Synthesis and Reactivity Studies of Dicationic Dihydrogen Complexes Bearing Sulfur‐Donor Ligands: A Combined Experimental and Computational Study

A series of dihydrogen complexes trans ‐[Ru(η 2 ‐H 2 ){SC(SR)H}(dppe) 2 ][X][BF 4 ] (R = CH 3 , X = OTf; R = C 6 H 5 CH 2 , X = BPh 4 ; R = H 2 C=CHCH 2 , X = BPh 4 ; dppe = Ph 2 PCH 2 CH 2 PPh 2 ) bearing sulfur‐donor ligands has been synthesized by protonation of the (alkyl dithioformate)hydrido complexes trans ‐[Ru(H){SC(SR)H}(dppe) 2 ][X] by using HBF 4 · Et 2 O. Competitive substitution reactions between H 2 and SC(SR)H in trans ‐[Ru(η 2 ‐H 2 ){SC(SR)H}(dppe) 2 ][X][BF 4 ] have been studied by treatment with CH 3 CN, CO, and P(OCH 3 ) 3 . These resulted in the expulsion of SC(SR)H from the metal center, thus indicating that the alkyl dithioformate ligand is more labile than H 2 . Bonding of alkyl dithioformate ligands (sulfur‐donor ligands) trans to H 2 have been studied by comparing the H–H distances and chemical‐shift values ( 1 H NMR spectroscopy) of the various dihydrogen complexes bearing different trans ligands. This study qualitatively suggests that the alkyl dithioformate ligands in these trans ‐dihydrogen complexes show a poor π effect, and it is further supported by density functional theory calculations. The first example of a dihydrogen complex bearing dithioformic acid, trans ‐[Ru(η 2 ‐H 2 ){SC(SH)H}(dppe) 2 ][BF 4 ] 2 , was obtained by protonation of trans ‐[Ru(H){SC(S)H}(dppe) 2 ] by using HBF 4 · Et 2 O.