Aryldiazene, Aryldiazenido, and Hydrazine Complexes of Manganese. Preparation, Characterization, and X-ray Crystal Structures of [Mn(CO)3(4-CH3C6H 4N=NH){PPh(OEt)2}2]BF4 and [Mn(CO)3(NH2NH2){PPh(OEt)2} 2]BPh4 Derivatives

Article abstract of DOI:10.1021/ic9608612

Aryldiazene complexes [Mn(CO)₃(ArN=NH)P₂]BF₄ (1, 2) and [{Mn(CO)₃P₂}₂(μ-HN=NArArN=NH)](BF ₄)₂ (3, 4) [P = PPh(OEt)₂, PPh₂OEt; Ar = C₆H₅, 2-CH₃C₆H₄, 4-CH₃C₆H₄, 4-CH₃OC₆H₄; ArAr = 4,4′-C₆H₄C₆H₄, 4,4′-(2-CH₃)C₆H₃C₆H ₃(2-CH₃), 4,4′-C₆H₄CH₂C₆H₄] were prepared by reacting hydride species MnH(CO)₃P₂ with the appropriate aryldiazonium cations in CH₂Cl₂ or acetone solutions at -80 °C. The compounds were characterized by IR, ¹H and ³¹P NMR spectra (with ¹⁵N isotopic substitution), and a single-crystal X-ray structure determination. The complex [Mn(CO)₃(4-CH₃C₆H ₄N=NH){PPh(OEt)₂}₂]BF₄ (1c) crystallizes in the space group C2/c with a = 31.857(5) A?, b = 11.119(2) A?, c = 22.414(3) A?, β = 97.82(1)°, and Z = 8. Treatment of aryldiazene compounds 1-4 with NEt₃ gave the pentacoordinate aryldiazenido [Mn(CO)₂(ArN₂)P₂] (5, 6) and [{Mn(CO)₂P₂}₂(μ-N₂-ArArN ₂)] (7, 8) [P = PPh(OEt)₂, PPh₂OEt; Ar = C₆H₅,4-CH₃C₆H₄; ArAr = 4,4′-C₆H₄C₆H₄, 4,4′-(2-CH₃)C₆H₃C₆H ₃-(2-CH₃)] derivatives. Protonation reactions of these aryldiazenido complexes 5-8 with HCl afforded the aryldiazene [MnCl(CO)₂(ArN=NH)P₂] (9) and [{MnCl(CO)₂P₂}₂(μ-HN=NArArN=NH)] (10) derivatives. Hydrazine complexes [Mn(CO)₃(RNHNH₂)P₂]BPh₄ (11, 12) [P = PPh(OEt)₂, PPh₂OEt; R = H, CH₃, C₆H₅, 4-NO₂C₆H₄] were prepared by allowing hydride species MnH(CO)₃P₂ to react first with triflic acid and then with the appropriate hydrazine. Their characterization by IR, ¹H and ³¹P NMR spectra, and an X-ray crystal structure determination is reported. The compound [Mn(CO)₃(NH₂NH₂){PPh(OEt)₂} ₂]BPh₄ (11a) crystallizes in the space group P1 with a = 13.772(3) A?, b = 14.951(4) A?, c = 13.319(3) A?, α = 104.47(1)°, β = 100.32(1)°, γ = 111.08(1)°, and Z = 2. Oxidation reactions of hydrazine compounds 11 and 12 with Pb(OAc)₄ at -40 °C gave stable aryldiazene [Mn(CO)₃(RN=NH)P₂]BPh₄ and thermally unstable (upon reaching -40 °C) diazene [Mn(CO)₃(HN=NH)P₂]-BPh₄ derivatives.

Full text of DOI:10.1021/ic9608612

1296
Inorg. Chem. 1997, 36, 1296-1305
Aryldiazene, Aryldiazenido, and Hydrazine Complexes of Manganese. Preparation,
Characterization, and X-ray Crystal Structures of
[Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4 and [Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4
Derivatives
Gabriele Albertin,*,† Stefano Antoniutti,† Alessia Bacchi,‡ Emilio Bordignon,†
Fabio Busatto,† and Giancarlo Pelizzi‡
Dipartimento di Chimica, Universita` di Venezia, Dorsoduro 2137, 30123 Venezia, Italy, and
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Centro CNR di
Strutturistica Diffrattometrica, Universita` di Parma, Viale delle Scienze, 43100 Parma, Italy
ReceiVed July 19, 1996X
Aryldiazene complexes [Mn(CO)3(ArNdNH)P2]BF4 (1, 2) and [{Mn(CO)3P2}2(µ-HNdNArArNdNH)](BF4)2 (3,
4) [P ) PPh(OEt)2, PPh2OEt; Ar ) C6H5, 2-CH3C6H4, 4-CH3C6H4, 4-CH3OC6H4; ArAr ) 4,4′-C6H4C6H4, 4,4′-
(2-CH3)C6H3C6H3(2-CH3), 4,4′-C6H4CH2C6H4] were prepared by reacting hydride species MnH(CO)3P2 with the
appropriate aryldiazonium cations in CH2Cl2 or acetone solutions at -80 °C. The compounds were characterized
by IR, 1H and 31P NMR spectra (with 15N isotopic substitution), and a single-crystal X-ray structure determination.
The complex [Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4 (1c) crystallizes in the space group C2/c with a )
31.857(5) Å, b ) 11.119(2) Å, c ) 22.414(3) Å, â ) 97.82(1)°, and Z ) 8. Treatment of aryldiazene compounds
1-4 with NEt3 gave the pentacoordinate aryldiazenido [Mn(CO)2(ArN2)P2] (5, 6) and [{Mn(CO)2P2}2(µ-N2-
ArArN2)] (7, 8) [P ) PPh(OEt)2, PPh2OEt; Ar ) C6H5, 4-CH3C6H4; ArAr ) 4,4′-C6H4C6H4, 4,4′-(2-CH3)C6H3C6H3-
(2-CH3)] derivatives. Protonation reactions of these aryldiazenido complexes 5-8 with HCl afforded the aryldiazene
[MnCl(CO)2(ArNdNH)P2] (9) and [{MnCl(CO)2P2}2(µ-HNdNArArNdNH)] (10) derivatives. Hydrazine
complexes [Mn(CO)3(RNHNH2)P2]BPh4 (11, 12) [P ) PPh(OEt)2, PPh2OEt; R ) H, CH3, C6H5, 4-NO2C6H4]
were prepared by allowing hydride species MnH(CO)3P2 to react first with triflic acid and then with the appropriate
1
hydrazine. Their characterization by IR, H and 31P NMR spectra, and an X-ray crystal structure determination
is reported. The compound [Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4 (11a) crystallizes in the space group P1h
with a ) 13.772(3) Å, b ) 14.951(4) Å, c ) 13.319(3) Å, R ) 104.47(1)°, â ) 100.32(1)°, γ ) 111.08(1)°, and
Z ) 2. Oxidation reactions of hydrazine compounds 11 and 12 with Pb(OAc)4 at -40 °C gave stable aryldiazene
[Mn(CO)3(RNdNH)P2]BPh4 and thermally unstable (upon reaching -40 °C) diazene [Mn(CO)3(HNdNH)P2]-
BPh4 derivatives.
Introduction
derivatives toward oxidation, reduction, protonation, and depro-
tonation reactions.
There is current interest in the chemistry of aryldiazo,
aryldiazene, and hydrazine complexes1-3 due to different factors
including the possible relevance in the dinitrogen fixation
process, the influence that the central metal and the ancillary
ligand may have in determining the different coordination modes
of the “diazo” groups, and the potential properties of these
Our interest in this field has been mainly devoted to metal
complexes of the iron family, and a number of studies on the
synthesis and reactivity of both mono and bis forms of
aryldiazene and aryldiazenido derivatives of the type [MH-
(ArNdNH)P4]+, [M(ArNdNH)2P4]2+, [M(ArN2)P4]+, and
[M(ArN2)2P3]2+ (M ) Fe, Ru, Os; P ) phosphite) have been
recently reported.4 These results prompted us to extend our
studies to include other metal complexes such as those of
manganese which result to be, as Mn(I), isoelectronic with the
iron(II) family and whose “diazo” and hydrazine chemistry is
relatively little studied5-12 as compared to other transition
metals.1 A perusal of the literature showed, in fact, that while
some stable and well-characterized aryldiazenido complexes,
† Dipartimento di Chimica, Universita` di Venezia.
‡ Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica,
Chimica Fisica, Universita` di Parma.
X Abstract published in AdVance ACS Abstracts, January 15, 1997.
(1) (a) Sutton, D. Chem. ReV. 1993, 93, 995. (b) Kisch, H.; Holzmeier,
H. AdV. Organomet. Chem. 1992, 34, 67. (c) Johnson, B. F. G.;
Haymore, B. L.; Dilworth, J. R. In ComprehensiVe Coordination
Chemistry; Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.;
Pergamon Press: Oxford, England, 1987; Vol. 2, p 130.
(4) (a) Albertin, G.; Antoniutti, S.; Lanfranchi, M.; Pelizzi, G.; Bordignon,
E. Inorg. Chem. 1986, 25, 950. (b) Albertin, G.; Antoniutti, S.; Pelizzi,
G.; Vitali, F.; Bordignon, E. J. Am. Chem. Soc. 1986, 108, 6627. (c)
Albertin, G.; Antoniutti, S.; Bordignon, E. Inorg. Chem. 1987, 26,
3416. (d) Albertin, G.; Antoniutti, S.; Pelizzi, G.; Vitali, F.; Bordignon,
E. Inorg. Chem. 1988, 27, 829. (e) Albertin, G.; Antoniutti, S.;
Bordignon, E. J. Am. Chem. Soc. 1989, 111, 2072. (f) Amendola, P.;
Antoniutti, S.; Albertin, G.; Bordignon, E. Inorg. Chem. 1990, 29,
318.
(5) Barrientos-Penna, C. F.; Einstein, F. W. B.; Sutton, D.; Willis, A. C.
Inorg. Chem. 1980, 19, 2740.
(6) (a) Ferguson, G.; Laws, W. J.; Parvez, M.; Puddephatt, R. J.
Organometallics 1983, 2, 276. (b) Turney, T. W. Inorg. Chim. Acta
1982, 64, L141.
(2) (a) Cusanelli, A.; Sutton, D. Organometallics 1995, 14, 4651. (b) Kim,
G. C.-Y.; Batchelor, R. J.; Yan, X.; Einstein, F. W. B.; Sutton, D.
Inorg. Chem. 1995, 34, 6163. (c) Kettler, P. B.; Chang, Y.-D.; Zubieta,
J. Inorg. Chem. 1994, 33, 5864. (d) Richards, T. C.; Bard, A. J.;
Cusanelli, A.; Sutton, D. Organometallics 1994, 13, 757.
(3) (a) Molinak, S. M.; Demadis, K. D.; Coucouvanis, D. J. Am. Chem.
Soc. 1995, 117, 3126. (b) Cheng, T.-Y.; Ponce, A.; Rheingold, A. L.;
Hillhouse, G. L. Angew. Chem., Int. Ed. Engl. 1994, 33, 657. (c) Smith,
M. R., III; Cheng, T.-Y.; Hillhouse, G. L. J. Am. Chem. Soc. 1993,
115, 8638. (d) Sellmann, D.; Ka¨ppler, J.; Moll, M.; Knoch, F. Inorg.
Chem. 1993, 32, 960. (e) Glassman, T. E.; Vale, M. G.; Schrock, R.
R. J. Am. Chem. Soc. 1992, 114, 8098. (f) Kawano, M.; Hoshino, C.;
Matsumoto, K. Inorg. Chem. 1992, 31, 5158.
S0020-1669(96)00861-0 CCC: $14.00 © 1997 American Chemical Society

Aryldiazene Complexes of Manganese
Inorganic Chemistry, Vol. 36, No. 7, 1997 1297
(99% enriched, CIL) and the appropriate amine. Alternatively, the
[C6H515NtN]BF4 salt was obtained from NaNO2 and C6H515NH2. The
hydrazines C6H5NHNH2, CH3NHNH2, 4-NO2C6H4NHNH2, and (CH3)2-
NNH2 were Aldrich products used as received. Hydrazine NH2NH2
was prepared by decomposition of hydrazine cyanurate (Fluka) fol-
lowing the reported method.16 Mn2(CO)10 (Aldrich), HBF4‚Et2O (54%
solution), and triflic acid (Aldrich) were used as purchased. Triethy-
lamine was dried with CaH2 and distilled before use. Other reagents
were purchased from commercial sources in the highest available purity
and used as received. Infrared spectra were recorded on a Digilab Bio-
Rad FTS-40 spectrophotometer. NMR spectra (1H, 13C, 31P) were
obtained on a Bruker AC200 spectrometer at temperatures varying
between -90 and +30 °C, unless otherwise noted. 1H and 13C spectra
are referred to internal tetramethylsilane, while 31P{1H} chemical shifts
are reported with respect to 85% H3PO4, with downfield shifts
considered positive. The conductivities of 10-3 M solutions of the
complexes in CH3NO2 at 25 °C were measured with a Radiometer CDM
83 instrument.
Chart 1
[Mn(η5-RC5H4)Mn(CO)2(o-N2C6H4R′)]BF4 (R ) CH3, H; R′
) CF3, F, H),5 Mn(CO)n(N2Ph)(PPh3)4-n (n ) 2, 3),8,10 MnX(N2-
Ph)2(PPh3)2,10 [Mn(CO)(N2Ph)2(PPh3)2]PF6,10 and [(PhNN)Mn-
(CO)4]2,12 have been described, very few examples of both
diazene and hydrazine complexes have been reported. Apart
from stable dimeric complexes with a diazene bridge of the type
Synthesis of Complexes. The hydride MnH(CO)5 was prepared
from Mn2(CO)10 according to the procedure previously reported.17 The
hydride species MnH(CO)3P2, MnH(CO)2P3, and MnH(CO)P4 [P )
PPh(OEt)2 and PPh2OEt] were instead prepared by substitution of the
carbonyl ligands in the MnH(CO)5 derivative following a method that
will be reported in a forthcoming paper.18 The MnH(CO)3(dppe)
complex was obtained as previously described.19
7
η5-C5H5Mn(CO)2HNdNHCr(CO)5 and [η5-C5H5Mn(CO)2]2-
(µ-C6H5NdNH)9 and the related unstable mononuclear ones,
only two brief reports, one on aryldiazene10 and the other on
hydrazine13 derivatives of manganese, appear in the literature.
It seems therefore desirable to begin a systematic study of the
“diazo” chemistry of this metal, and so in this paper we report
the synthesis and characterization of new aryldiazene, aryldia-
zenido, and hydrazine complexes of manganese stabilized by
phosphonite PPh(OEt)2 and phosphinite PPh2OEt ligands. These
studies include the use of the bis(diazonium) cations [N2-
ArArN2]2+ of the types A-C (Chart 1), which gave dinuclear
complexes, as well as the first X-ray crystal structure determina-
tions of an aryldiazene and a hydrazine derivative of manganese.
[Mn(CO)3(ArNdNH)P2]BF4 (1, 2) [Ar ) C6H5 (a), 4-CH3C6H4
(b), 2-CH3C6H4 (c); P ) PPh(OEt)2 (1), PPh2OEt (2)]. A solid
sample of the appropriate hydride MnH(CO)3P2 (1 mmol) and solid
aryldiazonium tetrafluoroborate [ArN2]BF4 (1 mmol) were mixed
together in a 25-mL three-necked round-bottomed flask and cooled to
about -80 °C. Dichloromethane (10 mL) was slowly added, and the
resulting mixture was brought to room temperature and stirred for 3 h.
Removal of the solvent under reduced pressure gave an oil which was
treated with 2 mL of ethanol. By cooling of the resulting solution to
-25 °C yellow microcrystals slowly separated out which were collected
and crystallized from ethanol; yield g80%. Anal. Calcd for 1a: C,
47.83; H, 4.98; N, 3.85. Found: C, 48.04; H, 4.91; N, 3.71. Mp: 87
°C. ΛM ) 87.3 Ω-1 mol-1 cm2. Calcd for 1b: C, 48.54; H, 5.16; N,
3.77. Found: C, 48.42; H, 5.31; N, 3.82. Mp: 97 °C. ΛM ) 99.5
Ω-1 mol-1 cm2. Calcd for 1c: C, 48.54; H, 5.16; N, 3.77. Found: C,
48.76; H, 5.06; N, 3.68. Mp: 123 °C. ΛM ) 92.8 Ω-1 mol-1 cm2.
Calcd for 2b: C, 56.60; H, 4.75; N, 3.47. Found: C, 56.57; H, 4.88;
N, 3.56. Mp: 131 °C. ΛM ) 85.6 Ω-1 mol-1 cm2. Calcd for 2c: C,
56.60; H, 4.75; N, 3.47. Found: C, 56.77; H, 4.71; N, 3.52. Mp:
137 °C. ΛM ) 91.0 Ω-1 mol-1 cm2.
Experimental Section
All synthetic work was carried out under an inert atmosphere using
standard Schlenk techniques or a Vacuum Atmosphere dry box. Once
isolated, the complexes were found to be relatively stable in air but
were stored under an inert atmosphere at -25 °C. All solvents were
dried over appropriate drying agents, degassed on a vacuum line, and
distilled into vacuumtight storage flasks. The phosphites PPh(OEt)2
and PPh2OEt were prepared by the method of Rabinowitz and Pellon.14
Diazonium salts were obtained in the usual way.15 The related
bis(diazonium) [N2ArArN2](BF4)2 [ArAr ) 4,4′-C6H4C6H4, A; 4,4′-
(2-CH3)C6H3C6H3(2-CH3), B; 4,4′-C6H4CH2C6H4, C] salts (Chart 1)
were prepared by treating the amine precursors H2NArArNH2 with
NaNO2 as described in the literature for the common mono(diazonium)
salts.15 The labeled diazonium tetrafluoroborates [C6H5Nt15N]BF4 and
[4,4′-15NtNC6H4C6H4Nt15N](BF4)2 were prepared from Na15NO2
[Mn(CO)3(4-CH3OC6H4NdNH)P2]BPh4 (1d, 2d). These com-
plexes were prepared like the related 1 and 2 but using an excess of
NaBPh4 (2 mmol, 0.68 g) in ethanol (5 mL) as the precipitating agent;
yield g80%. Anal. Calcd for 1d: C, 65.46; H, 5.90; N, 2.83.
Found: C, 65.84; H, 5.98; N, 2.89. ΛM
) 51.3 Ω-1 mol-1 cm2. Calcd
for 2d: C, 70.60; H, 5.54; N, 2.66. Found: C, 70.78; H, 5.67; N,
2.75. ΛM
) 53.8 Ω-1 mol-1 cm2.
[Mn(CO)3(C6H5Nd15NH){PPh(OEt)2}2]BF4 (1a1) and [Mn(CO)3-
(C6H515NdNH){PPh(OEt)2}2]BF4 (1a2). These complexes were
prepared like the related 1a using the labeled [C6H5Nt15N]BF4 and
[C6H515NtN]BF4 aryldiazonium salts, respectively; yield g80%. Anal.
Calcd for 1a1: C, 47.76; H, 4.97; N, 3.98. Found: C, 47.81; H, 4.89;
N, 3.86. Mp: 87 °C. ΛM ) 82.8 Ω-1 mol-1 cm2. Calcd for 1a2: C,
47.76; H, 4.97; N, 3.98. Found: C, 47.68; H, 4.84; N, 3.80. Mp: 87
°C. ΛM ) 92.0 Ω-1 mol-1 cm2.
(7) (a) Sellmann, D.; Gerlach, R.; Jo¨dden, K. J. Organomet. Chem. 1979,
178, 433. (b) Sellmann, D.; Jo¨dden, K. Angew. Chem., Int. Ed. Engl.
1977, 16, 464.
(8) Abel, E. W.; Burton, C. A. J. Organomet. Chem. 1979, 170, 229.
(9) (a) Sellmann, D.; Weiss, W. J. Organomet. Chem. 1978, 160, 183.
(b) Sellmann, D.; Weiss, W. Angew. Chem., Int. Ed. Engl. 1977, 16,
880.
(10) Haymore, B. L. J. Organomet. Chem. 1977, 137, C11.
(11) (a) Herrmann, W. A.; Ziegler, M. L.; Weidenhammer, K. Angew.
Chem., Int. Ed. Engl. 1976, 15, 368. (b) Herrmann, W. A.; Ziegler,
M. L.; Weidenhammer, K.; Biersack, H.; Mayer, K. K.; Minard, R.
D. Ibid. 1976, 15, 164. (c) Herrmann, W. A. J. Organomet. Chem.
1975, 97, 1.
(12) (a) Churchill, M. R.; Lin, K.-K. G. Inorg. Chem. 1975, 14, 1133. (b)
Abel, E. W.; Burton, C. A.; Churchill, M. R.; Lin, K.-K. G. J. Chem.
Soc., Chem. Commun. 1974, 268.
[{Mn(CO)3P2}2(µ-HNdNArArNdNH)](BF4)2 (3, 4) [P ) PPh-
(OEt)2 (3), PPh2OEt (4); ArAr ) 4,4′-C6H4C6H4 (a), 4,4′-(2-CH3)-
C6H3C6H3(2-CH3) (c)]. A 25-mL three-necked round-bottomed flask
was charged with a solid sample of the appropriate hydride MH(CO)3P2
(1 mmol) and of the bis(diazonium) salt [N2ArArN2](BF4)2 (0.5 mmol)
and cooled to about -80 °C. Acetone (10 mL) was added, and the
resulting mixture was brought to room temperature and stirred for 6 h.
(13) Sellmann, D. Z. Naturforsch. 1970, 25b, 890.
(14) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623.
(15) Vogel, A. I. Practical Organic Chemistry, 3rd ed.; Longmans, Green
and Co.: New York, 1956.
(16) Nachbaur, E.; Leiseder, G. Monatsh. Chem. 1971, 102, 1718.
(17) King, R. B.; Stone, F. G. A. Inorg. Synth. 1963, 7, 198.
(18) Albertin, G.; Antoniutti, S.; Bordignon, E. Manuscript in preparation.
(19) Booth, B. L.; Haszeldine, R. N. J. Chem. Soc. A 1966, 157.

1298 Inorganic Chemistry, Vol. 36, No. 7, 1997
Albertin et al.
The solvent was removed under reduced pressure giving an oil which
was triturated with 5 mL of ethanol. A red solid slowly separated out
which was filtered and crystallized from ethanol; yield g90%. Anal.
Calcd for 3a: C, 47.89; H, 4.85; N, 3.85. Found: C, 47.93; H, 4.94;
N, 3.79. Mp: 165 °C. ΛM ) 175 Ω-1 mol-1 cm2. Calcd for 3c: C,
48.61; H, 5.03; N, 3.78. Found: C, 48.25; H, 5.17; N, 3.71. Mp:
168 °C. ΛM ) 182 Ω-1 mol-1 cm2. Calcd for 4a: C, 56.16; H, 4.46;
C6H4Nt15N) (7a1) complex with HCl in a 1:2 molar ratio; yield g85%.
Anal. Calcd: C, 51.82; H, 5.44; N, 4.47. Found: C, 52.12; H, 5.39;
N, 4.35. Mp: 111 °C.
[Mn(CO)3(RNHNH2)P2]BPh4 (11, 12) [R ) H (a), CH3 (b); P )
PPh(OEt)2 (11), PPh2OEt (12)]. A solution of the appropriate hydride
MnH(CO)3P2 (1 mmol) in 10 mL of CH2Cl2 was cooled to -80 °C
and treated with an equimolar amount of CF3SO3H (1 mmol, 88.5 µL).
The reaction mixture was brought to room temperature, stirred for about
2 h, and cooled again to -80 °C. An excess of the appropriate
hydrazine (3 mmol) was added to the solution which was brought to
20 °C and stirred for 12-14 h. The solvent was removed under reduced
pressure giving an oil which was treated with 5 mL of ethanol. The
addition of an excess of NaBPh4 (2 mmol, 0.68 g) in 2 mL of ethanol
caused the precipitation of a yellow solid, which was filtered out and
crystallized from CH2Cl2 (2 mL)/ethanol (8 mL); yield g80%. Anal.
Calcd for 11a: C, 63.67; H, 6.14; N, 3.16. Found: C, 63.59; H, 6.21;
N, 3.23. Mp: 119 °C. ΛM ) 65.0 Ω-1 mol-1 cm2. Calcd for 11b:
C, 64.01; H, 6.27; N, 3.11. Found: C, 64.38; H, 6.22; N, 3.17. Mp:
108 °C. ΛM ) 60.7 Ω-1 mol-1 cm2. Calcd for 12a: C, 69.48; H,
5.72; N, 2.95. Found: C, 69.67; H, 5.68; N, 3.05. Mp: 122 °C. ΛM
) 59.2 Ω-1 mol-1 cm2. Calcd for 12b: C, 69.72; H, 5.85; N, 2.90.
Found: C, 69.51; H, 5.83; N, 2.97. Mp: 121 °C. ΛM ) 61.4 Ω-1
mol-1 cm2.
[Mn(CO)3(RNHNH2)P2]BPh4 (11, 12) [R ) C6H5 (c), 4-NO2C6H4
(d); P ) PPh(OEt)2 (11), PPh2OEt (12)]. These complexes were
prepared like the related hydrazine derivatives by treating MnH(CO)3P2
(1 mmol) with an equivalent amount of CF3SO3H (1 mmol, 88.5 µL)
and then with a slight excess (1.1 mmol) of the appropriate hydrazine.
The resulting solution was stirred for 3 h giving, after workup, green
microcrystals of the product in about 80% yield. Anal. Calcd for
11c: C, 66.12; H, 6.07; N, 2.91. Found: C, 66.39; H, 5.96; N, 2.85.
Mp: 123 °C. ΛM ) 62.2 Ω-1 mol-1 cm2. Calcd for 11d: C, 63.11;
H, 5.80; N, 4.17. Found: C, 62.90; H, 5.72; N, 4.22. Mp: 95 °C. ΛM
) 59.8 Ω-1 mol-1 cm2. Calcd for 12c: C, 71.35; H, 5.69; N, 2.73.
Found: C, 71.55; H, 5.72; N, 2.78. Mp: 125 °C. ΛM ) 63.7 Ω-1
mol-1 cm2. Calcd for 12d: C, 68.36; H, 5.36; N, 3.92. Found: C,
68.22; H, 5.47; N, 3.84. Mp: 98 °C. ΛM ) 64.1 Ω-1 mol-1 cm2.
[Mn(CO)3{(CH3)2NNH2}{PPh(OEt)2}2]BPh4 (11e). This complex
was prepared like the related 11 and 12 using an excess of the hydrazine
(CH3)2NNH2 with respect to the starting MnH(CO)3P2 compound (5:1
ratio) and stirring the reaction mixture for 24 h; yield g80%. Anal.
Calcd: C, 64.34; H, 6.39; N, 3.06. Found: C, 64.02; H, 6.51; N, 3.11.
Mp: 99 °C. ΛM ) 58.9 Ω-1 mol-1 cm2.
Oxidation Reactions. The oxidation of the hydrazine complexes
11 and 12 was carried out with Pb(OAc)4 under an inert atmosphere in
CH2Cl2 at -40 °C. In a typical experiment a CH2Cl2 solution (10 mL)
of the appropriate hydrazine complex (0.2 mmol) was placed in a three-
necked 25 mL flask fitted with a solid-addition side arm containing
Pb(OAc)4 (0.21 mmol, 93 mg). The system was cooled to -40 °C,
and the Pb(OAc)4 was added portionwise to the cold stirred solution
in about 20-30 min. The solution was filtered and the solvent removed
under vacuum to give an orange oil which was treated with 5 mL of
ethanol. By vigorous stirring of the resulting solution, an orange solid
separated out which was filtered out and dried under vacuum; yield
g80%.
N, 3.54. Found: C, 55.87; H, 4.38; N, 3.46. Mp: 156 °C. ΛM
)
178 Ω-1 mol-1 cm2. Calcd for 4c: C, 56.67; H, 4.63; N, 3.48.
Found: C, 56.51; H, 4.70; N, 3.58. Mp: 157 °C. ΛM ) 191 Ω-1
mol-1 cm2.
[Mn(CO)3{PPh(OEt)2}2]2(µ-4,4′-HNdNC6H4CH2C6H4NdNH)]-
(BPh4)2 (3e). This complex was prepared like the related 3 but using
an excess of NaBPh4 in ethanol as the precipitating agent; yield g90%.
Anal. Calcd: C, 66.47; H, 5.84; N, 2.90. Found: C, 66.60; H, 5.96;
N, 2.81. ΛM ) 121 Ω-1 mol-1 cm2.
[{Mn(CO)3(PPh(OEt)2)2}2(µ-4,4′-H15NdNC6H4C6H4Nd15NH)]-
(BF4)2 (3a1) and [{Mn(CO)3(PPh2OEt)2}2(µ-4,4′-H15NdNC6H4-
C6H4Nd15NH)] (BF4)2 (4a1). These complexes were prepared like the
related 3a and 4a using the labeled [4,4′-15NtNC6H4C6H4Nt15N](BF4)2
bis(diazonium) salt; yield g90%. Anal. Calcd for 3a1: C, 47.82; H,
4.84; N, 3.98. Found: C, 47.75; H, 4.72; N, 3.87. Mp: 165 °C. ΛM
) 184 Ω-1 mol-1 cm2. Calcd for 4a1: C, 56.08; H, 4.45; N, 3.66.
Found: C, 56.24; H, 4.53; N, 3.59. Mp: 155 °C. ΛM ) 172 Ω-1
mol-1 cm2.
Mn(CO)2(ArN2)P2 (5, 6) [Ar ) C6H5 (a), 4-CH3C6H4 (b); P )
PPh(OEt)2, (5), PPh2OEt (6)]. An excess of triethylamine (5 mmol,
0.70 mL) was added to a solution of the appropriate diazene complex
[Mn(CO)3(ArNdNH)P2]BF4 (1 mmol) in 10 mL of CH2Cl2, and the
reaction mixture was stirred for 2 h. The solvent was removed under
reduced pressure giving a red oil which was treated with 2 mL of
ethanol. The resulting solution was cooled to 0 °C and vigorously
stirred until an orange solid separated out which was filtered out and
crystallized from ethanol; yield g80%. Anal. Calcd for 5a: C, 54.91;
H, 5.76; N, 4.57. Found: C, 54.53; H, 5.65; N, 4.49. Calcd for 5b:
C, 55.60; H, 5.95; N, 4.47. Found: C, 55.78; H, 5.87; N, 4.55. Mp:
61 °C. Calcd for 6b: C, 64.35; H, 5.40; N, 4.06. Found: C, 64.57;
H, 5.49; N, 4.10. Mp: 123 °C.
Mn(CO)2(C6H5Nt15N){PPh(OEt)2}2 (5a1). This compound was
prepared like 5a starting from the labeled complex [Mn(CO)3-
(C6H5Nd15NH){PPh(OEt)2}2]BF4 (1a1); yield g80%. Anal. Calcd:
C, 54.82; H, 5.75; N, 4.73. Found: C, 54.58; H, 5.83; N, 4.80.
[Mn(CO)2P2]2(µ-N2ArArN2) (7, 8) [ArAr ) 4,4′-C6H4C6H4, (a),
4,4′-(2-CH3)C6H3C6H3(2-CH3) (c); P ) PPh(OEt)2 (7) PPh2OEt (8)].
These binuclear complexes were prepared like the related mononuclear
5 and 6 by deprotonation with triethylamine of the corresponding bis-
(diazene) [{Mn(CO)3P2}2(µ-HNdNArArNdNH)](BF4)2 (3, 4) deriva-
tives in CH2Cl2; yield g90%. Anal. Calcd for 7a: C, 55.00; H, 5.60;
N, 4.58. Found: C, 54.82; H, 5.48; N, 4.67. Mp: 132 °C. Calcd for
7c: C, 55.69; H, 5.80; N, 4.48. Found: C, 55.86; H, 5.86; N, 4.43.
Mp: 100 °C. Calcd for 8c: C, 64.45; H, 5.26; N, 4.06. Found: C,
64.22; H, 5.12; N, 4.13. Mp: 143 °C.
[Mn(CO)2{PPh(OEt)2}2]2(µ-4,4′-15NtNC6H4C6H4Nt15N) (7a1).
This complex was prepared like 7a starting from the labeled [{Mn-
(CO)3(PPh(OEt)2)2}2(µ-4,4′-H15NdNC6H4-C6H4Nd15NH)](BF4)2 (3a1)-
derivative; yield g90%. Anal. Calcd: C, 54.91; H, 5.60; N, 4.74.
Found: C, 54.78; H, 5.52; N, 4.81. Mp: 132 °C.
[MnCl(CO)2(4-CH3C6H4NdNH){PPh(OEt)2}2] (9b). A solution
of Mn(CO)2(4-CH3C6H4N2)[PPh(OEt)2]2 (5b) (0.3 mmol, 0.19 g) in
10 mL of CH2Cl2 was cooled to -80 °C, and HCl in solution of diethyl
ether (0.3 mmol, 3 mL of a 0.1 M solution) was added. [The solution
of HCl was prepared by treating (CH3)3SiCl in diethyl ether with an
equimolar amount of CH3OH.] The reaction mixture was brought to
room temperature and stirred for 2 h, and then the solvent was removed
under reduced pressure. The oil obtained was treated with 2 mL of
ethanol and the resulting solution stirred at 0 °C until a red solid slowly
separated out which was filtered and crystallized from ethanol; yield
g70%. Anal. Calcd: C, 52.54; H, 5.78; N, 4.23. Found: C, 52.76;
H, 5.63; N, 4.34. Mp: 107 °C.
X-ray Structure Determination of [Mn(CO)3(4-CH3C6H4NdNH)-
{PPh(OEt)2}2]BF4 (1b) and [Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4
(11a). The crystallographic data and the final R indices for the two
compounds 1b and 11a are summarized in Table 2. Both structures
were solved by direct methods (SIR92)20 and refined on F2 using
SHELXL93.21 All the non-hydrogen atoms were refined anisotropi-
cally. For compound 1b an empirical absorption correction was applied
after the last isotropic refinement, according to the method of Walker
and Stuart.22 In each case the hydrogen atoms bonded to N atoms
were located from ∆F maps and refined isotropically, whereas the
remaining ones were included at calculated positions and refined as
(20) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.; Burla,
M. C.; Polidori, G.; Camalli, M. J. Appl. Crystallogr. 1994, 27, 435.
(21) Sheldrick, G. SHELXL93, Program for structure refinement, University
of Gottingen, Germany, 1993.
[MnCl(CO)2{PPh(OEt)2}2]2(µ-4,4′-H15NdNC6H4C6H4Nd15NH)
(10a1). This complex was prepared like the related mononuclear 9b
by treating the labeled [Mn(CO)2{PPh(OEt)2}2]2(µ-4,4′-15NtNC6H4-
(22) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158.

Aryldiazene Complexes of Manganese
Inorganic Chemistry, Vol. 36, No. 7, 1997 1299
Scheme 1a
Figure 1. Perspective drawing of compound 1b, with anisotropic
thermal displacement parameters represented as ellipsoids at the 40%
level of probability. Phenyl and ethoxy groups have been omitted for
clarity.
a P ) PPh(OEt)2 (1, 3), PPh2OEt (2, 4); Ar ) C6H5 (a), 4-CH3C6H4
(b), 2-CH3C6H4 (c), 4-CH3OC6H4 (d), ArAr ) 4,4′-C6H4C6H4 (a), 4,4′-
(2-CH3)C6H3C6H3(2-CH3) (c), 4,4′-C6H4CH2C6H4 (e).
Chart 2
riding atoms with their thermal parameters set up to 1.2 times the values
of the parent atoms (1.5 times for methyl groups).
PARST9523 and ZORTEP24 were used for geometric calculations
and drawings. All calculations were performed on an ENCORE91
station at the Centro di Studi per la Strutturistica Diffrattometrica del
CNR in Parma, Italy.
Results and Discussion
Aryldiazene and Aryldiazenido Complexes. Hydride tri-
carbonyl species MnH(CO)3P2 react quickly with both mono-
and bis(aryldiazonium) cations to give the diazene derivatives
[Mn(CO)3(ArNdNH)P2]+ (1, 2) and [{Mn(CO)3P2}2(µ-
HNdNArArNdNH)]2+ (3, 4) which were isolated in high yields
as BF4- or BPh4- salts and characterized (Scheme 1). Crucial
for the successful preparation of both mono- and binuclear
complexes is the use of an exact stoichiometric ratio between
the reagents and a low temperature at the start of the reaction.
Otherwise, a large amount of decomposition products or oily
substances were found in the final reaction products.
Complexes 1-4 are yellow or orange solids, diamagnetic,
and stable in the air both as solids and in solutions of polar
organic solvents, where they behave as 1:1 (1, 2) or 2:1 (3, 4)
electrolytes.25 Some spectroscopic properties are reported in
Table 1.
Diagnostic for the presence of the diazene ligand in both
1
mono- and binuclear complexes was the high-frequency H
NMR signal of the NH proton at 14.09-13.33 ppm, which is
split into a sharp doublet in the labeled compounds 1a1, 1a2,
1
2
15NH
15NH
and 3a1. The values for both the J
and the J
of 65
Other manganese hydrides with a carbonyl-phosphine ratio
different from 3:2 of the type MnH(CO)2P3 and MnH(CO)P4
[P ) PPh(OEt)2 and PPh2OEt] were also reacted with aryldia-
zonium cations, but in every case no aryldiazene complex was
isolated. Monitoring the progress of the reactions by 1H NMR
spectra revealed the initial formation of a diazene compound
which, however, resulted to be very unstable in solution and
was not isolated. Instead, the hydride MnH(CO)3(dppe) (dppe
and 3.8 Hz, respectively, were also determined, and these
data1,4,26 further support the proposed formulation.
The infrared spectra of both the mono- and the dinuclear
aryldiazene complexes 1-4 show three ν(CO) bands between
2079 and 1939 cm-1, two of which are of strong intensity and
one medium, suggesting the presence of three carbonyl ligands
in a mer position. Furthermore, the broad signal that appears
at room temperature in the 31P{1H} NMR spectra resolves into
a sharp singlet at -90 °C, in agreement with the presence of
two magnetically equivalent phosphine ligands. On these bases
a mer-trans geometry (Chart 2) similar to that found in the
solid state for 1b (Figure 1) can be proposed in solution for all
the aryldiazene derivatives. This similar geometry observed for
both the mononuclear and binuclear diazene complexes agrees
with the other spectroscopic properties (νCO and 1H NMR data)
which result, in all cases, as strictly comparable.
+
) Ph2PCH2CH2PPh2) reacted with ArN2 to give [Mn(CO)3-
(ArNdNH)(dppe)]BF4, but the compound resulted to be impure
and decomposed when crystallization was attempted. However,
despite the absence of good analytical data, the IR (ν(CO) at
1
2029 m, 1951 s, and 1919 s cm-1 in KBr) and the H NMR
spectra [NH at δ 14.17 (s, br) and 4-CH3C6H4 at δ 2.20 (s)
ppm in CD2Cl2 at 25 °C] confirm the proposed formulation. It
seems, therefore, that both the stoichiometry of the complexes
and the nature of the phosphine ligands are important in
determining the stability of the diazene ligand bonded to a
manganese center. In fact, although the insertion reaction of
the aryldiazonium cation into the Mn-H bond seems to proceed
with all the tested hydrides, only with the tricarbonyl fragment
Mn(CO)3P2 containing phosphonite PPh(OEt)2 and phosphinite
PPh2OEt ligands can stable aryldiazene complexes be obtained.
Probably, the greater Π-acceptor properties of our phosphites
as compared with tertiary phosphine ligands play an important
role in stabilizing the aryldiazene ligand bonded to the Mn-
(CO)3P2 fragment. It seems, in fact, that only a delicate
balancing of steric and electronic factors of the ancillary ligands
allows stable aryldiazene complexes of manganese to be
prepared.
The broad signal observed at room temperature for the 31P-
{1H} NMR spectra seems to indicate a fluxional process which
may involve the aryldiazene ligand or the simple interexchange
of the positions of the phosphite groups. A switch in the Mn-N
bond of the ArNdNH ligand from NH to NC can be excluded
1
on the basis of the diazene H NMR spectra, which result in
being sharp between +20 and -90 °C in the 15N-labeled
compounds 1a1, 3a1, and 4a1. A restricted rotation of the
aryldiazene ligand as the temperature is changed cannot be
excluded, and the broad 31P NMR spectra observed at +20 °C
may suggest a slow rotation of the ArNdNH group at this
temperature. This feature, however, contrasts with the 1H NMR
(25) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.
(23) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659.
(24) Zsolnai, L.; Pritzkow, H. ZORTEP. ORTEP original programm
modified for PC, University of Heidelberg, Germany, 1994.
(26) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J. Chem. Soc., Dalton
Trans. 1973, 2713. Carrol, J. A.; Sutton, D.; Xiaoheng, Z. J.
Organomet. Chem. 1982, 244, 73.

1300 Inorganic Chemistry, Vol. 36, No. 7, 1997
Table 1. IR and NMR Data for Manganese Complexes
Albertin et al.
IRa
1H NMRb,c
δ (J (Hz))
14.04 (s)
31P{1H} NMRb,d
no.
compd
ν, cm-1
assgnt
assgnt
NH
δ
1a
[Mn(CO)3(C6H5NdNH){PPh(OEt)2}2]BF4
2062 m, 1981 s, 1948 s
2063 m, 1983 s, 1952 s
ν(CO)
189 (s, br)
4.18 (m)
1.42 (t)
POCH2CH3
POCH2CH3
NH
1a1
1a2
1b
1c
[Mn(CO)3(C6H5Nd15NH){PPh(OEt)2}2]BF4
[Mn(CO)3(C6H515NdNH){PPh(OEt)2}2]BF4
[Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4
[Mn(CO)3(2-CH3C6H4NdNH){PPh(OEt)2}2]BF4
[Mn(CO)3(4-CH3OC6H4NdNH){PPh(OEt)2}2]BPh4
[Mn(CO)3(4-CH3C6H4NdNH)(PPh2OEt)2]BF4
[Mn(CO)3(2-CH3C6H4NdNH)(PPh2OEt)2]BF4
[Mn(CO)3(4-CH3OC6H4NdNH)(PPh2OEt)2]BPh4
ν(CO)
ν(CO)
ν(CO)
ν(CO)
ν(CO)
ν(CO)
ν(CO)
ν(CO)
14.01 (d)
189 (s, br)
1
15
( J NH ) 65)
4.18 (m)
1.40 (t)
POCH2CH3
POCH2CH3
NH
2062 m, 1984 s, 1951 s
2063 m, 1983 s, 1950 s
2059 m, 1983 s, 1953 s
2064 m, 1983 s, 1960 s
2073 m, 1978 s, 1939 s
2060 m, 1982 s, 1956 s
2060 m, 1979 s, 1954 s
14.00 (d)
189 (s, br)
189.9 (s)e
188 (s, br)
2
15
( J NH ) 3.8)
4.18 (m)
1.40 (t)
POCH2CH3
POCH2CH3
NH
POCH2CH3
CH3
POCH2CH3
NH
POCH2CH3
CH3
POCH2CH3
NH
POCH2CH3
OCH3
POCH2CH3
NH
POCH2CH3
CH3
POCH2CH3
NH
POCH2CH3
CH3
POCH2CH3
NH
POCH2CH3
OCH3
POCH2CH3
NH
POCH2CH3
POCH2CH3
NH
13.83 (s)
4.16 (m)
2.35 (s)
1.39 (t)
13.93 (s)
4.19 (m)
2.46 (s)
1.41 (t)
13.39 (s)
4.15 (m)
3.85 (s)
1.38 (t)
13.74 (s)
3.69 (qi)
2.35 (s)
1.17 (t)
13.81 (s)
3.70 (qi)
2.26 (s)
1.18 (t)
13.33 (s)
3.68 (qi)
3.84 (s)
1.16 (t)
189 (s, br)
188 (s, br)
162 (s, br)
163 (s, br)
1d
2b
2c
2d
163 (s, br)
167.7 (s)e
3a
[{Mn(CO)3(PPh(OEt)2)2}2(µ-4,4′-
HNdNC6H4C6H4NdNH)](BF4)2
2067 m, 1986 s, 1950 s
2068 m, 1987 s, 1947 s
ν(CO)
ν(CO)
14.09 (s)
4.19 (m)
1.41 (t)
188 (s, br)
3a1
[{Mn(CO)3(PPh(OEt)2)2}2(µ-4,4′-
H15NdNC6H4C6H4Nd15NH)](BF4)2
14.09 (d)
188 (s, br)
189.9 (s)e
188 (s, br)
1
15
( J NH ) 65)
4.19 (m)
1.41 (t)
POCH2CH3
POCH2CH3
NH
POCH2CH3
CH3
POCH2CH3
NH
POCH2CH3
-CH2-
POCH2CH3
NH
3c
3e
[{Mn(CO)3(PPh(OEt)2)2}2(µ-4,4′-
2061 m, 1982 s, 1952 s
2062 m, 1983 s, 1964 s
ν(CO)
ν(CO)
13.95 (s)
4.19 (m)
2.52 (s)
1.40 (t)
13.88 (s)
4.16 (m)
3.97 (s)
1.37 (t)
HNdN(2-CH3)C6H3C6H3(2-CH3)NdNH}](BF4)2
[{Mn(CO)3(PPh(OEt)2)2}2(µ-4,4′-
HNdNC6H4CH2C6H4NdNH)](BPh4)2
191 (s, br)
4a
[{Mn(CO)3(PPh2OEt)2}2(µ-4,4′-
HNdNC6H4C6H4NdNH)](BF4)2
2062 m, 1987 s, 1945 s
2064 m, 1986 s, 1945 s
ν(CO)
ν(CO)
14.02 (s)
3.72 (qi)
1.19 (t)
162 (s, br)
163.1 (s)e
POCH2CH3
POCH2CH3
NH
4a1
[{Mn(CO)3(PPh2OEt)2}2(µ-4,4′-
14.02 (d)
162 (s, br)
1
H15NdNC6H4C6H4Nd15NH)](BF4)2
( J NH ) 65)
15
3.72 (qi)
1.20 (t)
POCH2CH3
POCH2CH3
NH
4c
[{Mn(CO)3(PPh2OEt)2}2{µ-4,4′-
2062 m, 1984 s, 1950 s
ν(CO)
13.88 (s)
3.72 (qi)
2.34 (s)
162 (s, br)
HNdN(2-CH3)C6H3C6H3(2-CH3)NdNH}](BF4)2
POCH2CH3
CH3
1.20 (t)
POCH2CH3
POCH2CH3
POCH2CH3
5a
5a1
5b
6b
7a
Mn(CO)2(C6H5NN){PPh(OEt)2}2
1943 s, 1864 s
1625 m, 1560 m
1574
1943 s, 1864 s
1611 m, 1544 m
1555
1937 s, 1866 s
1623 m, 1559 m
1590
1923 s, 1843 s
1623 m, 1560 m
ν(CO)
ν(NN)
ν′(NN)g
ν(CO)
ν(NN)
ν′(NN)
ν(CO)
ν(NN)
ν′(NN)
ν(CO)
ν(NN)
3.75-3.60 (m)f
0.78 (t)
203 (s, br)f
203 (s, br)
Mn(CO)2(C6H5N15N){PPh(OEt)2}2
4.02 (m)
1.24 (t)
POCH2CH3
POCH2CH3
Mn(CO)2(4-CH3C6H4NN){PPh(OEt)2}2
Mn(CO)2(4-CH3C6H4NN)(PPh2OEt)2
[Mn(CO)2{PPh(OEt)2}2]2(µ-4,4′-NNC6H4C6H4NN)
4.00 (m)
2.28 (s)
1.23 (t)
3.99 (qi)
2.23 (s)
1.28 (t)
4.05 (m)
1.27 (t)
POCH2CH3
CH3
POCH2CH3
POCH2CH3
CH3
POCH2CH3
POCH2CH3
POCH2CH3
203 (s, br)
201.9 (s)e
176 (s, br)
1941 s, 1861 s
1614 m, 1564 m
1576
ν(CO)
ν(NN)
ν′(NN)
203 (s, br)
201.4 (s)e

Aryldiazene Complexes of Manganese
Inorganic Chemistry, Vol. 36, No. 7, 1997 1301
Table 1. (Continued)
IRa
ν cm-1
1H NMRb,c
31P{1H} NMRb,d
no.
compd
assgnt
δ (J (Hz))
assgnt
δ
7a1 [Mn(CO)2{PPh(OEt)2}2]2(µ-4,4′-15NNC6H4C6H4N15N) 1940 s, 1861 s
ν(CO) 4.06 (m)
ν(NN) 1.27 (m)
ν′(NN)
POCH2CH3 203 (s, br)
POCH2CH3
1607 m, 1546 m
1553
7c
8c
9b
[Mn(CO)2{PPh(OEt)2}2]2{µ-4,4′-
NN(2-CH3)C6H3C6H3(2-CH3)NN}
1944 s, 1863 s
1617 m, 1577 m
1594
1931 s, 1850 s
1617 m, 1577 m
1590
ν(CO) 4.05 (m)
ν(NN) 2.22 (s)
ν′(NN) 1.27 (t)
ν(CO) 4.04 (qi)
ν(NN) 1.99 (s)
ν′(NN) 1.32 (t)
ν(CO) 13.52 (s)
POCH2CH3 203 (s, br)
CH3
POCH2CH3
POCH2CH3 176 (s, br)
CH3
POCH2CH3
[Mn(CO)2(PPh2OEt)2]2{µ-4,4′-
NN(2-CH3)C6H3C6H3(2-CH3)NN)
h
MnCl(CO)2(4-CH3C6H4NdNH){PPh(OEt)2}2
1951 s, 1884 s
NH
191 (s, br)
4.70-3.80 (m) POCH2CH3
2.28 (s)
1.35, 1.33,
1.27 (t)
CH3
POCH2CH3
10a1 [MnCl(CO)2{PPh(OEt)2}2]2(µ-4,4′-
H15NdNC6H4C6H4Nd15NH)
1956 s, 1888 s
ν(CO) 13.70 (d)
NH
190 (s, br)
1
15
( J NH ) 60)
4.25-3.80 (m) POCH2CH3 191.5 (s)e
1.37, 1.29 (t)
POCH2CH3
11a [Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4
11b [Mn(CO)3(CH3NHNH2){PPh(OEt)2}2]BPh4
2057 m, 1968 s, 1944 s
3348 m, 3294 m, 3262 w, 3222 m ν(NH) 2.78 (m)
1617 m
ν(CO) 4.06 (m)i
POCH2CH3 187 (s, br)i
MnNH2NH2
MnNH2NH2
POCH2CH3
δ(NH2) 2.28 (m)
1.39 (t)
2063 m, 1971 s, 1935 s
3318 m, 3270 m, 3192 w
ν(CO) 4.10 (m)i
ν(NH) 3.12 (m)
2.50 (m)
POCH2CH3 187 (s, br)i
NH2
NHCH3
1.99 (d)
NHCH3
(3JHH ) 6)
1.41 (t)
POCH2CH3
11c [Mn(CO)3(C6H5NHNH2){PPh(OEt)2}2]BPh4
2061 m, 1975 s, 1946 s
3341 m, 3298 m
1602 w
ν(CO) 5.75 (t)
ν(NH) 5.10 (m)
δ(NH2) 4.30 (m)
1.42 (t)
C6H5NH
NH2
POCH2CH3
POCH2CH3
188 (s, br)
184.7 (s)e
11d [Mn(CO)3(4-NO2C6H4NHNH2){PPh(OEt)2}2]BPh4
11e [Mn(CO)3{(CH3)2NNH2}{PPh(OEt)2}2]BPh4
12a [Mn(CO)3(NH2NH2)(PPh2OEt)2]BPh4
2063 m, 1986 s, 1947 s
3366 w, 3242 m
ν(CO) 6.68 (t)
ν(NH) 5.46 (m)
4.27 (m)
-C6H4NH 190 (s, br)
NH2
POCH2CH3
POCH2CH3
POCH2CH3 186 (s, br)
NH2
N(CH3)2
1.42 (t)
2056 m, 1969 s, 1944 s
3283 m
ν(CO) 4.23 (m)
ν(NH) 3.59 (s, br)
2.34 (s)
1.43 (t)
POCH2CH3
2050 m, 1964 s, 1935 s
3338 w, 3276 w, 3253 m
1610 m
ν(CO) 3.60 (m)i
ν(NH) 2.98 (m)
δ(NH2) 2.32 (t)
1.15 (t)
POCH2CH3 160 (s, br)i
MnNH2NH2 158.5 (s)e
MnNH2NH2
POCH2CH3
12b [Mn(CO)3(CH3NHNH2)(PPh2OEt)2]BPh4
2054 m, 1972 s, 1941 s
3315 w, 3256 m
1605 m
ν(CO) 3.66 (m, br)i
ν(NH) 3.14 (m)
δ(NH2) 2.64 (m)
1.98 (d)
POCH2CH3 160 (s, br)i
NH2
NHCH3
NHCH3
(3JHH ) 6)
1.21 (t)
POCH2CH3
12c [Mn(CO)3(C6H5NHNH2)(PPh2OEt)2]BPh4
2047 m, 1958 s, 1947 s
3363 w, 3285 w
1616 m
ν(CO) 5.58 (t)
ν(NH) 4.80 (m)
δ(NH2) 3.75 (m)
1.18 (t)
C6H5NH
NH2
POCH2CH3
POCH2CH3
161 (s, br)
12d [Mn(CO)3(4-NO2C6H4NHNH2)(PPh2OEt)2]BPh4
2054 m, 1973 s, 1954 s
3320 w, 3264 m, 3229 m
ν(CO) 6.48 (t)
ν(NH) 3.75 (m)
4.93 (m)
-C6H4NH 166 (s, br)
POCH2CH3
NH2
1.18 (t)
POCH2CH3
a In KBr pellets. b At room temperature in (CD3)2CO. c Phenyl proton resonances are omitted. d Positive shift downfield from 85% H3PO4. e At
-90 °C. f In C6D6. g For calculation see ref 34. h 13C{1H} NMR, δ (CD2Cl2): 227.4 t, 215.7 t (CO); 151-118 m (phenyl); 62.8 s (CH2); 16.2 s
(CH3). i In CD2Cl2.
spectra of the same diazene ligand and was never observed in
previously reported aryldiazene complexes4 or in the related
hydrazine derivatives 11 and 12. Therefore, it is plausible to
assume that the fluxional process simply results in the interex-
change of the position of the P ligands at room temperature,
and the freezing of this change as the temperature is lowered
results in a static structure with equivalent phosphorus nuclei
(sharp singlet) at -90 °C.
(CO)2N2 and was formulated as containing the MnN(Ph)dNH
moiety where the phenyl is located on NR adjacent to the
manganese.9 The compound is, however, thermally unstable
and decomposed at -30 °C like the related dinuclear9 derivative
[CpMn(CO)2]2(µ-PhNdNH). Other aryldiazene complexes of
manganese are only cited, either as an intermediate in the
10
preparation of Mn(CO)2(PhN2)(PPh3)2 or as a very unstable
species in the NaBH4 reduction27 of [(η5-CH3C5H4)Mn(CO)2(o-
A previously reported example of aryldiazene complex of
the type CpMn(CO)2(PhNdNH) was obtained by successive
nucleophilic and electrophilic attack by LiPh and H+ on CpMn-
(27) Barrientos-Penna, C. F.; Einstein, F. W. B.; Jones, T.; Sutton, D. Inorg.
Chem. 1982, 21, 2578.

1302 Inorganic Chemistry, Vol. 36, No. 7, 1997
Albertin et al.
Table 2. Crystallographic Data for Compounds [Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4 (1b) and
[Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4 (11a)
compd
chem formula
fw
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
T, °C
[Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4
C30H38BF4MnN2O7P2
742.33
C2/c (No. 15)
31.857(5)
11.119(2)
22.414(3)
90
97.82(1)
90
[Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4
C47H54BMnN2O7P2
888.65
P1h (No. 2)
13.772(3)
14.951(4)
13.319(3)
104.47(1)
100.32(1)
111.08(1)
22
22
λ, Å
0.710 69
7866(2)
8
1.254
4.77
0.710 69
2365(1)
2
1.245
3.96
V, Å3
Z
F
calcd, g cm-3
µ(Mo KR), cm-1
2
R1(Fo), wR2(Fo )a
0.0708, 0.3600
0.0511, 0.1730
2
2
a R1 ) Σ|Fo - Fc|/Σ(Fo), calculated only on reflections with Fo > 4σ(Fo); wR2 ) xΣ[w(Fo - Fc2)2]/Σ(w(Fo )2], calculated on all reflections.
Scheme 2a
Table 3. Selected Bond Distances (Å) and Angles (deg) with Esd’s
in Parentheses
[Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4
Mn-P1
Mn-P2
Mn-N1
Mn-C8
Mn-C9
Mn-C10
2.263(2)
2.263(2)
1.984(7)
1.855(9)
1.803(9)
1.847(9)
O1-C8
O2-C9
O3-C10
N1-N2
N2-C1
1.136(11)
1.156(12)
1.141(11)
1.263(10)
1.438(11)
C9-Mn-C10
C8-Mn-C10
C8-Mn-C9
N1-Mn-C10
N1-Mn-C9
N1-Mn-C8
P2-Mn-C10
P2-Mn-C9
P2-Mn-C8
P2-Mn-N1
P1-Mn-C10
92.4(4)
179.2(4)
87.3(4)
88.8(3)
178.7(4)
91.4(3)
92.0(3)
90.3(3)
88.8(2)
89.8(2)
90.0(3)
P1-Mn-C9
P1-Mn-C8
P1-Mn-N1
P1-Mn-P2
Mn-N1-N2
Mn-C8-O1
Mn-C9-O2
Mn-C10-O3
N1-N2-C1
N2-C1-C6
N2-C1-C2
90.0(3)
89.2(2)
89.8(2)
a P ) PPh(OEt)2 (5, 7), PPh2OEt (6, 8); R ) C6H5 (a), 4-CH3C6H4
(b), ArAr ) 4,4′-C6H4C6H4 (a), 4,4′-(2-CH3)C6H3C6H3(2-CH3) (c).
177.9(1)
125.1(5)
175.1(8)
176.4(8)
178.8(8)
119.8(7)
125.2(8)
115.2(7)
orange to red with the formation of the aryldiazenido derivatives
[Mn(CO)2(ArN2)P2] (5, 6) and [{Mn(CO)2P2}2(µ-N2ArArN2)]
(7, 8), which were isolated and characterized (Scheme 2). The
+
ammonium cation NHEt3 is also formed during the reaction
course and can be recovered in an equivalent amount as the
BPh4- salt from a CH2Cl2 solution. Furthermore, evolution of
gas (CO) was also observed and the complexes 5-8 were
obtained in almost quantitative yield (g90%) in agreement with
the stoichiometry reported in Scheme 2.
[Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4
Mn-P1
Mn-P2
Mn-N1
Mn-C1
Mn-C2
2.273(1)
2.266(1)
2.125(2)
1.859(2)
1.799(3)
O1-C1
O2-C2
O3-C3
N1-N2
Mn-C3
1.135(3)
1.153(3)
1.138(2)
1.455(3)
1.849(2)
The complexes are air-stable red-orange solids, diamagnetic,
and moderately soluble in both polar and nonpolar organic
solvents and nonelectrolytes. The infrared spectra show in the
ν(CO) region, for both mono- and dinuclear derivatives, two
strong bands at 1944-1843 cm-1, in agreement with two
carbonyl ligands in a mutually cis position. Furthermore, in
the νNN region of the aryldiazenido ligand, two medium-
intensity bands are present at 1625-1617 cm-1 and at 1577-
1559 cm-1, respectively, which are both shifted at a lower
frequency in the corresponding labeled compounds 5a1 and 7a1.
The presence of two or more ν(NN) bands for complexes
containing only one aryldiazenido group is a feature previously
observed for several derivatives, and it was demonstrated that
these bands result from resonance interaction of ν(NN) with
the weak vibrational mode of the attached phenyl group:28 This
probably applies to our derivatives. The values of the imper-
turbated ν′(NN) were also calculated28 and fall in the range
1594-1576 cm-1 (Table 1). A comparison of these ν(NN)
values with those of other aryldiazenido complexes whose
crystal structure is known2b,4b,29 does not allow us to unambigu-
ously assign a coordination mode for the ArN2 ligand, i.e. a
singly-bent or a double-bent geometry. The 1594-1576 cm-1
C2-Mn-C3
C1-Mn-C3
C1-Mn-C2
N1-Mn-C3
N1-Mn-C2
N1-Mn-C1
P2-Mn-C3
P2-Mn-C2
P2-Mn-C1
P2-Mn-N1
89.7(1)
179.1(1)
89.7(1)
90.7(1)
179.2(1)
89.9(1)
92.0(1)
89.1(1)
88.6(1)
91.5(1)
P1-Mn-C3
P1-Mn-C2
P1-Mn-C1
P1-Mn-N1
P1-Mn-P2
Mn-N1-N2
Mn-C1-O1
Mn-C2-O2
Mn-C3-O3
90.0(1)
90.9(1)
89.4(1)
88.5(1)
178.0(0)
117.4(2)
176.5(2)
179.2(2)
177.0(2)
N2C6H4CF3)]BF4, and therefore our compounds 1-4 seem to
be the first stable and well-characterized aryldiazene complexes
of manganese.
Preliminary studies on the chemical properties of these
manganese complexes 1-4 showed that the diazene ligand is
rather inert to substitution by several ligands such as CO,
isocyanides, and phosphites and the starting complex can be,
for example, recovered with high yield (g90%) after 10-12 h
of reaction with CO (1 atm) or an excess of isocyanide. The
use of longer reaction times as well as reflux conditions is
limited, however, by decomposition of the starting derivatives
1-4.
Treatment of both mono- (1, 2) and bis(diazene) (3, 4)
complexes with base resulted in a color change from yellow or
(28) Haymore, B. L.; Ibers, J. A.; Meek, D. W. Inorg. Chem. 1975, 14,
541.

Aryldiazene Complexes of Manganese
Inorganic Chemistry, Vol. 36, No. 7, 1997 1303
Scheme 3
Chart 3
frequency represents, in fact, a borderline case also for the
empirical rule proposed by Haymore and Ibers30 for which the
observed and corrected νNN frequencies fall into at least two
groups, those above and below 1550-1530 cm-1, with those
above characteristic of a singly-bent aryldiazenido ligand. In
Scheme 4a
+
fact, if we hypothesize the presence of a singly-bent ArN2
ligand bonded to a formal Mn(1-) d8 central metal, the observed
pentacoordination results as being plausible and the complex
may be compared with related iron(0) [Fe(CO)2(PPh3)2(C6H5N2)]-
a P ) PPh(OEt)2 (11), PPh2OEt (12); R ) H (a), CH3 (b), Ph (c),
4-NO2C6H4 (d).
29a
4b
BF4 and [Fe(ArN2)P4]BPh4 [P ) P(OEt)3, PPh(OEt)2] or
cobalt(I)31 [Co(ArN2)P4](BPh4)2 derivatives which show, how-
ever, a higher νN2 frequency [1660-1760 cm-1 for Fe(0) and
1770-1790 cm-1 for Co(I)] than our compounds 5-7.
A doubly-bent ArN2- ligand should be obtained, instead, as
the first deprotonation product (Scheme 3) of the [Mn(CO)3-
(ArNdNH)P2]+ cation, giving an aryldiazenido(1-) complex
with a formal Mn(1+) d6 central metal in an octahedral
environment. The dissociation of one ligand (CO) observed in
our case does not seem, however, plausible for such a config-
uration, but rather there is a rearrangement of the ArN2- ligand
to ArN2+ and concurrent formal reduction of the central metal
to Mn(1-) giving a pentacoordinate complex. In the absence
of an X-ray crystal structure, due to the poor quality of the
obtained crystals, no reliable assignment can be made, therefore,
on the singly- or doubly-bent coordination mode of the diazo
ligand as well as on the geometry of the complexes. The 31P-
{1H} NMR spectra of compounds 5-8 indicate, in fact, only
that the two phosphines are magnetically equivalent (only one
singlet present at low temperature) and do not give further
structural information.
νCO bands at 1984-1950 cm-1, in agreement with the presence
of two carbonyls in the mutually cis position. Furthermore,
the 13C{1H} NMR spectra suggest the magnetic unequivalence
of the two CO ligands showing two triplets at δ 227.4 and at δ
215.7 ppm in the carbonyl carbon region. Taking into account
that in the temperature range +30 to -90 °C the 31P{1H} NMR
spectra appear as sharp singlets, a cis-geometry of the type
shown in Chart 3 seems to be present in solution for the new
chloro-aryldiazene 9 derivatives.
Hydrazine Complexes. Treatment of the hydrides MnH-
(CO)3P2 first with triflic acid and then with the appropriate
hydrazine afforded the new [Mn(CO)3(RNHNH2)P2]+ (11, 12)
derivatives which were isolated as BPh4- salts and characterized
(Scheme 4). Studies on this reaction by 1H NMR showed that
the protonation of MnH(CO)3P2 species at low temperature
probably proceeds with the formation of the dihydrogen cation
[Mn(CO)3(η2-H2)P2]+ which is thermally unstable and gives,
after loss of H2, the triflate complex [Mn(OSO2CF3)(CO)3P2].
This complex is a good precursor of hydrazine derivatives
including the disubstituted (CH3)2NNH2 hydrazine compound
[Mn(CO)3{(CH3)2NNH2}{PPh(OEt)2}2]BPh4 (11e). The triflate
complex [Mn(OSO2CF3)(CO)3{PPh(OEt)2}2] was also isolated
as a nonelectrolyte yellow solid and shows the νCO bands at
2057 m, 1966 s, and 1930 s cm-1. Only one resonance at 157.6
ppm was observed in the 31P{1H} NMR spectra (C6D6), while
the proton signals are as follows (C6D6, δ): 7.60-6.70 (phenyl),
3.10 (m, CH2), 0.62 (t, CH3). However, diagnostic for the
presence of the η1-O-coordination of the triflate ion in the
complex is the characteristic band at 1320 cm-1 present in the
IR spectra.32
The previously reported aryldiazenido complexes of manga-
nese whose X-ray structure are known both contain a singly-
bent ArNN ligand, but they are difficult to compare with our
compounds 5-8 because one of them is the dinuclear12
compound [Mn(CO)4(C6H5N2)]2 with two bridging ArN2 groups
and the other is the cationic5 [(η5-CH3C6H4)(CO)2(o-N2C6H4-
CF3)]BF4 complex containing a formal Mn(1+) in an octahedral
environment.
Aryldiazenido complexes 5-8 react with an equimolar
amount of HCl in CH2Cl2 at -80 °C to give the new aryldiazene
complexes [MnCl(CO)2(ArNdNH)P2] which, in the case of Ar
) 4-CH3C6H4, 9b, was isolated in the solid state and character-
ized. Furthermore, in order to determine the nitrogen site of
the protonation, we treated the labeled [Mn(CO)2{PPh(OEt)2}2]2-
(µ-4,4′-15NtNC6H4C6H4Nt15N) (7a1) complex with HCl and
observed that the protonation takes place on the N1 nitrogen
atom affording [MnCl(CO)2{PPh(OEt)2}2]2(µ-4,4′-H15Nd
NC6H4C6H4Nd15NH) (10a1) as the final solid compound.
Finally, the deprotonation reaction of the chloro-diazene
[MnCl(CO)2(ArNdNH)P2] (9b) with triethylamine gives the
aryldiazenido [Mn(CO)2(ArN2)P2], which was also isolated as
a solid. The infrared spectra of the new aryldiazenes show two
All the hydrazine complexes are pale-yellow or green air-
stable solids, diamagnetic, and 1:1 electrolytes.25 Some of their
spectroscopic properties are reported in Table 1. The infrared
spectra confirm the presence of the hydrazine ligand showing
the characteristic ν(NH) bands of medium or weak intensity at
3366-3192 cm-1 and in some case also the δ(NH2) absorption
at 1616-1602 cm-1. Furthermore, in the ν(CO) region three
bands are present (two strong and one medium) between 2063
and 1935 cm-1 suggesting that the three carbonyl ligands are
in a mer position.
In the 1H NMR spectra the hydrazine RNHNH2 proton signals
are present as broad multiplets between 6.48 and 2.28 ppm and
have been clearly assigned by careful integration and decoupling
experiments (Table 1). In the case of the [Mn(CO)3(NH2NH2)-
P2]BPh4 (11a, 12a) complexes both the signals of the coordi-
nated and free NH2 protons appear in the 1H spectra, so
(29) (a) Haymore, B. L.; Ibers, J. A. Inorg. Chem. 1975, 14, 1369. (b)
Cowie, M.; Haymore, B. L.; Ibers, J. A. Ibid. 1975, 14, 2617. (c)
McArdle, J. V.; Schultz, A. J.; Corden, B. J.; Eisenberg, R. Inorg.
Chem. 1973, 12, 1676. (d) Gaughan, A. P.; Haymore, B. L.; Ibers, J.
A.; Myers, W. H.; Nappier, T. E.; Meek, D. W. J. Am. Chem. Soc.
1973, 95, 6859. (e) Cobbledick, R. E.; Einstein, F. W. B.; Farrell, N.;
Gilchrist, A. B.; Sutton, D. J. Chem. Soc., Dalton Trans. 1977, 373.
(30) Haymore, B. L.; Ibers, J. A. Inorg. Chem. 1975, 14, 3060.
(31) Albertin, G.; Bordignon, E. J. Chem. Soc., Dalton Trans. 1986, 2551.
(32) Lawrance, G. A. Chem. ReV. 1986, 86, 17.

1304 Inorganic Chemistry, Vol. 36, No. 7, 1997
Albertin et al.
data seem to support the presence of a diazene ligand in a
complex of the type [Mn(CO)3(HNdNH)P2]+ or, more prob-
ably, of the type [{Mn(CO)3P2}2(µ-HNdNH)]2+ as suggested
by the presence of only one NH signal in the 1H NMR spectra.
The formation of the starting hydrazine complex 11a from
the hypothesized diazene [Mn(CO)3(HNdNH)P2]+ can also be
observed in the NMR tube increasing the sample temperature
from -40 °C, and this may be due to the known dispropor-
tionation reaction7,33 of the diazene complexes affording the
[Mn(CO)3(NH2NH2)P2]+ cation and a very unstable N2 deriva-
tive of the type [Mn(CO)3(N2)P2]+, which was not detected.
The formation of the hydrazine complexes from the solution
containing the diazene derivative may therefore be considered
as a further support for the presence of the HNdNH ligand in
the oxidized complexes. The easy oxidation of the RNHNH2
ligand seems to be, however, the only reaction shown by
compounds 11 and 12, which are robust complexes rather inert
to the substitution of the ligand or to the deprotonation with an
excess of base (NEt3 or LiOH) to give hydrazido(1-) deriva-
tives. Also treatment with H2 (1 atm) does not give any reaction,
and the starting hydrazine complexes can be recovered un-
changed after 48 h of stirring under H2 at room temperature.
X-ray Crystal Structures. Perspective drawings of com-
pounds [Mn(CO)3(4-CH3C6H4NdNH){PPh(OEt)2}2]BF4 (1b)
and [Mn(CO)3(NH2NH2){PPh(OEt)2}2]BPh4 (11a) are shown
in Figures 1 and 2. The two compounds differ only in the nature
of the azo ligand (p-tolyldiazene in 1b and hydrazine in 11a)
and in the counteranion (BF4- and BPh4-, respectively). Both
crystal structures are the result of the packing of discrete cations
and anions, which interact only by means of electrostatic and
dispersive forces.
In both complex cations the coordination polyhedron of the
Mn(I) atom is a distorted octahedron, with the two phosphite
ligands trans to each other and one carbonyl group trans to the
terminal hydrazinic moiety. The bond distance between this
carbonyl group and the central metal is significantly affected
by the trans influence of the azo group, and in both compounds
this distance is about 0.05 Å shorter than the Mn-C distances
involving the two carbonyl groups in trans to each other.
Accordingly, the corresponding C-O distances follow the
opposite trend and the strenghtening of approximately 0.05 Å
of the Mn-C bond results in a weakening of about 0.015 Å of
the C-O bond.
The different nature of the diazo ligand in the two cations is
responsible for the relevant differences in the Mn-N [1.984(7)
and 2.125(2) Å] and N-N distances [1.263(10) and 1.455(2)
Å] (compounds 1b and 11a, respectively). These differences
derive from the different bonding conditions of the N atoms in
the two ligands: while for terminal hydrazine an sp3 hybridiza-
tion is present, the aryldiazene ligand shows an sp2 hybridization,
as already observed in similar compounds.4b In both complexes
the apical phosphorus atoms can be regarded as equivalent with
respect to the diazo moiety, which lies in the equatorial plane
of the coordination octahedron within less than 0.1 Å. The
displacement of N2 from the least-squares equatorial defined
by N1 and the three coordinated carbonyls is 0.05 Å for the
hydrazino and 0.08 Å for the aryldiazenido compounds,
respectively. With respect to the Mn-N bond, the diazo group
is cis to C3-O3 [C3-Mn-N1-N2 ) 2.1(2)°] in the hydrazino
and to C10-O3 [C10-Mn-N1-N2 ) 5.2(7)°] in the aryldia-
zene compound. In the latter, the aryl group and the metal atom
are trans to each other with reference to the NdN bond [Mn-
N1-N2-C1 ) 173.9(6)°]. The aryl plane forms a dihedral
Figure 2. Perspective drawing of compound 11a, with anisotropic
thermal displacement parameters represented as ellipsoids at the 50%
level of probability. Phenyl and ethoxy groups have been omitted for
clarity.
Chart 4
Scheme 5a
a P ) PPh(OEt)2, PPh2OEt; Ar ) C6H5, 4-NO2C6H4.
excluding the presence of a dimeric complex with the NH2NH2
bridging ligand.
In the temperature range between +30 and -90 °C the 31P-
{1H} NMR spectra show a sharp singlet indicating the magnetic
equivalence of the phosphine ligand as in the geometry shown
in Chart 4. Such a geometry for the hydrazine complex 11a
has been confirmed by an X-ray crystal structure determination
whose ORTEP is shown in Figure 2.
Arylhydrazine complexes [Mn(CO)3(ArNHNH2)P2]BPh4
(11c,d, 12c,d) react with an equimolar amount of Pb(OAc)4 at
-40 °C in CH2Cl2 to give the corresponding aryldiazene
derivatives [Mn(CO)3(ArNdNH)P2]+ (1, 2) which can be
isolated in good yields and characterized (Scheme 5). The lead
tetraacetate acts as oxidant on the coordinate arylhydrazine
giving the aryldiazene ligand, which remains bonded to
manganese. The related complexes [Mn(CO)3(ArNdNH)P2]-
BPh4 show spectroscopic properties identical to those of samples
prepared by reacting the hydride MnH(CO)3P2 with aryldiazo-
nium cations, and these features, together with the analytical
data, strongly support the proposed formulation.
These results prompted us to attempt to prepare the diazene
HNdNH complexes by oxidation with Pb(OAc)4 of the hydra-
zine [Mn(CO)3(NH2NH2)P2]BPh4 derivatives. The reaction
proceeds easily at a temperature below -40 °C to give a red
solution from which we were able to isolate only a red oil. This
oil is thermally unstable and slowly decomposes above -40
°C both as an oil and in CH2Cl2 solution giving the starting
hydrazine compound [Mn(CO)3(NH2NH2)P2]BPh4 and other
unidentified products. However, the 1H NMR spectra registered
on an oxidized sample of 11a prepared below -40 °C showed,
beside the phosphite signals, a rather broad signal at 19.0 ppm
(in CH2Cl2) attributable to a NH proton of a diazene ligand.
The 31P{1H} spectra of the same sample appear as only one
resonance at 193.5 ppm. Unfortunately, the compound is too
unstable for a complete characterization, but the spectroscopic
(33) Sellmann, D.; Brandl, A.; Endell, R. J. Organomet. Chem. 1975, 90,
309.

Aryldiazene Complexes of Manganese
Inorganic Chemistry, Vol. 36, No. 7, 1997 1305
angle of 16.0(4)° with the plane of the diazene bond, evidence
of the lack of resonance of the double-bond character between
the sp2 nitrogens and the ring system.
[{Mn(CO)3P2}2(µ-HNdNArArNdNH)](BF4)2 derivatives to be
prepared. The first structural parameters for both an aryldiazene
1b and a hydrazine 11a complex of manganese are also reported.
Among the properties shown by the aryldiazene complexes 1-4
can be cited the easy deprotonation reaction giving new
pentacoordinate aryldiazenido complexes [Mn(CO)2(ArN2)P2]
and [{Mn(CO)2P2}2(µ-N2Ar-ArN2)], which can be protonated
at the N1 nitrogen atom by treatment with HCl to give new
[MnCl(CO)2(ArNdNH)P2] aryldiazene derivatives.
Up to now, only seven complexes3c,34 between a transition
metal and a terminal hydrazine have been studied by X-ray
diffraction, and compound 11a is the first case which contains
Mn.
Conclusions. We have reported in this contribution that
aryldiazene cations of manganese of the type [Mn(CO)3-
(ArNdNH)P2]+ can be prepared both by an insertion reaction
of an aryldiazonium cation into the Mn-H bond of the hydride
species MnH(CO)3P2 and by an oxidation reaction with lead
tetraacetate of the arylhydrazine complexes [Mn(CO)3(RNHNH2)-
P2]BPh4. Crucial for the stabilization of the ArNdNH ligand
seems to be the coordination to the Mn(CO)3P2 fragment
containing phosphonite PPh(OEt)2 and phosphinite PPh2OEt
ligands, and this fragment also allows dinuclear bis(diazene)
Acknowledgment. The financial support of MURST and
the CNR, Rome, is gratefully acknowledged. We thank Daniela
Baldan for technical assistance.
Supporting Information Available: X-ray crystallographic files
in CIF format for compounds 1b and 11a are available on the Internet
only. Access information is given on any current masthead page.
IC9608612
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