Oxidative addition of ammonium and iminium tetraphenylborates to low-valent metal complexes. Evidence of selective N-C and N-H activation. A new, easy route to cationic allyl- And hydridonickel complexes

Article abstract of DOI:10.1021/om960602k

The reaction of ammonium and iminium tetraphenylborate salts ((CH₂dCHCH₂NH₃)BPh₄, [(CH₂dCHCH₂)HNdCMe₂]BPh₄, and [(PhCH₂)HNdCMe₂]BPh₄) with transition-metal systems in a low oxidation state has been investigated. We report the oxidative addition to (Cy₃P)₂Ni(η²-CO₂) or (Cy₃P)₂NiNtNNi(PCy₃)₂ under mild conditions (253-293 K) and describe a very selective NsC or NsH bond activation. (CH₂dCHCH₂NH₃)BPh₄ or [(CH₂dCHCH₂)HNdCMe₂]BPh₄ react with (Cy₃P)₂Ni(η²-CO₂) and (Cy₃P)₂NiNtNNi(PCy₃)₂ to afford the cationic π-allyl-Ni complexes [(η³-C₃H₅)Ni(PCy₃)(NH₃)]BPh₄ (1) and [(η³-C₃H₅)-Ni(PCy₃)(η¹(N)-HNdCMe₂)]BPh₄ (2), respectively. The reaction of [(PhCH₂)HNdCMe₂]BPh₄ with (Cy₃P)₂NiNtNNi(PCy₃)₂ leads to the hydrido-imino complex [trans-(H)Ni(PCy₃)₂(η¹-(N)-PhCH₂NdCMe₂)]BPh₄ (3) through NsH bond activation. Complexes 1-3 have been fully characterized in solution by NMR (¹H,¹³C,³¹P) spectroscopy. The hydrido-imino complex 3, characterized in the solid state by a X-ray diffraction study, shows a distorted-square-planar coordination around the nickel atom with a very narrow P-Ni-P angle, 148.6(2)°, involving the two P atoms from the trans PCy₃ ligands.

Full text of DOI:10.1021/om960602k

834
Organometallics 1997, 16, 834-841
Oxid a tive Ad d ition of Am m on iu m a n d Im in iu m
Tetr a p h en ylbor a tes to Low -Va len t Meta l Com p lexes.
Evid en ce of Selective N-C a n d N-H Activa tion . A New ,
Ea sy Rou te to Ca tion ic Allyl- a n d Hyd r id on ick el
Com p lexes
Michele Aresta,* Eugenio Quaranta, Angela Dibenedetto,
Potenzo Giannoccaro, and Immacolata Tommasi
Dipartimento di Chimica and Centro CNR MISO, Campus Universitario,
Universita´ di Bari, 70126 Bari, Italy
Maurizio Lanfranchi and Antonio Tiripicchio
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica,
Centro di Studio per la Strutturistica Diffrattometrica del CNR, Universita´ di Parma,
Viale delle Scienze, 43100 Parma, Italy
Received J uly 18, 1996X
The reaction of ammonium and iminium tetraphenylborate salts ((CH2dCHCH2NH3)BPh4,
[(CH2dCHCH2)HNdCMe2]BPh4, and [(PhCH2)HNdCMe2]BPh4) with transition-metal sys-
tems in a low oxidation state has been investigated. We report the oxidative addition to
(Cy3P)2Ni(η2-CO2) or (Cy3P)2NiNtNNi(PCy3)2 under mild conditions (253-293 K) and
describe a very selective NsC or NsH bond activation. (CH2dCHCH2NH3)BPh4 or
[(CH2dCHCH2)HNdCMe2]BPh4 react with (Cy3P)2Ni(η2-CO2) and (Cy3P)2NiNtNNi(PCy3)2
to afford the cationic π-allyl-Ni complexes [(η3-C3H5)Ni(PCy3)(NH3)]BPh4 (1) and [(η3-C3H5)-
Ni(PCy3)(η1(N)-HNdCMe2)]BPh4 (2), respectively. The reaction of [(PhCH2)HNdCMe2]BPh4
with (Cy3P)2NiNtNNi(PCy3)2 leads to the hydrido-imino complex [trans-(H)Ni(PCy3)2(η1-
(N)-PhCH2NdCMe2)]BPh4 (3) through NsH bond activation. Complexes 1-3 have been
fully characterized in solution by NMR (1H, 13C, 31P) spectroscopy. The hydrido-imino
complex 3, characterized in the solid state by a X-ray diffraction study, shows a distorted-
square-planar coordination around the nickel atom with a very narrow P-Ni-P angle,
148.6(2)°, involving the two P atoms from the trans PCy3 ligands.
In tr od u ction
of aliphatic and aromatic alkali-metal carbamates under
mild conditions.3
We have recently described, as a part of our studies
on the chemical utilization of carbon dioxide1a,b and
coordination chemistry of tetraphenylborates,1c,d a new
method of synthesis of alkylammonium tetraphenylbo-
rates (HL)BPh4 (L ) primary, secondary, or tertiary
aliphatic amine) based on the fixation of carbon dioxide
by amines in the presence of an alkali-metal BPh4- salt
(eq 1).2
Alkylammonium tetraphenylborates (HL)BPh4 are
currently used as proton transfer agents and act as
cocatalysts in some polymerization processes.4 The
traditional way of synthesis is based on the reaction of
NaBPh4 and an alkylammonium halide in aqueous
medium (eq 2),5a affording hydrated (HL)BPh4 salts,
(HL)X + NaBPh4 f NaX + (HL)BPh4
(2)
NHRR′ + CO2 + L + MBPh4 f
(HL)BPh4 + MO2CNRR′ (1)
although some substituted borates, i.e. B(C6F5)4 deriva-
tives,5b,c can be prepared by reaction of LiB(C6F5)4 with
tertiary amine hydrochlorides ((PhNMe2H)Cl, for ex-
ample) in CH2Cl2. As the anhydrous form is usually
required in most applications, further workup is needed
in the cases of hydrated salts and drying in vacuo for
R′ ) H, alkyl, L ) NHRR′; R ) aryl, R′ ) H,
L ) NR′′3 (R′′ ) alkyl); M ) Li, Na, K
Reaction 1 was revealed to be a new, versatile route
for both the preparation of alkylammonium BPh4- salts
under strictly anhydrous conditions and the synthesis
(3) Aresta, M.; Dibenedetto, A.; Quaranta, E. J . Chem. Soc., Dalton
Trans. 1995, 3359.
(4) Heeres, H. J .; Meetsma, A.; Teuben, J . H. J . Organomet. Chem.
1991, 414, 351. Seligson, A. L.; Trogler, W. C. Organometallics 1993,
12, 744. Horton, A. D.; Frijns, J . H. G. Angew. Chem., Int. Ed. Engl.
1991, 30, 1152. Borkowsky, S. L.; J ordan, R. F.; Hinch, G. D.
Organometallics 1991, 10, 1268. Bochmann, M.; Karger, G.; J aggar,
A. G. J . Chem. Soc., Chem. Commun. 1990, 1038. Lin, Z.; Le Marechal,
J .-F.; Sabat, M.; Marks, T. J . J . Am. Chem. Soc. 1987, 109, 4127.
(5) (a) Wittig, G.; Raff, P. J ustus Liebigs Ann. Chem. 1951, 573, 195.
(b) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245. (c)
Yang, X.; Stern, C. L.; Marks, T. J . Organometallics 1991, 10, 840.
X Abstract published in Advance ACS Abstracts, J anuary 15, 1997.
(1) (a) Aresta, M.; Quaranta, E.; Tommasi, I. New J . Chem. 1994,
18, 133. (b) Aresta, M.; Quaranta, E.; Tommasi, I.; Giannoccaro, P.;
Ciccarese, A. Gazz. Chim. Ital. 1995, 125, 509. (c) Aresta, M.;
Quaranta, E.; Albinati, A. Organometallics 1993, 12, 2032. (d) Aresta,
M.; Quaranta, E.; Tommasi, I. Gazz. Chim. Ital. 1993, 123, 271. (e)
Aresta, M.; Quaranta, E.; Tommasi, I.; De´rien, S.; Dunach, E. Orga-
nometallics 1995, 14, 3349.
(2) Aresta, M.; Quaranta, E. J . Organomet. Chem. 1995, 488, 211.
S0276-7333(96)00602-4 CCC: $14.00 © 1997 American Chemical Society

Ammonium and Iminium Tetraphenylborates
Organometallics, Vol. 16, No. 5, 1997 835
several days is applied under strictly controlled condi-
tions in order to avoid decomposition. The synthetic
methodology we have developed is of general application
and has quite improved the availability of the anhy-
drous salts.
systems. The X-ray structure of [trans-(H)Ni(PCy3)2-
(η1(N)-PhCH2NdCMe2)]BPh4 shows a distorted-square-
planar coordination around the nickel atom with a very
narrow P-Ni-P angle, 148.6(2)°, involving the two
trans P atoms from the PCy3 groups.
We have now investigated the reactivity of anhydrous
alkylammonium tetraphenylborates and found that, in
solution, according to the nature of the solvent, they can
either undergo an intramolecular proton transfer (eq 3)
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of Alk yla m m o-
n iu m a n d -im in iu m BP h 4 Sa lts. (CH2dCHCH2NH3)-
BPh4 and (PhCH2NH3)BPh4 were obtained by reacting
NaBPh4 or LiBPh4 with the amine (allylamine and
benzylamine, respectively) in the presence of carbon
(HL)BPh4 f PhH + LsBPh3
(3)
or intermolecularly transfer one proton to the solvent.
If acetone is used, iminium BPh4- salts are isolated as
stable products (eq 4).
dioxide (PCO ) 0.1 MPa) (eq 1). [(CH2dCHCH2)-
2
HNdCMe2]BPh4 and [(PhCH2)HNdCMe2]BPh4 have
been synthesized by reaction of (CH2dCHCH2NH3)BPh4
and (PhCH2NH3)BPh4, respectively, with acetone in the
presence of 4 Å molecular sieves as dehydrating agent,
at room temperature (293 K), according to eq 4 (R′ )
H; R ) allyl, benzyl).
(RR′NH2)BPh4 + Me2C(O) f
H2O + (RR′NdCMe2)BPh4 (4)
Interestingly, in the case of monoalkylammonium
salts (L ) primary amine), both the intra- and inter-
molecular proton transfer can be totally inhibited if a
suitable complexing agent (18-crown-6, for example),
able to coordinate the cation, is used.2
The reaction of alkylammonium tetraphenylborates
with alkyl or aryl transition-metal complexes, RnMLm,
has been investigated over the last few years, as the
former salts promote the protolytic cleavage of several
M-C bonds.4 In this way, a wide number of cationic or
zwitterionic (ηn-Ph)BPh3 metal complexes have been
synthesized, a few of which are active as catalysts for
alkene polymerization or olefin amination.
Iminium salts themselves occupy a key position in
many organic reactions, as they undergo rapid attack
by a wide number of nucleophiles.6a As for their
reactivity toward transition-metal complexes, iminium
ions represent very interesting molecular systems, since
they are both isoelectronic and isostructural with ole-
fins. It is known that N,N-dialkyl-substituted iminium
cations can coordinate to low-valent metal centers
through either the C-N double bond (η2(C,N))6b,c,d,g or
the electrophilic iminium carbon atom (η1(C)).6c,g Low-
valent transition-metal complexes can also promote the
transformation of iminium moieties into carbenes6c or
promote oxidative6f or reductive coupling reactions.6g It
is also worth noting that η2-coordinated iminium ions
are supposed to be intermediates in a few metal-
promoted transformations of tertiary amines.6h
All the salts have been characterized by elemental
analysis and spectroscopic techniques (IR, H and 13C
1
1
NMR). The IR and H NMR spectra of (CH2dCHCH2-
NH3)BPh4 and (PhCH2NH3)BPh4 have been reported in
a previous paper.2
The IR spectra of the iminium salts show a charac-
teristic medium-strong absorption around 1675 cm-1
assigned to the stretching of the iminium CdN bond.
The double bond hinders the CMe2 group rotation,
making the methyl groups nonequivalent. Such rigidity
is demonstrated by the existence of two distinct reso-
nances in the 1H and 13C NMR spectra of [(CH2d
CHCH2)HNdCMe2]BPh4 and [(PhCH2)HNdCMe2]BPh4.
The resonance of the iminium carbon atom is observed
near 192.5 ppm for both the salts, showing a consider-
able downfield shift with respect to the parent imine,
Me2CdNH, which resonates at 163.4 ppm.7
R ea ct ivit y of (CH 2dCH CH 2NH 3)BP h 4 t ow a r d
Ni(0)-Ter tia r y P h osp h in e Com p lexes: N-C Bon d
Activa tion . In previous papers,8,9 we have reported
that (Cy3P)2Ni(η2-CO2) can react with Brønsted acids
HX (X ) HS, PhS, Cl, Br, I) by two different reaction
pathways, depending on (i) the temperature and (ii) the
nature of the acid. Below 250 K, using H2S and PhSH,
which can act as (1e- + 1H+) transfer agents (HCl is
much less active) protonation of the bound CO2 with
subsequent reduction to bound CO is observed. At room
temperature, the oxidative addition of HX (Cl, Br, I) to
Ni is the preferential process with formation of (Cy3P)2-
Ni(H)X and CO2 elimination.
In this paper we report a study on the reactivity of
-
alkylammonium and -iminium BPh4 salts toward
complexes of Ni(0). (CH2dCHCH2NH3)BPh4, [(CH2d
CHCH2)HNdCMe2]BPh4, and [(PhCH2)HNdCMe2]BPh4
add oxidatively to Ni(0)-phosphine complexes, under
mild conditions, via a selective activation of the NsC
or NsH bond. The NsC cleavage in ammonium or
iminium salts, an uncommon reaction, represents a new,
easy way to the direct synthesis of cationic allyl-nickel
We have now investigated the reactivity of (CH2d
CHCH2NH3)BPh4 toward (Cy3P)2Ni(η2-CO2). Not sur-
prisingly, in THF at 253 K, [(η3-C3H5)Ni(PCy3)(NH3)]-
BPh4 (1) is formed as the only product according to eq
5.
(Cy3P)2Ni(η2-CO2) + (CH2dCHCH2NH3)BPh4
(6) (a) Hellmann, H.; Opitz, G. R-Aminoalkylation; Verlag Chemie:
Weinheim, Germany, 1960; p 1. (b) Mason, R.; Rucci, G. J . Chem. Soc.
D 1971, 1132. (c) Fong, C. W.; Wilkinson, G. J . Chem. Soc., Dalton
Trans. 1975, 1100. (d) Sepelak, D. J .; Pierpont, C. G.; Barefield, E.
K.; Budz, J . T.; Poffenberger, C. A. J . Am. Chem. Soc. 1976, 98, 6178.
(e) Barefield, E. K.; Sepelak, D. J . J . Am. Chem. Soc. 1979, 101, 6542.
(f) Barefield, E. K.; Carrier, A. M.; Sepelak, D. J .; Van Derveer, D. G.
Organometallics 1982, 1, 103. (g) Barefield, E. K.; Carrier, A. M.;
Sepelak, D. J .; Van Derveer, D. G. Organometallics 1985, 4, 1395. (h)
Murahashi, S.-I. Angew. Chem., Int. Ed. Engl. 1995, 34, 2443.
253 K, THF, CO2 or
N2 (0.1 MPa)
8
[(η3-C3H5)Ni(PCy3)(NH3)]BPh4 + PCy3 + CO2 (5)
Similarly, (CH2dCHCH2NH3)BPh4 reacts with (Cy3P)2-
NiNtNNi(PCy3)2 according to eq 6.

836 Organometallics, Vol. 16, No. 5, 1997
(Cy3P)2NiNtNNi(PCy3)2 +
Aresta et al.
The line broadening of both the 13C resonances of the
end allyl carbon atoms and H signals assigned to the
1
293 K, THF, N2
2(CH2dCHCH2NH3)BPh4
2[(η3-C3H5)Ni(PCy3)(NH3)]BPh4 + 2PCy3 + N2 (6)
8
H1, H2, and H4 protons of 1 suggests that the allyl
group in this complex is not rigidly bound to the metal
but is involved in a slow (with respect to the NMR time
scale) fluxional process.14,15 The slow fluxionality of the
system is also further supported by decoupling experi-
ments (Figure 1) in THF-d8, at 500 MHz and 293 K (the
undecoupled 1H spectrum under these conditions is
reported in the Experimental Section). Upon irradiation
of the signal at 3.73 ppm (H1), the multiplet at 5.38 ppm
(H5) converts into a triplet (J = 13.5 Hz), revealing that
under these conditions H5 can couple only to the anti
protons (H2 and H3)11 and no longer to H4 because of
saturation transfer16 from H1 to H4 through an ex-
change process. Accordingly, when the signal at 2.80
ppm (due to accidentally isochronous H2 and H4) is
saturated, the signal at 3.73 ppm (H1) practically
disappears and the multiplet at 5.38 ppm (H5) collapses
into a broad singlet as a result of saturation transfer
from H4 and H2 to H1 and H3, respectively.17 The
above experiments allow us also to establish the nature
of the fluxional process that involves left-to-right ex-
change of syn and anti protons (Scheme 1). In principle,
such a process could take place through free rotation of
the allyl group or the dissociation of the NH3 or PCy3
ligand. The first mechanism seems to be favored, at
least under the working conditions (293 K). In fact, the
13C spectrum of 1 (at 293 K) shows C-P coupling
between the phosphorus atom of the ligand and one of
the end allyl carbon atoms, thus excluding the possibil-
ity of a dissociative mechanism involving the P-ligand.
Furthermore, NH3 dissociation also appears to be quite
unlikely, as no spectroscopic evidence was found for the
formation of carbamic acid derivatives18 when reaction
5 was carried out under a carbon dioxide atmosphere.
Rea ctivity of [(CH2dCHCH2)HNdCMe2]BP h 4 to-
w a r d (Cy3P )2NiNtNNi(P Cy3)2: N-C Bon d Activa -
tion . The transfer of the allyl group from nitrogen to
nickel has been the only observed process also when
Ni(0) systems have been reacted with [(CH2dCHCH2)-
HNdCMe2]BPh4. In fact, the reaction of the iminium
tetraphenylborate salt with (Cy3P)2NiNtNNi(PCy3)2
affords selectively [(η3-C3H5)Ni(PCy3)(η1(N)-HNdCMe2)]-
BPh4 (2) in almost quantitative yield (eq 7).
Complex 1 has been characterized by IR spectroscopy
and NMR techniques (1H, 13C, 31P). The IR spectrum of
1 shows, in addition to the typical absorptions of the
uncoordinated BPh4- anion (1578, 1477, 1426, 745, 735,
705, 612 cm-1),2 characteristic bands in the range 3350-
3100 cm-1 (νNH) and at 1605 (δNH) and 513 cm-1. The
last absorption strongly supports the presence of an allyl
group π-coordinated to Ni.10 The presence of such a
group has been definitively confirmed by NMR spec-
troscopy.
1
The H NMR spectrum (CD2Cl2, 500 MHz, 293 K) of
1 shows four signals (2.60 and 2.57 (broad partially
overlapped singlets, 2 H, H2 and H4), 3.54 (broad
singlet, 1 H, H1), 5.19 (m, 1 H, H5, J = 7 Hz)) that can
be assigned to π-allyl protons.11 The resonance due to
H3 cannot be located, as it is obscured by the signals of
the PCy3 protons.12
In the 13C{1H} NMR spectrum (CD2Cl2, 125.76 MHz,
293 K) of 1 the three allyl carbon atoms resonate at
45.06 (s, broad, allylic Ccis), 73.89 (d, allylic Ctrans, 2J C-P
) 14 Hz), and 113.83 ppm (s, allylic Cmeso), respectively,
in good agreement with the results obtained by other
authors for structurally relevant systems.13 The pres-
ence of two signals for the end carbon atoms of the allyl
group clearly demonstrates that these nuclei are not
equivalent. This feature allows us to rule out a tetra-
hedral coordination to the nickel atom, being strongly
indicative of a square-planar ligand arrangement around
the metal center.
(Cy3P)2NiNtNNi(PCy3)2 +
293 K, toluene, N2
2[(CH2dCHCH2)HNdCMe2]BPh4
2[(η3-C3H5)Ni(PCy3)(η1(N)-HNdCMe2)]BPh4 +
8
(7) Pretsch, E.; Seibl, J .; Simon, W.; Clerc, T. Tables of Spectral Data
for Structure Determination of Organic Compounds; Springer-Verlag:
Berlin, 1983.
(8) Aresta, M.; Quaranta, E.; Tommasi, I. J . Chem. Soc., Chem.
Commun. 1988, 450.
2PCy3 + N2 (7)
(9) Aresta, M.; Gobetto, R.; Quaranta, E.; Tommasi, I. Inorg. Chem.
1992, 31, 4286.
(10) Green, M. L. H.; Nagy, L. I. Adv. Organomet. Chem. 1964, 2,
325.
(11) (a) Andrews, P.; Corker, J . M.; Evans, J .; Webster, M. J . Chem.
Soc., Dalton Trans. 1994, 1337. (b) Carmona, E.; Pilar, P.; Poveda,
M. L. Polyhedron 1990, 9, 757.
Imine coordination to nickel is strongly inferred by
the presence of both a sharp band at 3251 cm-1 (νNH
)
19
and a medium-weak absorption at 1656 cm-1 (νCdN
)
in the IR spectrum of 2. Coordination of imines to metal
(12) The reported assignment for the allyl protons H1-H4 is based
on decoupling experiments and the following considerations: (a) the
anti protons are, usually, more shielded than the corresponding syn
protons (δH1 > δH2; δH4 > δH3);10 (b) in related systems of formula (π-
allyl)Ni(P)(X) (P ) phosphine ligand; X ) halide, alkyl, aryl)11 the
resonance of the H1 proton is observed in the range 3-4.5 ppm, at
lower fields than the signals due to the H3-H4 protons.
(13) The assignment of the allyl carbon atoms is based on the values
of the chemical shift (see, for example, ref 11 and: J olly, P. W.; Stobbe,
S.; Wilke, G.; Goddard, R.; Kruger, C.; Sekutowski, J . C.; Tsay, Y.-H.
Angew. Chem., Int. Ed. Engl. 1978, 17, 124) and the fact that the allyl
carbon trans to a P-ligand is more strongly coupled to P than the cis
carbon atom.11
(14) J olly, P. W.; Mynott, R. Adv. Organomet. Chem. 1981, 19, 257.
(15) Vrieze, K.; Volger, H. C.; van Leeuwen, P. W. N. M. Inorg. Chim.
Acta Rev. 1969, 169.
(16) Mann, B. E. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, U. K., 1982; Vol. 3, p 89.
(17) The signal due to H3 cannot be observed in the spectrum, as it
is masked by the phosphine protons.
(18) Aresta, M.; Quaranta, E. Tetrahedron 1992, 48, 1515. Aresta,
M.; Quaranta, E. Tetrahedron 1991, 47, 9489.
(19) Cini, R.; Caputo, P. A.; Intini, F. P.; Natile, G. Inorg. Chem.
1995, 34, 1130. Fogg, D. E.; J ames, B. R. Inorg. Chem. 1995, 34, 2557.

Ammonium and Iminium Tetraphenylborates
Organometallics, Vol. 16, No. 5, 1997 837
F igu r e 1. 1H NMR (THF-d8, 500 MHz, 293 K) of [(η3-C3H5)Ni(PCy3)(NH3)]BPh4 in the 5.5-2.6 ppm region: (a) undecoupled
spectrum; (b) irradiation at 3.75 ppm; (c) irradiation at 2.78 ppm.
a medium absorption at 510 cm-1) and by means of
Sch em e 1. F lu xion a l Beh a vior of th e
[(η3-C3H5)Ni(P Cy3)(NH3)]+ Ca tion
NMR (1H, 13C) spectroscopy. As is the case for complex
1, only the signals due to the allyl protons H5 (5.39 ppm,
septet, J = 7 Hz), H1 (3.95 ppm, broad doublet, J = 7.3
Hz), and H2 and H4 (2.98 ppm, two slightly broad and
partially overlapping multiplets) can be observed in the
1H spectrum (CD2Cl2, 200 MHz, 293 K).21 The 13C
spectrum (CD2Cl2, 125.76 MHz, 293 K) shows the π-allyl
resonances in the usual range (48.65 d, allylic Ccis, 2J CP
centers is well-documented in the literature and may
involve the nitrogen atom (η1(N))19 or both the N and C
atoms (η2(C,N)).20 The 13C NMR spectrum of 2 allows
us to establish unambiguously that the imine ligand
mode of bonding is η1(N) in complex 2. In fact, η2(C,N)
) 6.06 Hz), 73.65 (d, allylic Ctrans,
2J CP ) 14.83 Hz),
114.09 (s, allylic Cmeso)).11,13 Interestingly, both end allyl
carbon atoms show coupling to phosphorus, and the
signals of protons H1, H2, and H4 exhibit a fine
structure. These spectroscopic features suggest that the
allyl group in complex 2 is more rigidly bound to nickel
than in 1. Varying the temperature within the range
188-308 K (at 200 MHz) produces some modifications
in the region of cyclohexyl protons but leaves practically
unchanged the chemical shifts of the allyl protons.
However, at 188 K the fine structure of the signals due
to the allyl protons is practically lost, probably because
of diminished resolution. Decoupling experiments
(CD2Cl2 as solvent) carried out at 308 K and 200 MHz
support the existence of a quite rigid allyl system. In
fact, when proton H1 is decoupled, the septet at 5.40
ppm converts into a triplet of doublets, whereas the
structure of the multiplets at about 3 ppm is only poorly
affected. Moreover, H5 decoupling converts the signal
at 3.96 ppm (H1) into a 1:2:2:1 quartet (J ) 2.4 Hz),
while the overlapping multiplets around 3 ppm (H2 and
H4) collapse into a poorly resolved broad signal.
imine coordination to a metal center causes a significant
high-field shift of the iminium carbon resonance,20 as
is the case in other π-systmes (olefins, arenes, etc.).
However, in complex 2 the iminium carbon resonance
is shifted downfield (188.38 ppm) with respect to the
free imine Me2CdNH (163.4 ppm), indicating that the
N atom is implied in a σ-interaction with the metal
center.
Syn th etic Im p lica tion of C-N Bon d Activa tion .
Reactions 5-7 thus allow the direct synthesis of cationic
(π-allyl)nickel complexes 1 and 2. Ionic π-allyl-Ni
complexes are of interest, as they are catalysts or
precursors of catalysts for reactions involving either
π-Coordination of the allyl group to nickel in complex
2 can be easily confirmed by its IR spectrum (showing
(20) Buchwald, S. L.; Watson, B. T.; Wannamaker, M. W.; Dewan,
J . C. J . Am. Chem. Soc. 1989, 111, 4486. Meyer, J . M.; Curtis, C. J .;
Bercaw, J . E. J . Am. Chem. Soc. 1983, 105, 2651.
(21) As for the case of 1, the resonance of H3 is masked by the
signals of phosphine protons.

838 Organometallics, Vol. 16, No. 5, 1997
Aresta et al.
olefins or dienes22 and are generally prepared in two
steps via halide abstraction from neutral π-allyl sys-
tems.22,23 Neibecker and Castro reported the synthesis
of a few cationic π-allyl nickel systems from Ni(CO)4 and
allyl derivatives, such as the poorly stable (allyloxy)-
tris(dimethylamino)phosphonium salts24 or less reactive
S-allyltetramethylthiouronium salts.25 These methods
involve allyl group transfer from an oxygen or a sulfur
atom to nickel and afford symmetric π-allyl complexes
of formula [(η3-allyl)Ni(L)2]X (L ) MeCN, PPh3, tetra-
methylthiourea). The reactions we have reported rep-
resent an easy way to obtain ionic π-allyl-Ni complexes
using stable, readily available, and very reactive allyl-
ammonium or -iminium salts. Interestingly, this way
allows the synthesis of unprecedented asymmetric cat-
ionic π-allyl complexes bearing both P- and N-ligands
in the coordination sphere of nickel.
To the best of our knowledge, the activation of a CsN
bond by Ni systems has been reported only once in the
literature: the cleavage of one of the C-N bonds of a
N,N′-bridged porphyrin by nickel tetracarbonyl under
more severe conditions.26 Pt and Ru compounds have
been reported27 to promote the cleavage of the allyl-N
bond of allylamines with subsequent transfer of the allyl
group to the metal center. The formation of nitrido
complexes by metathesis of W-W triple bonds with
nitriles,28 the four-electron oxidative addition of isocy-
anates, carbodiimides, and imine CdN double bonds to
Mo(II) or W(II) phosphine complexes to give Mo(VI)-
or W(VI)-imido compounds,29 and the nucleophile-
induced cleavage of a CsN bond of a η2(C,N)-coordinat-
ed pyridine ring30 are other examples of multiple CsN
bond activation.
Transition-metal-promoted breaking of CsN single
bonds31 is, probably, a major step in several catalytic
processes.32 The present work clearly shows that Ni(0)
complexes can promote the activation of a CsN bond
under very mild conditions and generate Ni systems
with interesting catalytic properties.
Rea ctivity of [(P h CH2)HNdCMe2]BP h 4 tow a r d
(Cy3P )2NiNtNNi(P Cy3)2: N-H Bon d Activa tion .
The reactivity of [(PhCH2)HNdCMe2]BPh4 toward
(Cy3P)2NiNtNNi(PCy3)2 markedly differs from that of
[(CH2dCHCH2)HNdCMe2]BPh4. In fact, the reaction
of [(PhCH2)HNdCMe2]BPh4 with (Cy3P)2NiNtNNi-
(PCy3)2, in THF at 293 K, affords the hydrido-imino
species [trans-(H)Ni(PCy3)2(η1(N)-PhCH2NdCMe2)]BPh4
(3) according to eq 8.
iminium NsH bond, other known examples of NsH
activation having been reported for ammonia, amines,
and amides.33 Reaction 8 is quite intriguing as, at least
from a formal point of view, it is reminiscent of 1-alkene
addition.34
Complex 3 has been fully characterized both in
solution (1H, 13C, 31P NMR) and in the solid state (IR,
X-ray). It is stable in the air and does not react with
CO2 (PCO ) 0.1-5 MPa, 293 K) even after long exposure
2
in solution.
The absence of any band above 3100 cm-1 and the
medium to weak absorptions observed at 1980 (m-w,
35
19
νNsH
)
and 1638 cm-1 (m, νCdN
)
in the IR spectrum
of 3 strongly suggest the presence of both a hydrido and
a tertiary imino group in the coordination sphere of
nickel. The complete characterization of 3 as a cationic
hydrido-imino-Ni complex was firmly established by
NMR spectroscopy and X-ray studies.
The 13C NMR spectrum (CD2Cl2, 125.76 MHz, 293 K)
of 3 shows a singlet at 179.42 ppm due to the imine
ligand η1(N)-coordinated to the metal (see above).
Sound evidence for a hydrido group bound to nickel
1
comes from the appearance in the H NMR spectrum
(CD2Cl2, 200 MHz, 293 K) of 3 of a triplet at -24.41
ppm (J HP ) 76.73 Hz). This pattern suggests a hydrido
group coupled to two equivalent P nuclei.35 In the 31P
spectrum (CH2Cl2, 81 MHz, 293 K) of 3, the signal (28.64
ppm) for the phosphorus atom of the phosphine ligands
is split into a doublet (J HP ) 76.73 Hz) because of the
coupling to the hydride hydrogen.
These features strongly suggest that, in solution, the
[(H)Ni(PCy3)2(η1(N)-PhCH2NdCMe2)]+ cation has a
square-planar geometry, with the phosphine ligands
trans to each other.35 Such a coordination geometry
around the nickel atom in complex 3 has been confirmed
in the solid state by an X-ray diffraction study. It is
worth noting that, even though both neutral and ionic
hydrido-bis(phosphine)-Ni complexes, (H)Ni(P)2(L) and
[(H)Ni(P)2(L)]X (P ) phosphine; L ) ancillary ligand),
(27) Hiraki, K.; Matsunaga, T. Organometallics 1994, 13, 1878.
Nagashima, H.; Katsunori, M.; Shiota, Y.; Ara, K.; Itoh, K.; Suzuki,
H.; Oshima, N.; Moro-oka, Y. Organometallics 1985, 4, 1314. Kuro-
sawa, H. Inorg. Chem. 1976, 15, 120.
(28) Schrock, R. R.; Listemann, M. L.; Sturgeoff, L. G. J . Am. Chem.
Soc. 1982, 104, 4293.
(29) Hall, K. A.; Mayer, J . M. J . Am. Chem. Soc. 1992, 114, 10402.
Bryan, J . C.; Mayer, J . M. J . Am. Chem. Soc. 1990, 112, 2298.
(30) Weller, K. J .; Gray, S. D.; Briggs, P. M.; Wigley, D. E.
Organometallics 1995, 14, 5588.
(31) Hagadorn, J . R.; Arnold, J . Organometallics 1994, 13, 4670.
Poszmik, G.; Carroll, P. J .; Wayland, B. B. Organometallics 1993, 12,
3410. Adams, R. D.; Chen, G. Organometallics 1993, 12, 2070.
(32) Roberto, D.; Alper, H. J . Am. Chem. Soc. 1989, 111, 7539.
Laine, R. M.; Thomas, D. W.; Cary, L. W. J . Am. Chem. Soc. 1982,
104, 1763. Roundhill, D. M. Chem. Rev. 1992, 92, 1.
(Cy3P)2NiNtNNi(PCy3)2 +
293 K, THF, N2
2[(PhCH2)HNdCMe2]BPh4
8
2[(H)Ni(PCy3)2(η1(N)-PhCH2NdCMe2)]BPh4 + N2
(33) For a few recent papers, see: Milstein, D.; Schulz, M. J . Chem.
Soc., Chem. Commun. 1993, 318. Schaad, D. R.; Landis, C. R.
Organometallics 1992, 11, 2024. Gagne´, M. R.; Stern, C. L.; Marks,
T. J . J . Am. Chem. Soc. 1992, 114, 275.
(8)
(34) Stoutland, P. O.; Bergmann, R. G. J . Am. Chem. Soc. 1988, 110,
5732.
To the best of our knowledge, reaction 8 represents
the first example of transition-metal activation of an
(35) (a) Green, M. L. H.; Saito, T.; Tanfield, P. J . J . Chem. Soc. A
1971, 152. (b) Green, M. L. H.; Munakata, H.; Saito, T. J . Chem. Soc.
A 1971, 469. (c) Imoto, H.; Moriyama, H.; Saito, T.; Sasaki, Y. J .
Organomet. Chem. 1976, 120, 453. (d) Clark, H. C.; Shaver, A. Can.
J . Chem. 1975, 53, 3462. (e) J onas, K.; Wilke, G. Angew. Chem., Int.
Ed. Engl. 1969, 8, 519. (f) Darensbourg, D. J .; Darensbourg, M. Y.;
Goh, L. Y.; Ludwig, M.; Wiegreffe, P. J . Am. Chem. Soc. 1987, 109,
7539. (g) Darensbourg, M. Y.; Ludwig, M.; Riordan, C. G. Inorg. Chem.
1989, 28, 1630. (h) Seligson, A. L.; Cowan, R. L.; Trogler, W. C. Inorg.
Chem. 1991, 30, 3371. (i) Mu¨ller, U.; Keim, W.; Kru¨ger, C.; Betz, P.
Angew. Chem., Int. Ed. Engl. 1989, 28, 1011.
(22) Wilke, G. Angew. Chem., Int. Ed. Engl. 1988, 27, 185. Keim,
W. Angew. Chem., Int. Ed. Engl. 1990, 29, 235. Tolman, C. A. J . Am.
Chem. Soc. 1970, 92, 6777. Commereuc, D.; Chauvin, Y. Bull. Soc.
Chim. Fr. 1974, 652.
(23) J olly, P. W.; Wilke, G. The Organic Chemistry of Nickel;
Academic Press: New York, 1974.
(24) Castro, B.; Neibecker, D. J . Organomet. Chem. 1975, 85, C39.
Castro, B.; Neibecker, D. J . Organomet. Chem. 1977, 134, 105.
(25) Castro, B.; Neibecker, D. Tetrahedron Lett. 1977, 27, 2351.
(26) Chan, Y. W.; Renner, M. W.; Balch, A. L. Organometallics 1983,
2, 1888.
(36) Gregory, U. A.; Kilbourn, B. T. Private communication to Frenz,
B. A. and Ibers, J . A. Quoted in: Transition Metal Hydrides; Dekker:
New York, 1971; p 45.

Ammonium and Iminium Tetraphenylborates
Organometallics, Vol. 16, No. 5, 1997 839
Ta ble 2. Exp er im en ta l Da ta for th e
Cr ysta llogr a p h ic An a lysis of 3‚CH2Cl2
formula
mol wt
C71H102BCl2NNiP2
1171.975
cryst syst
orthorhombic
space group
a, Å
P212121
14.943(4)
b, Å
32.218(5)
c, Å
13.931(3)
6707(3)
V, Å3
Z
4
Dc, Mg m-3
F(000)
1.161
2528
temp, K
295
diffractometer
radiation (λ ) 1.541 838 Å)
µ, cm-1
Siemens AED
graphite-monochromated Cu KR
18.89
3-12
1.20 + 0.142 tan θ
θ/2θ
3-60
5554
1819 (I > 2σ(I))
0.0642
scan speed, deg min-1
scan width, deg
scan mode
θ range, deg
no. of rflns measd
no. of obsd rflns
R ) ∑|∆F|/∑|Fo|
Rw ) [∑w(∆F)2/∑wFo
]
0.0761
2
1/2
Ni-P bonds are equal, 2.220(6) and 2.223(5) Å, and the
two trans P atoms form with the Ni atom an angle of
148.6(2)°, the strong distortion being due to the presence
of three adjacent bulky ligands. The values of the Ni-P
bonds are quite normal if compared to the mean value
2.211 Å (from the Cambridge Structural Database)
found in four-coordinate nickel(II) complexes with PCy3
ligands, whereas that of the Ni-N bond, 1.94(1) Å, is
slightly longer than the mean value 1.888 Å (from the
CSD) found with comparable N-donor ligands. The
fragment (CH2)2CdNCH2 of the imine ligand (except for
the hydrogen atoms) is planar (maximum deviation
0.03(2) Å for N) and is almost perpendicular to the
coordination mean plane (dihedral angle 98.1(5)°). Each
of the two PCy3 groups is oriented in such a way that a
PsC bond (P1-C11 and P2-C41) eclipses approxi-
mately the Ni-N bond, confirming a strong steric
hindrance which probably is responsible for the remark-
able deviation of the P1-Ni-P2 angle from the theo-
retical value of 180°. The other two P-C bonds of each
PCy3 group are staggered with respect to the Ni-H
bond, and this feature causes the complete caging of the
hydride, also accentuated by the narrowing of the P1-
Ni-P2 angle.
F igu r e 2. ORTEP view of the structure of the [trans-
(H)Ni(PCy3)2(η1(N)-PhCH2NdCMe2)]+ cation of complex 3
with the atomic numbering scheme. The ellipsoids for the
atoms are drawn at the 30% probability level.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 3‚CH2Cl2
Ni-P1
Ni-P2
Ni-N
2.220(6)
2.223(5)
1.94(1)
1.65(9)
1.88(2)
1.83(2)
1.87(2)
1.87(2)
P2-C35
P2-C41
N-Cl
1.81(2)
1.83(2)
1.25(3)
1.51(3)
1.48(3)
1.54(3)
1.45(3)
Ni-H
N-C4
P1-C11
P1-C17
P1-C23
P2-C29
C1-C2
C1-C3
C4-C5
N-Ni-H
166(3)
78(5)
110.1(5)
72(3)
101.3(5)
148.6(2)
112.1(6)
110.1(6)
116.8(6)
103.7(8)
102.2(8)
110.9(8)
119.4(6)
Ni-P2-C35
Ni-P2-C29
C35-P2-C41
C29-P2-C41
C29-P2-C35
Ni-N-C4
110.0(6)
111.3(6)
108.2(8)
103.1(8)
103.5(8)
115(1)
127(1)
118(2)
127(2)
121(2)
P2-Ni-H
P2-Ni-N
P1-Ni-H
P1-Ni-N
P1-Ni-P2
Ni-P1-C23
Ni-P1-C17
Ni-P1-C11
C17-P1-C23
C11-P1-C23
C11-P1-C17
Ni-P2-C41
Ni-N-C1
C1-N-C4
N-C1-C3
N-C1-C2
C2-C1-C3
N-C4-C5
112(2)
117(2)
Complex 3 is one of the few structurally characterized
nickel(II) complexes with a terminal hydride (Ni-H )
1.65(9) Å). The hydride was not localized in the neutral
(H)Ni(PBz3)2(OPh) complex,35h in which the values of
the Ni-P bonds, 2.163(3) and 2.171(3) Å (tribenzylphos-
phine ligands), are shorter than those found in 3 and
the P-Ni-P angle, 159.0(1)°, is indicative of a strong
distortion, as in 3. In (H)Ni(PCy3)[PPh2CH2C(CF3)2O-
P,O]35i the hydride is localized (Ni-H ) 1.37(3) Å), the
value of the Ni-P bond (PCy3 ligand) is 2.181(1) Å, and
the P-Ni-P angle is 173.1(1)°, due to a different steric
hindrance of the ligands with respect to the other two
complexes.
respectively, have been known for a long time,35 their
characterization by X-ray diffraction is very incom-
plete.35h,i,36
Descr ip tion of th e Cr ysta l Str u ctu r e of [tr a n s-
(H )Ni(P Cy3)2(η1(N)-P h CH 2NdCMe2)]BP h 4‚CH 2Cl2
(3‚CH2Cl2). A single-crystal X-ray study (Table 1) of
the dichloromethane solvate of 3 was carried out. In
the crystals, cationic moieties [trans-(H)Ni(PCy3)2(η1(N)-
PhCH2NdCMe2)]+, BPh4- anions, and molecules of the
solvent CH2Cl2 are present. The structure of the
cationic complex is shown in Figure 2 together with the
atom-numbering scheme. Selected bond distances and
angles are listed in Table 2. The coordination around
the nickel atom is distorted square planar and involves
two P atoms from the PCy3 groups in a trans position,
a N atom from the imine ligand, and a terminal hydride.
The atoms involved in the coordination are practically
coplanar, except for the hydride, which is out of the
mean plane through the other atoms by 0.3(2) Å. The
These structural features, as well as the ionic char-
acter of the complex and the nature of the ligand trans
to the hydride (imine vs Ph or Me; see below), can
explain the inertness of 3 toward carbon dioxide. The
Ni-H bond is quite protected by the P-ligands, which
prevents the reaction with CO2 and makes this complex
quite different from (H)Ni(PCy3)2(Me) or (H)Ni(PCy3)2-

840 Organometallics, Vol. 16, No. 5, 1997
Aresta et al.
(B) (P h CH2NH3)BP h 4. A THF (85 mL) solution of LiBPh4‚
3MeOCH2CH2OMe (2.601 g, 4.36 mmol) and PhCH2NH2 (0.95
mL, 8.72 mmol), prepared under dinitrogen, was saturated
with CO2 at 273 K. The white suspension of LiO2CNH(CH2Ph)
was treated with pentane (20 mL), cooled to 253 K, and
filtered. After the lithium carbamate on the filter was washed
with THF (3 × 10 mL), the mother liquor and washing
solutions were collected and concentrated in vacuo. Upon
addition of pentane (100 mL) and cooling to 253 K, a white
precipitate was obtained, isolated by filtration and identified
as (PhCH2NH3)BPh4‚0.5THF (1.798 g, 89%). Anal. Calcd for
C33H34BNO0.5: C, 85.52; H, 7.39; N, 3.02. Found: C, 85.48;
H, 7.26; N, 3.09.
(Ph), both of which have been reported to insert CO2
into the Ni-H bond to give neutral formate Ni com-
plexes.35f
Con clu sion s
The first examples of oxidative addition of alkylam-
monium or -iminium cations to a transition-metal center
have been described.
The interaction of the allylammonium and -iminium
tetraphenylborate salts (CH2dCHCH2NH3)BPh4 and
[(CH2dCHCH2)HNdCMe2]BPh4 with Ni(0)-phosphine
complexes (Cy3P)2Ni(η2-CO2) and (Cy3P)2NiNtNNi-
(PCy3)2 results in the activation, under mild conditions,
of the CsN single bond and affords, in one step,
unprecedented asymmetric cationic π-allyl-Ni com-
plexes of formula [(η3-C3H5)Ni(P)(N)]BPh4, containing
both a P- and N-ligand in the coordination sphere of Ni.
When the allyl group is exchanged for an aliphatic or
aromatic group, the reactivity of the BPh4 salts is
strongly influenced and the N-H, rather than the NsC,
activation takes place.
Syn th esis of [(CH2dCHCH2)HNdCMe2]BP h 4. The syn-
thesis of [(CH2dCHCH2)HNdCMe2]BPh4 and its characteriza-
tion by IR and 1H NMR have been reported in ref 2. Below
we report the 13C NMR spectrum. 13C{1H} NMR (THF-d8,
125.76 MHz, 293 K): δ 19.62 (Me), 25.35 (Me), 49.05
(-CH2CHdCH2), 119.72 (-CH2CHdCH2), 128.16 (CH2CHd
CH2), 192.86 (Me2CdNH-), 120.72 (Cpara,BPh4), 124.60 (q,
Cmeta,BPh , 3J CB ) 2.6 Hz), 135.69 (Cortho,BPh ), 163.72 (q, Cipso,BPh
,
4
4
4
1J CB ) 49.31 Hz). The above assignment is supported by a
13C DEPT experiment.
Syn th esis of [(P h CH2)HNdCMe2]BP h 4. To an acetone
(10 mL) solution of (PhCH2NH3)BPh4‚0.5THF (1.380 g, 2.98
mmol), prepared under dinitrogen, were added 4 Å molecular
sieves. The mixture was stirred for 1.5 h at room temperature
(293 K) and then filtered. After the residue on the filter was
washed with acetone (2 × 5 mL), the mother liquor and
washing solutions were collected, treated with diethyl ether
(50 mL), and cooled to 253 K. The white solid that precipitated
was filtered, washed with diethyl ether (2 × 8 mL), and dried
in vacuo (0.874 g, 58%). Anal. Calcd for C34H34BN: C, 87.36;
H, 7.33; N, 2.99. Found: C, 86.99; H, 7.34; N, 2.78. IR (Nujol,
KBr disks, cm-1): 3330 (vw), 3230 (m, broad), 3150 (m), 1673
(m-s, νCdN), 1580 (m), 1495 (m-w), 1480 (m-s), 1428 (m), 1370
(m-s), 746 (s), 735 (s), 720 (m), 712 (s), 695 (m). 1H NMR
(CD2Cl2, 200 MHz, 293 K): δ 1.59 (s, 3 H, Me), 1.80 (s, 3 H,
Me), 3.81 (slightly broad, 2 H, PhCH2), 6.89 (tt, 4 H, Hpara,BPH4),
In fact, the reaction of [(PhCH2)HNdCMe2]BPh4 with
(Cy3P)2NiNtNNi(PCy3)2 leads to the hydrido-imino
complex [trans-(H)Ni(PCy3)2(η1(N)-PhCH2NdCMe2)]-
BPh4 through N-H bond activation. This reaction
represents the first documented example of oxidative
addition of an iminium N-H bond to a metal center.
Exp er im en ta l Section
Gen er a l Com m en ts. Unless otherwise stated, all reac-
tions and manipulations were conducted under a dinitrogen
or carbon dioxide atmosphere (as specified in the text), by
using vacuum line techniques. All solvents were dried as
described in the literature37 and stored under dinitrogen.
Amines (Fluka, Aldrich) were dried37 and distilled before use.
NaBPh4 (Aldrich or Baker) and LiBPh4‚3MeOCH2CH2CH2OMe
(Strem or Aldrich) were used as received. (Cy3P)2Ni(η2-CO2)
and (Cy3P)2NiNtNNi(PCy3)2 have been prepared as previously
reported.38,39
IR spectra were obtained with a Perkin-Elmer 883 spectro-
photometer. NMR spectra were run on a Varian XL-200 or a
Bruker AM 500 instrument. 1H and 13C chemical shifts are
in ppm vs TMS and are referenced to the solvent peak. 31P
resonances are reported in ppm vs H3PO4.
Syn th esis of (HL)BP h 4 Sa lts (L ) (CH2dCHCH2)NH2,
P h CH2NH2). The synthesis of (CH2dCHCH2NH3)BPh4 and
(PhCH2NH3)BPh4 from the corresponding amine, NaBPh4, and
CO2 and their spectroscopic characterization (IR, 1H NMR)
have already been reported elsewhere.2 Below we report the
synthesis of these salts from LiBPh4.
(A) (CH2dCHCH2NH3)BP h 4. A THF (35 mL) solution of
LiBPh4‚3MeOCH2CH2OMe (0.964 g, 1.62 mmol) and CH2d
CHCH2NH2 (0.25 mL, 3.32 mmol), prepared under dinitrogen,
was saturated with CO2 at 273 K. The white suspension of
LiO2CNH(CH2CHdCH2) was treated with pentane (25 mL),
cooled to 253 K, and filtered. After the lithium carbamate was
washed on the filter with dichloromethane (2 × 5 mL), the
mother liquor and washing solutions were collected and
concentrated in vacuo. Upon addition of pentane (40 mL) and
cooling to 253 K, a white precipitate of (CH2dCHCH2NH3)-
BPh4 was obtained and isolated by filtration (0.550 g, 90%).
7.04 (t, 8 H, Hmeta,BPh , J ) 7.2 Hz), 7.50 (m, 8 H, Hortho,BPh4),
4
6.82-6.88 and 7.34-7.38 (two multiplets, 5 H, PhCH2).
13C{1H} NMR (CD2Cl2, 125.76 MHz, 293 K): δ 21.04 (Me),
27.30 (Me), 51.52 (-CH2Ph), 192.44 (Me2CdNH-), 122.00
3
(Cpara,BPh ), 126.03 (q, Cmeta,BPh , J CB ) 2.7 Hz), 135.28 (Cortho,B
-
4
Ph ), 163.84 (q, Cipso,BPh , 1J CB )449.2 Hz), 126.95, 129.00, 130.40,
4
4
and 133.13 (-CH2Ph).
Rea ction of (CH2dCHCH2NH3)BP h 4 w ith (Cy3P )2Ni(η2-
CO2). Syn th esis of [(η3-C3H5)Ni(P Cy3)(NH3)]BP h 4. To a
solution of (Cy3P)2Ni(η2-CO2) (0.187 g, 0.282 mmol) in THF (3
mL), prepared under dinitrogen at 253 K, was added 0.110 g
of (CH2dCHCH2NH3)BPh4 (0.292 mmol) dissolved in THF (3
mL) and the resulting mixture was stirred at 253 K. The
solution, initially orange, turned to greenish yellow, then to
brown and, after a few hours (3-4 h), to yellowish orange. The
reaction mixture was filtered and, after addition of pentane
(15 mL), cooled to 253 K. The yellow crystals that precipitated
were isolated by filtration, washed with pentane (5 mL), and
dried in vacuo (0.147 g, 74%). Anal. Calcd for C45H61NBPNi:
C, 75.43; H, 8.58; N, 1.95; Ni, 8.19; P, 4.32. Found: C, 74.94;
H, 8.54; N, 1.92; Ni, 8.11; P, 4.43. IR (Nujol, KBr disks, cm-1):
3337 (m-w), 3310 (m), 3255 (m), 3175 (m-w), 1605 (m-w,
broad), 1578 (m), 1477 (m), 1446 (m-s), 1428 (m), 1275 (m),
1265 (m), 1175 (m), 1035 (m), 1005 (m), 935 (m), 845 (m-s),
745 (s), 735 (s), 705 (s), 612 (m-s), 513 (m). 1H NMR (CD2Cl2,
500 MHz, 293 K): δ -0.59 (s, broad, 3 H, NH3), 1.1-2.0 (34
H, Cy protons and H3), 2.60 and 2.57 (broad partially
overlapped singlets, 2 H, H2 and H4), 3.54 (broad singlet, 1
Anal. Calcd for
C27H28BN: C, 85.94; H, 7.48; N, 3.71.
Found: C, 85.69; H, 7.55; N, 3.61.
H, H1), 5.19 (septet, 1 H, H5, J = 7 Hz), 6.91 (t, 4 H, Hpara,BPh
,
4
(37) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, U.K., 1986.
(38) Aresta, M.; Nobile, C. F.; Albano, V. G. J . Chem. Soc., Chem.
Commun. 1975, 636.
(39) Aresta, M.; Nobile, C. F.; Sacco, A. Inorg. Chim. Acta 1975, 12,
167.
J ) 6.93 Hz), 7.08 (t, 8 H, Hmeta,BPh4, J ) 7.24 Hz), 7.49 (m, 8
H, Hortho,BPh4). The signal at δ -0.59 disappears upon addition
of D2O. 1H NMR (THF-d8, 500 MHz, 293 K): δ 1.2-2.0 (Cy
protons and H3), 2.80 (broad singlet, H2 and H4), 3.73 (broad
singlet, H1), 5.38 (septet, H5, J = 7 Hz), 6.74 (t, Hpara,BPh4, J )

Ammonium and Iminium Tetraphenylborates
Organometallics, Vol. 16, No. 5, 1997 841
7.17 Hz), 6.89 (t, Hmeta,BPh , J ) 7.40 Hz), 7.32 (m, Hortho,BPh4).
58.86 (s, PhCH2), 121.37 (Cpara,BPh ), 125.28 (Cmeta,BPh4), 127.39
4
4
13C{1H} NMR (CD2Cl2, 125.76 MHz, 293 K): δ 25.86 (s, Cδ,PCy ),
(PhCH2), 128.21 (PhCH2), 128.84 (PhCH2), 133.98 (Cipso PhCH2),
3
3
135.60 (Cortho),BPh4), 163.75 (q, Cipso,BPh
,
1J CB ) 49.2 Hz),
27.15 (d, isochronous diastereotopic Cγ,PCy and Cγ′,PCy , J CP
)
3
3
4
179.49 (s, Me2CdN). 31P NMR (CH2Cl2, 81 MHz, 293 K): δ
28.64 (d, J HP ) 76.53 Hz).
10.16 Hz), 29.67 and 29.76 (singlets, diastereotopic Câ,PCy3 and
Câ′,PCy ), 33.47 (d, CR,PCy
,
3
1J CP ) 19.40 Hz), 45.06 (s, broad,
3
allylic Ccis), 73.89 (d, allylic Ctrans,
2J CP ) 14 Hz), 113.83 (s,
X-r a y Da ta Collection , Str u ctu r e Deter m in a tion , a n d
R efin em en t for [tr a n s-(H )Ni(P Cy3)2(η1(N)-P h CH2Nd
CMe2)]BP h 4‚CH2Cl2 (3‚CH2Cl2). The crystals for the X-ray
analysis were obtained by recrystallization from dichlo-
romethane solutions. All crystals were of very small size; one
of them, having dimensions 0.15 × 0.18 × 0.21 mm, was used
for data collection on a Siemens AED diffractometer at room
temperature. Crystallographic data are summarized in Table
2. A total of 5554 unique reflections were measured with θ in
the range 3-60°; only 1819 of them, having I > 2σ(I), were
used in the refinement. One standard reflection was moni-
tored every 100 measurements; no significant decay was
noticed over the time of data collection. Intensities were
corrected for Lorentz and polarization effects. No correction
for absorption was applied.
allylic Cmeso), 121.68 (Cpara,BPh ), 125.80 (Cmeta,BPh4), 135.38
4
(Cortho,BPh ), 163.98 (q, Cipso,BPh , 1J CB ) 49.2 Hz). 31P{1H} NMR
4
4
(CH2Cl2, 202.45 MHz, 293 K): δ 33.46.
R ea ct ion of [(CH2dCH CH2)H NdCMe2]BP h 4 w it h
(Cy3P )2NiNtNNi(P Cy3)2. Syn th esis of [(η3-C3H5)Ni(P Cy3)-
(η1(N)-HNdCMe2)]BP h 4. To a solution of (Cy3P)2NiNtNNi-
(PCy3)2 (0.290 g, 0.229 mmol) in toluene (30 mL) was added
0.199 g (0.477 mmol) of [(CH2dCHCH2)HNdCMe2]BPh4, and
the resulting suspension was stirred at room temperature (293
K) under dinitrogen. The purple-red solution fast turned to
greenish yellow, then to brown, and, finally, to yellow. The
yellow solid that precipitated was filtered, washed with toluene
(5 mL) and pentane (5 mL), dried in vacuo, and then recrystal-
lized from CH2Cl2/pentane (0.242 g, 70%). Anal. Calcd for
C48H65NBPNi: C, 76.20; H, 8.66; N, 1.85; Ni, 7.76; P, 4.10.
Found: C, 76.20; H, 8.58; N, 1.83; Ni, 7.8; P, 4.10. IR (Nujol,
KBr disks, cm-1): 3251 (m, sh), 1656 (m-w, br, νCdN), 1580
(m-w), 1475 (m), 1447 (s), 1425 (m), 1411 (m), 746 (s), 731 (s),
703 (s), 610 (m-s), 510 (m-w). 1H NMR (CD2Cl2, 200 MHz, 293
K): δ 1.1-2.0 (34 H, Cy protons and H3), 2.05 (s, 3 H, Me),
2.25 (s, 3 H, Me), 2.98 (two slightly broad and partially
overlapped multiplets, 2 H, H2 and H4), 3.95 (broad doublet,
1 H, H1, J = 7.3 Hz), 5.39 (septet, 1 H, H5, J = 7 Hz), 6.88 (t,
The structure was solved by Patterson and Fourier methods
and refined first by full-matrix least-squares procedures with
isotropic thermal parameters and then by full-matrix least-
squares procedures with anisotropic thermal parameters in
the last cycles of refinement for the non-hydrogen atoms,
except for the carbons of the cyclohexyl groups. In the crystals
dichloromethane molecules of solvation were found. The
hydride was clearly localized in the final ∆F map and refined
isotropically; all other hydrogen atoms were placed at their
geometrically calculated positions (C-H ) 0.96 Å) and refined
“riding” on the corresponding carbon atoms, isotropically.
Since the space group P212121 leads to a chiral configuration
in the structure, a refinement of the non-hydrogen atoms with
anisotropic thermal parameters was carried out using the
coordinates -x, -y, -z; an increasing in the R and Rw values
was obtained (R(x,y,z) ) 0.0642, Rw(x,y,z) ) 0.0761; R(-x,-
y,-z) ) 0.0666, Rw(-x,-y,-z) ) 0.0790). The former model
was selected, and the reported data refer to this model. The
final cycles of refinement were carried out on the basis of 407
variables; after the last cycles, no parameters shifted by more
than 0.8 esd. The highest remaining peak in the final
difference map was equivalent to about 0.27 e/Å3. In the final
4 H, Hpara,BPh , J ) 6.9 Hz), 7.03 (t, 8 H, Hmeta,BPh4, J ) 7.1 Hz),
4
7.31 (m, 8 H, Hortho,BPh4), 7.66 (s, broad, 1 H, NH). 13C{1H}
NMR (CD2Cl2, 125.76 MHz, 293 K): δ 25.85 (s, Cδ,PCy ), 27.19
3
(d, diastereotopic Cγ,PCy ,
3J CP ) 10.38 Hz), 27.23 (d, diaste-
3
3
reotopic Cγ′,PCy , J CP ) 10.38 Hz), 28.29 (s, Me), 29.50 (s, Me),
3
29.74 and 30.01 (singlets, diastereotopic Câ,PCy and Câ′,PCy ),
3
3
1
2
33.43 (d, CR,PCy , J CP ) 19.95 Hz), 48.65 (d, allylic Ccis, J CP
)
3
6.06 Hz), 73.65 (d, allylic Ctrans
allylic Cmeso), 121.39 (Cpara,BPh ), 125.29 (Cmeta,BPh4), 135.06
,
2J CP ) 14.83 Hz), 114.09 (s,
4
(Cortho,BPh ), 163.7 (q, Cipso,BPh
,
1J CB ) 49.6 Hz), 188.38 (s,
4
4
Me2CdN). The assignment is also supported by the 13C APT
NMR (CD2Cl2, 50.3 MHz, 293 K) spectrum. 31P{1H} NMR
(CH2Cl2, 81 MHz, 293 K): δ 33.60.
Rea ction of [(P h CH2)HNdCMe2]BP h 4 w ith (Cy3P )2-
NiNtNNi(P Cy3)2. Syn t h esis of [(H)Ni(P Cy3)2(η1(N)P h -
CH2NdCMe2)]BP h 4. To a solution of (Cy3P)2NiNtNNi-
(PCy3)2 (0.401 g, 0.317 mmol) in THF (12 mL), prepared under
dinitrogen at 293 K, was added 0.309 g of [(PhCH2)HNdCMe2]-
BPh4 (0.660 mmol) dissolved in THF (5 mL). Upon mixing of
the reactants, the solution fast turned from purple-red to dark
and, then, to yellowish brown. After it was stirred at room
temperature for 5 h, the reaction solution was concentrated,
added with diethyl ether, and cooled to 253 K.
cycles of refinement the weighting scheme w ) K[σ2(Fo) +
2
gFo
]
-1 was used; at convergence the K and g values were 0.733
and 0.003. Final R and Rw values were 0.0642 and 0.0761,
respectively. The analytical scattering factors, corrected for
the real and imaginary parts of anomalous dispersion, were
taken from ref 40. All calculations were carried out on the
Gould Powernode 6040 and Encore 91 computers of the
“Centro di Studio per la Strutturistica Diffrattometrica” del
CNR, Parma, Italy, using the SHELX-76 and SHELXS-86
systems of crystallographic computer programs.41
The separated solid was filtered, washed with diethyl ether
(2 × 10 mL), dried in vacuo, and then recrystallized from
CH2Cl2 (8 mL)/diethyl ether (40 mL) at 253 K. The crystals
that precipitated were isolated by filtration, washed with
diethyl ether, dried in vacuo, and characterized as [(H)Ni-
(PCy3)2(η1(N)-PhCH2NdCMe2)]BPh4‚CH2Cl2. (0.520 g, 70%).
One of these crystals was used for the X-ray characterization.
Anal. Calcd for C71H102NBP2Cl2Ni: C, 72.76; H, 8.77; N, 1.19;
Ni, 5.01; P, 5.29. Found: C, 73.10; H, 9.02; N, 1.15; Ni, 4.89;
P, 4.93. IR (Nujol, KBr disks, cm-1): 1980 (νNsH, m-w), 1638
(νCdN, m), 1578 (m), 1477 (m), 1448 (m-s), 1425 (m), 1264 (m),
1174 (m), 1135 (m), 1030 (m), 1002 (m), 887 (m), 848 (m-s),
745 (m-s), 732 (s), 703 (s), 611 (m-s), 511 (m). 1H NMR
(CD2Cl2, 200 MHz, 293 K): δ -24.41 (t, 1 H, NiH, J HP ) 76.73
Hz), 1.1-1.9 (Cy protons), 2.13 (s, 3 H, Me), 2.79 (s, 3 H, Me),
4.99 (PhCH2), 6.88 (t, 4 H, Hpara,BPh4, J ) 7 Hz), 7.04 (t, 8 H,
Ack n ow led gm en t. Financial support from the Ital-
ian MURST (40%, 60%) is acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Tables of final
values of atomic coordinates for the non-hydrogen atoms,
calculated coordinates and isotropic thermal parameters for
the hydrogen atoms, anisotropic thermal parameters for some
of the non-hydrogen atoms, and all bond distances and angles
for 3 (7 pages). Ordering information is given on any current
masthead page.
OM960602K
Hmeta,BPh , J ) 7 Hz), 7.11 (PhCH2), 7.33 (m, 8 H, Hortho,BPh4),
(40) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. IV.
(41) Sheldrick, G. M. SHELX-76 Program for Crystal Structure
determination; University of Cambridge, Cambridge, U.K., 1976.
Sheldrick, G. M. SHELXS-86 Program for the Solution of Crystal
Structures; University of Go¨ttingen, Go¨ttingen, Germany, 1986.
4
7.41 (PhCH2). 13C{1H} NMR (CD2Cl2, 125.76 MHz, 293 K): δ
22.01 (s, Me), 25.84 (s, Cδ,PCy ), 27.12 (virtual t, Cγ,PCy and
3
3
Cγ′,PCy , J ) 5.09 Hz), 29.72 and 29.83 (singlets, Câ,PCy and
3
3
Câ′,PCy ), 32.90 (s, Me), 34.83 (virtual t, CR,PCy , J ) 10.37 Hz),
3
3