Reaction of a diphosphene complex with dimethylcyanamide

Article abstract of DOI:10.1021/om021016w

The reaction of the diphenyldiphosphene[W(CO)₅]₃ complex 1 with N,N-dimethylcyanamide affords complex 2, resulting from the formal addition of one H and one N=CH-NMe₂ unit onto the P=P double bond of 1 as the major product. A bicyclic complex (3) probably resulting from an initial substitution of one cis-CO of each [P-W(CO)₅] group by the cyanamide is also formed. Both 2 and 3 have been characterized by X-ray crystal structure analysis.

Full text of DOI:10.1021/om021016w

1346
Organometallics 2003, 22, 1346-1347
Rea ction of a Dip h osp h en e Com p lex w ith
Dim eth ylcya n a m id e
Ngoc Hoa Tran Huy,* Louis Ricard, and Franc¸ois Mathey*
Laboratoire “He´te´roe´le´ments et Coordination” UMR CNRS 7653, DCPH, Ecole Polytechnique,
91128 Palaiseau Cedex, France
Received December 17, 2002
Summary: The reaction of the diphenyldiphosphene-
[W(CO)5]3 complex 1 with N,N-dimethylcyanamide af-
fords complex 2, resulting from the formal addition of
one H and one NdCH-NMe2 unit onto the PdP double
bond of 1 as the major product. A bicyclic complex (3)
probably resulting from an initial substitution of one cis-
CO of each [P-W(CO)5] group by the cyanamide is also
formed. Both 2 and 3 have been characterized by X-ray
crystal structure analysis.
In tr od u ction
Only a few [2+2] cycloaddition reactions have been
described with diphosphenes or their complexes.1 These
include the reaction of a metalladiphosphene with
electron-poor alkenes,2 the condensation of a diphos-
phene complex with alkynes,3 and the reaction of a
metalladiphosphene with an aminophosphaalkyne.4 In
the context of the phosphorus-nitrogen vs phosphorus-
carbon analogies,5 it was interesting to transpose the
last reaction with the nitrogen analogues of aminophos-
phaalkynes.
Resu lts a n d Discu ssion
F igu r e 1. ORTEP drawing of one molecule of 2a . Selected
bond lengths (Å) and angles (deg): P(1)-W(1) 2.519(2),
P(1)-C(4) 1.813(8), P(1)-P(2) 2.258(3), P(2)-C(10) 1.86-
(1), P(2)-N(1) 1.64(1), P(2)-W(2) 2.512(2), N(1)-C(1) 1.27-
(2), N(2)-C(1) 1.38(1), N(2)-C(2) 1.43(1), N(2)-C(3) 1.40-
(1); C(4)-P(1)-W(1) 117.2(2), C(4)-P(1)-H 97(4), C(4)-
P(1)-P(2) 103.6(3), P(2)-P(1)-W(1) 123.2(1), N(1)-P(2)-
C(10) 100.4(5), N(1)-P(2)-P(1) 101.7(3), C(10)-P(2)-P(1)
97.4(3), N(1)-P(2)-W(2) 122.1(3), C(10)-P(2)-W(2) 115.7-
(3), P(1)-P(2)-W(2) 115.6(1), C(1)-N(1)-P(2) 119.7(8),
C(1)-N(2)-C(3) 118(1), C(1)-N(2)-C(2) 119(1), C(3)-
N(2)-C(2) 122(1).
We decided to investigate the reaction of the diphos-
phene complex 13 with N,N-dimethylcyanamide. Heat-
ing 1 with a 4-fold excess of cyanamide in reflexing
xylene led to two products (eq 1).
The major product (2) is a mixture of two diastereo-
mers and incorporates a P-P and a P-H bond as shown
by its 31P NMR spectrum. 2a (65%): δ31P (CDCl3) -7.7,
1
1J PP ) 114.6 Hz, J PH ) 320 Hz (PH); +69.2 (P-N). 2b
(35%): δ31P -1.8, 1J P-P ) 145 Hz, 1J P-H ) 322 Hz (PH);
+65.7 (P-N). The major isomer was crystallized in CH2-
Cl2. The X-ray crystal structure analysis (Figure 1)
demonstrates that 2 results from the formal addition
of the diphosphene to the cyanamide +2H. Noteworthy
are the planarity of the NMe2 nitrogen and the delo-
calization of the NdCH-NMe2 unit. The most likely
mechanism for the formation of 2 implies the initial
formation of a zwitterionic adduct (4) by nucleophilic
attack of the CtN nitrogen onto the PdP double bond.
It is interesting to note that a similar adduct has been
(1) Review: Weber, L. Chem. Rev. 1992, 92, 1839.
(2) Weber, L.; Frebel, M.; Boese, R. Chem. Ber. 1990, 123, 733.
(3) Tran Huy, N. H.; Inubushi, Y.; Ricard, L.; Mathey, F. Organo-
metallics 1997, 16, 2506.
(4) Grobe, J .; Le Van, D.; Pohlmeyer, T.; Krebs, B.; Conrad, O.;
Dobbert, E.; Weber, L. Organometallics 1998, 17, 3383.
(5) Reviews: Dillon, K. B.; Mathey, F.; Nixon, J . F. Phosphorus: The
Carbon Copy; Wiley: Chichester, 1998. Mathey, F. Angew. Chem., Int.
Ed., in press.
10.1021/om021016w CCC: $25.00 © 2003 American Chemical Society
Publication on Web 02/15/2003

Notes
Organometallics, Vol. 22, No. 6, 2003 1347
eters might explain this difference: (1) the cyanamide
is a much better donor than the phosphaalkyne; (2) the
PdP substrate is apolar in the first case and highly
polarized in the second case. More work would be
needed to understand the outcome of these reactions.
Exp er im en ta l Section
NMR spectra were recorded on a multinuclear Bruker
AVANCE 300 MHz spectrometer operating at 300.13 for 1H,
75.47 for 13C, and 121.50 MHz for 31P. Chemical shifts are
expressed in parts per million (ppm) downfield from internal
tetramethylsilane (1H and 13C) and external 85% aqueous H3-
PO4 (31P). Elemental analyses were performed by the Service
de microanalyse du CNRS, Gif-sur-Yvette, France
Dip h osp h in e Com p lexes (2a ,b). A solution of the diphos-
phene complex 1 (350 mg, 3 × 10-4 mol) and N,N-dimethyl-
cyanamide (0.1 mL, 12 × 10-4 mol) in xylene (3 mL) was
heated at 130 °C for 45 min. After evaporation of the solvent,
the residue was chromatographed on silica gel with 4:1 hexane/
CH2Cl2 as the eluent. Complex 2 was isolated as white crystals
(125 mg, 45%).
F igu r e 2. ORTEP drawing of one molecule of 3. Phenyls
are omitted for clarity. Selected bond lengths (Å) and angles
(deg): W(1)-N(2) 2.250(4), N(2)-C(1) 1.303(7), C(1)-N(1)
1.341(6), C(1)-P(1) 1.872(6), P(1)-C(3) 1.820(6), P(1)-P(2)
2.245(2), P(1)-W(2) 2.480(2), P(2)-W(1) 2.469(2), P(2)-
C(2) 1.863(6), P(2)-C(11) 1.816(5), C(2)-N(4) 1.342(6),
C(2)-N(3) 1.299(7), N(3)-W(2) 2.235(4); P(2)-W(1)-N(2)
79.1(1), W(1)-N(2)-C(1) 133.9(4), N(2)-C(1)-P(1) 118.1-
(4), C(1)-P(1)-P(2) 98.2(2), P(1)-P(2)-W(1) 107.01(6),
C(1)-P(1)-C(3) 101.0(3), C(3)-P(1)-P(2) 99.8(2).
Com p lex 2a . 1H NMR (CDCl3): δ 3.13 (s, Me), 3.23 (s, Me),
6.17 (dd, 1J H-P ) 320 Hz, 2J H-P ) 14 Hz, PH), 7.68 (d, 3J H-P
)
21.9 Hz, CHdN). 13C NMR (CDCl3): δ 34.24 (s, Me), 39.92 (s,
2
3
Me), 163.43 (dd, J CP ) 22.3 Hz, J CP ) 5.4 Hz, CHdN). Anal.
Calcd for C25H18O10N2P2W2: C, 32.08; H,1.94. Found: C, 32.06;
H, 2.04.
Com p lex 2b. 1H NMR (CDCl3): δ 3.09 (s, Me), 3.15 (s, Me),
postulated in the reaction of iPr2N-CtP with a metal-
5.95 (dd, 1J H-P ) 322 Hz, 2J H-P ) 14 Hz, PH), 7.80 (d, 3J H-P
)
ladiphosphene.4
22.3 Hz, CHdN). 13C NMR (CDCl3): δ 33.92 (s, Me), 39.89 (s,
2
3
Me), 162.00 (dd, J CP ) 19.5 Hz, J CP ) 4.8 Hz, CHdN).
Com p lex 3. The chromatographic purification was carried
out with 2:1 hexane/CH2Cl2 as the eluent. Complex 3 was
isolated as yellow crystals (25 mg, 9%). 31P NMR (CDCl3): δ
34.0 (dd, 1J P-W ) 161.5 Hz, 2J P-W ) 67.2 Hz). 1H NMR (CDCl3):
δ 2.98 (s, NMe2), 6.39 (pseudo t, NH). 13C NMR (CDCl3): δ 53.9
(s, NMe2), 177.6 (m, CdN).
Cr ysta llogr a p h ic d a ta for 2a : C25H18N2O10P2W2; M )
936.05 g/mol; triclinic; space group P1h; a ) 9.847(1) Å, b )
10.539(1) Å, c ) 14.951(1) Å, R ) 89.360(1)°, â ) 76.650(1)°, γ
) 78.000(1)°, V ) 1475.6(2) Å3; Z ) 2; D ) 2.107 g cm-3; µ )
7.954 cm-1; F(000) ) 880. Crystal dimensions 0.20 × 0.12 ×
0.06 mm. Total reflections collected 11 828 and 7167 with I >
2σ(I). Goodness of fit on F2 1.047; R(I>2σ(I)) ) 0.0473, wR2 )
0.1217(all data); maximum/minimum residual density 2.894-
However in our case, the zwitterion does not cyclize
but abstracts 2H from the solvent. The formation of the
secondary product (3) has a completely different origin.
It is known that cyanamides are good ligands via their
CtN nitrogen.6 Substitution of one cis-CO on both
W(CO)5 groups yields the intermediate complex 5, which
can cyclize to give 3 upon abstraction of hydrogen from
the solvent. The structure of 3 has been unambiguously
established by X-ray analysis (Figure 2). Once again,
the NMe2 nitrogen is planar and the delocalization of
the NdC-N unit appears even more effective than in
the case of 2a . When comparing the reactions of R2N-
CtP4 and R2N-CtN with a PdP unit, it is striking to
see that the final products are quite different, whereas
the postulated intermediates are similar. Two param-
(0.235)/-3.141(0.235) e Å-3
.
Cr ysta llogr a p h ic d a ta for 3: C27H25Cl3N4O8P2W2; M )
1069.50 g/mol; monoclinic; space group P21/c; a ) 9.867(5) Å,
b ) 11.807(5) Å, c ) 30.100(5) Å, â ) 98.580(5)°, V ) 3467(2)
Å3; Z ) 4; D ) 2.049 g cm-3; µ ) 7.005 cm-1; F(000) ) 2032.
Crystal dimensions 0.20 × 0.12 × 0.06 mm. Total reflections
collected 17 494 and 8036 with I > 2σ(I). Goodness of fit on F2
1.101; R(I>2σ(I)) ) 0.0421, wR2 ) 0.1131(all data); maximum/
minimum residual density 3.730(0.223)/-3.947(0.223) e Å-3
.
Data were collected on a KappaCCD diffractometer at 150.0-
(1) K with Mo KR radiation (λ ) 0.71073 Å).
(6) See for example: Desjardins, P.; Yap, G. P. A.; Crutchley, R. J .
Inorg. Chem. 1999, 38, 5901. Ferreira, C. M. P.; da Silva, M. F. C. G.;
da Silva, J . J . R. F.; Pombeiro, A. J . L.; Kukushkin, V. Y.; Michelin, R.
A. Inorg. Chem. 2001, 40, 1134. Fairlie, D. P.; J ackson, W. G.; Skelton,
B. W.; Wen, H.; White, A. H.; Wickramasinghe, W. A.; Woon, T. C.;
Taube, H. Inorg. Chem. 1997, 36, 1020.
Su p p or tin g In for m a tion Ava ila ble: Full details of the
crystallographic analysis. This material is available free of
charge via the Internet at http://pubs.acs.org.
OM021016W