Spectroscopy, Molecular Structure, Electrochemistry, and Reactivity of Vanadium(IV,V) Imido Complexes of 5,7,12,14-Tetramethyldibenzo[b.i][1,4,8,11]tetraazacyclotetradecine

Article abstract of DOI:10.1021/ic9508381

The synthesis of new imidovanadium(IV) complexes containing the tetradendate dianionic 5,7,12,14-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato moiety (TMTAA^2-) is reported. Stirring of either [(HTMTAA)VCl₂]Cl or (TMTAA)VCl₂ in solution with NH₂R was used to prepare very moisture-sensitive, paramagnetic compounds of the type (TMTAA)V=NR (2, R = CH₃, t-C₄H₅, C₄H₂, C₆F₅ and N(CH₃)₂) in high yields. Complexes 2 were characterized by EPR, IR, UV/vis, and mass spectroscopic techniques. CV measurements indicate a reversible le-oxidation to the corresponding diamagnetic vanadium (V) cations [(TMTAA)V=NR]⁺ (4). Complexes 4 were prepared in preparative scale by oxidation of 2 with 1 equiv of [(C₅H₅)Fe]SbF₆ (3) and characterized by heteronuclear NMR, IR, and UV/vis spectroscopic methods. While the V=NR group in complexes 2 does not react with Cr(CO)₅ or Pt(P(C₆H₅)₃)₂ under complexation, cycloaddition of 2a with hexfluoracetone has been observed. This reactivity has been compared to (TMTAA)V&=O (5), which is demonstrated to undergo addition and cycloaddition reactions with hexafluoracetone, hexfluorpropene oxide, sulfur trioxide and triflic anhydride (complexes 8a-d). Complex 4b (R = t-C₄H₉) has been crystallographically characterized and the results discussed with those of 5 and [(TMTAA)V=O]SbF₆ (6).

Full text of DOI:10.1021/ic9508381

1808
Inorg. Chem. 1996, 35, 1808-1813
Spectroscopy, Molecular Structure, Electrochemistry, and Reactivity of Vanadium(IV,V)
Imido Complexes of 5,7,12,14-Tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine
Hans Schumann1
Fakulta¨t fu¨r Chemie, Universita¨t Bielefeld, Universita¨tsstrasse 25, D-33615 Bielefeld, Germany
ReceiVed July 7, 1995X
The synthesis of new imidovanadium(IV) complexes containing the tetradendate dianionic 5,7,12,14-
tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato moiety (TMTAA2-) is reported. Stirring of either
[(HTMTAA)VCl2]Cl or (TMTAA)VCl2 in solution with NH2R was used to prepare very moisture-sensitive,
paramagnetic compounds of the type (TMTAA)VdNR (2, R ) CH3, t-C4H9, C6H5, C6F5 and N(CH3)2) in high
yields. Complexes 2 were characterized by EPR, IR, UV/vis, and mass spectroscopic techniques. CV
measurements indicate a reversible 1e-oxidation to the corresponding diamagnetic vanadium(V) cations
[(TMTAA)VdNR]+ (4). Complexes 4 were prepared in preparative scale by oxidation of 2 with 1 equiv of
[(C5H5)2Fe]SbF6 (3) and characterized by heteronuclear NMR, IR, and UV/vis spectroscopic methods. While
the VdNR group in complexes 2 does not react with Cr(CO)5 or Pt(P(C6H5)3)2 under complexation, cycloaddition
of 2a with hexfluoracetone has been observed. This reactivity has been compared to (TMTAA)VdO (5), which
is demonstrated to undergo addition and cycloaddition reactions with hexafluoracetone, hexfluorpropene oxide,
sulfur trioxide and triflic anhydride (complexes 8a-d). Complex 4b (R ) t-C4H9) has been crystallographically
characterized and the results discussed with those of 5 and [(TMTAA)VdO]SbF6 (6).
Introduction
Scheme 1
Vanadium plays an important role in various biological
processes,2 which has invoked increased interest in the synthesis
and study of vanadium +IV and +V coordination compounds
over the last decade.3 The majority of these investigations has
been centered on systems containing the VO2+/3+ moieties, while
far less information is available on non-oxo vanadium centers.4
Non-oxo vanadium centers have been identified for example
in amavadin, a VIV complex of unknown function isolated from
mushrooms of the genus Amanita,5 and for the co-factor in
vanadium nitrogenase.6 Due to the presence of additional
interactions with nitrogen ligands beside the often present
chelating ligands in the above mentioned biological systems,
the preparation and redox chemistry of macrocyclic imidova-
nadium(IV,V) complexes are of interest due to the possible
access to new model systems. Compounds containing a
VdNR2+/3+ group and a macrocyclic ligand are very rare:
Buchler et al. reported the synthesis and characterization of a
series of alkyl and arylimidovanadium(IV) 5,10,15,20-tetra(p-
tolyl)porphyrinates7 and Sundermeyer et al. described recently
X Abstract published in AdVance ACS Abstracts, February 15, 1996.
(1) Present address: Strusen 51, D-33729 Bielefeld, Germany.
(2) (a) Chasteen, N. D. Struct. Bonding 1983, 53, 105. (b) Rehder, D.
Angew. Chem., Int. Ed. Engl. 1991, 30, 148. (c) Rehder, D. Biometals
1992, 5, 3.
(3) Boas, L. V., Pessoa, J. C. Vanadium. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon Press: Oxford, England, 1987; Vol. 3, p 453.
(4) (a) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley-
Interscience: New York 1988. (b) Mohan, M.; Holmes, S. M.;
Butcher, R. J.; Jasinski, J. P.; Carrano, C. J. Inorg. Chem. 1992, 31,
2029. (c) Hughes, D. L.; Kleinkes, U.; Leigh, G. J.; Maiwald, M.;
Sanders, J. R.; Sudbrake, C.; Weisner, J. J. Chem. Soc., Dalton Trans.
1993, 3093. (d) Reynolds, J. G.; Jones, E. L.; Huffman, J. C.; Christou,
G. Polyhedron 1993, 12, 407. (e) Vergopoulos, V.; Jantzen, S.; Julien,
N.; Rose, E.; Rehder, D. Z. Naturforsch., B 1994, 49, 1127. (f)
Vergopoulos, V.; Jantzen, S.; Rodewald, D.; Rehder, D. J. Chem. Soc.,
Chem. Commun. 1995, 377.
(tert-butylimido)dichloro(tris(3,5-dimethyl-1-pyrazolyl)hydri-
doborato) vanadium(V).8
The synthesis, the molecular structure, and the redox chem-
istry of the new (Imido)vanadium(IV,V) dibenzotetraaza[14]-
annulene complexes is described herein. The chemistry of the
VdNR moiety is also briefly compared to those of the VdO
group with respect to cycloadditions. The general structure of
the macrocyclic ligand H2TMTAA and of the complexes
(TMTAA)VdE (E ) O, NR) is shown in Scheme 1.
(5) Meisch, H.-U.; Schmitt, J. A.; Reinle, W. Z. Naturforsch., C 1978,
33, 1; Naturwissenschaften 1979, 66, 620.
(7) Buchler, J. W.; Pfeifer, S. Z. Naturforsch., B 1985, 40, 1362.
(8) Sundermeyer, J.; Putterlik, J.; Foth, M.; Field, J. S.; Ramesar, N. Chem.
Ber. 1994, 127, 1201.
(6) (a) Burgess, B. K. Chem. ReV. 1990, 90, 1377. (b) Eady, R. R.; Leigh,
G. J. J. Chem. Soc., Dalton Trans. 1994, 2739.
0020-1669/96/1335-1808$12.00/0 © 1996 American Chemical Society

(Imido)vanadium Complexes
Inorganic Chemistry, Vol. 35, No. 7, 1996 1809
Alternatively, the complexes may also be prepared by reaction of
[(HTMTAA)VCl2]Cl (1a) with an excess of NH2R but identical workup
afforded less pure and crystalline products.
Experimental Section
Materials. The ligand H2TMTAA,9 the complexes [(HTMTAA)-
VCl2]Cl (1a), (TMTAA)VCl2 (1b),10 (TMTAA)VdO (5),11 and [(C5H5)2-
Fe]SbF6 (3)12 were obtained as reported in the literature. The remaining
required chemicals were of reagent grade (Aldrich, Merck) and dried
prior to use. All syntheses were carried out in a dry/inert atmosphere
of purified argon by employing standard Schlenk glassware. Due to
the extreme moisture sensitivity of both educts and products, all
glassware was heated under high vacuum for at least 1 h to remove
last traces of moisture. The solvents were dried over CaH2 and degassed
under reflux.
[(TMTAA)VdNR]SbF6 (4a-e). A mixture of 2 (ca. 0.2-0.35 g,
0.54 mmol) and [(C5H5)2Fe]SbF6 (3; 0.22 g, 0.52 mmol) was stirred in
CH2Cl2 (25 mL) for 2 h. The solution was filtered and evaporated to
dryness. The formed ferrocene was removed by repeated extraction
with pentane. The remaining solid was recrystallized from CH2Cl2/
pentane at -25 °C for 12 h (4b from CH3CN/ether). The deep green
solids were washed with pentane and ether and dried in vacuo; yields:
0.31 g, 91% (4a), 0.32 g, 87% (4b), 0.33 g, 89% (4c), 0.35 g, 82%
(4d), and 0.30 g, 85% (4e). Anal. Calcd (found) for C23H25F6N5SbV
(4a): C, 41.96 (41.35); H, 3.80 (3.89); N, 10.64 (10.20). Anal. Calcd
(found) for C26H31F6N5SbV‚CH3CN (4b): C, 45.34 (45.88); H, 4.59
(5.07); N, 11.34 (11.24). Calcd (found) for C28H27F6N5SbV (4c): C,
46.68 (46.08); H, 3.75 (4.11); N, 9.72 (9.40). Anal. Calcd (found)
for C28H22F11N5SbV (4d): C, 41.49 (41.09); H, 2.72 (2.75); N, 8.64
(8.40). Anal. Calcd (found) for C24H28F6N6SbV (4e): C, 41.94 (41.76);
H, 4.08 (3.91); N, 12.23 (11.90).
Reactions of 2a with Organometallic Agents. To a solution of
2a (ca. 0.21 g, 0.5 mmol) in THF (10 mL) was added either (c-C8H14)-
Cr(CO)5 (0.15 g, 0.5 mmol) or (C2H4)Pt(P(C6H5)3)2 (0.37 g, 0.5 mmol)
as solid. The mixture was stirred after addition for 4 h without apparent
color change. Workup consisted of solvent evaporation and repeated
washings of the residue with pentane/ether 1/1. IR and EPR spectra
of the deep green residue indicated only the presence of unreacted 2a.
Reaction of 2a with Hexafluoracetone. Formation of (TMTAA)V-
(C4H3F6NO) (7). A CH2Cl2 solution (20 mL) of 2a (0.41 g, ca. 1
mmol) was stirred under an atmosphere of (CF3)2CO. Within minutes,
the reaction solution turned dark green and stirring was continued for
4 h. Concentration to 5 mL and addition of pentane (10 mL) caused
precipitation of a dark green solid. The product was filtered off, washed
with ether and pentane, and dried in vacuo for 1 h at ambient
temperature; yield: 0.56 g, 95%. Anal. Calcd (found) for C26H25F6N5-
OV (7): C, 53.07 (53.47); H, 4.25 (4.40); N, 11.91 (12.1). MS {EI}
calcd (found), m/e: 428 (427) [M - C3F5NO]+, 147 [C3F5O]+.
Reaction of 5 with Hexafluoracetone and Hexafluorpropene
Oxide. Formation of (TMTAA)V(C3F6O2) (8a and 8b). A solution
of 5 (1.0 g, 2.45 mmol) in CH2Cl2 (30 mL) was stirred under an
atmosphere of either hexafluoracetone or hexafluorpropene oxide for
1 h. The solution turned from green (5) to dark green (8) within
minutes, and eventually a dark solid began to separate out. Precipitation
was completed by addition of ether (30 mL) and further stirring for 2
h. The dark green solids were filtered off and washed with ether;
yields: 1.34 g, 95% (8a) and 1.28 g, 91% (8b). Anal. Calcd (found)
for C25H22F6N4O2V (8a/b): C, 52.18 (8a 52.74, 8a 52.45); H, 3.83 (8a
3.96, 8b 4.07); N, 9.74 (8a 10.15, 8b 10.21). MS {EI} calcd (found),
m/e: 409 (409) [M - C3F6O]+ for both 8a and 8b.
Physical Measurements. Infared spectra were recorded on Perkin
Elmer 580 and Bruker IFS66 spectrometers as KBr pellets, and
electronic spectra were obtained with a Omega UV spectrometer. EPR
spectra were obtained using a Bruker ECS 106 spectrometer with DPPH
(g ) 2.0037) as an external standard. NMR spectra were recorded on
Bruker AM 400 (1H, 13C{1H}, vs internal TMS) and Bruker WM 300/
AM 100 spectrometer (51V; vs external 10% VOCl3 in C6D6). Mass
spectra were obtained on Finigan MAT 311 A (EI mode, 70 eV) or
MAT 95 instruments (FAB mode, dimethoxybenzyl alcohol as matrix).
Variable-temperature susceptibility measurements between 120 and 300
K were carried out by the Faraday method using a combination of
Sartorius 4411 microbalance, Bruker B-M4 research magnet, and B-VT
1000 temperature controller. The electrochemical measurements were
performed at room temperature under O2-free conditions using a three-
electrode configuration: glassy-carbon working electrode, Pt-wire
counter electrode, and SCE reference electrode. The supporting
electrolyte was 0.1 M [N(C4H9-n)4]ClO4 in CH2Cl2, and all solutions
were ca. 1 mM in complex. A range from -2.6 to +1.0 V was
measured with a scan rate of 1000 mV/s.
Synthesis of Complexes. (TMTAA)VdNCH3 (2a) and (TMTAA)-
VdN(t-C4H9) (2b). A stirred suspension of [(HTMTAA)VCl2]Cl (1a;
1.93 g, 3.85 mmol) in 1,2-Cl2C2H4 (30 mL) was slowly treated with
either a stream of anhydrous NH2CH3 (excess) or by dropwise addition
of NH2C4H9-t (2.10 g, 28.6 mmol, excess). During the addition, the
suspension dissolved and the color changed rapidly to deep green.
Stirring of the mixtures was continued for 12 h, after which all volatiles
were removed under vacuum. The residues were extracted with boiling
toluene (3 × 25 mL). The combined extracts were concentrated to ca.
15 mL, layered with an equal volume of pentane, and kept in a freezer
at -20 °C for 2 d. The obtained deep green solids were collected by
filtration, washed with pentane and dried in vacuo; yields: 1.36 g, 84%
(2a) and 1.39 g, 78% (2b). Anal. Calcd (found) for C23H25N5V (2a):
C, 65.40 (65.67); H, 5.92 (6.17); N, 16.59 (16.39); MS {EI} calcd
(found), m/e: 422 (422) [M]+. Anal. Calcd (found) for C26H31N5V
(2b): C, 67.24 (67.40); H, 6.68 (6.69); N, 15.09 (14.89); MS {EI}
calcd (found), m/e: 464 (464) [M]+.
Reaction of 5 with SO3 and Triflic Anhydride. Formation of
(TMTAA)VdNR (R ) C6H5 (2c), C6F5 (2d), N(CH3)2 (2e)). To
a solution of in-situ prepared (TMTAA)VCl2 (1b; ca. 3 mmol) in 1,2-
Cl2C2H4 (30 mL) was added NH2R (9 mmol) as solution in CH2Cl2
(10 mL) over 15 min. The color changed rapidly to a deep green, and
stirring was continued for 4 h. The reaction solution was then
evaporated to dryness in vacuo and the residue extracted with boiling
toluene. Workup as above gave deep green crystalline solids; yields:
1.23 g, 85% (2c), 1.15 g, 67% (2d), and 0.95 g, 70% (2e). Anal. Calcd
(found) for C28H27N5V (2c): C, 69.42 (68.62); H, 5.58 (5.96); N, 14.46
(14.10); MS {EI} calcd (found), m/e: 484 (484) [M]+. Anal. Calcd
(found) for C28H22F5N5V (2d): C, 58.54 (58.74); H, 3.83 (4.05); N,
12.20 (12.42); MS {EI} calcd (found), m/e: 574 (574) [M]+. Anal.
Calcd (found) for C24H28N6V (2e): C, 63.86 (63.64); H, 6.21 (6.15);
N, 18.63 (18.50). MS {EI} calcd (found), m/e: 423 (423) [M - N2]+.
(TMTAA)V(O2SO2) (8c) and (TMTAA)V(OSO2CF3)2 (8d).
A
solution of either freshly sublimed SO3 (0.240 g, 4.0 mmol) or [CF3-
SO2]2O (1.13 g, 4.0 mmol) in CH2Cl2 (20 mL) was slowly added to a
solution of 5 (1.64 g, 4.0 mmol) in CH2Cl2 (40 mL) at 0 °C over 0.5
h. For each solution, a rapid color change from green (5) to brown-
green (8) was noted and the products started to precipitate. After 2 h
of stirring at ambient temperature, ether (30 mL) was added to each
solution to complete the precipitation. The brown microcrystalline
solids were isolated by filtration and washed repeatedly with CH2Cl2
and ether to remove traces of 5; yields: 1.78 g, 91% (8c) and 2.71 g,
97% (8d). Anal. Calcd (found) for C22H22N4O4SV (8c): C, 54.00
(54.13); H, 4.50 (4.62); N, 11.45 (11.34). Calcd (found) for
C24H22F6N4O6S2V (8d): C, 41.68 (40.95), H, 3.18 (3.12); N 8.11 (7.96).
MS {EI} calcd (found), m/e: 409 (409) [M]+ of 5 due to decomposition.
FAB MS measurements were attempted, but no [M]+ peak has been
observed for either 8c or 8d.
X-ray Structure Determination. Single crystals of [(TMTAA)VdN-
(t-C4H9)]SbF6 (4b) were grown by layering a dilute solution of 4b in
CH3CN with an equal amount of ether at 0 °C over 3 d. X-ray data
were collected on a Siemens R3m/V diffractometer with graphite
monochromated Mo KR radiation using a ω-2θ scan mode. Crystal-
lographic details are given in Table 1. The unit cell dimensions were
obtained by least-squares refinement of 20 automatically centered
(9) (a) Abbreviation: TMTAA ) dianion of 5,7,12,14-tetramethyldibenzo-
[b,i][1,4,8,11]tetraazacyclotetradecine. (b) Synthesis: Goedken, V. L.;
Weiss, M. C. Inorg. Synth. 1980, 20, 115.
(10) (a) Goedken, V. L.; Ladd, J. A. J. Chem. Soc., Chem. Commun. 1981,
910. (b) Yang, C.-H.; Ladd, J. A.; Goedken, V. L. J. Coord. Chem.
1988, 18, 317. (c) Schumann, H. Polyhedron, in press.
(11) (a) Compare 10a and 10b. (b) Lee, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. J. Chem. Soc., Dalton Trans. 1989, 145. (c) Cotton, F.
A.; Czuchajowska, J.; Feng, X. Inorg. Chem. 1991, 30, 349.
(12) Schumann, H. J. Organomet. Chem. 1986, 304, 341.

1810 Inorganic Chemistry, Vol. 35, No. 7, 1996
Schumann
Table 1. Crystallographic Data for [(TMTAA)VdNC4H9-t]SbF6
(4b)
Scheme 2
formula
fw
C28H34F6N6SbV V, pm
1590.4(8) × 106
741.3
Z
D
2
cryst size, mm 0.25 × 0.2 × 0.2
calc, g cm-1
1.548
cryst syst
space group
a, pm
monoclinic
P2/c
1011.8(3)
834.4(2)
1890.7(6)
94.87(2)
λ(MoKR), pm 71.073
µ, mm-1
temp, K
F(000)
R
1.200
294
744
0.063
0.062
b, pm
c, pm
â, deg
a
Rw
2
a Rw ) (∑w(|Fo| - |Fc|)2/(∑w|Fo| )1/2 for F > 4.0 σ(F).
reflections. During data collection three standard reflections monitored
after every 97 reflections indicated no decay, and data were corrected
for absorption by empirical methods. A total of 3693 reflections were
collected in the range 2θ ) 4 to 52°, with h ) -12 to 0, k ) 0 to 10
and l ) ( 23, of which 3156 independent reflections with F > 4 σ(F)
were used for structure determination. The structure was solved by
direct methods and refined by full-matrix-least-squares techniques using
the program SHELXTL PLUS (VMS).13 Due to disorder, the atoms
C(13), C(14), and C(15) have been refined with an occupancy factor
of 0.5. The final least-squares refinement converged to R ) 0.063
and Rw ) 0.062. The numbers of parameters refined was 184, and the
maximum fluctuation in the final ∆F map was in the range +0.60 ×
10-6 to -0.69 × 10-6 e/pm3.
Results and Discussion
Synthesis and Characterization. The macrocyclic vana-
dium(IV) dichloride [(HTMTAA)VCl2]Cl (1a)10 reacts with an
excess of NH2R (R ) CH3, t-C4H9) or (TMTAA)VCl2 (1b)10c
with three equivalents NH2R (R ) C6H5, C6F5, N(CH3)2) under
formation of the V(IV) organoimido complexes, 2 (Scheme 2).
Within seconds after the addition of the amine, the violet
suspension of the starting complex 1a dissolves and the solution
changes into a deep green color of the imido complex, 2. For
1b, a very fast color change from dark brown to deep green is
observed. Independently of the vanadium educts used for the
preparation, work-up of these reaction solutions affords deep
green, very moisture-sensitive solids in good yields.
cessfully attempted by addition of either (C5H5)2Co or Na/Hg
to THF solutions of either 2a or 2b as describted recently for
(TMTAA)VdO (5),15 the preparative oxidation of complexes
2 with [(C5H5)2Fe]SbF6 (3)12 has been successful with the
isolation of the (imido)vanadium(V) tetramethyldibenzotetraaza-
[14]annulene cations 4 (Scheme 3).
Characterization of the isolated complexes 2 is given in Table
2 with analytical data stated in the Experimental Section. These
compounds are EPR-active (µeff ) 1.77 to 1.83 µB at 294 K)
and exhibit an isotropic eight-line spectrum in CH2Cl2 solution
with giso values around 1.978 and Aiso(51V) ) 87-90 G at 294
K. Measurements in the solid state between 120 and 300 K
show only a single unresolved broad signal around g ) 2.0.
Stirring an equal molar amount of 2 and 3 in CH2Cl2 for
about 2 h results in the formation of orange-green solutions.
Workup gives complete separation of the green, airstable but
-
also very moisture-sensitive crystalline complexes 4 as SbF6
salts from the by-product ferrocene in good yield. Magnetic
measurements of 4 confirm their diamagnetic nature in agree-
ment with a V- (VIV to VV)15 rather then a ligand-centered
oxidation as observed often with Ni as coordinated metal center
with tetraza[14]annulene-type ligands.18 For the complexes 4,
the 1H and 13C NMR spectra indicate the presence of an
unchanged dianionic 5,7,12,14-tetramethyldibenzo[14]annulene
core together with the expected signals due to the NR group.
More informative are the obtained 51V NMR data (reference
external VOCl3): The obtained shift range is ca. 70 ppm with
the extreme values observed at δ ) -554 ppm (H1/2 ) 265
Hz; 4a) and δ ) -487 ppm (H1/2 ) 310 Hz; 4c). These values
are well within the known 51V NMR range for VV compounds19a
and the upfield position of the 51V NMR signal of the imido
vanadium (V) complexes 4 from the position the corresponding
1
The EPR spectra are attributable to a single S ) /2 species in
which the unpaired electron in a dxy orbital is coupled to the
nuclear spin of the vanadium nucleus (I ) 7/2).14 CV measure-
ments for complexes 2 (Table 3) indicate a reversible oxidation
in the range 0.30-0.34 V and an irreversible reduction at ca.
-1.95 V vs SCE. On the basis of the observed range for the
oxidation waves, this process is attributed to the 1e-oxidation
of the coordinated vanadium center from VIV (2) to VV (4).
Very similar values have been found for (TMTAA)VdO (5)15
and related substituted (TMTAA)VdO systems.16 The irrevers-
ible reduction waves around -2 V vs SCE have been attributed
to reduction processes within the ligand framework followed
by polymerization upon the electrode as investigated in some
details recently on substituted (TMTAA)Ni complexes.17 While
experimental verification of the reduction process was unsuc-
(17) (a) Keita, B.; Lu, Y. W.; Nadjo, L. J. Electroanal. Chem. 1994, 367,
285. (b) Deronzier, A.; Marques, M.-J. J. Electroanal. Chem. 1994,
370, 151.
(18) (a) Dabrowiak, J. C.; Fisher, D. P.; McElroy, F. C.; Macero, D. J.
Inorg. Chem. 1979, 18, 2304. (b) Wuu, Y.-M.; Peng, S.-M.; Chang,
H. J. Inorg. Nucl. Chem. 1980, 42, 839. (c) Hunziker, M.; Loeliger,
H.; Rihs, G.; Hilti, B. HelV. Chim. Acta 1981, 64, 2544. (d) Stach, J.;
Kirmse, R.; Ja¨ger, E.-G. Z. Chem. 1984, 24, 416.
(13) G. M. Sheldrick, program package SHELXTL-PLUS, Siemens
Analytical X-ray Instruments Inc., Madison, WI, 1989.
(14) Weiss, A.; Witte, H. Magnetochemie, Verlag Chemie: Weinheim,
Germany, 1973.
(15) H. Schumann, Z. Naturforsch., B 1995, 50, 1494.
(16) Davies, D. L.; Grist, A. J. Inorg. Chim. Acta 1994, 216, 217.

(Imido)vanadium Complexes
Inorganic Chemistry, Vol. 35, No. 7, 1996 1811
Table 2. Spectroscopic Data for (TMTAA)VdNR (2) and [(TMTAA)VdNR]SbF6 (4)
magn
com- suscepta
EPRb
UVd λmax, nm
(ꢀ, M-1 cm-1
plex µeff, µB g (A(51V), G)
NMRc δ, ppm
)
IRe ν, cm-1
2a
2b
2c
2d
1.77
1.81
1.81
1.76
1.993 (br),
1.978 (89.0)
1.991 (br),
1.975 (87.7)
1.984 (br),
1.978 (89.1)
1.987 (br),
1.978 (88.9)
269 (8500), 308 (8000),
377 (23000), 420 sh (8700)
265 (22000), 307 (12500),
376 (33500), 396 sh (21000)
268 (15000), 308 (13000),
376 (36000), 416 (7700)
268 (8700), 309 (8500), 374
(24500), 418 sh (5200)
751, 979, 1033, 1196, 1279, 1399,
1435, 1462, 1539, 1575
747, 842, 980, 1032, 1195, 1280,
1399, 1461, 1539
751, 840, 977, 1033, 1197, 1279,
1397, 1462, 1539, 1575
752, 840, 975, 1036, 1197, 1279,
1399, 1462, 1539, 2493,
2677, 2939
2e
4a
1.83
1.992 (br),
1.978 (88.4)
268 (13500), 307 (12500),
376 (35000), 420 (7000)
268 (19000), 308 (14000),
379 (33000), 439 sh (5200),
690 (2000)
752, 975, 1033, 1197, 1280, 1397,
1462, 1539
660, 757, 940, 992, 1198, 1277,
1311, 1398, 1433, 1462,
1537, 1565
1H: 7.33, 7.24, 7.18 (m, 8 H, C6H4),
6.33 (s, 2 H, CH), 3.23 (s, 3 H,
NCH3), 2.34 (s, 12 H, CH3)
51V: -554 (H1/2 ) 264 Hz)
4b
1H: 7.78, 7.71 (m, 4 H each, C6H4),
6.28 (s, 2 H, CH), 3.76 (s, 9 H,
t-C4H9), 2.75 (s, 12 H, CH3)
265 (21800), 308 (12200),
380 (32000), 437 sh (5000),
660 (1500)
659, 766, 1029, 1224, 1311, 1347,
1398, 1433, 1461, 1533
13C: 133.5 (CN), 129.97 (C6H4 C-3),
123.42 (C6H4 C-2), 121.00 (CH),
109.50 (C6H4 C-1), 44.31 (C(CH3)3),
29.2 (C(CH3)3), 23.49 (CH3)
51V: -573 (H1/2 ) 250 Hz)
4c
1H: 7.35, 7.13 (m, 8 H, C6H4), 6.67
(br m, 5 H, C6H5), 6.34 (s, 2 H, CH),
1.98 (s, 12 H, CH3)
269 (21000), 317 (19000),
378 (40000), 440 sh (6700),
695 (4000)
659, 760, 992, 1207, 1269, 1326,
1398, 1430, 1461, 1527, 1566
51V: -487 (H1/2 ) 310 Hz)
4d
1H: 7.7 to 7.5 (m, 8 H, C6H4), 6.20
(s, 2 H, CH), 2.48 (s, 12 H, CH3)
51V: -513 (H1/2 ) 970 Hz)
271 (13000), 322 (12000),
380 (20000), 444 (4500),
687 (2300)
270 (15000), 317 (13000),
378 (26500), 439 (5000),
685 (2700)
558, 660, 766, 846, 991, 1036, 1171,
1259, 1327, 1375, 1398, 1432,
1525, 1567, 2492, 2678, 2941
660, 763, 987, 1270, 1327, 1392,
1430, 1461, 1529, 1567
4e
1H: 7.26-7.20 (m, 8 H, C6H4), 6.34
(s, 2 H, CH), 3.47 (s, 6 H, N(CH3)2),
2.38 (s, 12 H, CH3)
51V: -536 (H1/2 ) 900 Hz)
a Measured at 294 K for powdered solids. b Signals observed as powdered solid (first value) and in CH2Cl2 solution at 294 K (second value). c In
1
CD2Cl2; H/13C NMR signals vs internal TMS; 51V NMR signals in CD3CN vs external 10% VOCl3 in C6D6. d In CH2Cl2. e In KBr.
Table 3. Electrochemical Data for the Oxidation of Complexes 2
to the Cations 4a
Scheme 3
complex
Eox, V
∆Ep1/2, mV
ipa/ipc
2a
2b
2c
2d
2e
5
0.30
0.30
0.34
0.31
0.31
0.35
108
195
141
75
97
90
0.98
0.95
0.88
1.00
1.00
0.96
a In CH2Cl2; irreversible reduction waves were observed for all
complexes in the range -1.94 to -1.99 V.
oxo vanadium (V) complex 6 (δ ) -368 ppm, H1/2 ) 90 Hz)15
has also been noted in a recent comparison of oxo and
iminoazavanadatranes.19b A rough correlation between the solid
state ESR g values for the complexes 2 and the δ 51V NMR
shift of the complexes 4 has been found as to be expected for
structurally similar systems differentiating only by the oxidation
state of the vanadium atom.20
The electronic absorption spectra of complexes 2 and 4 are
characteristic of tetramethyldibenzo[14]annulene complexes with
(19) (a) Kidd, R. G.; Goodfellow, R. J. The Transition Metals. In NMR
and the Periodic Table; Harris, R. K., Mann, B. E., Eds.; Academic
Press: London, 1978. (b) Plass, W.; Verkade, J. G. Inorg. Chem. 1993,
32, 3762.
(20) (a) Kazanskii, L. P.; Spitsyn, V. I. Dokl. Akad. Nauk. S.S.S.R. 1975,
223, 381; Dokl. Phys. Chem. 1975, 223, 721. (b) Correlation between
the ESR g values obtained for solid samples at 293 K and solution
51V NMR shifts except for 2b.
intense Soret-type bands around 270, 310 and 380 nm, which
are due to π f π* and charge transfer transitions.21 Ligand
field transitions may be assigned to absorptions at λmax ca. 420
nm (2) or at ca. 440 nm (2B2 f 2A1) and ca. 660 to 690 (2B f
2E) nm (4). These assignments are in agreement with the
reported data for (TMTAA)VdO (5, CH2Cl2; λmax (ꢀ) ) 419

1812 Inorganic Chemistry, Vol. 35, No. 7, 1996
Schumann
vanadium atom is square-pyramidal coordinated with the four
nitrogen atoms of the TMTAA macrocycle forming the basal
plane and the t-butylimido group at the apical site. The
vanadium (V) center is located 62 pm above the mean basal
plane with an average V-N (macrocycle) distance of 198 pm.
These data can be compared to the results obtained from the
structure determinations of unsolvated (TMTAA)VdO (5, VIV)
and [(TMTAA)VdO]SbF6 (6, VV):15 In these oxo vanadium
(IV/V) complexes, the vanadium atoms are located 68(3)/60-
(2) pm above the basal N4 plane with an average V-N
(macrocycle) distance of 202.6/198.1 pm. These differences
are attributed primarily to the size differences of their VIV/V
centers. Within the experimental error, the observed values for
the coordination of the TMTAA moiety to the vanadium center
in both VV complexes 4b and 6 are identical. The V-N(5)
distance within the imido group is 163.4(9) pm, which lies in
the range of other (imido)vanadium(V) complexes with a
coordination number of 5: V(NC4H9-t)(N(C4H9-t)Si(CH3)2N-
(C4H9-t)H)Cl2 (V-N ) 163.6(2) pm),26a {V(NCl)Cl2}2(µ-Cl)2
(V-N ) 164.2(9) pm),26b and V(NP(CH3)2C6H5)(P(CH3)2C6H5)-
Cl3 (V-N ) 175.4(5) pm).26c
Chemical Reactivity of 2. All obtained complexes are
extremely sensitive toward moisture hydrolyzing to [(TMTA-
A)VdO]n+ (5 or 6) as confirmed by analytical and spectroscopic
means. However, in solution or as solids under inert gas
atmosphere, all complexes are stable for months.
To compare the reactivity of the imido vanadium (IV)
complexes 2 with those of the related oxo vanadium (IV)
compound 5, several reactions have been performed (Scheme
4): Complexation of either the imido nitrogen atom by (CO)5Cr
(starting complex (c-C8H14)Cr(CO)5)27 or of the VN bond by
(C6H5)3P)2Pt (starting complex (C2H4)Pt(P(C6H5)3)2)28 has been
attempted. As described in the Experimental Section, no
reactions have been found and the starting complex 2a could
be recovered.
Figure 1. Molecular structure and atom-numbering scheme for
[(TMTAA)VdN(t-C4H9)]SbF6CH3CN (4b). Thermal ellipsoids are
drawn at the 50% probability level.
Table 4. Selected Bond Distances (pm) and Angles (deg) for
[(TMTAA)VdN(t-C4H9)]SbF6 (4b)
V-N(1)
198.4(6)
163.4(9)
133.9(9)
141.9(9)
111.7(31)
140.8(11)
137.0(11)
138.5(14)
138.6(10)
149.4(10)
184.3(8)
V-N(2)
197.7(6)
141.4(10)
134.8(9)
142.1(14)
139.7(10)
149.4(11)
139.5(11)
137.3(12)
140.8(10)
182.0(8)
184.3(6)
V-N(3)
N(1)-C(8)
N(2)-C(2)
N(3)-C(12)
C(1)-C(2)
C(2)-C(3)
C(4)-C(9)
C(6)-C(7)
C(8)-C(9)
Sb-F(1)
N(1)-C(10)
N(2)-C(9)
N(4)-C(16)
C(1)-C(l0A)
C(4)-C(5)
C(5)-C(6)
C(7)-C(8)
C(10)-C(11)
Sb-F(2)
Sb-F(3)
N(1)-V-N(2)
N(2)-V-N(3)
N(2)-V-N(lA)
N(2)-V-N(2A)
V-N(1)-C(8)
C(8)-N(1)-C(10)
V-N(2)-C(9)
V-N(3)-C(12)
81.3(2)
108.3(2)
87.3(2)
143.3(4)
102.1(4)
126.2(6)
102.2(4)
180.0(1)
N(1)-V-N(3)
N(1)-V-N(lA)
N(3)-V-N(lA)
N(3)-V-N(2A)
V-N(1)-C(10)
V-N(2)-C(2)
C(2)-N(2)-C(9)
108.4(2)
143.2(4)
108.4(2)
108.3(2)
131.7(5)
131.5(5)
126.3(6)
On the basis of recent studies on the reactivity of (TMTAA)-
Ti)O,29 [C5H5M()O)3]- (M ) Mo, W)30 and (RNH)(RNd)2V-
(OC2H5)2 (R ) t-Bu3Si)31 toward cycloaddition reactions, both
complexes 2a and 5 have been reacted with hexafluoracetone.
Within a short time, dark green precipitates have been formed
in both reaction solutions. On the basis of the obtained
analytical and spectroscopic data (Experimental Section and
Table 5), isolation affords the [2 + 2] cycloaddition products 7
and 8a in high yield. While not unexpected for 2a due to the
higher reactivity of MdNR over most MdO bonds,4a the
reactivity of 5 has been unexpected due to the high stability of
the VdO bond.
Reaction of 5 with hexafluorpropene oxide, SO3 and triflic
anhydride also yields the related ring-opening and cycloaddition
products 8b, 8c, and 8d as brownish-green microcystalline
solids. These compounds are stable at room temperature for
months without apparent decomposition and may be handled
for a short time under normal atmosphere. No reaction has been
(12 200), 740 (840) nm).15,21c,22 and [(TMTAA)VdO]SbF6 (6,
CH2Cl2; λmax (ꢀ) ) 444 (6000), 692 (4200) nm).15,22 The IR
spectra for 2 and 4 show the expected strong bands generally
observed for coordinated macrocyclic imine ligands, νCdC,CdN
absorptions due to the macrocyclic skeleton in the range 1400-
1470 cm-1 and νCdN at ca. 1530-1540 cm-1. Despite the
variation of the organic groups bonded to the imido nitrogen,
no specific assignment for the νVN absorption is possible.23 For
all SbF6 salts 4, the anion shows the expected strong absorption
at ca. 660 cm-1 [ν3(F2u)].24
Structure of 4b. Crystals of [(TMTAA)VdN(t-C4H9)]SbF6,
4b, suitable for single-crystal X-ray diffraction were grown by
layering an acetonitrile solution of 4b with ether. A perspective
view of the (imido)vanadium(V) complex 4b is shown in Figure
1. The bond distances and angles pertaining to the metal
coordination spheres are given in Table 4. The macrocyclic
framework in the [(TMTAA)VdN(t-C4H9)]+ cation is saddle-
shaped as observed and discussed for this type of ligand.25 The
(26) (a) Preuss, F.; Fuchslochner, E.; Sheldrick, W. S. Z. Naturforsch., B
1985, 40, 1040. (b) Stra¨hle, J.; Ba¨rnighausen, H. Z. Anorg. Allg. Chem.
1968, 359, 325. (c) Hills, A.; Hughes, D. L.; Leigh, G. J.; Prieto-
Alcon, R. J. Chem. Soc., Dalton Trans. 1993, 3609.
(27) Grevels, F.-W.; Skibbe, V. J. Chem. Soc., Chem. Commun. 1984, 681.
(28) (a) Nagel, U. Chem. Ber. 1982, 115, 1998. (b) Edelmann, F.; Spang,
C.; Roesky, H. W.; Jones, P. G. Z. Naturforsch., B 1988, 43, 517.
(29) (a) Housmekerides, C. E.; Pilato, R. S.; Geoffroy, G. L.; Rheingold,
A. L. J. Chem. Soc., Chem. Commun. 1991, 563. (b) Housmekerides,
C. E.; Ramage, D. L.; Kretz, C. M.; Shontz, J. T.; Pilato, R. S.;
Geoffroy, G. L.; Rheingold, A. L.; Haggerty, B. S. Inorg. Chem. 1992,
31, 4453.
(21) (a) Sakata, K.; Hashimoto, M.; Tagami, N.; Murakami, Y. Bull. Chem.
Soc. Jpn. 1980, 53, 2262. (b) Snopok, B. A.; Lampeka, Y. D. Opt.
Spectrosk. 1993, 75, 321; Opt. Spectrosc. (Engl. Transl.) 1993, 75,
188. (b) Sakata, K.; Yamaura, F.; Hashimoto, M. Synth. React. Inorg.
Met.-Org. Chem. 1990, 20, 1043.
(22) Lever, A. B. P. Inorganic Electronic Spectroscopy, 2nd ed.; Elsevier:
Amsterdam, 1984.
(23) Compare ref 4a, p 123. The in ref 19b discussed νVN range of ca.
1150-1280 cm-1 is dominated in both complexes 2 and 4 by IR
absorption of the coordinated TMTAA ligand.
(24) Weidlein, J.; Mu¨ller, U.; Dehnicke, K. Schwingungsfrequenzen I; G.
Thieme Verlag: Stuttgart, Germany, 1981.
(25) Review: Cotton, F. A.; Czuchajowska, J. Polyhedron 1990, 9, 2553.
(30) Rau, M. S.; Kretz, C. M.; Mercando, L. A.; Geoffroy, G. L. J. Am.
Chem. Soc. 1991, 113, 7420.
(31) de With, J.; Horton, A. D. Organometallics 1993, 12, 1493.

(Imido)vanadium Complexes
Inorganic Chemistry, Vol. 35, No. 7, 1996 1813
Table 5. Spectroscopic Characterization of the Cycloaddition Products 7 and 8
magn
com-
plex
suscepta
EPRb
UVc
max, nm
IRd
µeff, µB
g (A(51V), G)
λ
ν, cm-1
7
1.80
1.81
1.75
1.78
1.81
1.999 (br), 1.977 (87.4)
1.991 (br), 1.977 (87.2)
2.012 (br), 1.974 (90.5)
1.995 (br)
(310, 405, 590)
720, 750, 806, 840, 942, 1033, 1077, 1123, 1161,
1241, 1279, 1312, 1398, 1435, 1462, 1541, 1577
720, 750, 943, 1033, 1082, 1123, 1199, 1218,
1279, 1312, 1436, 1463, 1540, 1576, 1624
482, 719, 751, 941, 1030, 1162, 1278, 1312, 1328,
1399, 1434, 1462, 1539, 1574
437, 579, 664, 768, 910, 924, 1031, 1154, 1179,
1276, 1338, 1429, 1456, 1530, 1575
517, 637, 690, 770, 1031, 1163, 1263, 1345, 1430,
1460, 1519, 1548, 1577
8a
8b
8c
8d
265, 308, 375
(320, 410, 560)
270, 305, 377,
430 (350, 435)
(310, 420)
2.011 (br)
(320, 440)
a Measured at 294 K for powdered solids. b Signals observed as powdered solid (first value) and in CH2Cl2 solution at 294 K (second value). c In
CH2Cl2; data in parentheses obtained by reflection from solid samples. d In KBr, only strong bands stated.
Scheme 4
Scheme 5
comes from IR investigations: (a) the absence of the normally
very strong νVdO absorption at ca. 976 cm-1 for all complexes
7 and 8 together with (b) the presence of new strong absorptions
in the νCF region of 1140-1210 cm1 for the hexafluoroacetone
and hexfluoropropene oxide reaction products 7, 8a, and 8b;
(c) the observation of typical νSO bands at 579, 664, 713, 910,
924, 1179, and 1276 cm-1 for a η2-[O2]-SO4 coordination in
8c (for comparison, the νSO absorptions of (TMTAA)Ti(η2-
[O2]-SO4) have been assigned to 558, 671, 712, 912, 922, 1172,
and 1276 cm-1);29b,24 (d) absorptions assignable to the coordi-
nated CF3SO3 groups of 8d at 572, 1031 (νSO), and 1130-1230
cm-1 (νCF).32 For the related (TMTAA)Ti complexes formed
upon reaction of the coordinated TidO moiety with hexafluor-
propene oxide, phthalic anhydride and SO3, their structures have
also been confirmed by single-crystal X-ray structure determi-
nation.29 Several attempts to obtain crystals of complexes 7
and 8 suitable for single-crystal X-ray diffraction studies by
different methods have been so far unsuccessful.
Acknowledgment. This work was supported by the Fonds
der Chemischen Industrie (Liebig Fellowship 1991-1992), the
Bundesministerium fu¨r Forschung und Technologie (Heinz-
Meyer-Leibnitz Prize 1991), Bayer AG, Degussa AG, BASF
AG, and Gesellschaft fu¨r Elektrometallurgie. I am especially
grateful to Dr. H. Bo¨gge, Dr. R. Rolfing, and A. Amartage for
measuring and solving the X-ray structure determination of 4b
and the Fakulta¨t fu¨r Chemie der Universita¨t Bielefeld for the
use of space and equipment.
observed with the less electrophilic agents phthalic anhydride,
SO2, and CS2, thereby confirming the expected reduced reactiv-
ity of 5 in comparison to (TMTAA)TidO.29 The imido
vanadium complex 2a also reacts with these agents but due to
the extreme moisture sensitivity, workup of these reactions
affords inseparable product mixtures.
Supporting Information Available: Tables of data collection and
refinement details, atom positional and thermal parameters, and bond
distances and angles, and a view of the unit cell content (10 pages).
Ordering information is given on any current masthead page.
Magnetic measurements and EPR spectra confirm for both 7
and 8a-d the presence of a single VIV center coordinated to a
TMTAA unit as evident from IR and UV/vis data. Best
evidence for the proposed structures of these reaction products
IC9508381
(32) Nakamoto, K. Infared and Raman Spectra of Inorganic and Coordina-
tion Compounds, 4th. ed.; Wiley-Interscience: New York, 1986.