Synthesis and Reactivity of Ortho-Mercuriated and Ortho-Palladated Arylacetals and Cyclic and Acyclic Aryldithioacetals. New Examples of the Rearrangement of Acyclic Dithioacetal Aryl- to Dithioether Alkyl-Palladium Complexes

The arylmercurial [Hg{C6H3(CHO)2-2,5}Cl] (1) reacts with CH(OMe)3 or HS(CH2)2SH to give [Hg{C6H3{CH(OMe)2}2-2,5}Cl] (2) or [Hg(Ara)Cl] [Ara = C6H3{CH(SCH2CH2S)}2-2,5 (3a)], respectively. The mercurial 2 or 3a reacts with (NMe4)2[Pd2Cl6] and 2,2‘-bipyridine (bpy) or with trans-[PdCl2(PPh3)2] to give the aryl-palladium complex [Pd{C6H3{CH(OMe)2}2-2,5}Cl(bpy)] (4) or [Pd(κ2-C,S-Ara)Cl(PPh3)] (5a*), respectively. The reaction of 1 with NaI3 renders IC6H3(CHO)2-2,5 (6), which reacts with HS(CH2)2SH to give IAra (7a). Similarly, IC6H(OMe)3-2,3,4-(CHO)-6 (8) reacts with HS(CH2)2SH or ToSH (To = C6H4Me-4) to give the corresponding dithioacetals IArb [Arb = C6H(OMe)3-2,3,4-{CH(SCH2CH2S)}-6 (7b)] or IC6H(OMe)3-2,3,4-CH(STo)2-6 (9). The iodoarene 7a or 7b adds oxidatively to “Pd(dba)2” (dba = dibenzylideneacetone) to give [Pd(κ2-C,S-Ar)(μ-I)]2 [Ar = Ara (10a), Arb (10b)], which, in turn, reacts (i) with 1 equiv of PPh3 to give [Pd(κ2-C,S-Ar)I(PPh3)] [Ar = Ara (5a), Arb (5b)], (ii) with Tl(TfO) (TfO = CF3SO3) and PPh3 (1:2:4 molar ratio) to give [Pd(κ2-C,S-Arb)(PPh3)2]TfO (11b), or (iii) with 1 equiv of Tl(TfO) and bpy (1:2:2 molar ratio) to give [Pd(κ2-C,S-Arb)(bpy)]TfO (11b*). Complexes 10 react with 1 equiv of isonitriles to give, after a short period of reaction, the complexes [Pd(κ2-C,S-Ar)I(CNR)] [Ar = Ara, R = Xy = 2,6-dimethylphenyl (12a), tBu (12a‘); Ar = Arb, R = tBu (12b‘)]. The iminoacyl complexes [Pd(κ2-C,S-Im)(μ-I)]2 [Im = Ima (13a), Imb (13b)] can be obtained by stirring a solution of 12a for 5 days to give 13a or by reacting 10b with XyNC in 1:1 molar ratio during 22 h to give 13b. Complexes 10 react with 2 equiv of isonitriles to give the iminoacyl complexes [Pd(κ2-C,S-Im)I(CNR)] [Im = C(NR)C6H3{CH(SCH2CH2S)}2-2,5, R = Xy, Im = Ima (14a), R = tBu, Im = Ima (14a‘); Im = C(NR)C6H(OMe)3-2,3,4-(SCH2CH2S)-6, R = Xy, Im = Imb (14b), R = tBu, Im = Imb (14b‘)]. Complexes 14a,b react with 10a,b in 2:1 molar ratio to give 13a,b. Complexes 10a,b react with XyNC and Tl(TfO) (1:4:1) to give the dimeric cations [Pd{(κ2-C,S-Im)(CNXy)}2(μ-I)]TfO [R = Xy, Im = Ima (15a), Imb (15b)]. The compound [Pd{κ2-C,S-Arc}(μ-I)]2 (16) reacts (i) with PPh3 and Tl(TfO) in 1:4:2 molar ratio to give [PdII(κ2-C,S-Arc)(PPh3)2]TfO ↔ [Pd023-C,S,S-S(To)CHC6H(STo)-2-(OMe)3-3,4,5}(PPh3)2]TfO (17), (ii) with isonitriles in 1:2 or 1:4 molar ratio yielding complexes [Pd(κ2-C,S-Arc)I(CNR)] [R = Xy (18), R = tBu (18‘)] or trans-[Pd(κ1-C-Arc)I(CNR)2] [R = Xy (19), R = tBu (19‘)], respectively, and (iii) with PPh3 in 1:2 molar ratio yielding [Pd(κ2-C,S-Arc)I(PPh3)] (20). The iodoarene 9 reacts with Pd(dba)2 (i) and PPh3 (1:1:1 molar ratio) to give [Pd{κ2-C,S-Arc)I(PPh3)] [Arc = CH(STo)C6H(STo)-2- (OMe)3-3,4,5 (20)] and (ii) PPh3 and Tl(TfO) (1:1:2:1 molar ratio) to give 17. The crystal and molecular structures of 4, 5a*, 14a, and 14b have been determined by X-ray diffraction studies.