Crystal structure of (4-fluorobenzyl-κC)(bis(2-hydroxyethyl) carbamodithioato-κ2S,S′)(2,2′-imino-diethanolato-κ3N,O,O′)tin(IV), C16H25FN2O4S2Sn

Abstract C16H25FN2O4S2Sn, monoclinic, P21/n (no. 14), a = 11.2227(1) Å, b = 12.6793(1) Å, c = 13.8731(1) Å, β = 98.282(1)°, V = 1953.50(3) Å3, Z = 4, Rgt(F) = 0.0198, wRref(F2) = 0.0507, T = 100(2) K.

CrysAlis PRO [1], SHELX [2,3], WinGX/ORTEP [4]   Di(4-fluorobenzyl)tin dichloride was synthesized by the direct reaction of 4-fluorobenzyl chloride (Merck) and metallic tin powder (Merck) in toluene according to a literature procedure [5]. The dithiocarbamate ligand was prepared in situ (methanol; 15 mL) from the reaction of CS 2 (Merck, 0.25 mmol) with diethanolamine (Merck, 0.25 mmol) and NaOH (0.02 mL; 50% w/v); CS 2 was added dropwise into the methanol solution. The resulting solution was kept at 273 K for 1 h. Next, di(4-fluorobenzyl)tin dichloride (Merck, 0.25 mmol, 0.10 g) in methanol (10 mL) was added into the solution and the resulting mixture was stirred for 3 h. The filtrate was evaporated until an off-white precipitate was obtained. The precipitate was washed with n-hexane and recrystallised from a methanol-acetone solution. Crystals of the title compound were obtained from the slow evaporation of the solvent; the 2,2′-imino-diethanolate di-anion is derived from diethanolamine. Yield: 0.010 g (7.

Experimental details
The C-bound H atoms were geometrically placed (C-H = 0.95-0.99 Å) and refined as riding with U iso (H) = 1.2Ueq(C). The O-and N-bound H-atoms were located in a difference Fourier map but, were refined with distance restraints of O-H = 0.84 ± 0.01 Å and N-H = 0.88 ± 0.01 Å, respectively, and with U iso (H) set to 1.5Ueq(O) and 1.2Ueq(N), respectively.

Comment
The 1,1-dithiolate, e.g. dithiocarbamate ( − S 2 CNR 2 ), compounds of the zinc-triad elements [5], main group elements [6,7], including tin [8], are well-known to form secondary M· · · S bonding interactions in their crystal structures [9,10]. However, when concurrently bound to potentially bidentate, bridging bi-pyridyl ligands, with the aim of increasing the dimensionality of the supramolecular association, the secondary bonding is generally lost, as amply demonstrated in the structural chemistry of the zinc-triad 1,1-dithiolates [11]. One way of overcoming this limitation is to introduce hydrogen bonding functionality in the R groups, e.g. hydroxyethyl groups, as the resultant hydrogen bonding can lead to one-, two-and, sometimes, three-dimensional aggregation in the solid-state [5][6][7][8]11]. In the title mixed ligand, organotin compound, (4-FC 6 H4CH 2 )Sn[OCH 2 CH 2 N(H)CH 2 CH 2 O][S 2 CN(CH 2 CH 2 OH) 2 ], (I), the dithiocarbamate ligand bears two hydroxyethyl groups, each capable of hydrogen bonding. Herein, the crystal and molecular structures of (I) are described along with an analysis of the calculated Hirshfeld surfaces.
The molecular structure of (I) is shown in the figure (70% displacement ellipsoids). The tin atom is coordinated by the methylene-carbon atom of the 4-fluorobenzyl substituent, two sulphur atoms of the dithiocarbamate ligand along with the imino-nitrogen and two ethoxide-oxygen atoms of the di-anionic, tridentate 2,2′-imino-diethanolate ligand. The dithiocarbamate ligand chelates in a symmetric mode as seen in the equivalence of the Sn-S1 and S2-Sn-O3 [157.41(4)°] trans angles deviate from the ideal 180°. To a first approximation, the O 2 S 2 atoms define a square-plane [r.m.s. deviation = 0.0348 Å] and the Sn atom lies 0.2859 (6) above this plane in the direction of the 4fluorobenzyl-C10 atom. The tridentate mode of coordination for the 2,2′-imino-diethanolate ligand gives rise to two five-membered Sn,O,N,C 2 rings, which adopt distinct conformations. Thus, the O3-chelate is twisted about the C7-N2 bond. By contrast, the O4-ring has an envelope conformation with the flap atom, C9, lying 0.555(3) Å out of the leastsquares plane through the remaining four atoms [r.m.s. deviation = 0.044 Å].
Tin(II), tin(IV) and organotin(IV) dithiocarbamate compounds are well known in the literature with coordination modes ranging from symmetric as in (I) to effectively monodentate in triorganotin derivatives but often adopt asymmetric modes of coordination [8]. By contrast, there is only one literature precedent for a tin compound with the 2,2′-imino-diethanolate ligand, namely in the structure of Sn(OCH 2 CH 2 N(H)CH 2 CH 2 O)(CH 2 Si(Me) 2 OSi(Me) 2 CH 2 ) [12].
The other major contributions come from F· · · H/H· · · F [9.2%] and S· · · H/H· · · S [7.1%], with some F· · · H contacts within distances less than the sum of their van der Waals radii.