Fig. 1 ORTEP diagrams of the cations of compounds 7, 9 and 15. Only the major component of compound 9 is shown. Hydrogen atoms have been
˚
eliminated for clarity and thermal ellipsoids are shown at the 50% probability level. Selected bond lengths (A) and angles (u): 7: Fe(1)–P(1) 2.1691(4); P(1)–
N(1) 1.624(1); P(1)–N(2) 1.575(1); N(2)–N(3) 1.403(2); N(3)–C(14) 1.296(2); Fe(1)–P(1)–N(1) 126.19(4); Fe(1)–P(1)–N(2) 124.59(4); P(1)–N(2)–N(3)
114.45(9). 9: Fe(1)–P(1) 2.2135(8); 2.2135(8); P(1)–C(1) 1.633(3); P(1)–N(1) 1.641(2); Si(1)–C(1) 1.862(3); Fe(1)–P(1)–N(1) 119.80(8); Fe(1)–P(1)–C(1)
126.3(1); P(1)–C(1)–Si(1) 138.4(2). 15: W(1)–P(1) 2.7289(9); W(1)–N(1) 2.076(2); W(1)–N(2) 2.201(2); P(1)–N(2) 1.704(2); P(1)–N(3) 1.642(2); N(1)–N(2)
1.424(3); N(2)–N(3) 1.403(2); N(1)–C(13) 1.294(3); W(1)–P(1)–N(2) 53.70(7); W(1)–P(1)–N(3) 111.78(8); W(1)–N(2)–P(1) 87.69(8); W(1)–N(1)–N(2)
75.4(1); W(1)–N(2)–N(1) 65.9(1); W(1)–N(1)–C(13) 155.9(2); N(1)–N(2)–P(1) 102.1(1); N(2)–N(1)–C(13) 126.3(2).
The complex [CpFe(CO)2(g1-PNiPr2)]AlCl4 (1) which has been
fully characterised was prepared via AlCl3 induced halide
abstraction from the phosphide precursor [CpFe(CO)2(g1-
P(Cl)NiPr2)] (6). A resonance appears in the 31P NMR spectrum
of 1 at d 922, similar to that of the structurally characterised
analogue [Cp*Fe(CO)2(g1-PNiPr2)]AlCl4 (d 965).10
atom in [Cp*W(CO)2{g3-P(NiPr2)NNCPh2}]AlCl4 (15) and con-
firmed the loss of CO from 5. The diazaphosphaallene ligand is
oriented in an exo fashion with W–N(1) and N(2) separations of
˚
2.076(2) A and 2.201(2) A, respectively. The W–P(1) bond length
˚
˚
(2.7289(9) A) is lengthened significantly compared to the WLP
1
separation in 5 (2.4503(6) A) indicating that the phosphorus atom
˚
of the g3-diazaphosphaallene ligand is rather weakly bound to the
The addition of Ph2CN2 to 1 (Scheme 1) rapidly affords a
complex containing an g1-coordinated phosphaazine ligand
[CpFe(CO)2{g1-P(NiPr2)LN–NL(CPh2)}]AlCl4 (7). The 31P
NMR spectrum of 7 exhibits a resonance at d 291 Hz. The
metal centre. To our knowledge this is the first diazaphosphaallene
complex to be described although
a
related molecule
[CpMo(CO)2(g3-P(tBu)PC(SiMe3)2)] containing a diphosphaallyl
ligand recently described by Weber and co-workers has a similar
11
Mo–P(2) separation of 2.6756(3) A. Since the reactivity of
X-ray structure{ (Fig. 1) shows that the phosphaazine ligand is
1
g -bound to iron via phosphorus (Fe–P(1) 5 2.1691(4) A) and that
˚
˚
the NiPr2 and NCPh2 substituents have a trans disposition with
thermally stable, electrophilic phosphinidene complexes is typically
initiated by binding of nucleophilic substrates to the vacant
p-orbital on phosphorus,2 we believe that the addition of Ph2CN2
to 5 results in the initial formation of adduct 12 which then
subsequently undergoes CO loss to form g3-diazaphosphaallene
complex 15. Although 12 has not been observed spectroscopically,
the isolation and structural characterisation of complex 7 strongly
supports the proposed mechanism. Analogues [Cp*M(CO)2{g3-
P(NiPr2)NN(CPh2)}]AlCl4 (M 5 Cr (13); Mo (14)) were prepared
similarly.
˚
respect to the PLN double bond (P(1)–N(2) 5 1.575(1) A). The
complex [Cp*Fe(CO)2{g1-P(NiPr2)LN–N(CPh2)}]AlCl4 (8) pre-
pared in the same manner has a similar structure.
The addition of the diazoalkane Me3SiCHN2 to 1 proceeds with
vigorous gas evolution to afford the g1-phosphaalkene complex
[CpFe(CO)2{g1-P(NiPr2)LCHSiMe3}]AlCl4 (9) (d 31P 241). The
1H NMR spectrum of 9 shows a resonance for the LCH signal at d
2
6.43 and the relatively large JPH coupling of 36.8 Hz strongly
suggests that N2 has been lost during the reaction with the
formation of a PLC bond. This is confirmed by the X-ray
structure{ (Fig. 1). The major structural features include a typical
In conclusion, we have shown that terminal electrophilic
phosphinidene ligands may be converted into g1-phosphaazine,
g1-phosphaalkene and g3-diazaphosphaallene ligands. The highly
reactive nature of the phosphinidene complexes allows for the
synthesis of a wide range of phosphorus-containing ligands that are
difficult or impossible to obtain using standard synthetic protocols.
This work was supported by the National Research Council of
Canada and the Natural Sciences and Engineering Research
Council of Canada (to A.J.C.).
piano-stool ligand arrangement about the iron atom and a Fe–P(1)
i
separation of 2.2135(8) A. The bulky N Pr2 and SiMe3 groups are
˚
in the expected trans positions about the PLC double bond (P(1)–
˚
˚
C(1) 5 1.633(3) A; P(1)–N(1) 5 1.641(2) A). Attempts to convert 7
into a phosphaalkene complex similar to 9 (70 uC overnight) via
loss of N2 resulted only in decomposition.
When Ph2CN2 was added to [Cp*W(CO)3(g1-PNiPr2)]AlCl4 (5)
the immediate evolution of gas was also observed, together with
the formation of a complex with a 31P NMR resonance at d 125.
An X-ray structure determination{ established the presence of a
novel diazaphosphaallene ligand g3-coordinated to the tungsten
Notes and references
{ Crystallographic data for: 7 [C27H31AlCl6FeN3O2P], 756.05, monoclinic,
˚
˚
˚
P21/c, a 5 10.3584(8) A, b 5 17.449(1) A, c 5 18.948(2) A, b 5 99.531(1)u,
This journal is ß The Royal Society of Chemistry 2005
Chem. Commun., 2005, 5890–5892 | 5891
Graham, Todd W.
