Synthesis and multinuclear magnetic resonance study of some tin(IV) complexes of pyridine-2-thiolate and related ligands, and the X-ray structural analysis of Sn(C₅H₄NS)₄•C₅H₅NS

Abstract

Tin metal reacts with 2,2′-dithiobis (pyridine) in refluxing toluene to give the pyridine-2-thiolate complex Sn(C 5 H 4 NS) 4 , 1a. Multinuclear ( 77 Se, 119 Sn) magnetic resonance shows that ligand redistribution occurs in 1a:Sn(EPh) 4 (E = S or Se) mixtures to give Sn(EPh) 4−x (C 5 H 4 NS) x . From the pattern of the 119 Sn chemical shifts of these series, compared with that of Sn(EPh) 4−x (SR) x (R = simple alkyl or aryl group), the complexes are shown to be five-coordinate Sn(EPh) 3 (C 5 H 4 NS-N,S) when x = 1 and six-coordinate Sn(EPh) 4−x (C 4 H 4 NS-S) x−2 (C 5 H 4 NS-N,S) 2 when x = 2–4. Reaction of Sn(SPh) 2 and (C 5 H 4 NS) 2 yields pure Sn(SPh) 2 (C 5 H 4 NS) 2 . The 13 C NMR spectrum of Sn(C 5 H 4 NS-S) 2 (C 5 H 4 NS-N,S) 2 is an exchange average down to 178 K, probably as a result of fluxionality. The series Sn(EPh) 4−x ,(L′) x (E = Se, L′ =5-nitropyridine- or quinoline-2-thiolate, x = 0–4; E = S or Se, L′ = pyridine-2-thiolate-N-oxide, x = 0–2) can be prepared insitu by redox between Sn(EPh) 4 and the disulfide (L′) 2 . Treatment of 1a with X 2 (X = Br or E- gives SnX 4−x (C 5 H 4 NS-N,S) x (x = 2 or 3), which have been characterized by NMR, and provides a new synthesis of the known dihalo complexes.In a recrystallization of 1a from CH 2 Cl 2 :hexane Sn(C 5 H 4 NS) 4 •C 5 H 5 NS, 2, was obtained, probably as a result of hydrolysis. The structure of 2 has been solved by single crystal X-ray diffraction techniques. The compound crystallizes in the orthorhombic space group Pbca (No. 61) with a unit cell of dimensions a = 17.132(2) Å, b = 15.337(2) Å, c = 21.268(3) Å, and Z = 8. Full-matrix least-squares on F led to agreement factors R = 0.0439 and R w = 0.0426 for 3145 independent reflections with F o > 2.5σ (F o ) and 206 variables. The molecule Sn(C 5 H 4 NS-S) 2 (C 5 H 4 NS-N,S) 2 has highly distorted octahedral coordination about the tin atom, with the monodentate ligands in cis positions and the bidentate ligands attached with mutually cis nitrogen atoms. The Sn—S distances are 2.463(2)–2.542(2) Å and the Sn—N distances are 2.332(2) and 2.324(2) Å. The N—Sn—S angles in the chelate rings are 64.2(2) and 65.1(1)°. The molecule of pyridine-2-thione in the lattice is hydrogen-bonded to the N atom of one of the monodentate ligands in the tin complex, with a [Formula: see text] hydrogen bond distance of 1.92(7) Å. Keywords: pyridine-2-thiolate, selenium-77 NMR, tin-119 NMR, tin(IV) complexes, X-ray analysis.