
H), 6.65, 3.54 (br s, 12H, 2,6,2′′,6′′-CH(CH3)2), 2.98 (sept,
JHH ) 6.0 Hz, 6H, 4,4′′-CH(CH3)2), 1.70, 1.45 (br s, 72H,
2,6,2′′,6′′-CH(CH3)2), 1.38 (d, JHH ) 6.3 Hz, 36H, 4,4′′-CH-
(CH3)2), 1.25 (s, 3H, 2′-H), -1.93, -26.89, -33.13; 19F{1H}
NMR (C6D6, 20 °C) δ -12527 (br s, o-C6F5), -156.42 (s),
-158.90 (s); IR (C6D6) cm-1 (s) 2184 (νCN).
Reaction of {[HIPTN3N]Mo(NH3)}BAr′4 with NaCtCH.
A mixture of {[HIPTN3N]Mo(NH3)}BAr′4 (336 mg, 131.9 µmol),
NaCtCH (19 mg, 396 mmol), and fluorobenzene (5 mL) was
sealed in an Schlenk bulb and heated at 90 °C for 3 h while
stirring. Volatiles were removed in vacuo, and the residue was
extracted into 10 mL of pentane. The extract solution was
filtered through Celite, concentrated in vacuo, and cooled to
-35 °C overnight. The yellow powder was collected by filtration
and recrystallized from heptane to afford 128 mg of micro-
crystalline product; yield 58%: 1H NMR (C6D6, 20 °C, partial)
δ 13.59 (d, JHH ) 2.4 Hz, 1H, ModC-H), 7.19, (m, 14H, Ar-H),
6.96 (s, 2H, Ar-H), 6.82 (s, 1H, Ar-H), 6.55 (br s, 1H, Ar-H),
6.37 (s, 1H, Ar-H), 6.29 (d, 2H, Ar-H), 4.69 (d, JHH ) 2.4 Hz,
1H, Mo-C-H)), 4.15 (br m, 1H, NCH2), 3.97 (br m, 1H, NCH2),
3.68 (br d, 1H, NCH2), 3.49 (br m, 3H, NCH2), 3.24 (br m, 3H,
X-ray Structural Studies. Low-temperature diffraction
data were collected on a Siemens Platform three-circle dif-
fractometer coupled to a Bruker-AXS Smart Apex CCD detec-
tor with graphite-monochromated Mo KR radiation (λ )
0.71073 Å), performing æ- and ω-scans. All structures were
solved by direct methods using SHELXS59 and refined against
F2 on all data by full-matrix least squares with SHELXL-97.60
All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms bonded to carbon atoms (except on carbon
atoms that bind directly to metal atoms) were included into
the model at geometrically calculated positions and refined
using a riding model. Coordinates for the other hydrogen atoms
were taken from the difference Fourier synthesis and refined
freely with the help of distance restraints. The isotropic
displacement parameters of all hydrogen atoms were fixed to
1.2 times the U value of the atoms they are linked to (1.5 times
for methyl groups). Crystal and structural refinement data are
listed in Table 1 for all four structures.
Most of the isopropyl groups in all of the structures were
disordered, and whenever such a disorder could be modeled
successfully, it was refined with the help of similarity re-
(59) Sheldrick, G. M. Acta Crystallogr. Sect. A 1990, 46, 467.
(60) Sheldrick, G. M. SHELXL 97; Universita¨t Go¨ttingen: Go¨ttin-
gen, Germany, 1997.

4450 Organometallics, Vol. 24, No. 18, 2005
Byrnes et al.
straints on 1-2 and 1-3 distances and displacement param-
eters as well as rigid bond restraints for anisotropic displace-
ment parameters. The relative occupancies for the disordered
components were refined freely, while constraining the total
occupancy of both components to unity.
In the structure of {[HIPTN3N]Mo(C2H4)}{BAr′4}, the anion
is disordered over two positions. To counteract the correlation
between coordinates and anisotropic displacement parameters
of the disordered atoms, similarity restraints on 1-2 and 1-3
distances and displacement parameters as well as rigid bond
restraints for anisotropic displacement parameters were ap-
plied. The occupancies of the two components were not refined
freely but constrained to 0.5, as the crystallographic inversion
center is involved in the disorder. One relatively high residual
electron density maximum (2.1 electrons per Å3) is located 0.91
Å away from the Mo atom. No meaningful assignment could
be made for this peak, and we believe that absorption effects
and Fourier truncation errors are the cause for this spurious
electron density.
The crystals giving rise to the datasets for structures
[HIPTN3N]Mo(C2H4) and “[HIPTN3N]Mo(CCH)” only dif-
fracted to relatively low resolution, which led to a low data-
to-parameter ratio in the refinement of those structures. This
is a problem encountered relatively frequently with compounds
that contain the large and flexible [HIPTN3N]3- ligands, and
similarity restraints and rigid-bond restraints for anisotropic
displacement parameters were applied to all atoms in those
two structures to counteract the correlation effects arising from
the low number of data. All structures contain disordered
solvent molecules (toluene in [HIPTN3N]Mo(C2H4) and hexane
or heptane in the other three). In all structures, crystal-
lographic symmetry elements are involved in these disorders.
This leads to noninteger values for the number of the carbon
and/or hydrogen atoms in the empirical formulas of three of
those structures.
The structure of “[HIPTN3N]Mo(CCH)” may be twinned by
merohedry with the true space group being P3h instead of P3hc1
(twin law 0 1 0 1 0 0 0 0-1). Unfortunately, the twin
refinement was not stable. The main reason for this is probably
the insufficient quality and low resolution of the data. There-
fore this structure is reported as untwinned in the higher
symmetric space group. The crystal structure of this molecule
is suboptimal. Unfortunately all attempts to obtain better
crystals failed, and we believe that at least some meaningful
conclusions can be drawn from this structure, which justifies
including it in this publication.
Acknowledgment. We thank the National Science
Foundation (CHE-9988766) for supporting this research.
Supporting Information Available: Fully labeled ther-
mal ellipsoid drawing, atomic coordinates, bond lengths and
angles, anisotropic displacement parameters, and hydrogen
coordinates for [HIPTN3N]Mo(C2H4) (04044), [HIPTN3N]Mo-
(CH2CH3) (04200), “[HIPTN3N]Mo(CCH)” (05021), and {[HIP-
TN3N]Mo(C2H4)}BAr′4 (05034). This material is available free
of charge via the Internet at http://pubs.acs.org. Data for the
four structures are also available to the public at http://
www.reciprocalnet.org/. The number in parentheses above
identifies each structure at this site.
OM050373E