Thiolate Coordination vs C-S Bond Cleavage of Thiolates in Dinickel(II) Complexes.

A detailed study for the synthesis of dinickel(II)-thiolate and dinickel(II)-hydrosulfide complexes and the complete characterization of the relevant intermediates involved in the C-S bond cleavage of thiolates are presented. Hydrated Ni(II) salts mediate the hydrolytic C-S bond cleavage of thiolates (NaSR/RSH; R = Me, Et, Bu, Bu), albeit inefficiently, to yield a mixture of a dinickel(II)-hydrosulfide complex, [Ni(BPMP)(μ-SH)(DMF)] (), and the corresponding dinickel(II)-thiolate complexes, such as [Ni(BPMP)(μ-SEt)(ClO)] () (HBPMP is 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol). A systematic study for the reactivity of thiolates with Ni(II) was therefore pursued which finally yielded as a pure product which has been characterized in comparison with the dinickel(II)-dichloride complex, [Ni(BPMP)(Cl)(MeOH)] (). While the reaction of thiolates with anhydrous Ni(OTf) in dry conditions could only yield [Ni(BPMP)(OTf)] () instead of the expected dinickel(II)-thiolate compound, the C-S bond cleavage could be suppressed by the use of a chelating thiol, such as PhCOSH, to yield [Ni(BPMP)(SCOPh)] (). Finally, with the suitable choice of a monodentate thiol, a dinickel(II)-monothiolate complex, [Ni(BPMP)(SPh)(DMF)(MeOH)(HO)] (), was isolated as a pure product within 1 h of reaction, which after a longer time of reaction yielded and PhOH. Complex may thus be regarded as the intermediate that precedes the C-S bond cleavage and is generated by the reaction of a thiolate with an initially formed dinickel(II)-solvento complex, Ni(BPMP)(MeOH)(HO). Selected dinickel(II) complexes were explored further for the scope of substitution reactions, and the results include the isolation of a dinickel(II)-bis(thiolate) complex, [Ni(BPMP)(μ-SPh)] ().