Dihapto carbamoyl (carboxamide) complexes of iron(II)

Article abstract of DOI:10.1021/om0306933

The carbamoyl ferrate Li[Fe{C(=O)NⁱPr₂}(CO) ₄] reacts in diethyl ether with Br₂PPh₃, I ₂PPh₃, or I₂ followed by triphenylphosphine to provide the complexes [Fe(η²-OCNⁱPr ₂)X-(CO)₂(PPh₃)] [X = I trans to PPh ₃ (1a); Br (1b) two isomers], each of which feature dihaptoC,O carbamoyl coordination. The reactions of 1a or 1b with AgBF₄ in the presence of CO provide [Fe(η²-OCNⁱPr ₂)(CO)₃(PPh₃)]BF₄ (2a·BF ₄), one carbonyl ligand of which is labile and readily replaced by I^-, Br^-, or PPh₃ to provide 1a, 1b, or [Fe-{η²-OCNⁱPr₂}(CO)₂(PPh ₃)₂]BF₄(2b·BF₄). The reaction of 1a with dppe leads to a separable mixture of the salt [Fe{η²- OCNⁱPr₂}(CO)₂(dppe)]I (3·I) and [Fe{η²-OCNⁱPr₂}I(CO)(dppe)] (4). Successive treatment of Li[Fe{C(=O)NⁱPr₂}(CO)₄] with ClSnPh₃ and PPh₃ provides the stannyl complex [Fe(η²-OCNⁱPr₂)(SnPh₃)(CO) ₂(PPh₃)] (1d). Treating Id with iodine leads to Sn-Fe rather than Sn-C cleavage and formation of 1a. In all the above transformations the integrity of the dihapto carbamoyl coordination is ultimately retained. The crystal structures of 1d and 2b·PF₆ are reported.

Full text of DOI:10.1021/om0306933

2686
Organometallics 2004, 23, 2686-2693
Dih a p to Ca r ba m oyl (Ca r boxa m id e) Com p lexes of Ir on (II)
Stephen Anderson,† Timothy E. Berridge,‡ Anthony F. Hill,*,‡,§ Ying Thong Ng,‡
Andrew J . P. White,‡ and David J . Williams‡
School of Theoretical and Applied Sciences, Ramapo College, Mahwah, New J ersey 07430,
Department of Chemistry, Imperial College London, South Kensington London, U.K., and
Research School of Chemistry, Institute of Advanced Studies, Australian National University,
Canberra ACT, Australia
Received December 24, 2003
The carbamoyl ferrate Li[Fe{C(dO)NiPr2}(CO)4] reacts in diethyl ether with Br2PPh3,
I2PPh3, or I2 followed by triphenylphosphine to provide the complexes [Fe(η2-OCNiPr2)X-
(CO)2(PPh3)] [X ) I trans to PPh3 (1a ); Br (1b) two isomers], each of which feature dihapto-
C,O carbamoyl coordination. The reactions of 1a or 1b with AgBF4 in the presence of CO
provide [Fe(η2-OCNiPr2)(CO)3(PPh3)]BF4 (2a ‚BF4), one carbonyl ligand of which is labile and
readily replaced by I-, Br-, or PPh3 to provide 1a , 1b, or [Fe{η2-OCNiPr2}(CO)2(PPh3)2]BF4
(2b‚BF4). The reaction of 1a with dppe leads to a separable mixture of the salt [Fe{η2-OCNi-
Pr2}(CO)2(dppe)]I (3‚I) and [Fe{η2-OCNiPr2}I(CO)(dppe)] (4). Successive treatment of Li[Fe-
{C(dO)NiPr2}(CO)4] with ClSnPh3 and PPh3 provides the stannyl complex [Fe(η2-OCNiPr2)-
(SnPh3)(CO)2(PPh3)] (1d ). Treating 1d with iodine leads to Sn-Fe rather than Sn-C cleavage
and formation of 1a . In all the above transformations the integrity of the dihapto carbamoyl
coordination is ultimately retained. The crystal structures of 1d and 2b‚PF6 are reported.
In tr od u ction
Rather, access is provided to a wealth of unanticipated
chemistry that almost exclusively involves the surpris-
ingly stable carbamoyl ligand adopting a purely spec-
tatorial role.10 We report herein the synthesis of a range
of carbamoyl complexes of divalent iron, all of which
feature the apparently favorable bidentate coordination
Carbamoyl (carboxamido) complexes LnMC(dO)NR2
(Chart 1) have received considerably less attention than
their acyl analogues LnMC(dO)R′. Comparatively little
novel ligand-based chemistry has been added in the
interim to that reviewed by Angelici1 in 1972. Principal
foci of carbamoyl coordination chemistry have included
(i) their use, particularly anionic examples, as inter-
mediates in the synthesis of aminomethylidene2 and
aminomethylidyne complexes;3 (ii) their implication in
the metal-mediated (often catalytic) formation of urea
derivatives;4 (iii) their formation by carbonylation of
metal amido complexes;5 (v) implicit formamide C-H
activation processes,6 and (vi) the reactions of coordi-
nated CO with amines.7 By far the bulk of this chem-
istry has involved monodentate coordination of the
carbamoyl ligand through carbon.
(4) (a) Busetto, L.; Palazzi, A. Inorg. Chim. Acta 1982, 64, L39. (b)
Probert, G. D.; Whitby, W. J . Tetrahedron Lett. 1995, 36, 4113. (c)
Diversi, P.; Ermini, L.; Ingrosso, G.; Lucherini, A.; Pinzino, C.;
Sagramora, L. J . Organomet. Chem. 1995, 494, C1. (d) Wakita, Y.;
Noma, S. Y.; Maeda, M.; Kojima, M. J . Organomet. Chem. 1985, 297,
379. (e) Giannoccaro, P.; Tommasi, I.; Aresta, M. J . Organomet. Chem.
1994, 476, 13. (f) Poszmik, G.; Carroll, P. J .; Wayland, B. B. Organo-
metallics 1993, 12, 3410. (g) Balas, L.; J ousseaume, B.; Shin, H.;
Verlhac, J . B.; Wallian, F. Organometallics 1991, 10, 366. (h) Gargulak,
J . D.; Gladfelter, W. L. J . Am. Chem. Soc. 1994, 116, 3792. (i) Gargulak,
J . D.; Gladfelter, W. L. Inorg. Chem. 1994, 33, 253. (j) McCusker, J .
E.; Logan, J .; McElwee-White, L. Organometallics 1998, 17, 4037. (k)
McCusker, J . E.; Abboud, K. A.; McElwee-White, L. Organometallics
1997, 16, 3863.
(5) (a) Fagan, P. J .; Manriquez, J . M.; Vollmer, S. H.; Secaur Day,
C.; Day, V. W.; Marks, T. J . J . Am. Chem. Soc. 1981, 103, 2206. (b)
Hartwig, J . F.; Bergman, R. G.; Andersen, R. A. J . Am. Chem. Soc.
1991, 113, 6499. (c) Rahim, M.; Bushweller, C. H.; Ahmed, K. J .
Organometallics 1994, 13, 4952. (d) J oslin, F. L.; J ohnson, M. P.;
Mague, J . T.; Roundhill, D. M. Organometallics 1991, 10, 2781. (e)
Huang, T.-M.; Chen, J .-T.; Lee, G.-H.; Wang, Y. Organometallics 1991,
10, 175.
We have attempted to employ iron carbamoyls as
precursors to aminomethylidyne complexes of iron8 but
have to date found that, with one exception,9 this
approach does not readily lead to alkylidyne complexes.
(6) (a) Muller, A.; Seyer, U.; Eltzner, W. Inorg. Chim. Acta 1979,
32, L65. (b) Coalter, J . N., III; Huffman, J . C.; Caulton, K. G.
Organometallics 2000, 19, 3569.
* Corresponding author. E-mail: a.hill@anu.edu.au.
† Ramapo College.
‡ Imperial College London.
(7) (a) Kawasaki, N.; Masuzoe, K.; Ozawa, F.; Yamamoto, A. J .
Organomet. Chem. 1989, 361, C37. (b) Szostak, R.; Strouse, C. E.; Kaez,
H. D. Inorg. Chem. 1982, 21, 1704. (c) Fernandez, M. J .; Modrego, J .;
Rodriguez, M. J .; Santamaria, M. C.; Oro, L. A. J . Organomet. Chem.
1992, 441, 155. (d) Avey, A.; Weakley, T. J . R.; Tyler, D. R. J . Am.
Chem. Soc. 1993, 115, 7706. (e) Mandal, S. K.; Ho, D. M.; Orchin, M.
Polyhedron 1992, 11, 2055. (f) Liao, W. J .; Wang, Y.-J .; Chen, J .-D.;
Lin, Y.-C.; Liu, L.-K. J . Chin. Chem. Soc. 1992, 39, 311. (g) Huang, L.;
Ozawa, F.; Osakada, K.; Yamamoto, A. Organometallics 1989, 8, 2065.
(8) Anderson, S.; Hill, A. F.; Clark, G. R. Organometallics, 1992,
11, 1988.
§ Australian National University.
(1) Angelici, R. J . Acc. Chem. Res. 1972, 18, 335.
(2) Recent examples include: (a) Chen, J .-T.; Tzeng, W.-H.; Tsai,
F.-Y.; Cheng, M.-C.; Yu, W. Organometallics 1991, 10, 3954. (b) Fischer,
E. O.; Apostolidis, C.; Dornberger, E.; Filippou, A. C.; Kanellakopulos,
B.; Lungwitz, B.; Muller, J .; Powietzka, B.; Rebizant, J .; Roth, W. Z.
Naturforsch. 1995, 50b, 1382.
(3) For general reviews of the chemistry of alkylidyne complexes
see: (a) Mayr, A.; Hoffmeister, H. Adv. Organomet. Chem. 1991, 32,
227. (b) Kim, H. P.; Angelici, R. J . Adv. Organomet. Chem. 1987, 27,
51. (c) Gallop, M. A.; Roper, W. R. Adv. Organomet. Chem. 1986, 25,
121. (d) Mayr, A.; Ahn, S. Adv. Trans. Metal Coord. Chem. 1996, 1, 1.
(e) Transition Metal Carbyne Complexes; Kreissl, F. R., Ed.; NATO
ASI Series C392; Kluwer: Dordrecht, 1992.
(9) Anderson, S.; Hill, A. F. Organometallics 1995, 14, 1562.
(10) (a) Anderson, S.; Hill, A. F.; Slawin, A. M. Z.; Williams, D. J .
J . Chem. Soc., Chem. Commun. 1993, 266. (b) Anderson, S.; Hill, A.
F.; Ng, Y. T. Organometallics 2000, 19, 15.
10.1021/om0306933 CCC: $27.50 © 2004 American Chemical Society
Publication on Web 04/22/2004

Dihapto Carbamoyl Complexes of Iron(II)
Organometallics, Vol. 23, No. 11, 2004 2687
Ch a r t 1. Acyl a n d Ca r ba m oyl (ca r boxa m id o)
Coor d in a tion
Sch em e 1. Syn th esis of
[F e(η2-OCNiP r 2)I(CO)2(P P h 3)] (1a )
of the carbamoyl ligand. This prevalence of bidentate
coordination, indicated by spectroscopic data, has
prompted us to investigate the crystal structures of two
examples, [Fe(η2-OCNiPr2)(CO)2(PPh3)2]PF6 and [Fe(η2-
OCNiPr2)(SnPh3)(CO)2(PPh3)].
Resu lts a n d Discu ssion
Fischer has reported the in situ preparation of the
iron carbamoylate salt Li[Fe{C(dO)NiPr2}(CO)4] from
the reaction of [Fe(CO)5] and lithium diisopropylamide
(hereafter LDA).11 Petz has described a related and
isolated salt, [Fe{C(dO)NMe2}(CO)4][C(NMe2)3],12 from
the reaction of [Fe(CO)5] and C(NMe2)4. Indeed, the
general class of compounds [Fe{C(dO)NR2}(CO)4][NR2H2]
has a long history, resulting from their facile equilib-
rium with [Fe(CO)5] and secondary amines (HNR2).1
The complex [Fe{C(O)NiPr2}(CO)4]- is readily alkylated
by the “hard” electrophile [Et3O]BF4 to provide the
neutral carbene complex [Fe{dC(OEt)NiPr2}(CO)4].11
Mayr has previously introduced an oxalyl chloride-
or trifluoroacetic anhydride-mediated oxide-abstraction
protocol as a convenient route to alkylidynes of group
6.13 However, in the case of Li[Fe0{C(dO)NnPr2}(CO)4],
oxalyl chloride apparently induces a redox dispropor-
tionation process to generate the bis(carbamoylate)
[FeII{C(dO)NnPr2}2(CO)4], which rearranges to the car-
bene complex [Fe0{κ2-C(NnPr2)OC(NnPr2)O}(CO)3].14 In
contrast, with Li[Fe{C(dO)NiPr2)(CO)4] and HgCl2 as
the oxidant in the presence of PPh3, the binuclear
complex [Fe2(µ-OCNiPr2)2(CO)5(PPh3)] is obtained.15
Phosphine dihalides have been previously employed as
reagents for the conversion of anionic aroylates and
carbamoylates into alkylidyne complexes of group 6
metals,16,17 and we were eager to extend this to group 8
metals, given the scarcity of general synthetic routes
for alkylidyne complexes of iron.10b,18
tion of triphenylphosphine diiodide, leads to a smooth
reaction to provide a carbamoyl derivative of iron(II),
viz., [Fe(η2-OCNiPr2)I(CO)2(PPh3)] (1a ) (88%, Scheme 1)
rather than the desired aminomethylidyne complex
[Fe(tCNiPr2)I(CO)2(PPh3)]. The same complex is also
obtained, in comparable yields (72%), if the carbamoyl
ferrate is treated sequentially with 1 equiv of iodine
followed by triphenylphosphine. The formulation follows
from spectroscopic data: In addition to metal-carbonyl
infrared absorptions at 2012 and 1948 cm-1 (Nujol), a
peak at 1615 cm-1 is characteristic of an iron-bound
bidentate carbamoyl ligand; for example, the structur-
ally characterized complex [Fe(η2-OCNiPr2)(CF3)(CO)2-
(PPh3)] (1c) has absorptions at 2020, 1949, and 1606
cm-1 (Nujol).8 The diisopropylamino group of 1a fea-
tures chemically inequivalent methyl groups evident as
1
four doublets in the H NMR spectrum. The carbamoyl
carbon gives rise to a 13C{1H} NMR resonance at 197.4
ppm, slightly to higher field of the two chemically
inequivalent terminal carbonyl resonances at δ 220.5
and 212.4. The FAB mass spectrum shows a molecular
ion (m/z ) 629), and substantially abundant isotope
patterns are also observed for fragmentations involving
loss of carbonyl, iodide, and/or carbamoyl ligands.
A slightly more complicated situation arises for the
corresponding bromide derivative: A complex formu-
lated as [Fe(η2-OCNiPr2)Br(CO)2(PPh3)] (1b) (on the
basis of elemental microanalytical and FAB-MS data)
appears to be obtained by treating Li[Fe{C(dO)NiPr2}-
(CO)4] either with preformed Br2PPh3 or alternatively
by sequential addition of bromine and triphenylphos-
phine, and the complex may be isolated in a yield
comparable to 1a . Furthermore, the same species may
also be obtained by treating [Fe(η2-OCNiPr2)(CO)3-
(PPh3)]BF4 (vide infra) with [nBu4N]Br (Scheme 2).
Following cryostatic chromatographic purification (-30
°C), spectroscopic data acquired for the complex 1b
suggest that in the solid state it is isostructural with
1a and 1c, whereas in solution two species coexist in
proportions that are solvent dependent. Thus the in-
frared spectrum of 1b obtained from a Nujol mull
Treating a solution of [Fe(CO)5] in diethyl ether with
LDA, followed by cooling (dry ice/propanone) and addi-
(11) Fischer, E. O.; Schneider, J . Ackermann, Z. Naturforsch. 1984,
39b, 468.
(12) (a) Weller, F.; Petz, W. Z. Anorg. Allg. Chem. 1994, 620, 343.
(b) Petz, W. J . Organomet. Chem. 1993, 456, 85. (c) Boese, R.; Blaser,
D.; Petz, W. Z. Naturforsch. 1988, 43b, 945. (d) Petz, W. Z. Naturforsch.
1981, 36b, 335.
(13) (a)McDermott, G. A.; Dorries, A. M.; Mayr, A. Organometallics
1987, 6, 925. (b) Mayr, A.; McDermott, G. A.; Dorries, A. M. Organo-
metallics 1985, 4, 608.
(14) Luart, D.; le Gall, N.; Salau¨n, J .-E.; Toupet, L.; des Abbayes,
H. Organometallics 1998, 17, 2680.
(15) Anderson, A.; Hill, A. F.; Slawin, A. M. Z.; White, A. J . P.;
Williams, D. J . Inorg. Chem. 1998, 37, 594.
(16) Fischer, H.; Fischer, E. O. J . Organomet. Chem. 1974, 69, C1.
(17) (a) Anderson, S.; Cook, D. J .; Hill, A. F. J . Organomet. Chem.
1993, 463, C3. (b) Anderson, S.; Cook, D. J .; Hill, A. F. Organometallics
1997, 16, 5595.
(18) Fischer, E. O.; Schneider, J .; Neugebauer, D. Angew. Chem.,
Int. Ed. Engl. 1984, 23, 820.

2688 Organometallics, Vol. 23, No. 11, 2004
Anderson et al.
Ta ble 1. Selected 13C a n d 31P NMR Da ta for
Sch em e 2. Syn th esis a n d Isom er ism of
[F e(OCNiP r 2)Br (CO)2(P P h 3)] (1b)
Bid en ta te Ca r ba m oyl a n d Rela ted Com p lexes of
Ir on a
δ(O13CN) 2J (PC) δ(31P)
complex
(ppm)
(Hz)
(ppm)
[Fe(OCNiPr2)I(CO)2(PPh3)]
197.4
194.9
198.4
197.1
196.7
185.9
184.0
204.9
19.4
28.6
19.7
n.r.c
12.9
18.8
23.0
37.5,
21.4
50.0
28.0
32.5
17.7
78.5
38.0
74.6
49.6
53.8
22.4
54.6
105.5,
68.2
74.4
71.1
114.7d
81.8
[Fe(OCNiPr2)Br(CO)2(PPh3)] major
[Fe(OCNiPr2)Br(CO)2(PPh3)] minor
[Fe(OCNiPr2)(CF3)(CO)2(PPh3)]10b,b
[Fe(OCNiPr2)(SnPh3)(CO)2(PPh3)]b
[Fe(OCNiPr2)(CO)3(PPh3)]+b
[Fe(OCNiPr2)(CO)2(PPh3)2]+
[Fe(OCNiPr2)(CO)(dppe)I]
[Fe(OCNiPr2)(CF3)(CO)(dppe)]10b
205.4
260
[Fe(OCC6H2Me3)Br(CO)(dppe)]19
a
Data obtained from saturated solutions in CDCl3 at 25 °C.
Chemical shifts given relative to internal CDCl3 ) 77.0 (13C) or
external H3PO4 ) 0.0 (31P). bCharacterized by X-ray crystal-
c
d
lography. n.r. ) not resolved. J (PAPB) ) 17.3 Hz.
plings for carbonyl ligands in these complexes suggests
that the minor isomer has a facial Fe(CO)2(PPh3)
disposition. The 13C carbonyl resonances due to the
major isomer are broad, and this precludes identification
of 2J (PC); however it is most likely that the major
isomer is either B or C. The two atoms of the carbamoyl
ligand have complimentary π-interactions with the
metal center in that the oxygen is π-basic and the carbon
is π-acidic. It therefore seems most likely that the major
isomer is that with bromide trans to the carbamoyl
carbon, i.e., B (Scheme 2).
reveals two Fe-CO absorptions and one carbamoyl-
associated absorption at 2012, 1964, and 1637 cm-1
,
respectively. However, a spectrum measured in dichloro-
methane solution shows two carbamoyl-associated ab-
sorptions at 1634 and 1624 cm-1. Furthermore, in
addition to the bands due to the terminal carbonyl
ligands at 2017 and 1958 cm-1, a shoulder at ca. 2034
cm-1 was discernible. A spectrum of a solution of 1b in
toluene also showed two major carbonyl peaks at 2012
and 1954 cm-1 and a carbamoyl absorption at 1632
cm-1; however peaks at 2032 and 1615 cm-1 were also
The iodide ligand in 1a and the bromide ligand in
1b are both labile and readily removed by Ag[BF4] in
the presence of CO to provide the yellow salt [Fe(η2-
OCNiPr2)(CO)3(PPh3)]BF4 (2a ‚BF4) in high yield.
The same complex results from the reaction of [Fe(η2-
OCNiPr2)(CF3)(CO)2(PPh3)] with aqueous HBF4, notably
in the absence of added CO, the third carbonyl ligand
arising from hydrolysis of a putative difluorocarbene
intermediate. Spectroscopic data indicate that the
Fe(CO)3 unit adopts a facial geometry and that the
bidentate carbamoyl coordination is retained: Carbon-
13 NMR signals for the carbonyl ligands show distinct
cis (31.4, 26.5) and trans (51.0 Hz) couplings to phos-
phorus, while the signal due to the carbamoyl carbon
1
clearly resolved in this solvent. Data from 31P{1H}, H,
and 13C{1H} NMR measurements also confirm that two
species are present in solution and that they do not
interconvert on the NMR time scales. The 31P{1H} NMR
spectrum of 1b in CDCl3 shows two singlet resonances
at δ 74.6 and 38.0, in an approximate ratio of 1:2. In
toluene-d8 or benzene-d6 at 30 °C, however, the peak
at δ 75.3 represents approximately 5% of the total
phosphorus, the remainder giving rise to a singlet at δ
37.6. The relative proportions of the two species are
invariant from 30 to 65 °C, and above this temperature
range decomposition ensues rapidly. The type of isomer-
ism occurring remains equivocal; however it can be
noted that the position of the 31P NMR resonance for
the minor species (δ ) 74.6) corresponds most closely
with that for 1a (δ ) 78.5) and presumably corresponds
2
once again appears to higher field (δ 185.9, J (PC) )
18.8 Hz) of those due to the carbonyls. Consistent with
the cationic charge and comparatively high ν(CO) values
(CH2Cl2: 2102, 2058, 2023 cm-1), one carbonyl ligand
is labile and readily replaced by triphenylphosphine to
provide trans-[Fe(η2-OCNiPr2)(CO)2(PPh3)2]BF4 (2b‚BF4).
Phosphorus-31 NMR data indicate that the two phos-
phine ligands are mutually trans (δ 54.6), and this is
confirmed by the triplet multiplicity of the 13C reso-
nances due to the carbonyl (δ 214.0 2J (PC) ) 30.1; 211.4
1
to A (Scheme 2). In a similar manner the methine H
resonances for the minor isomer (δ 5.19, 3.47) cor-
respond well with those for 1a (δ 5.09, 3.35), while those
for the major isomer show a less dramatic difference in
chemical shift (δ 4.67, 3.87). Table 1 collects selected
13C and 31P NMR data for related carbamoyl complexes
of iron(II), including three examples that have been
structurally characterized (vide infra). From these data
it is clear that typical cis-2J (PC) couplings for the
carbamoyl ligand lie in the range 13-28 Hz, while the
two examples of trans-2J (PC) couplings are larger at
37.8 and 50.0 Hz. Thus it appears that both isomers
have a cis arrangement of carbamoyl and phosphine
2
2J (PC) ) 21.3) and carbamoyl (δ 184.0, J (PC) ) 23.0
Hz) carbons and the virtual triplicity of the aryl
resonances of the phosphine ligands. The molecular
geometry was confirmed by a crystallographic study of
the 2b‚PF6 salt, which provided crystals suitable for
analysis. The results of this study are summarized in
Table 2 and Figure 1 and are discussed below. Neither
the carbonyl ligands nor the bidentate carbamoyl in
2b‚BF4 is labile. Thus no reaction is observed with the
potential ligands or pro-ligands KI, 1,2-bis(diphenyl-
2
ligands. Furthermore, similar analysis of J (PC) cou-

Dihapto Carbamoyl Complexes of Iron(II)
Organometallics, Vol. 23, No. 11, 2004 2689
Sch em e 3. Liga n d Exch a n ge Rea ction s of th e
Com p lex 1a
F igu r e 1. Molecular structure of the cation (2b+) of
[Fe(OCNiPr2)(CO)2(PPh3)2]PF6. Phenyl groups omitted for
clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Com p lex 2b+
Fe-P
2.3106(12)
1.823(7)
1.985(4)
1.271(7)
1.151(7)
1.485(8)
Fe-P(0A)
Fe-C(9)
2.3106(12)
1.764(7)
1.920(6)
1.136(7)
1.305(7)
1.515(8)
Fe-C(8)
Fe-O(1)
C(2)-O(1)
C(9)-O(9)
N(3)-C(6)
Fe-C(2)
C(8)-O(8)
C(2)-N(3)
N(3)-C(4)
P-Fe-P(0A)
177.95(7)
119.2(3)
37.9(2)
125.8(6)
73.8(3)
C(8)-Fe-C(9)
C(8)-Fe-O(1)
Fe-C(2)-N(3)
Fe-O(1)-C(2)
C(6)-N(3)-C(4)
C(6)-N(3)-C(2)
100.6(3)
102.2(2)
160.4(5)
68.3(3)
117.8(5)
120.7(6)
C(9)-Fe-C(2)
O(1)-Fe-C(2)
O(1)-C(2)-N(3)
O(1)-C(2)-Fe
C(4)-N(3)-C(2)
Ch a r t 2. P r op osed F lu xion a lity in th e Ca tion ic
Com p lex 3+ (P ) P P h 2)
121.5(5)
phosphino)ethane, Na[S2CNMe2], CNC6H3Me2-2,6, or
excess PPh3 over a period of 24 h in dichloromethane
at room temperature. Complex and intractable mixtures
were obtained for the same combinations of reagents
in refluxing tetrahydrofuran.
The complex 2b + can also be obtained as the tri-
fluoroacetate salt 2b‚O2CCF3 from the reaction of
Li[Fe{C(dO)NiPr2}(CO)4] with trifluoroacetic anhydride
and triphenylphosphine at low temperature. In this
synthesis, the time delay between the successive addi-
tion of (CF3CO)2O and PPh3 is crucial. As the delay
increases, so does the proportion of [Fe(η2-OCNiPr2)-
(CF3)(CO)2(PPh3)] (1c)8 at the expense of 2b‚O2CCF3.
This behavior might be a consequence of slow (at -78
°C) decarboxylation of an intermediate of the form
[Fe{C(dO)CF3}{C(dO)NiPr2}(CO)n] (n ) 3, 4, ?) to
provide [Fe{C(dO)NiPr2}(CF3)(CO)n]. The extensive
chemistry of 1c has been discussed elswhere.10b
The reaction of 2a ‚BF4 with dppe [1,2-bis(diphenyl-
phosphino)ethane] leads to substitution of one carbonyl
and the triphenylphosphine ligand to provide [Fe(η2-
OCNiPr2)(CO)2(dppe)]BF4 (3‚BF4) (Scheme 3). The gross
formulation follows from the FAB mass spectrum, which
features a molecular ion and peaks due to the loss of
one and two carbonyl ligands. The yellow salt shows two
terminal carbonyl-associated absorptions in the infrared
(CH2Cl2) spectrum, at 2043 and 1978 cm-1, consistent
with the ionic formulation and a cis-dicarbonyl arrange-
ment. The 31P{1H} NMR spectrum, however, shows only
one resonance (δ 74.0), which is inconsistent with an
octahedral arrangement of the six ligating atoms. These
data are consistent with a trigonal prismatic arrange-
ment (D, Chart 2) or perhaps, more likely, a fluxional
process involving a symmetrical intermediate (E, Chart
2), possibly arising from monodentate coordination of
the carbamoyl ligand. This latter interpretation is
further supported by the broad nature of the H NMR
spectra of recrystallized material, which nevertheless
allow identification of four doublets due to the isopropyl
methyl groups in addition to the multiplet due to the
ethylene chain of the dppe ligand, which is also broad-
ened. Furthermore, only one broad 13C resonance is
observed for the carbonyl ligands.
1
The complex 3+ is also formed as an iodide salt
directly from 1a and dppe in tetrahydrofuran, although
the neutral complex [Fe(η2-OCNiPr2)I(CO)(dppe)] (4) is
also formed as a side product. The two compounds are
readily separable, as the salt 3‚I is only sparingly
soluble in thf and precipitates from the reaction mix-
ture. The various spectroscopic data for 4 indicate a
considerably more π-basic iron center than in 1b includ-
ing a decrease in the frequency of the carbamoyl-
associated infrared peak observed at 1584 cm-1 and the
terminal carbonyl absorption at 1922 cm-1. The geom-
etry at iron, as shown in Scheme 3, follows from the
31P and 13C NMR data. The chemically inequivalent

2690 Organometallics, Vol. 23, No. 11, 2004
Anderson et al.
Sch em e 4
Figu r e 2. Molecular structure of the complex [Fe(OCNiPr2)-
(SnPh3)(CO)2(PPh3)2] (1d ). Phenyl groups omitted for
clarity.
phosphorus nuclei give rise to an AB system [δ 68.2,
105.5, 2J (AB) ) 22.0 Hz] in the 31P NMR spectrum,
while the carbamoyl 13C resonance is evident as a
double-doublet [δ 204.9] with quite distinct couplings
to trans (37.5) and cis (21.4 Hz) phosphorus nuclei.
These data may be compared with those for the related
aroyl complex [Fe(η2-OCC6H2Me3)(CO)(dippe)Br] (Table
1),19 which has been structurally characterized and is
obtained by the facile carbonylation of [Fe(C6H2Me3)-
Br(dippe)] (dippe ) 1,2 bis(diisopropylphosphino)-
ethane).
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for th e Com p lex 1d
Fe-P
2.205(3)
1.722(6)
2.051(4)
1.296(6)
1.169(7)
1.496(7)
Fe-Sn
2.5632(13)
1.787(6)
1.885(5)
1.166(7)
1.302(6)
1.478(7)
Fe-C(10)
Fe-O(1)
Fe-C(11)
Fe-C(2)
C(2)-O(1)
C(11)-O(11)
N(3)-C(4)
C(10)-O(10)
C(2)-N(3)
N(3)-C(7)
Treatment of a solution of Li[Fe{C(dO)NiPr2}(CO)4]
with triphenylchlorostannane provides a thermally
sensitive intermediate presumably of the form [Fe(η2-
OCNiPr2)(SnPh3)(CO)3], which can be converted to the
thermally stable derivative 1d by treatment with tri-
phenylphosphine (Scheme 4). In addition, varying
amounts of [Fe(CO)3(PPh3)2] are obtained, which may
be removed by column chromatography or recrystalli-
zation from dichloromethane and ethanol. Spectroscopic
data suggest the formulation of the compound as a
stannyl-carbamoyl complex of iron(II) [Fe(η2-OCNiPr2)-
(SnPh3)(CO)2(PPh3)] (1d ), and this was confirmed crys-
tallographically (Figure 2, Table 3, vide infra). Variable-
P-Fe-Sn
176.53(7)
116.2(3)
38.1(2)
124.2(5)
77.9(3)
C(10)-Fe-C(11)
C(11)-Fe-O(1)
Fe-C(2)-N(3)
Fe-O(1)-C(2)
C(7)-N(3)-C(4)
C(7)-N(3)-C(2)
99.0(3)
104.7(2)
157.9(4)
64.0(3)
119.7(4)
123.2(5)
C(10)-Fe-C(2)
O(1)-Fe-C(2)
O(1)-C(2)-N(3)
O(1)-C(2)-Fe
C(4)-N(3)-C(2)
117.1(4)
iron center is more π-basic than in the previously
reported and related complex [Fe(η2-OCNiPr2)(CF3)-
(CO)2(PPh3)] (2020, 1953 cm-1),8 reflecting the relative
electronegativies of the CF3 and SnPh3 groups.
The complex [Fe(η2-OCNiPr2)(CF3)(CO)2(PPh3)] reacts
with K[HB(pz)3] (pz ) pyrazol-1-yl) to provide the
ferraoxetene [Fe(κ2-CF2OCNiPr2)(CO){HB(pz)3}] pre-
sumably via the coupling of the carbamoyl ligand with
a putative difluorocarbene complex.10 One motivation
for developing synthetic routes to stannyl-carbamoyl
complexes was to establish whether it might be possible
to generate an electrophilic stannylene ligand which
would be similarly trapped intramolecularly by the
carbamoyl ligand to provide a stannaferraoxetene. Ac-
cordingly, the reaction of the complex 1d with iodine
was investigated as a means of cleaving one or more
Sn-Ph linkages to generate cationic stannylene or
neutral iodostannyl complexes. Such processes have
been implicated in the chemistry of ruthenium stannyl
complexes.20 Reaction of [Fe(η2-OCNiPr2)(SnPh3)(CO)2-
(PPh3)] with iodine however leads to cleavage of the Sn-
Fe bond and formation of [Fe(η2-OCNiPr2)I(CO)2(PPh3)]
(1a ), the alternative preparation of which was described
above.
1
temperature H NMR spectroscopy in the range 225-
335 K failed to provide completely resolved spectra due
to fluxional processes. The static molecular geometry
as depicted in Scheme 4 and Figure 2 has no element
of symmetry, and at no temperature within this range
do the isopropyl substituents become equivalent. At the
hot extreme (335 K), before decomposition ensues, two
methine multiplets and a four-line pattern in the methyl
region are apparent. At the cold extreme (225 K), when
precipitation occurs, two unresolved methine and three
methyl resonances (ratio ca. 1:1:2) are observed. Among
the various conceivable fluxional processes the two most
plausible are (i) dissociation of the bidentate carbamoyl
coordination followed by rotation about the iron-carbon
bond, allowing exchange of methyl sites but retaining
the independence of methine sites, or (ii) rotation about
the C-N bond. The former appears the most plausible
and accounts for the persisting inequivalence of the
methine resonances and the facility of ligand exchange
reactions via the presumed five-coordinate intermediate
(vide infra). The 31P NMR spectrum consists of a singlet
showing coupling to tin, consistent with a trans disposi-
tion of the PPh3 and SnPh3 groups. The infrared data
for the Fe(CO)2 unit (1979, 1908 cm-1) suggest that the
Cr yst a l a n d Molecu la r St r u ct u r e of [F e(η2-
OCNiP r 2)(CO)2(P P h 3)2]P F 6 (2b‚P F 6). The molecular
structure of the complex cation [Fe(η2-OCNiPr2)(CO)2-
(PPh3)2]+ (2b+) is shown in Figure 1, and selected
geometrical parameters are given in Table 2. The
complex and counterion interact only weakly via a pair
(20) Clark, G. R.; Flower, K. R.; Roper, W. R.; Wright, L. J .
Organometallics 1993, 12, 259.
(19) Hermes, A. R.; Girolami, G. S. Organometallics 1988, 7, 394.

Dihapto Carbamoyl Complexes of Iron(II)
Organometallics, Vol. 23, No. 11, 2004 2691
Cr yst a l a n d Molecu la r St r u ct u r e of [F e(η2-
OCNiP r 2)(Sn P h 3)(CO)2(P P h 3)] (1d ). The molecular
geometry of the complex is shown in Figure 2, and
selected geometrical parameters are given in Table 3.
The complex exhibits mirror disorder with in ca. 10%
of the molecules the positions of the PPh3 and SnPh3
groups being reversed. Figure 2 illustrates the major
occupancy conformer and confirms (i) the trans disposi-
tion of stannyl and phosphine groups; (ii) the cis
dicarbonyl arrangement [C(10)-Fe-C(11) 99.0(3)°] with
both carbonyls more strongly bound to the neutral iron
center [Fe-C(10) 1.722(10), Fe-C(11) 1.787(6) Å] than
in the cationic complex 2b+, and (iii) the bidentate
carbamoyl mode of coordination. The iron-phosphorus
separation [2.205(3) Å] compared with that observed in
1c [2.291(4) Å]8 and 2b+ [2.3106(12) Å] suggests that
the coordination of the electropositive stannyl group
trans to the phosphine strengthens the binding relative
to the electronegative CF3 group or the PPh3 group in
the cation 2b+. The iron-tin separation of 2.5632(13)
Å is within the range previously observed for Fe-SnPh3
bond lengths, e.g., [Fe(SnPh3)(CO)2(η-C5H5)] [2.533,
2.540 Å]21 and cis-[Fe(SnPh3)2(CO)4] [2.661(1) Å],22
although longer than observed for the tribromo deriva-
tive [Fe(SnBr3)(CO)2(η-C5H5)] [2.462(2) Å].2323-31
Ta ble 4. Str u ctu r a l Da ta (Å) for Bid en ta te Acyl,
Ar oyl, a n d Ca r ba m oyl Com p lexes of Gr ou p 8
Meta ls
complex
a
b
c
M ) Fe
[Fe(η2-OCMe)I(CO)(PMePh2)2]24
[Fe(η2-OCiPr)I(CO)(PEt3)2]25c
1.83
1.81
1.86
1.87
1.89
1.92
1.23
1.24
1.28
1.25
1.30
1.27
2.25
2.19
1.99
2.04
2.05
1.99
[Fe(η2-OCC6H2Me3)I(CO)(dippe)]19
[Fe(η2-OCNiPr2)(CF3)(CO)2(PPh3)]8
[Fe(η2-OCNiPr2)(SnPh3)(CO)2(PPh3)]
[Fe(η2-OCNiPr2)(CO)2(PPh3)2]+
M ) Ru, Os
[Ru(η2-OCMe)I(CO)(PPh3)2]26
1.88
1.92
1.96
1.96
2.01
2.04
1.92
1.92
1.33
1.21
1.25
1.25
1.22
1.29
1.28
1.28
2.47
2.36
2.34
2.38
2.42
1.96
1.98
2.01
[Ru(η2-OCC6H4Me)Cl(CO)(PPh3)2]26
[Ru(η2-OCNMe2)H2Cl(PiPr3)2]6b
[Ru(η2-OCC6H4NH2)Cl(CO)(PPh3)2]27
[Os(η2-OCC6H4Me)Cl(CH2)(PPh3)2]28
[Fe0(η2-OCHPh)(CO)2(PEt3)2]a,29
[Fe0(η2-OCdCPh2)(CO)2(PEt3)2]a,30
[Fe0(η2-OCdCHCO2Et)(CO)2(PEt3)2]a,31
a
Included as a benchmarks for aldehyde and ketene coordina-
tion; however the iron center is formally zerovalent.
As with 2b + above, interest centers on the
FeOCNiPr2 unit, and pertinent structural features
for this group are summarized in Table 4 along with
those for 1c and bidentate acyl/aroyl complexes of iron.
The nitrogen is clearly trigonal planar, although in
contrast to 2b+, here this is not a crystallographic
requirement. Accordingly, pπ-pπ overlap between N(3)
and C(2) [N(3)-C(2) 1.302(6) Å] is a factor that should
bear on the dimensions of the FeO(1),C(2) metallacycle.
Of the valence bond descriptions contributing to the
bonding descriptions (Chart 1) it is the zwitterionic
(hyperconjugative) contributor that is peculiar to car-
bamoyls as distinct from acyl and aroyl complexes. This
should lead to a lengthening of the bonds within the
metallacycle, and this is clearly evident, with Fe-O(1)
at 2.051(4) Å and C(2)-O(1) at 1.296(6) Å. The bond
between iron and the carbamoyl carbon at 1.885(5) Å is
shorter than in 2b+ and comparable to that in 1c,
of C-H‚‚‚F hydrogen bonds involving a meta-C-H
group on one of the phenyl rings of each PPh3 unit;
[C‚‚‚F], [H‚‚‚F] 3.36, 2.14 Å, [C-H‚‚‚F] 164°. The
complex has crystallographic Cs symmetry about the
plane containing the iron atom, the two CO groups, and
the OCNiPr2 ligand. The “Fe(CO)2(PPh3)2” unit is un-
remarkable, with the equatorial C(8)-Fe-C(9) angle of
100.6(3)° lying between trigonal and octahedral norms.
The two Fe-CO distances differ significantly, with that
trans to the carbamoyl carbon [Fe-C(8) 1.832(7) Å]
being longer than that trans to oxygen [Fe-C(9) 1.764(7)
Å]. Here the difference in bond lengths probably reflects
the π-acceptor and π-donor roles of the trans carbamoyl
carbon and oxygen atoms. The two phosphines are
mutually trans, and the two Fe-P vectors are almost
collinear [P(1)-Fe-P(2) 177.95(7)°].
The main interest in this structure centers on the
iron-carbamoyl interaction, given that the chemistry
outlined above suggests that this may be strong. The
Fe-C(2) separation of 1.920(6) Å clearly suggests some
limited degree of multiple bonding, while the iron
oxygen separation of 1.985(4) Å is somewhat shorter
than that observed for the complex 1c [2.030(2Å]8 and
the acyl complexes collected in Table 4. However, since
2b+ is the only cationic complex in this series, the
stronger binding of the oxygen donor is consistent with
the more electrophilic iron center. The trigonally coor-
dinated nitrogen atom of the carbamoyl ligand is
separated by 1.305(7) Å from the carbamoyl carbon,
which clearly indicates a considerable amount of mul-
tiple bonding (cf. N(3)-C(4) 1.515(8), N(3)-C(6) 1.485(8)
Å]. Thus it appears that each of the canonical forms in
Chart 1 contributes appreciably to the overall bonding.
The positions of the isopropyl methyl groups are such
as to minimize nonbonding interactions with each other
and with the phosphine ligands. Alternative rotational
isomers would lead to substantial and unfavorable steric
conflict between these groups.
(21) Bryan, F. R. J . Chem. Soc. (A) 1967, 192.
(22) Pomeroy, R. K.; Vancea, L.; Calhoun, H. P.; Graham, W. A. G.
Inorg. Chem. 1977, 16, 1508.
(23) Melson, G. A.; Stokey, P. F., Bryan, R. F. J . Chem. Soc. (A)
1970, 2247.
(24) Cardaci, G.; Bellachioma, G.; Zanazzi, P. Organometallics 1988,
7, 172.
(25) (a) Kolbener, P.; Hund, H.-U.; Bosch, H. W.; Sontag, C.; Berke,
H. Helv. Chim. Acta 1990, 73, 2251. (b) Lowe, C.; Hund, H.-U.; Berke,
H. J . Organomet. Chem. 1989, 372, 295. (c) Birk, R.; Berke, H.;
Huttner, G.; Zsolnai, L. J . Organomet. Chem. 1986, 309, C18.
(26) Roper, W. R.; Taylor, G. E.; Waters, J . M.; Wright, L. J . J .
Organomet. Chem. 1979, 182, C46.
(27) Clark, G. R.; Roper, W. R.; Wright, L. J .; Yap, V. P. D.
Organometallics 1997, 16, 5135.
(28) (a) Bohle, D. S.; Clark, G. R.; Rickard, C. E. F.; Roper, W. R.;
Shephard, W. E. B.; Wright, L. J . J . Chem. Soc., Chem. Commun. 1987,
563. (b) Bohle, D. S.; Clark, G. R.; Rickard, C. E. F.; Roper, W. R.;
Wright, L. J . J . Organomet. Chem. 1988, 358, 411.
(29) Birk, R.; Berke, H.; Hund, H.-U.; Evertz, K.; Huttner, G.;
Zsolnai, L. J . Organomet. Chem. 1988, 342, 67.
(30) Birk, R.; Berke, H.; Hund, H.-U.; Huttner, G.; Zsolnai, L.;
Dahlenburg, L.; Behrens, U.; Sielisch, T. J . Organomet. Chem. 1989,
372, 397.
(31) Kandler, H.; Bidell, W.; J a¨nicke, M.; Knickmeier, M.; Veghini,
D.; Berke, H. Organometallics 1998, 17, 960.

2692 Organometallics, Vol. 23, No. 11, 2004
Anderson et al.
isolated and recrystallized from dichloromethane and light
petroleum. Yield: 0.17 g (76%). IR (CH2Cl2): 2021, 1953 ν(CO)
1610 ν(NCO) cm-1. IR (Nujol): 2012, 1948 ν(CO), 1615 ν(NCO)
cm-1. NMR (CDCl3, 25 °C): 1H (270 MHz): δ 0.55, 1.15, 1.19,
consistent with a π-acceptor role for this carbon accom-
modating the increased metal π-basicity of neutral
complexes.
Con clu d in g Rem a r k s. A convenient entry into the
chemistry of carbamoyl complexes of divalent iron has
been established. A feature of the reactivity described
is the apparent tenacity of the bidentate mode of
carbamoyl coordination, at least in ground-state struc-
tures. Nevertheless, the facility of ligand exchange
reactions, the facile isomerism, and the fluxionality of
some of the complexes might be taken to suggest that
monodentate carbamoyl complexes play a role in the
solution chemistry. The importance of bidentate versus
monodentate carbamoyl coordination in preactivation
toward ligand substitution is further supported by the
observation that of all the carbamoyl complexes studied,
the one that is substitution inert, i.e., 2b+, has a
significantly shorter iron-oxygen bond length.
3
1.52 [d × 4, CH3, J (HH) ) 6.6], 3.35, 5.09 [h × 2, 2 H, NCH,
3J (HH) ) 6.6 Hz], 7.19-7.67 [m × 2, 15 H, C6H5]. 13C{1H} (67.5
MHz): δ 220.5 [d, FeCO, 2J (PC) ) 25.0], 212.4 [d, FeCO,
2J (PC) ) 20.8], 197.4 [d, NCO, 2J (PC) ) 19.4 Hz], 134.2-128.3
[C6H5], 55.5, 47.9 (NCH), 21.6, 21.3, 20.4, 19.7 (CH3). 31P{1H}
(109 MHz): δ 78.5. FAB-MS: m/z 629[M]+, 573[M - 2CO]+,
445[FePPh3I]+, 318[FePPh3]+. Anal. Found: C, 51.1; H, 4.6;
N, 2.0. Calcd for C27H29FeINO3P: C, 51.5; H, 4.7; N, 2.2.
Syn th esis of [F e(η2-OCNiP r 2)Br (CO)2(P P h 3)] (1b). Bro-
mine (0.79 mL, 15 mmol) was diluted in diethyl ether (100
mL), and the solution placed in an ice-bath. Triphenylphos-
phine (10.2 g, 38 mmol) was then added slowly, and the
resulting PPh3Br2/PPh3 suspension stirred at room tempera-
ture for 15 min. [Fe(CO)5] (3.00 g, 15 mmol) was placed in a
second Schlenk tube with diethyl ether (50 mL), and a solution
of LDA added dropwise (1.5 mol dm-3, 10.0 mL, 15 mmol). On
completion of the addition, the reaction mixture was cooled
(dry ice/propanone) and the PPh3Br2/PPh3 suspension added
dropwise via a pressure-equalized dropping funnel. The reac-
tion was then left to warm slowly to room temperature. A
yellow precipitate eventually formed, which was isolated by
decanting off the ethereal supernatant. Lithium bromide was
removed by extracting the residue with a mixture of dichloro-
methane and light petroleum (2:1) and filtering the combined
extracts through diatomaceous earth. On removing the solvent
from the filtrate, the product was isolated and further purified
by chromatography (silica gel, CH2Cl2 eluant, -30 °C), followed
by crystallization from a mixture of dichloromethane and light
petroleum. Yield: 7.06 g (79%). NB: Solution data are
complicated by the presence of two isomers, designated A
(minor) and B (major) according to Scheme 2. IR (CH2Cl2):
2034(sh) 2017, 1958 ν(CO), 1634, 1614 ν(NCO) cm-1. IR
Exp er im en ta l Section
Gen er a l P r oced u r es. All manipulations were routinely
carried out under an atmosphere of prepurified dinitrogen
using conventional Schlenk-tube techniques. Solvents were
purified by distillation from an appropriate drying agent
(ethers and paraffins from sodium/potassium alloy with benzo-
phenone as indicator; halocarbons from CaH2).
1H, 13C{1H}, and 31P{1H} NMR spectra were recorded on a
J EOL GNM EX270 NMR spectrometer and calibrated against
internal Me4Si (1H), CDCl3 (13C), or external H3PO4 (31P).
Infrared spectra were recorded using a Perkin-Elmer 1720-X
FT-IR spectrometer. FAB mass spectrometry was carried out
with an Autospec Q mass spectrometer using nitrobenzyl
alcohol as matrix (“M” refers to the cationic complex for salts).
Light petroleum refers to that fraction of bp 40-60 °C.
Elemental microanalyses were carried out by Medac Ltd,
Middlesex, or by the Imperial College Microanalytical Labora-
tory. Solvent of crystallization was confirmed by 1H NMR
integration where appropriate and by X-ray crystallography
in the case of 2b‚PF6.
(toluene): 2032, 2012, 1954 ν(CO), 1632, 1615 ν(NCO) cm-1
.
IR (Nujol): 2012, 1964 ν(CO), 1637 ν(NCO) cm-1. NMR (CDCl3,
25 °C): 1H (270 MHz): δ 0.65, 1.19, 1.14, 12.9 [d × 4, A-CH3,
3
3J (HH) ) 6.6], 1.28, 1.41, 1.46, 1.53 [d × 4, B-CH3, J (HH) )
3
6.6], 3.43, 5.19 [h × 2, A-NCH, J (HH) ) 6.6], 3.87, 4.67 [h ×
2, B-NCH, 3J (HH) ) 6.6 Hz], 7.34-7.69 [m, 15 H, C6H6].
13C{1H} (67.5 MHz): 218.6 [d, A-FeCO, 2J (PC) ) 26.8], 215.2,
212.4 [br × 2, B-FeCO], 210.3 [d, A-FeCO, 2J (PC) ) 21.4],
Syn th esis of [F e(η2-OCNiP r 2)I(CO)2(P P h 3)] (1a ). (a)
[Fe(CO)5] (3.00 g, 15 mmol) was placed in a Schlenk tube with
diethyl ether (50 mL), and a solution of LDA was then added
dropwise (Aldrich: 1.5 mol dm-3, 10.2 mL, 15 mmol). On
completion, the reaction mixture was cooled (dry ice/pro-
panone) and iodine (3.88 g, 15 mmol) added. The iodine
eventually reacted as the reaction mixture was warmed to ca.
-30 °C. When all had dissolved, triphenylphosphine (6.0 g,
23 mmol) was added, and the reaction mixture allowed to
warm slowly to room temperature, causing a purple precipitate
to form, which was isolated by decantation. Lithium iodide was
removed by extraction of the solid with CH2Cl2/light petroleum
(2:1) and filtration of the extracts through diatomaceous earth.
The filtrate was concentrated and chromatographed (silica gel,
CH2Cl2 eluant). The purple fraction was collected, concen-
trated, and diluted with petrol. On cooling (-30 °C), purple
crystals of the product formed. Yield: 6.92 g (72%). (b) The
product can also be prepared using a suspension of preformed
I2PPh3 (15 mmol, obtained by combining I2 (3.88 g) and PPh3
(4.00 g)) in diethyl ether (50 mL). Yield: 8.51 g (88%). (c) To a
solution of [Fe(η2-OCNiPr2)(SnPh3)(CO)2(PPh3)] (1d , 0.30 g,
0.35 mmol) in dichloromethane (50 mL) was added solid iodine
(0.10 g, 0.40 mmol). The mixture was stirred for 4 h and then
freed of volatiles in vacuo. The residue was washed with light
petroleum and then crystallized from a mixture of dichloro-
methane and petroleum ether. Yield: 0.11 g (48%). (d) A
suspension of [Fe(η2-OCNiPr2)(SnPh3)(CO)2(PPh3)] (1d , 0.30 g,
0.35 mmol) and iodine (0.10 g, 0.40 mmol) in diethyl ether (20
mL) was stirred for 1 h. The precipitate that formed was
2
2
198.4 [d, A-NCO, J (PC) ) 19.7], 194.9 [d, B-NCO, J (PC) )
28.6 Hz], 134.2-127.4 [C6H5], 55.5, 47.8 [A-NCH], 53.8, 49.5
[B-NCH], 21.9, 20.3, 20.2, 20.1 [A-CH3], 21.7, 21.4, 20.9, 20.7
[B-CH3]. 31P{1H} (109 MHz): δ 74.6 (A), 38.0 (B). FAB-MS:
m/z 525 [M - 2CO]+, 474 [M - CO,Br]+, 446 [M - 2CO,Br]+,
398 [FePPh3Br]+. Anal. Found: C, 54.1; H, 4.9; N, 2.3. Calcd
for C27H29BrFeNO3P(0.25CH2Cl2): C, 54.2; H, 4.9; N, 2.3.
Syn th esis of [F e(η2-OCNiP r 2)(CO)2(P P h 3)2]X (2b‚X). (a)
X ) BF4. [Fe(η2-OCNiPr2}(CO)2(PPh3)]BF4 (2a ‚BF4, 0.20 g, 0.30
mmol)10b was dissolved in thf (20 mL) and triphenylphosphine
added (0.13 g, 0.50 mmol). The reaction mixture was then
heated under reflux for 1 h, and on completion the thf was
removed under reduced pressure. Diethyl ether (30 mL) was
added to the residue, and upon ultrasonic trituration, a yellow
precipitate was produced, which was isolated by decantation.
This crude product was then recrystallized from a mixture of
dichloromethane and light petroleum (-30 °C). Yield: 0.16 g
(58%). (b) X ) PF6. A solution of [Fe(η2-OCNiPr2)(CO)2-
(PPh3)2](CF3CO2) (2b‚O2CCF3) (1.00 g, 1.14 mmol)10b in dichloro-
methane (15 mL) was treated with concentrated aqueous HPF6
(0.34 g, 0.46 mL, 2.4 mmol) followed by light petroleum (8 mL).
The mixture was stirred for 15 min and then left to stand
without stirring overnight. The well-formed yellow crystals
were isolated by filtration, washed with diethyl ether, and
dried in vacuo. IR (CH2Cl2): 2039, 1968 ν(CO) 1605 ν(NCO)
cm-1. IR (Nujol): 2026, 1960 ν(CO), 1612 ν(NCO) cm-1. NMR
(CDCl3, 25 °C): 1H (270 MHz): δ 0.09, 1.00 [d × 2, 12 H, CH3],

Dihapto Carbamoyl Complexes of Iron(II)
Organometallics, Vol. 23, No. 11, 2004 2693
2
3.06, 5.16 [h × 2, 2 H, NCH], 7.33-7.53 [m, 30 H,C6H5].
20.2 (CH3). 31P{1H} (109 MHz): δ 68.2, 105.5 [AB, J (AB) )
13C{1H} (67.5 MHz): δ 214.0 [t, FeCO, J (P2C) ) 30.1], 211.4
22.0 Hz]. FAB-MS: m/z 709 [M - CO]+, 610 [M - I]+, 582 [M
- CO,I]+, 453[Fe(dppe)]+. Anal. Found: C, 51.7; H, 4.6; N. 1.4.
Calcd for C34H38FeINO2P2‚CH2Cl2: C, 51.8; H, 4.8; N, 1.7.
P r ep a r a tion of [F e(η2-OCNiP r 2)(Sn P h 3)(CO)2(P P h 3)]
(1d ). To a solution of [Fe(CO)5] (3.00 g, 15 mmol) in diethyl
ether (50 mL) was added LiNiPr2 (1.5 mol dm-3, 10.2 mL, 15
mmol). The mixture was then cooled (dry ice/propanone) and
treated with ClSnPh3 (5.90 g, 15 mmol) and the mixture
allowed to warm with stirring until the ClSnPh3 had dissolved,
after which time PPh3 (6.00 g, 23 mmol) was added The
mixture was stirred at room temperature for 12 h, after which
time the supernatant liquor was decanted from the red-orange
precipitate and discarded. Lithium chloride was removed by
extracting the residue with a mixture of CH2Cl2 and petroleum
ether (2:1). The combined extracts were filtered through
diatomaceous earth and concentrated in vacuo to effect
crystallization of the product. In the occasional event that the
crude product was contaminated with [Fe(CO)3(PPh3)2] [ν(CO)
1880 cm-1], the material could be further purified by chroma-
tography [silica gel, ethyl ethanoate as eluant] or recrystalli-
zation from a mixture of dichloromethane and ethanol. Yield:
4.81 g (37%). IR (CH2Cl2): 1979, 1908 ν(CO) 1585 ν(NCO)
cm-1. IR (Nujol): 1973, 1907 ν(CO), 1586 ν(NCO) cm-1. NMR
(CDCl3, 25 °C): 1H (270 MHz): δ 0.60 [br, 12 H, CH3], 2.93,
4.70 [h × 2, 2 H, NCH], 7.10-7.60 [m, 30 H, C6H5]. 13C{1H}
2
2
2
[t, FeCO, J (P2C) ) 21.3], 184.0 [t, OCN, J (P2C) ) 23.0 Hz],
133.6-129.4 (C6H5), 56.2, 49.6 (NCH), 21.3, 19.2 (CH3). 31P{1H}
(109 MHz): δ 54.6. FAB-MS: m/z 764 [M]+, 708 [M - 2CO]+,
580 [Fe(PPh3)2]+. Anal. Found C, 53.0; H, 4.4; N, 1.3. C45H44F6-
FeNO3P3‚(2CH2Cl2) requires C, 52.3; H, 4.5; N, 1.3. Dichloro-
1
methane solvate confirmed by H NMR and X-ray diffraction.
Crystal data for 2b‚PF6: [C45H44NO3P2Fe](PF6)‚2CH2Cl2, M
) 1079.42, monoclinic, P21/m (no. 11), a ) 9.349(2) Å, b )
24.347(3) Å, c ) 10.980(2) Å, â ) 96.467(14)°, V ) 2483.4(6)
Å3, Z ) 2 (Cs symmetry), Dc ) 1.444 g cm-3, µ(Mo KR) ) 0.68
mm-1, T ) 223 K, yellow plates; 3134 independent measured
reflections, F2 refinement, R1 ) 0.049, wR2 ) 0.105, 2267
independent observed absorption corrected reflections [|Fo| >
4σ(|Fo|), 2θmax ) 45°], 277 parameters. CCDC 232296.
Rea ction of [F e(η2-OCNiP r 2)I(CO)2(P P h 3)] w ith d p p e:
Syn th esis of (a ) [F e(η2-OCNiP r 2)(CO)2(d p p e)]I (3‚I) a n d
(b) [F e(η2-OCNiP r 2)I(CO)(d p p e)] (4). [Fe(η2-OCNiPr2)(CO)2-
(PPh3)I] (1a , 0.20 g, 0.31 mmol) and 1,2-bis(diphenylphos-
phino)ethane (0.13 g, 0.31 mmol) were placed in a Schlenk
tube, and the tube was evacuated and refilled with nitrogen.
Tetrahydrofuran (30 mL) was added and the reaction mixture
stirred at room temperature overnight, resulting in a yellow
precipitate and a purple supernatant. On allowing the pre-
cipitate to settle, the thf liquor was decanted off, the residue
washed with thf (5 mL), and the product [Fe(η2-OCNiPr2)(CO)2-
(dppe)]I isolated. Yield: 0.09 g (37%). IR (CH2Cl2): 2043, 1978
ν(CO), 1626 ν(NCO) cm-1. IR (Nujol): 2030, 1969 ν(CO), 1627
ν(NCO) cm-1. NMR (CDCl3, 25 °C): 1H (270 MHz): δ 0.96,
1.41, 1.55, 1.84 [d × 4, 12 H, CH3, 3J (HH) ) 6.6], 2.98, 3.39
2
(67.5 MHz): δ 218.0 [d, FeCO, J (PC) not resolved], 196.7 [d,
OCN, 2J (PC) ) 12.9], 145.7 [C1(SnPh), 3J (PC) ) 5.1, 1J (119SnC)
) 258], 137.2 [C2,6(SnPh), 2J (119SnC) ) 32.9], 133.8-128.2
[PC6H5 + C4(SnC6H5)], 127.4 [C3,5(SnC6H5), J (119SnC) ) 37.5
3
Hz], 54.4, 47.5 (NCH), 20.7, 20.1 (CH3). 31P{1H} (109 MHz): δ
53.8 [2J (119SnP) ) 637 Hz]. FAB-MS: m/z 851 [M]+, 795 [M -
2CO]+, 720 [M - 2CO - Ph]+, 668 [Fe(SnPh3)(PPh3)]+, 563
[M - CO - PPh3]+, 535 [M - 2CO - PPh3]+, 351 [SnPh3]+,
318 [FePPh3]+. Anal. Found: C, 63.5; H, 4.9; N. 1.5. Calcd for
3
[m(br) × 2, 4 H, PCH2], 3.63, 4.79 [h × 2, 2 H, NCH, J (HH)
) 6.6 Hz], 7.02, 7.57 [m × 2, 20 H, C6H5]. 13C{1H} (67.5 MHz):
2
δ 208.5 [br, FeCO], 193.4 [d, OCN, J (PC) ) 14.3 Hz], 133.3-
129.4 (C6H5), 55.2, 49.6 (NCH), 29.5 [m(br), PCH2], 21.0, 20.1
(CH3). 31P{1H} (109 MHz): δ 74.1. FAB-MS: m/z 638 [M]+,
610 [M - CO]+, 582 [M - 2CO]+, 453 [Fe(dppe)]+. Anal: Found
C, 52.4; H, 4.6; N. 1.7. Calcd for C35H38FeINO3P2‚0.5CH2Cl2:
C, 52.8, H 4.9; N 1.7. (b) The solvent was removed from the
thf supernatant above, under vacuum, and diethyl ether (30
mL) added to the residue. On ultrasonic trituration, a pre-
cipitate was formed, and after decanting off the diethyl ether,
the product [Fe(η2-OCNiPr2)I(CO)(dppe)] was isolated. Yield:
0.08 g (34%). IR (CH2Cl2): 1917 ν(CO) 1593 ν(NCO) cm-1. IR
(Nujol): 1922 ν(CO), 1584 ν(NCO) cm-1. NMR (CDCl3, 25 °C):
1H (270 MHz): δ 0.77, 1.19, 1.37, 1.57 [d × 4, 12 H, CH3,
3J (HH) ) 6.6], 2.40, 2.71 [m(br) × 2, 4 H, PCH2], 3.49, 5.30 [h
× 2, 2 H, NCH, 3J (HH) ) 6.6 Hz], 7.02, 7.57 [m × 2, 20 H,
C
C
45H44FeNO3PSn: C, 63.4; H, 5.2; N, 1.6. Crystal data for 1d :
45H44NO3PSnFe‚CH2Cl2, M ) 937.25, monoclinic, P21/n (no.
14), a ) 10.527(7) Å, b ) 19.299(11) Å, c ) 21.567(7) Å, â )
93.97(3)°, V ) 4371(4) Å3, Z ) 4, Dc ) 1.424 g cm-3, µ(Mo KR)
) 1.10 mm-1, T ) 293 K, orange-yellow blocks; 5689 inde-
pendent measured reflections, F2 refinement, R1 ) 0.044, wR2
) 0.123, 4454 independent observed absorption corrected
reflections [|Fo| > 4σ(|Fo|), 2θmax ) 45°], 445 parameters. CCDC
232295.
Su p p or tin g In for m a tion Ava ila ble: Full details of the
crystal structure determinations and ORTEP representations
for 2b‚PF6 and 1d . This material is available free of charge
via the Internet at http://pubs.acs.org.
2
C6H6]. 13C{1H} (67.5 MHz): δ 223.9 [d, FeCO, J (PC) ) 28.5],
2
204.9 [dd, OCN, J (PC) ) 37.5, 21.4 Hz], 135.2-127.7 (C6H5),
54.9, 47.4 (NCH), 32.2, 28.5 (dd × 2, PCH2), 21.6, 21.1, 20.8,
OM0306933