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The synthesis and crystal structure of penta­carbonyl(pyrrolidin-2-yl­idene)­chromium(0), [Cr(C4H7N)(CO)5], is reported. The compound shows strong interaction between the lone pair at nitro­gen and the carbene C atom, and weak intermolecular hydrogen bonds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100004479/qa0221sup1.cif
Contains datablocks III, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100004479/qa0221IIIsup2.hkl
Contains datablock III

CCDC reference: 145625

Comment top

Fischer aminocarbene complexes are versatile reagents for stereoselective organic synthesis (Dötz, 1984; Hegedus, 1995; Wulff, 1995; Barluenga, 1996). Cycloalkylidene complexes are potential precursors for spiro-cycloaddition and annelation reactions. Oxacyclopentylidene complexes are readily accessible by cyclization of alkynols at the metal template (Dötz et al., 1987) and can be transformed into azacyclopentylidene (pyrrolidinylidene) complexes by an efficient one-pot procedure recently described by us (Haase & Dötz, 1999). The protocol is characterized by smooth conditions and provides the first generally applicable (Haase et al., 1999; Dötz et al., 1997) access to N-unprotected azacyclopentylidene complexes.

The structure was determined by X-ray crystallography to study the ring conformation and bond lengths in the absence of steric hindrance induced by substituents at the N atom. Complex (III) shows a 3E conformation, with an angle of 11.3 (3)° between the C4/N1/C1/C2 and C4/C3/C2 planes, C3 lying 0.181 (4) Å above the C4/N1/C1/C2 plane. Characteristic details are the planarity at the N and the carbene C atom which indicates the strong π-interaction between these atoms, supported by the very short nitrogen–carbene bond of 1.296 (2) Å and the minor distortions from an exact trigonal environment of the Nsp2 atom [C1—N1—H1 121.7 (14)°]. In contrast, known N-methyl-substituted azacyclopentylidene complexes show major steric interactions between the pentacarbonylchromium fragment and the N-methyl group resulting in C1—N1—NCH3 angles of 125.8 (Dötz et al., 1997) or 127.7° (Dötz et al., 1999) and longer nitrogen–carbene bonds (1.313 and 1.3059 Å, respectively). Complex (III) shows almost ideal octahedral coordination around the Cr atom. The Cr—C distance of the trans-carbonyl group is between 0.014 and 0.035 Å shorter than to the cis-carbonyl ligands, as expected for Fischer carbene complexes (Fischer, 1974). The crystal structure is stabilized by weak intermolecular hydrogen bonds [2.26 (2) Å] between the N1 H atom and the O1Ei atom of a carbonyl ligand [symmetry code: (i) x + 1, y, z].

Experimental top

Pentacarbonyl(oxacyclopentylidene)chromium(0), (I), was subjected to ammonolysis and the intermediate formed, i.e. acyclic aminocarbene complex (II), was recyclized under Mitsunobu conditions overnight. Recrystallization of the pure product from n-pentane/dichloromethane yielded complex (III) as yellow crystals in 65% overall yield.

Refinement top

All H atoms were located by a difference Fourier synthesis and refined with fixed individual displacement parameters [Uiso(H) = 1.2Ueq(C or N)], using a riding model with C—H = 0.99 Å, while the coordinates of the H(N) atom were refined.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-Plus (Sheldrick, 1991); software used to prepare material for publication: SHELXL97.

2-Azacyclopentylidene(pentacarbonyl)chromium(0) top
Crystal data top
[Cr(C4H7N)(CO)5]Dx = 1.637 Mg m3
Mr = 261.16Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121Cell parameters from 14785 reflections
a = 6.7152 (3) Åθ = 3.3–27.3°
b = 10.1507 (5) ŵ = 1.08 mm1
c = 15.5447 (9) ÅT = 123 K
V = 1059.59 (9) Å3Plates, yellow
Z = 40.40 × 0.10 × 0.05 mm
F(000) = 528
Data collection top
Nonius KappaCCD
diffractometer
2402 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.035
Graphite monochromatorθmax = 28.3°, θmin = 3.3°
rotation in ϕ and ω, 2° scansh = 88
14711 measured reflectionsk = 1313
2630 independent reflectionsl = 2020
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.024H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.057 w = 1/[σ2(Fo2) + (0.0307P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max = 0.001
2630 reflectionsΔρmax = 0.25 e Å3
148 parametersΔρmin = 0.22 e Å3
1 restraintAbsolute structure: Flack (1983); 1097 Friedel pairs
Primary atom site location: PattersonAbsolute structure parameter: 0.015 (17)
Crystal data top
[Cr(C4H7N)(CO)5]V = 1059.59 (9) Å3
Mr = 261.16Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 6.7152 (3) ŵ = 1.08 mm1
b = 10.1507 (5) ÅT = 123 K
c = 15.5447 (9) Å0.40 × 0.10 × 0.05 mm
Data collection top
Nonius KappaCCD
diffractometer
2402 reflections with I > 2σ(I)
14711 measured reflectionsRint = 0.035
2630 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.024H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.057Δρmax = 0.25 e Å3
S = 1.02Δρmin = 0.22 e Å3
2630 reflectionsAbsolute structure: Flack (1983); 1097 Friedel pairs
148 parametersAbsolute structure parameter: 0.015 (17)
1 restraint
Special details top

Experimental. Absorption correction using SHELXTL-Plus and MULABS (Blessings algorithm) don't improve the data.

dx = 39.880 (4) mm; 2 x 90 sec., 2 °., 279 frames; mos.= 0.744 (3)

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cr10.32622 (4)0.31481 (3)0.307789 (17)0.01860 (8)
C1A0.2411 (3)0.19876 (18)0.22144 (11)0.0241 (4)
O1A0.1875 (2)0.12955 (14)0.16777 (8)0.0330 (3)
C1B0.2120 (3)0.45717 (19)0.24477 (11)0.0238 (4)
O1B0.14254 (19)0.54057 (14)0.20615 (8)0.0342 (3)
C1C0.4376 (3)0.17510 (19)0.37240 (11)0.0231 (4)
O1C0.5022 (2)0.08924 (14)0.41127 (9)0.0336 (3)
C1D0.5750 (3)0.34191 (18)0.25094 (11)0.0235 (4)
O1D0.7233 (2)0.35719 (14)0.21661 (9)0.0346 (3)
C1E0.0839 (3)0.29405 (17)0.36800 (11)0.0214 (4)
O1E0.06250 (19)0.28133 (13)0.40525 (9)0.0278 (3)
N10.5664 (2)0.44329 (16)0.45095 (10)0.0258 (3)
H10.652 (3)0.3807 (17)0.4462 (13)0.031*
C10.4092 (3)0.44857 (17)0.40267 (11)0.0193 (3)
C20.2968 (3)0.56986 (18)0.43046 (13)0.0293 (4)
H2A0.16920.54470.45780.035*
H2B0.26770.62640.38010.035*
C30.4276 (3)0.6433 (2)0.49435 (15)0.0434 (6)
H3A0.35140.66640.54670.052*
H3B0.48090.72510.46850.052*
C40.5952 (3)0.54790 (19)0.51559 (12)0.0270 (4)
H4A0.72720.59040.50920.032*
H4B0.58200.51290.57480.032*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cr10.01866 (12)0.01926 (13)0.01787 (12)0.00060 (11)0.00123 (11)0.00015 (11)
C1A0.0250 (8)0.0250 (9)0.0222 (8)0.0026 (8)0.0038 (7)0.0040 (8)
O1A0.0415 (8)0.0335 (7)0.0241 (6)0.0022 (7)0.0013 (6)0.0086 (6)
C1B0.0217 (10)0.0284 (9)0.0214 (8)0.0007 (8)0.0031 (7)0.0022 (8)
O1B0.0342 (8)0.0358 (7)0.0326 (8)0.0070 (6)0.0015 (6)0.0116 (6)
C1C0.0219 (8)0.0250 (9)0.0223 (8)0.0026 (8)0.0047 (7)0.0036 (8)
O1C0.0377 (8)0.0296 (7)0.0333 (8)0.0066 (6)0.0025 (6)0.0083 (6)
C1D0.0291 (10)0.0228 (10)0.0185 (8)0.0006 (8)0.0011 (8)0.0007 (7)
O1D0.0289 (7)0.0413 (8)0.0338 (8)0.0016 (6)0.0102 (6)0.0036 (6)
C1E0.0254 (8)0.0183 (9)0.0206 (8)0.0015 (7)0.0039 (7)0.0008 (7)
O1E0.0220 (6)0.0305 (7)0.0310 (7)0.0004 (5)0.0058 (5)0.0025 (6)
N10.0229 (8)0.0263 (8)0.0281 (8)0.0064 (7)0.0019 (7)0.0058 (7)
C10.0202 (8)0.0201 (9)0.0175 (8)0.0018 (7)0.0022 (7)0.0037 (7)
C20.0279 (11)0.0266 (10)0.0333 (10)0.0050 (8)0.0038 (8)0.0032 (8)
C30.0421 (13)0.0421 (13)0.0461 (14)0.0149 (10)0.0152 (10)0.0200 (11)
C40.0280 (9)0.0280 (10)0.0249 (9)0.0003 (8)0.0043 (8)0.0047 (8)
Geometric parameters (Å, º) top
Cr1—C1A1.8751 (19)N1—C41.475 (2)
Cr1—C1E1.8892 (18)N1—H10.862 (15)
Cr1—C1C1.892 (2)C1—C21.507 (3)
Cr1—C1B1.9069 (19)C2—C31.521 (3)
Cr1—C1D1.9097 (19)C2—H2A0.9900
Cr1—C12.0808 (18)C2—H2B0.9900
C1A—O1A1.148 (2)C3—C41.521 (3)
C1B—O1B1.138 (2)C3—H3A0.9900
C1C—O1C1.146 (2)C3—H3B0.9900
C1D—O1D1.140 (2)C4—H4A0.9900
C1E—O1E1.148 (2)C4—H4B0.9900
N1—C11.296 (2)
C1A—Cr1—C1E91.26 (7)C4—N1—H1120.1 (14)
C1A—Cr1—C1C91.70 (8)N1—C1—C2105.99 (15)
C1E—Cr1—C1C89.66 (7)N1—C1—Cr1126.99 (13)
C1A—Cr1—C1B89.18 (8)C2—C1—Cr1127.01 (12)
C1E—Cr1—C1B89.57 (7)C1—C2—C3107.37 (15)
C1C—Cr1—C1B178.84 (8)C1—C2—H2A110.2
C1A—Cr1—C1D91.49 (8)C3—C2—H2A110.2
C1E—Cr1—C1D177.25 (8)C1—C2—H2B110.2
C1C—Cr1—C1D90.44 (8)C3—C2—H2B110.2
C1B—Cr1—C1D90.29 (8)H2A—C2—H2B108.5
C1A—Cr1—C1177.43 (8)C2—C3—C4104.89 (16)
C1E—Cr1—C187.27 (7)C2—C3—H3A110.8
C1C—Cr1—C190.39 (7)C4—C3—H3A110.8
C1B—Cr1—C188.71 (7)C2—C3—H3B110.8
C1D—Cr1—C189.98 (7)C4—C3—H3B110.8
O1A—C1A—Cr1178.78 (16)H3A—C3—H3B108.8
O1B—C1B—Cr1178.80 (17)N1—C4—C3102.31 (15)
O1C—C1C—Cr1178.81 (16)N1—C4—H4A111.3
O1D—C1D—Cr1179.44 (18)C3—C4—H4A111.3
O1E—C1E—Cr1179.41 (15)N1—C4—H4B111.3
C1—N1—C4118.15 (15)C3—C4—H4B111.3
C1—N1—H1121.7 (14)H4A—C4—H4B109.2
C1E—Cr1—C1A—O1A90 (8)C1D—Cr1—C1E—O1E48 (16)
C1B—Cr1—C1A—O1A0 (8)C1—Cr1—C1E—O1E47 (15)
C1D—Cr1—C1A—O1A90 (8)C4—N1—C1—C20.1 (2)
C1—Cr1—C1A—O1A35 (9)C4—N1—C1—Cr1179.01 (13)
C1A—Cr1—C1B—O1B4 (8)C1E—Cr1—C1—N1123.34 (17)
C1E—Cr1—C1B—O1B87 (8)C1C—Cr1—C1—N133.70 (17)
C1C—Cr1—C1B—O1B136 (7)C1B—Cr1—C1—N1147.03 (17)
C1D—Cr1—C1B—O1B96 (8)C1D—Cr1—C1—N156.75 (17)
C1A—Cr1—C1C—O1C45 (8)C1A—Cr1—C1—C20.2 (17)
C1E—Cr1—C1C—O1C46 (8)C1E—Cr1—C1—C255.34 (16)
C1B—Cr1—C1C—O1C95 (9)C1C—Cr1—C1—C2144.98 (16)
C1D—Cr1—C1C—O1C136 (8)C1B—Cr1—C1—C234.29 (16)
C1—Cr1—C1C—O1C134 (8)C1D—Cr1—C1—C2124.58 (16)
C1A—Cr1—C1D—O1D18 (20)N1—C1—C2—C37.2 (2)
C1C—Cr1—C1D—O1D74 (20)Cr1—C1—C2—C3173.85 (14)
C1B—Cr1—C1D—O1D107 (20)C1—C2—C3—C411.1 (2)
C1A—Cr1—C1E—O1E135 (15)C1—N1—C4—C36.9 (2)
C1C—Cr1—C1E—O1E44 (15)C2—C3—C4—N110.4 (2)
C1B—Cr1—C1E—O1E135 (15)

Experimental details

Crystal data
Chemical formula[Cr(C4H7N)(CO)5]
Mr261.16
Crystal system, space groupOrthorhombic, P212121
Temperature (K)123
a, b, c (Å)6.7152 (3), 10.1507 (5), 15.5447 (9)
V3)1059.59 (9)
Z4
Radiation typeMo Kα
µ (mm1)1.08
Crystal size (mm)0.40 × 0.10 × 0.05
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
14711, 2630, 2402
Rint0.035
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.024, 0.057, 1.02
No. of reflections2630
No. of parameters148
No. of restraints1
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.25, 0.22
Absolute structureFlack (1983); 1097 Friedel pairs
Absolute structure parameter0.015 (17)

Computer programs: COLLECT (Nonius, 1998), DENZO-SMN (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL-Plus (Sheldrick, 1991), SHELXL97.

 

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