2,2′-Bis(4-methoxyphenyl)-2,2′-bis(trimethylsilanyloxy)-2,2′-(ferrocene-1,1′-diyl)diacetonitrile

In the title compound, [Fe(C17H20NO2Si)2], the Fe atom is situated on a crystallographic centre of inversion, leading to a perfectly staggered conformation of the Cp rings.

In the title compound, [Fe(C 17 H 20 NO 2 Si) 2 ], the Fe atom is situated on a crystallographic centre of inversion, leading to a perfectly staggered conformation of the Cp rings.
The molecular structure of the title compound, (I), shows the Fe atom on a crystallographic center of inversion and two Cp ligands with a cyanohydrin ether substituents. Because of the inversion symmetry the Cp ligands show a staggered conformation. The central tetrahedral C(6) atom is bound to C≡N, (CH 3 ) 3 SiO and (CH 3 O)C 6 H 4 groups in compound and is therefore a new stereogenic center which is formed during the reaction sequence. Due to the internal symmetry of the molecule Figure 1 shows the R,S diastereomer. There is no evidence for the formation of R,R-or S,S-diastereomers even from NMR spectra of the crude reaction product. The bond angle of C(6)-C(7)-N(1) is 178.9 (6)° showing sp hybridization for the C≡N carbon atom. The Si(1)-O(1)-C(6) bond angle measures to 131.6 (3)° which is significantly larger compared to that of a regular tetrahedron (109.5°). The influence of neighbouring Csp and Csp 2 atoms shorten the C(6)-C(1), C(6)-C(7) and C(6)-C(8) bond distances (1.511 (6) Å, 1.483 (7) Å and 1.531 (6), respectively) compared to normal C-C bond distances (app. 1.54 Å). It shows there may be a super conjugate effect in the molecule of the title compound.

S2. Experimental
Into a 100 ml 3-neck round-bottomed flask equipped with magnetic stirring bar, reflux condenser and CaCl 2 drying tube was placed 1.1 mmol (297 mg) bisacetylferrocene in 15 ml dry CH 2 Cl 2 and 1 mmol (319 mg) ZnI 2 . After stirring for 20 minutes, 4.4 mmol TMSCN (374 mg) were added and the was solution stirred for 10 h. During the reaction the progress of the reaction was monitored by TLC (benzene). After completion the solvent was evaporated under reduced pressure with the residue obtained being extracted with pentane. The solution was washed with saturated cold aqueous NaHSO 3 and dried over Na 2 SO 4 . Filtration and removal of the solvent under reduced pressure yielded the crude product which was recrystallized from ether/light petroleum (b.p. 60-90°) to obtain single crystals the title compound.

S3. Refinement
All the H atoms were positioned geometrically and refined using a riding model with C-H distances of 0.93-0.97° and U iso (H) = 1.2U eq of the corresponding parent atom. The methyls at the terminal group have higher U eq than silicon atom in supporting information the central tetrahedral.

Figure 1
The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are represented by circles of arbitrary size.

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. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )
x y z U iso */U eq