Behavior of anionic molybdenum(iv,vi) and tungsten(iv,vi) complexes containing bulky hydrophobic dithiolate ligands and intramolecular NH⋯S hydrogen bonds in nonpolar solvents

Abstract

Molybdenum(IV, VI) and tungsten(IV, VI) complexes, (Et4N)2[M(IV)O{1,2-S2-3,6-(RCONH)2C6H2}2] and (Et4N)2[M(VI)O2{1,2-S2-3,6-(RCONH)2C6H2}2] (M = Mo, W; R = (4-(t)BuC6H4)3C), with bulky hydrophobic dithiolate ligands containing NH···S hydrogen bonds were synthesized. These complexes are soluble in nonpolar solvents like toluene, which allows the detection of unsymmetrical coordination structures and elusive intermolecular interactions in solution. The (1)H NMR spectra of the complexes in toluene-d8 revealed an unsymmetrical coordination structure, and proximity of the counterions to the anion moiety was suggested at low temperatures. The oxygen-atom-transfer reaction between the molybdenum(IV) complex and Me3NO in toluene was considerably accelerated in nonpolar solvents, and this increase was attributed to the favorable access of the substrate to the active center in the hydrophobic environment.

Unexpected Reaction Promoted by NH+···O=Mo Hydrogen Bonds in Nonpolar Solvents

“…Indeed, (Et 4 N) 2 [1] was synthesised in 10 % watercontaining acetonitrile. [21] In the present case, (Et 3 NH) 2 [1] was not obtained in the presence of excess water, especially under acidic conditions. In this method, the trace amount of water and excess Et 3 N are very important.…”

“…In the previous work, LS was used as a precursor of the ligand. [21] As an improvement, thiosulfonate…”

“…In both cases, intramolecular NH···π interactions were present, as described previously for (Et 4 N) 2 [1]. [21] The chemical shifts and IR data are summarised in Table 1. The data for Ar 3 CCONHPh and 1,2-benzenedithiol (bdtH 2 ) are given as reference values, without hydrogen bonds.…”

“…2- [21] was treated with KI [24] to give the 1,2,5,6-tetrathiocin derivative L 2 , i.e., the disulfide form of L, in reasonable yield. Reduction of L 2 Figure 1 and Table S1 and Figure S1 in the Supporting Information).…”

“…[20,21] We have reported a monooxomolybdenum(IV) arenedithiolate containing very bulky hydrophobic acylamino groups, (Et 4 N) 2 [Mo IV O(1,2-S 2 -3,6-{(tBuC 6 H 4 ) 3 CCONH} 2 C 6 H 2 ) 2 ] [(Et 4 N) 2 [1]]. [21] The crystal structure of which showed an interionic CH···O=Mo interaction between the Et 4 N + cation and [1] 2-anion, which is maintained in toluene. If the counter cation is replaced by Et 3 NH + , an NH + ···O=Mo hydrogen bond should be formed, and its strength and properties in solution can be evaluated.…”