Aminocarbene Complexes as Intermediates in the Ruthenium-Assisted Aminolysis of Phenylacetylene to Isonitriles and Toluene

Article abstract of DOI:10.1021/om990050g

Various primary amines and NH₃ have been found to react in THF with the Ru(II) vinylidene complex fac,cis-[(PNP)RuCl₂{C=C(H)Ph}], affording aminocarbene derivatives of the general formula fac,cis-[(PNP)RuCl₂{C(NHR)(CH₂Ph)}] (PNP = CH₃CH₂CH₂N(CH₂-CH ₂PPh₂)₂; R = CH₃CH₂CH₂) Ph, cyclo-C₆H₁₁, (R)-(+)-CH(Me)(Ph), (R)-(-)-CH(Me)(Et), (S)-(-)-CH(Me)(1-naphthyl), H). With piperidine as the starting material, the tertiary aminocarbene /ac,cis-[(PNP)RuCl₂{C(NC₅H₁₀)(CH ₂Ph)}] has been obtained. The aminocarbene complexes are formed through an unforeseen mechanism in which 2 equiv of amine is involved: one serves to deprotonate the vinylidene C_β carbon atom, while the other coordinates the metal center and then brings about an intramolecular nucleophilic attack onto the C_α carbon atom of a σ-phenylethynyl ligand. The (phenylethynyl)amine intermediates have been isolated and characterized. The aminocarbene derivative foc,cis-[(PNP)RuCl₂-{C(NH(S)-(-)-CH(Me)(1-naphthyl)XCH ₂Ph)}] has been authenticated by a single-crystal X-ray diffraction analysis. Upon thermolysis in wet solvents, generally THF, the secondary aminocarbene complexes generate toluene and transform quantitatively into the corresponding isonitrile derivatives fac,cis-[(PNP)RuCl₂(C=NR)] (R = CH₃CH₂CH₂) Ph, cyclo-C₆H₁₁, (R)-(+)-CH(Me)Ph, (R)-(-)-CH(Me)Et). In contrast, the primary aminocarbene fac,cis-[(PNP)-RuCl₂{C(NH₂)(CH₂Ph)}] and the tertiary aminocarbene [(PNP)RuCl₂{C(NC₅H₁₀)(CH₂Ph)}] are thermally stable up to 150°C. The mechanism for the aminocarbene to isonitrile conversion has been found to involve the intermediacy of iminoacyl and (benzyl)isonitrile Ru(II) compounds, which have been intercepted and identified from independent reactions.

Full text of DOI:10.1021/om990050g

2376
Organometallics 1999, 18, 2376-2386
Am in oca r ben e Com p lexes a s In ter m ed ia tes in th e
Ru th en iu m -Assisted Am in olysis of P h en yla cetylen e to
Ison itr iles a n d Tolu en e
Claudio Bianchini,* Dante Masi, Antonio Romerosa, Fabrizio Zanobini, and
Maurizio Peruzzini*
Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione,
ISSECC-CNR, Via J . Nardi 39, 50132 Firenze, Italy
Received J anuary 26, 1999
Various primary amines and NH3 have been found to react in THF with the Ru(II)
vinylidene complex fac,cis-[(PNP)RuCl2{CdC(H)Ph}], affording aminocarbene derivatives
of the general formula fac,cis-[(PNP)RuCl2{C(NHR)(CH2Ph)}] (PNP ) CH3CH2CH2N(CH2-
CH2PPh2)2; R ) CH3CH2CH2, Ph, cyclo-C6H11, (R)-(+)-CH(Me)(Ph), (R)-(-)-CH(Me)(Et), (S)-
(-)-CH(Me)(1-naphthyl), H). With piperidine as the starting material, the tertiary ami-
nocarbene fac,cis-[(PNP)RuCl2{C(NC5H10)(CH2Ph)}] has been obtained. The aminocarbene
complexes are formed through an unforeseen mechanism in which 2 equiv of amine is
involved: one serves to deprotonate the vinylidene Câ carbon atom, while the other
coordinates the metal center and then brings about an intramolecular nucleophilic attack
onto the CR carbon atom of a σ-phenylethynyl ligand. The (phenylethynyl)amine intermedi-
ates have been isolated and characterized. The aminocarbene derivative fac,cis-[(PNP)RuCl2-
{C(NH(S)-(-)-CH(Me)(1-naphthyl))(CH2Ph)}] has been authenticated by a single-crystal
X-ray diffraction analysis. Upon thermolysis in wet solvents, generally THF, the secondary
aminocarbene complexes generate toluene and transform quantitatively into the correspond-
ing isonitrile derivatives fac,cis-[(PNP)RuCl2(CtNR)] (R ) CH3CH2CH2, Ph, cyclo-C6H11,
(R)-(+)-CH(Me)Ph, (R)-(-)-CH(Me)Et). In contrast, the primary aminocarbene fac,cis-[(PNP)-
RuCl2{C(NH2)(CH2Ph)}] and the tertiary aminocarbene [(PNP)RuCl2{C(NC5H10)(CH2Ph)}]
are thermally stable up to 150 °C. The mechanism for the aminocarbene to isonitrile
conversion has been found to involve the intermediacy of iminoacyl and (benzyl)isonitrile
Ru(II) compounds, which have been intercepted and identified from independent reactions.
In tr od u ction
found to attack the CR carbon atom of disubstituted
vinylidene ligands to give aminocarbene derivatives.3,10
It is generally agreed that the formation of the amino-
carbene group proceeds via an intermolecular-concerted
process in which the primary amine adds across the
highly polarized C-C double bond (Scheme 1).3,10 In this
concerted process, the metal center does not seem to
play a direct role in assisting the hydroamination
reaction of the C-C double bond, although the metal
does control the electronic nature and consequently the
reactivity of the vinylidene ligand.11
The reactivity of the metal-vinylidene moiety is
dominated by the electrophilicity of the R-carbon atom.
Several examples of addition of nucleophiles, including
water1-4 alcohols,1,3,5 thiols,3,6 phosphines,7 and fluoride8
and cyanide ions9 have been reported. Primary amines
conform to this general protocol, as they have been
(1) Bianchini, C.; Marchi, A.; Marvelli, L.; Peruzzini, M.; Romerosa,
A.; Rossi, R. Organometallics 1996, 15, 3804 and references therein.
(2) Bianchini, C.; Casares, J . A.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. J . Am. Chem. Soc. 1996, 118, 4585.
In this paper we describe the synthesis of a new
family of ruthenium aminocarbene complexes and re-
port experimental evidence of a different mechanism for
the hydroamination reaction of the vinylidene functional
group. In addition, we show that aminocarbene com-
plexes are effective precursors, by simple thermolysis,
to products containing isonitrile ligands with various
organic substituents. Despite their environmentally
(3) Boland-Lussier, B. E.; Hughes, R. P. Organometallics 1982, 1,
635.
(4) (a) Bruce, M. I.; Swincer, A. G. Aust. J . Chem. 1980, 33, 147. (b)
Sullivan, B. P.; Smythe, R. S.; Kober, E. M.; Meyer, T. J . J . Am. Chem.
Soc. 1982, 104, 4701. (c) Mountassir, C.; Ben-Hadda, T.; Le Bozec, H.
J . Organomet. Chem. 1990, 388, C13. (d) Knaup, W.; Werner, H. J .
Organomet. Chem. 1991, 411, 471.
(5) Bruce, M. I.; Swincer, A. J . Organomet. Chem. 1979, 171, C5.
(6) Bianchini, C.; Glendenning, L.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. J . Chem. Soc., Chem. Commun. 1994, 2219.
(7) (a) Boland-Lussier, B. E.; Churchill, M. R.; Hughes, R. P.;
Rheingold, A. L. Organometallics 1982, 1, 628. (b) Senn, D. R.; Wong,
A.; Patton, A. T.; Marsi, M.; Strokes, C. E.; Gladysz, J . A. J . Am. Chem.
Soc. 1988, 110, 6096. (c) Bianchini, C.; Meli, A.; Peruzzini, M.; Zanobini,
F.; Zanello, P. Organometallics 1990, 9, 241.
(10) Gamasa, M. P.; Gimeno, J .; Lastra, E.; Lanfranchi, M.; Tirip-
icchio, A. J . Organomet. Chem. 1992, 430, C39.
(11) (a) Bruce, M. I. Chem. Rev. 1991, 91, 197. (b) Bruce, M. I.;
Swincer, A. G. Adv. Organomet. Chem. 1983, 22, 59. (c) Davies, S. G.;
McNally, J . P.; Smallridge, A. J . Adv. Organomet. Chem. 1990, 30, 1.
(d) Antonova, A. B.; Ioganson, A. A. Russ. Chem. Rev. (Engl. Transl.)
1989, 58, 593.
(8) Ting, P.-C.; Lin, Y.-C.; Lee, G.-H.; Cheng, M.-C.; Wang, Y. J . Am.
Chem. Soc. 1996, 118, 6433.
(9) Davies, S. G.; Smallridge, A. J . J . Organomet. Chem. 1991, 413,
313.
10.1021/om990050g CCC: $18.00 © 1999 American Chemical Society
Publication on Web 05/20/1999

Aminocarbene Complexes in Ru-Assisted Aminolysis
Organometallics, Vol. 18, No. 12, 1999 2377
LiAlH4 and P2O5, respectively. Amines were purchased from
Aldrich, their purity was checked by 1H NMR spectroscopy,
and, when necessary, they were dried over KOH and distilled
from BaO under an Ar or N2 atmosphere prior to use. All the
other reagents and chemicals were reagent grade and, unless
otherwise stated, were used as received by commercial sup-
pliers. All reactions and manipulations were routinely per-
formed under a dry nitrogen atmosphere by using standard
Schlenk-tube techniques. The solid complexes were collected
on sintered-glass frits and washed with light petroleum ether
(bp 40-60 °C) before being dried in a stream of nitrogen. The
ligand CH3CH2CH2N(CH2CH2PPh2)2 (PNP)21 and the com-
plexes mer,trans-[(PNP)RuCl2(PPh3)] (1),22,23 and fac,cis-[(PNP)-
RuCl2{CdC(H)Ph}] (2)24 were prepared as described in the
literature. Deuterated solvents for NMR measurements (Merck
and Aldrich) were dried over molecular sieves (0.4 nm). 1H and
13C{1H} NMR spectra were recorded on Varian VXR 300,
Bruker AC200, or Bruker AVANCE DRX 500 spectrometers
operating at 299.94, 200.13, or 500.13 MHz (1H) and 75.42,
50.32, or 125.80 MHz (13C), respectively. Peak positions are
relative to tetramethylsilane and were calibrated against the
residual solvent resonance (1H) or the deuterated solvent
multiplet (13C). 13C-DEPT experiments were run on the Bruker
Sch em e 1
hostile nature,12 isonitriles are indeed useful ligands in
coordination, organometallic chemistry, and catalysis.13
Very few isonitriles, however, are commercially avail-
able due to their tendency for polymerization as well
as the complicated synthetic procedures.12 For this
reason, several metal-mediated syntheses have been
developed with the ultimate goal of assembling the
isonitrile moiety from less toxic and readily available
reagents. Common procedures involve (i) the attack of
primary amines on dihalo-, thio-, and dithiocarbene
complexes,14,15 (ii) the oxidative addition of Cl2CNPh to
low-valent metal complexes,16 and (iii) the alkylation
of transition-metal cyanides.17 An effective protocol for
the synthesis of isonitriles would be the isomerization
of nitriles which can catalytically be produced by Ru(II)-
assisted dehydrogenation of amines.18,19 Unfortunately,
no example of nitrile to isonitrile isomerization via
amine oxidation has been reported so far. Although
restricted to a precise metal fragment, the novel syn-
thetic procedure described in this work has the great
advantages of being quite simple and selective and of
providing access to a large variety of isonitrile ligands,
including optically pure derivatives.
1
AC200 spectrometer. H,13C-2D HETCOR NMR experiments
were recorded on either the Bruker AC200 spectrometer using
the XHCORR pulse program or the Bruker AVANCE DRX 500
spectrometer equipped with a 5 mm triple-resonance probe
head for 1H detection and inverse detection of the hetero-
nucleus (inverse correlation mode, HMQC experiment, with
1
no sample spinning). The H,1H-2D COSY NMR experiments
were routinely conducted on the Bruker AC200 instrument
in the absolute magnitude mode using a 45 or 90° pulse after
the incremental delay or were acquired on the AVANCE DRX
500 Bruker spectrometer using the phase-sensitive TPPI mode
with double quantum filter. 31P{1H} NMR spectra were
recorded on either the Varian VXR 300 or Bruker AC200
instrument operating at 121.42 or 81.01 MHz, respectively.
Chemical shifts were measured relative to external 85% H3-
PO4 with downfield values taken as positive. The proton NMR
spectra with broad-band phosphorus decoupling were recorded
on the Bruker AC200 instrument equipped with a 5 mm
inverse probe and a BFX-5 amplifier device using the wide-
band phosphorus decoupling sequence GARP. Infrared spectra
were recorded as Nujol mulls on a Perkin-Elmer 1600 series
FT-IR spectrometer between KBr plates. A Shimadzu GC-14A/
GCMS-QP2000 instrument was employed for all GC-MS
investigations. Elemental analyses (C, H, N) were performed
using a Carlo Erba Model 1106 elemental analyzer.
Syn th esis of th e Secon d a r y Am in oca r ben e Com p lexes
fa c,cis-[(P NP )Ru Cl2{C(NHR)(CH2P h )}] (R ) CH3CH2CH2
(3), P h (4), cyclo-C6H11 (5), (R)-(+)-CH(Me)(P h ) (6), (R)-
(-)-CH(Me)(Et) (7), (S)-(-)-CH(Me)(1-n a p h th yl) (8)). A
3-fold excess of the appropriate primary amine, NH2R (R )
CH3CH2CH2, Ph, cyclo-C6H11, (R)-(+)-CH(Me)(Ph), (R)-(-)-CH-
(Me)(Et), (S)-(-)-CH(Me)(1-naphthyl), was syringed at room
temperature into a stirred suspension of the vinylidene
complex 2 (0.40 g, 0.53 mmol) in 30 mL of THF. The reaction
mixture was stirred in the dark for 1 h to give a canary yellow
solution which was evaporated to ca. 5 mL. Addition of light
petroleum ether gave canary yellow microcrystals of the
aminocarbene complex, which were recrystallized from CH2-
Cl2 and light petroleum ether. Yield: ca. 90%.
A preliminary communication of part of this work has
already appeared.20
Exp er im en ta l Section
Gen er al P r ocedu r es. Tetrahydrofuran (THF) and dichloro-
methane were purified by distillation under nitrogen over
(12) Walboorsky, H. M.; Periasami, M. P. In The Chemistry of Triple-
Bonded Functional Groups; Patai, S., Ed.; Wiley: Chichester, U.K.,
1992; Vol. 31, Chapter 20.
(13) (a) Malatesta, L. Prog. Inorg. Chem. 1959, 1, 283. (b) Malatesta,
L.; Bonati, F. Isonitrile Complexes of Metals; Wiley: New York, 1969.
(c) Treichel, P. M. Adv. Organomet. Chem. 1973, 11, 21. (d) Bonati, F.;
Minghetti, G. Inorg. Chim. Acta 1974, 9, 95. (e) Yamamoto, Y. Coord.
Chem. Rev. 1980, 32, 193. (f) Singleton, E.; Oosthuizer, H. E. Adv.
Organomet. Chem. 1983, 22, 209.
(14) Mansuy, D.; Lange, M.; Chottard, J . C.; Bartali, J . F. Tetrahe-
dron Lett. 1978, 3027.
(15) (a) Greaves, W. M.; Angelici, R. J . Inorg. Chem. 1981, 20, 2983.
(b) McCormick, F. B.; Angelici, R. J . Inorg. Chem. 1979, 18, 1231. (c)
Pickering, R. A.; Angelici, R. J . Inorg. Chem. 1981, 20, 2877. (d)
Steinmetz, A. L.; Hershberger, S. A.; Angelici, R. J . Organometallics
1984, 3, 461. (e) Albano, V. G.; Bordoni, S.; Braga, D.; Busetto, C.;
Palazzi, A.; Zanotti, V. Angew. Chem., Int. Ed. Engl. 1991, 30, 847. (f)
Faraone, F.; Piraino, P.; Marsala, V.; Sergi, S. J . Chem. Soc., Dalton
Trans. 1977, 859.
(16) Fehlammer, W. P.; Mayr, A.; Olgemoeller, B. Angew. Chem.,
Int. Ed. Engl. 1975, 14, 369.
(17) See for example: (a) Baird, G. J .; Davies, S. G. J . Organomet.
Chem. 1984, 262, 215. (b) Bianchini, C.; Laschi, F.; Ottaviani, M. F.;
Peruzzini, M.; Zanello, P.; Zanobini. F. Organometallics 1989, 8, 893.
(c) Richter-Addo, G. B.; Knight, D. A.; Dewey, M. A.; Arif, A. M.;
Gladysz, J . A. J . Am. Chem. Soc. 1993, 111, 11863.
(18) Mixed amine-phosphine complexes of ruthenium(II) have been
reported; see for example: Fogg, D. E.; J ames, B. R. Inorg. Chem. 1995,
34, 2557.
(19) (a) Diamond, S. E.; Tom. G. M.; Taube, H. J . Am. Chem. Soc.
1975, 97, 2661. (b) Adcock, P. A.; Keene, F. R. J . Am. Chem. Soc. 1981,
103, 6494. (c) Bailey, A. J .; J ames, B. R. J . Chem. Soc., Chem. Commun.
1996, 2343 and references therein.
fa c,cis-[(P NP )Ru Cl2{C(N(H)CH3CH2CH2)(CH2P h )}] (3).
Anal. Calcd for C42H50N2Cl2P2Ru: C, 61.76; H, 6.17; N, 3.43.
(21) Sacconi, L.; Morassi, R. J . Chem. Soc. A 1969, 2904.
(22) Bianchini, C.; Innocenti, P.; Masi, D.; Peruzzini, M.; Zanobini,
F. Gazz. Chim. Ital. 1992, 122, 461.
(23) Bianchini, C.; Masi, D.; Peruzzini, M.; Romerosa, A.; Zanobini,
F. Acta Crystallogr. 1995, C51, 2514.
(20) Bianchini, C.; Peruzzini, M.; Romerosa, A.; Zanobini, F. Orga-
nometallics 1995, 14, 3152.
(24) Bianchini, C.; Innocenti, P.; Peruzzini, M.; Romerosa, A.;
Zanobini, F. Organometallics 1996, 15, 272

2378 Organometallics, Vol. 18, No. 12, 1999
Bianchini et al.
Found: C, 61.55; H, 6.26; N, 3.32. IR: ν(NH) 3450 cm-1 (br,
w). 31P{1H} NMR (22 °C, CDCl3, 121.42 MHz): δ 51.31 (s). 1H
NMR (22 °C, CD2Cl2, 299.94 MHz): δNH 10.62 (br s, 1H), δCH
mL of n-hexane led to the precipitation of yellow microcrystals
of fac,cis-[(PNP)RuCl2{C(NH2)(CH2Ph)}] (9), which were fil-
tered off and washed several times with light petroleum ether
before being dried in vacuo. Recrystallization from CH2Cl2 and
light petroleum ether (2:1 v/v) gave 9 as light yellow crystals.
Yield: 86%. Anal. Calcd for C39H44N2Cl2P2Ru: C, 60.46; H,
5.72; N, 3.62. Found: C, 60.19; H, 5.94; N, 3.56. IR: ν(NH)
3383 (m), 3276 cm-1 (w). 31P{1H} NMR (22 °C, CDCl3, 81.01
MHz): δ 53.36 (s). 1H NMR (22 °C, CD2Cl2, 200.13 MHz): δNH
10.14, 8.34 (br singlets, 1H each), δCH 4.65 (s, 2H). 13C{1H}
Ph
2
4.58 (s, 2H), δNCH
3.30 (t, 3J (HH) ) 7.1 Hz, 2H),
CH CH
2
2
3
δNCH
3 1.67 (sextet, 3J (HH) ) 7.1 Hz, 2H), δNCH
3 0.96
CH CH
CH CH
2
2
2
2
(t, J (HH) ) 7.1 Hz, 3H). 13C{1H} NMR (22 °C, CD2Cl2, 75.42
3
MHz): δRudC 254.4 (t, 2J (CP) ) 11.6 Hz), δCH
δNCH
59.0 (s),
12.1 (s).
CH CH
2 2 3
Ph
2
52.8 (s), δNCH
23.2 (s), δNCH
CH CH
2
CH CH
2
3
2
2
3
fa c,cis-[(P NP )R u Cl2{C(N(H )P h )(CH2P h )}] (4). Anal.
Calcd for
C45H48N2Cl2P2Ru: C, 63.53; H, 5.69; N, 3.29.
Ph
2
NMR (22 °C, CD2Cl2, 50.32 MHz): δRudC 261.6 (t, 2J (CP) )
Found: C, 63.44; H, 5.56; N, 3.21. IR: ν(NH) 3466 cm-1 (br,
w). 31P{1H} NMR (22 °C, CDCl3, 121.42 MHz): δ 50.17 (s); 1H
NMR (22 °C, CDCl3, 299.94 MHz): δNH 12.35 (s, 1H), δCH
11.4 Hz), δCH 58.7 (s).
Ph
2
Syn th esis of th e Ter tia r y Am in oca r ben e Com p lex
fa c,cis-[(P NP )Ru Cl2{C(NC5H10)(CH2P h )}] (10). Complex 10
was prepared as described above for the secondary aminocar-
bene complexes by using piperidine in place of primary amines.
Anal. Calcd for C44H52N2Cl2P2Ru: C, 62.70; H, 6.22; N, 3.32.
Found: C, 62.48; H, 6.17; N, 3.12. 31P{1H} NMR (22 °C, C6D6,
81.01 MHz): δ 50.07. 1H NMR (22 °C, C6D6, 200.13 MHz):
δCH 4.62 (s). 13C{1H} NMR (22 °C, C6D6, 50.32 MHz): δRudC
Ph
2
4.88 (s, 2H). 13C{1H} NMR (20 °C, CDCl3, 75.42 MHz): δRudC
2
264.9 (t, J (CP) ) 11.7 Hz), δCH
59.8 (s).
Ph
2
fa c,cis-[(P NP )Ru Cl2{C(N(H)-cyclo-C6H11)(CH2P h )}] (5).
Anal. Calcd for C45H54N2Cl2P2Ru: C, 63.08; H, 6.35; N, 3.27.
Found: C, 62.96; H, 6.31; N, 3.26. IR: ν(NH) 3440 cm-1 (br,
1
w). 31P{1H} NMR (22 °C, CDCl3, 81.01 MHz): δ 49.73 (s). H
NMR (22 °C, CD2Cl2, 200.13 MHz): δNH 10.69 (br d, J (HH) )
Ph
2
252.4 (t, 2J (CP) ) 14.2 Hz), δCH Ph 57.9 (s), δCH2(piperidine) 51.8,
9.3 Hz, 1H), δCH 4.69 (s, 2H), δNCH(cyclohexyl) 3.65 (m, 1H),
Ph
2
2
27,7, 25.4 (all s).
δCH2(cyclohexyl) 1.2-2.5 (m, superimposed to the PNP aliphatic
protons). 13C{1H} NMR (23 °C, CD2Cl2, 50.32 MHz): δRudC
Syn th esis of th e P h en yleth yn yl-Am in e Com p lexes
fa c-[(P NP )Ru Cl(CtCP h )(NH2R)] (R ) CH3CH2CH2 (11),
cyclo-C6H11 (12), (R)-(-)-CH(Me)Et (13)). Meth od A. To a
solution of 2 (0.40 g, 0.53 mmol) in 25 mL of THF was added
2 equiv of the appropriate primary amine with vigorous
stirring. After the yellow solution was stirred for 3 h, it was
concentrated to ca. half its volume. The addition of 20 mL of
n-hexane, followed by slow concentration under nitrogen, gave
the alkynyl complexes fac-[(PNP)RuCl(CtCPh)(NH2R)] (R )
CH3CH2CH2 (11), cyclo-C6H11 (12), (R)-(-)-CH(Me)Et (13)) in
yields higher than 90%. While 11 was obtained as a pure
product, 12 (and 13) were always contaminated by variable
amounts (<10%) of 5 (and 7).
Meth od B. To a solution of 2 (0.40 g, 0.53 mmol) in 25 mL
of CH2Cl2 was added 2 equiv of the appropriate primary amine
in water (25 mL) with vigorous stirring. The resulting biphasic
system was vigorously stirred for 2 h at room temperature in
the dark. The organic layer was separated, dried over MgSO4
or Na2SO4, and then concentrated to ca. 5 mL under vacuum.
Addition of light petroleum ether (10 mL) gave pale yellow
microcrystals of the alkynyl-amine complexes fac-[(PNP)-
RuCl(CtCPh)(NH2R)] (R ) CH3CH2CH2 (11), cyclo-C6H11 (12),
(R)-(-)-CH(Me)Et (13)) in yields ranging from 76 to 89%. The
crude products were recrystallized from CH2Cl2/n-hexane
solution.
251.9 (t, 2J (CP) ) 11.6 Hz), δCH
58.4 (s), δNCH(cyclohexyl)
58.5 (s), δCH2(cyclohexyl) 33.3, 25.9, 25.2 (all s).
Ph
2
(R )-(+)-fa c,cis-[(P NP )R u Cl2{C(N(H )CH Me P h )(CH 2-
P h )}] (6). Anal. Calcd for C47H52N2Cl2P2Ru: C, 64.23; H, 5.96;
N, 3.19. Found: C, 64.08; H, 5.89; N, 3.11. IR: ν(NH) 3460
cm-1 (br, w). 31P{1H} NMR (22 °C, CDCl3, 81.01 MHz): AB
2
1
system, δA 50.32, δB 48.04, J (PAPB) ) 29.7 Hz. H NMR (22
3
°C, CD2Cl2, 200.13 MHz): δNH 11.13 (br d, J (HH) ) 9.6 Hz,
1H), δCHMe 4.94 (dq, 3J (HH) ) 9.6, 6.6 Hz, 1H), δCH
4.80,
Ph
2
4.48 (AB system, 3J (HH) ),16.8 Hz, 2H), δCHMe 1.58 (d, 3J (HH)
) 6.6 Hz, 3H). 13C{1H} NMR (22 °C, CD2Cl2, 75.42 MHz): δRud
255.3 (t, 2J (CP) ) 11.3 Hz), δCHMe 59.3 (s), δCH
58.6 (t,
Ph
C
2
3J (CP) ) 4.6 Hz), δCHMe 24.6 (s).
(R )-(-)-fa c,cis-[(P NP )R u Cl2{C(N(H )CH Me E t )(CH 2-
P h )}] (7). Anal. Calcd for C43H52N2Cl2P2Ru: C, 62.16; H, 6.31;
N, 3.37. Found: C, 62.05; H, 6.44; N, 3.20. IR: ν(NH) 3440
cm-1 (br, w). 31P{1H} NMR (22 °C, CDCl3, 81.01 MHz): AB
2
1
system, δA 51.21, δB 50.59, J (PAPB) ) 28.2 Hz. H NMR (25
3
°C, CD2Cl2, 500.13 MHz): δNH 10.82 (br d, J (HH) ) 9.6 Hz,
1H), δCH
4.70, 4.54 (AB system, 2J (HH) ) 17.1 Hz, 2H),
Ph
2
δCH(Me)Et 3.70 (m, 1H), δCH(Me)CH 3 1.81, 1.64 (m, diastereotopic
CH
2
protons, 2H), δCH(Me)Et 1.36 (d, 3J (HH) ) 6.4 Hz, 3H), δCH(Me)CH
CH
2
3
1.06 (t, J (HH) ) 7.4 Hz, 3H). 13C{1H} NMR (25 °C, CD2Cl2,
3
2
125.80 MHz): δRudC 251.3 (t, J (CP) ) 11.4 Hz), δCH(Me)Et 57.0
(s), δCH
56.5 (s), δCH(Me)CH
30.4 (s), δCH(Me)Et 20.6 (s),
After concentration of the water phase under reduced
pressure, the corresponding ammonium salt [NH3R]Cl was
isolated in quantitative yield.
Ph
CH
2
2
3
δCH(Me)CH
12.6 (s).
CH
2
3
(S)-(-)-fa c,cis-[(P NP )Ru Cl2{C[N(H)CHMe(1-n a p h th yl)]-
(CH2P h )}] (8). Anal. Calcd for C51H54N2Cl2P2Ru: C, 65.94;
H, 5.86; N, 3.02. Found: C, 65.86; H, 5.89; N, 2.92. IR: ν(NH)
3460 cm-1 (br, w). 31P{1H} NMR (22 °C, CDCl3, 81.01 MHz):
fa c-[(P NP )R u Cl(CtCP h )(NH 2CH 3CH 2CH 2)]
Yield: 92% (method A), 85% (method B). Anal. Calcd for
42H49N2ClP2Ru: C, 64.65; H, 6.33; N, 3.59. Found: C, 64.54;
(11).
C
2
1
AB system, δA 51.25, δB 48.03, J (PAPB) ) 29.9 Hz. H NMR
H, 6.39; N, 3.28. IR: ν(NH) 3320 (w), ν(CtC) 2054 (vs), 1999
3
(22 °C, CD2Cl2, 200.13 MHz): δNH 11.46 (br d, J (HH) ) 9.3
cm-1 (sh, m). 31P{1H} NMR (20 °C, CD2Cl2, 81.01 MHz): AB
3
2
1
Hz, 1H), δCH(Me)Np 5.85 (dq, J (HH) ) 9.3, 6.6 Hz, 1H), δCH
system, δA 58.89, δB 57.13, J (PAPB) ) 34.9 Hz. H NMR (20
°C, CD2Cl2, 500.13 MHz): δNH 2.10 (br s, 2H), δNH
Ph
2
4.80, 4.47 (AB system, 2J (HH) ) 17.1 Hz, 2H), δCHMeNp 1.75
CH CH CH
3
2
2
2
2
(d, J (HH) ) 6.6 Hz, 3H). 13C{1H} NMR (22 °C, CD2Cl2, 50.32
3.4-2.1 (m, superinposed with PNP aliphatic protons),
3
MHz): δRudC 255.8 (t, 2J (CP) ) 11.6 Hz), δCH Ph 59.5 (s), δCHMeNp
δNH
0.63 (t, J (HH) ) 7.2 Hz). 13C{1H} NMR (22 °C,
3
CH CH CH
3
2
2
2
2
58.4 (s), δCHMeNp 24.4 (s).
CD2Cl2, 50.32 MHz): δRuC 138.0 (dd, 2J (CP) ) 20.0, 6.1 Hz),
CtC 112.8 (s), δNCH 56.9 (s), δNCH 27.7 (s), δNCH
δ
Syn th esis of th e P r im a r y Am in oca r ben e Com p lexes
fa c,cis-[(P NP )Ru Cl2{C(NH2)(CH2P h )}] (9). A regular stream
of NH3 was slowly bubbled through an orange solution of 2
(0.40 g, 0.53 mmol) in CHCl3 (30 mL) for 30 min. During this
period the solution become yellow, while a colorless solid
separated. The ammonia was then replaced by nitrogen, and
the solution was slowly heated to the boiling point and then
refluxed with stirring for 2 h. During this time the solid
dissolved to give a bright yellow solution, which was evapo-
rated under a brisk current of nitrogen to ca. 8 mL. After the
residue was cooled to room temperature, the addition of 15
CH CH
2
CH CH
CH CH
2 2 3
2
3
2
2
3
12.4 (s).
fa c-[(P NP )R u Cl(CtCP h ){NH 2-cyclo-C6H 11}]
(12).
Yield: 89% (method B). Anal. Calcd for C45H53N2ClP2Ru: C,
65.88; H, 6.51; N, 3.41. Found: C, 65.43; H, 6.26; N, 3.16. IR:
ν(NH) 3318 (w), ν(CtC) 2058 (vs), 1997 cm-1 (sh, m). 31P{1H}
NMR (CD2Cl2, 81.01 MHz): fluxional AB system at 22 °C, δA
58.0 (br), δB 56.8 (br), 2J (PAPB) ≈ 33 Hz; AB system at -50
°C, δA 58.08, δB 56.25, 2J (PAPB) ) 35.2 Hz. 1H NMR (22 °C,
CD2Cl2, 200.13 MHz): δNH not assigned, likely buried in the
2
crowded aliphatic region of the spectrum. 13C{1H} NMR (22

Aminocarbene Complexes in Ru-Assisted Aminolysis
Organometallics, Vol. 18, No. 12, 1999 2379
°C, CD2Cl2, 50.32 MHz): δRuC 138.4 (t, 2J (CP) ) 10.4, 6.1 Hz),
δCtC 112.4 (s), δNCH 53.2 (s).
(B) Rea ction of fa c-[(P NP )Ru Cl(CtCP h ){NH2(cyclo-
C6H11)}] (12) w ith [NH3(CH3CH2CH2)]Cl. A 5 mm NMR
tube was charged under nitrogen with 12 (20 mg, 0.024 mmol),
[NH3(CH3CH2CH2)]Cl (2.5 mg, 0.026 mmol), and THF-d8 (0.8
mL). The tube was shaken for 30 s and then placed into a NMR
probe. 31P{1H} NMR analysis of the reaction revealed the
conversion of 12 to 5. Occasionally, 3 was also formed (e5%).
The composition of the reaction mixture did not change over
a period of 2 days at room temperature.
Rea ction of fa c-[(P NP )Ru Cl(CtCP h ){NH2R}] w ith CO.
Carbon monoxide was bubbled throughout a stirred CH2Cl2
solution (10 mL) of 11-14 (ca. 100 mg) at room temperature
for 20 min. Addition of ethanol (10 mL), followed by slow
concentration under nitrogen, gave pale yellow microcrystals
of the known alkynyl-carbonyl complex fac-[(PNP)RuCl(Ct
CPh)(CO)] (15): yield 95%.24
Syn th esis of th e Ison itr ile Com p lexes fa c,cis-[(P NP )-
Ru Cl2(CtNR)] (R ) CH3CH2CH2 (16), P h (17), cyclo-C6H11
(18), (R)-(+)-CH(Me)P h (19), (R)-(-)-CH(Me)Et (20)). A
solution of 0.5 mmol (0.41-0.44 g) of the aminocarbene
complexes 3-7 in 50 mL of THF/H2O (20:1 v/v) was introduced
into a 100 mL Schlenk flask equipped with a stirring bar, a
reflux condenser, and a nitrogen inlet. The canary yellow
solution was gently refluxed for ca. 16 h. During this time,
the yellow color faded to give a pale yellow solution, which
was evaporated to dryness under vacuum. The solid residue
was washed with n-pentane (2 × 5 mL), dissolved in ca. 15
mL of CH2Cl2, and dried over MgSO4 for ca. 30 min. The CH2-
Cl2 solution was then filtered, and its volume was reduced to
ca. 5 mL under reduced pressure. Addition of light petroleum
ether (bp 40-60 °C, 10 mL) gave cream-colored microcrystals
of the isonitrile complexes fac,cis-[(PNP)RuCl2(CtNR)] (R )
CH3CH2CH2 (16), Ph (17), cyclo-C6H11 (18), (R)-(+)-CH(Me)-
Ph (19), (R)-(-)-CH(Me)Et (20)). The yields were generally
higher than 90%.
fa c-[(P NP )Ru Cl(CtCP h )(NH2(R)-(-)-CH(Me)Et)] (13).
Yield: 76% (method B). Anal. Calcd for C43H51N2ClP2Ru: C,
65.02; H, 6.47; N, 3.53. Found: C, 65.28; H, 6.60; N, 3.38. IR:
ν(NH) 3320 (w), ν(CtC) 2057 cm-1 (vs). 31P{1H} NMR (CD2-
Cl2, 81.01 MHz): fluxional AB system at 22 °C, δA 57.6 (v br),
2
δB 56.7 (v br); AB system at 0 °C, δA 57.82, δB 56.44, J (PAPB)
1
) 34.1 Hz. H NMR (22 °C, CDCl3, 200.13 MHz): δNH 2.3 (br
2
s, 2H). 13C{1H} NMR (22 °C, CD2Cl2, 50.32 MHz): δRuC 137.2
(dd, J (CP) ) 10.0, 6.8 Hz), δCtC 112.7 (t, J (CP) ) 3.5 Hz).
2
3
Syn th esis of th e P h en yleth yn yl-Am m on ia Com p lex
fa c-[(P NP )Ru Cl(CtCP h )(NH3)] (14). A solution of 2 (0.40
g, 0.53 mmol) in 30 mL of CHCl3/H2O (1:1 v/v) was saturated
with gaseous ammonia at 0 °C (ice bath) with vigorous stirring.
The resulting biphasic system was stirred overnight in the
dark at room temperature. The organic layer was separated,
dried over Na2SO4, and concentrated to ca. 5 mL under
vacuum. Addition of light petroleum ether (10 mL) gave the
complex fac-[(PNP)RuCl(CtCPh)(NH3)] (14), which was re-
crystallized from CH2Cl2/n-hexane solution. Yield: 71%.
After evaporation of the water phase under reduced pres-
sure, off-white microcrystals of NH4Cl were obtained in
quantitative yield.
Alternatively, 14 was prepared by reacting a solution of 2
(0.40 g, 0.53 mmol) in 20 mL of CHCl3 with a small excess of
diluted ammonium hydroxide (20 µL, NH3 30% in water).
Workup as described above gave 14 in 85% yield.
Anal. Calcd for C39H43N2ClP2Ru: C, 63.46; H, 5.87; N, 3.79.
Found: C, 63.16; H, 5.79; N, 3.24. IR: ν(NH) 3394 (w), ν(Ct
C) 2054 cm-1 (vs). 31P{1H} NMR (22 °C, CDCl3, 121.42 MHz):
2
1
AB system, δA 59.48, δB 57.53, J (PAPB) ) 35.4 Hz. H NMR
(22 °C, CDCl3, 299.94 MHz): δNH 1.89 (br s, 3H).
3
Rea ction of th e Am in o-Alk yn yl Com p lexes 11-14
w ith HCl. A stoichiometric amount of gaseous HCl (1.3 mL,
0.06 mmol) was syringed into a 5 mm NMR tube containing a
CD2Cl2 (1.0 mL) solution of the amino-alkynyl complexes 11-
14. 31P{1H} and 1H NMR analysis at room temperature showed
the transformation of the alkynyl complexes 11-14 into the
corresponding amminocarbenes 3, 5, 7, and 9 in quantitative
yield (based on 31P{1H} NMR integration).
R ea ct ion of t h e Am in o-Alk yn yl Com p lex 11 w it h
[NH3(CH2CH2CH3)]Cl. A THF solution (15 mL) of 11 (0.20
g, 0.26 mmol) was reacted with a small excess (30 mg, 0.31
mmol) of n-propylammonium chloride with stirring. Stirring
was continued for 30 min. Addition of n-heptane (10 mL) and
slow concentration under nitrogen gave yellow crystals of 3.
Yield: 85%.
fa c,cis-[(P NP )Ru Cl2(CtNCH2CH2CH3)] (16). Anal. Calcd
for C35H42N2Cl2P2Ru: C, 58.01; H, 5.84; N, 3.87. Found: C,
57.88; H, 5.76; N, 3.62. IR: ν(CtN) 2117 cm-1 (vs). 31P{1H}
1
NMR (20 °C, CDCl3, 121.42 MHz): 59.23 (s). H NMR (20 °C,
CDCl3, 200.13 MHz): δNCH
3 4.07 (t, 3J (HH) ) 6.6 Hz, 2H),
CH CH
2
2
δNCH
2.01 (sex, 3J (HH) ) 7.1 Hz, 2H), δNCH
1.24
CH CH
3
CH CH
2
2
3
2
2
(t, J (HH) ) 7.3 Hz, 3H). 13C{1H} NMR (20 °C, CD2Cl2, 75.42
3
2
MHz): δCtN 159.2 (t, J (CP) ) 15.6 Hz), δNCH
δNCH
52.1 (s),
CH CH
3
2
2
24.5 (s), δNCH
12.1 (s).
CH CH
3
CH CH
2
2
3
2
2
fa c,cis-[(P NP )R u Cl2(CtNP h )] (17). Anal. Calcd for
C38H40N2Cl2P2Ru: C, 60.16; H, 5.31; N, 3.69. Found: C, 59.98;
H, 5.25; N, 3.48. IR: ν(CtN) 2062 cm-1 (vs). 31P{1H} NMR
(20 °C, CD2Cl2, 121.42 MHz): δ 57.74 (s). 13C{1H} NMR (20
2
°C, CD2Cl2, 75.42 MHz): δCtN 171.4 (t, J (CP) ) 16.9 Hz).
In situ NMR experiments showed that the amino-alkynyls
12-14 react with 1 equiv of the appropriate alkylammonium
salt to give the corresponding aminocarbene in excellent yield
(g95%, based on 31P{1H} NMR integration).
fa c,cis-[(P NP )Ru Cl2{CtN(cyclo-C6H11)}] (18). Anal. Cal-
cd for C38H46N2Cl2P2Ru: C, 59.68; H, 6.06; N, 3.66. Found: C,
59.59; H, 6.10; N, 3.49. IR: ν(CtN) 2108 cm-1 (vs). 31P{1H}
NMR (22 °C, CD2Cl2, 81.01 MHz): δ 58.45 (s). 13C{1H} NMR
(20 °C, CD2Cl2, 75.42 MHz): δCtN 158.9 (t, 2J (CP) ) 15.9 Hz).
(R)-(+)-fa c,cis-[(P NP )Ru Cl2{CtNCH(Me)P h }] (19). Anal.
Calcd for C40H44N2Cl2P2Ru: C, 61.07; H, 5.64; N, 3.56.
Found: C, 60.94; H, 5.70; N, 3.48. IR: ν(CtN) 2100 cm-1 (vs).
31P{1H} NMR (22 °C, CDCl3, 81.01 MHz): AB system, δA 58.02,
δB 57.76, 2J (PAPB) ) 26.1 Hz. 1H NMR (20 °C, THF-d8, 200.13
MHz): δCHMe 5.6 (q, 3J (HH) ) 6.5 Hz, 1H), δCHMe 2.08 (d,
3J (HH) ) 6.8 Hz, 3H). 13C{1H} NMR (20 °C, CD2Cl2, 75.42
Cr ossin g Exp er im en ts. (A) Rea ction of fa c-[(P NP )-
Ru Cl(CtCP h )(NH2CH3CH2CH2)] (11) w ith [NH3(cyclo-
C6H11)]Cl. NMR Exp er im en t. A 5 mm NMR tube was
charged under nitrogen with 11 (20 mg, 0.026 mmol), [NH3-
(cyclo-C6H11)]Cl (4.0 mg, 0.029 mmol), and THF-d8 (0.8 mL).
The tube was shaken for 30 s and then placed into an NMR
probe. 31P{1H} NMR monitoring of the reaction showed the
fast conversion of 11 into a 9:1 mixture of the aminocarbenes
3 and 5. The composition of the reaction mixture did not
change over a period of 2 days at room temperature.
2
MHz): δCtN 160.9 (t, J (CP) ) 15.2 Hz), δCHMe 57.9 (s), δCHMe
25
25.9 (s). [R]D ) +11.50 (c ) 1.4, CHCl3).
P r ep a r a tive Exp er im en t. A THF (15 mL) solution of 11
(0.20 g, 0.26 mmol) was stirred in the presence of 1.1 equiv of
[NH3(cyclo-C6H11)]Cl (40 mg, 0.29 mmol) for 2 h. The addition
of n-heptane (10 mL), followed by concentration under a
stream of nitrogen, gave yellow crystals of 3 (yield 80%)
occasionally contaminated by trace amounts of 5. GC-MS
analysis of the solution showed the presence of about 1 equiv
of cyclohexylamine.
(R)-(-)-fa c,cis-[(P NP )Ru Cl2{CtNCH(Me)Et}] (20). Anal.
Calcd for
C36H44N2Cl2P2Ru: C, 58.54; H, 6.00; N, 3.79.
Found: C, 58.36; H, 5.99; N, 3.71. IR: ν(CtN) 2085 cm-1 (vs).
31P{1H} NMR (22 °C, CD2Cl2, 81.01 MHz): AB system, δA
2
1
59.31, δB 59.20, J (PAPB) ) 26.3 Hz. H NMR (20 °C, THF-d8,
200.13 MHz): δCH(Me)Et 4.30 (sextet, 3J (HH) ) 6.4 Hz, 1H),
δCH(Me)CH 3 1.98, 1.89 (ABXY3 spin system, 2J (HH) ) 14.2 Hz,
CH
2
3J (HAHX) ) 7.3, 3J (HBHX)) 5.5, 3J (HAHY) ) 7.5, 3J (HBHY) )

2380 Organometallics, Vol. 18, No. 12, 1999
Bianchini et al.
7.3 Hz, 2H), δCH(Me)Et 1.64 (d, 3J (HH) ) 6.2 Hz, 3H). δCH(Me)CH
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta for 8
CH
2
3
1.24 (t, J (HH) ) 7.1 Hz, 3H). 13C{1H} NMR (22 °C, CD2Cl2,
3
formula
mol wt
cryst size, mm
cryst syst
space group
a, Å
C51H54Cl2N2P2Ru
928.94
50.32 MHz): δCtN 159.2 (t, 2J (CP) ) 15.5 Hz), δCH(Me)Et 56.2
(s), δCH(Me)CH
[R]D ) -5.93 (c ) 1.2, CHCl3).
31.7 (s), δCH(Me)Et 22.6 (s), δCH(Me)CH 3 12.4 (s).
CH
CH
2
0.37 × 0.37 × 0.30
2
3
25
orthorhombic
P21P21P21 (No. 19)
13.551(4)
Syn th esis of (S)-(-)-fa c,cis-[(P NP )Ru Cl2{CtNCH(Me)-
(1-n a p h th yl)}] (21). When the (1-naphthyl)aminocarbene
complex 8 was refluxed as described above, only partial
conversion (e15%) to the corresponding isonitrile derivative
(S)-(-)-fac,cis-[(PNP)RuCl2{CtNCH(Me)(1-naphthyl)}] (21) was
obtained. Complete conversion of 8 to the isonitrile complex
21 was obtained when the thermal reaction was carried out
in refluxing monoglyme/H2O (20:1,v/v; bp ) 124 °C) for 14 h.
Yield: 88%. Anal. Calcd for C44H46N2Cl2P2Ru: C, 63.16; H,
5.54; N, 3.35. Found: C, 63.01; H, 5.38; N, 3.28. IR: ν(CtN)
2088 cm-1 (vs). 31P{1H} NMR (22 °C, CD2Cl2, 81.01 MHz): AB
b, Å
14.115(3)
c, Å
27.662(6)
5290.98
V, Å3
Z
d
4
1.17
4.82
calcd, g cm-3
µ(Mo KR), cm-1
radiation
graphite-monochromated Mo KR,
λ ) 0.710 69 Å
ω-2θ
scan type
2θ range, deg
scan width, deg
scan speed, deg min-1
total no. of data
5-46
0.9 + 0.34 tan θ
5.49
4131
2
1
system, δA 58.19, δB 58.04, J (PAPB) ) 26.2 Hz. H NMR (22
3
°C, CD2Cl2, 200.13 MHz): δCH(Me)Nap 6.26 (q, J (HH) ) 6.8 Hz,
1H), δCH(Me)Nap 2.16 (d, 3J (HH) ) 6.8 Hz, 3H). 13C{1H} NMR
no. of unique data, I > 3σ(I) 2573
(20 °C, CD2Cl2, 50.32 MHz): δCtN 162.1 (t, 2J (CP) ) 15.9 Hz),
no. of params
212
25
δCH(Me)Nap 54.5 (s), δCH(Me)Np 24.7 (s). [R]D ) +12.6 (c ) 0.9,
R
Rw
0.078
0.081
CHCl3).
On e-P ot Syn th esis of th e Ison itr ile Com p lexes 16-20.
A 3-fold excess of phenylacetylene was pipetted into a stirred
slurry of 1 (0.23 g, 0.25 mmol) in THF (40 mL). The mixture
was slowly brought to reflux temperature, and heating was
continued for 30-45 min. Three equivalents of the appropriate
primary amine NH2R (R ) CH3CH2CH2, cyclo-C6H11, (R)-(+)-
CH(Me)Ph, (R)-(-)-CH(Me)Et) was then syringed into the hot
red solution, which immediately became light yellow. The clear
yellow solution was refluxed overnight to afford, after the usual
workup, pure samples of the isonitrile complexes 16-20.
Yield: g85%.
complex fac-[(PNP)RuCl{CdNPh(CH2Ph}(CO)] (23) was fil-
tered off. Yield: 73%. Anal. Calcd for C46H47N2ClOP2Ru: C,
65.59; H, 5.62; N, 3.33. Found: C, 65.43; H, 5.61; N, 3.12. IR:
ν(CtO) 1920 (vs), ν(CdN) 1643 cm-1 (m). 31P{1H} NMR (-25
°C, CD2Cl2 saturated with CO, 121.42 MHz): AB spin system,
2
1
δ
A 66.98, δB 30.01, J (PAPB) ) 8.7 Hz. H NMR (-25 °C, CD2-
Cl2 saturated with CO, 299.94 MHz): δCH ABX spin system
Ph
2
(X ) 31P), δA 4.71, δB 4.12, J (HAHB) ) 13.0 Hz, J (HBX) ) 4.4
2
4
Hz, 2H). 13C{1H} NMR (-25 °C, CD2Cl2 saturated with CO,
2
50.32 MHz): δCdN 208.0 [dd, J (CPcis) ) 15.8, 10.7 Hz], δCtO
215.0 (dd, 2J (CPtrans) ) 101.0 Hz, 2J (CPcis) ) 8.9 Hz), δCH
When 1 was replaced by the vinylidene complex 2 in the
above reaction, the corresponding isonitrile complexes were
obtained in similar yields.
Ph
2
52.7 (s).
Rea ction of fa c,cis-[(P NP )Ru Cl2{C(NH2)(CH2P h )}] (9)
w ith n Bu Li in th e P r esen ce of CO: Syn th esis of fa c-
[(P NP )Ru Cl{CdNH(CH2P h )}(CO)] (24). A double propor-
tion of nBuLi (0.49 mL, 0.78 mmol, 1.6 M solution in THF)
was added dropwise to a stirred THF solution (20 mL) of 9
(0.300 g, 0.39 mmol) saturated with carbon monoxide and
cooled to -78 °C. The temperature was slowly raised to -10
°C, during which time the yellow color of the starting solution
faded. After 1 h, cold n-hexane purged with CO (25 mL) was
added until cream-colored crystals of the iminoacyl-carbonyl
complex fac-[(PNP)RuCl{CdNH(CH2Ph)}(CO)] (24) precipi-
tated. Yield: 80%. Anal. Calcd for C40H43N2ClOP2Ru: C, 62.70;
H, 5.66; N, 3.66. Found: C, 62.42; H, 5.66; N, 3.39. IR: ν(Ct
O) 1916 (vs), ν(CdN) 1638 cm-1 (m). 31P{1H} NMR (20 °C,
THF-d8 saturated with CO, 81.01 MHz): AB spin system, δA
62.43, δB 31.06, 2J (PAPB) ) 9.0 Hz. 1H NMR (20 °C, THF-d8
Rea ction of fa c,cis-[(P NP )Ru Cl2{C(N(H)P h )(CH2P h )}]
w ith n Bu Li: Syn th esis of m er ,tr a n s-[(P NP )Ru Cl(CH2P h )-
(CtNP h )] (22). To a THF (25 mL) solution of 4 (0.250 mg,
0.29 mmol) cooled to 0 °C was added a stoichiometric amount
of nBuLi (0.19 mL, 0.30 mmol, 1.6 M solution in THF) dropwise
with stirring. Stirring was continued for 30 min while the
solution was warmed to room temperature. Addition of ethanol
(20 mL) and slow concentration under nitrogen gave pale
yellow crystals of mer,trans-[(PNP)RuCl(CH2Ph)(CtNPh)] (22)
in 86% yield. Following this procedure, 22 was similarly
n
prepared from 4 by using NaOH instead of BuLi.
The crude product was recrystallized from CH2Cl2/ethanol
(1:1). Anal. Calcd for C45H47N2ClP2Ru: C, 66.37; H, 5.82; N,
3.44. Found: C, 66.17; H, 5.91; N, 3.40. IR: ν(CtN) 2050 cm-1
(vs). 31P{1H} NMR (20 °C, CD2Cl2, 81.01 MHz): δ 31.69 (s).
2
1H NMR (20 °C, CD2Cl2, 200.13 MHz): δCH
3.11 (t, J (CP)
4
saturated with CO, 200.13 MHz): δNH 9.09 (d, J (HP) ) 27.3
Ph
2
) 4.4 Hz, 2H). 13C{1H} NMR (20 °C, CD2Cl2, 50.32 MHz): δCt
160.8 (t, J (CP) ) 2.9 Hz), δCH 10.31 (t, J (CP) ) 6.5 Hz).
2
Hz, 1H); δCH
AB spin system, δA 5.00, δB 3.53, J (HAHB) )
Ph
2
2
2
16.4 Hz, 2H.
N
Ph
2
Rea ction of m er ,tr a n s-[(P NP )Ru Cl(CH2P h )(CtNP h )]
X-r a y Diffr a ction Stu d y of fa c,cis-[(P NP )Ru Cl2{C{NH2-
(1-n a p h th yl)}(CH2P h )}] (8). Canary yellow crystals (0.25 ×
0.20 × 0.12 mm) suitable for an X-ray diffraction analysis were
grown in the air by slow evaporation from a diluted dichloro-
methane/n-hexane solution of 8. A summary of crystal and
intensity data for the compound is presented in Table 1.
Experimental data were recorded at room temperature on a
ENRAF-Nonius CAD4 diffractometer using graphite-mono-
chromated Mo KR radiation. A set of 25 carefully centered
reflections in the range 5.5° e θ e 7° was used for determining
the lattice constants. As a general procedure, the intensities
of three standard reflections were measured periodically every
2 h for orientation and intensity control. This procedure
revealed a minimum decay (5%) of intensities. The data were
corrected for Lorentz and polarization effects. Atomic scatter-
ing factors were those tabulated by Cromer and Waber,25 with
anomalous dispersion corrections taken from ref 26. An
w ith HCl. A slight excess of HCl (1 M solution in H2O) was
added via syringe into a 5 mm screw cap NMR tube containing
a THF-d8 (0.8 mL) solution of 22 (30 mg, 0.037 mmol) cooled
to -40 °C. 31P{1H} NMR spectroscopy showed the quantitative
transformation of 22 into 17. GC-MS analysis of the solution
confirmed the formation of 1 equiv of toluene.
Rea ction of fa c,cis-[(P NP )Ru Cl2{C(N(H)P h )(CH2P h )}]
(4) w ith n Bu Li in th e P r esen ce of CO: Syn th esis of fa c-
[(P NP )Ru Cl{CdNP h (CH2P h }(CO)] (23). A double propor-
tion of nBuLi (0.37 mL, 0.59 mmol, 1.6 M solution in THF)
was added dropwise to a stirred THF solution (20 mL) of 4
(0.250 g, 0.29 mmol) saturated with carbon monoxide and
cooled to -78 °C. The temperature was slowly raised to -18
°C, during which time the yellow color of the starting solution
faded. After 2 h, cold n-hexane purged with CO (25 mL) was
added and the off-white precipitate of the iminoacyl-carbonyl

Aminocarbene Complexes in Ru-Assisted Aminolysis
Organometallics, Vol. 18, No. 12, 1999 2381
Sch em e 2
empirical absorption correction was applied using the program
DIFABS27 with transmission factors in the range 0.77-1.41.
The computational work was performed with a Pentium-II
personal computer using the program SHELX76.28 The pro-
grams PARST29 and ORTEP30 were also used. Final atomic
coordinates with equivalent isotropic thermal parameters of
all atoms and structure factors are available as Supporting
Information.
The structure was solved via direct methods using the SIR92
program,31 and all the non hydrogen atoms were found through
a series of Fo Fourier maps. Refinement was done by full-
matrix least-squares calculations, initially with isotropic
thermal parameters and then, in the last least-squares cycle,
with anisotropic thermal parameters for the ruthenium,
chlorine, and phosphorus atoms. All of the phenyl rings were
treated as rigid bodies with D6h symmetry and C-C distances
fixed at 1.39 Å. Hydrogen atoms were introduced in calculated
positions but not refined. Constraint distances were used for
the naphthyl substituent. No significant peaks were detected
in the final least-squares cycles.
Compounds 3-9 are canary yellow crystalline solids
with good solubility in polar organic solvents and
excellent stability to moisture and oxygen. Their un-
equivocal characterization was achieved by means of
standard spectroscopic techniques as well as elemental
analyses, which were all consistent with the incorpora-
tion of one molecule of amine into the complex frame-
work. Selected NMR and IR data are given in the
Experimental Section. Briefly, all the IR spectra contain
a broad and weak absorption in the N-H stretching
region (3466-3440 cm-1), while the primary aminocar-
bene 9 shows two bands at slightly lower wavenumbers
(3383, 3276 cm-1).
Indicative of a facial arrangement of the PNP ligand,
the 31P{1H} NMR spectra in CDCl3 show singlet reso-
nances from 53.36 to 48.03 ppm.2,24,33,34 The 31P NMR
signals do not vary with the temperature from +20 to
-110 °C (in a CDCl3/CD2Cl2 mixture), which indicates
a rapid rotation of the carbene ligand around the Ru-C
axis irrespective of the bulkiness of the N-substituent.
The existence of a low-energy rotational barrier about
the Ru-C bond in carbene and vinylidene derivatives
has several precedents and is consistent with a sub-
stantial degree of Ru-C single bond.35 As a conse-
quence, structures containing a C-N double bond
should significantly contribute to the description of the
aminocarbenes 3-9. Indeed, the different chemical
shifts exhibited by the hydrogens of the NH2 group in 9
support this hypothesis. Due to the presence of a chiral
substituent on the aminocarbene ligand, the 31P{1H}
NMR spectra of 6-8 show slightly perturbed second-
order AB splitting patterns with homonuclear geminal
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of th e Am in o-
ca r ben e Com p lexes. Treatment of the vinylidene
complex fac,cis-[(PNP)RuCl2{CdC(H)Ph}] in THF with
a 3-fold excess of a primary amine yields neutral
aminocarbene complexes of the general formula
fac,cis-[(PNP)RuCl2{C(NHR)(CH2Ph)}] (R ) CH3CH2-
CH2 (3), Ph (4), cyclo-C6H11 (5), (R)-(+)-CH(Me)(Ph) (6),
(R)-(-)-CH(Me)(Et) (7), (S)-(-)-CH(Me)(1-naphthyl) (8))
(Scheme 2). All the reactions are generally fast even at
room temperature, as shown by an immediate color
change from orange to light yellow. Only with the least
basic amine, aniline (pKa ) 4.63),32 does the reaction
require 3 h to be complete.
2
coupling constants J PP equal to ca. ∼29 Hz. In the
chiral aminocarbenes 6-8, the hydrogen atoms of the
The primary aminocarbene complex fac,cis-[(PNP)-
RuCl2{C(NH2)(CH2Ph)}] (9) is prepared by stirring a
CHCl3 solution of 2 for 30 min under a NH3 atmosphere,
followed by overnight reflux under nitrogen.
benzyl substituent are diastereotopic and thus give rise
1
to an AB multiplet in the H NMR spectra. In contrast,
the achiral derivatives 3-5 and 9 show only a singlet
resonance for the benzylic protons. Irrespective of the
presence of a chiral N-substituent, the NH proton
appears as either a broad hump or a broad doublet (3J HH
≈ 9 Hz) (δNH 12.35-10.62) due to coupling to the
quadrupolar nitrogen nucleus (I(14N) ) 1).36 The NH2-
(25) Cromer, D. T.; Waber, J . T. Acta Crystallogr. 1965, 18, 104.
(26) International Tables of Crystallography; Kynoch: Birmingham,
U.K., 1974; Vol. 4.
(27) Walker, N.; Stuart, D. Acta Crystallogr. 1983, 39A, 158.
(28) Sheldrick, G. M. SHELX-76 Program for Crystal Structure
Determination; University of Cambridge: Cambridge, U.K., 1976.
(29) Nardelli, M. Comput. Chem. 1983, 7, 95.
(30) J ohnson, C. K. ORTEP; Report ORNL-5138; Oak Ridge Na-
tional Laboratory: Oak Ridge, TN, 1976.
(31) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27, 435.
(32) Gordon, A. J .; Ford, R. A. The Chemist’s Companion; Wiley-
Interscience: New York, 1972; p 59.
(33) Pregosin, P. S.; Kunz, R. W. In 31P and 13C NMR of Transition
Metal Phosphine Complexes; Diehl, P., Fluck, E., Konsfeld, R., Eds.;
Springer-Verlag: Berlin, Heidelberg, New York, 1979.
(34) Meek, D. W.; Mazanec, T. Acc. Chem. Res. 1981, 14, 266.
(35) Kostic, N. M.; Fenske, R. F. Organometallics 1982, 1, 974.
(36) Gunnoe, T. B.; White, P. S.; Templeton, J . L. J . Am. Chem. Soc.
1996, 118, 6916.

2382 Organometallics, Vol. 18, No. 12, 1999
Bianchini et al.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 8
Ru-P1
Ru-P2
Ru-Cl1
Ru-Cl2
Ru-N1
2.285(5)
2.292(6)
2.472(5)
2.478(5)
2.37(2)
Ru-C8
N2-C8
N2-C10
C8-C9
1.99(2)
1.32(2)
1.46(2)
1.51(2)
Cl1-Ru-Cl2
P1-Ru-P2
P1-Ru-Cl1
P1-Ru-C12
P2-Ru-C11
P2-Ru-C12
P1-Ru-C8
P2-Ru-C8
P1-Ru-N1
83.4(2)
99.6(2)
83.5(2)
163.7(2)
171.4(2)
92.1(2)
99.2(5)
97.6(5)
83.1(4)
P2-Ru-N1
Cl1-Ru-N1
Cl2-Ru-N1
Cl1-Ru-C8
Cl2-Ru-C8
Ru-C8-N2
Ru-C8-C9
N2-C8-C9
83.3(4)
89.2(4)
87.1(4)
89.9(5)
90.4(5)
117(1)
127(1)
116(1)
The two chloride ligands are cis to each other and trans
to the two phosphorus atoms of the PNP ligand. The
carbene ligand is located trans to the nitrogen atom.
The principal geometrical features of 8 are in line
with those found for other ruthenium(II)-PNP com-
plexes.22-24,41 The most evident distortion from the
idealized geometry is the bending of the PPh2 wings
toward the N(1) atom (P(1)-Ru-N(1) ) 83.1(4)°; P(2)-
Ru-N(1) ) 83.3(4)°) and toward the two chlorine atoms
(P(1)-Ru-P(2) ) 99.6(2)°). A similar distortion was
observed in fac,cis-[(PNP)RuCl2(CO)].24 In keeping with
the smaller trans influence of the aminocarbene vs CO,
the Ru-N(1) separation (2.37(2) Å) is larger than that
found in the CO complex (2.310(8) Å).24
The bond lengths and angles pertaining to the amino-
carbene ligand are typical for Fischer-type carbene
complexes38 and quite similar to those found in CpRuI-
(CO){C(NHMe)P}, which was the only Ru(II) aminocar-
bene complex to have been authenticated by X-ray
methods.40 The angles around the carbene carbon C(8)
are 117(1)° (Ru-C(8)-N(2)), 127(1)° (Ru-C(8)-C9)),
and 116(1)° (N(2)-C(8)-C(9)), which sum up to 360°,
reflecting the sp2 hybridization at the carbon C(8). The
naphthyl substituent on the carbon stereocenter lies in
the plane that bisects the two chlorine atoms. The
coordination plane of the carbene ligand (Ru-C(8)-
C(9)-N(2), rms deviation 0.0095) is twisted by ca. 41°
from the plane N(1)-Cl(2)-C(8)-P(1)-Ru (rms devia-
tion 0.0292). This deformation, which reflects the pres-
ence of a bulky group, has already been observed in
Fischer-type carbenes bearing sterically demanding
substituents.38
F igu r e 1. ORTEP drawing of complex 8. For the sake of
clarity the phenyl rings in the PNP ligand have been
omitted.
carbene 9 exhibits two slightly downfield shifted reso-
nances (δNH 10.14 and 8.34).37
2
The 13C{1H} NMR spectra of 3-9 confirm the pres-
ence of a carbene ligand trans to the nitrogen donor
atom. The carbene carbons appear as triplets with
chemical shifts (δRudC 265-251) and coupling constants
in the expected range for ruthenium(II) Fischer-type
carbenes (2J CP ≈ 11 Hz).2,37,38 All the proton and carbon
resonances of the aminocarbene complexes were unam-
biguously assigned by means of HMQC (1H,13C-hetero-
correlated 2D-NMR spectra), 1H,1H-2D COSY NMR,
and 13C{1H} DEPT-135 NMR experiments.
With the exception of piperidine, which gives fac,cis-
[(PNP)RuCl2{C(NC5H10)(CH2Ph)}] (10), secondary and
tertiary amines do not form aminocarbene products by
reaction with 2. Since piperidine is indeed the least
sterically demanding secondary amine,39 it is reasonable
to conclude that the formation of the aminocarbene
group is also controlled by steric effects (vide infra). The
chemical and physical properties of the tertiary amino-
carbene complex 10 do not differ from those of the
germane compounds bearing NHR or NH2 substituents
on the carbene carbon and thus do not deserve any
additional comment.
Cr ysta l Str u ctu r e of fa c,cis-[(P NP )Ru Cl2{C(NH-
(S)-(-)-CH(Me)(1-n a p h th yl))(CH2P h )}] (8). To con-
firm the stereochemistry of the present aminocarbene
complexes and to collect further geometrical information
on this class of compounds, an X-ray analysis was
carried out on a single crystal of the chiral complex 8.
An ORTEP drawing of the complex is shown in Figure
1 with the atomic numbering scheme. A list of selected
bond distances and angles is given in Table 2.
Mech a n istic Stu d ies of th e Hyd r oa m in a tion of
th e Vin ylid en e Liga n d . Monitoring the reaction be-
tween 2 and primary amines by 31P{1H} NMR spectros-
copy provides evidence of a new mechanism for the
hydroamination of metal vinylidenes by primary amines.
The formation of the PNP aminocarbene complexes
indeed requires 2 equiv of amine to occur and involves
a mechanism in which one molecole of amine deproto-
nates the vinylidene Câ carbon atom, while a second
molecule coordinates the metal center prior to be
transferred onto the CR carbon atom of a σ-alkynyl
intermediate (Scheme 3).
The coordination geometry of the ruthenium atom
may be described as a slightly distorted octahedron with
the aminodiphosphine ligand occupying three facial
coordination sites. Two chloride ligands and one amino-
carbene group complete the coordination polyhedron.
(37) Gamasa, M. P.; Gimeno, J .; Mart´ın-Vaca, B.; Borge, J .; Garc´ıa-
Granda, S.; Perez-Carren˜o, E. Organometallics 1994, 13, 4045.
(38) Do¨tz, K. H.; Fischer, H.; Hoffmann, P.; Kreissl, F. R.; Schubert,
U.; Weiss, K. Transition Metal Carbene Complexes; Verlag-Chemie:
Weinheim, Germany, 1983.
(39) House, D. A. In Comprehensive Coordination Chemistry; Wilkin-
son, G., Gillard, R. D., McCleverty, J . A., Eds.; Pergamon Press:
Oxford, U.K., 1987; Vol. 2, Chapter 13.1.
Experimental evidence of this mechanism was pro-
vided by an in situ NMR study carried out as follows.
(40) Adams, H.; Bailey, N. A.; Ridgway, C.; Taylor, B. F.; Walters,
S. J .; Winter, M. J . J . Organomet. Chem. 1990, 394, 349.
(41) Bianchini, C.; Masi, D.; Peruzzini, M.; Romerosa, A.; Zanobini,
F. Acta Crystallogr. 1996, C52, 1973.

Aminocarbene Complexes in Ru-Assisted Aminolysis
Organometallics, Vol. 18, No. 12, 1999 2383
Sch em e 3
basis of this simple experiment, one may readily con-
clude that the formation of the aminocarbene complexes
3-9 involves a preliminary acid/base reaction between
the first equivalent of amine and the vinylidene 2
(formal dehydroalogenation reaction)45 to give five-
coordinate phenylethynyl Ru(II) complexes and alkyl-
ammonium chlorides. At this point, the second equiva-
lent of amine can occupy the vacant coordination site
and ultimately generate the octahedral (phenylethynyl)-
primary amine derivatives 11-14. These complexes are
stable in solution and can be isolated in the solid state
provided that alkylammonium chloride is removed from
the reaction medium. In fact, if not removed, the NH3R+
cations quickly reprotonate the alkynyl ligand. As a
result, transient cis-amine-vinylidene complexes are
formed which spontaneously degrade to the thermody-
namically stable aminocarbene products via intramo-
lecular attack by the amine onto the electrophilic CR
carbon atom of the vinylidene group. No amine-
vinylidene intermediate was seen by NMR spectroscopy,
however.
One equivalent of propylamine was syringed into an
NMR tube containing a CD2Cl2 solution of 2 at 20 °C.
A 31P NMR spectrum was immediately acquired, show-
ing the vinylidene resonance at 47.9 ppm to have almost
disappeared with formation of a new AB spin system
2
centered at 58.0 ppm (δA 58.89, δB 57.13, J (PAPB) )
34.9 Hz). The addition of a second equivalent of amine
completed the transformation of 2 into this new product
and also led to the formation of a very small amount of
the aminocarbene 3 (singlet at 51.31 ppm). With time
this latter complex became the only PNP complex in
solution.
The occurrence of an intramolecular amine-migration
step has been proved by means of several cross experi-
ments. As an example, an isolated sample of the
phenylethynyl-n-propylamine complex 11 was treated
in an NMR tube with cyclohexylammonium chloride.
After the tube was shaken for a few seconds, a 31P NMR
spectrum showed that the aminocarbene 3 was quickly
and selectively formed. Vice versa, when n-propyl-
ammonium chloride was added to a solution of 12, the
aminocarbene 5 was selectively obtained. Analogous
experiments with various combinations of phenyl-
ethynyl-amine complexes and alkylammonium chlo-
rides confirmed that the nucleophilic attack at the
vinylidene CR atom is selectively brought about by the
coordinated amine.46
In keeping with the overall mechanistic picture given
in Scheme 3, the addition of gaseous HCl (ca. 1 equiv)
to a CD2Cl2 solution of any phenylethynyl-amine
complexes led to the quantitative formation of the
corresponding aminocarbene. The protonation of the
alkynyl ligand in 11-14 is thus a mandatory step to
generate the vinylidene group susceptible to attack by
the cis amine ligand. The occurrence of an intramolecu-
lar nucleophilic attack by the coordinated amine also
accounts for the fact that only nonsterically demanding
amines with good coordinating ability such as NH3,
primary amines, and piperidine react with 2, yielding
aminocarbene complexes. Secondary and tertiary amines
do not coordinate the ruthenium center, although they
are still able to deprotonate the vinylidene ligand in 2
to σ-alkynyl. From this reaction, however, no product
was isolated unless CO was added. In this case, the
known phenylethynyl-carbonyl complex fac-[(PNP)-
RuCl(CtCPh)(CO)] (15) was quantitatively formed.24
Tr a n sfor m a tion of th e Am in oca r ben e Liga n d s
in to Ison itr ile Liga n d s a n d Tolu en e. The aminocar-
bene complexes 3-7 transform into the corresponding
isonitrile derivatives fac,cis-[(PNP)RuCl2(CtNR)] (R )
On the basis of the in situ NMR evidence, the
intermediate product with the AB pattern was isolated
by simply scaling up the spectroscopic experiment and
identified as the complex fac-[(PNP)RuCl(CtCPh)(NH2-
CH3CH2CH2)] (11), containing cis phenylethynyl and
propylamine ligands. The analogous derivatives fac-
[(PNP)RuCl(CtCPh)(NH2R)] (R ) cyclo-C6H11 (12), (R)-
(-)-CH(Me)Et (13), H (14)) were similarly synthesized.
A few examples of ruthenium amine-alkynyl complexes
have been reported,42 and the structure of [(NH3)Ru-
(CtCPh)(dppe)2]PF6 (dppe ) Ph2PCH2CH2PPh2) has
also been determined by an X-ray analysis.43 Salient
spectroscopic features of the PNP compounds 11-14 are
(i) a strong and sharp ν(CtCPh) absorption at ca. 2055
cm-1 in the IR spectrum,44 (ii) the chemical inequiva-
lence of the two PPh2 groups (31P NMR AB system)
originated by the substitution of one chloride ligand by
amine, and (iii) the appearance in the 1H NMR spectrum
of a broad resonance in the region of amine N-H
groups.18 The NH2R ligands in 11-14 are quite labile
and can readily be displaced by different σ- and π-donor
ligands. As an example, treatment of a CH2Cl2 solution
of any (phenylethynyl)amine complex with CO gives the
known phenylethynyl-carbonyl complex fac-[(PNP)-
RuCl(CtCPh)(CO)] in almost quantitative yield.24
Consistent with the release of 1 equiv of alkylammo-
nium chloride upon reaction of 2 with the first equiva-
lent of primary amine, the use of aqueous biphasic
media (H2O/CHCl3 or H2O/CH2Cl2; 1:1 v/v) was found
to greatly improve both the yield and purity of the
amine-alkynyl complexes 11-14. Once separated from
the organic phases containing the ruthenium products,
the aqueous phases were concentrated under vacuum
until the alkylammonium chlorides separated. On the
(42) (a) Touchard, D.; Haquette, P.; Guesmi, S.; Le Pichon, L.;
Daridor, A.; Toupet, L.; Dixneuf, P. H. Organometallics 1997, 16, 3640.
(b) Rappert, T.; Yamamoto, A. Organometallics 1994, 13, 4984. (c)
Nu¨rnberg, O.; Werner, H. J . Organomet. Chem. 1993, 460, 163. (d)
Touchard, D.; Guasmi, S.; Le Pichon, L.; Daridor, A.; Dixneuf, P. H.
Inorg. Chim. Acta 1998, 280, 118.
(43) Touchard, D.; Morice, C.; Cadierno, V.; Haquette, P.; Toupet,
L.; Dixneuf, P. H. J . Chem. Soc., Chem. Commun. 1994, 859.
(44) See for example: Bianchini, C.; Meli, A.; Peruzzini, M.; Vacca,
A.; Laschi, F.; Zanello, P.; Ottaviani, F. M. Organometallics 1990, 9,
360.
(45) (a) Heyn, R. H.; Caulton, K. G. J . Am. Chem. Soc. 1993, 115,
3354. (b) Slugovc, C.; Mauthner, K.; Kacetl, M.; Mereiter, K.; Schmid,
R.; Kirchner, K. Chem. Eur. J . 1998, 4, 2043.
(46) Τhe conversion of vinylidene to hydroxycarbene by intramo-
lecular attack of water through a similar mechanism has been proposed
for the reaction of 2 with water.2

2384 Organometallics, Vol. 18, No. 12, 1999
Bianchini et al.
Sch em e 4
Sch em e 5
CH3CH2CH2 (16), Ph (17), cyclo-C6H11 (18), (R)-(+)-CH-
(Me)Ph (19), (R)-(-)-CH(Me)Et (20)) upon overnight
reflux in THF/H2O mixtures (20:1 v/v). A medium with
a higher boiling point (monoglyme/H2O) was employed
to convert the aminocarbene complex 8 bearing the
bulky (S)-(-)-1-(1-naphthyl)ethyl substituent. Each ther-
molysis was accompanied by the quantitative formation
of free toluene and required the presence of some water
in the reaction medium to occur (Scheme 4). Indeed, in
truly anhydrous solvents, all the aminocarbene com-
plexes were stable even under prolonged reflux. In
contrast to this general behavior, both the primary
aminocarbene 9 and the tertiary aminocarbene 10 did
not convert to the isocyanide derivative even after
prolonged heating in wet THF, monoglyme, or DMSO.
The isonitrile complexes 16-20 were straightfor-
wardly authenticated by standard spectroscopic tech-
niques. Diagnostic features are a strong CtN band at
ca. 2100 cm-1 in the IR spectra and a triplet resonance
(2J CP ≈ 16 Hz) at ca. 160 ppm in the 13C{1H} NMR
spectra due to the CtN carbon atom. No coupling of
the latter nucleus to the 14N nucleus was observed.47
The phenylisonitrile complex 17 shows a slightly red-
shifted CN absorption (ν(CN) 2062 cm-1) and a slightly
deshielded CN resonance (δ 171.4), indicating a signifi-
cant π-electron delocalization over the N-bonded phenyl
ring.
Sch em e 6
The 31P{1H} NMR spectra contain signals in the
typical range for fac,cis-PNP metal complexes (ca. 59
ppm) and consist of either a singlet (16-18) or an AB
spin system (19-21) depending on the achiral or chiral
nature of the isonitrile substituent, respectively.
A one-pot synthesis of the isonitrile complexes 16-
21 has also been developed, starting from reagent grade
THF (or monoglyme for 21) containing the precursor
mer,trans-[(PNP)RuCl2(PPh3)] (1), phenylacetylene, and
a primary amine among those employed in this work
(Scheme 5). In light of the well-known reactivity of 1
with terminal alkynes,24 there is little doubt that 2 is
the first species to be formed via 1-alkyne to vinylidene
tautomerization.11,48 From the vinylidene intermediate,
each isonitrile derivative is then obtained following the
reaction sequence alkynyl-amine f aminocarbene f
isonitrile.
the formation of the isonitrile complexes fac,cis-[(PNP)-
RuCl2(CtNR)] from the aminocarbene precursors fac,-
cis-[(PNP)RuCl2{(NHR)(CH2Ph)}] is proposed in Scheme
6a. The mechanism involves three steps: thermal
elimination of HCl from the aminocarbene ligand to give
a coordinatively unsaturated iminoacyl derivative (A),
migration of the benzyl substituent from the iminoacyl
group to the metal (this step may be seen as phenyl-
isonitrile deinsertion) (B), and protonolysis of the
Ru(II)-alkyl bond by the previously generated HCl (C).
Through this final step, toluene is formed and the
octahedral geometry around the metal is restored by
chloride coordination. Traces of water in the reaction
media are most likely necessary to favor both the
deprotonation from the aminocarbene complexes and
the subsequent protonation of the alkynyl ligand in the
phenylethynyl-amine intermediates.
A quite similar mechanism has recently been reported
for the hydrolysis of the vinylidene complex 2 to give
fac,cis-[(PNP)RuCl2(CO)] and toluene (Scheme 6b).2 The
identification of the principal intermediates along the
hydrolysis pathway, in particular the acyl complex (A′)
and the benzyl-carbonyl species (B′), was achieved by
means of independent reactions with isolated com-
pounds. This same strategy has been employed to gain
Mech a n istic Stu d ies of th e Th er m olysis of th e
Am in oca r ben e Liga n d s. A mechanism accounting for
(47) Crociani, B.; Richards, R. L. J . Organomet. Chem. 1978, 144,
85.
(48) Key references on metal-assisted alkyne to vinylidene tau-
tomerization include: (a) Werner, H. Angew. Chem., Int. Ed. Engl.
1990, 29, 1077. (b) Bianchini, C.; Peruzzini, M.; Vacca, A.; Zanobini,
F. Organometallics 1991, 10, 463. (c) Fryzuk, M. D.; Huang, L.;
Mcmanus, N. T.; Paglia, P.; Rettig, S. J .; White, G. S. Organometallics
1992, 11, 2979. (d) Lumprey, J . R.; Selegue, J . P. J . Am. Chem. Soc.
1992, 114, 5518. (e) Bianchini, C. Marchi, A.; Marvelli, L.; Peruzzini,
M.; Romerosa, A.; Rossi, R.; Vacca, A. Organometallics 1995, 14, 3203.
(f) de los R´ıos, I.; J ime´nez Tenorio, M.; Puerta, M. C.; Valerga, P. J .
Am. Chem. Soc. 1997, 119, 6529.

Aminocarbene Complexes in Ru-Assisted Aminolysis
Organometallics, Vol. 18, No. 12, 1999 2385
ν(CdN) 1643 cm-1) but decomposes in solution in the
absence of a protective CO atmosphere. The solution
structure of 23 was thus determined at -25 °C by
multinuclear NMR spectroscopy in CD2Cl2 solution
saturated with CO. The presence of a fac-PNP ligand
in the complex is shown by a low-field AB 31P pattern
Sch em e 7
2
(δA 66.98, δB 30.01, J (PAPB) ) 8.7 Hz) with PB being
the phosphorus atom trans to CO.50 The 13C NMR
spectrum contains two doublets of doublets for both the
2
CO and CdN carbon nuclei (215.0 ppm, dd, J (CPtrans
)
) 101.0 Hz, 2J (CPcis) ) 8.9 Hz and 208.0 ppm, dd,
2J (CPcis) ) 15.8, 10.7 Hz, respectively). The chemical
shift of the iminoacyl carbon atom is strongly indicative
of an η1-iminoacyl ligand.51 The benzylic protons are
diastereotopic because of the chiral nature of the metal
center and give rise to a complex ABX pattern due to
coupling to each other and to one phosphorus atom.
mechanistic insight into the transformation of fac,cis-
[(PNP)RuCl2{C(NHPh)(CH2Ph)}] (4) into fac,cis-[(PNP)-
RuCl2(CNPh)] (17).
Quite similar spectroscopic characteristics are exhib-
ited by the iminoacyl-carbonyl complex fac-[(PNP)-
RuCl{CdNH(CH2Ph}(CO)] (24), obtained by reaction of
Monitoring the thermolysis of 4 by 31P{1H} and 1H
NMR spectroscopy in either THF-d8 or CDCl3 did not
show any intermediate along the transformation into
17, even at the lowest temperature at which the
degradation of the aminocarbene became visible (ca. 40
°C). The absence of detectable intermediates suggested
that the degradation of the iminoacyl complex and the
subsequent reaction of the benzyl-isonitrile derivative
with HCl are much faster than the elimination of HCl
from the aminocarbene (rate-determining step). In an
attempt to intercept the iminoacyl and/or benzyl-
isonitrile intermediates, the elimination of HCl from 4
was performed in the presence of reactants capable of
stabilizing either intermediate. In a first attempt, 4 in
THF was treated with nBuLi at 0 °C. As a result, the
benzyl-phenylisonitrile complex mer,trans-[(PNP)RuCl-
(CH2Ph)(CtNPh)] (22) was selectively obtained. This
latter compound indeed gave toluene and 17 upon
reaction with HCl even at very low temperature (-78
°C) (Scheme 7).
n
the primary aminocarbene 9 with BuLi in the presence
1
of CO. In the H NMR spectrum, the CdNH hydrogen
appears as a doublet at 9.09 ppm with 4J (HP) ) 27.3
Hz.
Besides incorporating all the experimental observ-
ables accumulated in the course of this study, the
mechanism outlined in Scheme 6a also accounts for the
thermal stability of the tertiary aminocarbene complex
10. In this compound, the carbene nitrogen atom does
not bear hydrogens and thus cannot be deprotonated
to generate the iminoacyl group. Less straightforward
is the explanation for the thermal stability of the
primary aminocarbene 9. Indeed, this complex contains
a CdNH group and thus might undergo the thermal
elimination of HCl to give the hydrogen isocyanide
complex fac,cis-[(PNP)RuCl2(CtNH)] via iminoacyl and
benzyl-hydrogen isocyanide intermediates. The fact
that this does not happen might be due to both kinetic
and thermodynamic factors. In particular, we suggest
that the inverse reaction of the iminoacyl intermediate
by HCl to regenerate 9 is faster than its degradation to
the benzyl-hydrogen isocyanide complex. As a matter
of fact, the iminoacyl-carbonyl complex 24 is quanti-
tatively produced from 9 when HCl is neutralized by
nBuLi in the presence of CO (Scheme 7). In the absence
of CO, butane and LiCl were still formed but no stable
ruthenium complex was obtained, most likely because
of the inherent instability of the CNH molecule.
n
When the reaction between 4 and BuLi was followed
by variable-temperature NMR spectroscopy in THF-d8,
no intermediate species was seen prior to the selective
formation of 22, indicating that the conversion of the
iminoacyl intermediate to the benzyl-isonitrile product
is a downhill process, faster than the NMR time scale.
In an attempt to intercept the iminoacyl complex, the
reaction between 4 and nBuLi was carried out at low
temperature (-78 °C) in the presence of a positive
pressure of CO. As result, the iminoacyl complex was
successfully intercepted and isolated as the CO adduct
fac-[(PNP)RuCl{CdNPh(CH2Ph}(CO)] (23).
Finally, it is worth mentioning that the thermolytic
degradation of aminocarbene ligands to isonitriles has
no precedent in the literature.52 To the best of our
knowledge, the only related process may be identified
in the transformation of the iron vinylidene complex
Both 22 and 23 have been characterized by analytical
and spectroscopic techniques. In particular, 22 was
readily authenticated by comparison with the known
complex mer,trans-[(PNP)RuCl(CH2Ph)(CO)].2 The pres-
ence of a phenylisonitrile ligand in 22 is shown by a
ν(CtN) band at 2050 cm-1 and by a triplet at 160.8 ppm
in the 13C NMR spectrum clearly due to the isonitrile
carbon atom. A triplet at 10.31 ppm was assigned to
the benzyl carbon on the basis of a DEPT-135 experi-
ment. It is worth mentioning that the fragmentation of
the aminocarbene group in 4 into benzyl and isonitrile
ligands is associated with the isomerization of the PNP
ligand from fac to mer.2,49 Unlike 22, the carbonyl
(49) Bianchini, C.; Farnetti, E.; Glendenning, L.; Graziani, M.;
Nardin, G.; Peruzzini, M.; Rocchini, E.; Zanobini, F. Organometallics
1995, 14, 1489.
(50) Bianchini, C.; Peruzzini, M.; Purches, G.; Zanobini, F. Inorg.
Chim. Acta 1998, 272, 1.
(51) (a) Conejo, M. d. M.; Pizzarro, A.; Sa´nchez, L. J .; Carmona, E.
J . Chem. Soc., Dalton Trans. 1996, 3687. (b) Stark, G. A.; Gladysz, J .
A. Inorg. Chem. 1996, 35, 5509. (c) Delis, J . G. P.; Aubel, P. G.; van
Leeuwen, P. W. N. M.; Vrieze, K.; Veldman, N.; Spek, A. L. J . Chem.
Soc., Chem. Commun. 1996, 2233.
(52) The addition of amine across alkyne triple bonds gives enamines
that, similarly to enols, tautomerize to the more stable imines. No
rearrangement of imine to nitrile or isonitriles has ever been reported,
however.
complex 23 is stable in the solid state (ν(CO) 1920 cm-1
,

2386 Organometallics, Vol. 18, No. 12, 1999
Bianchini et al.
[Cp(CO)(PPh3)FedCdCH2]BF4 into the acetonitrile de-
rivative [Cp(CO)(PPh3)FeNtCCH3]BF4 through the
condensation of the vinylidene ligand with hydrazines,
followed by an “organometallic” Beckmann-type rear-
rangement of a hydrazino-carbene intermediate.53
sents a drawback of the present procedure, as it
precludes any chance of catalytic production. Neverthe-
less, the method is clean and selective and also provides
access to very rare examples of chiral isonitrile ligands,
starting from commercially available, optically pure
amines.55
Con clu sion s
Ack n ow led gm en t. Thanks are due to the bilateral
project “Azione integrata” between the Universities of
Florence (Florence, Italy) and Almeria (Almeria, Spain)
for supporting the stay of A.R. in Florence and to the
EC (projects INTAS No. 96-1176 and INCO ERB
IC15CT960746) for financial support.
In conclusion, an unforeseen conversion of ruthenium
vinylidene complexes to ruthenium isonitrile derivatives
via aminocarbene intermediates has been carried out.
From a formal viewpoint, the formation of the isonitrile
complexes may be described as either a metal-assisted
aminolysis of the alkyne triple bond54 or a metal-
assisted oxidation of amines.19 The strong coordination
of the isonitrile ligands to ruthenium, however, repre-
Su p p or tin g In for m a tion Ava ila ble: Tables containing
crystal data and data collection parameters, positional pa-
rameters, anisotropic temperature factors, and bond distances
and angles for 8. This material is available free of charge via
the Internet at http://pubs.acs.org.
(53) Barrett, A. G. M.; Carpenter, N. E.; Sabat, M. J . Organomet.
Chem. 1988, 352, C8.
(54) For a review, see: (a) Chekulaeva, B.; Kondrat’eva, D. Russ.
Chem. Rev. (Engl. Transl.) 1965, 34, 669. (b) Dickstein, J . I.; Miller,
S. I. In The Chemistry of the Carbon-Carbon Triple Bond; Patai, S.,
Ed.; Wiley: Chichester, U.K., 1978; Vol. 24, Chapter 19.
OM990050G
(55) Brunner, H.; Vogel, M. J . Organomet. Chem. 1972, 35, 169.