Crystal structure of a trifluoromethyl benzoato quadruple-bonded dimolybdenum complex

The study of quadruple bonds between transition metals, in particular those of dimolybdenum, has revealed much about the two-electron bond. The solid-state structure of the quadruple-bonded dimolybdenum(II) complex tetrakis(μ-4-trifluoromethylbenzoato-κ2 O:O′)dimolybdenum(II) 0.762-pentane 0.238-tetrahydrofuran solvate, [Mo2(p-O2CC6H4CF3)4·2THF]·0.762C5H12·0.238C4H8O or [Mo2(C8H4F3O2)4(C4H8O)2]·0.762C5H12·0.238C4H8O is reported. The complex crystallizes within a triclinic cell and low symmetry (P\overline{1}) results from the intercalated pentane/THF solvent molecules. The paddlewheel structure at 100 K has inversion symmetry and comprises four bridging carboxylate ligands encases the Mo2(II,II) core that is characterized by two axially coordinated THF molecules and an Mo—Mo distance of 2.1098 (7) Å.

Structural diversity among some dialkyltin(IV) benzoate and related derivatives

The molecular structures of five diorganotin(IV) carboxylates, (I)–(V), can be categorized into two main well-known structural types for such Sn complexes. One is the mononuclear dialkytin(IV) carboxylates with an [R2Sn(LH)2]-type skew-trapezoidal bipyramid, where the alkyl ligands are in pseudo-axial positions and the O atoms from two asymmetrically coordinated bidentate carboxylate ligands are in the equatorial plane. This structure type is adopted by dibutylbis{(E)-2-hydroxy-5-[(3-methylphenyl)diazenyl]benzoato}tin(IV) cyclohexane hemisolvate, [Sn(C4H9)2(C14H11N2O3)2]·0.5C6H12, (I), dibenzylbis{(E)-5-[(4-bromophenyl)diazenyl]-2-hydroxybenzoato}tin(IV), [Sn(C7H7)2(C13H8BrN2O3)2], (II), and aquadibenzylbis(4-{(E)-[(Z)-4-hydroxypent-3-en-2-ylidene]amino}benzoato)tin(IV) benzene disolvate, [Sn(C7H7)2(C12H12NO3)2(H2O)]·2C6H6, (III), although the latter has an additional water ligand to give a distorted pentagonal bipyramidal coordination geometry in which the carboxylate groups are more symmetrically coordinated to the Sn atom than in (I) and (II). The other structure motif is that of the tetranuclear bis(dicarboxylatotetraorganodistannoxanes), {[R2Sn(LH)]2O}2, which contain an Sn4O2 core decorated with four bridging carboxylate ligands, plus two alkyl ligands at each SnIV centre. The complexes octabutyltetrakis{μ-(E)-4-[(4-hydroxy-3,5-dimethylphenyl)diazenyl]benzoato}di-μ3-oxido-tetratin(IV) ethanol disolvate, [Sn4(C4H9)8(C15H13N2O3)4O2]·2C2H6O, (IV), and octabutyltetrakis{(E)-3-[(2-hydroxybenzylidene)amino]propanoato}di-μ3-oxido-tetratin(IV), [Sn4(C4H9)8(C10H10NO3)4O2], (V), display this motif. The structures obtained correlate with the 1:1 and 1:2 stoichiometric ratios of the dialkyltin(IV) and carboxylic acid starting materials in the syntheses. The supramolecular structures arising from consideration of secondary Sn...O interactions and/or classic hydrogen bonds include discrete molecules for (V), centrosymmetric dimers for (I), extended chains for (II) and (III), and sheets for (IV).