Formation and reactivity of the Os(IV)-azidoimido complex, PPN[OsIV(bpy)(Cl)3(N4)]

Article abstract of DOI:10.1021/ja0122086

Reactions between the Os(VI)-nitrido complexes, [Os^VI(L₂)(Cl)₃(N)] (L₂ = 2,2′-bipyridine (bpy) ([1]), 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy), 1,10-phenanthroline (phen), and 4,7-diphenyl-1,10-phenanth

Full text of DOI:10.1021/ja0122086

Published on Web 04/05/2002
Formation and Reactivity of the Os(IV)-Azidoimido Complex,
PPN[OsIV(bpy)(Cl)3(N4)]
My Hang V. Huynh,*,‡ R. Thomas Baker,§ Donald L. Jameson,| Andrea Labouriau,§ and
Thomas J. Meyer*,†
Contribution from The Associate Laboratory Director for Strategic Research, MS A127, and the Chemistry DiVision,
MS J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Received September 20, 2001
Table 1. Selected Infrared Data ((2 cm-1) for PPN-
In the chemistry of Os(VI)-nitrido complexes, a general
[OsIV(bpy)(Cl)3(N4)] and Its 15N-Labeled Analogues in Nujol Mulls
reactivity is emerging based on formal N- addition to a variety of
IV
[Os (bpy)(Cl)3(N )]- isotopic distribution
ν
asym(N -
)
ν(Os−N )
nucleophiles,1-5 examples being CN-,6 RSH,7 R2NH,8 PR3,9 and
SPR3,10 eqs 1-5.
4
3
R
[OsIV-14N14N14N14N]-
[OsIV-15N14N14N14N]-
[OsIV-14N15N14N14N]-
[OsIV-14N14N14N15N]-
[OsIV-15N15N14N14N]-
[OsIV-15N14N14N15N]-
[2]- a
2058
2056
1092
1074
[2*]- b
[OsVI(tpy)(Cl)2(N)]+ + CN- f [OsIV(tpy)(Cl)2(NCN)] (1)
[2A*]- c
[2B*]- c
[2A**]- d
[2B**]- d
2040
2041
1090
1073
[OsVI(tpy)(Cl)2(N)]+ + ArSH f
[OsIV(tpy)(Cl)2(NS(H)(Ar)]+ (2)
a Product from reaction between [OsVI(bpy)(Cl)3(14N)] and 14N14N14N-.
b Product from reaction between [OsVI(bpy)(Cl)3(15N)] and 14N14N14N-.
c Products from reaction between [OsVI(bpy)(Cl)3(14N)] and 15N14N14N-.
d Products from reaction between [OsVI(bpy)(Cl)3(15N)] and 15N14N14N-.
[OsVI(tpm)(Cl)2(N)]+ + R2NH f
[OsIV(tpm)(Cl)2(N(H)R2)]+ (3)
by gradient column chromatography on silica gel with CH3CN:
C6H5CH3 mixtures (from 1:1 to 5:1 (v/v) ratio) as the eluent,
followed by recrystallization from tetrahydrofuran. The product was
collected (32% yield) and fully characterized by cyclic voltammetry,
elemental analysis, 1H and 15N NMR, UV-vis, and infrared (Table
1) (IR) spectroscopies.12
[OsVI(tpy/tpm)(Cl)2(N)]+ + PR3 f
[OsIV(tpy/tpm)(Cl)2(NPR3)] (4)
[OsVI(tpy/tpm)(Cl)2(N)]+ + SPR3 f
1/2[OsIV(tpy/tpm)(Cl)2(NPR3)]+ +
1/2[OsII(tpy/tpm)(Cl)2(NS)]+ (5)
Direct evidence for the formation of an Os(IV)-azidoimido
product comes from 15N-labeling and IR measurements in Nujol
mulls and 15N NMR in CD3CN. As shown in Table 1, the
asymmetric stretching vibration of the azido group, νasym(N3-),
appears at 2057 ( 2 cm-1 in PPN[OsIV(bpy)(Cl)3(14N14N3)]
(PPN[2]) and PPN[OsIV(bpy)(Cl)3(15N14N3)] (PPN[2*])13 and at
2041 ( 2 cm-1 in mixtures of PPN[OsIV(bpy)(Cl)3(14N15N14N14N)]
(PPN[2A*]) and PPN[OsIV(bpy)(Cl)3(14N14N14N15N)] (PPN[2B*])
(tpy ) 2,2′:6′,2′′-terpyridine,
tpm ) tris(pyrazol-1-yl)methane)
We report here the novel observation that reaction between azide
ion and the relatively electron-rich nitrido complex, [OsVI(bpy)-
(Cl)3(N)] ([1]) (bpy ) 2,2′-bipyridine), results in the stable OsIV-
azidoimido product, [OsIV(bpy)(Cl)3(N4)]- ([2]-), which contains
or in mixtures of PPN[OsIV(bpy)(Cl)3(15N15N14N14N)] (PPN[2A**])
-
and PPN[OsIV(bpy)(Cl)3(15N14N14N15N)] (PPN[2B**]). νasym(N3
)
appears at 2019 cm-1 in PPN[14N14N14N] and at 2005 cm-1 in
PPN[15N14N14N]. From these data, it can be inferred that the N3
unit is retained in [2]-.
2-
the first example of an unbridged N4 ligand,11 eq 6.
In the same set of IR spectra, ν(Os-14N) appears at 1091 ( 2
cm-1 in PPN[2], PPN[2A*], and PPN[2B*], and ν(Os-15N) appears
at 1073 ( 2 cm-1 in PPN[2*], PPN[2A**], and PPN[2B**]. From
these data, it can be concluded that the N-atom in the OsVItN
precursor is retained in the OsIV-N4 product at NR, the N-atom
bound to Os.
Reaction between [1] and PPNN3 in dry CH3CN under N2 at 60
°C for 3 h resulted in a color change from purple to dark brown
with associated changes in the visible spectrum from λmax ) 498
nm to 486 and 452 nm. The brown solution was evaporated to
dryness by rotary evaporation, and the crude product was purified
The proposed structure for PPN[2] is further confirmed by 15N
NMR spectrosopic data in CD3CN for the highly labeled complexes,
PPN[2A**] and PPN[2B**].14 The Ost15N resonance at 1187 ppm
for [1*] is shifted to 489 ppm (NR) in PPN[2B**]. The other
resonance for PPN[2B**] at 668 ppm can be assigned to Nδ of the
* Corresponding authors. E-mails: (T.J.M.) tjmeyer@lanl.gov; (M.H.V.H.)
huynh@lanl.gov.
† Associate Laboratory Director for Strategic and Supporting Research, Los
Alamos National Laboratory, MS A127, Los Alamos, NM 87545. Telephone:
505-667-8597. Fax: 505-667-5450.
2-
15NR14Nâ14Nγ15Nδ ligand. Isotopomer PPN[2A**] shows two
‡ Director-Funded Postdoctoral Fellow, Los Alamos National Laboratory,
Chemistry Division, MS J514, Los Alamos, NM 87545. Telephone: 505-667-
3968. Fax: 505-667-9905.
doublet resonances at 489 and 730 ppm (1J(15N-15N) ) 6.5 Hz)
due to NR and Nâ, respectively.15 The 15N-15N one-bond
coupling constant of 6.5 Hz compares well with similar values
§ Los Alamos National Laboratory, Chemistry Division, MS J514, Los Alamos,
NM 87545.
1
| Department of Chemistry, Gettysburg College, Gettysburg, PA 17325.
for Os dinitrogen complexes, that is, J(15N-15N) ) 4.5 for mer-
9
4580
J. AM. CHEM. SOC. 2002, 124, 4580-4582
10.1021/ja0122086 CCC: $22.00 © 2002 American Chemical Society

C O M M U N I C A T I O N S
Table 2. Selected Infrared Data ((2 cm-1) for [OsIV(bpy)-
at 2045 ( 2 cm-1. As for [2]-, these observations are consistent
with the retention of the N3 structure in the N(OH)N3 ligand.
(Cl)3(N(OH)N3)] and Their 15N-Labeled Analogues in Nujol Mulls
-
IV
Reminiscent of [2]-, it can be inferred on the basis of the IR
data that the N-atom from OsVItN is retained, and that there is an
N-O bond in [6]. ν(Os-N) shifts from 1091 ( 2 cm-1 in [6] and
the mixture of [6A*] and [6B*] to 1075 ( 2 cm-1 in [6*] and the
mixture of [6A**] and [6B**]. It is not a coupled ν(NNO) stretch
as shown by its insensitivity to 15N substitution for 14N at the N
atom â to Os in [6A*]-[6B*] and [6A**]-[6B**]. Similarly, ν(N-
O) in [6] and the mixture of [6A*] and [6B*] shifts from 772 ( 2
cm-1 to 756 ( 2 cm-1 in [6*] and the mixture of [6A**] and
[6B**]. A ν(O-H) stretch appears at 3406 ( 2 cm-1 in all of the
Os(IV)-azidohydroxoamido complexes.
[Os (bpy)(Cl)3(N(OH)N )]
3
isotopic distribution
ν
asym(N -
)
ν(Os−N ) ν(N −O) ν(O−H)
3
R
R
[OsIV-14N(OH)14N14N14N] [6]a
[OsIV-15N(OH)14N14N14N] [6*]b
[OsIV-14N(OH)15N14N14N] [6A*]c
[OsIV-14N(OH)14N14N15N] [6B*]c
[OsIV-15N(OH)15N14N14N] [6A**]d
[OsIV-15N(OH)14N14N15N] [6B**]d
2058
2060
1092
1076
772
756
3404
3408
2046
2045
1091
1074
773
756
3407
3406
a Product from reaction between OrNMe3‚3H2O and PPN[OsIV
-
(bpy)(Cl)3(14N14N14N14N)]. b Product from reaction between OrNMe3‚3H2O
and PPN[OsIV(bpy)(Cl)3(15N14N14N14N)]. c Products from reaction between
OrNMe3‚3H2O and PPN[OsIV(bpy)(Cl)3(14N15N14N14N)] and PPN[OsIV
-
(bpy)(Cl)3(14N14N14N15N)]. d Products from reaction between OrNMe3‚
3H2O and PPN[OsIV(bpy)(Cl)3(15N15N14N14N)] and PPN[OsIV(bpy)(Cl)3-
(15N14N14N15N)].
Deprotonation of the coordinated N(OH)N3- ligand in [6] to the
bound N(O)N32- ligand results in an instability toward N2 evolution.
When [6] was redissolved in 3:1 (v/v) CH3CN:H2O, pH ) 9-12
containing a NaOH/NaH2PO4-NaOH/Na2HPO4 buffer, a rapid
reaction occurred with the effervescence of N2 gas evolution. The
resulting brown product is the corresponding Os(II)-dinitrogen
oxide complex, [OsII(bpy)(Cl)3(N2O)]- ([7]-), eq 8.
[OsII(Br)2(15N2)(PMe2Ph)3]16 and 1J(15N-15N) ) 4.0 for mer-
[OsII(Cl)2(15N2)(PMe2Ph)3].17
Formulation of PPN[2] as a diamagnetic d4 Os(IV)-azidoimido
2-
complex containing the N4 ligand with retention of the mer-
geometry is consistent with its spectroscopic properties. In the 1H
NMR spectrum, the expected eight resonances of bpy appear from
8.05 to 9.22 ppm, similar to the pattern of resonances for the parent
mer-[OsVI(bpy)(Cl)3(N)]. The visible spectrum in CH3CN has a
pattern of bands, λmax ) 486 and 452 nm, analogous to bands at
521 and 421 nm for the analogous Os(IV)-cyanoimido complex,
[OsIV(bpy)(Cl)3(NCN)]-.6 Closely related reactions occur between
[OsVI(Me2bpy)(Cl)3(N)] (Me2bpy ) 4,4′-dimethyl-2,2′-bipyridine),
[OsVI(phen)(Cl)3(N)] (phen ) 1,10-phenanthroline), or [OsVI-
(Ph2phen)(Cl)3(N)] (Ph2phen ) 4,7-diphenyl-1,10-phenanthroline)
and PPNN3 to give the corresponding Os(IV)-azidoimido products,
[OsIV(L2)(Cl)3(N4)]- (L2 ) Me2bpy ) [3]-, phen ) [4]-, and
Ph2phen ) [5]-). They were also isolated as PPN+ salts and
characterized by cyclic voltammetry, elemental analysis, and
UV-visible and IR spectroscopies.12
mer-[OsIV(bpy)(Cl) (N(OH)N )]
-
+ OH f
3
3
[6]
mer-[OsII(bpy)(Cl)3(N2O)]-
[7]-
+ N2 + H2O (8)
This reaction may occur by deprotonation and internal electron
transfer, eq 9.
We have begun to explore the reactivity of these novel
complexes. For PPN[2] in 0.1 M TBAH/CH3CN (TBAH )
tetrabutylammonium hexafluorophosphate), chemically reversible
waves appear in the cyclic voltammogram at E1/2 ) +1.40,
+0.88, and -0.82 V (versus SSCE) for the Os(VI/V), Os(V/IV),
The putative OsII-N(O)N3 intermediate is analogous to inter-
mediates proposed in reactions between metal nitrosyls and azide
ion, eq 10.18
and Os(IV/III) couples, respectively. They compare with E1/2
)
+1.72, +0.90, and -0.40 V for the same couples for PPN[OsIV-
(bpy)(Cl)3(NCN)].6 In dry CH3CN with added OrNMe3‚3H2O, a
rapid color change occurs from dark to lighter brown. The product
was isolated (68% yield) from the solution and characterized by
elemental analysis and IR and 1H NMR spectroscopies.12 Its
formulation as the Os(IV)-azidohydroxoamido complex, mer-
[OsIV(bpy)(Cl)3(14N(OH)14N3)] ([6]), in eq 7 is further supported
by 15N-labeling. This appears to be the first example of the
cis-[RuII(bpy)2(NO)(Cl)]2+ + N3- f
{RuII(bpy)2(N(O)N3)(Cl)}+ +CH CN8
cis-[RuII(bpy)2(NCCH3)(Cl)]+ + N2O + N2 (10)
3
Complex [7]- was isolated (42% yield) as the PPN+ salt and
characterized by elemental analysis, cyclic voltammetry, and IR
-
N(OH)N3 ligand.
1
(Table 3) and H NMR spectroscopies.12 It is the second example
of a characterized N2O transition-metal complex.19
mer-[OsIV(bpy)(Cl)3(NN3)]-
+ OrNMe3 + H2O f
In PPN[OsII(bpy)(Cl)3(14N14NO)] (PPN[7]), the pseudosymmetric
(largely N-N) N2O stretch appears at 1245 cm-1 (ν1), doubly de-
generate bends appear at 536 and 533 cm-1 (ν2), and a pseudo-
asymmetric (largely N-O) stretch appears at 2252 cm-1 (ν3),
Table 3. ν1 and ν2 are shifted to lower energy upon coordination
(gaseous N2O: ν1 ) 1286 and ν2 ) 589 cm-1),20 but ν3 is
shifted to higher energy (gaseous N2O: ν3 ) 2224 cm-1) as in
[RuII(NH3)5(N2O)]2+ 21 and for N2O absorbed on alkali-halide
films22 or on R-Cr2O3.23
[2]-
mer-[OsIV(bpy)(Cl) (N(OH)N )]
-
+ NMe3 + OH (7)
3
3
[6]
As shown in Table 2, in mer-[OsIV(bpy)(Cl)3(14N(OH)14N3)] ([6])
and its 15N analogue, [OsIV(bpy)(Cl)3(15N(OH)14N3)] ([6*]), νasym(N3-)
appears at 2059 ( 2 cm-1. In mixtures of [OsIV(bpy)(Cl)3(14N-
(OH)15N14N14N)] ([6A*]) and [OsIV(bpy)(Cl)3(14N(OH)14N14N15N)]
([6B*]) or of [OsIV(bpy)(Cl)3(15N(OH)15N14N14N)] ([6A**]) and
[OsIV(bpy)(Cl)3(15N(OH)14N14N15N)] ([6B**]), νasym(N3-) appears
In the product of reaction 7 followed by 8 with [OsVI(bpy)-
(Cl)3(15N)] as the starting complex and 14N3-, ν1 ) 1238 and
ν3 ) 2221 cm-1. The 15N isotope effects on ν1 (7 cm-1) and
9
J. AM. CHEM. SOC. VOL. 124, NO. 17, 2002 4581

C O M M U N I C A T I O N S
Table 3. Selected Infrared Data ((2 cm-1) for PPN-
from the Director’s Office of Los Alamos National Laboratory.
Los Alamos National Laboratory is operated by the University of
California for the U.S. Department of Energy under Contract
W-7405-ENG-36.
[OsII(bpy)(Cl)3(N2O)] and Its 15N-Labeled Analogues in Nujol Mulls
N O bands
II
[Os (bpy)(Cl)3(N O)]-
2
2
isotopic distribution
ν1a (largely N−N)
ν2b
ν3c (largely N−O)
[OsII-14N14NO]- [7]- d
[OsII-14N15NO]- [7*]- e
[OsII-14N14NO]- [7]- f
[OsII-15N14NO]- [7A*]- f
[OsII-14N15NO]- [7*]- g
[OsII-15N15NO]- [7**]- g
1245
1238
536, 533
532, 526
2252
2221
Supporting Information Available: Text containing characteriza-
tions is included (PDF). This material is available free of charge via
the Internet at http://pubs.acs.org.
1244, 1237
1237, 1233
535, 532
532, 525
2252
2221, 2212
References
a Pseudosymmetric stretch. b Doubly degenerate bend. c Pseudoasym-
metric stretch. d Product obtained from [OsIV(bpy)(Cl)3(14N(OH)14N14N14N)]
(1) (a) Pawson, D.; Griffith, W. P. J. Chem. Soc., Dalton Trans. 1975,
417-423. (b) Demadis, K. D.; Bakir, M.; Klesczewski, B. G.; Williams,
D. S.; White, P. S.; Meyer, T. J. Inorg. Chim. Acta 1998, 270, 511-526.
(2) Williams, D. S.; Meyer, T. J.; White, P. S. J. Am. Chem. Soc. 1995, 117,
823-824.
in 3:1 (v/v) CH3CN:H2O at pH
)
10. e Product obtained from
[OsIV(bpy)(Cl)3(15N(OH)14N14N14N)] in 3:1 (v/v) CH3CN:H2O at pH ) 10.
f Products obtained from [OsIV(bpy)(Cl)3(14N(OH)14N14N15N)] and
[OsIV(bpy)(Cl)3(14N(OH)15N14N14N)] in 3:1 (v/v) CH3CN:H2O at pH ) 10.
g Products obtained from [OsIV(bpy)(Cl)3(15N(OH)14N14N15N)] and
[OsIV(bpy)(Cl)3(15N(OH)15N14N14N)] in 3:1 (v/v) CH3CN:H2O at pH ) 10.
(3) Crevier, T. J.; Mayer, J. M. J. Am. Chem. Soc. 1998, 120, 5595-5596.
(4) Crevier, T. J.; Mayer, J. M. Angew. Chem., Int. Ed. 1998, 37 (13),
1891-1893.
(5) Brown, S. N. Inorg. Chem. 2000, 39, 378-381.
(6) Huynh, M. H. V.; White, P. S.; Carter, C. A. G.; Meyer, T. J. Angew.
Chem. Int. Ed. 2001, 40 (16), 3037-3039.
ν3 (31 cm-1) are consistent with the isotopic distribution PPN-
[OsII(bpy)(Cl)3(14N15NO)] in the product (PPN[7*]). This conclusion
(7) (a) Huynh, M. H. V.; White, P. S.; Meyer, T. J. Angew. Chem., Int. Ed.
2000, 39 (22), 4101-4104. (b) Huynh, M. H. V.; White, P. S.; Meyer, T.
J. J. Am. Chem. Soc. 2001, 123, 9170-9171.
is also in agreement with: (1) ν1(14N14NO) at 1244 cm-1
,
(8) Huynh, M. H. V.; El-Samanody, E.-S.; Demadis, K. D.; White, P. S.;
Meyer, T. J. J. Am. Chem. Soc. 1999, 121, 1403-1404.
(9) Bakir, M.; White, P. S.; Dovletoglou, A.; Meyer, T. J. Inorg. Chem. 1991,
30, 2835-2836.
ν1(15N14NO) at 1237 cm-1, and ν3 at 2252 cm-1 in the mixture of
PPN[7] and PPN[OsII(bpy)(Cl)3(15N14NO)] ([7A*]-) in Table 3 and
(2) ν1(14N15NO) ) 1237 cm-1, ν1(15N15NO) ) 1233 cm-1
,
(10) Huynh, M. H. V.; White, P. S.; Meyer, T. J. Inorg. Chem. 2000, 39, 2825-
ν3(14N15NO) ) 2221 cm-1, and ν3(15N15NO) ) 2212 cm-1. In the
mixture of PPN[7*] and PPN[OsII(bpy)(Cl)3(15N15NO)] (PPN[7**]),
the 15N shifts of ν2 in Table 3 are similar to those found with 15N-
labeling in [RuII(NH3)5(N2O)]2+ formed by Cr2+ reduction of
[RuIII(NH3)5(Cl)]Cl2 in the presence of N2O (14N14NO, 14N15NO,
and 15N14NO).19a
2830.
(11) For an example of a bridging N4 ligand, see: Mass, V. W.; Kujanek, R.;
Baum, G.; Dehnicke, K. Angew. Chem., Int. Ed. Engl. 1984, 23 (2),
149-149.
(12) Detailed characterization data are provided in the Supporting Information
Materials.
(13) Prepared by the reaction between mer-[OsVI(bpy)(Cl)3(15N)] ([1*])6 and
PPN14N3.
(14) (a) 30 MHz 15N NMR measurements were conducted by using a Varian
Unity series spectrometer. All 15N chemical shifts are reported relative to
the resonance for a saturated solution of 15NH4Cl in D2O at + 353.0 ppm,
referred to a neat nitromethane external standard. (b) Witanowski, M.;
Stefaniak, L. In Annual reports on NMR Spectrosopy: Nitrogen NMR
Spectroscopy; Webb, G. A., Ed.; Academic Press: New York, 1983;
Vol. 15, p 138.
The 15N-labeling results in Table 3 are consistent with coordina-
tion through the terminal nitrogen of N2O with the original N-atom
from OsVItN appearing at the â-position in OsII-NRNâO. Given
the mechanism implied in eq 9, formation of the final product
must entail Os-N linkage isomerization from the R to the â position
(15) The 15N NMR resonance for mono-labeled azide, 15N14N14N-, is at
431 ppm.
(16) Dilworth, J. R.; Donovanmtunzi, S.; Kan, C. T.; Richards, R. L.;
Mason, J. Inorg. Chim. Acta, Lett. 1981, 53, L161-L162.
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2-
in the N2 extrusion reaction of the N(O)N3 ligand. A related
observation has been made in the reaction between [RuII-
(NH3)5(15NO)]3+ and hydroxylamine (14NH2OH) which forms
[RuII(NH3)5(14N15NO)]2+ and H2O.21
The series of transformations starting in eq 6 with the formation
of mer-[OsIV(bpy)(Cl)3(NN3)]- followed by hydroxylation to form
mer-[OsIV(bpy)(Cl)3(N(OH)N3)] and then deprotonation and extru-
sion of N2 to give [OsII(bpy)(Cl)3(N2O)]- is a remarkable sequence
of reactions in the chemistry of coordinated ligands. It involves
2-
two new examples of coordinated ligands (azidoimido N4 and
azidohydroxoamido N(OH)N3-) and a reaction sequence which
allows for the stepwise addition of N and O atoms to a nitrido
ligand.
(21) Bottomley, F.; Crawford, J. R. J. Am. Chem. Soc. 1972, 94, 9092-9095.
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Acknowledgments are made to the Laboratory Directed Re-
search and Development Program for support of this research.
M.H.V.H. gratefully acknowledges postdoctoral fellowship support
JA0122086
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4582 J. AM. CHEM. SOC. VOL. 124, NO. 17, 2002