trans-Bis(acetonitrile-κN)bis­{1,2-bis­[bis­(3-hydroxy­prop­yl)phosphino]ethane-κ2 P,P′}iron(II) dichloride

J W Gohdes; Lev N Zakharov; David R Tyler

doi:10.1107/S1600536809021758

. 2009 Jun 17;65(Pt 7):m776. doi: 10.1107/S1600536809021758

trans-Bis(acetonitrile-κN)bis{1,2-bis[bis(3-hydroxypropyl)phosphino]ethane-κ² P,P′}iron(II) dichloride

J W Gohdes ^a, Lev N Zakharov ^b, David R Tyler ^b,^*

PMCID: PMC2969375 PMID: 21582706

Abstract

In the title compound, [Fe(CH₃CN)₂(C₁₄H₃₂O₄P₂)₂]Cl₂, the Fe^II atom lies on a crystallographic inversion center and has a distorted trans-FeN₂P₄ octahedral coordination environment arising from two P,P′-bidentate 1,2-bis[bis(3-hydroxypropyl)phosphino]ethane ligands in the equatorial plane and two acetonitrile molecules in the axial positions. One of the pendant –(CH₂)₃OH groups of the ligand is disordered over two sets of sites in a 0.597 (5):0.403 (5) ratio. In the crystal, O—H⋯Cl and O—H⋯O hydrogen bonding helps to establish the packing.

Related literature

For related compounds containing bidentate phosphine ligands, see: Gilbertson et al. (2007 ▶); Miller et al. (2002 ▶); Martins et al. (1998 ▶); Barron et al. (1987 ▶); George et al. (1997 ▶); Edwards et al. (2006 ▶). For reference structural data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

[Fe(C₂H₃N)₂(C₁₄H₃₂O₄P₂)₂]Cl₂
M _r = 861.53
Orthorhombic,
a = 18.3024 (12) Å
b = 11.5220 (8) Å
c = 19.8413 (13) Å
V = 4184.1 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.69 mm⁻¹
T = 173 K
0.22 × 0.18 × 0.17 mm

Data collection

Bruker APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2000 ▶) T _min = 0.863, T _max = 0.892
24288 measured reflections
4571 independent reflections
4122 reflections with I > 2σ(I)
R _int = 0.024

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.092
S = 1.04
4571 reflections
269 parameters
7 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.88 e Å⁻³
Δρ_min = −1.01 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT (Bruker, 2000 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809021758/hb2994sup1.cif

e-65-0m776-sup1.cif^{(25.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809021758/hb2994Isup2.hkl

e-65-0m776-Isup2.hkl^{(224KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Fe1—N1	1.9077 (14)
Fe1—P1	2.2884 (4)
Fe1—P2	2.3049 (4)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O⋯Cl1	0.928 (17)	2.126 (18)	3.0493 (16)	173 (3)
O2—H2O⋯Cl1ⁱ	0.976 (18)	2.23 (2)	3.1777 (19)	164 (3)
O3—H3O⋯O1ⁱ	0.924 (17)	1.841 (18)	2.741 (2)	164 (2)
O4—H4O⋯Cl1ⁱⁱ	0.98 (2)	1.95 (2)	2.931 (6)	177 (3)
O4A—H4OA⋯Cl1ⁱⁱ	0.98 (2)	2.84 (11)	3.490 (10)	125 (9)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

We thank the NSF (CHE-0809393) for funding.

supplementary crystallographic information

Comment

The bidentate phosphine 1,2-bis[di(3-hydroxypropyl)phosphino]ethane (DHPrPE) was developed as a water soluble ligand for use in making iron complexes capable of binding dinitrogen and hydrogen (Miller et al., 2002). It was found that the hydroxypropyl groups were non-innocent in reactions with iron(II), and a stable complex was isolated in which the chelating phosphine ligands are tridentate and coordinate through one of the hydroxypropyl groups in addition to both phosphines. This results in a coordinatively saturated complex where the alcohols ligands are cis to one another. The current work shows that addition of acetonitrile to this species results in the rearrangement to the trans geometry.

The stucture of the cation [Fe(DHPrPE)₂(CH₃CN)₂]²⁺ in the title compound, (I), is shown in Fig. 1. The four phosphine donors from the DHPrPE ligands form a square planar arrangement around the iron atom and the two coordinated acetonitrile ligands occupy the trans axial sites to form a distorted octahedral geometry around the iron. Such trans bis acetonitrile complexes of iron(II) with bidentate phosphines are not uncommon. The first reported structure was of the DMPE analog (Barron et al. 1987). An examination of similar compounds (George et al. 1997, Martins et al. 1998, Gilbertson et al. 2007 and Edwards et al. 2006) shows there are minor variations within the primary coordination sphere of all of these complexes. The Fe—N bond distances vary from 1.895 to 1.917 Å; the Fe—P bond distances vary from 2.255 to 2.3032 Å and the P—Fe—P bite angles are between 84.0° and 85.5°. The Fe—P distances in the title compound, 2.2883 (5) and 2.3044 (5) Å, are at the high end of the expected range while the bite angle of 84.2° is at the low end of the range, indicating significant steric crowding around the iron center.

Experimental

The title compound was prepared by dissolving 60 mg of iron(II)chloride tetrahydrate (0.30 mmole) and 200 mg of 1,2-bis[di(3-hydroxypropyl)phosphino]ethane (0.61 mmole) in 3.0 ml of methanol to give a dark purple solution. After addition of 2.0 ml of acetonitrile, the solution slowly turned orange indicating formation of the title complex. Addition of diethylether and filtration yielded 215 mg (90%) of the title compound as an orange, crystalline powder and gave a single resonance in the ³¹P{¹H} NMR spectrum at 61.4 p.p.m.. Yellow blocks of (I) were grown by vapor diffusion of diethylether into a 3:1 methanol/acetonitrile solution of the complex.