Preparations, structures, and electrochemical studies of aryldiazene complexes of rhenium: Syntheses of the first heterobinuclear and heterotrinuclear derivatives with bis(diazene) or bis(diazenido) bridging ligands

Article abstract of DOI:10.1021/ic991393+

The mono- and binuclear aryldiazene complexes [Re(C₆H₅N=NH)(CO)(5-n)P(n)]BY₄ (1-5) and [{Re(CO)(5-n)P(n)}₂-(μ-HN=NAr-ArN=NH)](BY₄)₂ (6-12) [P = P(OEt)₃, PPh(OEt)₂, PPh₂OEt; n = 1-4; Ar-Ar = 4,4'-C₆H₄-C₆H₄, 4,4'-(2-CH₃)C₆H₃-C₆H₃(2-CH₃), 4,4'-C₆H₄-CH₂-C₆H₄; Y = F, Ph) were prepared by reacting the hydride species ReH(CO)(5-n)P(n) with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as other prepared compounds, were characterized spectroscopically (IR; ¹H, ³¹P, ¹³C, and ¹⁵N NMR data), and 1a was also characterized by an X-ray crystal structure determination. [Re(C₆H₅N=NH)(CO){P(OEt)₃}₄]BPh₄ (1a) crystallizes in space group P1 with a = 15.380(5) A, b = 13.037(5) A, c = 16.649(5) A, α = 90.33(5)°, β = 91.2(1)°, γ = 89.71(9)°, and Z = 2. The 'diazene-diazonium' complexes [M(CO)₃P₂(HN=NAr-ArN≡N)]-(BF₄)₂ (13-15, 17) [M = Re, Mn; P = PPh₂OEt, PPh₂OMe, PPh₃; Ar-Ar = 4,4'-C₆H₄-C₆H₄, 4,4'-C₆H₄-CH₂-C₆H₄] and [Re(CO)₄(PPh₂OEt)(4,4'-HN=NC₆H₄-C₆H₄N≡N)](BF₄)₂ (16b) were synthesized by allowing the hydrides MH(CO)₃P₂ or ReH(CO)₄P to react with equimolar amounts of bis(aryldiazonium) cations under appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H₂P'₄ and M2'H(CO)(5-n)P''(n) afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)₃P₂(μ-HN=NAr-ArN=NH)M2HP'₄](BPh₄)₂ (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)₃P₂(μ-HN=NAr-ArN=NH)M2'-(CO)(5-n)P''(n)](BPh₄)₂ (ReMn, MnRe) [M1 = Re, Mn; M2 = Fe, Ru, Os; M2' = Mn, Re; P = PPh₂OEt, PPh₂OMe; P', P'' = P(OEt)₃, PPh(OEt)₂; Ar-Ar = 4,4'-C₆H₄-C₆H₄, 4,4'-C₆H₄-CH₂-C₆H₄; n = 1, 2]. The heterotrinuclear complexes [Re(CO)₃(PPh₂OEt)₂(μ-4,4'-HN=NC₆H₄-C₆H₄N=NH)M{P(OEt)₃}₄(μ-4,4'-H N=NC₆H₄-C₆H₄N=NH)Mn(CO)₃(PPh₂OEt)₂](BPh₄)₄ (M = Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobinuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex with a bis(aryldiazenido) bridging ligand [Mn(CO)₂(PPh₂OEt)₂(μ-4,4'-N₂C₆H₄-C₆H₄N₂)Fe{P(OEt)₃}₄]BPh₄ (MnFe) was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)₃(PPh₂OEt)₂(μ-4,4'-HN=NC₆H₄-C₆H₄N=NH)Fe(4-CH₃C₆H₄CN){P(OEt )₃}₄](BPh₄)₃. Finally, the binuclear compound [Re(CO)₃(PPh₂OEt)₂(μ-4,4'-HN=NC₆H₄-C₆H₄N₂)Fe(CO)₂{P(OPh)₃}₂](BP h₄)₂ (ReFe) containing a diazene-diazenido bridging ligand was prepared by reacting [Re(CO)₃(PPh₂OEt)₂(4,4'-HN=NC₆H₄-C₆H₄N≡N)]₊ with the FeH₂(CO)₂{P(OPh)₃}₂ hydride derivative. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear aryldiazenido compounds Mn(C₆H₅N₂)(CO)₂P₂ and {Mn(CO)₂P₂}₂(μ-4,4'-N₂C₆H₄-C₆H₄N₂) (P = PPh₂OEt) was also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal centers behave independently in the presence of the diazenido bridging unit.

Full text of DOI:10.1021/ic991393+

Inorg. Chem. 2000, 39, 3265-3279
3265
Preparations, Structures, and Electrochemical Studies of Aryldiazene Complexes of
Rhenium: Syntheses of the First Heterobinuclear and Heterotrinuclear Derivatives with
Bis(diazene) or Bis(diazenido) Bridging Ligands
Gabriele Albertin,*,† Stefano Antoniutti,† Alessia Bacchi,‡ Giovanni B. Ballico,†
Emilio Bordignon,† Giancarlo Pelizzi,‡ Maria Ranieri,† and Paolo Ugo§
Dipartimento di Chimica, Universita` Ca’Foscari di Venezia, Dorsoduro 2137, 30123 Venezia, Italy,
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Centro CNR di Strutturistica Diffrattometrica, Universita` di Parma, Viale delle Scienze,
43100 Parma, Italy, and Dipartimento di Chimica Fisica, Universita` Ca’Foscari di Venezia,
Dorsoduro 2137, 30123 Venezia, Italy
ReceiVed December 3, 1999
The mono- and binuclear aryldiazene complexes [Re(C6H5NdNH)(CO)5-nPn]BY4 (1-5) and [{Re(CO)5-nPn}2-
(µ-HNdNAr-ArNdNH)](BY4)2 (6-12) [P ) P(OEt)3, PPh(OEt)2, PPh2OEt; n ) 1-4; Ar-Ar ) 4,4′-C6H4-
C6H4, 4,4′-(2-CH3)C6H3-C6H3(2-CH3), 4,4′-C6H4-CH2-C6H4; Y ) F, Ph) were prepared by reacting the hydride
species ReH(CO)5-nPn with the appropriate mono- and bis(aryldiazonium) cations. These compounds, as well as
1
other prepared compounds, were characterized spectroscopically (IR; H, 31P, 13C, and 15N NMR data), and 1a
was also characterized by an X-ray crystal structure determination. [Re(C6H5NdNH)(CO){P(OEt)3}4]BPh4 (1a)
crystallizes in space group P1h with a ) 15.380(5) Å, b ) 13.037(5) Å, c ) 16.649(5) Å, R ) 90.33(5)°, â )
91.2(1)°, γ ) 89.71(9)°, and Z ) 2. The “diazene-diazonium” complexes [M(CO)3P2(HNdNAr-ArNtN)]-
(BF4)2 (13-15, 17) [M ) Re, Mn; P ) PPh2OEt, PPh2OMe, PPh3; Ar-Ar ) 4,4′-C6H4-C6H4, 4,4′-C6H4-
CH2-C6H4] and [Re(CO)4(PPh2OEt)(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (16b) were synthesized by allowing
the hydrides MH(CO)3P2 or ReH(CO)4P to react with equimolar amounts of bis(aryldiazonium) cations under
appropriate conditions. Reactions of diazene-diazonium complexes 13-17 with the metal hydrides M2H2P′4
and M2′H(CO)5-nP′′n afforded the heterobinuclear bis(aryldiazene) derivatives [M1(CO)3P2(µ-HNdNAr-ArNd
NH)M2HP′4](BPh4)2 (ReFe, ReRu, ReOs, MnRu, MnOs) and [M1(CO)3P2(µ-HNdNAr-ArNdNH)M2′-
(CO)5-nP′′n](BPh4)2 (ReMn, MnRe) [M1 ) Re, Mn; M2 ) Fe, Ru, Os; M2′ ) Mn, Re; P ) PPh2OEt, PPh2OMe;
P′, P′′ ) P(OEt)3, PPh(OEt)2; Ar-Ar ) 4,4′-C6H4-C6H4, 4,4′-C6H4-CH2-C6H4; n ) 1, 2]. The heterotrinuclear
complexes [Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)M{P(OEt)3}4(µ-4,4′-HNdNC6H4-C6H4Nd
NH)Mn(CO)3(PPh2OEt)2](BPh4)4 (M ) Ru, Os) (ReRuMn, ReOsMn) were obtained by reacting the heterobi-
nuclear complexes ReRu and ReOs with the appropriate diazene-diazonium cations. The heterobinuclear complex
with a bis(aryldiazenido) bridging ligand [Mn(CO)2(PPh2OEt)2(µ-4,4′-N2C6H4-C6H4N2)Fe{P(OEt)3}4]BPh4 (MnFe)
was prepared by deprotonating the bis(aryldiazene) compound [Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4Nd
NH)Fe(4-CH3C6H4CN){P(OEt)3}4](BPh4)3. Finally, the binuclear compound [Re(CO)3(PPh2OEt)2(µ-4,4′-HNd
NC6H4-C6H4N2)Fe(CO)2{P(OPh)3}2](BPh4)2 (ReFe) containing a diazene-diazenido bridging ligand was prepared
by reacting [Re(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4NtN)]+ with the FeH2(CO)2{P(OPh)3}2 hydride deriva-
tive. The electrochemical reduction of mono- and binuclear aryldiazene complexes of both rhenium (1-12) and
the manganese, as well as heterobinuclear ReRu and MnRu complexes, was studied by means of cyclic
voltammetry and digital simulation techniques. The electrochemical oxidation of the mono- and binuclear
aryldiazenido compounds Mn(C6H5N2)(CO)2P2 and {Mn(CO)2P2}2(µ-4,4′-N2C6H4-C6H4N2) (P ) PPh2OEt) was
also examined. Electrochemical data show that, for binuclear compounds, the diazene bridging unit allows
delocalization of electrons between the two different redox centers of the same molecule, whereas the two metal
centers behave independently in the presence of the diazenido bridging unit.
Introduction
bridging ligands,3 and none containing two different metals have
ever been reported. In the course of our studies on the reactivity
of rhenium hydride complexes with mono- and bis(aryldiazo-
nium) cations, we prepared the mononuclear aryldiazene
Although a large number of studies on the syntheses, struc-
tures, and reactivity of aryldiazene and aryldiazenido complexes
of transition metals have been reported,1,2 very few of them
involve binuclear species with bis(diazene) or bis(diazenido)
(2) (a) Zollinger, H. Diazo Chemistry II; VCH: Weinheim, Germany,
1995. (b) Johnoson, 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, U.K., 1987;
Vol. 2, p 130. (c) Henderson, R. A.; Leigh, G. J.; Pickett, C. J. AdV.
Inorg. Chem. Radiochem. 1983, 27, 197. (d) Nugent, W. A.; Haymore,
B. L. Coord. Chem. ReV. 1980, 31, 123.
† Dipartimento di Chimica, Universita` Ca’Foscari di Venezia.
‡ Universita` di Parma.
§ Dipartimento di Chimica Fisica, Universita` Ca’Foscari di Venezia.
(1) (a) Sutton, D. Chem. ReV. 1993, 93, 995. (b) Kisch, H.; Holzmeier, P.
AdV. Organomet. Chem. 1992, 34, 67.
10.1021/ic991393+ CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/01/2000

3266 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
Chart 1
one type of stable aryldiazene complex, [Re(η5-C5H5)(CO)2-
(HNdNR)] (R ) 4-CH3C6H4, 4-CH3OC6H4), has been de-
scribed,6,7b prepared by reacting an aryldiazenido [Re(η5-C5H5)-
(CO)2(N2R)]BF4 complex with NaBH4.
It therefore seemed of interest to report some new results on
the aryldiazene chemistry of rhenium, including an X-ray crystal
structure determination and an electrochemical study aimed at
comparing the obtained results with those for related manganese
complexes3b and shedding light on the different electrochemical
behaviors shown by bis(aryldiazene) and bis(aryldiazenido)
binuclear derivatives.3a,c
complexes [{Re}-HNdNAr-ArNtN]2+, still containing a
diazonium -NtN group potentially able to react with another
metal hydride, affording heterobinuclear bis(aryldiazene) deriva-
tives (Chart 1).
The syntheses, characterizations, and electrochemical studies
of this new class of binuclear complexes, also including bis-
(aryldiazenido) and diazene-diazenido bridging ligands, are the
subject of this report.
Furthermore, in view of current interest1,2,4 in the chemistry
of “diazo” complexes, due not only to their importance in
nitrogen fixation processes but also to their diverse reactivity
modes and structural properties, in this paper we report an
extensive study on the reactivity of the hydride species
ReH(CO)5-nPn (P ) phosphite) toward aryldiazonium cations,
which allows mono- and homobinuclear bis(aryldiazene) com-
plexes to be prepared.
Diazo complexes of rhenium have been widely studied1,2 and
include mainly aryldiazenido5 [Re]-N2Ar, arylhydrazido,5j,k,6-8
and hydrazine9 derivatives, whereas there have been fewer
investigations on the aryldiazene complexes. In fact, apart from
chelate organodiazene complexes10 of the type [ReCl(HNd
Npy)(NNpy)(PPhMe2)2]+, [ReCl2(NNC4H2N2CF3)(HNdNC4-
H2N2CF3)(PPh3)], and [ReCl3(NNC5H4NH)(HNdNC5H4N)],
obtained from the reaction of NaReO4 or ReOCl3P2 (P ) tertiary
phosphine) with hydrazinopyridine or hydrazinopyrimidine, only
Experimental Section
General Materials and Methods. All synthetic work was carried
out under an appropriate atmosphere (Ar or N2) using standard Schlenk
techniques or a vacuum atmosphere drybox. Once isolated, the
complexes were found to be relatively stable in air but were nevertheless
stored under an inert atmosphere at -25 °C. All solvents were dried
over appropriate drying agents, degassed on a vacuum line, and distilled
into vacuum-tight storage flasks. Triethyl phosphite was an Aldrich
product, purified by distillation under nitrogen. The phosphines PPh-
(OEt)2, PPh2OEt, and PPh2OMe were prepared by the method of
Rabinowitz and Pellon.11 The complex Re2(CO)10 was purchased from
Pressure Chemical Co. (Pittsburgh, PA) and used as received. Diazo-
nium salts were obtained in the usual way.12 The related bis(diazonium)
salts [N2Ar-ArN2](BF4)2 [Ar-Ar ) 4,4′-C6H4-C6H4, 4,4′-(2-CH3)-
C6H3-(2-CH3)C6H3, 4,4′-C6H4-CH2-C6H4] were prepared by treating
the amine precursors H2NAr-ArNH2 with NaNO2, as described in the
literature for common mono(diazonium) salts.12 The labeled diazonium
tetrafluoroborates [C6H5Nt15N]BF4 and [4,4′-15NtNC6H4-C6H4Nt
15N](BF4)2 were prepared from Na15NO2 (99% enriched, CIL) and the
appropriate amine. Alternatively, the [C6H515NtN]BF4 salt was pre-
pared from NaNO2 and C6H515NH2. Other reagents were purchased from
commercial sources in the highest available purity and used as received.
Infrared spectra were recorded on a Nicolet Magna 750 FT-IR
spectrophotometer. NMR spectra (1H, 31P, 13C, 15N) were obtained on
a Bruker AC200 spectrometer at temperatures between -90 and +30
(3) (a) Albertin, G.; Antoniutti, S.; Bacchi, A.; Bordignon, E.; Pelizzi,
G.; Ugo, P. Inorg. Chem. 1996, 35, 6245. (b) Albertin, G.; Antoniutti,
S.; Bacchi, A.; Bordignon, E.; Busatto, F.; Pelizzi, G. Inorg. Chem.
1997, 36, 1296. (c) Albertin, G.; Antoniutti, S.; Bacchi, A.; Barbera,
D.; Bordignon, E.; Pelizzi, G.; Ugo, P. Inorg. Chem. 1998, 37, 5602.
(4) (a) Hidai, M.; Mizobe, Y. Chem. ReV. 1995, 95, 1115. (b) Eady, R.
R.; Leigh, G. J. J. Chem. Soc., Dalton Trans. 1994, 2739. (c) Sellmann,
D. Angew. Chem., Int. Ed. Engl. 1993, 32, 64.
°C, unless otherwise noted. H and 13C NMR spectra refer to internal
1
tetramethylsilane; 31P{1H} NMR chemical shifts are reported with re-
spect to 85% H3PO4, with downfield shifts considered positive; 15N
NMR spectra refer to external CH315NO2, with downfield shifts con-
sidered positive. The SwaN-MR software package13 was used to treat
NMR data. The conductivities of 10-3 M solutions of the complexes
in CH3NO2 at 25 °C were measured with a Radiometer CDM 83.
Syntheses of the Complexes. The hydride species ReH(CO)P4, ReH-
(CO)2P3, ReH(CO)3P2, ReH(CO)4P, and MnH(CO)3P2 [P ) P(OEt)3,
PPh(OEt)2, PPh2OEt, PPh2OMe] were prepared according to literature
procedures.14,15 The dihydride compounds FeH2[P(OEt)3]4,16 [FeH(4-
(5) For aryldiazenido complexes, see: (a) da Costa, M. T. A. R. S.;
Dilworth, J. R.; Duarte, M. T.; da Silva, J. J. R. F.; Galva˜o, A. M.;
Pombeiro, A. J. L. J. Chem. Soc., Dalton Trans. 1998, 2405. (b)
Garcia-Minsal, A.; Sutton, D. Organometallics 1996, 15, 332. (c) Rose,
D. J.; Maresca, K. P.; Kettler, P. B.; Chang, Y.-D.; Soghomomian,
V.; Chen, Q.; Abrams, M. J.; Larsen, S. K.; Zubieta, J. Inorg. Chem.
1996, 35, 3548. (d) Coutinho, B.; Dilworth, J. R.; Jobanputra, P.;
Thompson, R. M.; Schmid, S.; Stra¨hle, J.; Archer, C. M. J. Chem.
Soc., Dalton Trans. 1995, 1663. (e) Cusanelli, A.; Sutton, D.
Organometallics 1995, 14, 4651. (f) Cusanelli, A.; Batchelor, R. J.;
Einstein, F. W. B.; Sutton, D. Organometallics 1994, 13, 5096. (g)
Kettler, P. B.; Chang, Y.-D.; Zubieta, J. Inorg. Chem. 1994, 33, 5864.
(h) Carr, S. W.; Fontaine, X. L. R.; Shaw, B. L. J. Chem. Soc., Dalton
Trans. 1987, 3067. (i) Ali, H. M.; Leigh, G. J. J. Chem. Soc., Dalton
Trans. 1986, 213. (j) Barrientos-Penna, C. F.; Gilchrist, A. B.; Klahn-
Oliva, A. H.; Hanlan, A. J. L.; Sutton, D. Organometallics 1985, 4,
478. (k) Dilworth, J. R.; Harrison, S. A.; Walton, D. R. M.; Schweda,
E. Inorg. Chem. 1985, 24, 2594.
19
CH3C6H4CN){P(OEt)3}4]BPh4,17e RuH2[P(OEt)3]4,18 OsH2P4 [P )
20
P(OEt)3, PPh(OEt)2], and FeH2(CO)2[P(OPh)3]2 were also prepared
by following reported methods.
(11) Rabinowitz, R.; Pellon, J. J. Org. Chem. 1961, 26, 4623.
(12) Vogel, A. I. Practical Organic Chemistry, 3rd ed.; Longmans, Green
and Co.: New York, 1956.
(6) Barrientos-Penna, C. F.; Einstein, F. W. B.; Jones, T.; Sutton, D. Inorg.
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(7) (a) Dilworth, J. R.; Henderson, R. A.; Dahlstrom, P.; Nicholson, T.;
Zubieta, J. A. J. Chem. Soc., Dalton Trans. 1987, 529. (b) Barrientos-
Penna, C. F.; Campana, C. F.; Einstein, F. W. B.; Jones, T.; Sutton,
D.; Tracey, A. S. Inorg. Chem. 1984, 23, 363.
(8) (a) Nicholson, T.; Zubieta, J. A. J. Chem. Soc., Chem. Commun. 1985,
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Cheng, T.-Y.; Peters, J. C.; Hillhouse, G. L. J. Am. Chem. Soc. 1994,
116, 204.
(10) (a) Hirsch-Kuchma, M.; Nicholson, T.; Davison, A.; Davis, W. M.;
Jones, A. G. Inorg. Chem. 1997, 36, 3237. (b) Hirsch-Kuchma, M.;
Nicholson, T.; Davison, A.; Davis, W. M.; Jones, A. G. J. Chem. Soc.,
Dalton Trans. 1997, 3185. (c) Nicholson, T.; Cook, J.; Davison, A.;
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Acta 1996, 252, 421, 427. (d) Kettler, P. B.; Chang, Y.-D.; Chen, Q.;
Zubieta, J. A.; Abrams, M. J.; Larsen, S. K. Inorg. Chim. Acta 1995,
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(13) Balacco, G. J. Chem. Inf. Comput. Sci. 1994, 34, 1235.
(14) Albertin, G.; Antoniutti, S.; Garcia-Fonta´n, S.; Carballo, R.; Padoan,
F. J. Chem. Soc., Dalton Trans. 1998, 2071.
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Organometallics 1997, 16, 4959.
(16) Tebbe, F. N.; Meakin, P.; Jesson, J. P.; Muetterties, E. L. J. Am. Chem.
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1989, 2353.

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3267
[Re(C6H5NdNH)(CO){P(OEt)3}4]BPh4 (1a), [Re(C6H5NdNH)-
(CO)2(PPh2OEt)3]BF4 (2a), and [Re(C6H5NdNH)(CO)3P2]BF4 (3,
4, 5) [P ) P(OEt)3 (3a), PPh(OEt)2 (4a), PPh2OEt (5a)]. The
appropriate hydride ReH(CO)5-nPn (n ) 2, 3, 4) (0.15 mmol) and the
phenyldiazonium salt [C6H5N2]BF4 (0.15 mmol, 29 mg) were placed
in a 25-mL three-necked flask, and after the mixture was cooled to
-196 °C, 10 mL of (CH3)2CO was added. The reaction mixture was
brought to room temperature and stirred for 4 h, and the solvent was
then removed under reduced pressure. The resulting oil was treated
with ethanol (2 mL), affording a yellow solution that slowly deposited
a crystalline solid, which was filtered off and crystallized by cooling
to -25 °C a saturated solution in ethanol prepared at 30 °C; yield
g65%. The yield could be increased (to about 90%) by adding to the
yellow solution in ethanol an excess of NaBF4 (0.30 mmol, 33 mg) in
2 mL of ethanol. In the case of 1, the complex was precipitated as its
BPh4 salt by adding an excess of NaBPh4 (0.3 mmol, 103 mg) in 2 mL
of ethanol. After filtration and crystallization from a mixture of CH2-
Cl2 (2 mL) and ethanol (3 mL), the yield was g75%. Anal. Calcd for
C55H86N2BO13P4Re (1a): C, 50.65; H, 6.65; N, 2.15. Found: C, 50.47;
H, 6.54; N, 2.10. ΛM ) 51.2 Ω-1 mol-1 cm2. Anal. Calcd for C50H51N2-
BF4O5P3Re (2a): C, 53.34; H, 4.57; N, 2.49. Found: C, 53.45; H,
4.46; N, 2.43. ΛM ) 89.7 Ω-1 mol-1 cm2. Anal. Calcd for C21H36N2-
BF4O9P2Re (3a): C, 31.71; H, 4.56; N, 3.52. Found: C, 31.54; H,
4.64; N, 3.45. ΛM ) 92.2 Ω-1 mol-1 cm2. Anal. Calcd for C29H36N2-
BF4O7P2Re (4a): C, 40.52; H, 4.22; N, 3.26. Found: C, 40.44; H,
4.15; N, 3.25. ΛM ) 86.7 Ω-1 mol-1 cm2. Anal. Calcd for C37H36N2-
BF4O5P2Re (5a): C, 48.11; H, 3.93; N, 3.03. Found: C, 47.98; H,
3.97; N, 3.13. ΛM ) 85.9 Ω-1 mol-1 cm2.
4,4′-C6H4-C6H4 (b), 4,4′-(2-CH3)C6H3-C6H3(2-CH3) (c), 4,4′-C6H4-
CH2-C6H4 (d)]. These complexes were prepared like the related BPh4
derivatives 10 and 11 by reacting the appropriate hydride ReH(CO)3P2
(0.3 mmol) and [N2Ar-ArN2](BF4)2 salt at low temperature (-196 °C)
in acetone solution (10 mL). The reaction mixture, evaporated to dryness
under reduced pressure, gave an oil, which was triturated with ethanol
(2 mL). In this case, a yellow solid slowly appeared in the resulting
solution. This was filtered off and crystallized by cooling to -25 °C a
saturated solution in ethanol prepared at 30 °C; yield g70%. Anal.
Calcd for C42H70N4B2F8O18P4Re2 (9b): C, 31.75; H, 4.44; N, 3.53.
Found: C, 31.98; H, 4.51; N, 3.48. ΛM ) 186.2 Ω-1 mol-1 cm2. Anal.
Calcd for C58H70N4B2F8O14P4Re2 (10b): C, 40.57; H, 4.11; N, 3.26.
Found: C, 40.72; H, 4.19; N, 3.25. ΛM ) 177.1 Ω-1 mol-1 cm2. Anal.
Calcd for C59H72N4B2F8O14P4Re2 (10d): C, 40.94; H, 4.19; N, 3.24.
Found: C, 40.82; H, 4.28; N, 3.18. ΛM ) 160.7 Ω-1 mol-1 cm2. Anal.
Calcd for C74H70N4B2F8O10P4Re2 (11b): C, 48.17; H, 3.82; N, 3.04.
Found: C, 48.09; H, 3.90; N, 3.11. ΛM ) 186.4 Ω-1 mol-1 cm2. Anal.
Calcd for C76H74N4B2F8O10P4Re2 (11c): C, 48.73; H, 3.98; N, 2.99.
Found: C, 48.61; H, 4.05; N, 3.04. ΛM ) 180.7 Ω-1 mol-1 cm2.
[{Re(CO)2(PPh2OEt)3}2(µ-4,4′-H15NdNC6H4-C6H4Nd15NH)]-
(BPh4)2 (8b*) and [{Re(CO)3[PPh(OEt)2]2}2(µ-4,4′-H15NdNC6H4-
C6H4Nd15NH)](BF4)2 (11b*). These complexes were prepared by
following the method described for the related compounds 8b and 11b
using the labeled [4,4′-15NtNC6H4-C6H4Nt15N](BF4)2 bis(diazonium)
salt; yield g75%.
ReH(CO)3(PPh3)2. In a 25-mL three-necked Pyrex Schlenk flask
were placed 0.3 mL (2.1 mmol) of ReH(CO)5, an excess of PPh3 (5.9
mmol, 1.6 g), and 25 mL of toluene, and the resulting solution was
irradiated at room temperature for 6 h using a standard 400 W medium-
pressure mercury arc lamp. A white solid began to precipitate during
irradiation, and after concentration of the reaction mixture to 10 mL,
this solid was filtered off, washed with toluene, and dried under vacuum;
yield g30%. Anal. Calcd for C39H31O3P2Re: C, 58.86; H, 3.93.
[Re(C6H5Nd15NH)(CO)3{PPh(OEt)2}2]BF4 (4a*) and [Re-
(C6H515NdNH)(CO)3{PPh(OEt)2}2]BF4 (4a**). These complexes
were prepared exactly like the related compound 4a using labeled
[C6H5Nt15N]BF4 and [C6H515NtN]BF4 diazonium salts, respectively;
yield g65%.
Found: C, 58.67; H, 4.12. IR (KBr): 2080 m, 1914 br [ν(CO)] cm-1
.
[{Re(CO)[P(OEt)3]4}2(µ-HNdNAr-ArNdNH)](BPh4)2 (6b, 6d),
[{Re(CO)2P3}2(µ-HNdNAr-ArNdNH)](BPh4)2 (7b, 7d, 8b) [P )
PPh(OEt)2 (7), PPh2OEt (8)], [{Re(CO)3P2}2(µ-HNdNAr-ArNd
NH)](BPh4)2 (10c, 11d) [P ) PPh(OEt)2 (10), PPh2OEt (11)], and
[{Re(CO)4(PPh2OEt)}2(µ-HNdNAr-ArNdNH)](BPh4)2 (12b) [Ar-
Ar ) 4,4′-C6H4-C6H4 (b), 4,4′-(2-CH3)C6H3-C6H3(2-CH3) (c), 4,4′-
C6H4-CH2-C6H4 (d)]. The appropriate hydride ReH(CO)5-nPn (n )
4, 3, 2, 1) (0.3 mmol) and bis(aryldiazonium) salt [N2Ar-ArN2](BF4)2
(0.15 mmol) were placed in a 25-mL three-necked flask, and the mixture
was cooled to -196 °C, after which 10 mL of acetone was added. The
reaction mixture was brought to room temperature and stirred for 4 h,
and the solvent was then removed under reduced pressure. The resulting
oil was triturated with 2 mL of ethanol, giving a yellow solution, from
which the complex was precipitated by adding a slight excess of NaBPh4
(0.4 mmol, 137 mg) in 1 mL of ethanol. After crystallization from
CH2Cl2/ethanol/diethyl ether (1/3/5 mL), the complex was filtered off
and dried under vacuum; the yields were between 60 and 80%. Anal.
Calcd for C110H170N4B2O26P8Re2 (6b): C, 50.69; H, 6.57; N, 2.15.
Found: C, 50.56; H, 6.65; N, 2.20. ΛM ) 114.5 Ω-1 mol-1 cm2. Anal.
Calcd for C111H172N4B2O26P8Re2 (6d): C, 50.88; H, 6.62; N, 2.14.
Found: C, 51.03; H, 6.74; N, 2.07. ΛM ) 107.0 Ω-1 mol-1 cm2. Anal.
Calcd for C124H140N4B2O16P6Re2 (7b): C, 59.05; H, 5.59; N, 2.22.
Found: C, 59.22; H, 5.55; N, 2.16. ΛM ) 105.6 Ω-1 mol-1 cm2. Anal.
Calcd for C125H142N4B2O16P6Re2 (7d): C, 59.19; H, 5.64; N, 2.21.
Found: C, 59.25; H, 5.71; N, 2.09. ΛM ) 109.1 Ω-1 mol-1 cm2. Anal.
Calcd for C148H140N4B2O10P6Re2 (8b): C, 65.48; H, 5.20; N, 2.06.
Found: C, 65.60; H, 5.12; N, 1.96. ΛM ) 104.8 Ω-1 mol-1 cm2. Anal.
Calcd for C108H114N4B2O14P4Re2 (10c): C, 58.70; H, 5.20; N, 2.54.
Found: C, 58.81; H, 5.23; N, 2.41. ΛM ) 113.3 Ω-1 mol-1 cm2. Anal.
Calcd for C123H112N4B2O10P4Re2 (11d): C, 63.56; H, 4.86; N, 2.41.
Found: C, 63.41; H, 4.99; N, 2.40. ΛM ) 103.6 Ω-1 mol-1 cm2. Anal.
Calcd for C96H80N4B2O10P2Re2 (12b): C, 60.51; H, 4.23; N, 2.94.
Found: C, 61.88; H, 4.11; N, 2.49. ΛM ) 106.4 Ω-1 mol-1 cm2.
[{Re(CO)3P2}2(µ-HNdNAr-ArNdNH)](BF4)2 (9b, 10b, 10d, 11b,
11c) [P ) P(OEt)3 (9), PPh(OEt)2 (10), PPh2OEt (11); Ar-Ar )
1H NMR (C6D6, 25 °C): δ 7.90-6.90 (m, 30 H, Ph), -4.45 (t, 1 H,
hydride, JPH ) 18 Hz). 31P{1H} NMR (C6D6, 25 °C): δ 22.54 (s).
[Re(CO)3P2(HNdNAr-ArNtN)](BF4)2 (13b, 13d, 14b, 15b) [P
) PPh2OEt (13), PPh2OMe (14), PPh3 (15); Ar-Ar ) 4,4′-C6H4-
C6H4 (b), 4,4′-C6H4-CH2-C6H4 (d)] and [Re(CO)4(PPh2OEt)(4,4′-
HNdNC6H4-C6H4NtN)](BF4)2 (16b). A solution of the appropriate
hydride ReH(CO)3P2 or ReH(CO)4P (0.3 mmol) in 40 mL of acetone
was cooled to -80 °C and quickly transferred by needle into a solution
of an [N2Ar-ArN2](BF4)2 bis(aryldiazonium) salt (0.3 mmol) in 30
mL of acetone cooled to -196 °C. The reaction mixture was brought
to 0 °C and stirred for 5 h. The solvent was removed under reduced
pressure, giving an oil which was rather difficult to transform into a
solid. However, after crystallization of the oil from CH2Cl2/ethanol (2/5
mL), solid products were obtained in the case of compounds 13 and
15. These were filtered off and dried under vacuum. Gummy orange
products were obtained for compounds 14 and 16, which were also
characterized and used for further reactions. The yields were between
60 and 80%. Anal. Calcd for C43H39N4B2F8O5P2Re (13b): C, 46.38;
H, 3.53; N, 5.03. Found: C, 46.46; H, 3.60; N, 5.12. ΛM ) 184.7 Ω-1
mol-1 cm2. Anal. Calcd for C44H41N4B2F8O5P2Re (13d): C, 46.87; H,
3.66; N, 4.97. Found: C, 46.71; H, 3.68; N, 5.11. ΛM ) 191.4 Ω-1
mol-1 cm2. Anal. Calcd for C41H35N4B2F8O5P2Re (14b): C, 45.37; H,
3.25; N, 5.16. Found: C, 45.59; H, 3.34; N, 5.25. ΛM ) 185.6 Ω-1
mol-1 cm2. Anal. Calcd for C51H39N4B2F8O3P2Re (15b): C, 52.02; H,
3.34; N, 4.76. Found: C, 52.16; H, 3.46; N, 4.88. ΛM ) 182.9 Ω-1
mol-1 cm2. Anal. Calcd for C30H24N4B2F8O5PRe (16b): C, 39.54; H,
2.65; N, 6.15. Found: C, 39.35; H, 2.69; N, 6.30. ΛM ) 188.4 Ω-1
mol-1 cm2.
[Re(CO)3(PPh2OEt)2(4,4′-H15NdNC6H4-C6H4Nt15N)](BF4)2 (13b*)
and [Re(CO)3(PPh3)2(4,4′-H15NdNC6H4-C6H4Nt15N)](BF4)2 (15b*).
These complexes were prepared exactly like the related compounds
13b and 15b using the labeled [4,4′-15NtNC6H4-C6H4Nt15N](BF4)2
bis(diazonium) salt; yield g70%.
[Mn(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (17b).
This compound was prepared by following the method used for the
related rhenium complex 13b by reacting MnH(CO)3(PPh2OEt)2 (0.34
mmol, 200 mg) with [4,4′-N2C6H4-C6H4N2](BF4)2 (0.34 mmol, 127
(20) Brunet, J. J.; Kindela, F. B.; Neibecker, D. Inorg. Synth. 1992, 29,
156.

3268 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
mg) in acetone at -196 °C. After crystallization from CH2Cl2/ethanol
(2/6 mL), the yield of the gummy orange product was about 75%. Anal.
Calcd for C43H39N4B2F8MnO5P2: C, 52.58; H, 4.00; N, 5.70. Found:
C, 52.75; H, 3.88; N, 5.86. ΛM ) 179.5 Ω-1 mol-1 cm2.
N)]2+ cations; yield g80%. Anal. Calcd for C116H140N4B2MnO18P6Re
(Mn17Re-b): C, 59.87; H, 6.06; N, 2.41. Found: C, 59.77; H, 6.15;
N, 2.48. ΛM ) 103.2 Ω-1 mol-1 cm2.
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)FeH-
{P(OEt)3}4](BPh4)2 (Re13Fe-b). A solution of [Re(CO)3(PPh2OEt)2-
(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (0.277 mmol, 308 mg) in 10 mL
of CH2Cl2 was cooled to -80 °C and quickly transferred by needle
into a 25-mL three-necked flask containing 200 mg (0.277 mmol) of
FeH2[P(OEt)3]4 cooled to -196 °C. The reaction mixture was brought
to room temperature and stirred for 4 h, and the solvent was then
removed under reduced pressure. The resulting oil was triturated with
3 mL of ethanol, giving a red-brown solution, from which the complex
was precipitated by adding an excess of NaBPh4 (1 mmol, 342 mg) in
2 mL of ethanol. After crystallization from a mixture of CH2Cl2 (2
mL) and ethanol (5 mL), the complex was filtered off and dried under
vacuum; yield g60%. Anal. Calcd for C115H141N4B2FeO17P6Re: C,
[Mn(CO)3(PPh2OEt)2(4,4′-H15NdNC6H4-C6H4Nt15N)](BF4)2
(17b*). This compound was prepared exactly like 17b using the labeled
[4,4′-15NtNC6H4-C6H4Nt15N](BF4)2 salt; yield g75%.
[Re(CO)3P2(µ-HNdNAr-ArNdNH)RuHP′4](BPh4)2 (Re13Ru-b,
Re13Ru-d, Re14Ru-b) [P ) PPh2OEt (Re13), PPh2OMe (Re14); P′ )
P(OEt)3; Ar-Ar ) 4,4′-C6H4-C6H4 (b), 4,4′-C6H4-CH2-C6H4 (d)]
and [Re(CO)4(PPh2OEt)(µ-4,4′-HNdNC6H4-C6H4NdNH)RuH-
{P(OEt)3}4](BPh4)2 (Re16Ru-b). The hydride RuH2[P(OEt)3]4 (0.13
mmol, 0.10 g) and the appropriate diazene-diazonium complex [Re-
(CO)5-nPn(HNdNAr-ArNtN)](BF4)2 (13, 14, 16) (0.13 mmol) were
placed in a 25-mL three-necked flask and cooled to -196 °C, after
which 10 mL of acetone was added. The reaction mixture was brought
to room temperature and stirred for about 2 h, and the solvent was
then removed under reduced pressure. The resulting oil was treated
with ethanol (5 mL) containing an excess of NaBPh4 (0.52 mmol, 178
mg), giving a red solid, which was filtered off and crystallized from a
mixture of CH2Cl2 (2 mL) and ethanol (7 mL); yield g70%. Anal.
Calcd for C115H141N4B2O17P6ReRu (Re13Ru-b): C, 58.87; H, 6.06; N,
2.39. Found: C, 58.99; H, 6.12; N, 2.50. ΛM ) 100.6 Ω-1 mol-1 cm2.
Anal. Calcd for C116H143N4B2O17P6ReRu (Re13Ru-d): C, 59.03; H, 6.11;
N, 2.37. Found: C, 58.88; H, 6.20; N, 2.37. ΛM ) 97.8 Ω-1 mol-1
cm2. Anal. Calcd for C113H137N4B2O17P6ReRu (Re14Ru-b): C, 58.55;
H, 5.96; N, 2.42. Found: C, 58.76; H, 6.04; N, 2.34. ΛM ) 103.1 Ω-1
mol-1 cm2. Anal. Calcd for C102H126N4B2O17P5ReRu (Re16Ru-b): C,
60.03; H, 6.18; N, 2.43. Found: C, 60.20; H, 6.24; N, 2.35. ΛM
)
104.1 Ω-1 mol-1 cm2.
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)Ru-
{P(OEt)3}4(µ-4,4′-HNdNC6H4-C6H4NdNH)Mn(CO)3(PPh2OEt)2]-
(BPh4)4 (Re13RuMn17). A solution of the diazene-diazonium complex
[Mn(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (17b) (0.25
mmol, 254 mg) in 10 mL of acetone was cooled to -80 °C and quickly
transferred into a 25-mL three-necked flask containing [Re(CO)3(PPh2-
OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)RuH{P(OEt)3}4](BPh4)2 (Re13Ru-
b) (0.25 mmol, 586 mg) in 10 mL of acetone cooled to -80 °C. The
reaction mixture was brought to room temperature and stirred for 8 h,
and the solvent was then removed under reduced pressure. The resulting
oil was triturated with ethanol (5 mL) containing an excess of NaBPh4
(0.50 mmol, 170 mg), affording a red-brown solid, which was filtered
off and crystallized from a mixture of CH2Cl2 (2 mL) and ethanol (7
mL); yield g60%. Anal. Calcd for C206H220N8B4MnO22P8ReRu: C,
65.23; H, 5.85; N, 2.95. Found: C, 65.39; H, 5.96; N, 2.87. ΛM ) 244
Ω-1 mol-1 cm2.
57.14; H, 5.92; N, 2.61. Found: C, 57.29; H, 5.98; N, 2.70. ΛM
)
100.1 Ω-1 mol-1 cm2.
[Re(CO)3(PPh2OEt)2(µ-4,4′-H15NdNC6H4-C6H4Nd15NH)-
RuH{P(OEt)3}4](BPh4)2 (Re13Ru-b*). This compound was prepared
like the related compound Re13Ru-b using the labeled [Re(CO)3-
(PPh2OEt)2(H15NdNC6H4-C6H4Nt15N)](BF4)2 derivative; yield g70%.
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)RuH-
{P(OEt)3}4](BPh4)2 (Mn17Ru-b). The complex was prepared like the
related complex Re13Ru-b by reacting RuH2P4 with [Mn(CO)3(PPh2-
OEt)2(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (17b) in acetone at -196
°C; yield g65%. Anal. Calcd for C115H141N4B2MnO17P6Ru: C, 62.36;
H, 6.42; N, 2.53. Found: C, 62.55; H, 6.55; N, 2.41. ΛM ) 107.5 Ω-1
mol-1 cm2.
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)Os-
{P(OEt)3}4(µ-4,4′-HNdNC6H4-C6H4NdNH)Mn(CO)3(PPh2OEt)2]-
(BPh4)4 (Re13OsMn17). This compound was prepared like the related
trinuclear Re13RuMn17 complex; yield g45%. Anal. Calcd for
C
206H220N8B4MnO22OsP8Re: C, 63.73; H, 5.71; N, 2.89. Found: C,
63.89; H, 5.83; N, 2.84. ΛM ) 235 Ω-1 mol-1 cm2.
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)Fe(4-
CH3C6H4CN){P(OEt)3}4](BPh4)3 (Mn17Fe1-b). In a 25-mL three-
necked flask were placed the hydride [FeH(4-CH3C6H4CN){P(OEt)3}4]-
BPh4 (0.2 mmol, 230 mg) and the diazene-diazonium complex
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NtN)](BF4)2 (17b) (0.2
mmol, 196 mg), and the mixture was cooled to -196 °C, after which
10 mL of acetone was added. The reaction mixture was brought to
room temperature and stirred for about 5 h, and the solvent was then
removed under reduced pressure. The resulting oil was triturated with
ethanol (5 mL) containing an excess of NaBPh4 (0.4 mmol, 137 mg).
A yellow solid slowly precipitated. This was filtered off and crystallized
from a mixture of CH2Cl2 (2 mL) and ethanol (5 mL); yield g60%.
Anal. Calcd for C147H167N5B3FeMnO17P6: C, 67.78; H, 6.46; N, 2.69.
Found: C, 67.63; H, 6.55; N, 2.60. ΛM ) 181.8 Ω-1 mol-1 cm2.
[Mn(CO)3(PPh2OEt)2(µ-4,4′-H15NdNC6H4-C6H4Nd15NH)Fe(4-
CH3C6H4CN){P(OEt)3}4](BPh4)3 (Mn17Fe1-b*). This compound was
prepared exactly like the related unlabeled complex Mn17Fe1-b starting
from the labeled [Mn(CO)3(PPh2OEt)2(µ-4,4′-H15NdNC6H4-C6H4Nt
15N)](BF4)2 (17b*) complex; yield g60%.
[Mn(CO)2(PPh2OEt)2(µ-4,4′-N2C6H4-C6H4N2)Fe{P(OEt)3}4]-
BPh4 (MnFe-b). An excess of NEt3 (0.5 mmol, 69 µL) was added to
a solution of [Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)-
Fe(4-CH3C6H4CN){P(OEt)3}4](BPh4)3 (Mn17Fe1-b) (0.1 mmol, 260 mg)
in 5 mL of CH2Cl2, and the reaction mixture was stirred for about 50
min. After filtration to remove the [NHEt3]BPh4 salt, the solution was
evaporated to dryness and the resulting oil triturated with 2 mL of
ethanol. The red-brown solid that slowly formed was filtered off and
crystallized from a mixture of CH2Cl2 (2 mL) and ethanol (5 mL);
yield g60%. Anal. Calcd for C90H118N4BFeMnO16P6: C, 59.42; H, 6.54;
N, 3.08. Found: C, 59.56; H, 6.64; N, 3.00. ΛM ) 52.6 Ω-1 mol-1
cm2.
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)OsHP′4]-
(BPh4)2 (Re13Os-b, Re13Os1-b) [P′ ) P(OEt)3 (Os), PPh(OEt)2 (Os1)]
and [Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)OsH-
{P(OEt)3}4](BPh4)2 (Mn17Os-b). These heterobinuclear complexes
were prepared like the related complex Re13Ru by reacting the hydride
OsH2P4 with the appropriate diazene-diazonium [M(CO)3P2(4,4′-HNd
NC6H4-C6H4NtN)](BF4)2 (M ) Re, Mn) derivatives; yield g65%.
Anal. Calcd for C115H141N4B2O17OsP6Re (Re13Os-b): C, 56.72; H, 5.84;
N, 2.30. Found: C, 56.65; H, 5.95; N, 2.24. ΛM ) 104.3 Ω-1 mol-1
cm2. Anal. Calcd for C131H141N4B2O13OsP6Re (Re13Os1-b): C, 61.38;
H, 5.54; N, 2.19. Found: C, 61.57; H, 5.68; N, 2.27. ΛM ) 102.8 Ω-1
mol-1 cm2. Anal. Calcd for C115H141N4B2MnO17OsP6 (Mn17Os-b): C,
59.95; H, 6.17; N, 2.43. Found: C, 60.12; H, 6.28; N, 2.35. ΛM
)
99.6 Ω-1 mol-1 cm2.
[Re(CO)3P2(µ-4,4′-HNdNC6H4-C6H4NdNH)Mn(CO)3P′2]-
(BPh4)2 (Re13Mn-b, Re15Mn-b) [P ) PPh2OEt (Re13), PPh3 (Re15);
P′ ) PPh(OEt)2]. These complexes were prepared according to the
general method, by reacting the hydride MnH(CO)3P′2 with the
appropriate [Re(CO)3P2(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 com-
plexes in acetone; yield g70%. Anal. Calcd for C114H110N4B2MnO12P4-
Re (Re13Mn-b): C, 64.75; H, 5.24; N, 2.65. Found: C, 64.93; H, 5.38;
N, 2.57. ΛM ) 112.5 Ω-1 mol-1 cm2. Anal. Calcd for C122H110N4B2-
MnO10P4Re (Re15Mn-b): C, 67.25; H, 5.09; N, 2.57. Found: C, 67.33;
H, 5.12; N, 2.67. ΛM ) 108.7 Ω-1 mol-1 cm2.
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)Re(CO)-
{P(OEt)3}4](BPh4)2 (Mn17Re-b) and [Mn(CO)3(PPh2OEt)2(µ-4,4′-
H15NdNC6H4-C6H4Nd15NH)Re(CO){P(OEt)3}4](BPh4)2 (Mn17Re-
b*). These complexes were also prepared according to the general
method, by reacting ReH(CO)[P(OEt)3]4 with the unlabeled and labeled
diazene-diazonium [Mn(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4Nt

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3269
Table 1. Crystal Data and Structure Refinement Details for
[Re(C6H5NdNH)(CO){P(OEt)3}4]BPh4 (1a)
showed no significant features. All calculations were performed on a
Digital Alpha 255 workstation at the Centro di Studio per la Struttur-
istica Diffrattometrica del CNR in Parma. The final geometry was
analyzed with the program PARST97,23 and the drawing of the structure
was made with ZORTEP.24
empirical formula
fw
C55H86BN2O13P4Re
1304.15
20(2)
temp (°C)
Electrochemical Apparatus and Procedures. Voltammetric experi-
ments were carried out in a three-electrode cell. The working electrode
was a glassy-carbon (area 0.2 cm2) or platinum disk (area 0.07 cm2),
mirror-polished with graded alumina powder. The voltammetric patterns
of the tested compounds showed similar characteristics on both Pt and
glassy-carbon electrodes (apart from large peak current values, which
are on scale with respect to electrode area). All data presented here
were obtained using a glassy-carbon disk as the working electrode.
The working electrode was surrounded by a platinum spiral counter
electrode. The reference electrode (aqueous KCl-saturated Ag/AgCl)
was placed in a Luggin capillary reference electrode compartment.
All potentials are referred to this Ag/AgCl reference electrode. The
E1/2 value for the ferrocene/ferrocenium (Fc/Fc+) couple, measured
in the supporting electrolyte used in this work, (0.1 M tetrabutylam-
monium hexafluorophosphate, TBAH, in dichloroethane, DCE) was
+0.520 V vs Ag/AgCl. The specific resistance of the electrolyte solu-
tion, measured with a Crison CM 2202 conductometer, was 1250 Ω
cm. All measurements were carried out at room temperature under a
nitrogen atmosphere. The voltammetric equipment used was an EG&G
PAR Model 273 potentiostat controlled by a personal computer via M
270 software, using a positive feedback correction of uncompensated
IR drops.
wavelength (Å)
crystal system, space group
unit cell dimensions (Å; deg)
0.710 69
triclinic, P1h
a ) 15.380(5), b ) 13.037(5),
c ) 16.649(5), R ) 90.33(5),
â ) 91.2(1), γ ) 89.71(9)
3337(2)
2, 1.298
19.71
R1 ) 0.0384, wR2 ) 0.0811
R1 ) 0.0970, wR2 ) 0.0970
volume (Å3)
Z, calcd density (g/cm3)
abs coeff (cm-1
)
final R indices [I > 2σ(I)]a
R indices (all data)
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑[w(Fo2 - Fc2)2]/∑[w(Fo2)2]}1/2
;
2
2
w ) 1/{σ2(Fo ) + [0.17(2Fc2 + Fo )/3]2}.
[Mn(CO)2(PPh2OEt)2(µ-4,4′-15NtNC6H4-C6H4Nt15N)Fe-
{P(OEt)3}4]BPh4 (MnFe-b*). This compound was prepared exactly
like the related unlabeled complex MnFe-b by deprotonation with NEt3
of the labeled [Mn(CO)3(PPh2OEt)2(µ-4,4′-H15NdNC6H4-C6H4Nd15-
NH)Fe(4-CH3C6H4CN){P(OEt)3}4](BPh4)3 (Mn17Fe1-b*) derivative;
yield g60%.
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NtN)Fe(CO)2-
{P(OPh)3}2](BPh4)2 (Re13Fe2). A solution of [Re(CO)3(PPh2OEt)2(4,4′-
HNdNC6H4-C6H4NtN)](BF4)2 (0.277 mmol, 308 mg) in 10 mL of
acetone was cooled to -80 °C and quickly transferred by a cannula
into a 25-mL three-necked flask containing 203 mg (0.277 mmol) of
FeH2(CO)2[P(OPh)3]2 cooled to -196 °C. The reaction mixture was
brought to room temperature and stirred for about 20 h, and the solvent
was then removed under reduced pressure. The resulting oil was
triturated with 3 mL of ethanol, giving a red-brown solution, from which
the complex was precipitated by adding an excess of NaBPh4 (0.8 mmol,
274 mg) in 2 mL of ethanol. After crystallization from a mixture of
CH2Cl2 (2 mL) and ethanol (5 mL), the gummy solid obtained was
filtered off and dried under vacuum; yield g55%. Anal. Calcd for
C129H109N4B2FeO13P4Re: C, 67.05; H, 4.75; N, 2.42. Found: C, 67.31;
H, 4.73; N, 2.34. ΛM ) 105.1 Ω-1 mol-1 cm2.
Digital simulations of experimental voltammograms were performed
with Digisim 2.1 (Bas Inc.), a cyclic voltammetric simulation program,
running on an HP 735/90 CPU Pentium computer. The voltammograms
of the binuclear compounds were simulated by the following reaction
sequence, where A is the starting binuclear compound:
A + e ) B
B ) C
(1)
(2)
(3)
C + e ) D
D ) E
(4)
X-ray Structure Determination of [Re(C6H5NdNH)(CO){P-
(OEt)3}4]BPh4 (1a). Suitable crystals for X-ray analysis were obtained
by recrystallization from ethanol. The data were collected at room
temperature on a Philips PW 1100 diffractometer using graphite-mono-
chromatized Mo KR radiation. Despite the values of the angles, all
near 90°, a cell reduction program failed to show the presence of a
higher symmetry, and the choice of the triclinic centric space group
P1h was justified by the intensity distribution statistics and the
satisfactory refinement of the structure. No crystal decay was observed.
Pertinent crystallographic parameters are summarized in Table 1. The
data were processed with a peak-profile procedure and corrected for
Lorentz and polarization as well as for absorption effects, using the
ψ-scan method. A total of 19 477 reflections ((h,(k,+l) were measured
by using the θ-2θ scan technique to a maximum 2θ value of 60°.
The structure was solved by direct methods21 and refined by a full-
matrix least-squares procedure on F2 with SHELXL97.22 All non-
hydrogen atoms were refined with anisotropic thermal parameters.
Hydrogen atoms were inserted at calculated positions using a riding
model, with the exception of the hydrogen belonging to the nitrogen
in the phenyldiazene group, which was detected in a ∆F map and
refined freely. Phenyl groups of the anion were refined as rigid bodies.
Neutral-atomic scattering factors were employed, and anomalous
dispersion terms were included for non-hydrogen atoms. The refinement
for 653 parameters converged with R1 ) 0.0384 (for 10 297 observed
data), wR2 ) 0.0970, and GOF ) 0.829. The final difference map
The voltammograms of the relevant mononuclear compounds were
simulated by a similar mechanism from which, however, reactions 3
and 4 were excluded. For all the compounds studied in this work, the
fits between simulated and experimental data were optimized using
the simulation parameters listed in Table 2. For digital simulation of
the oxidation of mono- and binuclear Mn aryldiazenido compounds,
the following mechanism was adopted:
B + e ) A
C + e ) B
(5)
(6)
where A was always the starting complex; reaction 6 was excluded in
the case of the mononuclear compound. The fits between simulated
and experimental data were optimized by the simulation parameters
listed in Table 3.
Although a positive feedback correction of the ohmic drop of the
solution was used to obtain the experimental data, slightly better fits
between experimental and simulated voltammograms were achieved
by introducing a residual uncompensated resistance of 200 Ω in the
simulations. A double-layer capacitance of 5 × 10-6 farad was
employed.
Results and Discussion
Aryldiazene Complexes. The rhenium hydride complexes
ReH(CO)5-nPn quickly react with both mono- and bis(aryl-
diazonium) cations to give the aryldiazene derivatives [Re-
(21) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G.; Polidori, G.; Spagna, R. Sir97:
A new program for solVing and refining crystal structures; Istituto di
Ricerca per lo Sviluppo di Metodologie Cristallografiche, CNR: Bari,
Italy, 1997.
(23) Nardelli, M. PARST97, updated version of PARST95. J. Appl.
Crystallogr. 1995, 28, 659.
(22) Sheldrick, G. M. SHELXL97: Program for structure refinement;
University of Goettingen: Goettingen, Germany, 1997.
(24) Zsolnai, L.; Pritzkow, H. ZORTEP: ORTEP original program modified
for PC; University of Heidelberg: Heidelberg, Germany, 1994.

3270 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
Table 2. Fitting Parameters Used in the Digital Simulations of the Reductions of Selected Aryldiazene Complexesa
E°(1)
ks(1)
kf(2) E°(3)
Keq(2) (s-1 (V) R(3) (cm s-1
103ks(3)
kf(4) 106D(A) 106D(B) 106D(C) 106D(D) 106D(E)
Keq(4) (s-1) (cm2 s-1) (cm2 s-1) (cm2 s-1) (cm2 s-1) (cm2 s-1
)
cmpd
(V) R(1) (cm s-1
)
)
)
5a
11b
-0.79 0.2 0.005
-0.70 0.37 0.017
0.002
300
30
500
100
2.0
2.4
2.0
1.5
1.0
1.2
2.0
2.4
1.8
1.0
1.0
1.8
2.0
2.4
2.0
1.0
1.0
8.0
400 -0.83 0.22
100 -1.24 0.3
100
9
5
3 × 105 100
3 × 104 500
2.0
2.0
2.0
2.0
Re13Ru-b -0.66 0.2
Mn1
Mn2
-0.89 0.2
-0.73 0.2
0.0015 300
0.001
300
1
-0.95 0.2
1
3
3 × 104 150
1.0
8.0
1.0
8.0
Mn17Ru-b -0.85 0.2
0.0012 3 × 105 100 -1.24 0.3
3 × 104 500
a R ) transfer coefficient, ks ) standard heterogeneous rate constant, D ) diffusion coefficient, and the other symbols have their usual meanings.
Mn1 ) [Mn(C6H5NdNH)(CO)3(PPh2OEt)2]BF4; Mn2 ) [{Mn(CO)3(PPh2OEt)2}2(µ-4,4′-HNdNC6H4-C6H4NdNH)](BPh4)2.3b
Table 3. Fitting Parameters Used in the Digital Simulations of the Oxidations of Aryldiazenido Compounds of Manganese
E°(5)
(V)
104ks(5)
E°(6)
(V)
104ks(6)
106D(A)
106D(B)
106D(C)
(cm2 s-1
)
cmpd
R(5)
(cm s-1
)
R(6)
(cm s-1
)
(cm2 s-1
)
(cm2 s-1
)
Mn3
Mn4
0.425
0.44
0.4
0.35
1.5
1.5
6.5
5
6.5
5
0.48
0.35
2.0
5
a Mn3 ) Mn(C6H5N2)(CO)2(PPh2OEt)2; Mn4 ) {Mn(CO)2(PPh2OEt)2}2(µ-4,4′-N2C6H4-C6H4N2).3b
Scheme 1a
Scheme 2a
a P ) P(OEt)3 (1, 3), PPh(OEt)2 (4), PPh2OEt (2, 5).
(PhNdNH)(CO)5-nPn]+ (1-5) and [{Re(CO)5-nPn}2(µ-
HNdNAr-ArNdNH)]2+ (6-12), which were isolated as BF4
-
-
or BPh4 salts and characterized (Schemes 1 and 2).
An exact stoichiometric ratio between the reagents and the
start of the reaction at low temperature seems to be crucial for
successful synthesis of the aryldiazene derivatives. Otherwise,
some decomposition products or oily substances were found in
the final reaction products.
P ) P(OEt)3 (6, 9), PPh(OEt)2 (7, 10), PPh2OEt (8, 11, 12); Ar-Ar
) 4,4′-C6H4-C6H4 (b), 4,4′-(2-CH3)C6H3-C6H3(2-CH3) (c), 4,4′-
C6H4-CH2-C6H4 (d).
Good analytical data were obtained for all the aryldiazene
complexes, which are yellow or orange solids and are stable in
air and in solutions of polar organic solvents, where they behave
as 1:1 or 2:1 electrolytes.25 The IR and NMR data (Table 4)
support the proposed formulations and allow geometries in
solution to be established for all the complexes (Schemes 1 and
2). In particular, the presence of the diazene ligand was
In the temperature range between +30 and -80 °C, the 31P
NMR spectra of the monocarbonyl complexes 1 and 6 appeared
as sharp singlets, indicating the magnetic equivalence of the
four phosphite ligands, whereas the IR spectra showed only one
ν(CO) band. On this basis, the mutual trans positions of the
diazene and carbonyl ligands may be proposed.
For both the mononuclear dicarbonyl complexes 2 and the
binuclear dicarbonyl complexes 7 and 8, the IR spectra showed
two strong ν(CO) bands, suggesting a cis arrangement of the
1
confirmed by the H NMR spectra, which showed the charac-
teristic NH proton signal as a broad resonance at 14.51-12.21
ppm. For the related labeled compounds 4a*, 4a**, 8b*, and
1
15NH
11b*, this signal was split into a sharp doublet with J
)
2
15
62-66 Hz and J NH ) 3.5 Hz, in agreement with the proposed
formulations.1,2,26 The 15N NMR spectra of labeled compounds
8b* and 11b* further support the assignments, showing a
doublet of triplets for the 15NH resonance (Table 5) due to
coupling with the proton and phosphorus nuclei.
(25) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.
(26) (a) Laing, K. R.; Robinson, S. D.; Uttley, M. F. J. Chem. Soc., Dalton
Trans. 1973, 2713. (b) Carrol, J. A.; Sutton, D.; Xiaoheng, Z. J.
Organomet. Chem. 1982, 244, 73.

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3271
Table 4. IR and NMR Data for Selected Mono-, Bi-, and Trinuclear Complexesa
IR(KBr)
1H NMRb,c
spin
31P{1H} NMRb,d
δ (ppm; J, Hz)
compd
ν (cm-1
)
assgnt
δ (ppm; J, Hz)
assgnt
NH
system
1a
2a
[Re(C6H5NdNH)(CO){P(OEt)3}4]BPh4
1903 (s)
ν(CO)
14.37 (qi)
JPH ) 4
A4
116.4 (br)
[117.6 (s)]e
4.04 (m)
1.26 (t)
12.21 (d)
3.34 (m)
0.84 (t)
CH2
CH3
NH
CH2
CH3
f
[Re(C6H5NdNH)(CO)2(PPh2OEt)3]BF4
1968 (s)
1889 (s)
ν(CO)
AB2
δA ) 115.5
δB ) 108.8
JAB ) 28
0.65 (t)
14.30 (s, br)g
3.97 (m)
1.24 (t)
NH
CH2
CH3
NH
A2
136.0 (s)
g
4a
[Re(C6H5NdNH)(CO)3{PPh(OEt)2}2]BF4
[Re(C6H5Nd15NH)(CO)3{PPh(OEt)2}2]BF4
2072 (m) ν(CO)
1979 (s)
1960 (s)
2078 (m) ν(CO)
1979 (s)
1960 (s)
[137.9 (s)]e
4a*
14.31 (d)g
A2Xe,g
137.8 (d)
J
NH ) 63
2J N ) 2.5
15
31P15
3.98 (m)
1.24 (t)
CH2
CH3
NH
CH2
CH3
NH
CH2
CH3
NH
CH2
CH3
5a
[Re(C6H5NdNH)(CO)3(PPh2OEt)2]BF4
2071 (m) ν(CO)
1979 (s)
1948 (s)
12.55 (s)
3.65 (m)
1.18 (t)
13.46 (s)
3.67 (m)
1.22 (t)
12.78 (s)
3.70 (qi)
1.21 (t)
A2
A2
A
110.9 (s)
110.5 (s)
106.3 (s)
11b
12b
[{Re(CO)3(PPh2OEt)2}2(µ-4,4′-HNdNC6H4- 2075 (m) ν(CO)
C6H4NdNH)](BF4)2
1981 (s)
1925 (s)
2115 (m) ν(CO)
2033 (s)
2017 (s)
[{Re(CO)4(PPh2OEt)}2(µ-4,4′-HNdNC6H4-
C6H4NdNH)](BPh4)2
1980 (s)
13b
[Re(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-
C6H4NtN)](BF4)2
2266 (m) ν(NtN) 13.70 (s)
NH
A2
110.4 (s)
2071 (m) ν(CO)
1979 (s)
1942 (s)
13.55 (s)
3.64 (qi)
1.22 (t)
CH2
CH3
NH
13b*
[Re(CO)3(PPh2OEt)2(4,4′-H15NdNC6H4-
C6H4Nt15N)](BF4)2
2232 (m) ν(NtN) 13.71 (d)
A2X
110.6 (s, br)
2072 (m) ν(CO)
1979 (s)
1942 (s)
13.54 (d)
15
J
NH ) 66
3.64 (br)
1.21 (br)
CH2
CH3
NH
h
17b
[Mn(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-
C6H4NtN)](BF4)2
2265 (m) ν(NtN) 13.11 (s)
A2 + A2
161.9 (s, br)
2061 (m) ν(CO)
1984 (s)
1952 (s)
2072 (m) ν(CO)
1978 (s)
1943 (s)
12.95 (s)
3.58 (br)
1.20 (br)
13.98 (s, br)
12.72 (s)
12.68 (s)
4.05 (m)
3.62 (q)
1.30 (t)
CH2
CH3
NH, Ru
NH, Re
Re13Ru-b
[Re(CO)3(PPh2OEt)2(µ-4,4′-HN)NC6H4-
C6H4NdNH)RuH{P(OEt)3}4](BPh4)2
A2 + A2
109.8 (s), Re
109.6 (s)
AB2C
δA ) 149.5, Ru
δB ) 141.7
δC ) 136.7
JAB ) 62.0
JAC ) 41.5
JBC ) 43.0
CH2
CH3
1.26 (t)
1.24 (t)
1.19 (t)
-6.89 to
-7.90 (m)
13.99 (d)
12.71 (d)
12.66 (d)
4.05 (m)
3.62 (qi)
1.30 (t)
H, hydride
Re13Ru-b* [Re(CO)3(PPh2OEt)2(µ-4,4′-H15NdNC6H4-
C6H4Nd15NH)RuH{P(OEt)3}4](BPh4)2
2071 (m) ν(CO)
1978 (s)
1941 (s)
NH, Ru
NH, Re
A2X + A2X 109.8 (s, br) Re
AB2CX
δA ) 149.5, Ru
δB ) 141.6
δC ) 136.7
JAB ) 62.6
JAC ) 41.7
JAX ) 52.4
JBC ) 43.0
JBX ) 4.6
CH2
CH3
1.26 (t)
1.23 (t)
1.19 (t)
-6.88 to
-7.89 (m)
14.14 (s, br)g
14.06 (s)
13.98 (s)
4.27 (br)
4.08 (br)
3.70 (qi)
1.34 (t)
H, hydride
JCX ) 3.8
Mn17Ru-b
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)RuH{P(OEt)3}4](BPh4)2
2060 (m) ν(CO)
1981 (s)
1954 (s)
NH, Ru
NH, Mn
A2 + A2
162.6 (s, br), Mn
δA ) 151.6, Ru
δB ) 145.0
δC ) 137.4
JAB ) 61.3
JAC ) 41.5
JBC ) 41.0
AB2Cg
CH2
CH3
1.30 (t)
1.26 (t)
1.22 (t)
-6.76 to
-7.70 (m)
H, hydride

3272 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
Table 4 (Continued)
IR(KBr)
1H NMRb,c
spin
31P{1H} NMRb,d
δ (ppm; J, Hz)
compd
ν (cm-1
)
assgnt
ν(CO)
δ (ppm; J, Hz)
assgnt
system
Re13Os-b
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)OsH{P(OEt)3}4](BPh4)2
2071 (m)
1978 (s)
1947 (s)
14.61 (s, br)
12.59 (s)
12.54 (s)
NH, Os
NH, Re
A2 + A2
109.7 (s), Re
109.5 (s)
[110.7 (s)
[12.60 (s)
110.5 (s)]i
12.53 (s)]i
A2BC
δA ) 103.9, Os
δB ) 101.2
δC ) 100.4
JAB ) 47.3
JAC ) 29.6
JBC ) -32.7
4.17-3.94 (m) CH2
3.64 (m)
1.30 (t)
1.23 (t)
1.20 (t)
-8.32 to
CH3
H, hydride
NH, Re
-8.82 (m)
Re13Mn-b
Mn17Re-b
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)Mn(CO)3{PPh(OEt)2}2](BPh4)2
2064 (w)
1978 (s, br)
1950 (s, br)
ν(CO)
12.75 (s)
12.73 (s)
12.55 (s)
4.09 (br)
3.65 (m)
1.37 (t)
A2
186.6 (s), Mn
[187.6 (s)]i
NH, Mn
CH2
A2 + A2
109.7 (s, br), Re
[110.8 (s, br)]i
CH3
1.18 (t br)
14.47 (br)
12.47 (br)
4.06 (m)
3.60 (m)
1.30 (m br)
14.12 (br)
12.85 (s)
12.73 (s)
12.51 (s)
12.39 (s)
4.05 (m)
3.62 (m)
1.30 (m)
1.18 (m)
14.62 (br)
12.92 (s)
12.91 (s)
12.56 (s)
12.42 (s)
4.10 (m)
3.62 (m)
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)Re(CO){P(OEt)3}4](BPh4)2
2060 (m)
1981 (s)
1954 (s)
1865 (s)
ν(CO), Mn
ν(CO), Re
NH, Re
NH, Mn
CH2
A2 + A2
161.4 (s, br), Mne
123.6 (s), Re
A4
CH3
NH, Ru
NH, Mn
Re13RuMn17 [Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
2060 (m, br) ν(CO)
A2 + A2
A2 + A2
160.7 (br), Mn
110.0 (s), Re
109.9 (s)
δA ) 126.5, Ru
δB ) 116.7
JAB ) 61.5
C6H4NdNH)Ru{P(OEt)3}4(µ-4,4′-HNdNC6H4- 1980 (s, br)
C6H4NdNH)Mn(CO)3(PPh2OEt)2](BPh4)4
1947 (s, br)
NH, Re
CH2
A2B2
CH3
Re13OsMn17 [Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)Mn(CO)3(PPh2OEt)2](BPh4)4
2071 (m, br) ν(CO)
NH, Os
NH, Mn
A2 + A2
A2 + A2
A2BC
160.8 (br), Mn
109.9 (s, br), Re
δA ) 102.8, Os
δB ) 101.0
C6H4NdNH)Os{P(OEt)3}4(µ-4,4′-HNdNC6H4- 1980 (s, br)
1948 (s, br)
NH, Re
CH2
δC ) 100.5
JAB ) 31.0
JAC ) 45.5
1.37-1.15 (m) CH3
4.05 (br)
3.69 (br)
JBC ) 29.8
MnFe-b
[Mn(CO)2(PPh2OEt)2(µ-4,4′-N2C6H4-
C6H4N2)Fe{P(OEt)3}4]BPh4
1931 (s)
1853 (s)
1653 (m)
1617 (m)
1560 (m)
1585 (m)
ν(CO)
CH2
A2 +
174.1 (s), Mn
h
ABC2 δA ) 169.2, Fe
ν(NtN), Fe 1.30 (br)
CH3
δB ) 166.8
δC ) 152.6
ν(NtN), Mn
JAB ) -3.75
JAC ) 122.5
ν′(NtN), Mn
JBC ) 126.3
MnFe-b*
Re13Fe2
[Mn(CO)2(PPh2OEt)2(µ-4,4′-15NtNC6H4-
C6H4Nt15N)Fe{P(OEt)3}4]BPh4
1931 (s)
1854 (s)
1604 (m)
1580 (m)
1541 (m)
1558 (m)
2073 (m)
1978 (s)
1944 (s)
2054 (m)
2000 (sh)
1752 (m)
ν(CO)
4.05 (br)
3.70 (br)
ν(NtN), Fe 1.31 (br)
CH2
CH3
A2X +
ABC2X 170-150 (m), Fe
174.7 (s, br), Mn
ν(NtN), Mn
ν′(NtN), Mn
ν(CO), Re
[Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4N2)Fe(CO)2{P(OPh)3}2](BPh4)2
14.37 (br)g
3.78 (m)
1.21 (t)
NH
CH2
CH3
A2 + A2
145.9 (s), Re
111.0 (s, br), Fe
g
A2
ν(CO), Fe
ν(NtN)
a IR and NMR data for all the prepared complexes are reported in Table S1 (Supporting Information). b In CD2Cl2 at 25 °C unless otherwise
f 13
1
noted. c Phenyl proton resonances are omitted. d Positive shift downfield from 85% H3PO4. e At -90 °C. C{ H} NMR, δ: 202.2 (dt, J
)
13
CP
) 8.5 Hz, CO), 193.7 (dt, J
) 8.2, J
) 67 Hz, CO), 135-120 (m, Ph), 65.35 (d), 64.95 (t), (CH2), 15.8 (t), 15.5 (d) (CH3).cigs In
13
J
13
13
CP
CP
cis
CP
trans
(CD3ci)s2CO. h At -30 °C. i At -70 °C.
two carbonyl ligands. However, these two ligands are not
magnetically equivalent, as shown by the two well-separated
multiplets due to the carbonyl carbon atom that appear at 202.2
(dt) and 193.7 (dt) ppm in the 13C NMR spectrum of
[Re(C6H5NdNH)(CO)2(PPh2OEt)3]BF4 (2a). Furthermore, the
31P{1H} NMR spectra appear as an AB2 multiplet, suggesting
a mer-cis geometry for the dicarbonyl derivatives.
The IR spectra of complexes 3, 4, 5, 9, 10, and 11, containing
the tricarbonyl fragment Re(CO)3P2, showed three bands (one
medium and two of strong intensity) in the ν(CO) region,
indicating a mer rearrangement of the three carbonyl ligands.
In the temperature range between +30 and -80 °C, the 31P-
{1H} NMR spectra consisted of sharp singlets, indicating the
magnetic equivalence of the two phosphite ligands. On this basis,

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3273
Table 5. 15N NMR Data for Selected Labeled Complexesa
compd
δ
b (ppm; J, Hz)
-11.5 (dt)
assgnt
15NH
8b*
[{Re(CO)2(PPh2OEt)3}2(µ-4,4′-H15NdN-C6H4-C6H4-Nd15NH)](BPh4)2
[{Re(CO)3(PPh2OEt)2}2(µ-4,4′-H15NdN-C6H4-C6H4-Nd15NH)](BF4)2
[Re(CO)3(PPh2OEt)2(4,4′-H15NdN-C6H4-C6H4-Nt15N)](BF4)2
2
1
15
J
J
NP ) 4
15
NH ) 62
11b*
13b*
-17.6 (dt)
15NH
15NH
2
1
15
J
J
NP ) 4
NH ) 66
15
-8.3 (d, br)
-16.6 (d, br)
15
J
NH ) 66
-70.0 (s)
Nt15N
15b*
[Re(CO)3(PPh3)2(4,4′-H15NdN-C6H4-C6H4-Nt15N)](BF4)2
-15.0 (d)
15NH
-20.0 (d)
15
J
NH ) 66
-70.0 (s)
16.8 (d, br)
Nt15N
17b*
[Mn(CO)3(PPh2OEt)2(4,4′-H15NdNC6H4-C6H4Nt15N)](BF4)2
[Mn(CO)2(PPh2OEt)2(µ-4,4′-15NtNC6H4-C6H4Nt15N)Fe{P(OEt)3}4]BPh4
15NH
11.6 (d, br)
15
J
NH ) 65
-70.0 (s)
Nt15N
MnFe-b*
58.0 (t)
Mn15NtN
15
J
NP ) 13
27.0 (m, br)
Fe15NtN
a In CD2Cl2 at 25 °C. b Positive shift downfield from CH315NO2.
a mer-trans geometry of the type in Schemes 1 and 2 may be
proposed for the tricarbonyl compounds. It may also be noted
that exclusively mer-trans complexes were obtained by reacting
both mer-trans and fac-cis isomers of the ReH(CO)3P2 hydride
precursors prepared in the case of the PPh2OEt ligand.
Finally, mutual cis positions for the phosphite and diazene
ligands of the tetracarbonyl [{Re(CO)4(PPh2OEt)2}2(µ-4,4′-
HNdNC6H4-C6H4NdNH)](BPh4)2 (12b) complex may be
proposed on the basis of the presence of four ν(CO) bands in
the infrared spectra.
A comparison of these results for rhenium aryldiazene
complexes with those previously reported by us for related
manganese derivatives3b showed that, in both cases, aryldiazene
complexes can be obtained by “apparent” insertions of aryl-
diazonium cations into the M-H bonds of the monohydride
species MH(CO)5-nPn (M ) Mn, Re) containing phosphites as
ancillary ligands. However, whereas stable diazene complexes
of rhenium can be obtained for all CO:P ratios in the
[Re(ArNdNH)(CO)5-nPn]+ (n ) 1-4) complexes, only the
tricarbonyl fragment Mn(CO)3P2 allowed stable aryldiazene
derivatives to be prepared. Furthermore, the [Mn(ArNdNH)-
(CO)3P2]+ cations can easily be deprotonated with NEt3,
affording aryldiazenido Mn(ArN2)(CO)2P2 derivatives, in agree-
ment with eq 7. Surprisingly, no reaction [as in (8)] was
Figure 1. ORTEP view of the cation [Re(C6H5NdNH)(CO)-
{P(OEt)3}4]+ (1a+) with thermal ellipsoids drawn at the 50% probability
level. Ethyl groups of phosphite ligands are omitted for clarity.
CO or one phosphite ligand may explain the different behaviors
of the aryldiazene complexes of the two metals.
X-ray Crystal Structure of 1a. The crystal structure of 1a
consists of discrete [Re(C6H5NdNH)(CO){P(OEt)3}4]+ cations
and BPh4- anions, which interact only by means of electrostatic
and dispersive forces. The complex cation showing the atom-
labeling scheme used is depicted in Figure 1. Selected bond
distances and angles are given in Table 6. The coordination
polyhedron is a distorted octahedron in which the rhenium atom
is coordinated by four phosphite groups, one phenyldiazene
molecule, and one carbonyl group, the two last ligands being
mutually trans. The angles in the coordination sphere range
from 169.91(3) to 176.24(4)° (trans) and from 82.7(1) to 97.6-
(1)° (cis). The orientation of the phosphite groups containing
P1 and P4 is determined by an intramolecular bifurcated
hydrogen bond involving two ethoxy oxygens and the hydrazidic
-NH: N1-H‚‚‚O2 (2.924(5) Å, 108(3)°) and N1-H‚‚‚O12
(2.902(4) Å, 120(3)°). This compound is the first case in which
the structure of the Re-NHdN-Ph system has been deter-
mined.
[Mn(ArNdNH)(CO)3P2]+ + NEt3 f
Mn(ArN2)(CO)2P2 + CO + [NHEt3]+ (7)
[Re(ArNdNH)(CO)5-nPn]+ + excess NEt3 N
(8)
observed when the related rhenium aryldiazene complexes 1-12
were treated with base. The starting [Re]-NHdNAr compound,
in fact, could be recovered unchanged even after 10-12 h of
reaction with an excess of NEt3 at room temperature, whereas
longer reaction times or reflux conditions only caused decom-
position of the aryldiazene derivative. This unreactivity was
rather unexpected in view of the known properties of aryldiazene
complexes3,17 and may be explained by taking into account eq
7, which involves deprotonation of ArNdNH and concurrent
dissociation of one ligand, affording a pentacoordinate Mn(-
I) aryldiazenido derivative. In agreement with this path, the
probable reluctance of the rhenium complexes to dissociate one
Like that of the phenyldiazene ligand, this structure may be
compared with the structure of the similar complex3b [Mn(CO)3-
(4-CH3C6H4NdNH){PPh(OEt)2}2]+, in which the metal envi-

3274 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
Scheme 4a
Table 6. Selected Bond Distances (Å) and Angles (deg) for
[Re(C6H5NdNH)(CO){P(OEt)3}4]+ (1a+)
Distances
Re-C1
Re-N1
Re-P1
Re-P2
Re-P3
1.887(5)
2.136(4)
2.370(1)
2.372(2)
2.368(1)
Re-P4
2.366(2)
1.180(4)
1.229(4)
1.424(5)
O13-C1
N1-N2
N2-C2
Angles
C1-Re-N1
C1-Re-P4
N1-Re-P4
C1-Re-P3
N1-Re-P3
P4-Re-P3
C1-Re-P1
N1-Re-P1
P4-Re-P1
175.6(1)
89.6(1)
86.1(1)
93.2(1)
87.8(1)
87.82(9)
96.1(1)
82.7(1)
88.30(9)
P3-Re-P1
C1-Re-P2
N1-Re-P2
P4-Re-P2
P3-Re-P2
P1-Re-P2
N2-N1-Re
N1-N2-C2
O13-C1-Re
169.91(3)
86.7(1)
97.6(1)
176.24(4)
92.86(9)
91.61(9)
135.4(3)
118.6(3)
178.6(3)
Scheme 3
ronment consists of two phosphite ligands trans to each other,
three carbonyl groups, and one p-tolyldiazene moiety, and with
the structure of chlorodicarbonyl(cis-phenyldiazene)bis(tri-
phenylphosphine)ruthenium(1+).5k The structural parameters of
the Re-NHdN-C system (Re-N ) 2.136(4), N-N ) 1.229-
(4), N-C ) 1.424(5) Å; Re-N-N ) 135.4(3), N-N-C )
118.6(3)°) agree with sp2 hybridization for both N atoms. In
the aryldiazene ligand of the above-mentioned Mn derivative,
the distances are slightly longer (N-N ) 1.263(10), N-C )
1.438(11) Å) and the bond angles more regular (Mn-N-N )
125.1(5), N-N-C ) 119.8(7)°). The geometry of the Ru
complex (N-N ) 1.218, N-C ) 1.409 Å; Ru-N-N ) 129,
N-N-C ) 118°), is not significantly different from that of
the Re compound, apart from the M-N-N angle. It is in-
teresting to compare the geometry of Re-NHdN-Ph with that
of the Re-NdNH-Ph system found in dibromo(phenyldiaz-
enido)(phenylhydrazido)bis(triphenylphosphine)rhenium,27 where
the shift of the proton from N1 to N2 produces shortening of
the Re-N bond (1.922 Å) and lengthening of the N-N bond
(1.276 Å).
a Top: M ) Re (13, 14, 15), Mn (17); P ) PPh2OEt (13, 17),
PPh2OMe (14), PPh3 (15). Bottom: Ar-Ar ) 4,4′-C6H4-C6H4 (b),
4,4′-C6H4-CH2-C6H4 (d).
complexes [Re(CO)5-nPn(HNdNAr-ArNtN)]2+ (n ) 2, 1)
(13-16), which were isolated in pure form and characterized
(Scheme 4). The 1H, 31P, and 15N NMR data of complexes 13-
15 indicate the presence of two stereoisomers of types A and B
(Scheme 4), which will be discussed below.
Investigations of the reactions between ReH(CO)5-nPn species
containing phosphines with ethoxy groups and bis(diazonium)
salts showed that the mononuclear diazene-diazonium com-
plexes were obtained exclusively with hydrides containing the
PPh2OEt ligand, whereas all other hydrides containing P(OEt)3
or PPh(OEt)2 always afforded the binuclear derivatives under
any conditions. These results may be related to the electronic
and steric properties28 of PPh2OEt as compared to other
phosphites, which induce a unique reactivity in ReH(CO)3-
(PPh2OEt)2 toward the bis(diazonium) cations. Furthermore, the
formation of the diazene-diazonium complexes [Re(CO)3P2-
(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 with P ) PPh2OMe (14)
and P ) PPh3 (15) confirmed that phosphine ligands with large
steric hindrance and rather weak π-acceptor properties28 allow
the mononuclear derivatives 13-16 to be prepared.
The properties shown by the rhenium hydrides ReH(CO)5-nPn
containing bulky PPh2OR or PPh3 ligands prompted us to
investigate the reactivity of the related manganese complexes
MnH(CO)3P2 toward bis(aryldiazonium) cations under appropri-
ate experimental conditions, in an attempt to prepare similar
diazene-diazonium derivatives. Binuclear [{Mn(CO)3P2}2(µ-
HNdNAr-ArNdNH)]2+ species have recently been synthe-
sized.3b Results showed that also the manganese diazene-
diazonium complex [Mn(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-
C6H4NtN)](BF4)2 (17b) can be prepared as a mixture of the
two isomers A and B (Scheme 4) and characterized.
“Diazene-Diazonium” Derivatives. In the course of syn-
thesizing the binuclear [{Re(CO)5-nPn}2(µ-HNdNAr-ArNd
NH)]2+ cations, we observed that, in some cases, the 1H NMR
spectra of the raw products showed a new NH signal of low
intensity besides that of the binuclear species. This observation
led us to hypothesize that the reactions between the hydrides
ReH(CO)5-nPn and bis(aryldiazonium) cations may also afford
mononuclear species of the type [Re(CO)5-nPn(HNdNAr-
ArNtN)]2+ as marginal products, obtained by reactions of
only one end of the +N2Ar-ArN2 ligands with the hydrides
+
(Scheme 3).
To test this hypothesis and to attempt to isolate these mono-
nuclear compounds containing a diazene-diazonium ligand in
pure form, we studied the reactions between ReH(CO)5-nPn and
+
+N2Ar-ArN2 species extensively and found that hydrides
containing PPh2OEt, PPh2OMe, and PPh3, under appropriate
conditions, reacted with equimolar amounts of bis(aryldiazo-
nium) cations to give the mononuclear diazene-diazonium
(28) (a) Tolman, C. A. Chem. ReV. 1977, 77, 313. (b) Rahman, M. M.;
Liu, H.-Y.; Eriks, K.; Prock, A.; Giering, W. P. Organometallics 1989,
8, 1.
(27) Haymore, B. L.; Ibers, J. A. J. Am. Chem. Soc. 1975, 97, 5369.

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3275
appearing as slightly broad doublets due to slight coupling with
the two magnetically equivalent phosphite ligands. The spectra
also show a singlet at -70 ppm (Table 5), attributed to the
diazonium 15N resonance of the 4,4′-15NtNC6H4-C6H4Nd15-
NH group. The presence of two NH resonances is probably due
to two isomers of the types shown in Scheme 4, with H and
aryl substituents mutually in trans and cis positions with respect
to the NdN moiety. For these two isomers, two proton NH
and two 15N NMR resonances are expected; the difference in
chemical shifts of the farther 15NtN group in the two isomers
is probably smaller than the line width, giving only one 15N
signal. Furthermore, the two NH resonances do not coalesce
into only one signal as temperature increases, indicating that
the two stereoisomers do not interconvert between +50 and -60
°C. Support for this hypothesis is given by the 31P{1H} NMR
spectra which, in the temperature range between +30 and -80
°C, show two singlets for each diazene-diazonium compound
with close chemical shift values (Table 4), as expected for the
two isomers.
Figure 2. 15N NMR spectrum of [Re(CO)3(PPh2OEt)2(4,4′-H15Nd
NC6H4-C6H4Nt15N)](BF4)2 (13b*) derivative, in CD2Cl2 at 25 °C.
The peak marked with the asterisk is due to an impurity.
The reactions of both the rhenium and manganese hydrides
MH(CO)5-nPn with bis(aryldiazonium) cations can therefore
proceed (with special phosphite ligands and under appropriate
conditions) through the insertion of only one NtN group,
affording the mononuclear diazene-diazonium complexes 13-
17. However, also in the case of PPh2OR or PPh3 complexes,
the reactions give the mononuclear complexes 13-17 as the
main products, since the binuclear [{M(CO)5-nPn}2(µ-HNd
NAr-ArNdNH)]2+ cations are always present in the reaction
products as secondary species (10-25%). In contrast, with
hydrides containing P(OEt)3 and PPh(OEt)2 ligands, the bi-
nuclear derivatives 6-11 were obtained exclusively.
These results may tentatively be explained on the basis of
rather low rates of +N2Ar-ArN2+ insertion into the M-H bonds
in the cases of MH(CO)5-nPn hydrides containing PPh2OR or
PPh3 ligands. As the second insertion involving a [M(CO)5-nPn-
(HNdNAr-ArNtN)]2+ cation is probably slower than the first,
the use of diluted reaction mixtures at low temperatures with
hydrides that react slowly with +N2Ar-ArN2+ allows diazene-
diazonium complexes to be prepared.
The mononuclear [M(CO)5-nPn(HNdNAr-ArNtN)](BF4)2
derivatives (13-17) are obtained as orange solid or gummy
products, stable both in air and in solutions of polar organic
solvents, where they behave as 1:2 electrolytes.25 Elemental
analyses and IR and NMR data (Tables 4 and 5) support the
proposed formulation. The spectroscopic data also indicate the
existence of stereoisomers A and B for each mononuclear
complex, with the geometries shown in Scheme 4.
Besides the ν(CO) bands, the IR spectra of the mononuclear
compounds 13-17 show one medium-intensity absorption band
between 2281 and 2265 cm-1, attributed to ν(NtΝ) of the HNd
NAr-ArNtN group. This band falls at a lower frequency than
that of the free species [N2Ar-ArN2](BF4)2 [ν(N2) at 2315
cm-1] and is shifted to a lower frequency (about 35 cm-1) for
the labeled [M(CO)3(PPh2OEt)2(4,4′-H15NdNC6H4-C6H4Nt
15N)](BF4)2 [M ) Re (13b*), Mn (17b*)] complexes, in
agreement with the proposed formulation.
In contrast with the results obtained for the diazene-
diazonium derivatives 13-17, all of the mono- and binuclear
aryldiazene cations [Re(ArNdNH)(CO)5-nPn]+ (1-5) and [{Re-
(CO)5-nPn}2(µ-HNdNAr-ArNdNH)]2+ (6-12), including those
containing the PPh2OEt ligand, show only one 1H and 15N NH
resonance, in agreement with the presence of only one stere-
oisomer involving the NdN group. The solid-state structure of
[Re(C6H5NdNH)(CO){P(OEt)3}4]BPh4 (1a) confirms the exist-
ence of only one isomer of type A. The formation of two
stereoisomers in the case of the [Re(CO)3P2(HNdNAr-ArNt
N)]2+ complexes (13-17) and only one for the other aryldiazene
derivatives (1-12) is rather surprising and may be explained
on the basis of the different reaction conditions (reagent ratios,
temperature, concentration) used in the two syntheses, which
may also cause two different mechanisms to operate in the
reactions. Preparing the binuclear [{Re(CO)3(PPh2OEt)2}2(µ-
4,4′-HNdNC6H4-C6H4NdNH)]2+ complex (11b) under dilute
conditions at 0 °C afforded a mixture of [Re(CO)3(PPh2OEt)2-
(4,4′-HNdNC6H4-C6H4NtN)]2+ (13b) and the binuclear
complex 11b, both showing two proton NH resonances probably
due to two stereoisomers for each compound. This fact partly
supports the hypothesis of the influence of experimental
conditions on reaction mechanism.
Heterobinuclear and Heterotrinuclear Aryldiazene Com-
plexes. The diazene-diazonium [M(CO)5-nPn(HNdNAr-
ArNtN)]2+ cations (13-17) contain an -NtN group which
may potentially react with a new metal hydride to afford
binuclear bis(aryldiazene) complexes. We therefore treated these
complexes with several metal hydrides whose reactivity with
aryldiazonium cations is well-known,3,17 obtaining the first
heterobinuclear complexes with bis(aryldiazene) bridging ligands,
as shown in Scheme 5.
The complexes were obtained as orange or reddish-brown
solids, stable in air and in solution of polar organic solvents,
where they behave as 1:2 electrolytes.25 Analytical and spec-
troscopic data (Table 4) confirm the proposed formulation and
also indicate the geometries shown in Scheme 5. The binuclear
complexes were in fact obtained as mixtures of the two
stereoisomers A and B, like those observed for the diazene-
diazonium precursors with the H and aryl substituents mutually
trans or cis to the NdN moiety. However, this isomerism only
involves the metal-bonded diazene of the [M(CO)3P2(HNd
NAr-ArNtN)]2+ precursors, since the other diazene is present
in only one isomer. The 1H NMR spectra of the heterobinuclear
complexes show two sets of NH proton resonances in the high-
The 1H NMR spectra of diazene-diazonium derivatives show
the NH diazene signal in the high-frequency region, appearing
as two slightly broad resonances at 14.44-12.95 ppm, both split
into doublets for the labeled [M(CO)3(PPh2OEt)2(4,4′-H15Nd
NC6H4-C6H4Nt15N)]2+ [M ) Re (13b*), Mn (17b*)] cations
1
with JNH ) 66 Hz. The proton-coupled (Figure 2) and
decoupled 15N NMR spectra of 13b* parallel the proton
spectrum, showing two 15NH resonances in the coupling spectra,

3276 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
Scheme 5a
Scheme 6a
a M ) Ru, Os; P ) PPh2OEt; P′ ) P(OEt)3.
reaction with a diazonium group, and we therefore reacted these
complexes with diazene-diazonium [M(CO)3P2(HNdNAr-
ArNtN)]2+ derivatives in an attempt to obtain heterotrinuclear
complexes. Although the reactions were rather slow, they did
yield, after workup, [Re(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-
C6H4NdNH)M2{P(OEt)3}4(µ-4,4′-HNdNC6H4-C6H4NdNH)-
Mn(CO)3(PPh2OEt)2](BPh4)4 (M2 ) Ru, Os) (Re13RuMn17,
Re13OsMn17) derivatives, which were isolated as solids and
characterized (Scheme 6).
The IR spectra show three ν(CO) bands (two strong and one
weak) which are quite broad due to the overlap of Re(CO)3
and Mn(CO)3 fragments. In the proton NMR spectra, apart from
the signals of the phosphites and BPh4, three groups of NH
resonances appear, attributed to the diazene bonded to the three
metals. Two of these groups of resonances, attributed to ReNd
NH and MnNdNH proton signals, appear as a set of two signals,
again indicating the presence of several isomers. The 31P{1H}
NMR data support the formulation of the complexes as tri-
nuclear species, showing three groups of signals at chemical
shift values near those expected for the Re(CO)3P2, RuP4 (or
OsP4), and Mn(CO)3P2 fragments, in agreement with the
proposed formulation.
Heterobinuclear Bis(aryldiazenido) Complexes. The known
properties of some aryldiazene complexes3,17 of transition
metals, which may be deprotonated with base to give aryldia-
zenido compounds, prompted us to attempt to synthesize a
heterobinuclear complex with a bis(aryldiazenido) bridging
ligand. The strategy used for this synthesis should therefore have
involved the initial preparation of a binuclear bis(aryldiazene)
species containing two metal fragments, each able to convert
the diazene ligand into the related diazenido ligand. However,
the properties shown by the rhenium aryldiazene complexes
1-12, which are unreactive toward base and do not give
aryldiazenido complexes, exclude the use of an Re aryldiazene
as one end of the binuclear complexes. Instead, only aryldiazene
species containing a rather labile ligand are reported3a,b,17b,d,e
to afford, by deprotonation, aryldiazenido complexes, according
to Scheme 7, which involves rearrangement of the ArN2 group
a Top: M1 ) Mn, Re; M2 ) Fe, Ru, Os; P ) PPh2OEt, PPh2OMe;
P′ ) P(OEt)3, PPh(OEt)2 (Os1). Bottom: M1 ) Mn, Re; M2 ) Re,
Mn; P ) PPh2OEt, PPh3; P′ ) P(OEt)3, PPh(OEt)2.
frequency region, one appearing as a broad signal and the other
as two slightly broad singlets. The latter are very similar to those
of the [M1(CO)3P2(HNdNAr-ArNtN)]2+ precursors (13-17)
and fall at similar chemical shift values, indicating the presence
of two isomers with H and aryl substituents mutually in cis
and trans positions with respect to the -NHdN(R) moiety. The
heterobinuclear nature of our complexes is also confirmed by
the 31P spectra, which show two groups of signals of phosphites
bonded to two different metals. In particular, the spectra of
ReRu, MnRu, ReOs, ReFe, and MnOs show complicated
AB2C multiplets due to the cis-M2HP4 (M2 ) Ru, Os) fragment
and a doublet due to stereoisomers A and B of the M1(CO)3P2
(M1 ) Re, Mn) center of the binuclear complexes. The proton
spectra of these complexes also have multiplets, at low
frequency, attributed to the hydride resonance of the M2HP4
fragment, in agreement with the proposed formulation.
+
and dissociation of one ligand to give a singly bent ArN2
species with a 2 e reduction of the central metal.
We therefore prepared the new heterobinuclear complex
[Mn(CO)3(PPh2OEt)2(µ-4,4′-HNdNC6H4-C6H4NdNH)Fe(4-
CH3C6H4CN){P(OEt)3}4](BPh4)3 (Mn17Fe1-b) by reacting [Mn-
(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4NtN)](BF4)2 with the
hydride17e [FeH(4-CH3C6H4CN){P(OEt)3}4]BPh4 and studied
the deprotonation reaction with an excess of NEt3. The reaction
proceeds at room temperature in CH2Cl2 with a rapid color
Complexes [M1(CO)3P2(µ-HNdNAr-ArNdNH)M2HP′4]2+
still contain a metal-hydride group accessible for further

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3277
Scheme 7
Scheme 9a
Scheme 8a
a P ) PPh2OEt; P′ ) P(OPh)3.
toward SP geometry may result in an ABC2-type spectrum, as
previously proposed for the related mononuclear17b [Fe(ArN2)-
P4]+ and binuclear3a [{FeP4}2(µ-N2Ar-ArN2)]2+ cations. This
distortion may have occurred in our case too, although restricted
rotation at low temperature of the Ar-ArNN group placed in
the equatorial plane of a regular TBP (Scheme 8) may also result
in an ABC2-type 31P spectrum.
The easy deprotonation of the aryldiazene complexes of
manganese [Mn(CO)3P2(HNdNAr)]+, on one hand, and the
unreactivity of the rhenium complexes [Re(CO)3P2(HNd
NAr)]+, on the other, suggested treating a binuclear [Re(CO)3P2-
(µ-HNdNAr-ArNdNH)Mn(CO)3P2](BPh4)2 complex with base
to prepare a binuclear complex with a diazene-diazenido
bridging ligand of the type in [Re(CO)3P2(µ-HNdNAr-ArNt
N)Mn(CO)2P2]BPh4. However, although the reaction with NEt3
proceeded easily at room temperature, no stable complex could
be obtained.
A different strategy was therefore employed in order to
prepare heterobinuclear complexes with an aryldiazene-aryl-
diazenido bridging ligand, involving the reaction of the diazene-
diazonium [Re(CO)3(PPh2OEt)2(4,4′-HNdNC6H4-C6H4Nt
N)]2+ cation with the dihydride FeH2(CO)2[P(OPh3)3]2 (Scheme
9), whose reactions with aryldiazonium cations are reported3c
to give aryldiazenido [Fe(ArN2)(CO)2{P(OPh3)3}2]+ derivatives.
The reaction proceeded slowly, affording the [Re(CO)3(PPh2-
OEt)2(µ-4,4′-HNdNC6H4-C6H4NtN)Fe(CO)2[P(OPh3)3]2]-
(BPh4)2 (Re13Fe2) complex (Scheme 9), which was isolated in
moderate yield and characterized.
Diagnostic for the presence of the diazene-diazenido bridging
ligand µ-HNdNAr-ArNtN are both IR and 1H NMR spectra
which show, respectively, a medium-intensity ν(N2) band at
1752 cm-1 and a slightly broad NH signal at 14.37 ppm.
Furthermore, the ν(CO) region of the IR spectrum contains five
bands which may be attributed, by spectral comparison with
the related mononuclear complexes, to the CO ligands of the
two ends of the complex. In particular, the two bands at 2054
and 2000 cm-1 are assigned to the two carbonyl ligands cis to
the Fe(CO)2 moiety, whereas the three at 2073(w), 1978(s), and
1944(s) cm-1 are attributed to the Re(CO)3 fragment with the
carbonyls in a mer arrangement. In the temperature range
between +30 and -80 °C, the 31P{1H} NMR spectra show the
signals of the phosphorus nuclei of the two end groups as
singlets, in agreement with the presence of two magnetically
equivalent phosphite ligands for both metals. On these bases, a
geometry of the type reported in Scheme 9 can be proposed for
this binuclear Re13Fe2 complex with a diazene-diazenido
bridging ligand.
a P ) PPh2OEt; P′ ) P(OEt)3; R ) 4-CH3C6H4.
change of the solution and the separation of (NHEt3)BPh4 as a
white solid, according to Scheme 8.
After workup, the heterobinuclear MnFe-b complex with a
bis(aryldiazenido) bridging ligand was isolated as a stable
reddish-orange solid and characterized in the usual way. The
compound is a diamagnetic solid and behaves as a 1:1 electrolyte
in solution.25 IR spectrum shows two strong bands in the ν-
(CO) region due to the two carbonyl ligands cis to the M(CO)2P2
end of the complex. The spectrum also shows one medium-
intensity band at 1653 cm-1 and two others at 1617 and 1560
cm-1. These bands shift to lower frequencies (1604 and 1580,
1541 cm-1, respectively) in the spectrum of the labeled [Mn-
(CO)2P2(µ-4,4′-15NtNAr-ArNt15N)FeP′4]BPh4 (MnFe-b*)
derivative and are attributed to ν(N2) of the FeN2Ar- (1654
cm-1) and MnN2Ar- (1617, 1560 cm-1) groups, respectively.
Attributions are based on comparison with the IR spectra of
the mononuclear Mn(CO)2P2(ArN2) and [FeP′4(ArN2)]+ deriva-
tives, previously reported by us,3b,17b which contain a singly
bent aryldiazenido ArN2+ ligand bonded to the formal Mn(-I)
or Fe(0) central metal. This probably also applies to the binuclear
MnFe-b derivative and is confirmed29,30 by the 15N NMR data
(Table 5).
The 31P{1H} NMR spectrum of the complex agrees with the
proposed formulation, showing two groups of signals attributed
to the phosphorus nuclei of the MnP2 and FeP′4 fragments. The
spectrum is also temperature dependent, and whereas the singlet
due to MnP2 at 174 ppm remains unchanged between +30 and
-90 °C, the rather broad resonance observed at room temper-
ature for the FeP′4 phosphorus nuclei resolves into an ABC2
multiplet at -30 °C. This type of spectrum seems to exclude a
regular TBP geometry of the type shown in Scheme 8, for which
an A2B2 spectrum would be expected. However, a TBP distorted
Electrochemical Reductions of Aryldiazene Complexes.
Voltammograms for the electrochemical reductions of the
mononuclear compounds 5a and [Mn(C6H5NdNH)(CO)3(PPh2-
OEt)2]BF4 (Mn1) in 0.1 M TBAH/DCE, recorded at 0.05 V
(29) Haymore, B. L.; Hughes, M.; Mason, J.; Richards, R. L. J. Chem.
Soc., Dalton Trans. 1988, 2935.
(30) Dilworth, J. R.; Kan, C. T.; Richards, R. L.; Mason, J.; Stenhouse, I.
J. Organomet. Chem. 1980, 201, C24.

3278 Inorganic Chemistry, Vol. 39, No. 15, 2000
Albertin et al.
s-1, are characterized by one irreversible reduction peak located
at -0.81 V for 5a and -0.92 V for Mn1. Increasing the scan
rate (V) to >1 V s-1 causes the progressive appearance of a
return peak with a concomitant increase in the Ip /Ip ratio (where
b
f
Ip and Ip are the currents of the peaks recorded in the backward
b
f
and forward scans, respectively), which approaches unity at a
scan rate of 30 V s-1
.
Ip V-1/2 values decrease slightly (by about 15%) when the
f
scan rate is increased from 1 to 30 V s-1. The peak potential
recorded in the forward scan (Ep ) shifts negatively with scan
f
rate, with a shift of about 80 mV when the scan rate is increased
from 0.1 to 1 V s-1
.
These findings indicate that the reduction follows an EC
mechanism, which involves a quasi-reversible electron-transfer
step followed by a chemical reaction. The quasi-reversibility
of the charge transfer is supported by the evidence that, when
V e 1 V s-1, the shift in peak potentials with scan rate is higher
than the 30 mV/decade value expected for an EC process with
reversible electron transfer. The value of almost unity for the
Ip /Ip ratio at 30 V s-1 indicates that, at this scan rate, almost
Figure 3. Experimental (full line) and simulated (dotted line) cyclic
voltammograms obtained for 2 × 10-3 M [Re(CO)3(PPh2OEt)2(µ-4,4′-
HNdNC6H4-C6H4NdNH)RuH{P(OEt)3}4](BPh4)2 (Re13Ru-b) at 0.05
V s-1. Supporting electrolyte: 0.1 M tetrabutylammonium hexafluoro-
phosphate/dichloroethane. Working electrode: glassy carbon (area 0.2
cm2). Potentials are referred to an aqueous Ag/AgCl reference electrode.
b
f
pure diffusion-controlled conditions hold. Comparison of peak
currents recorded at this scan rate with reduction peak currents
of mononuclear ruthenium complexes with one aryldiazene
ligand, which have been shown to undergo one-electron
reduction,3a indicates that the process is a one-electron reduction.
Half-wave potentials (E1/2), calculated as (Ep + Ep )/2 (where
The chemical reactions coupled with the electron transfer
could be proton-transfer reactions, isomeric equilibria, or (for
reactions 10 and 14) simple decomposition reactions. In any
case, they are well fitted in the simulations as simple first-order
processes.
The main point is that, for both the Re and Mn binuclear
compounds, the two electron-transfer processes take place at
different potential values: delocalization of the electron between
the two metal centers makes the first reduction process easier
than in the case of the mononuclear compounds. Moreover, in
the homobinuclear complex, the addition of the first electron
makes the second reduction process more energy demanding.
This situation is comparable to that observed previously for
ruthenium-diazene binuclear complexes,3a confirming that the
ability to provide electronic communication between the two
metal centers in the binuclear compounds is a property typical
of the diazene ligand
The importance of delocalization of the electron between the
two redox centers via the diazene bridging ligand is also
confirmed by the electrochemical behavior of heterobinuclear
compounds containing rhenium-ruthenium or manganese-
ruthenium redox centers. The full-line voltammogram of Figure
3 shows the pattern for the Re13Ru-b heterobinuclear complex.
The dotted-line voltammogram refers to data obtained by digital
simulation (see Table 2 for fitting parameters). A similar pattern
is observed for the Mn17Ru-b binuclear complex (at 0.05 V
s-1 the potentials of the two peaks are -0.81 and -1.29 V).
The first reduction process clearly involves the reduction of
either rhenium or manganese, while the second reduction peak
involves the ruthenium center.3a At variance with results relevant
to previously studied homobinuclear ruthenium complexes,3a at
all the scan rates employed in this work, the Ru reduction peak
is irreversible (a broad reoxidation peak starts to appear at 30
V s-1). This indicates that, in the heterobinuclear compounds,
electron transfer to the Ru center is followed by a chemical
reaction. At variance with Ru homobinuclear compounds,3a the
presence of a different metal center (Re or Mn) makes the
reduction products more unstable, thus decreasing their lifetimes
and hindering the possibility of observing their reoxidations on
a voltammetric time scale.
f
b
Ep is the potential of the peak recorded in the backward scan)
b
from the voltammograms at 30 Vs-1, are -0.80 V for 5a and
-0.88 V for Mn1. Satisfactory agreement between experimental
and simulated data is achieved using the (1)-(2) mechanism
and the fitting parameters listed in Table 2.
These findings indicate that, for mononuclear compounds,
the reduction mechanism is the following:
[M(I)]+ + e f [M(0)]0
[M(0)]0 h P1
(9)
(10)
where M ) Re or Mn and P1 is an unknown product.
Voltammetric patterns for the reduction of the binuclear
compounds 11b and [{Mn(CO)3(PPh2OEt)2}2(µ-4,4′-HNd
NC6H4-C6H4NdNH)](BPh4)2 (Mn2), recorded at 0.05 e V e
10 V s-1, are characterized by two irreversible reduction peaks;
associated return peaks can only be detected at 30 V s-1. At
0.05 V s-1, Ep values for the two peaks are -0.70 and -0.77
f
V for 11b and -0.84 and -1.00 V for Mn2. The change in
voltammetric parameters with scan rate (Ep values, appearance
f
of return peaks, etc.) follows the same trend as that observed
for the mononuclear compounds; a satisfactory fit between
experimental and simulated data is achieved via mechanism
(1)-(4), using the fitting parameters of Table 2.
These findings indicate that the following reduction mech-
anism is operative for the binuclear compounds:
[M(I)-M(I)]2+ + e f {[M(0)-M(I)]+}*
{[M(0)-M(I)]+ }* h {[M(0)-M(I)]+}**
{[M(0)-M(I)]+ }** + e f [M(0)-M(0)]0
[M(0)-M(0)]0 h P10
(11)
(12)
(13)
(14)
where M ) Re or Mn, {[M(0)-M(I)]+}* and {[M(0)-M(I)]+}-
** are two forms of the mixed-valence complex in equilibrium
with each other, and P10 is an unknown product.

Aryldiazene Complexes of Rhenium
Inorganic Chemistry, Vol. 39, No. 15, 2000 3279
Electrochemical Oxidations of Aryldiazenido Complexes.
Results obtained from voltammetric studies of mono- and
binuclear complexes with bis(aryldiazene) bridging ligands
prompted us to extend investigations also to binuclear aryldia-
zenido complexes of manganese, with the aim of clarifying the
different electrochemical behaviors observed between bis-
(aryldiazene) and bis(aryldiazenido) complexes of iron3c and
whether this behavior is typical of iron complexes or if it also
involves other central metals.
complexes were neutral species, whereas the Fe complexes
studied in ref 3c were cationic. Moreover, electrochemical
oxidations of Mn compounds are less irreversible than those of
Fe compounds, as evidenced by both the presence of small return
peaks and the ks values used in the simulations which, for Mn
complexes, are roughly 1 order of magnitude higher than those
obtained previously for the Fe case.3c
It must be emphasized that oxidation of diazenido binuclear
complexes with both Fe(0) and Mn(-I) metal centers proceeds
in such a way that each metal center does not show any
interaction with the other metal center of the same molecule,
since both centers are oxidized at potential values which may
be compared with each other as well as with that of the
mononuclear compound. These results contrast with those
observed for binuclear bis(aryldiazene) complexes of Fe(II),3a
Ru(II),3a Mn(I),3b and Re(I) and may be attributed to the different
electronic properties of the aryldiazenido NtNAr-ArNtN
(singly bent coordination)3b,c as compared to the aryldiazene
HNdNAr-ArNdNH bridging ligand, which prevent electronic
communication between the two metal centers in bis(aryldia-
zenido) derivatives.
Voltammetric patterns for electrochemical oxidations of the
mononuclear Mn(C6H5N2)(CO)2(PPh2OEt)2 (Mn3) and binuclear
{Mn(CO)2(PPh2OEt)2}2(µ-4,4′-N2C6H4-C6H4N2) (Mn4) com-
pounds are characterized by an oxidation peak with which a
small reduction peak (shifted toward much less positive potential
values) is associated in the return scan. Values of the oxidation
peak potentials at 0.05 V s-1 are 0.680 and 0.570 V for the
mononuclear and binuclear compounds, respectively. Both of
these peak values shift toward more positive potential values
with increasing scan rate; for instance, at 0.500 V s-1 they are
0.940 V for Mn3 and 0.670 V for Mn4. Peak currents increase
linearly with the square root of the scan rate; Ip /Ip values remain
b
f
almost constant at 0.64-0.67, i.e. always much lower than unity,
independent of the scan rate. All these findings, together with
the satisfactory fitting with simulated voltammograms [see Table
3 and mechanisms (5)-(6) for simulation parameters], indicate
that the charge-transfer process is irreversible. Comparison of
the Mn3 and Mn4 oxidation peak currents indicates that the
process for Mn(C6H5N2)(CO)2(PPh2OEt)2 is a one-electron
oxidation, whereas that for the binuclear compound {Mn(CO)2-
(PPh2OEt)2}2(µ-4,4′-N2C6H4-C6H4N2) is a two-electron oxida-
tion. The shape of the voltammogram (Ep - Ep /2 values, where
Conclusions
The present studies show that aryldiazene complex cations
of rhenium of the types [Re(ArNdNH)(CO)5-nPn]+ and [{Re-
(CO)5-nPn}2(µ-HNdNAr-ArNdNH)]2+ may easily be pre-
pared by insertions of mono- and bis(aryldiazonium) cations
into the Re-H bonds of the hydride species ReH(CO)5-nPn.
The first “diazene-diazonium” derivatives [M(CO)5-nPn(HNd
NAr-ArNtN)]2+ (M ) Re, Mn) were prepared through the
insertions of only one -NtN group of the bis(aryldiazonium)
cations [NtNAr-ArNtN]2+ into the MH(CO)5-nPn hydrides
containing bulky phosphite ligands. These diazene-diazonium
derivatives are building blocks for heterobinuclear M1-M2 and
heterotrinuclear M1-M-M2 complexes with bis(aryldiazene)
bridging ligands. In fact, the reactions of [M1(CO)5-nPn(HNd
NAr-ArNtN)]2+ with M2H2P′4 or M2′H(CO)3P′′2 metal
hydrides allow several examples of this new class of bi- and
trinuclear complexes, of the type Re-Ru, Re-Os, Mn-Ru,
Re-Mn, Re-Ru-Mn, etc., to be prepared. Furthermore,
syntheses of the heterobinuclear complexes incorporating a bis-
(aryldiazenido) bridging ligand [Mn(CO)2P2(µ-N2Ar-ArN2)-
FeP′4]BPh4 were also achieved, together with syntheses of the
“diazene-diazenido” [Re(CO)3P2(µ-HNdNAr-ArNtN)Fe-
(CO)2P′2]2+ cationic species. Finally, the structural parameters
of an aryldiazene complex of rhenium were determined and
electrochemical studies were conducted for both mono- and
binuclear derivatives prepared in this work.
f
f
Ep /2 is the half-peak potential) and the fitting with mechanism
f
(5)-(6) indicate that, as already observed for similar aryldia-
zenido compounds of iron,3c oxidation of the binuclear complex
of manganese is composed of two separate one-electron
processes, in which the two Mn centers behave as localized
redox centers not interacting with each other. Under these
conditions, the peak parameters are the same as those for a one-
electron-transfer process, the only difference being an increase
in peak current.31,32 The scheme for oxidation of the binuclear
compound that matches experimental and simulated voltam-
mograms is
[Mn-Mn] f [Mn-Mn]+ + e
[Mn-Mn]+ f [Mn-Mn]2+ + e
(15)
(16)
In the case of the mononuclear compound Mn(C6H5N2)(CO)2-
(PPh2OEt)2, oxidation is limited to the one-electron irreversible
process
Acknowledgment. The financial support of MURST, Rome
(Programmi di Ricerca Scientifica di Rilevante Interesse Na-
zionale, Cofinanziamento 1998/99), is gratefully acknowledged.
We thank Daniela Baldan and Danilo Rudello for technical
assistance.
[Mn] f [Mn]+ + e
(17)
Comparison of aryldiazenido-Mn(-I) compound data with
those for the Fe(0) complexes studied previously3c reveals that
oxidations of Mn complexes occur at less positive potential
values. This may be explained by the fact that the starting Mn
Supporting Information Available: An X-ray crystallographic file,
in CIF format for 1a, complete lists of IR and NMR data for all
complexes (Table S1), infrared spectra of 13b and 13b* (Figure S1),
and cyclic voltammograms of 5a and 11b (Figure S2) and Mn3 and
Mn4 (Figure S3). This material is available free of charge via the
Internet at http://pubs.acs.org.
(31) Flanagan, J. B.; Margel, S.; Bard, A. J.; Anson, F. C. J. Am. Chem.
Soc. 1978, 100, 4248.
(32) Ammar, F.; Saveant, J. M. J. Electroanal. Chem. Interfacial Electro-
chem. 1973, 47, 115.
IC991393+