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

Abstract

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(κ 2 -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{(κ 2-C,S-Im)(CNXy)}2(μ-I)]TfO [R = Xy, Im = Ima (15a), Imb (15b)]. The compound [Pd{κ 2-C,S-Arc}(μ-I)]2 (16) reacts (i) with PPh3 and Tl(TfO) in 1:4:2 molar ratio to give [PdII(κ 2-C,S-Arc)(PPh3)2]TfO ↔ [Pd0{η 2 -κ3-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(κ 2-C,S-Arc)I(CNR)] [R = Xy (18), R = tBu (18‘)] or trans-[Pd(κ 1 -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{κ 2-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.

Synthesis and Reactivity of Ortho-Palladated Phenylacetamides. Intramolecular C−N vs C−O Reductive Coupling after CO or XyNC Insertion into the Pd−C Bond. Synthesis of Isoquinoline- and Isocoumarin-Based Heterocycles

“…We report also a systematic study of the reactions of these aryl complexes with CO and XyNC (Xy = 2,6-dimethylphenyl). This type of reactions have been widely studied, as they are involved in the synthesis of acyl [10][11][12][13][14][15] and iminoacyl 11,[13][14][15][16][17][18][19][20] palladium complexes and also in many stoichiometric and catalytic syntheses of organic compounds. [13][14][15][20][21][22] We report in this work that, depending on the substituents on the amidic nitrogen, these insertion reactions lead to isoquinoline-or isocoumarin-based heterocycles resulting from intramolecular C-N or C-O couplings.…”

New developments in the studies of the reactivity of cyclometallated palladium(II) compounds with homo- ([P,P],[As,As]) and heterobidentate ([P,N],[P,O]) ligands

“…Mass spectra were obtained in a QUATRO mass spectrometer with Cs ion-gun and 3-NBA matrix. NMR spectra were obtained as CDCl 3 solutions and referenced to SiMe 4 ( 1 H, 13 (1) and [Pd{5-(COH)C 6 H 3 -C(H)@NCy-C2,N}(l-Cl)] 2 (2) has been reported previously from this laboratory [17,18]. The phosphine (oTol) 2 P(CH 2 ) 2 P(o-Tol) 2 was prepared as described previously in the literature [61].…”

“…In particular, cyclometallation of Schiff-base ligands with a wide range of transition metals has been extensively investigated. Tetradentate [C,N,C,N] Schiff bases generally undergo double metallation to give compounds with two metal atoms per organic ligand [6][7][8][9][10][11][12][13][14][15][16], however, as we have reported previously, in the case of the potentialy tetradentate ligands derived from isophthalaldehyde, 1,3-(CyN@CH) 2 C 6 H 4 , and terephthalaldehyde, 1,4-(CyN@CH) 2 conditions [17][18][19]. Thus, treatment with palladium(II) acetate in acetic acid gave the monocyclometallated complexes 1 and 2 after cleavage of one C@N double bond, and we have studied the reactivity of these cyclometallated complexes towards different mono and bidentate ligands [20][21][22][23][24].…”

Hemilabile orthometallated acetals: Synthesis, spectroscopic characterization and crystal and molecular structures of [RuCl{η2-C,O-C6H4-2-CH(O2C2H4)}(CO)(PPh3)2] and [HgBr{η2-C,O-C6H4-2-CH(O2C2H4)}]

“…A better understanding of the nature of these fluxional processes is useful in understanding the dynamics of this type of ligand and the development of new hemilabile ligand sets for use in homogeneous catalysis [6]. During the course of this work Vicente et al reported the preparation of some analogous orthomercuriated arylacetals and their utility as transfer reagents in the preparation of some orthopalladated arylacetal complexes [7]. The number of other examples of cyclometallated (g 2 -C,O coordinated) aryl acetals is limited [8].…”

“…For related thioether-containing complexes pyramidal geometry at sulfur is, as expected, normal. For example Vicente et al have recently reported the solid state structure of the cyclopalladated thioacetal-containing complex [PdCl{g 2 -C,S-C 6 H 3 -2,5-(CHS 2 C 2 H 4 )}(PPh 3 )] and the thioacetal ligand is pyramidal at sulfur [7].…”