The first acetimino complexes of Rh(III). 4-Imino-2-methylpentan-2-amino- Rh(III) complexes through metal-assisted intramolecular aldol-type condensation of two acetimino ligands

Article abstract of DOI:10.1021/ic051521w

[Rh(Cp*)Cl(μ-Cl)]₂ (Cp* = pentamethylcyclopentadienyl) reacts (i) with [Au(NH=CMe₂)(PPh ₃)]ClO₄ (1:2) to give [Rh(Cp*)(μ-Cl)(NH=CMe ₂)]₂(ClO₄)₂ (1), which in turn reacts with PPh₃ (1:2) to give [Rh(Cp*)Cl(NH=CMe ₂)(PPh₃)]-ClO₄ (2), and (ii) with [Ag(NH=CMe₂)]ClO₄ (1:2 or 1:4) to give [Rh(Cp*)Cl(NH=CMe₂)₂]ClO₄ (3) or [Rh(Cp*)-(NH=CMe₂)₃](ClO₄) ₂·H₂O (4·H₂O), respectively. Complex 3 reacts (i) with XyNC (1:1, Xy = 2,6-dimethylphenyl) to give [Rh(Cp*)Cl(NH=CMe₂)(CNXy)]ClO₄ (5), (ii) with Tl(acac) (1:1, acacH = acetylacetone) or with [Au(acac)-(PPh₃)] (1:1) to give [Rh(Cp*)(acac)(NH=CMe₂)]ClO₄ (6), (iii) with [Ag(NH=CMe₂)₂]ClO₄ (1:1) to give 4, and (iv) with (PPN)Cl (1:1, PPN = Ph₃P=N=PPh₃) to give [Rh(Cp*)Cl(imam)]Cl (7·Cl), which contains the imam ligand (N,N-NH=C(Me)CH₂C(Me)₂NH₂ = 4-imino-2-methylpentan-2-amino) that results from the intramolecular aldol-type condensation of the two acetimino ligands. The homologous perchlorate salt (7·ClO₄) can be prepared from 7·Cl and AgClO ₄ (1:1), by treating 3 with a catalytic amount of Ph₂C=NH, in an atmosphere of CO, or by reacting 4 with (PPN)CI (1:1). The reactions of 7·ClO₄ with AgClO₄ and PTo₃ (1:1:1, To = C₆H₄Me-4) or XyNC (1:1:1) give [Rh(Cp*)(imam) (PTo₃)](ClO₄)₂·H2O (8) or [Rh(Cp*)(imam)(CNXy)](ClO₄)₂ (9), respectively. The crystal structures of 3 and 7-Cl have been determined.

Full text of DOI:10.1021/ic051521w

Inorg. Chem. 2006, 45, 181−188
The First Acetimino Complexes of Rh(III).
4-Imino-2-methylpentan-2-amino Rh(III) Complexes through
−
Metal-Assisted Intramolecular Aldol-Type Condensation of Two
Acetimino Ligands
Jose´ Vicente,* Mar´ıa-Teresa Chicote,* Rita Guerrero, Inmaculada Vicente-Herna´ndez, and
Miguel M. Alvarez-Falco´n
Grupo de Qu´ımica Organometa´lica, Departamento de Qu´ımica Inorga´nica, UniVersidad de
Murcia, Aptdo. 4021, Murcia, 30071 Spain
Received September 6, 2005
[Rh(Cp*)Cl(
[Rh(Cp*)( -Cl)(NH
ClO4 (2), and (ii) with [Ag(NH
(NH CMe2)3](ClO4)2 H2O (4 H2O), respectively. Complex 3 reacts (i) with XyNC (1:1, Xy
give [Rh(Cp*)Cl(NH CMe2)(CNXy)]ClO4 (5), (ii) with Tl(acac) (1:1, acacH acetylacetone) or with [Au(acac)-
(PPh3)] (1:1) to give [Rh(Cp*)(acac)(NH CMe2)]ClO4 (6), (iii) with [Ag(NH CMe2)2]ClO4 (1:1) to give 4, and (iv)
PPh3) to give [Rh(Cp*)Cl(imam)]Cl (7 Cl), which contains the imam ligand
4-imino-2-methylpentan-2-amino) that results from the intramolecular aldol-type
ClO4) can be prepared from 7 Cl
NH, in an atmosphere of CO, or by reacting 4
ClO4 with AgClO4 and PTo3 (1:1:1, To C6H4Me-4) or XyNC (1:1:1) give
H2O (8) or [Rh(Cp*)(imam)(CNXy)](ClO4)2 (9), respectively. The crystal structures of
Cl have been determined.
µ
-Cl)]2 (Cp*
CMe2)]2(ClO4)2 (1), which in turn reacts with PPh3 (1:2) to give [Rh(Cp*)Cl(NH
CMe2)2]ClO4 (1:2 or 1:4) to give [Rh(Cp*)Cl(NH CMe2)2]ClO4 (3) or [Rh(Cp*)-
2,6-dimethylphenyl) to
)
pentamethylcyclopentadienyl) reacts (i) with [Au(NH
d
CMe2)(PPh3)]ClO4 (1:2) to give
µ
d
d
CMe2)(PPh3)]-
d
d
d
‚
‚
)
d
)
d
d
with (PPN)Cl (1:1, PPN
)
Ph3P
dNd
‚
(N,N-NH C(Me)CH2C(Me)2NH2
d
)
condensation of the two acetimino ligands. The homologous perchlorate salt (7
and AgClO4 (1:1), by treating 3 with a catalytic amount of Ph2C
with (PPN)Cl (1:1). The reactions of 7
[Rh(Cp*)(imam)(PTo3)](ClO4)2
3 and 7
‚
‚
d
‚
)
‚
‚
Introduction
could transmetalate the acetimine ligand(s) to different metal
complexes, thus providing a general method for preparing
acetimino complexes. In fact, using [Ag(NHdCMe2)2]ClO4,
Acetimine, one of the condensation products of acetone
and ammonia,1 is an unstable compound that decomposes
after short periods of storage to give acetonine (2,2,4,4,6-
pentamethyl-2,3,4,5-tetrahydropyrimidine).2 The difficulties
associated with the preparation and handling of acetimine3
may account for the scarcity of complexes with this ligand.
In fact, acetimine itself has never been used in the various
syntheses of the metal-acetimino complexes reported so
(4) Sellmann, D.; Thallmair, E. J. Organomet. Chem. 1979, 164, 337.
Harman, W. D.; Taube, H. Inorg. Chem. 1988, 27, 3261. Rappert, T.;
Yamamoto, A. Chem. Lett. 1994, 2211. Fischer, E. O.; Knauss, L.
Chem. Ber. 1970, 103, 1262. Czarkie, D.; Shvo, Y. J. Organomet.
Chem. 1970, 280, 123. Wong, K.-Y.; Che, C.-M.; Li, C.-K.; Chiu,
C.-K.; Zhou, Z.-Y.; Mak, T. C. W. Chem. Commun. 1992, 754.
Adcock, P. A.; Keene, F. R.; Smythe, R. S.; Snow, M. R. Inorg. Chem.
1984, 23, 2336. Yeh, W. Y.; Ting, C. S.; Peng, S. M.; Lee, G. H.
Organometallics 1995, 14, 1417. Castarlenas, R.; Esteruelas, M. A.;
On˜ate, E. Organometallics 2000, 19, 5454. Klingebiel, W.; Nolte-
meyer, M.; Schmidt, H.-G.; Schmidt-Ba¨se, D. Chem. Ber./Recl. 1997,
130, 753. Aresta, M.; Quaranta, E.; Dibenedetto, A.; Giannoccaro,
P.; Tommasi, I.; Lanfranchi, M.; Tiripicchio, A. Organometallics 1997,
16, 834. King, R. B.; Douglas, W. M. Inorg. Chem. 1974, 13, 1339.
Fornie´s, J.; Casas, J. M.; Mart´ın, A.; Rueda, A. J. Organometallics
2002, 21, 4560.
6
far.4-8 The synthesis by us of [Au(NHdCMe2)(PPh3)]ClO4
and [Ag(NHdCMe2)2]ClO4 prompted us to check if they
8
* To whom correspondence should be addressed. E-mail: jvs1@um.es
(J.V.), mch@um.es (M.-T.C.).
(1) Bradbury, R. B.; Hancox, N. C.; Hatt, H. H. J. Chem. Soc. 1947, 1394.
Murayama, K.; Morimura, S.; Amakasu, O.; Toda, T.; Yamao, E.
Nippon Kagaku Zasshi 1969, 90, 296 (Chem. Abstr. 1969, 70, 324).
(2) Findeisen, K.; Heitzer, H.; Dehnicke, K. Synthesis 1981, 702.
(3) Verardo, G.; Giumanini, A. G.; Strazzolini, P.; Poiana, M. Synth.
Commun. 1988, 18, 1501. Xu, T.; Zhang, J.; Haw, J. F. J. Am. Chem.
Soc. 1995, 117, 3171.
(5) Vicente, J.; Chicote, M. T.; Guerrero, R.; Vicente-Herna´ndez, I.;
Alvarez-Falco´n, M. M.; Jones, P. G.; Bautista, D. Organometallics
2005, 24, 4506.
(6) Vicente, J.; Chicote, M. T.; Guerrero, R.; Saura-Llamas, I. M.; Jones,
P. G.; Ram´ırez de Arellano, M. C. Chem.sEur. J. 2001, 7, 638.
10.1021/ic051521w CCC: $33.50
Published on Web 11/17/2005
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 1, 2006 181

Vicente et al.
CaH2, KMnO4, and Na/benzophenone, respectively. THF was
distilled under nitrogen from Na/benzophenone. Other solvents (n-
pentane (Baker) and n-hexane (Scharlau)) and reagents (AgClO4
(Aldrich), PPh3, PTo3, XyNC (Fluka), and (PPN)Cl (Lancaster))
were obtained from commercial sources and used as received. The
complexes [Rh(Cp*)Cl(µ-Cl)]2,15 [Au(NHdCMe2)(PPh3)]ClO4,6
[Ag(NHdCMe2)2]ClO4,8 and Tl(acac)16 were prepared according
to literature methods.
we have recently synthesized the first family of acetimino-
Rh(I) complexes.8
On the other hand, complexes with the ligand 4-imino-
2-methylpentan-2-amine (imam) are very scarce, and only
-
-
nine of them (including the Br-, NO3 , and ClO4 salts of
the [Ni(imam)2]2+ cation) have been fully characterized by
their X-ray crystal structures.9 They were obtained by
reacting some ammino complexes of Co(III)10 or Ni(II) with
Warning! Perchlorate salts of organic cations may be explosive.
Preparations on a scale larger than that reported here should be
avoided.
12,13
acetone,11 by treating Cu(NO3)2
or some Pd(II) com-
plexes7 with ammonia in acetone, or by reacting some Ru-
(III) complexes14 with ammonium thiobenzoate and acetone
or with ammonia and mesityl oxide. It was suggested that
the imam ligand forms by the condensation of two NH3
ligands and two Me2CO molecules or one of mesityl oxide
in a template-type reaction.10,12,14 Surprisingly, the formation
of the Pd(imam) complexes was explained7 on the assump-
tion that the imam ligand forms in equilibrium with other
species in ammonia/acetone mixtures. However, no experi-
mental or bibliographic evidence is provided in support of
the existence of this ligand in such mixtures.
Synthesis of [Rh(Cp*)(µ-Cl)(NHdCMe2)]2(ClO4)2 (1). To a
suspension of [Rh(Cp*)Cl(µ-Cl)]2 (226 mg, 0.366 mmol) in acetone
(15 mL) was added [Au(NHdCMe2)(PPh3)]ClO4 (450 mg, 0.731
mmol). After 2 h of being stirred, the orange suspension was
filtered, and the solid was washed with CH2Cl2 (3 × 5 mL) and
air-dried to give 1 as an orange powder. Yield: 232 mg, 74%.
1
Mp: 218 °C. H NMR (200 MHz, DMSO-d6): δ 1.64 (s, 15 H,
Me, Cp*), 2.30 (s, 3 H, Me), 2.37 (s, 3 H, Me), 10.07 (br, 1 H,
NH). 13C NMR (50 MHz, DMSO-d6): δ 8.76 (Me, Cp*), 27.14
3
1
(Me), 28.87 (d, Me, JCRh ) 2.2 Hz), 100.39 (d, C, Cp*, JCRh
)
7.3 Hz), 191.58 (CdN). IR (cm-1): ν(NH) 3242, ν(CdN) 1662,
1644. Anal. Calcd for C26H44Cl4N2O8Rh2: C, 36.30; H, 5.16; N,
3.26. Found: C, 36.32; H, 5.14; N, 3.27.
We have preliminarily reported the synthesis and some
structural features of [Rh(Cp*)Cl(NHdCMe2)2]ClO4 (3) and
of the product from the aldol-type condensation of the two
acetimino ligands in 3, namely [Rh(Cp*)Cl(imam)]Cl (7‚
Cl) (imam ) 4-imino-2-methylpentan-2-amino).5 In this
paper, we report (i) new types of Rh(III) complexes with
one ([Rh(Cp*)Cl(NHdCMe2)(L)]ClO4 (L ) PPh3, XyNC)
and [Rh(Cp*)(acac)(NHdCMe2)]ClO4), two ([Rh(Cp*)Cl-
(NHdCMe2)2]ClO4), or three ([Rh(Cp*)(NHdCMe2)3](ClO4)2)
acetimino ligands, (ii) a new example of aldol-type conden-
sation of two acetimino ligands from [Rh(Cp*)(NHdCMe2)3]-
(ClO4)2, (iii) a new type of imam complexes ([Rh(Cp*)-
(imam)(L)](ClO4)2 (L ) PPh3, XyNC)), and (iv) full details
of the crystal structures of 3 and 7‚Cl.
Synthesis of [Rh(Cp*)Cl(NHdCMe2)(PPh3)]ClO4 (2). To a
suspension of 1 (146.2 mg, 0.17 mmol) in acetone (20 mL) was
added PPh3 (92 mg, 0.35 mmol). After being stirred for 1 h, the
resulting solution was filtered through a short pad of Celite, and
the filtrate was concentrated under vacuum (to ca. 2 mL). Upon
addition of Et2O (25 mL), 2 precipitated as a yellow powder, which
was filtered and air-dried. Yield: 232 mg, 99%. Mp: 179 °C dec.
4
1H NMR (400 MHz, CDCl3): δ 1.50 (d, 15 H, Me, Cp*, JHP
)
4
3.53 Hz), 1.91 (d, 3 H, Me, JHH ) 0.64 Hz), 2.22 (s, 3 H, Me),
7.55 (m, 15 H, Ph), 8.69 (br, 1 H, NH). 13C{1H} NMR (100 MHz,
CDCl3): δ 9.11 (Me, Cp*), 26.88 (Me), 30.17 (Me), 100.65 (dd,
C, Cp*, 1JCRh ) 6.65 Hz, 2JCP ) 2.42 Hz), 128.16 (ipso-C), 128.69
(d, o-C, 2JCP ) 10.3 Hz), 131.36 (m-C), 134.6 (d, p-C, 4JCP ) 8.9
Hz), 191.27 (CdN). 31P{1H} NMR (121 MHz, CDCl3): δ 35.70
(d, JPRh ) 135.7 Hz). IR (cm-1): ν(NH) 3273, ν(CdN) 1644.
1
Experimental Section
ΛM: 158 Ω-1 cm2 mol-1. Anal. Calcd for C31H37Cl2NO4PRh: C,
53.77; H, 5.39; N, 2.02. Found: C, 53.92; H, 5.42; N, 1.98.
Synthesis of [Rh(Cp*)Cl(NHdCMe2)2]ClO4 (3). To a suspen-
sion of [Rh(Cp*)Cl(µ-Cl)]2 (144 mg, 0.233 mmol) in acetone (30
mL) was added [Ag(NHdCMe2)2]ClO4 (150 mg, 0.467 mmol). The
reaction mixture was stirred for 30 min, and was filtered through
a short pad of Celite. The filtrate was concentrated under vacuum
(to ca. 1 mL), and Et2O (25 mL) was added to precipitate a solid
that was filtered, washed with Et2O (5 mL), and air-dried to give
3 as an orange powder. Yield: 194 mg, 85%. Mp: 180 °C dec. 1H
NMR (300 MHz, CDCl3): δ 1.65 (s, 15 H, Me, Cp*), 2.37 (s, 6
IR spectroscopy, elemental analyses, and melting point deter-
minations were carried out as described elsewhere.6 Molar con-
ductivities were measured on ca. 5 × 10-4 M acetone solutions
with a Crison Micro CM2200 conductimeter. The NMR spectra
were recorded on Bruker Avance 200, 300, or 400 MHz spectrom-
eters. Chemical shifts are referred to TMS (1H and 13C{1H}) and
H3PO4 (31P{1H}). Unless otherwise stated, all reactions were carried
out at room temperature without special precautions against
moisture. CH2Cl2, acetone, and Et2O were distilled before use from
(7) Ruiz, J.; Rodr´ıguez, V.; Cutillas, N.; Lo´pez, G. Organometallics 2002,
21, 4912.
(8) Vicente, J.; Chicote, M. T.; Guerrero, R.; Vicente-Herna´ndez, I.; Jones,
P. G. Inorg. Chem. 2003, 42, 7644.
(9) Cambridge Structural Database, version 5.25; Cambridge Crystal-
lographic Data Centre: Cambridge, U.K.; December 2004.
(10) Alzuet, G.; Ferrer, S.; Casanova, J.; Borra´s, J.; Castin˜eiras, A. Inorg.
Chim. Acta 1993, 205, 79. Fairlie, D. P.; Turner, M.; Byriel, K. A.;
McKeon, J. A.; Jackson, W. G. Inorg. Chim. Acta 1999, 290, 133.
(11) Hanic, F.; Machajdik, D. Chem. ZVesti 1969, 23, 3. Rose, N. J.; Elder,
M. S.; Busch, D. H. Inorg. Chem. 1967, 6, 1924. Domiano, P.; Musatti,
A.; Pelizzi, C. Cryst. Struct. Commun. 1975, 4, 185. Jehn, W. Z. Anorg.
Allg. Chem. 1967, 351, 260.
4
H, Me), 2.41 (d, 6 H, Me, JHH ) 1.2 Hz), 9.53 (br, 2 H, NH).
13C{1H} NMR (100 MHz, CDCl3): δ 9.08 (Me, Cp*), 26.77 (Me),
3
1
30.29 (d, Me, JCRh ) 1.2 Hz), 95.37 (d, C, Cp*, JCRh ) 8 Hz),
190.67 (CdN). IR (cm-1): ν(NH) 3250, ν(CdN) 1642. ΛM: 139
Ω-1 cm2 mol-1. Anal. Calcd for C16H29Cl2N2O4Rh: C, 39.44; H,
6.00; N, 5.75. Found: C, 39.16; H, 6.03; N, 5.62. Single crystals
of 3 grew by the liquid diffusion method using CH2Cl2 and Et2O.
Synthesis of [Rh(Cp*)(NHdCMe2)3](ClO4)2‚H2O (4‚H2O). To
a solution of 3 (100 mg, 0.21 mmol) in CH2Cl2 (20 mL) was added
[Ag(NHdCMe2)2]ClO4 (66 mg, 0.21 mmol). The resulting suspen-
(12) Curtis, N. F. Coord. Chem. ReV. 1968, 3, 3.
(13) Hanic, F.; Serator, M. Chem. ZVesti 1964, 18, 572.
(14) Gould, R. O.; Stephenson, T. A.; Thomson, M. A. J. Chem. Soc.,
Dalton Trans. 1978, 769.
(15) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 228.
(16) Vicente, J.; Chicote, M. T. Inorg. Synth. 1998, 32, 172.
182 Inorganic Chemistry, Vol. 45, No. 1, 2006

First Acetimino Complexes of Rh(III)
sion was stirred for 5 h, and was filtered through a short pad of
Celite. When the filtrate was concentrated under vacuum (to ca. 5
mL), a yellow solid precipitated that was filtered and dried under
nitrogen to give 4‚H2O as a yellow powder. Yield: 70 mg, 54%.
mg, 0.40 mmol). After 30 min of being stirred, the resulting
suspension was filtered through Celite. The yellow filtrate was
concentrated under vacuum (to ca. 1 mL), and Et2O (25 mL) was
added to precipitate a solid that was filtered and air-dried to give
7‚ClO4 as an orange powder. Yield: 183 mg, 95%. Mp: 215 °C
dec. 1H NMR (300 MHz, CDCl3): δ 1.12 (s, 3 H, Me), 1.54 (s, 3
H, Me), 1.76 (s, 15 H, Me, Cp*), 2.34, 2.56 (AB system, 2 H,
1
Mp: 228 °C dec. H NMR (300 MHz, DMSO-d6): δ 1.59 (s, 15
H, Me, Cp*), 1.78 (s, 9 H, Me), 2.30 (s, 9 H, Me), 3.31 (br, 2 H,
H2O), 10.06 (br, 3 H, NH). 13C{1H} NMR (100 MHz, DMSO-d6):
δ 8.37 (Me, Cp*), 25.63 (Me), 29.10 (Me), 97.11 (d, C, Cp*, 1JCRh
) 7.5 Hz), 190.51 (CdN). IR (cm-1): ν(OH) 3600, ν(NH) 3240,
ν(CdN) 1651, 1634. ΛM: 198 Ω-1 cm2 mol-1. Anal. Calcd for
C19H38Cl2N3O9Rh: C, 36.44; H, 6.12; N, 6.71. Found: C, 36.43;
H, 5.83; N, 6.74.
Synthesis of [Rh(Cp*)Cl(NHdCMe2)(CNXy)]ClO4 (5). To a
suspension of 3 (100 mg, 0.205 mmol) in dry THF under nitrogen
was added XyNC (27 mg, 0.206 mmol). After being stirred for 1
h, the resulting suspension was filtered, and the collected solid was
washed with Et2O (3 × 5 mL) and air-dried to give 5 as a yellow
powder. Yield: 72 mg, 62%. Mp: 103 °C dec. 1H NMR (300 MHz,
CDCl3): δ 1.87 (s, 15 H, Me, Cp*), 2.38 (s, 3 H, Me), 2.45 (d, 3
H, Me, 4JHH ) 1.2 Hz), 2.48 (s, 6 H, Me, Xy), 7.20 (m, 3 H, Xy),
9.49 (br, 1 H, NH). 13C{1H} NMR (75 MHz, CDCl3): δ 9.68 (Me,
Cp*), 18.76 (Me, Xy), 27.35 (Me), 30.16 (d, Me, 3JCRh ) 1.5 Hz),
101.55 (d, C, Cp*, 1JCRh ) 7.5 Hz), 128.2 (m-C), 130.2 (p-C), 135.9
(o-C), 190.8 (CdN) IR (cm-1): ν(NH) 3177, ν(C≡N) 2170,
ν(CdN) 1664, 1645. ΛM: 170 Ω-1 cm2 mol-1. Anal. Calcd for
C22H31Cl2N2O4Rh: C, 47.08; H, 5.57; N, 4.99. Found: C, 46.66;
H, 5.72; N, 5.01.
4
CH2, JAB ) 16.7 Hz), 2.41 (d, 3 H, Me, JHH ) 1.1 Hz), 3.31 (d,
2
2
1 H, NH2, JHH ) 11.2 Hz), 4.22 (d, 1 H, NH2, JHH ) 11.2 Hz),
9.58 (br, 1 H, NH). IR (cm-1): ν(NH) 3291, 3272, 3256, 3241,
ν(CdN) 1657, δ(NH2) 1585. ΛM: 160 Ω-1 cm2 mol-1. MS
(FAB+): (m/z, %): [M+] 386.91, 100, [M+ - Cl] 350.93, 52. Anal.
Calcd for C16H29Cl2N2O4Rh: C, 39.44; H, 6.00; N, 5.75. Found:
C, 39.43; H, 6.00; N, 5.61.
Synthesis of [Rh(Cp*)(imam)(PTo3)](ClO4)2‚H2O (8). To a
solution of 7‚ClO4 (47 mg, 0.10 mmol) in acetone (20 mL) were
successively added AgClO4 (20 mg, 0.10 mmol) and PTo3 (29 mg,
0.10 mmol) with an interval of 2 min. After 1 h of being stirred,
the resulting suspension was concentrated to dryness under vacuum.
The residue was stirred with CH2Cl2 (10 mL), and the suspension
was filtered through a short pad of Celite. The yellow filtrate was
concentrated under vacuum (to ca. 1 mL), and Et2O (30 mL) was
added to precipitate a solid that was filtered and air-dried to give
8 as a lemon yellow powder. Yield: 58 mg, 69%. Mp: 210 °C
dec. 1H NMR (300 MHz, CDCl3): δ -0.08 (d, 1 H, CH2, 2JHH
18 Hz), 1.08 (s, 3 H, Me), 1.25 (s, 3 H, Me), 1.60 (d, 15 H, Me,
Cp*, 4JHP ) 3 Hz), 1.77 (s, 2 H, H2O), 1.90 (d, 1 H, CH2, 2JHH
)
)
Synthesis of [Rh(Cp*)(acac)(NHdCMe2)]ClO4 (6). To a solu-
tion of 3 (83 mg, 0.17 mmol) in acetone (20 mL) was added Tl-
(acac) (52 mg, 0.17 mmol). After 1 h of being stirred, the resulting
suspension was filtered through a short pad of Celite. The yellow
filtrate was concentrated under vacuum (to ca. 1 mL), and Et2O
(25 mL) was added to precipitate a solid that was filtered and dried
under nitrogen to give 6 as a yellow powder. Yield: 74 mg, 88%.
18 Hz), 2.40 (s, 3 H, Me), 2.44 (s, 9 H, Me, To), 2.75 (d, 1 H,
NH2, 2JHH ) 9 Hz), 5.21 (d, 1 H, NH2, 2JHH ) 12 Hz), 7.32-7.46
(m, 12 H, To), 10.29 (br, 1 H, NH). 13C NMR (50 MHz, CDCl3):
δ 9.47 (d, Me, Cp*, 2JCP ) 1.1 Hz), 21.45 (d, Me, To, 5JCP ) 1.6
Hz), 25.2 (Me), 31.08 (Me), 31.71 (Me), 49.30 (CH2), 102.76 (dd,
C, Cp*, 1JCRh ) 5.9 Hz, 2JCP ) 1.6 Hz), 123.35 (d, ipso-C, 1JCP
)
)
1
2
3
Mp: 193 °C dec. H NMR (400 MHz, CDCl3): δ 1.61 (s, 15 H,
47.3 Hz), 130.65 (d, o-C, JCP ) 10.7 Hz), 134.1 (d, m-C, JCP
4
5.4 Hz), 143.6 (d, p-C, JCP ) 2.7 Hz), 189.70 (CdN). 31P NMR
Me, Cp*), 1.95 (s, 6 H, Me), 2.21 (s, 3 H, Me), 2.34 (d, 3 H, Me,
4JHH ) 0.65 Hz), 5.07 (s, 1 H, CH), 8.71 (br, 1 H, NH). 13C{1H}
NMR (100 MHz, CDCl3): δ 8.35 (Me, Cp*), 25.54 (Me), 28.08
1
(121 MHz, CDCl3): δ 34.1 (d, JPRh ) 134.1 Hz). IR (cm-1): ν-
(OH) 3604, ν(NH) 3289, 3241, ν(CdN) 1644, δ(NH2) 1597, 1583.
3
1
ΛM: 210 Ω-1 cm2 mol-1. MS (FAB+) (m/z, %): [M+ - ClO4-],
(Me), 29.69 (d, Me, JCRh ) 1.23 Hz), 93.66 (d, C, Cp*, JCRh
)
3
8.8 Hz), 98.55 (d, CH, JCRh ) 1.25 Hz), 187.31 (CdN), 188.57
(CdO). IR (cm-1): ν(NH) 3247, ν(CdN) 1663, ν(CdO) 1580.
ΛM: 165 Ω-1 cm2 mol-1. Anal. Calcd for C18H29ClNO6Rh: C,
43.78; H, 5.92; N, 2.84. Found: C, 43.89; H, 5.96; N, 3.10.
Synthesis of [Rh(Cp*)Cl(imam)]Cl [7‚Cl, imam ) NHdC-
(Me)CH2C(Me)2NH2]. To a solution of 3 (120 mg, 0.25 mmol) in
acetone (15 mL) was added (PPN)Cl (141 mg, 0.25 mmol). After
being stirred for 4 h, the resulting suspension was filtered, and the
collected solid was washed with Et2O (3 × 5 mL) and air-dried to
give 7‚Cl as an orange powder. Yield: 54 mg, 52%. Mp: 210 °C
dec. 1H NMR (400 MHz, CDCl3): δ 1.14 (s, 3 H, Me), 1.63 (s, 3
H, Me), 1.93 (s, 15 H, Me, Cp*), 2.19, 2.45 (AB system, 2 H,
-
-
754.84, 5, [M+ - ClO4 - PTo3] 450.96, 66, [M+ - 2ClO4
-
PTo3] 350.98, 100. Anal. Calcd for C37H52Cl2N2O9PRh: C, 50.87;
H, 6.00; N, 3.21. Found: C, 51.12; H, 5.96; N, 3.37.
Synthesis of [Rh(Cp*)(imam)(CNXy)](ClO4)2 (9). Solid Ag-
ClO4 (26 mg, 0.125 mmol), 3 (60 mg, 0.123 mmol), and XyNC
(16 mg, 0.122 mmol) were placed in a flask under nitrogen. Acetone
(20 mL) was added, and the resulting suspension was stirred for 2
h. The mixture was filtered through a short pad of Celite, and the
yellow filtrate was concentrated under vacuum (to ca. 1 mL). Upon
the addition of Et2O (25 mL), a solid precipitated that was filtered
and dried under nitrogen to give 9 as a lemon yellow powder.
Yield: 79 mg, 95%. Mp: 155 °C dec. 1H NMR (300 MHz, acetone-
d6): δ 1.36 (s, 3 H, Me), 1.41 (s, 3 H, Me), 2.05 (s, 15 H, Me,
Cp*), 2.49 (s, 6 H, Me, Xy), 2.56 (d, 3 H, Me, 4JHH ) 3 Hz), 2.71,
2.87 (AB system, 2 H, CH2, JAB ) 16.5 Hz), 4.14 (d, 1 H, NH2,
2
CH2, JAB ) 16.5 Hz), 2.53 (s, 3 H, Me), 2.95 (d, 1 H, NH2, JHH
) 11 Hz), 6.31 (d, 1 H, NH2, 2JHH ) 11 Hz), 11.39 (br, 1 H, NH).
13C{1H} NMR (100 MHz, CDCl3): δ 10.13 (Me, Cp*), 23.95 (Me),
1
31.25 (Me), 32.08 (Me), 48.41 (CH2), 96.50 (d, C, Cp*, JCRh
)
2
2JHH ) 12 Hz), 5.32 (d, 1 H, NH2, JHH ) 12 Hz), 7.33 (m, 3 H,
7.8 Hz), 185.13 (CdN). IR (cm-1): ν(NH) 3218, 3192, 3110,
ν(CdN) 1654, δ(NH2) 1600. MS (FAB+) (m/z, %): [M+] 386.94,
100, [M+ - Cl] 350.97, 26. Anal. Calcd for C16H29Cl2N2Rh: C,
45.41; H, 6.91; N, 6.62. Found: C, 45.23; H, 6.65; N, 6.33. Single
crystals of 7‚Cl were obtained by the liquid diffusion method using
CH2Cl2 and Et2O.
Xy), 10.55 (br, 1 H, NH). 13C NMR (100 MHz, acetone-d6): δ
9.50 (s, Me, Cp*), 18.97 (Me, Xy), 26.96 (Me), 28.25 (Me), 31.48
(Me), 48.74 (CNH2), 50.77 (CH2), 103.91 (d, C, Cp*, 1JCRh ) 6.6
Hz), 129.15 (m-C) 131.51 (p-C), 137.21 (o-C), 191.05 (CdN). IR
(cm-1): ν(NH) 3243, 3161, ν(C≡N) 2169, ν(CdN) 1659, δ(NH2)
1598. ΛM: 180 Ω-1 cm2 mol-1. MS (FAB+) (m/z, %): [M+
-
[Rh(Cp*)Cl(imam)]ClO4 (7‚ClO4). To a suspension of 7‚Cl
(167 mg, 0.39 mmol) in acetone (40 mL) was added AgClO4 (82
-
ClO4-] 581.99, 5, [M+ - ClO4 - XyNC] 450.93, 52, [M+ - 2
Inorganic Chemistry, Vol. 45, No. 1, 2006 183

Vicente et al.
Scheme 1
Table 1. Crystal Data for Compounds 3 and 7‚Cl
3
7‚Cl
formula
cryst size (mm3)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C16H29Cl2N2O4Rh
0.25 × 0.19 × 0.16
monoclinic
P21
8.5542(3)
15.9110(6)
15.4317(6)
90
102.1380(10)
90
2053.39(13)
4
C16H29Cl2N2Rh
0.11 × 0.11 × 0.10
monoclinic
C2/c
13.5331(6)
12.0370(4)
22.7027(8)
90
94.644(4)
90
3686.1(2)
8
Z
F
Mr
calcd (mg m-3
)
1.576
487.22
1.525
423.22
T (K)
100(2)
133(2)
F(000)
index ranges
1000
1744
-10 e h e 10
-20 e k e 20
-19 e l e 19
1.21
1.35-27.10
semiempirical
from equiv
23 574
-19 e h e 19
-17 e k e 17
-32 e l e 32
1.11
1.80-30.50
semiempirical
from equiv
42 399
µ (Mo KR; mm-1
θ range (deg)
abs corr
)
no. of reflns collected
no. of indep reflns
Rint
8876
0.0150
5620
0.0458
transm
0.8419/0.7682
8876/15/479
0.0198
0.0488
0.482 and -0.408
0.8883/0.7774
5620/0/210
0.0262
0.0607
0.765 and -0.366
data/restraints/params
R1 [I > 2σ(I)]
wR2 (all reflns)
largest difference peak
and hole (e Å-3
)
-
ClO4 - XyNC] 350.95, 100. Anal. Calcd for C25H38Cl2N3O8Rh:
C, 44.00; H, 5.61; N, 6.16. Found: C, 43.63; H, 5.63; N, 6.15.
X-ray Structure Determinations. The structures of 3 and 7‚
Cl were determined (Table 1). Data were registered on Bruker
SMART APEX at 100 K (3) and Bruker SMART 1000 at 133 K
CCD diffractometers, respectively, using Mo KR radiation (λ )
0.71073 Å). Absorption corrections were applied using the program
SADABS. Structures were refined anisotropically on F2 using
program system SHELXL.17 Hydrogen atoms were included as
follows: NH free, rigid methyls, others riding.
produced a solution from which [Rh(Cp*)Cl(NHdCMe2)-
(PPh3)]ClO4 (2) was obtained in almost quantitative yield.
However, the reactions of 1 with chloride (Me4NCl (1:4) or
PPNCl (1:2), both in acetone), expected to produce bridge
splitting with formation of [Rh(Cp*)Cl2(NHdCMe2)], instead
Results and Discussion
1
gave mixtures of compounds (by H NMR) that we could
not separate.
Synthesis of Acetimino Complexes of Rh(III). The imine
transfer reaction between [Au(NHdCMe2)(PPh3)]ClO4 and
[Rh(Cp*)Cl(µ-Cl)]2 (2:1, in acetone, Scheme 1) produced
the dinuclear complex [Rh(Cp*)(µ-Cl)(NHdCMe2)]2(ClO4)2
(1) in good yield, which could easily be separated from the
byproduct [AuCl(PPh3)] because of the insolubility of 1 in
acetone and CH2Cl2. The use of gold(I) complexes as
transmetallating agents6,18,19 is increasing. We have used this
method for the synthesis of other gold complexes.6,19 The
addition of 2 equiv of PPh3 to an acetone suspension of 1
The mononuclear bis(acetimino)-Rh(III) complex [Rh-
(Cp*)Cl(NHdCMe2)2]ClO4 (3) formed along with AgCl
from the reaction of [Ag(NHdCMe2)2]ClO4 with [Rh(Cp*)-
Cl(µ-Cl)]2 (2:1, in acetone or CH2Cl2), and could be isolated
in good yield.
The reaction of 3 with [Ag(NHdCMe2)2]ClO4 (1:1, in
CH2Cl2) produced the tris(acetimino) complex [Rh(Cp*)-
(NHdCMe2)3](ClO4)2‚H2O (4‚H2O), which could also be
obtained directly from [Rh(Cp*)Cl(µ-Cl)]2 and 4 equiv of
[Ag(NHdCMe2)2]ClO4. 4 is rather hygroscopic, and was
isolated as a monohydrate even though it was filtered and
dried under nitrogen. The yield was only moderate, but we
(17) Sheldrick, G. M. SHELXL; University of Go¨ttingen: Go¨ttingen,
Germany.
(18) Singh, A.; Sharp, P. R. J. Chem. Soc., Dalton Trans. 2005, 2080. Bruce,
M. I.; Humphrey, P. A.; Melino, G.; Skelton, B. W.; White, A. H.;
Zaitseva, N. N. Inorg. Chim. Acta 2005, 358, 1453. Contel, M.; Stol,
M.; Casado, M. A.; van Klink, G. P. M.; Ellis, D. D.; Spek, A. L.;
van Koten, G. Organometallics 2002, 21, 4556. Ferrer, M.; Rodr´ıguez,
L.; Rossell, O.; Lima, J. C.; Go´mez-Sal, P.; Mart´ın, A. Organometallics
2004, 23, 5096. Gregory, J.; Ingold, C. K. J. Chem. Soc. B 1969, 276.
Bennett, M. A.; Bhargava, S. K.; Griffiths, K. D.; Robertson, G. B.;
Wickramasinghe, W. A.; Willis, A. C. Angew. Chem., Int. Ed. 1987,
26, 258.
(19) Vicente, J.; Chicote, M. T.; Abrisqueta, M. D.; Jones, P. G.
Organometallics 1997, 16, 5628. Vicente, J.; Chicote, M. T.; Abris-
queta, M. D. J. Chem. Soc., Dalton Trans. 1995, 497. Vicente, J.;
Chicote, M. T.; Abrisqueta, M. D.; Alvarez-Falco´n, M. M. J.
Organomet. Chem. 2002, 663, 40. Vicente, J.; Chicote, M. T.; Jones,
P. G. Inorg. Chem. 1993, 32, 4960.
184 Inorganic Chemistry, Vol. 45, No. 1, 2006

First Acetimino Complexes of Rh(III)
Scheme 2
Scheme 3
equimolar amount of AsPh3 (acetone, 24 h) or a catalytic
amount of SMe2 (1:0.1, acetone, 24 h), or when it is heated
at 70 °C in solution (CH2Cl2 or acetone, in a Carius tube)
for 24 h. However, in all these cases, a small amount of
1
another product was detected by H NMR.
As we have mentioned in the Introduction, all the previous
data on imam metal complexes suggest that this ligand forms
from the condensation of acetone or mesityl oxide with
ammonia in a template reaction assisted by a base.12,20 The
formation of complexes 7‚Cl and 7‚ClO4 shows for the first
time that the imam ligand can form by an intramolecular
aldol-type self-condensation of two acetimino ligands,
promoted by gentle heating or by the addition of various
ligands. An intermolecular process involving the attack of a
free acetimine molecule (generated by a replacement or
dissociation process) to an acetimino ligand can be ruled out,
as the reactions of 3 with PPh3, XyNC, or [Ag(NHdCMe2)2]-
ClO4 (1:1) gave the corresponding mono- (2, 5) or tri-
acetimino (4) products (by NMR), respectively, whereas no
imam complex could be detected despite the presence of free
acetimine in such reaction mixtures.
could not improve it by adding Et2O to complete the
precipitation because, in this case, 4‚H2O precipitated along
with an unidentified impurity.
Complex 3 reacted with XyNC (1:1, THF, under nitrogen)
to give [Rh(Cp*)Cl(NHdCMe2)(CNXy)]ClO4 (5), which
could not be obtained directly from 1 and XyNC (1:2, THF),
although it was identified by 1NMR in the resulting mixture.
The reaction between equimolar amounts of 3 and [Au-
(acac)(PPh3)] in acetone, which we carried out in an attempt
to replace the NH hydrogen atom of one of the acetimino
ligands by the isolatable AuPPh3 group, instead gave the
complex [Rh(Cp*)(acac)(NHdCMe2)]ClO4 (6), which was
isolated in good yield. It could also be obtained by using
Tl(acac) instead of [Au(acac)(PPh3)]. Complex 6 is rather
hygroscopic, and was isolated under nitrogen.
On the assumption that the same mechanism applies to
all the reactions of 3 with L to give 7‚ClO4, the ability of
CO to promote the condensation process allows us to
conclude that the role of the added ligand is not that of the
base usually required as the catalyst in aldol condensations.
However, it is evident that the coordination of L can modify
both the electronic properties of the metal (changing the
coordination mode of Cp* from η5 to η3 (A in Scheme 3),
among other effects) and/or the geometry of the complex
(change in the coordination number or relative disposition
of the ligands, particularly the two acetimino ligands). The
latter seems to be the most important effect because (i)
condensation also occurs in the absence of added L upon
gentle heating of 3 and (ii) the nature of the ligands capable
of effecting condensation ranges from σ and π donor (Cl-,
SMe2) to π acceptor/weak σ donor (CO). Similarly, the
observed transformation of 4 into 7‚ClO4 upon addition of
PPNCl could take place by coordination of chloride, con-
densation of two acetimino ligands into the chelating imam,
and displacement of the most labile acetimino ligand.
Synthesis of 4-Imino-2-methylpentan-2-amino Com-
plexes of Rh(III). When we reacted 3 with PPNCl (1:1,
acetone, 4 h) in an attempt to prepare the neutral mono-
acetimino derivative [Rh(Cp*)Cl2(NHdCMe2)], which we
could not obtain from 1 and PPNCl, an orange suspension
of [Rh(Cp*)Cl(imam)]Cl (7‚Cl; imam ) κ2-N,N-4-imino-2-
methylpentan-2-amino) formed, in which the unexpected
imam ligand results from the aldol-like condensation of two
acetimino ligands (Scheme 2).
The homologous perchlorate salt [Rh(Cp*)Cl(imam)]ClO4
(7‚ClO4) was obtained in almost quantitative yield by reacting
7‚Cl with AgClO4 (1:1, acetone, 30 min) or 4 with PPNCl
(1:1, acetone, 7 h). Notice that the reaction of 4 with PPNCl
does not produce the substitution of acetimino by chloro to
give complex 3. In fact, 3 was not even detected in the
reaction mixture. Although 3 remains unchanged after being
stirred in acetone at room temperature for 24 h, we have
found that, surprisingly, it converts quantitatively into 7‚
ClO4 when the same acetone solution is stirred for 24 h under
a CO atmosphere of 1.8 bar, or is treated with a catalytic
amount of Ph2CdNH (1:0.1, 24 h). Complex 7‚ClO4 also
forms as the major product when 3 is reacted with an
(20) Curtis, N. F.; Powell, H. K. J.; Puschmann, H.; Rickard, C. E. F.;
Waters, J. M. Inorg. Chim. Acta 2003, 355, 25.
Inorganic Chemistry, Vol. 45, No. 1, 2006 185

Vicente et al.
Scheme 3 shows a reasonable proposal for this rearrange-
ment involving the imine-enamine tautomerization of one
of the ligands (A f B). This, along with the modified
geometrical and/or electronic properties of the complex,
could help the C-C coupling (C) that gives the imino-imido
intermediate (D) and a proton that would migrate to the
negatively charged imido nitrogen, the final step being the
dissociation of L to give 7‚ClO4.
Note that (i) the condensation involves the formation of a
new C-C bond and the transfer of one proton between two
nitrogen atoms without the need for an external base, (ii)
the added ligands responsible for the condensation act
catalytically, (iii) the changes necessary to effect condensa-
tion in 3 can be achieved by gentle heating, and (iv) any
ligand capable of replacing one of the acetimino ligands in
1‚ClO4, such as PPh3 or XyNC, precludes the synthesis of
7.
Figure 1. Ellipsoid representation of the cation in complex 3 (50%
probability level). Selected bond lengths (Å) and angles (deg): Rh(1)-
N(1) 2.096(2), Rh(1)-N(2) 2.104(2), Rh(1)-C(1) 2.160(2), Rh(1)-C(2)
2.163(3), Rh(1)-C(3) 2.128(3), Rh(1)-C(4) 2.172(2), Rh(1)-C(5) 2.171-
(2), Rh(1)-Cl(1) 2.4069(7), N(1)-C(12) 1.276(3), N(2)-C(15) 1.272(4);
N(1)-Rh(1)-N(2) 83.96(8), N(1)-Rh(1)-Cl(1) 92.15(6), N(2)-Rh(1)-
Cl(1) 88.82(6), C(12)-N(1)-Rh(1) 134.66(18), C(15)-N(2)-Rh(1) 133.64-
(19).
At present, we are studying the possibility of obtaining
complexes with the terdentate imino-bis(amino) ligand
NHdC(Me)CH2C(NH2)C(Me)CH2C(Me2)NH2 that would
result from the further reaction between the imino moiety
of a NHdC(Me)CH2C(NH2)Me2 ligand and an acetimino
ligand. With this intention, we attempted the synthesis
of [Rh(Cp*)(NHdCMe2){NHdC(Me)CH2C(NH2)Me2}]-
(ClO4)2 by reacting 7‚ClO4 with equimolar amounts of [Ag-
(NHdCMe2)2]ClO4 (CH2Cl2) or [Au(NHdCMe2)(PPh3)]-
ClO4 (acetone). However, although the complex [Rh(Cp*)-
(NHdCMe2){NHdC(Me)CH2C(NH2)Me2}](ClO4)2 is the
1
major product in both reactions (by H NMR (acetone-d6):
δ 1.19 (s, 3 H, Me), 1.45 (s, 3 H, Me), 1.81 (s, 15 H, Me,
2
Cp*), 2.07 (d, 1 H, CH2, JHH ) 17.4 Hz), 2.28 (s, 3 H,
4
Me), 2.41 (d, 3 H, Me, JHH ) 0.9 Hz), 2.45 (d, 3 H, Me,
2
4JHH ) 1.5 Hz), 2.63 (d, 1 H, CH2, JHH ) 17.4 Hz), 4.03
2
2
(d, 1 H, NH2, JHH ) 11.5 Hz), 4.58 (d, 1 H, NH2, JHH
)
11.5 Hz) 9.68 (s, br, 1 H, NH), 10.76 (s, br, 1 H, NH)), it is
contaminated with small amounts of 7‚ClO4, which so far
we have not been able to separate.
Crystal Structures of [Rh(Cp*)Cl(NHdCMe2)2]ClO4
(3) and [Rh(Cp*)Cl{NHdC(Me)CH2C(NMe2)NH2}]Cl (7‚
Cl). The structure of 3 involves two independent [Rh(Cp*)-
Cl(NHdCMe2)2]+ cations displaying only small differences
in bond distances and angles (one of them is represented in
Figure 1). Both cations, [Rh(Cp*)Cl(NHdCMe2)2]+ and [Rh-
(Cp*)Cl(imam)]+ (Figure 2), exhibit a pseudo-octahedral
“three-legged piano stool” geometry, with the Cp* group
occupying three fac coordination sites.
The Rh-Cl (3: 2.4069(7), 2.4114(7) Å; 7: 2.4074(5) Å),
Rh-N(amine) (7: 2.1539(16) Å), Rh-N(imine) (3: 2.092-
(2)-2.105(2) Å; 7: 2.0851(16) Å), and CdN (3: 1.267(3)-
1.283(3) Å; 7: 1.274(2) Å) bond distances are in the ranges
found for other Cp*-Rh(III) complexes (2.335-2.474,
2.016-2.214, 2.067-2.182, and 1.148-1.384 Å, re-
spectively, for Rh-Cl, Rh-N(amine), Rh-N(imine), and
CdN).9 The N-Rh-Cl (3: 92.15(6), 88.82(6), 92.38(6),
89.69(6)°; 7: 85.76(4), 86.11(5)°) and N-Rh-N (3: 83.96-
(8), 84.09(9)°; 7: 88.34(6)°) angles are close to those
expected for an octahedral disposition. The Cp*-Rh moieties
do not display special features.
Figure 2. Ellipsoid representation of complex 7‚Cl (50% probability level).
Selected bond lengths (Å) and angles (deg): Rh-N(1) 2.0851(16), Rh-
N(2) 2.1539(16), Rh-C(11) 2.1588(17), Rh-C(12) 2.1595(18), Rh-C(13)
2.1804(18), Rh-C(14) 2.1614(18), Rh-C(15) 2.1654(18), Rh-Cl(1)
2.4074(5), N(1)-C(2) 1.274(2), N(2)-C(4) 1.493(2); N(1)-Rh-N(2)
88.34(6), N(1)-Rh-Cl(1) 85.76(4), N(2)-Rh-Cl(1) 86.11(5), C(2)-N(1)-
Rh 130.92(14), C(4)-N(2)-Rh 118.77(11), N(1)-C(2)-C(3) 121.19(17),
C(2)-C(3)-C(4) 115.95(15), N(2)-C(4)-C(3) 108.02(15).
The cations of 3 aggregate into dimers (Figure 3 and
the Supporting Information) because of the formation of
C-H‚‚‚Cl hydrogen bonds. Additionally, each dimer is
hydrogen-bonded to two others via two perchlorate anions,
giving rise to a ribbon structure.
In complex 7‚Cl, the six-membered Rh-N(1)-C(2)-
C(3)-C(4)-N(2) chelate ring adopts a screw-boat confor-
mation with the C(3) and the C(4) atoms lying 0.27 Å below
and 0.57 Å above the plane, respectively, of the other four
atoms. The cations of 7‚Cl aggregate into dimers (Figure 4
and the Supporting Information) because of the formation
of N-H‚‚‚Cl hydrogen bonds between the coordinated
chlorine atom in one molecule and one of the NH2 hydrogen
186 Inorganic Chemistry, Vol. 45, No. 1, 2006

First Acetimino Complexes of Rh(III)
The 1H NMR spectra of 4-imino-2-methylpentan-2-amino
complexes 7-9 show three resonances for the inequivalent
methyl groups in the ranges 1.08-1.36, 1.25-1.63, and
2.40-2.56 ppm. In complexes 7‚Cl and 8, the groups are
all singlets, whereas in complexes 7‚ClO4 and 9, one of the
methyl groups (at 2.41 and 2.56 ppm, respectively) splits
into a doublet (4JHH ) 1.1 and 3 Hz, respectively), likely
due to coupling with the NH proton. The spectra also show
the NH2 and methylene protons to be inequivalent. The
former give rise to two doublets in the ranges 2.75-4.14
and 4.22-6.31 ppm with 2JHH values around 12 Hz, whereas
the latter are shown as an AB system (7‚Cl, 7‚ClO4, 9) in
the 2.19-2.87 ppm range or as two doublets (8, -0.08 and
1.90 ppm) with 2JHH values of 16-18 Hz. These assignments
1
have been confirmed by means of a H/13C HMQC experi-
ment carried out on complex 8, which proves the resonances
at -0.08 and 1.90 ppm in the 1H NMR spectrum are related
to that at 49.30 ppm in the 13C NMR spectrum (see below),
which is assigned to the CH2 carbon. The 31P NMR spectra
of phosphino compounds 2 and 8 show two doublets at 35.25
and 34.1 ppm, respectively, arising from coupling with 103Rh.
In the 13C{1H} NMR spectra of complexes 1-9, the Cp*
methyl carbon atoms are shown in the 8.35-10.13 ppm
interval as a singlet resonance or as a doublet due to coupling
Figure 3. Hydrogen bonds for 3.
2
with 31P (8, JCRh ) 1.1 Hz), whereas the Cp* ring carbon
atoms appear in the 93.66-103.91 ppm interval as a doublet
due to coupling with 103Rh (1JCRh ) 5.9-8.8 Hz) or as a
doublet of doublets due to the additional coupling with 31P
(2, 2JCP ) 2.4 Hz; 8, 2JCP ) 1.6 Hz). In complexes 1-9, the
CdN carbon gives a singlet resonance in the 185-192 ppm
range. In the acetimino complexes, the inequivalent Me
carbon atoms give two separate resonances. However,
although one of the methyl carbon atoms in complexes 1, 3,
5, and 6 is shown as a doublet that we attribute to coupling
with the trans 103Rh nucleus (3JCRh in the range of 1.2-2.2
Hz), this coupling is observed neither in the remaining
acetimino complexes (2, 4) nor in the amino-imino deriva-
tives 7-9.
IR Spectra. Complexes 1-9 show ν(N-H) and ν(CdN)
bands in the ranges 3161-3294 and 1644-1664 cm-1,
respectively. Additionally, the amino-imino complexes 7-9
show sharp δ(NH2) bands in the range 1583-1600 cm-1.
The isocyanide complexes 5 and 9 show the ν(C≡N) band
at 2170 and 2169 cm-1, respectively, and the acac complex
6 shows the expected ν(CdO) band at 1580 cm-1.21
Figure 4. Hydrogen bonds for 7‚Cl.
atoms in another molecule. Additionally, each of these dimers
is conected with four others through N-H‚‚‚Cl hydrogen
bonds in which both the NH and NH2 groups are involved.
NMR Spectra. The rhodium atom in complexes 2, 5, and
7-9 is chiral. However, in the absence of another chiral
center, only one resonance for each type of active nucleus
1
is observed. The H NMR spectra of complexes 1-9 show
the resonance due to the methyl protons of the Cp* group
in the 1.50-2.05 ppm range as a singlet (1, 3-7, 9) or as a
doublet (2, 8) due to coupling with 31P. Both the acetimino
and the 4-imino-2-methylpentan-2-amino complexes show
the NH imino proton as a broad resonance in the 8.69-11.39
ppm interval.
The 1H NMR spectra of acetimino complexes 1-6 show
two separate resonances for the methyl protons, indicating
inequivalence caused by restricted rotation around the Cd
N bond at room temperature. In the spectra of complexes 1
and 4, measured in DMSO-d6, both resonances are singlets;
for complexes 2, 3, 5, and 6, one of them splits into a doublet,
likely due to coupling with the trans-NH proton (4JHH, 0.6-
1.2 Hz), as we have previously observed in some acetimino-
gold(I)6 and -Rh(I)8 complexes.
Conclusions
The transmetalation reactions between [Ag(NHdCMe2)2]-
ClO4 or [Au(NHdCMe2)(PPh3)]ClO4 and Rh(III)-pentam-
ethylcyclopentadienylchloro complexes have allowed the
synthesis of mono-, bis-, and trisacetimino complexes, which
are the first Rh(III) derivatives with such a ligand. The aldol-
like condensation of two acetimino ligands into the imam
chelating ligand takes place in bis- or tris(acetimino)Rh(III)
complexes under mild experimental conditions, i.e., upon the
(21) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 4th ed.; John Wiley and Sons: New York, 1986.
Inorganic Chemistry, Vol. 45, No. 1, 2006 187

Vicente et al.
addition of labile ligands in excess (CO), stoichiometric (Cl-,
AsPh3), or even catalytic amounts (Ph2CdNH), or just upon
being stirred in solution at 70 °C, to give the first Rh
complexes with this ligand. This is the first report of the
synthesis of imam complexes of any metal from acetimino
complexes. We have proposed a reasonable reaction pathway
for the aldol-like condensation of two acetimino ligands that
supports the previous proposal of a template-type reaction
for the synthesis of the reported imam complexes.
Acknowledgment. We thank Ministerio de Educacio´n y
Ciencia and FEDER for a Grant (CTQ2004-05396) and a
Contract (I.V.-H.). R.G. thanks Cajamurcia (Spain) for a
grant. This Article is dedicated to Prof. Victor Riera, with
best wishes, on the occasion of his retirement.
Supporting Information Available: Tables of X-ray data for
the complexes in CIF format, hydrogen bond data. This material is
available free of charge via the Internet at http://pubs.acs.org.
IC051521W
188 Inorganic Chemistry, Vol. 45, No. 1, 2006