Low-temperature tris(tert-butyl 3-oxo­butan­oato)­iron(III)

The low-temperature (173 K) structure of the title complex, [Fe(C₈H₁₃O₃)₃], a metal-organic chemical vapour deposition (MOCVD) precursor, has been analyzed. The Fe atom is octahedrally coordinated and the three chelate rings are found to be significantly non-planar, adopting a half-chair conformation with the Fe atom out of the plane.

S1. Comment

We have been exploring the use of metalorganic (MO) complexes as precursors for chemical vapour deposition (CVD) of thin films (Patnaik et al., 1996). In the title compound, (I), an iron complex, the ligand has tert-butoxy as the terminal group on one side and methyl on the other. The bulky groups render the complex more volatile, a very desirable quality for CVD.

The coordination geometry is essentially octahedral. The Fe—O bond lengths range from 1.945 (3) to 2.048 (3) Å and the O—Fe—O bond angles within the chelate rings range from 86.9 (1) to 88.0 (1)°. The bite O···O distances are comparable to those observed in similar iron complexes (Pfluger & Haradem, 1983; Soling, 1976). The six-membered chelate rings are significantly non-planar and adopt a half-chair conformation with the Fe atom out of the plane by about 0.3 Å, unlike the boat conformation observed other iron complexes (Clegg, 1985; Calogero et al., 1997). It is noted that the average Fe—O lengths in each chelate ring are 1.948 and 2.039 Å, the shorter length being on the same side as the methyl group.

The angles between the best planes fitted through the six atoms of each ring are 100, 91 and 105°. The intramolecular short contacts are only of the C—H···O type, involving the tertiary butyl C atom and the chelate ring O atom. The distances range from 2.881 (7) to 2.991 (6) Å and the C—H···O angles vary from 112.3 (3) to 118.1 (3)°. There are no significant intermolecular C—H···O interactions and the packing is dominated by van der Waals interactions.

S2. Experimental

The complex was synthesized by dissolving tert-butyl acetoacetate (9.8 ml, 60 mmol) and potassium acetate (5.88 g, 60 mmol) in ethanol (30 ml). This was followed by the addition of iron(III) chloride (5.4 g, 20 mmol) dissolved in water (20 ml). The mixture was stirred under ice-cold conditions for 6 h and the precipitate which formed was filtered off, washed with water and recrystallized from cyclohexane. Single crystals were obtained by slow evaporation from a solution in cyclohexane.

S3. Refinement

The positional parameters of all the H atoms were calculated geometrically and fixed with U(H) = 1.2U_eq(parent atom).

Computing details

Data collection: CrystalClear (Rigaku Corporation, 1999); cell refinement: CrystalClear (Rigaku, 1999); data reduction: CrystalClear; program(s) used to solve structure: SHELXS86 (Sheldrick, 1985); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: WinGX (Farrugia, 1998).

tris(tert-butyl-3-oxobutanoato)iron(III)

Crystal data

[Fe(C8H13O3)3]	F(000) = 1124
Mr = 527.4	Dx = 1.278 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71069 Å
a = 9.598 (3) Å	Cell parameters from 10463 reflections
b = 16.056 (4) Å	θ = 2.5–28.5°
c = 18.112 (4) Å	µ = 0.60 mm^−1
β = 100.88 (2)°	T = 173 K
V = 2741 (1) Å^3	Prism, red
Z = 4	0.15 × 0.15 × 0.10 mm

Data collection

Rigaku AFC8 coupled with mercury CCD diffractometer	3190 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.06
Graphite monochromator	θmax = 30.6°, θmin = 2.5°
ω scans	h = 0→13
31072 measured reflections	k = −22→22
7261 independent reflections	l = −24→23

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.062	w = 1/[σ^2(Fo^2) + (0.0144P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.173	(Δ/σ)max = 0.007
S = 0.91	Δρmax = 0.54 e Å^−3
7261 reflections	Δρmin = −0.56 e Å^−3
319 parameters

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Fe1	0.80599 (6)	0.23407 (4)	0.36506 (3)	0.03710 (17)
O7	0.7703 (3)	0.14036 (19)	0.42707 (16)	0.0424 (7)
O9	1.2082 (3)	0.1857 (2)	0.49675 (16)	0.0468 (8)
O3	0.8416 (3)	0.09677 (19)	0.17076 (16)	0.0440 (7)
O5	0.7753 (3)	0.31212 (19)	0.44253 (16)	0.0438 (7)
O4	0.8704 (3)	0.33228 (18)	0.30941 (15)	0.0390 (7)
O8	1.0169 (3)	0.22319 (19)	0.41152 (15)	0.0416 (7)
O6	0.9472 (3)	0.46255 (17)	0.29270 (16)	0.0431 (7)
O2	0.6174 (3)	0.24213 (18)	0.30226 (14)	0.0380 (6)
O1	0.8590 (3)	0.15981 (18)	0.28328 (16)	0.0398 (7)
C12	0.9721 (5)	0.4433 (3)	0.2163 (2)	0.0396 (10)
C20	1.3070 (4)	0.2398 (3)	0.4636 (2)	0.0400 (9)
C14	0.8346 (5)	0.4206 (3)	0.1656 (2)	0.0484 (11)
H14A	0.7994	0.368	0.1825	0.073*
H14B	0.8501	0.4144	0.114	0.073*
H14C	0.7647	0.4647	0.1674	0.073*
C1	0.5783 (4)	0.2273 (3)	0.2305 (2)	0.0359 (8)
C2	0.6555 (4)	0.1823 (3)	0.1881 (2)	0.0417 (10)
H2	0.6174	0.1744	0.1363	0.05*
C7	1.0941 (5)	0.1290 (3)	0.1993 (3)	0.0479 (11)
H7A	1.071	0.1672	0.1566	0.072*
H7B	1.1885	0.1051	0.2006	0.072*
H7C	1.0932	0.1595	0.2461	0.072*
C4	0.9856 (5)	0.0600 (3)	0.1911 (3)	0.0411 (10)
C8	0.4354 (4)	0.2607 (3)	0.1958 (2)	0.0433 (10)
H8A	0.3622	0.2316	0.217	0.065*
H8B	0.4188	0.2519	0.1413	0.065*
H8C	0.4317	0.3204	0.2065	0.065*
C18	0.9926 (5)	0.1279 (3)	0.5085 (2)	0.0449 (10)
H18	1.0421	0.1028	0.5534	0.054*
C3	0.7892 (4)	0.1472 (3)	0.2179 (2)	0.0378 (9)
C17	0.8514 (5)	0.1097 (3)	0.4859 (2)	0.0390 (9)
C10	0.8793 (5)	0.4339 (3)	0.4057 (2)	0.0433 (10)
H10	0.9095	0.4889	0.4202	0.052*
C19	1.0691 (4)	0.1820 (3)	0.4685 (2)	0.0374 (9)
C13	1.0846 (5)	0.3762 (3)	0.2201 (3)	0.0514 (12)
H13A	1.1636	0.3884	0.2614	0.077*
H13B	1.1193	0.3748	0.1726	0.077*
H13C	1.0435	0.322	0.2287	0.077*
C21	1.3078 (5)	0.2154 (4)	0.3840 (3)	0.0649 (15)
H21A	1.3196	0.1549	0.381	0.097*
H21B	1.3864	0.2434	0.3666	0.097*
H21C	1.2178	0.2318	0.3521	0.097*
C11	0.8986 (4)	0.4050 (3)	0.3346 (2)	0.0392 (9)
C16	0.7988 (6)	0.4231 (3)	0.5290 (3)	0.0523 (12)
H16A	0.6995	0.4166	0.5341	0.078*
H16B	0.8232	0.4825	0.5307	0.078*
H16C	0.8603	0.3941	0.5703	0.078*
C5	0.9941 (5)	0.0072 (4)	0.1226 (3)	0.0636 (15)
H5A	0.9225	−0.037	0.1177	0.095*
H5B	1.0887	−0.0177	0.1283	0.095*
H5C	0.9764	0.0423	0.0775	0.095*
C22	1.2692 (6)	0.3291 (3)	0.4708 (3)	0.0604 (13)
H22A	1.1799	0.3412	0.4364	0.091*
H22B	1.3446	0.3644	0.4583	0.091*
H22C	1.2582	0.3403	0.5226	0.091*
C24	0.7791 (5)	0.0521 (3)	0.5319 (3)	0.0512 (12)
H24A	0.7034	0.0821	0.5502	0.077*
H24B	0.8484	0.0315	0.5749	0.077*
H24C	0.7384	0.0049	0.5008	0.077*
C15	1.0252 (6)	0.5251 (3)	0.1916 (3)	0.0557 (13)
H15A	0.9521	0.5678	0.1909	0.084*
H15B	1.0466	0.519	0.1411	0.084*
H15C	1.1113	0.5415	0.2268	0.084*
C9	0.8190 (5)	0.3869 (3)	0.4553 (2)	0.0392 (9)
C6	0.9989 (6)	0.0061 (3)	0.2594 (4)	0.0711 (17)
H6A	0.9909	0.0405	0.3031	0.107*
H6B	1.0913	−0.0219	0.2682	0.107*
H6C	0.9231	−0.0358	0.2517	0.107*
C23	1.4496 (5)	0.2195 (4)	0.5133 (3)	0.0674 (15)
H23A	1.4444	0.2298	0.566	0.101*
H23B	1.5234	0.2547	0.4989	0.101*
H23C	1.4726	0.1608	0.5068	0.101*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0346 (3)	0.0435 (3)	0.0344 (3)	−0.0002 (3)	0.0096 (2)	0.0023 (3)
O7	0.0386 (17)	0.0480 (18)	0.0414 (16)	−0.0057 (14)	0.0094 (13)	0.0079 (14)
O9	0.0346 (16)	0.056 (2)	0.0481 (17)	−0.0070 (15)	0.0023 (13)	0.0123 (15)
O3	0.0320 (15)	0.0563 (19)	0.0435 (17)	0.0059 (14)	0.0064 (13)	−0.0144 (14)
O5	0.0460 (18)	0.0499 (19)	0.0384 (15)	−0.0042 (15)	0.0155 (13)	−0.0053 (14)
O4	0.0438 (17)	0.0340 (16)	0.0419 (16)	0.0018 (13)	0.0149 (13)	0.0008 (12)
O8	0.0362 (16)	0.0508 (18)	0.0375 (14)	−0.0020 (14)	0.0060 (12)	0.0080 (14)
O6	0.055 (2)	0.0369 (16)	0.0400 (15)	−0.0039 (14)	0.0151 (14)	−0.0027 (13)
O2	0.0324 (14)	0.0447 (17)	0.0375 (14)	0.0020 (13)	0.0077 (11)	−0.0018 (13)
O1	0.0363 (16)	0.0447 (17)	0.0372 (15)	0.0066 (13)	0.0042 (12)	−0.0017 (13)
C12	0.040 (2)	0.038 (2)	0.043 (2)	−0.0009 (19)	0.0115 (19)	0.0026 (18)
C20	0.032 (2)	0.049 (3)	0.0380 (19)	−0.0028 (19)	0.0054 (16)	0.0045 (19)
C14	0.043 (3)	0.062 (3)	0.040 (2)	−0.004 (2)	0.008 (2)	−0.001 (2)
C1	0.0305 (19)	0.037 (2)	0.041 (2)	−0.0022 (18)	0.0085 (16)	0.0044 (19)
C2	0.035 (2)	0.052 (3)	0.038 (2)	0.005 (2)	0.0082 (18)	0.004 (2)
C7	0.038 (2)	0.050 (3)	0.056 (3)	−0.001 (2)	0.009 (2)	−0.004 (2)
C4	0.031 (2)	0.041 (2)	0.052 (2)	0.0033 (18)	0.0093 (19)	−0.002 (2)
C8	0.034 (2)	0.048 (3)	0.047 (2)	0.004 (2)	0.0072 (17)	0.002 (2)
C18	0.045 (3)	0.050 (3)	0.039 (2)	−0.003 (2)	0.0063 (19)	0.008 (2)
C3	0.031 (2)	0.039 (2)	0.044 (2)	−0.0004 (18)	0.0096 (18)	0.0006 (18)
C17	0.036 (2)	0.040 (2)	0.042 (2)	0.0016 (19)	0.0132 (18)	0.0047 (19)
C10	0.049 (3)	0.037 (2)	0.044 (2)	−0.002 (2)	0.011 (2)	−0.0020 (19)
C19	0.037 (2)	0.041 (2)	0.033 (2)	0.0008 (19)	0.0054 (17)	−0.0008 (18)
C13	0.046 (3)	0.052 (3)	0.059 (3)	0.008 (2)	0.019 (2)	0.005 (2)
C21	0.047 (3)	0.094 (4)	0.058 (3)	−0.005 (3)	0.021 (2)	−0.021 (3)
C11	0.032 (2)	0.042 (2)	0.045 (2)	0.0051 (18)	0.0093 (18)	0.0077 (19)
C16	0.059 (3)	0.056 (3)	0.044 (3)	0.001 (2)	0.015 (2)	−0.004 (2)
C5	0.043 (3)	0.073 (4)	0.077 (4)	−0.001 (3)	0.017 (3)	−0.033 (3)
C22	0.063 (3)	0.050 (3)	0.067 (3)	−0.011 (3)	0.010 (3)	−0.003 (3)
C24	0.050 (3)	0.052 (3)	0.054 (3)	−0.004 (2)	0.016 (2)	0.015 (2)
C15	0.066 (3)	0.045 (3)	0.062 (3)	−0.007 (2)	0.025 (3)	0.005 (2)
C9	0.040 (2)	0.043 (2)	0.037 (2)	0.008 (2)	0.0094 (18)	−0.0045 (19)
C6	0.068 (4)	0.054 (3)	0.100 (4)	0.018 (3)	0.039 (3)	0.030 (3)
C23	0.037 (3)	0.091 (4)	0.069 (3)	−0.008 (3)	−0.001 (2)	0.021 (3)

Geometric parameters (Å, º)

Fe1—O5	1.945 (3)	C12—C14	1.503 (6)
Fe1—O7	1.946 (3)	C12—C15	1.506 (6)
Fe1—O2	1.952 (3)	C12—C13	1.518 (6)
Fe1—O4	2.030 (3)	C20—C22	1.491 (7)
Fe1—O1	2.039 (3)	C20—C21	1.496 (6)
Fe1—O8	2.048 (3)	C20—C23	1.524 (6)
O7—C17	1.292 (5)	C1—C2	1.368 (5)
O9—C19	1.338 (5)	C1—C8	1.496 (6)
O9—C20	1.493 (5)	C2—C3	1.412 (6)
O3—C3	1.341 (5)	C7—C4	1.508 (6)
O3—C4	1.483 (5)	C4—C6	1.496 (7)
O5—C9	1.278 (5)	C4—C5	1.518 (6)
O4—C11	1.265 (5)	C18—C17	1.371 (6)
O8—C19	1.249 (5)	C18—C19	1.421 (6)
O6—C11	1.334 (5)	C17—C24	1.500 (6)
O6—C12	1.481 (5)	C10—C9	1.382 (6)
O2—C1	1.305 (4)	C10—C11	1.413 (6)
O1—C3	1.263 (5)	C16—C9	1.502 (6)
O5—Fe1—O7	90.8 (1)	O9—C20—C21	110.7 (4)
O5—Fe1—O2	97.4 (1)	C22—C20—C23	111.1 (4)
O7—Fe1—O2	98.2 (1)	O9—C20—C23	101.9 (3)
O5—Fe1—O4	87.7 (1)	C21—C20—C23	110.2 (4)
O7—Fe1—O4	172.1 (1)	O2—C1—C2	124.8 (4)
O2—Fe1—O4	89.7 (1)	O2—C1—C8	114.9 (3)
O5—Fe1—O1	173.4 (1)	C2—C1—C8	120.3 (4)
O7—Fe1—O1	93.6 (1)	C1—C2—C3	123.1 (4)
O2—Fe1—O1	86.9 (1)	O3—C4—C6	111.5 (4)
O4—Fe1—O1	87.3 (1)	O3—C4—C7	109.0 (3)
O5—Fe1—O8	91.8 (1)	C6—C4—C7	113.2 (4)
O7—Fe1—O8	88.0 (1)	O3—C4—C5	102.1 (4)
O2—Fe1—O8	168.9 (1)	C6—C4—C5	110.1 (4)
O4—Fe1—O8	84.3 (1)	C7—C4—C5	110.4 (4)
O1—Fe1—O8	83.4 (1)	C17—C18—C19	123.6 (4)
C17—O7—Fe1	128.7 (3)	O1—C3—O3	119.8 (4)
C19—O9—C20	122.4 (3)	O1—C3—C2	125.2 (4)
C3—O3—C4	121.7 (3)	O3—C3—C2	114.9 (4)
C9—O5—Fe1	130.3 (3)	O7—C17—C18	125.0 (4)
C11—O4—Fe1	127.1 (3)	O7—C17—C24	115.0 (4)
C19—O8—Fe1	126.6 (3)	C18—C17—C24	120.0 (4)
C11—O6—C12	121.5 (3)	C9—C10—C11	123.8 (4)
C1—O2—Fe1	129.0 (2)	O8—C19—O9	120.6 (4)
C3—O1—Fe1	127.9 (3)	O8—C19—C18	125.5 (4)
O6—C12—C14	110.0 (3)	O9—C19—C18	114.0 (4)
O6—C12—C15	102.6 (3)	O4—C11—O6	120.5 (4)
C14—C12—C15	109.7 (4)	O4—C11—C10	125.2 (4)
O6—C12—C13	110.2 (3)	O6—C11—C10	114.3 (4)
C14—C12—C13	113.0 (4)	O5—C9—C10	123.9 (4)
C15—C12—C13	110.8 (4)	O5—C9—C16	115.6 (4)
C22—C20—O9	109.9 (4)	C10—C9—C16	120.5 (4)
C22—C20—C21	112.5 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C14—H14A···O4	0.98	2.34	2.928 (5)	118 (1)
C7—H7C···O1	0.98	2.47	2.991 (6)	113 (1)
C13—H13C···O4	0.98	2.42	2.932 (6)	112 (1)
C21—H21C···O8	0.98	2.38	2.930 (6)	115 (1)
C22—H22A···O8	0.98	2.44	2.988 (6)	115 (1)
C6—H6A···O1	0.98	2.29	2.881 (7)	118 (1)