New approach to the chemistry of polysulfides using diphosphanylmethanide complexes of manganese(I)

The study of the nucleophilic degradation of S-8 by the methanide complex [ Mn(CO)(4){PPh2)(2)CH}] (2) has led to the preparation of a unique class of polysulfide derivatives of formula [(CO)(4)Mn{(PPh2)(2)C-S-n-C(PPh2)(2)}-Mn (CO)(4)]. The structures of 3 (n = 6), 4 (n = 2), and 7 (n = 1) have been d etermined by X-ray crystallography, whereas those polysulfides with the sul fur chains S-7, S-5, S-4, and S-3 have been detected by spectroscopic metho ds. The polysulfides with n > 2 lose sulfur spontaneously, a process that c an be accelerated by treatment with PPh3 or Na/Hg. Complexes 3, 4, and 7 we re protonated at the two methanide carbon atoms to give the cationic dinucl ear derivatives [(CO)(4)Mn[(PPh2)(2)C(H)-S-n-C(H)-(PPh2)(2)}Mn(CO)(4)](2+) (8, n = 6; 9, n = 2; 10, n = 1). The H-1 NMR spectrum of 9 suggests the exi stence of intramolecular C-H - - - S interactions, in agreement with the X- ray structural determination of this complex. By treatment of 4 and 7 with one equivalent of HBF, it is possible to selectively protonate just one met hanide carbon atom, which allows the isolation of the mixed cationic deriva tives [(CO)(4)Mn{(PPh2)(2)C(H)-S-n-C(PPh2)(2)}Mn(CO)(4)](+) (11, n = 2; 6, n = 1). Additionally, heterometallic complexes containing a bridging disulf ide unit, of general formula [(CO)(4)Mn{(PPh2)(2)C(AuPPh3)S-SC-(AuPPh3)(PPh 2)(2)}Mn(CO4)](2+) (12) and [(CO)(4)Mn{(PPh2)(2)C(H)S-SC(AuPPh3)-(PPh2)}Mn( CO)(4)](+) (13), were prepared by reaction of 4 and 11, respectively, with [AuCl(PPh3)] in the presence of TIPF6.