Conversion of benzaldehyde imines into isocyanides at a low-valent molybdenum center. Preparation and reactivities of isocyanide-dinitrogen complexes trans-[Mo(RNC)(N2)(Ph2PCH2CH 2PPh2)2] (R = Aryl, Alkyl)

Article abstract of DOI:10.1021/om9904605

The molybdenum dinitrogen complex trans-[Mo(N₂)₂(dppe)₂] (1; dppe = Ph₂PCH₂CH₂PPh₂) reacts with benzaldehyde imines PhCH=NR (R = Ph, C₆H₄Me-p, C₆H₄OMe-P, C₆H₄F-p, C₆H₄-NMe₂-p, Buⁿ, Prⁱ, CH₂Ph) in benzene at reflux to give a series of isocyanide-dinitrogen complexes trans-[Mo(RNC)(N₂)(dppe)₂] (7) with the concurrent formation of benzene. The structure of 7a (R = Ph) has been determined by X-ray crystallography. Treatment of 7a and 7f (R = Buⁿ) with CO (1 atm) or p-MeOC₆H₄CN results in the replacement of the coordinated N₂ by these ligands, affording trans-[Mo(RNC)(L)(dppe)₂] (L = CO (9), p-MeOC₆H₄CN (10)). The complex containing two different isocyanides trans-[Mo(PhNC)-(Bu^tNC)(dppe)²] was obtained analogously from 7a and Bu^tNC. On the other hand, when benzene or toluene solutions of 7a and 7e (R = C₆H₄NMe₂-p) were first heated under Ar up to 80-90°C for a short period to dissociate the coordinated N₂ and then treated with H₂ at room temperature, dihydrogen complexes trans-[Mo(RNC)(η²-H₂)(dppe)₂] (13) were produced. The X-ray analyses have revealed the detailed structures for 9a (R = Ph), 10a (R = Ph), and 13e (R = C₆H₄NMe₂-P) along with the bis(isocyanide) complex trans-[Mo(PhNC)₂(dppe)₂].

Full text of DOI:10.1021/om9904605

Organometallics 1999, 18, 4165-4173
4165
Con ver sion of Ben za ld eh yd e Im in es in to Isocya n id es a t a
Low -Va len t Molybd en u m Cen ter . P r ep a r a tion a n d
Rea ctivities of Isocya n id e-Din itr ogen Com p lexes
tr a n s-[Mo(RNC)(N2)(P h 2P CH2CH2P P h 2)2] (R ) Ar yl,
Alk yl)1
Hidetake Seino,2a Chirima Arita,2a Daigo Nonokawa,2a Goh Nakamura,2a,b
Yuji Harada,2a,b Yasushi Mizobe,*,2a,c and Masanobu Hidai*,2b
Institute of Industrial Science, The University of Tokyo, Roppongi, Minato-ku, Tokyo 106-8558,
J apan, Department of Chemistry and Biotechnology, Graduate School of Engineering,
The University of Tokyo, Hongo, Tokyo 113-8656, J apan, and Institute for Molecular Science,
Myodaiji, Okazaki 444-8585, J apan
Received J une 14, 1999
The molybdenum dinitrogen complex trans-[Mo(N2)2(dppe)2] (1; dppe ) Ph2PCH2CH2PPh2)
reacts with benzaldehyde imines PhCHdNR (R ) Ph, C6H4Me-p, C6H4OMe-p, C6H4F-p, C6H4-
NMe2-p, Bun, Pri, CH2Ph) in benzene at reflux to give a series of isocyanide-dinitrogen
complexes trans-[Mo(RNC)(N2)(dppe)2] (7) with the concurrent formation of benzene. The
structure of 7a (R ) Ph) has been determined by X-ray crystallography. Treatment of 7a
and 7f (R ) Bun) with CO (1 atm) or p-MeOC6H4CN results in the replacement of the
coordinated N2 by these ligands, affording trans-[Mo(RNC)(L)(dppe)2] (L ) CO (9),
p-MeOC6H4CN (10)). The complex containing two different isocyanides trans-[Mo(PhNC)-
(ButNC)(dppe)2] was obtained analogously from 7a and ButNC. On the other hand, when
benzene or toluene solutions of 7a and 7e (R ) C6H4NMe2-p) were first heated under Ar up
to 80-90 °C for a short period to dissociate the coordinated N2 and then treated with H2 at
room temperature, dihydrogen complexes trans-[Mo(RNC)(η2-H2)(dppe)2] (13) were produced.
The X-ray analyses have revealed the detailed structures for 9a (R ) Ph), 10a (R ) Ph),
and 13e (R ) C6H4NMe2-p) along with the bis(isocyanide) complex trans-[Mo(PhNC)2(dppe)2].
In tr od u ction
organic compounds including aldehydes, formamides,
carboxylic acid esters, and alcohols,6 where 1 serves as
a versatile precursor to generate a highly reactive,
coordinatively unsaturated species by dissociating the
N2 ligands. Reactions of this type are exemplified by the
formation of trans-[Mo(CO)(DMF)(dppe)2] (3; DMF )
N,N-dimethylformamide) upon treatment of 1 with an
excess of DMF in benzene at reflux.7 Interestingly, the
DMF ligand in 3 is so labile that 3 is readily converted
to trans-[Mo(CO)(N2)(dppe)2] (4) and [Mo(CO)(dppe)2]
(5).6a From these carbonyl complexes as well as their
W analogues derived similarly from 2, a number of
carbonyl complexes of the types [M(CO)(L)(dppe)2] (M
) Mo, L ) Lewis bases, nitrile, olefin,6a,8 H2,9 hydrosi-
lanes;10 M ) Mo, W: L ) vinylidene11) and [M(CO)H-
Since the isolation of the first Mo dinitrogen complex
trans-[Mo(N2)2(dppe)2] (1; dppe ) Ph2PCH2CH2PPh2) in
this laboratory,3 intensive efforts have been devoted to
investigate reactivities of the N2 ligand in 1 and related
Mo and W complexes such as trans-[W(N2)2(dppe)2] (2)
and cis-[M(N2)2(PMe2Ph)4] (M ) Mo, W), aiming at
development of a new type of N2-fixing systems.4 Now
it has become apparent that these Mo and W dinitrogen
complexes are distinctive from other numerous N2
complexes hitherto reported in the reactivity of the
coordinated N2 which gives rise to the formation of
nitrogenous ligands and compounds under ambient
conditions.4,5
One of the other intriguing reactions promoted by 1
is the decarbonylation of various oxygen-containing
(1) Preparation and Properties of Molybdenum and Tungsten Dini-
trogen Complexes. 64. Part 63: see ref 15.
(2) (a) Institute of Industrial Science. (b) Department of Chemistry
and Biotechnology. (c) Institute for Molecular Science.
(3) (a) Hidai, M.; Tominari, K.; Uchida, Y.; Misono, A. J . Chem. Soc.,
Chem. Commun. 1969, 1392. (b) Hidai, M.; Tominari, K.; Uchida, Y.
J . Am. Chem. Soc. 1972, 94, 110.
(6) (a) Sato, M.; Tatsumi, T.; Kodama, T.; Hidai, M.; Uchida, T.;
Uchida, Y. J . Am. Chem. Soc. 1978, 100, 4447. (b) Tatsumi, T.;
Tominaga, H.; Hidai, M.; Uchida, Y. J . Organomet. Chem. 1981, 215,
67. (c) Tatsumi, T.; Tominaga, H.; Hidai, M.; Uchida, Y. J . Organomet.
Chem. 1981, 218, 177.
(7) Mizobe, Y.; Ishida, T.; Egawa, Y.; Ochi, K.; Tanase, T.; Hidai,
M. J . Coord. Chem. 1991, 23, 57.
(4) (a) Hidai, M.; Mizobe, Y. Chem. Rev. 1995, 95, 1115. (b) Hidai,
M.; Ishii, Y. Bull. Chem. Soc. J pn. 1996, 69, 819.
(5) (a) Richards, R. L. Coord. Chem. Rev. 1996, 154, 83. (b)
Bazhenova, T. A.; Shilov, A. E. Coord. Chem. Rev. 1995, 144, 69. (c)
Gambarotta, S. J . Organomet. Chem. 1995, 500, 117. (d) Leigh, G. J .
Acc. Chem. Res. 1992, 25, 177.
(8) Tatsumi, T.; Tominaga, H.; Hidai, M.; Uchida, Y. J . Organomet.
Chem. 1980, 199, 63.
(9) (a) Kubas, G. J .; Ryan, R. R.; Wrobleski, D. A. J . Am. Chem.
Soc. 1986, 108, 1339. (b) Kubas, G. J .; Burns, C. J .; Eckert, J .; J ohnson,
S. W.; Larson, A. C.; Vergamini, P. J .; Unkefer, C. J .; Khalsa, G. R.
K.; J ackson, S. A.; Eisenstein, O. J . Am. Chem. Soc. 1993, 115, 569.
10.1021/om9904605 CCC: $15.00 © 1999 American Chemical Society
Publication on Web 09/08/1999

4166 Organometallics, Vol. 18, No. 20, 1999
Seino et al.
Sch em e 1
7; however, use of the imines having the substituents
C6H4X-p (X ) CF3, COOEt) and But for R did not afford
the corresponding compounds. Due to the thermal
instability, 7h (R ) CH2Ph) once produced proved to
decompose rapidly under the conditions employed. Thus,
7h was obtained in satisfactory yield by refluxing the
reaction mixture for only 5 min. The conversion of
imines at the Mo center into the corresponding isocya-
nides appears to proceed via the scission of both the
C-Ph and C-H bonds on the benzylidene carbon. This
was confirmed by the concurrent formation of benzene
with 7a and 7b in the reaction of 1 with PhCHdNPh
or PhCHdNC6H4Me-p (0.71 and 0.73 mol of C6H6/mol
of 1, respectively).
Although the reactions of several aliphatic aldehyde
imines R′CHdNR (R ) alkyl, aryl; R′ ) alkyl) with 1
were attempted, complexes containing the RNC ligand
were not produced. Interestingly, from the reaction
mixtures of 1 with the imines that remained intact
under these conditions, a Mo(0) complex with a novel
tetradentate phosphine [Mo{o-C6H4(PPhCH2CH2PPh2)2}-
(dppe)] has been isolated in low yield. Characterization
and the improved method for preparation of this com-
plex from 1 by thermolysis have already been reported
separately.15 It is to be noted that the reactions of 1 with
various isocyanides give bis(isocyanide) complexes trans-
[Mo(RNC)2(dppe)2] (R ) alkyl, aryl) exclusively, and the
formation of the monosubstituted complexes 7 was not
observed.16
To our knowledge, little is known about the direct
transformation of imines into isocyanides. In contrast,
insertion of isocyanides into M-R bonds leading to η1-
or η2-iminoacyls is a well-precedented process.17 For
certain metal iminoacyl species, formation of imines by
succesive alkyl migration onto the iminoacyl carbon is
also known.18 The novel conversion of benzylidene-
anilines into isocyanides reported here might proceed
by following these processes in the reverse direction
(Scheme 2). Thus, oxidative addition of the benzylidene
C-H bond occurs initially at the coordinatively unsat-
urated Mo(0) center generated by thermolysis of 1,
giving a hydrido-iminoacyl intermediate [MoH{C(d
NR)Ph}(dppe)2]. Deinsertion of RNC from the iminoacyl
ligand and the following reductive elimination of ben-
(X)(dppe)2] (M ) Mo, W: X ) alkynyl;11 M ) W, X )
carbonate, carbamate,12 hydride13) have been prepared.
The mechanism for the formation of 3 from 1 involves
the cleavage of the aldehydic C-H bond in DMF at the
coordinatively unsaturated Mo center to give a hydrido-
carbamoyl species followed by the elimination of di-
methylamine (Scheme 1). This has been verified by the
isolation of [WH(η2-CONMe2)(dppe)2] (6) from the reac-
tion of 2 with DMF under controlled conditions. As
expected, when heated in benzene in the presence of
DMF, 6 is converted to trans-[W(CO)(DMF)(dppe)2] with
concurrent formation of HNMe2.13
Now the study has been extended to the reactions of
1 with benzaldehyde imines PhCHdNR (R ) aryl, alkyl)
instead of aldehydic compounds, and we have found that
unprecedented conversion of the imines into isocyanides
takes place at the Mo center to give a series of isocya-
nide-dinitrogen complexes trans-[Mo(RNC)(N2)(dppe)2]
(7). In this paper, details of the syntheses and charac-
terization of 7 are described, together with the reactivi-
ties of 7 toward a series of neutral ligands including CO,
nitriles, isocyanides, and H2. A part of this work has
been reported recently as a communication.14
Resu lts a n d Discu ssion
P r ep a r a t ion of Isocya n id e-Din it r ogen Com -
p lexes 7. When reacted with a range of PhCHdNR in
benzene at reflux for 2 h, the dinitrogen complex 1
afforded 7 in moderate yields (eq 1). Employment of the
(10) (a) Luo, X.-L.; Kubas, G. J .; Bryan, J . C.; Burns, C. J .; Unkefer,
C. J . J . Am. Chem. Soc. 1994, 116, 10312. (b) Luo, X.-L.; Kubas, G. J .;
Burns, C. J .; Bryan, J . C.; Unkefer, C. J . J . Am. Chem. Soc. 1995, 117,
1159.
(11) Nakamura, G.; Harada, Y.; Mizobe, Y.; Hidai, M. Bull. Chem.
Soc. J pn. 1996, 69, 3305.
(12) Ishida, T.; Hayashi, T.; Mizobe, Y.; Hidai, M. Inorg. Chem. 1992,
31, 4481.
(13) Ishida, T.; Mizobe, Y.; Tanase, T.; Hidai, M. J . Organomet.
Chem. 1991, 409, 355.
(14) Nakamura, G.; Harada, Y.; Arita, C.; Seino, H.; Mizobe, Y.;
Hidai, M. Organometallics 1998, 17, 1010.
(15) Arita, C.; Seino, H.; Mizobe, Y.; Hidai, M. Chem. Lett. 1999,
611.
(16) (a) Chatt, J .; Elson, C. M.; Pombeiro, A. J . L.; Richards, R. L.;
Royston, G. H. D. J . Chem. Soc., Dalton Trans. 1978, 165. (b) Pombeiro,
A. J . L.; Pickett, C. J .; Richards, R. L.; Sangokoya, S. A. J . Organomet.
Chem. 1980, 202, C15. (c) Pombeiro, A. J . L.; Richards, R. L. Coord.
Chem. Rev. 1990, 104, 13.
(17) Durfee, L. D.; Rothwell, I. P. Chem. Rev. 1988, 88, 1059.
(18) (a) Durfee, L. D.; Fanwick, P. E.; Rothwell, I. P.; Folting, K.;
Huffman, J . C. J . Am. Chem. Soc. 1987, 109, 4720. (b) Koschmieder,
S. U.; Hussain-Bates, B.; Hursthouse, M. B.; Wilkinson, G. J . Chem.
Soc., Dalton Trans. 1991, 2785. (c) La¨ı, R.; Desbois, O.; Zamkotsian,
F.; Faure, R.; Feneau-Dupont, J .; Declercq, J .-P. Organometallics 1995,
14, 2145. (d) Ca´mpora, J .; Buchwald, S. L.; Gutie´rrez-Puebla, E.;
Monge, A. Organometallics 1995, 14, 2039.
imines with R ) C6H4X-p (X ) H, Me, OMe, F, NMe2),
Bun, Pri, and CH2Ph gave the well-defined complexes

Conversion of Benzaldehyde Imines into Isocyanides
Organometallics, Vol. 18, No. 20, 1999 4167
Sch em e 2
zene affords [Mo(CNR)(dppe)2] (8), which rapidly binds
N2 to yield 7. Many attempts to isolate or detect 8 were
carried out, but failed.
Since the hydrido-carbamoyl intermediate 6 was able
to be isolated only for W in the related decarbonylation
reaction of DMF (Scheme 1), W complex 2 was allowed
to react with benzaldehyde imines under the analogous
conditions. However, neither the isocyanide-dinitrogen
complexes nor the hydrido-iminoacyl complexes were
obtained.
Since a variety of benzaldehyde imines are readily
available, the reactions reported here are attractive as
a route to isocyanides. However, the reaction proceeded
only stoichiometrically, and the liberation of free iso-
cyanides was not observed in the reactions with an
excess amount of benzaldehyde imines.
Ch a r a cter iza tion of 7. The structure of 7a has been
determined in detail by single-crystal X-ray analysis.
The ORTEP drawing is shown in Figure 1, while the
important bond lengths and angles are listed in Table
1. Complex 7a has a slightly distorted octahedral
structure with mutually trans PhNC and N2 ligands
bound to the Mo center in an end-on fashion. In the
PhNC ligand, the Mo-C(1)-N(1) linkage is almost
linear (176.7(3)°), while the C(1)-N(1)-C(2) bond is
slightly bent, with an angle of 167.4(4)°. The C(1)-N(1)
bond length at 1.179(4) Å is unexceptional for the
isocyanide ligand of this coordination mode. With re-
spect to the N2 ligand, the Mo-N(2)-N(3) linkage is
nearly linear (177.1(3)°), and the N(2)-N(3) distance at
1.102(3) Å is comparable to those in free N2 (1.0976(2)
Å)19 and 4 (1.09(2) Å).6a
Spectroscopic and analytical data for 7a are in good
agrement with the solid-state structure. Thus, the IR
spectrum shows two intense bands at 2049 and 1910
cm-1 assignable to ν(NN) of the coordinated N2 and ν-
(NC) of the PhNC ligand, respectively, while the 31P-
{1H} NMR spectrum exhibits one singlet at δ 68.9 due
to the two dppe ligands constituting the basal plane of
the octahedral structure. The other new complexes 7b-
7h show the analogous spectral features, indicating that
the structures are essentially identical.20
F igu r e 1. ORTEP diagram of 7a . Hydrogen atoms are
omitted for clarity.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in 7a
(a) Bond Length
Mo-P(1)
Mo-P(3)
Mo-N(2)
N(1)-C(1)
N(2)-N(3)
2.4548(9)
2.4544(9)
2.102(3)
1.179(4)
1.102(3)
Mo-P(2)
Mo-P(4)
Mo-C(1)
N(1)-C(2)
2.4491(9)
2.4481(9)
1.992(3)
1.388(4)
(b) Bond Angle
P(1)-Mo-P(2)
P(1)-Mo-P(4)
P(1)-Mo-C(1)
P(2)-Mo-P(4)
P(2)-Mo-C(1)
P(3)-Mo-N(2)
P(4)-Mo-N(2)
N(2)-Mo-C(1)
Mo-N(2)-N(3)
79.91(3)
102.74(3)
89.90(9)
172.62(3)
86.71(9)
87.86(7)
89.80(8)
174.9(1)
177.1(3)
P(1)-Mo-P(3)
P(1)-Mo-N(2)
P(2)-Mo-P(3)
P(2)-Mo-N(2)
P(3)-Mo-P(4)
P(3)-Mo-C(1)
P(4)-Mo-C(1)
C(1)-N(1)-C(2)
Mo-C(1)-N(1)
174.12(3)
87.61(7)
96.97(3)
97.22(8)
80.97(3)
94.91(9)
86.41(9)
167.4(4)
176.7(3)
trans to the N2 is CO,6a N2,3 nitriles,21 or isocyanides
coordinated to the Mo(0) center in an end-on manner.
Comparison of the IR data for these complexes provides
the order of the ν(NN) values decreasing as L ) CO
(2128 cm-1) > PhNC (2049 cm-1) > N2 (2020sym
,
1970asym cm-1) > p-MeOC6H4CN (1946 cm-1). Force
constants calculated from these ν(NN) values are 18.7,
17.3, 16.4, and 15.6 mdyn/Å, respectively.22 This indi-
cates that the π-acidity of L decreases according to this
order, which results in the increase in the net π-donat-
ing nature of the {Mo(L)(dppe)2} moiety toward the
antibonding orbitals of the N2 ligand.
(20) The X-ray analyses have also been undertaken for 7c, 7f, and
7g. Although the refinements were not completed to the satisfactory
level, the preliminary results have clearly demonstrated that the
structures of these three complexes are essentially analogous to that
of 7a . See Experimental Section.
Now a series of the N2 complexes of the type trans-
[Mo(L)(N2)(dppe)2] are available, where the ligand L
(21) Tatsumi, T.; Hidai, M.; Uchida, Y. Inorg. Chem. 1975, 14, 2530.
(22) (a) Lazarowych, N. J .; Morris, R. H.; Ressner, J . M. Inorg. Chem.
1986, 25, 3926. (b) Morris, R. H.; Earl, K. A.; Luck, R. L.; Lazarowych,
N. J .; Sella, A. Inorg. Chem. 1987, 26, 2674, and references therein.
(19) (a) Wilkinson, P. G.; Houk, N. B. J . Chem. Phys. 1956, 24, 528.
(b) Gordon, A. J .; Ford, R. A. The Chemist’s Companion; J ohn Wiley &
Sons: New York, 1972; p 107.

4168 Organometallics, Vol. 18, No. 20, 1999
Seino et al.
The ν(NN) value (2049 cm-1) is considerably lower
than that of free N2 (2331 cm-1) but still higher than
the parent N2 complex 1 (2020 and 1970 cm-1).3 Thus,
the N2 ligand in 7a is so labile as to be converted readily
into the related Mo(0) isocyanide complexes trans-[Mo-
(PhNC)(L)(dppe)2] (L ) CO (9a ), p-MeOC6H4CN (10a ),
and ButNC (11)).
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in 9a , 10a , a n d 12
9a
(a) Bond Length
Mo-P(1)
Mo-P(3)
Mo-C(1)
O-C(8)
2.429(1)
2.434(1)
2.072(4)
1.086(4)
1.407(5)
Mo-P(2)
Mo-P(4)
Mo-C(8)
N(1)-C(1)
2.439(1)
2.422(1)
2.017(5)
1.099(4)
P r ep a r a tion a n d Ch a r a cter iza tion of tr a n s-[Mo-
(RNC)(CO)(dppe)2] (9), tr a n s-[Mo(RNC)(p-MeOC6H4-
CN)(d p p e)2] (10), a n d tr a n s-[Mo(P h NC)(Bu tNC)-
(d p p e)2] (11). When 7a suspended in THF was treated
with CO at room temperature, an isocyanide-carbonyl
complex 9a was readily obtained in excellent yield.
Although the reaction of 7f with CO appears to proceed
more slowly, 9f (R ) Bun) was able to be isolated in
satisfactory yield by treatment of a benzene solution of
7f with CO at 50 °C. Reactions of 7a or 7f with ca. 2
equiv of p-MeOC6H4CN in benzene at room temperature
also resulted in the replacement of the N2 ligand by the
nitrile to give isocyanide-nitrile complexes 10 in high
yields. Detailed structures of 9a and 10a have been
determined by X-ray analyses as described below. On
the other hand, the reaction of 7a with an equimolar
amount of ButNC at room temperature gave 11, which
was characterized by the spectroscopic and microana-
lytical data. This finding indicates that 7 can serve as
the versatile precursor for preparing a wide range of
Mo complexes containing two different isocyanides
trans-[Mo(RNC)(R′NC)(dppe)2]. The reactions forming
9-11 are summarized in eq 2.
N(1)-C(2)
(b) Bond Angle
P(1)-Mo-P(2)
P(1)-Mo-P(4)
P(1)-Mo-C(8)
P(2)-Mo-P(4)
P(2)-Mo-C(8)
P(3)-Mo-C(1)
P(4)-Mo-C(1)
C(1)-Mo-C(8)
Mo-C(1)-N(1)
80.31(4)
101.27(4)
90.8(1)
178.04(4)
91.1(1)
89.9(1)
89.9(1)
175.9(2)
179.2(4)
P(1)-Mo-P(3)
P(1)-Mo-C(1)
P(2)-Mo-P(3)
P(2)-Mo-C(1)
P(3)-Mo-P(4)
P(3)-Mo-C(8)
P(4)-Mo-C(8)
C(1)-N(1)-C(2)
Mo-C(8)-O
176.10(4)
86.4(1)
98.34(4)
91.4(1)
80.16(4)
92.9(1)
87.7(1)
177.6(3)
177.9(4)
10a
(a) Bond Length
Mo-P(1)
Mo-P(3)
Mo-N(1)
N(1)-C(1)
N(2)-C(8)
2.464(1)
Mo-P(2)
Mo-P(4)
Mo-C(1)
N(1)-C(2)
2.457(1)
2.432(1)
1.964(3)
1.386(4)
2.414(1)
2.160(3)
1.217(4)
1.153(4)
(b) Bond Angle
P(1)-Mo-P(2)
P(1)-Mo-P(4)
P(1)-Mo-C(1)
P(2)-Mo-P(4)
P(2)-Mo-C(1)
P(3)-Mo-N(2)
P(4)-Mo-N(2)
N(2)-Mo-C(1)
Mo-N(2)-C(8)
N(2)-C(8)-C(9)
80.09(4)
99.14(4)
97.9(1)
177.24(4)
98.0(1)
89.88(8)
92.56(8)
173.6(1)
179.3(3)
173.4(4)
P(1)-Mo-P(3)
P(1)-Mo-N(2)
P(2)-Mo-P(3)
P(2)-Mo-N(2)
P(3)-Mo-P(4)
P(3)-Mo-C(1)
P(4)-Mo-C(1)
C(1)-N(1)-C(2)
Mo-C(1)-N(1)
178.09(4)
88.22(8)
99.70(4)
84.78(8)
80.98(4)
84.0(1)
84.8(1)
149.8(4)
168.9(3)
12
(a) Bond Length
Mo-P(1)
Mo-C(1)
N-C(2)
2.461(2)
2.031(6)
1.399(7)
Mo-P(2)
N-C(1)
2.445(2)
1.171(6)
(b) Bond Angle
P(1)-Mo-P(1)*
P(1)-Mo-P(2)*
P(1)-Mo-C(1)*
P(2)-Mo-C(1)
C(1)-Mo-C(1)*
Mo-C(1)-N
101.90(8)
175.69(6)
89.4(2)
87.2(2)
177.2(3)
176.5(5)
P(1)-Mo-P(2)
P(1)-Mo-C(1)
P(2)-Mo-P(2)*
P(2)-Mo-C(1)*
C(1)-N-C(2)
80.64(5)
88.9(2)
97.04(8)
94.7(2)
Table 2 lists the selected bond distances and angles
in 9a and 10a determined by X-ray analyses. Since the
attempt to prepare high-quality single crystals was
unsuccessful for 11, a single crystal of trans-[Mo-
(PhNC)2(dppe)2] (12)16a was prepared and subjected to
the X-ray diffraction study, whose results are also shown
in Table 2. As depicted in Figures 2-4, structures of
9a , 10a , and 12, respectively, are well comparable to
that of 7a , viz., the CO, p-MeOC6H4CN, and PhNC
ligands occupy the trans position of the PhNC ligand
in the octahedral coordination sphere. The Mo-C(8)-
O, Mo-N(2)-C(8), and Mo-C(1)-N linkages in each
complexes are linear with angles of 177.9(4)°, 179.3(3)°,
and 176.5(5)°, while the C(8)-O, N(2)-C(8), and C(1)-N
bond distances in these moieties at 1.086(4), 1.153(4),
and 1.171(6) Å, respectively, are unexceptional for these
molecules of this coordination mode.
172.7(7)
accordingly the Mo-C(1) and N(1)-C(2) bond distances
decrease as 9a > 12 > 7a > 10a . This finding is
interpreted in terms of the net π-donating ability of the
{Mo(L)(dppe)2} moieties toward the PhNC ligand, in-
creasing in the order L ) CO < PhNC < N2
<
p-MeOC6H4CN, which is in good agreement with the
results obtained for a series of dinitrogen complexes
trans-[Mo(N2)(L)(dppe)2] (vide supra). In contrast to
relatively small differences in the bond angles of the
Mo-C(1)-N(1) arrays (179.2(4)-168.9(3)°), those of the
C(1)-N(1)-C(2) linkages change significantly, from
177.6(5)° in 9a to 149.8(4)° in 10a . In general, bent
C-N-C linkages are found in the aliphatic isocyanides
bound to the zerovalent metal center having no π-ac-
cepting ligands, where the electron density remains
localized on the N atom in the NC group and the
C-N-C linkage tends to be bent due to the pairing
effects of electrons,23 e.g., the average C-N-C angle of
130° for the two equatorial isocyanide ligands in the
trigonal bipyramidal [Ru(CNBut)4(PPh3)] and that of
For the PhNC ligands in trans-[Mo(PhNC)(L)(dppe)2],
important bonding parameters associated with 9a , 10a ,
and 12 are summarized in Table 3, together with those
of 7a for comparison. With respect to the bond lengths,
Table 3 clearly shows that the C(1)-N(1) bonds are
elongated, following the order 9a < 12 < 7a < 10a , and

Conversion of Benzaldehyde Imines into Isocyanides
Organometallics, Vol. 18, No. 20, 1999 4169
F igu r e 2. ORTEP diagram of 9a . Hydrogen atoms are
F igu r e 4. ORTEP diagram of 12. Hydrogen atoms are
omitted for clarity.
omitted for clarity.
Ta ble 3. Selected Bon d in g P a r a m eter s in
tr a n s-[Mo(P h NC)(L)(d p p e)2]
9a
CO
12
7a
10a
L
PhNC
N2
p-MeOC6H4CN
(a) Bond Length (Å)
Mo-C(1)
C(1)-N(1)
N(1)-C(2)
2.072(4) 2.031(6) 1.992(3) 1.964(3)
1.099(4) 1.171(6) 1.179(4) 1.217(4)
1.407(5) 1.399(7) 1.388(4) 1.386(4)
(b) Bond Angle (deg)
Mo-C(1)-N(1)
179.2(4) 176.5(5) 176.7(3) 168.9(3)
C(1)-N(1)-C(2) 177.6(5) 172.7(7) 167.4(4) 149.8(4)
N atom into the aromatic rings; cis-[W(CNC6H4NC)2-
(dppe)2] provides the rare example containing the bent
aryl isocyanide ligands with C-N-C angles of 136.8-
(11)° and 141.4(8)°.23 This tendency is consistent with
the finding that the C-N-C angle in trans-[Mo(PhNC)2-
(dppe)2] (172.9(8)°) is larger than that in trans-[Mo-
(MeNC)2(dppe)2] (156(1)°).25 In this respect, the sub-
stantially bent C-N-C angle of 149.8(4)° observed in
the PhNC complex 10a is noteworthy.
All of the 31P{1H} NMR spectra for 9-11 show one
singlet assignable to the dppe ligands, indicating that
all have the trans structure, demonstrated by the X-ray
analyses for 9a and 10a . In the IR spectra appear the
intense bands characteristic of the C-O and C-N
multiple bonds in the carbonyl, nitrile, and isocyanide
ligands. Splitting of the ν(NC) band in 9a (2017 and
1991 cm-1) might be explained by the packing effect as
observed previously for 4 and its W analogue.6a,13 By
using the ν(NC) frequencies observed for a series of
trans-[Mo(PhNC)(L)(dppe)2], force constants of the iso-
cyanide N-C multiple bonds may be calculated to be
15.3 (av), 14.4, 13.9, and 12.6 mdyn/Å for L ) CO,
F igu r e 3. ORTEP diagram of 10a . Hydrogen atoms are
omitted for clarity.
135° for the two bent isocyanide ligands in [Fe(CN-
But)5].24 On the other hand, significant C-N-C bending
hardly occurs for the aryl isocyanide ligands because of
their ability to delocalize the charge from the isocyanide
(23) Hu, C.; Hodgeman, W. C.; Bennett, D. W. Inorg. Chem. 1996,
35, 1621.
(24) Basset, J .-M.; Berry, D. E.; Barker, G. K.; Green, M.; Howard,
J . A. K.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1979, 1003.
(25) Chatt, J .; Pombeiro, A. J . L.; Richards, R. L.; Royston, G. H.
D.; Muir, K. W.; Walker, R. J . Chem. Soc., Chem. Commun. 1975, 708.

4170 Organometallics, Vol. 18, No. 20, 1999
Seino et al.
Sch em e 3
PhNC, N2, and p-MeOC6H4CN, respectively, and this
order is similar to that observed for the force constants
of the N-N bonds in trans-[Mo(N2)(L)(dppe)2] (vide
supra).
P r ep a r a tion a n d Ch a r a cter iza tion of tr a n s-[Mo-
(RNC)(η2-H2)(d p p e)2] (13). Activation of the H-H
bond on transition metal centers is of much interest,26
and the binding of H2 to the 16e species [M(CO)(R2-
PCH2CH2PR2)2] (M ) Mo, R ) aryl, alkyl; M ) W, R )
aryl) and [Mn(CO)(R2PCH2CH2PR2)2]+ (R ) alkyl, aryl)
has been investigated extensively. From these studies,
several η2-H2 complexes have already been isolated and
characterized in a well-defined manner, which include
trans-[Mo(CO)(η2-H2)(R2PCH2CH2PR2)2] (R
)
Ph,9
PhCH2, m-CH3C6H4CH227) and trans-[Mn(CO)(η2-H2)(R2-
PCH2CH2PR2)2]+ (R ) Et, Ph).28 In contrast, it has been
revealed that the reactions of Mo complexes containing
more electron-donating diphosphines under H2 afford
dihydride complexes [Mo(CO)H2(R2PCH2CH2PR2)2] (R
) Et, Bui).9b,29 The analogous electronic control has been
achieved by replacing the Mo atom with the more
electron-rich W, which results in the formation of
dihydride complex [W(CO)H2(Ph2PCH2CH2PPh2)2].13
Ta ble 4. T1 Va lu es for th e H2 Sign a l in
tr a n s-[Mo(CNR)(H2)(d p p e)2] (13)a
Now the reactions of 7 containing a readily replace-
able N2 ligand with H2 have been investigated to clarify
the interaction of H2 with the {Mo(RNC)(dppe)2} chro-
mophore. This will demonstrate for the first time the
effect of the ligand occupying the site trans to the H2
upon the bonding of the incorporated H2. In contrast to
the reactions with CO, nitriles, and isocyanides, initial
attempts to prepare [Mo(RNC)(H2)(dppe)2] through the
direct substitution of the N2 ligand in 7 by H2 (1 atm)
at room temperature or 50 °C were unsuccessful, since
most of 7 was recovered even after the prolonged
reaction time. However, when a toluene solution of 7a
was heated at 90 °C for 30 min or a benzene solution of
7e was refluxed for 30 min under Ar to dissociate the
N2 ligand and then the resultant black solutions pre-
sumably containing the five-coordinate complexes [Mo-
(RNC)(dppe)2] (8) were treated with H2 gas (1 atm), the
desired H2 complexes trans-[Mo(RNC)(η2-H2)(Ph2PCH2-
CH2PPh2)2] (13a , R ) Ph; 13e, R ) p-Me2NC6H4) could
be isolated in moderate yields (Scheme 3).
Since the N2 ligands in the isocyanide complexes 7
are bound to the Mo center more firmly than the N2 in
4 containing the more electron-withdrawing CO ligand,
removal of the N2 to give the reactive five-coordinate
species 8 probably requires more forcing conditions than
those for generating 5 from 4. This well correlates to
the previous findings that 5 is readily obtained by
bubbling Ar gas through a benzene solution of 4 at 50
°C for several minutes or degassing it in vacuo, whereas
the W analogue [W(CO)(dppe)2] (14) is isolable after
refluxing a benzene solution of trans-[W(CO)(N2)(dppe)2]
(15) under Ar, owing to the presence of the more
13a
T1 (ms)
13e
T1 (ms)
13f
T1 (ms)
temp (K)
δ
δ
δ
290
260
230
-4.8
b
21
17
-5.4
b
15
20
-5.9
20
15
17
a
400 MHz; toluene-d8 solutions. Inversion recovery method.
Data are unreliable due to much broadening of the signal.
b
electron-rich W center. The IR data of 4, 15, and 7
support this observation; the ν(NN) bands appear at
2110 and 2080 cm-1 for 4 and at 2070 and 2030 cm-1
for 15, indicating the presence of the stronger back-
donation to the N2 ligand in 15. The fact that the ν-
(NN) values observed for 7 are almost the same or lower
than those of 15 is consistent with the requirement of
the drastic conditions to generate 8.
Despite the repeated trials, characterization of 8 could
not be completed possibly due to its extreme sensitivity
to air and moisture. Thus, although dark brown crystals
obtained from the black solution produced after ther-
molysis of 7e showed the satisfactory analytical data
to be formulated as [Mo(p-Me2NC6H4NC)(dppe)2] (8e),
reliable spectral data were unable to be collected. As
observed for 5 and 14, solutions possibly containing 8
were treated with N2 to give 7 reversibly.
Taking into account the weaker π-acidity of the RNC
ligands than the CO ligand, 13 had been expected to
have dihydride ligands rather than a H2 ligand. How-
ever, the 1H NMR spectra for 13a and 13e both
exhibited broad signals at -4.8 and -5.2 ppm, which
are characteristic of the η2-H2 protons. As summarized
in Table 4, the T1 values in the range 15-21 ms at 230
and 260 K are comparable to 20 ms at 200 K of the fully
characterized dihydrogen complex trans-[Mo(CO)(η2-
H2)(dppe)2] (16),9 indicating unambiguously that these
can be identified as the η2-H2 complexes.26 Even for 13f
(R ) Bun), possibly having the more π-donating {Mo-
(BunNC)(dppe)2} moiety, the η2-H2 nature has been
demonstrated by the NMR data at 230, 260, and 290 K
as listed in Table 4, although isolation of the pure
(26) (a) Heinekey, D. M.; Oldham, W. J ., J r. Chem. Rev. 1993, 93,
913. (b) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789.
(c) J essop, P. G.; Morris, J . H. Coord. Chem. Rev. 1992, 121, 155. (d)
Kubas, G. J . Acc. Chem. Res. 1994, 27, 183.
(27) Luo, X.-L.; Kubas, G. J .; Burns, C. J .; Eckert, J . Inorg. Chem.
1994, 33, 5219.
(28) (a) King, W. A.; Scott, B. L.; Eckert, J .; Kubas, G. J . Inorg.
Chem. 1999, 38, 1069. (b) King, W. A.; Luo, X.-L.; Scott, B. L.; Kubas,
G. J .; Zilm, K. W. J . Am. Chem. Soc. 1996, 118, 6782.
(29) Kubas, G. J .; Ryan, R. R.; Unkefer, C. J . J . Am. Chem. Soc.
1987, 109, 8113.

Conversion of Benzaldehyde Imines into Isocyanides
Organometallics, Vol. 18, No. 20, 1999 4171
the appearance of the ν(NN) band at 2048 and 2018
cm-1 for 7a and 7e, respectively.
It is interesting that the C(1)-N(1) bond in the
isocyanide ligand in 13e is fairly long at 1.213(4) Å and
the C(1)-N(1)-C(2) linkage is significantly bent with
an angle of 148.4(4)°, which reflect the quite weak
π-accepting nature of the η2-H2 ligand in this complex.
Considerably low ν(NC) frequencies observed for 13
(e.g., 13a , 1875 and 1817; 13e, 1891 and 1813 cm-1) also
arise from this electronic feature of the η2-H2 ligand.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were carried
out under an atmosphere of nitrogen except for those stated
otherwise. IR and NMR spectra were recorded on J ASCO FT/
IR-420 and J EOL EX-270 or LA-400 spectrometers. The
signals arising from the aromatic protons are omitted in the
1
following H NMR data. Elemental analyses were done with
a Perkin-Elmer 2400 series II CHN analyzer. Amounts of
solvating molecules in the crystals were determined by the
X-ray crystallography, NMR measurement, and/or GLC analy-
sis. Complexes 132 and 1216a were prepared according to the
literature methods.
P r ep a r a tion of tr a n s-[Mo(RNC)(N2)(d p p e)2] (7) fr om
Ben za ld eh yd e Im in es. P r ep a r a tion of 7a (R ) P h ).
Complex 1 (166 mg, 0.175 mmol) and PhCHdNPh (33 mg, 0.18
mol) were dissolved in benzene (2 mL), and the solution was
heated at reflux for 2 h. After cooling, ether was layered on
the resulting dark red solution. Dark red crystals of 7a ‚2C6H6
deposited, which were filtered off and dried in vacuo (129 mg,
62%). Anal. Calcd for C71H65N3MoP4: C, 72.26; H, 5.55; N, 3.56.
Found: C, 71.99; H, 5.70; N, 3.23. IR (KBr): ν(NN), 2049; ν-
F igu r e 5. ORTEP diagram of 13e. Hydrogen atoms are
omitted for clarity.
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in 13e
(a) Bond Length
1
(NC), 1910 cm-1. H NMR (C6D6): δ 2.35 (br, 8H, PCH2). 31P-
Mo-P(1)
Mo-P(3)
Mo-C(1)
N(1)-C(2)
2.454(1)
2.410(1)
1.969(4)
1.385(4)
Mo-P(2)
Mo-P(4)
N(1)-C(1)
2.443(1)
2.431(1)
1.213(4)
{1H} NMR (C6D6): δ 68.9 (s).
P r ep a r a tion of 7b (R ) C6H4Me-p). This compound was
obtained from 1 (166 mg, 0.175 mmol) and PhCHdNC6H4Me-p
(68 mg, 0.35 mmol) by essentially the same procedure as that
for preparing 7a except that the red crystals of 7b‚C6H6 were
isolated by addition of hexane to the product solution. Yield:
52%. Anal. Calcd for C66H61N3MoP4: C, 71.03; H, 5.51; N, 3.77.
Found: C, 71.02; H, 5.73; N, 3.23. IR (KBr): ν(NN), 2053; ν-
(NC), 1914 cm-1. 1H NMR (C6D6): δ 2.11 (s, 3H, Me), 2.40 (br,
8H, PCH2). 31P{1H} NMR (C6D6): δ 69.1 (s).
(b) Bond Angle
P(1)-Mo-P(2)
P(1)-Mo-P(4)
P(2)-Mo-P(3)
P(2)-Mo-C(1)
P(3)-Mo-C(1)
C(1)-N(1)-C(2)
80.41(3)
99.25(3)
99.05(3)
91.1(1)
82.63(10)
148.4(4)
P(1)-Mo-P(3)
P(1)-Mo-C(1)
P(2)-Mo-P(4)
P(3)-Mo-P(4)
P(4)-Mo-C(1)
Mo-C(1)-N(1)
179.22(4)
96.82(10)
177.84(4)
81.27(3)
86.8(1)
171.2(3)
The following compounds 7c-7g were obtained similarly,
except that 1 (0.175 mmol) was reacted with a larger excess
of the imine (1.75 mmol).
compound showing satisfactory microanalysis data was
unsuccessful.
7c‚3/2C6H6 (R ) C6H4OMe-p): Red crystals, yield 46%.
Anal. Calcd for C69H64N3MoOP4: C, 70.77; H, 5.51; N, 3.59.
Found: C, 70.12; H, 5.74; N, 3.11. IR (KBr): ν(NN), 2054; ν-
The X-ray analysis was carried out for 13e, whose
results are shown in Figure 5 and Table 5. Although
the η2-H2 moiety could not be located, 13e has a common
octahedral structure and the η2-H2 ligand is inferred to
be present at the site trans to the isocyanide. The
structure clarified here is well comparable to that of
fully characterized 16.9 By contrast, seven-coordinate
dihydride complexes [W(CO)H2(dppe)2]13 and [Mo(CO)-
H2(Et2PCH2CH2PEt2)2]29 tend to have a pentagonal
bipyramidal geometry. Morris et al. claimed previously
that treatment of the octahedral d6 N2 complexes
exhibiting a ν(NN) band in the region 2060-2150 cm-1
with H2 results in the formation of stable η2-H2 com-
plexes.30,31 It is noteworthy that 13a and 13e have
apparently the well-characterized η2-H2 ligand despite
(NC), 1908 cm-1 1H NMR (C6D6): δ 3.31 (s, 3H, OMe), 2.41
.
(br, 8H, PCH2). 31P{1H} NMR (C6D6): δ 69.0 (s). Repeated
purification did not improve the analysis data.
7d ‚1/2C6H6 (R ) C6H4F -p): Orange crystals, yield 35%.
Anal. Calcd for C62H55N3FMoP4: C, 68.89; H, 5.13; N, 3.89.
Found: C, 68.23; H, 5.43; N, 3.58. IR (KBr): ν(NN), 2054; ν-
1
(NC), 1907 cm-1. H NMR (C6D6): δ 2.3-2.5 (m, 8H, PCH2).
31P{1H} NMR (C6D6): δ 68.7 (s). Repeated purification did not
result in the better carbon analysis.
7e (R ) C6H4NMe2-p): Orange crystals, yield 38%. Anal.
Calcd for C61H58N4MoP4: C, 68.67; H, 5.48; N, 5.25. Found:
C, 68.70; H, 5.68; N, 5.22. IR (KBr): ν(NN), 2018; ν(NC), 1929
cm-1 1H NMR (C6D6): δ 2.51 (s, 6H, NMe), 2.41 (br, 8H,
.
PCH2). 31P{1H} NMR (C6D6): δ 69.1 (s).
7f (R ) Bu n ): Orange crystals, yield 56%. Anal. Calcd for
(30) Morris, R. H.; Earl, K. A.; Luck, R. L.; Lazarowych, N. J .; Sella,
A. Inorg. Chem. 1987, 26, 2674.
(31) In the IR spectrum of 7f, a very strong and broad band centered
at 1963 cm-1 appeared. The NN and NC stretching bands are probably
overlapping, and it was impossible to assign the correct ν(NN)
frequency.
C
57H57N3MoP4: C, 68.19; H, 5.72; N, 4.19. Found: C, 68.63;
1
H, 5.60; N, 4.02. IR (KBr): ν(NN) and ν(NC), 1964 cm-1. H
(32) Hussain, W.; Leigh, G. J .; Mohd.-Ali, H.; Pickett, C. J .; Rankin,
D. A. J . Chem. Soc., Dalton Trans. 1984, 1703.

4172 Organometallics, Vol. 18, No. 20, 1999
Seino et al.
NMR (C6D6): δ 0.83 (t, J ) 7.1 Hz, 3H, CH2Me), 1.0-1.2 (m,
4H, CH2CH2Me), 2.90 (t, J ) 6.5 Hz, 2H, NCH2), 2.2-2.5 (br
m, 8H, PCH2). 31P{1H} NMR (C6D6): δ 70.0 (s).
7g (R ) P r i): Orange-red crystals, yield 60%. Anal. Calcd
for C56H55N3MoP4: C, 67.95; H, 5.60; N, 4.24. Found: C, 67.80;
H, 5.61; N, 3.96. IR (KBr): ν(NN), 2035; ν(NC), 1929 cm-1. 1H
NMR (C6D6): δ 0.67 (d, J ) 6.4 Hz, 6H, Me), 3.37 (sep, J )
6.4 Hz, 1H, NCH), 2.3-2.5 (m, 8H, PCH2). 31P{1H} NMR
(C6D6): δ 70.0 (s).
P r ep a r a tion of tr a n s-[Mo(P h NC)(Bu tNC)(d p p e)2] (11).
A mixture of 7a ‚2C6H6 (99 mg, 0.097 mmol) and ButNC (11
µL, 0.098 mmol) in benzene (5 mL) was stirred at room
temperature for 24 h. Crystallization from benzene/hexane
afforded 11‚C6H6 (57 mg, 51% yield) as dark brown crystals.
Anal. Calcd for C70H68N2MoP4: C, 72.66; H, 5.92; N, 2.42.
Found: C, 72.50; H, 5.87; N, 2.60. IR (KBr): ν(NC), 2010 (But-
NC) and 1880 (PhNC) cm-1 1H NMR (C6D6): δ 0.64 (s, 9H,
.
But), 2.2-2.5 (m, 8H, PCH2). 31P{1H} NMR (C6D6): δ 73.3 (s).
P r ep a r a tion of [Mo(p-Me2NC6H4NC)(d p p e)2] (8e). A
benzene solution (5 mL) of 7e (108 mg, 0.101 mmol) was
refluxed under Ar for 40 min to give a yellow-black solution.
After cooling to room temperature, hexane (10 mL) was added
and the mixture was filtered. Addition of hexane (12 mL) to
the concentrated filtrate (ca. 5 mL) afforded 8e as dark brown
crystals (40 mg, 38% yield), which were separated manually
from undesired byproducts deposited as orange crystals. Anal.
Calcd for C61H58N2MoP4: C, 70.52; H, 5.63; N, 2.70. Found:
C, 70.38; H, 5.85; N, 2.89.
P r ep a r a tion of tr a n s-[Mo(P h NC)(η2-H2)(d p p e)2] (13a ).
A toluene solution (4.5 mL) of 7a ‚2C6H6 (99 mg, 0.097 mmol)
was heated at 90 °C under Ar for 30 min. After cooling, the
resultant yellowish black solution was degassed and then kept
under H2 (1 atm). The solution gradually turned to orange-
red, from which red crystals of 13a ‚C6H5CH3 precipitated (46
mg, 43% yield). Addition of hexane to the filtrate gave the
second crop (26 mg, 25% yield). Anal. Calcd for C66H63NMoP4:
C, 72.72; H, 5.83; N, 1.28. Found: C, 72.32; H, 5.74; N, 1.58.
IR (KBr): ν(NC), 1875 and 1817 cm-1. 1H NMR (C6D6): δ -4.8
(br, 2H, H2), 2.15 (s, 3H, C6H5CH3), 2.2-2.4 (m, 8H, PCH2).
31P{1H} NMR (C6D6): δ 74.5 (s).
7h ‚C6H6 (R ) CH2P h ). A mixture of 1 (167 mg, 0.176 mmol)
and PhCHdNCH2Ph (166 µL, 0.882 mmol) in benzene (3 mL)
was refluxed for 5 min, and the resultant dark green solution
was filtered. Addition of hexane (10 mL) to the filtrate gave
orange-red crystals of 7h ‚C6H6 (111 mg, 56%). Anal. Calcd for
C66H61N3MoP4: C, 71.03; H, 5.51; N, 3.77. Found: C, 70.75;
H, 5.47; N, 3.68. IR (KBr): ν(NN), 1972; ν(NC), 1933 cm-1. 1H
NMR (C6D6): δ 4.13 (s, 2H, NCH2), 2.3-2.5 (m, 8H, PCH2).
31P{1H} NMR (C6D6): δ 69.9 (s).
Qu a n tita tive An a lysis of th e Ben zen e P r od u ced in th e
Rea ction F or m in g 7. A mixture of 1 (104 mg, 0.110 mmol)
and PhCHdNPh (22.7 mg, 0.125 mmol) in toluene (1 mL) was
refluxed under N2 for 1 h. After cooling to room temperature,
the resultant solution was subjected to the GLC analysis using
a Shimadzu GC-14A Gas Chromatograph equipped with a 25
m × 0.25 mm fused silica capillary column, which showed the
formation of 0.71 mol of benzene per Mo atom. Formation of
benzene (0.73 mol/Mo atom) from the reaction of 1 with
PhCHdNC6H4Me-p in p-xylene was confirmed by the analo-
gous method.
P r ep a r a t ion of tr a n s-[Mo(P h NC)(CO)(d p p e)2] (9a ).
Through a suspension of 7a ‚2C6H6 (114 mg, 0.0966 mmol) in
THF (5 mL) was passed CO gas for a few minutes, and the
mixture was stirred under CO for 25 h at room temperature.
The resultant orange solid was filtered off, washed with THF
and ether, and then dried in vacuo (57 mg, 58%). Addition of
hexane (10 mL) to the combined THF filtrate afforded the
second crop of 9a as orange prisms (18 mg, 18%). Anal. Calcd
for C60H53NMoOP4: C, 70.38; H, 5.22; N, 1.37. Found: C, 69.88;
H, 5.19; N, 1.53. IR (KBr): ν(NC), 2017 and 1991; ν(CO), 1812
P r ep a r a t ion of tr a n s-[Mo(p -Me2NC6H 4NC)(η2-H 2)-
(d p p e)2] (13e). A benzene solution (3 mL) of 7e (84 mg, 0.078
mmol) was refluxed under Ar for 30 min. Analogous treatment
of the resultant solution with H2 afforded 13e, which was
obtained as orange-red crystals by recrystallization from
benzene-hexane (60 mg, 74% yield). Anal. Calcd for C61H60N2-
MoP4: C, 70.38; H, 5.81; N, 2.69. Found: C, 70.01; H, 5.86; N,
1
2.67. IR (KBr): ν(NC), 1891 and 1813 cm-1. H NMR (C6D6):
cm-1 1H NMR (C6D6): δ 2.35 (br, 8H, PCH2). 31P{1H} NMR
.
(C6D6): δ 72.1 (s).
δ -5.2 (br, 2H, H2), 2.55 (s, 6H, NCH3), 2.3-2.6 (m, 8H, PCH2).
31P{1H} NMR (C6D6): δ 75.1 (s).
P r ep a r a tion of tr a n s-[Mo(Bu n NC)(η2-H2)(d p p e)2] (13f).
This complex was obtained from 7f by the same procedure as
that for 13e. However, the compound is always contaminated
by a small amount of byproduct(s), and satisfactory analysis
data were not available. Anal. Calcd for C57H59NMoP4: C,
70.01; H, 6.08; N, 1.43. Found: C, 69.27; H, 5.90; N, 1.61. IR
(KBr): ν(NC), 1800-1900 cm-1 (vbr). 1H NMR (C6D6): δ -5.9
(br, 2H, H2), 0.86 (t, J ) 7.4 Hz, 3H, CH3), 1.0-1.2 (m, 2H
each, NCH2CH2CH2), 2.94 (t, J ) 6.6 Hz, 2H, NCH2), 2.2-2.3
(m, 8H, PCH2). 31P{1H} NMR (C6D6): δ 76.3 (s).
P r ep a r a tion of tr a n s-[Mo(Bu n NC)(CO)(d p p e)2] (9f). A
benzene solution (15 mL) of 7f (307 mg, 0.306 mmol) was
stirred under CO at 50 °C for 3 h, and the resulting orange
mixture was filtered. Hexane was added to the concentrated
filtrate, affording 9f as orange crystals (190 mg, 62% yield).
Anal. Calcd for C58H57NMoOP4: C, 69.39; H, 5.72; N, 1.40.
Found: C, 68.75; H, 5.69; N, 1.66. IR (KBr): ν(NC), 2075; ν-
1
(CO), 1788 cm-1. H NMR (C6D6): δ 0.71 (t, J ) 6.4 Hz, 3H,
Me), 0.8-0.9 (m, 4H, MeCH2CH2), 2.40 (m, 2H, NCH2), 2.2-
2.3 (m, 8H, PCH2). 31P{1H} NMR (C6D6): δ 73.4 (s).
X-r a y Diffr a ction Stu d ies. Single crystals were sealed in
glass capillaries under N2 for 7a , 9a , 10a , and 12 or under Ar
for 13e, which were transferred to a Rigaku AFC7R diffrac-
tometer equipped with a graphite-monochromatized Mo KR
source. Diffraction studies were carried out at room temper-
ature. Orientation matrixes and unit cell parameters were
determined by least-squares treatment of 25 reflections with
35° < 2θ < 40°.The intensities of three check reflections were
monitored every 150 reflections during data collection, which
revealed no significant decay for all crystals. Intensity data
were corrected for Lorentz and polarization effects and for
absorption (ψ scans). Details of crystal and data collection
parameters are summarized in Table 6.
P r ep a r a t ion of tr a n s-[Mo(P h NC)(p -MeOC6H 4CN)-
(d p p e)2] (10a ). A mixture of 7a ‚2C6H6 (315 mg, 0.308 mmol)
and p-MeOC6H4CN (78 mg, 0.59 mmol) in benzene (17 mL)
was stirred at room temperature for 24 h. Addition of hexane
to the resultant solution gave dark brown prisms of 10a ‚1/
2C6H6 (290 mg, 84% yield). Anal. Calcd for C70H63N2MoOP4:
C, 71.98; H, 5.44; N, 2.40. Found: C, 71.93; H, 5.27; N, 2.24.
IR (KBr): ν(CNnitrile), 2171; ν(NCisocyanide), 1821 and 1715 cm-1
.
1H NMR (C6D6): δ 3.13 (s, 3H, OMe), 2.3-2.7 (m, 8H, PCH2).
31P{1H} NMR (C6D6): δ 70.2 (s).
P r ep a r a t ion of tr a n s-[Mo(Bu n NC)(p -MeOC6H 4CN)-
(d p p e)2] (10f). This complex was obtained similarly from 7f
and p-MeOC6H4CN as dark brown crystals in 78% yield. Anal.
Calcd for C65H64N2MoOP4: C, 70.39; H, 5.82; N, 2.53. Found:
C, 70.27; H, 5.85; N, 2.58. IR (KBr): ν(CNnitrile), 2154; ν-
Structure solution and refinements were carried out by
using the teXsan program package.33 The positions of the non-
hydrogen atoms were determined by Patterson methods and
(NCisocyanide), 1734 cm-1 1H NMR (C6D6): δ 0.93 (t, J ) 7.4
.
Hz, 3H, CH2Me), 1.26 and 1.40 (m, 2H each, NCH2CH2CH2),
3.22 (t, J ) 6.6 Hz, 2H, NCH2), 3.10 (s, 3H, OMe), 2.35-2.55
(m, 8H, PCH2). 31P{1H} NMR (C6D6): δ 71.8 (s).
(33) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corp.: The Woodlands, TX, 1985 and 1992.

Conversion of Benzaldehyde Imines into Isocyanides
Organometallics, Vol. 18, No. 20, 1999 4173
Ta ble 6. Cr ysta llogr a p h ic Da ta for 7a ‚2C6H6, 12‚C6H6, 9a , 10a ‚1/2C6H6, a n d 13e
7a ‚2C6H6
12‚C6H6
9a
10a ‚1/2C6H6
13e
formula
fw
space group
a (Å)
b (Å)
c (Å)
C
71H65N3P4Mo
C72H64N2P4Mo
1177.15
P2/c (No. 13)
12.233(2)
12.391(5)
19.718(3)
90
93.41(1)
90
2983(1)
2
C60H53NOP4Mo
1023.92
P21/n (No. 14)
11.094(8)
26.412(6)
17.392(5)
90
100.16(3)
90
5016(3)
4
C70H63N2OP4Mo
1168.12
P1h (No. 2)
10.382(2)
12.113(2)
24.231(4)
100.70(1)
93.65(2)
102.17(1)
2909.9(9)
2
C61H60N2P4Mo
1040.99
P1h (No. 2)
11.8428(8)
13.390(1)
18.522(1)
79.707(7)
81.434(6)
65.707(6)
2624.7(4)
2
1180.15
P1h (No. 2)
11.3451(6)
15.713(2)
17.645(2)
97.286(9)
93.183(6)
103.892(7)
3016.6(5)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F
calc (g cm-3
)
1.299
1228
3.68
1.310
1224
3.71
1.356
2120
4.31
1.333
1214
3.81
1.317
1084
4.12
F(000)
µ
calc (cm-1
)
transmn factor
cryst size (mm3)
scan type
2θ range (deg)
no. measd
no. unique
no. obsd
0.9091-0.9987
0.4 × 0.4 × 0.2
ω-2θ
0.9218-0.9981
0.2 × 0.2 × 0.2
ω-2θ
0.9709-0.9988
0.5 × 0.15 × 0.1
ω
0.8559-0.0990
0.7 × 0.7 × 0.15
ω-2θ
0.9541-0.9999
0.8 × 0.5 × 0.3
ω-2θ
5-50
5-40
5-55
5-50
5-55
11055
10635
7090
3150
2973
2019
12090
11504
6280
10809
10280
7044
12580
12065
7352
no. var
713
0.034
0.033
357
0.036
0.036
605
0.041
0.036
703
0.037
0.036
846
0.037
0.038
Ra
b
Rw
GOF
1.41
0.22, -0.23
1.53
0.36, -0.31
1.35
0.37, -0.40
1.62
0.52, -0.43
1.66
0.85, -0.33
residual peaks (e/Å-3
)
a
b
2 1/2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑wFo
] .
subsequent Fourier syntheses (DIRDIF PATTY),34 which were
refined anisotropically by full-matrix least-squares techniques.
The hydrogen atoms in 13e were found in the Fourier map
except for the η2-H2 hydrogens and refined isotropically, while
unobserved η2-H2 hydrogens were not included for refinements.
For the other complexes, all hydrogen atoms were placed at
the calculated positions and included in the final stages of
refinements with fixed parameters.
X-ray diffraction studies were undertaken also for the
following compounds. Although the analyses could not be
completed as described below, the preliminary results clarified
the atom connecting scheme in these compounds.
7c‚3/2C6H6: a ) 13.278(3) Å, b ) 22.298(3) Å, c ) 11.497(2)
Å, R ) 92.34(1)°, â ) 113.43(1)°, and γ ) 104.19(1)° with Z )
2 in space group P1h (No. 2). R (Rw) ) 0.067 (0.053) for 3594
data with I > 3.0 σ(I). Carbon atoms in the dppe ligands were
treated only isotropically.
7f: a ) 10.905(3) Å, b ) 12.370(5) Å, c ) 18.996(5) Å, R )
98.69(3)°, â ) 101.42(2)°, and γ ) 94.78(3)° with Z ) 2 in space
group P1h (No. 2). R (Rw) ) 0.080 (0.082) for 3747 data with I
> 3.0 σ(I). An uncharacterizable large peak still remained in
the final Fourier map.
7g: a ) 12.821(4) Å, b ) 17.594(3) Å, c ) 11.471(3) Å, R )
100.56(2)°, â ) 103.47(3)°, and γ ) 84.54(2)° with Z ) 2 in
space group P1h (No. 2). R (Rw) ) 0.078 (0.070) for 4825 data
with I > 3.0 σ(I). The least-squres refinements resulted in the
unusually large temperature factors for the Pri carbons prob-
ably due to the disorder of this group.
Ack n ow led gm en t. This work was supported by the
Ministry of Education, Science, Sports, and Culture of
J apan (Grant Nos. 09102004 and 09238103).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and equivalent isotropic thermal parameters,
anisotropic thermal parameters, and extensive bond lengths
and angles, together with figures with full atom-numbering
scheme, for 7a , 9a , 10a , 12, and 13e. This material is available
free of charge via the Internet at http://pubs.acs.org.
(34) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bos-
man, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla,
C. The DIRDIF program system; Technical Report of the Crystal-
lography Laboratory: University of Nijmegen, The Netherlands, 1992.
OM9904605