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,
n
Bu,
t
Bu), albeit
inefficiently, to yield a mixture of a dinickel(II)–hydrosulfide
complex, [Ni2(BPMP)(μ-SH)(DMF)2]2+ (1), and the corresponding dinickel(II)–thiolate
complexes, such as [Ni2(BPMP)(μ-SEt)(ClO4)]1+ (2) (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 1 as a pure product which has been characterized
in comparison with the dinickel(II)–dichloride complex, [Ni2(BPMP)(Cl)2(MeOH)2]1+ (3). While the reaction of thiolates with anhydrous Ni(OTf)2 in dry conditions could only yield [Ni2(BPMP)(OTf)2]1+ (5) 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 [Ni2(BPMP)(SCOPh)2]1+ (6). Finally,
with the suitable choice of a monodentate thiol, a dinickel(II)–monothiolate
complex, [Ni2(BPMP)(SPh)(DMF)(MeOH)(H2O)]2+ (7), was isolated as a pure product within
1 h of reaction, which after a longer time of reaction yielded 1 and PhOH. Complex 7 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, [Ni2(BPMP)(MeOH)2(H2O)2]3+(4). 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, [Ni2(BPMP)(μ-SPh)2]1+ (8).