Trigonal Prismatic vs Octahedral Coordination Geometry:  Syntheses and Structural Characterization of Hexakis(arylthiolato) Zirconate Complexes

Abstract

Treating [Li(tmeda)]2[Zr(CH3)6] with aryl thiols, HSC6H4-4-R, in a 1:6 stoichiometry in diethyl ether affords excellent yields of [Li(tmeda)]2[Zr(SC6H4-4-R)6], where R = CH3 (1(2-)) or OCH3 (2(2-)) and tmeda denotes N,N,N',N'-tetramethylethylenediamine. These complexes are air-sensitive canary-yellow solids, soluble in hexane, diethyl ether, THF, and acetonitrile, that form yellow single crystals of [Li(tmeda)](2)1 (diethyl ether solution) or [Li(THF)3](2)2 (THF solution) from saturated solutions at -20 degrees C. Both complexes were characterized by X-ray crystallography and consist of a zirconium atom coordinated solely by the sulfur atoms of six aryl thiolate ligands in a nonoctahedral geometry. In each structure the lithium cation coordinates to the three sulfur atoms on the triangular faces of the S6 pseudotrigonal prism. These lithium-sulfur interactions appear to play a role in determining the coordination geometry about the metal center by orienting the sulfur lone pairs of electrons slightly out of the plane defined by the S3 triangular face and tilted away from the zirconium atoms. A likely consequence is the positioning of the sulfur lone pairs of electrons away from orthogonality with the zirconium-sulfur vector, and hence, they are poorly arranged to pi-interact with zirconium. Complex 1(2-) with a twist angle of ca. 9.18 degrees (trigonal prism, 0 degree; octahedron, 60 degrees) agrees with the interpretations of computational studies on d degree complexes, which suggest that a nearly trigonal prismatic geometry is favored when the interaction between metal and ligand is primarily through sigma-bonds. The intrinsically weak pi-donor thiolate ligand is probably converted to a primarily sigma-bonding system by the lithium-sulfur interaction. On the other hand complex 2(2-) with a twist angle of ca. 30.38 degrees is trigonally twisted to the midpoint of the trigonal prismatic-to-octahedral reaction coordinate. In complex 2(2-) the 4-OCH3 group is an electron donor by resonance effects that possibly may lead to the movement away from the expected trigonal prismatic geometry due to either pi-interactions or electrostatics repulsion.

Synthesis and X-ray Molecular Structure of [WVI(C6H4S2-1,2)3] Completing the Structural Characterization of the Series [W(C6H4S2-1,2)3]n (n = 0, 1, 2): Trigonal-Prismatic versus Octahedral Coordination in Tris(benzene-1,2-dithiolato) Complexes

“…The moderate yields as well as the solvent toxicity and the highly reactive by-product in these syntheses proved disadvantageous in our opinion. A rather exotic way to prepare hexakis(arylthiolato) zirconate complexes with six monodentate thiolato ligands using [Zr(CH 3 ) 6 ] 2Ϫ as a precursor was reported by Giolando et al [4] Using this approach, we have improved the synthesis for [W VI (C 6 H 4 S 2 -1,2) 3 ] (1) by reacting [W(CH 3 ) 6 ] with three equivalents of benzene-1,2-dithiol in diethyl ether with formation of unreactive methane gas (Scheme 1). The product can be isolated in pure form and in yields of about 70%.…”

“…[2] In addition, the ''non-innocent'' nature of benzenedithiolato ligands and their derivatives has more recently become a field of considerable interest. [3] Nevertheless, the trigonal-prismatic coordination geometry is not limited to tris(dithiolene) complexes, but can also be observed for some hexaarylthiolato [4] and hexaorgano complexes with six monodentate ligands. The latter complexes have received a great deal of attention since the molecular structure of the complex [Li(tmed)] 2 [Zr(CH 3 ) 6 ] containing a distorted trigonal-prismatic coordinated zirconium atom was reported.…”

Trigonal‐Prismatic vs. Octahedral Geometry for MnII Complexes with Innocent Didentate Ligands: A Subtle Difference as Shown by XRD and DFT on [Mn(acac)2(bpy)]

“…[10,11] Even some examples of six-coordinate trigonalprismatic complexes with monodentate ligands have been reported. [12,13] These complexes all contain d 0 metal ions and in these cases the preference for the trigonal-prismatic geometry has been ascribed to the absence of steric or π-bonding effects.…”

Muconato‐bridged Manganese Coordination Polymer exhibiting rare Distorted‐trigonal Prismatic Coordination Arrangement

“…[10] Furthermore, in fewer cases, this arrangement has been revealed in complexes using innocent bidentate ligands, such as bipyridine and acac, and even in complexes with monodentate ligands. [11] Herein, we describe the synthesis, crystal structure details and magnetic properties of polymer [Mn(H 2 O)(dmb)(muco)] (1) (H 2 muco = trans,trans-muconic acid; dmb = 5,5Ј-dimethyl-2,2Ј-bipyridine), which shows an unusual distorted trigonal prismatic coordination sphere, that include innocent ligands and an aqua ligand, as well as a 2D supramolecular array through hydrogen bonding. Self-assembly of small molecules, compounds or complexes, has demonstrated to be an appreciated process for synthesizing large structures with a minimum effort.…”