suggesting that the process is a thermal E/Z isomerization of the
phosphaalkene (eqn (3)).10
reported. However, the most related reaction in the literature is
a 1,2-phenyl migration from a P(V) intermediate.14
This synthesis, insertion of an organic isocyanide in to the Zr–P
bond of a primary phosphido complex followed by rearrangement,
takes advantage of phenylphosphine as the phosphorus source and
commercially available benzyl isocyanide. Such a strategy avoids
salt elimination and exhibits perfect atom economy. We are
currently expanding this novel transformation into a general
synthesis.
ð3Þ
This work was supported by the University of Vermont and the
U.S. National Science Foundation (Grant #0521237 to J. M. T.).
The authors thank Prof. John Protasiewicz for helpful discussions.
The structure of 3 was confirmed by a single-crystal X-ray
diffraction study, and a perspective view of the complex is shown
in Fig. 1.§ The phosphaalkene is in the E configuration in the solid
state, and P, C(16), H(16) and C(21) (the ipso carbon of the phenyl
ring on P) are coplanar, which is implicit of an sp2-hybridized
Notes and references
˚
phosphorus center. The P–C bond length of 1.716(2) A is
{ Experimental data: (N3N)Zr[C(PHPh)LNCH2Ph] (2). A 6 mL benzene
solution of (N3N)ZrPHPh (86 mg, 0.154 mmol) was cooled to ca. 5 uC, and
a 2 mL benzene solution of PhCH2NMC (18 mg, 0.154 mmol) was added.
The resultant orange solution was then frozen, and the benzene removed by
lyophilization to give a pale orange powder (98 mg, 0.144 mmol, 94%). 1H
NMR (C6D6, 500.1 MHz): d 7.750 (t, C6H6, 2 H), 7.554 (d, C6H6, 2 H),
7.202 (t, C6H6, 2 H), 7.102 (m, C6H6, 4 H), 6.038 (d, PH, JPH = 259 Hz),
4.903 (s, CH2, 2 H), 3.287 (br s, CH2, 6 H), 2.484 (s, CH2, 6 H), 0.090 (s,
somewhat long compared to other structurally characterized
phosphaalkenes, despite the relatively small hydrogen and phenyl
substituents.4,5 The slightly elongated P–C bond may result from a
zwitterionic resonance contributor where there is some C–N
double bond character and a delocalized system. In support of
˚
CH3, 27 H). 13C NMR (C6D6, 125.8 MHz): d 263.21 (d, CLN, JPC
=
this hypothesis, the C–N bond length of 1.362(2) A of 3 is
slightly shorter than expected for
C–N single bond.11
a
99.5 Hz), 137.93 (s, Ph), 135.75 (d, Ph, JPC = 16.6 Hz), 129.34 (s, Ph),
129.01 (s, Ph), 128.68 (s, Ph), 128.66 (d, Ph, JPC = 6.9 Hz), 128.48 (s, Ph),
126.56 (s, Ph), 63.27 (d, CH2, JPC = 19.4 Hz), 61.21 (s, CH2), 47.45 (s,
CH2), 2.19 (s, CH3). 31P{1H} NMR (C6D6, 202.4 MHz): 239.98 (s). IR
(KBr, Nujol): 2280s (nPH), 1705s (nCN) cm21. (N3N)Zr[N(CH2Ph)C-
(H)LPPh] (3). A 3 mL benzene solution of (N3N)ZrPHPh (173 mg,
0.309 mmol) and PhCH2NMC (36 mg, 0.309 mmol) was heated to 90 uC for
3 h. The orange solution was then frozen, and the benzene removed by
lyophilization to give an orange powder, which was extracted into ca. 3 mL
Et2O. The orange solution was filtered then cooled to 230 uC to yield pale
yellow crystals in several crops (163 mg, 0.241 mmol, 78%). 1H NMR
(C6D6, 500.1 MHz): 10.291 (br s, CH, 1 H), 7.836 (br, C6H6, 2 H), 7.543
(br, C6H6, 2 H), 7.260 (t, C6H6, 2 H), 7.092 (m, C6H6, 2 H), 7.045 (m,
C6H6, 2 H), 5.207 (s, CH2, 2 H), 3.204 (s, CH2, 6 H), 2.278 (s, CH2, 6 H),
0.170 (s, CH3, 27 H). 13C NMR (C6D6, 125.8 MHz): d 193.12 (d, CLN,
JPC = 55.6 Hz), 138.76 (s, Ph), 133.35 (s, Ph), 132.88 (d, Ph, JPC = 16.6 Hz),
128.46 (s, Ph), 128.28 (s, Ph), 126.71 (s, Ph), 126.37 (s, Ph), 65.73 (s, CH2),
64.46 (s, CH2), 46.78 (s, CH2), 1.38 (s, CH3), one phenyl carbon resonance
was not observed, presumably obscured by solvent. 31P{1H} NMR (C6D6,
202.4 MHz): 91.85 (s). Anal. Calc. for C29H52N5PSi3Hf: C, 51.43; H, 7.74;
N, 10.34. Found: C, 51.54; H, 7.44; N, 10.63%.
Additionally, N is coplanar with the phosphaalkene fragment,
which is also consistent with delocalization. Known amine-
substituted phosphaalkenes display similar bond lengths.12
Interestingly, complex 3 is a rare instance of metal complex
containing a phosphaalkene moiety that is not involved in
coordination to the metal center.13
A rich reaction chemistry has developed around phosphaalkenes
as facile syntheses evolved.1,4,5 There are several common routes
to these molecules including 1,2-elimination, condensation,
and rearrangement reactions.4 Synthesis of phosphaalkenes by a
1,2-hydride migration appears not to have been previously
§ Crystal data for 3, C29H52N5PSi3Zr, M = 677.22, monoclinic, P21/c, a =
˚
16.5616(8), b = 10.9871(5), c = 21.170(1) A, b = 110.889(1)u, Z = 4, V =
3
3598.9(3) A , T = 125(2) K, m(Mo-Ka) = 0.475 mm21. Of 49757 total
˚
reflections (pale yellow block, 1.35 ¡ h ¡ 30.45u), 10366 were independent
(Rint = 3.51%). The structure was solved using direct methods and standard
difference map techniques and refined by full-matrix least-squares
procedures on F2. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms on carbon were included in calculated positions and were
refined using a riding model except the hydrogen atom on the
phosphaalkene carbon, H(16), which was located in the Fourier difference
map and refined. R(F) = 2.89%, R(wF) = 6.78%, GoF = 1.033. CCDC
651742. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b709506f
1 F. Mathey, Phosphorus-Carbon Heterocyclic Chemistry: The Rise of a
New Domain, Pergamon, Amsterdam, 2001; E. Niecke, A. Fuchs,
F. Baumeister, M. Nieger and W. W. Schoeller, Angew. Chem., Int. Ed.
Engl., 1995, 34, 555–557; J. I. Bates and D. P. Gates, J. Am. Chem. Soc.,
2006, 128, 15998–15999; D. Martin, F. S. Tham, A. Baceiredo and
G. Bertrand, Chem.–Eur. J., 2006, 12, 8444–8450.
2 F. Ozawa and M. Yoshifuji, Dalton Trans., 2006, 42, 4987–4995;
M. Yoshifuji, Pure Appl. Chem., 2005, 77, 2011–2020.
3 I. Manners, Angew. Chem., Int. Ed., 2007, 46, 1565–1568;
T. Baumgartner and R. Reau, Chem. Rev., 2006, 106, 4681–4727;
K. J. T. Noonan and D. P. Gates, Angew. Chem., Int. Ed., 2006, 45,
7271–7274; V. A. Wright, B. O. Patrick, C. Schneider and D. P. Gates,
Fig. 1 Perspective view of the molecular structure of 3 with hydrogen
atoms except H(16) omitted for clarity. Thermal ellipsoids shown at the
35% probability level. Selected metrical parameters: N(5)–C(16) 1.362(2),
N(5)–C(17) 1.465(2), P–C(16) 1.716(2), P–C(21) 1.831(2), C(16)–H(16)
0.96(2), Zr–N(1) 2.064(1), Zr–N(3) 2.071(1), Zr–N(2) 2.081(1), Zr–N(5)
˚
2.187(1), Zr–N(4) 2.498(1) A; C(16)–N(5)–C(17) 114.3(1), C(16)–N(5)–Zr
121.75(9), C(17)–N(5)–Zr 122.12(9), N(5)–C(16)–P 126.4(1), N(5)–C(16)–
H(16) 114.2(1), P–C(16)–H(16) 119.3(1), C(16)–P–C(21) 101.63(7)u.
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