{μ-2-[4-(1,3-Benzothiazol-2-yl)phenyl]-2-azapropane-1,3-dithiolato-κ4 S,S′:S,S′}bis[tricarbonyliron(I)]

The title compound, [Fe2(C15H12N2S3)(CO)6], was prepared as an azadithiolatodiiron model for the active site of [FeFe]-hydrogenase. The Fe2S2 core adopts a butterfly shape, with each metal having a pseudo square-pyramidal geometry. The N-substituted azadithiolate is μ2-κ4 S,S′:S,S′-coordinated to the Fe(CO)3 moieties to form two fused six-membered rings with different conformations. The sum of the C—N—C angles around the N atom [356.85 (15)°] indicates a flattening of the trigonal–pyramidal geometry about the N atom and an increase in the degree of sp 2-hybridization.

The sum of the C-N-C angles around N1 atom is 356.85 (15)° implying a noticeable flattening of the trigonal pyramidal geometry about N1 and an increase in the degree of p-π conjugation between the substituted phenyl ring and the p-orbital of the bridging N atom. The distance of N1 from the plane defined by C7, C8 and C9 is 0.146 (2) Å and the dihedral angle between this plane and the mean plane of the adjacent phenyl ring is 2.5 (1)°. The substituted phenyl ring attached to N1 lies in an axial position relative to the metalloheterocycle and slants towards the Fe 2 (CO) 3 unit. As a result, the C1-Fe1-Fe2 angle is enlarged by ca 7° compared with the C6-Fe2-Fe1 angle.
The molecular structure of the title compound is shown in Fig.1.

Experimental
All reactions and operations related to the title compound were carried out under a dry, prepurified nitrogen atmosphere with standard Schlenk techniques. All solvents were dried and distilled prior to use according to standard methods. The starting material N,N′-bis(chloromethyl)-(4-benzothiazole)-phenylamine was prepared in 50% yield from 4-benzothiazole-phenylamine (Lawrence et al., 2001). A degassed solution of (µ-S 2 )Fe 2 (CO) 6 (1.38 g, 4.0 mmol) in 30 ml dry THF was cooled to 195 K. LiEt 3 BH (1 M solution in THF, 8.0 ml, 8.0 mmol) was dropped into the above solution by syringe over 30 min. N,N′-bis(chloromethyl)-(4-benzothiazole)-phenylamine (2.6 g, 8.0 mmol) was added to the resulting dark green solution causing an immediate change in color to dark red. The mixture was stirred for 2 h at 195 K and another 1 h at room temperature. The solvent was removed on a rotary evaporator and the crude product was purified by column chromatography (silica, 20% dichloromethane in hexane as eluent) to give a red solid (1.37 g, 57%). Recrystallization from a CH 2 Cl 2 /hexane solution afforded crystals of the title compound suitable for X-ray study.

Refinement
The H atoms attached to C were placed in geometrically calculated positions (C-H = 0.93-0.97 Å) and refined as riding, with U iso (H) = 1.2U eq (C).

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level and Hatoms omitted.

{µ-2-[4-(1,3-Benzothiazol-2-yl)phenyl]-2-azapropane-1,3-dithiolato-κ 4 S,S′:S,S′}bis[tricarbonyliron(I)]
Crystal data [Fe 2 (C 15   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.