Abstract:Mixtures of ªPd(dba) 2 º (dba dibenzylideneacetone) and neutral ligands react with an excess of 2-iodoaniline to give [Pd(C 6 H 4 NH 2 -2)-

By the refluxing of an acetonitrile solution of [Pd(OAc)2]3 and primary amines 4-XC6H4CH2NH2 (F, Cl, NO2, OMe), 3,5-X2C6H3CH2NH2 (X = OMe), or PhCH2CH2NH2 (Pd:amine = 1:1) and subsequent addition of excess NaBr, the corresponding orthometalated complexes [Pd{C6H3(CH2NH2)-2,X-5}(μ-Br)]2, [Pd{C6H3(CH2NH2)-2,(OMe)2-4,6}(μ-Br)]2, or [Pd{C6H3(CH2NH2)-2}(μ-Br)]2 are obtained. Alternatively, the hydrochloride of 4-XC6H4CH2NH2 (X = F, NO2) can also be used to prepare the corresponding [Pd{C6H3(CH2NH2)-2,X-5}(μ-Cl)]2 complexes. These results show that primary benzylamines can be orthometalated even if the substituents are electron-withdrawing groups and that 2-(phenyl)ethylamine can be orthometalated in spite of the six-membered ring that it forms. These reactions occur via intermediate complexes [Pd(OAc)2L2], which react with [Pd(OAc)2]3 to give the dimeric species [Pd(OAc)(μ-OAc)L]2 (L = amine), from which in turn the orthometalated complexes are formed. Each of these steps has been studied, and both types of intermediates have been isolated for all the amines. PPh3 reacts with the orthometalated complexes to give the corresponding products of the bridge splitting. The crystal structures of [Pd(OAc)(μ-OAc)L]2 (L = 4-O2NC6H4CH2NH2) and [Pd{C6H4(CH2CH2NH2)-2}Br(PPh3)] have been determined by X-ray diffraction.

The reaction between [Pd(C6H3NNR-2, X-5)Cl]2 and phosphines gives [Pd(C6H3NNTo-2,Me-5)Cl(L)] [To = C6H4Me-4, L = PEt3 (1a), PPh2Me (1b)] or trans-[Pd(C6H3N2To-2,Me-5)ClL2] (L = PEt3 (2a), PPh2Me (2b), L2 = bis(diphenylphosphino)methane = dppm (2c)) or trans-[Pd(C6H3N2X-2, R-5)Cl(μ-dppm)]2 (X = Me, R = To (3a); X = H, R = Ph (3b)), depending on the molar ratio of the reagents. Tl(OTf) (OTf = O3SCF3), AgClO4, or AgSbF6 react with 1a,b, 2a, 2c, or 3a to give, variously, [Pd(C6H3NNTo-2,Me-5)(Y)(L)] (L = PEt3, Y = TfO (4a); L = PPh2Me, Y = TfO (4b), ClO4 (4b‘)), trans-[Pd(C6H3N2To-2,Me-5)(OTf)(PEt3)2] (5), [Pd(C6H3N2To-2,Me-5)(η1-dppm)(η2-dppm)]TfO (6), or [Pd(C6H3NNR-2,X-5)(η2-dppm)]Y (X = Me, R = To, Y = TfO (7a)). Complexes [Pd(C6H3NNR-2,X-5)(η2-dppm)]SbF6 (X = Me, R = To (7a‘); X = H, R = Ph (7b)) can be prepared by reacting [Pd(C6H3NNR-2,X-5)Cl]2 with AgSbF6 and dppm. Complex 4b‘ reacts with PPh2Me to give [Pd(C6H3N2To-2,Me-5)(PPh2Me)3]ClO4 (8). Attempts to obtain single crystals of 4a, [Pd(C6H3NNR-2,X-5)(PPh3)(Me2CO)]ClO4, or 7b lead to different products. From 4, an insertion into the Pd−OTf bond of one molecule of water gives [Pd(C6H3NNTo-2,Me-5(OH2···OTf)(PEt3)] (9) while substitution of the acetone molecule by two water molecules occurs in the second case to give [Pd(C6H3NNTo-2,Me-5){(μ3-OH2)(···OClO3)(···OH2)}(PPh3)] (10). Finally, ready oxidation in the air of 7b gives [Pd(C6H4NNPh-2)(η2-dppmO)]SbF6 (11) [dppmO = bis(diphenylphosphino)methane monoxide]. [Pt(PPh3)3] reacts with [Hg(C6H3N2To-2, Me-5)Cl] to give trans-[Pt(C6H3N2To-2,Me-5)Cl(PPh3)2] (12), which in turn reacts with Tl(OTf) to give [Pt(C6H3NNTo-2,Me-5)(PPh3)2]TfO (13). Crystal structures of 2c· 1 / 2 CH 2 Cl 2 , 4b‘, 5, 6, 7a, 9, 10, and 11·2MeOH have been determined.

The ortho-metalated complex (S,S)-[Pd2{κ2(C,N)-C6H4CH2CH(CO2Me)NH2-2}2(μ-Br)2] (1b) can be prepared by refluxing in acetonitrile equimolecular amounts of Pd(OAc)2 and l-phenylalanine methyl ester hydrochloride, followed by addition of an excess of NaBr. Complex 1b reacts with 4-picoline to give the mononuclear derivative (S)-[Pd{κ2(C,N)-C6H4CH2CH(CO2Me)NH2-2}2Br(NC5H4Me-4)] (2), whose crystal structure has been determined by X-ray diffraction. The precursor of 1b, (S,S)-[Pd2{κ2(C,N)-C6H4CH2CH(CO2Me)NH2-2}2(μ-Cl)2] (1a), could not be isolated in a pure form, but it can be used as the starting material for the synthesis of functionalized derivatives of the phenylalanine methyl ester. Thus, CO and RNC (R = Xy, t Bu) insert into the Pd−C bond of 1a to afford, after depalladation, (S)-1-oxo-3-(methoxycarbonyl)-1,2,3,4-tetrahydroisoquinoline (3) and (S)-1-R-3-(methoxycarbonyl)-3,4-dihydroisoquinolinium triflate (R = tBu (4), Xy (5)), respectively. Reaction of complex 1b with bromine or iodine affords trans-(S,S)-[PdBr2{NH2CH(CO2Me)CH2C6H4-X-2}2] (X = Br (6), I (7)), which further reacts with 1,10-phenanthroline (phen) to give [PdBr2(phen)] and (S)-2-X-phenylalanine methyl ester (X = Br (8), I (9)).

We have studied the reactivity of the complexes [Pd(C6H4X-2)Br(bpy)] (bpy = 2,2‘-bipyridine; X = C(O)Me (1a), CN (1b), CHO (1c)), [Pd{C6H4CHCH2-2}(PPh3)(bpy)](TfO) (TfO = CF3SO3; 2d), trans-[Pd(C6H4X-2)Br(PPh3)2] (X = C(O)Me (3a), CN (3b), CHCH2 (3d)), and [Pd(μ-Br)(C6H4X-2)(PPh3)]2(X = C(O)Me (4a), CN (4b)). Their reactions with XyNC (Xy = 2,6-dimethylphenyl) depend on the nature of X and the other ligands and on the reaction conditions. The products of these reactions are mono- and triinserted complexes. Among the former are [Pd{C(NXy)C6H4X-2}Br(L2)] (L2 = bpy, X = C(O)Me (5a), CN (5b); L = CNXy, X = C(O)Me (6a), CN (6b), CHCH2 (6d)) and trans-[Pd{C(NXy)C6H4CHCH2-2}(CNXy)2(PPh3)](TfO) (7d). The reaction of 1c with XyNC (1:5 molar ratio) gives 10, a product resulting after substitution of bpy, coordination of two molecules of XyNC, triinsertion of XyNC, and a cyclization resulting after the attack of the nitrogen of the first inserted molecule at the carbon atom of the formyl group. The complexes [Pd{κ2 C 1,N 3-C(NXy)C(NXy)C(NXy)C6H4X-2}Br(CNXy)] (X = C(O)Me (8a), CN (8b)) were obtained by reacting (i) 3a or 3b with XyNC (1:4 molar ratio) or (ii) Pd(dba)2 (dba = dibenzylideneacetone) with BrC6H4X-2 and XyNC (1:1:4 molar ratio). When this oxidative addition reaction was carried out with BrC6H4CHO-2, the resulting product decomposed to give the Pd(I) complex [Pd2Br2(CNXy)4] (9). Tl(TfO) was reacted with (i) 8a and 8b (1:1 molar ratio) to give the corresponding triflato complexes 11a and 11b, (ii) 4a (1:2 molar ratio) in the presence of moisture to give the cyclopalladated aquo complex [Pd{κ2 C,O-C6H4{C(O)Me-2}(OH2)(PPh3)](TfO) (12a), and (iii) 4b (3:1 molar ratio) to give [Pd(C6H4CN-2)(κ2 N,N- 4b)(PPh3)](TfO) (13b), in which 4b behaves as a ligand through the two cyano groups. The crystal structures of 5b, 6b, 7d, 8a,b, 9, 10, 11a,b, 12a, and 13b have been determined by X-ray diffraction studies.

Reactions of AuCl(tht) (tht = tetrahydrothiophene) with various ylides in equimolar amounts give the complexes [AuCl(ylide)]X n (n = 0, ylide = C(PPh3)2 (1a), 4-MeC6H4SO2CHPPh3 (1b); n = 1, X = TfO, ylide = [HC(PPh3)2]+ (2)) and [(AuCl)2{μ-C(PPh3)2}] (3) when using a 2:1 molar ratio. The complex 1a reacts (i) with Tl(acac) to give [Au(acac){C(PPh3)2}] (4) and (ii) with terminal alkynes (with or without added Et3N) to give [HC(PPh3)2][Au(C⋮CC6H4R-4)Cl] (R = H (5a), CN (5b), OMe (5c), NO2 (5d)) instead of the desired complexes [Au(C⋮CC6H4R-4){C{PPh3}2}]. These complexes (R = H (6a), CN (6b), OMe (6c), NO2 (6d), C⋮CPh (6e)) were prepared by the reaction of [Au(acac){C(PPh3)2}] (4) with a large excess of alkynes (ca. 1:25−30). Complex 1b reacts with terminal alkynes in the presence of Et3N differently from 1a, giving the complexes [Au(C⋮CC6H4R-4){CH(PPh3){S(O)2C6H4Me-4}}] (R = H (7a), NC (7b), OMe (7c), NO2 (7d), C⋮CPh (7e)). The reaction of PPN[Au(acac)2] with the phosphonium salt [H2C(PPh3)2](TfO)2 or [4-MeC6H4S(O)2CH2PPh3]TfO in 1:2 stoichiometry afforded the cationic complex [Au(ylide)2](TfO) n , where the ylide is [HC(PPh3)2]+ (n = 3, 8a) or 4-MeC6H4S(O)2CHPPh3 (n = 1, 8b), respectively. The crystal structures of [4-MeC6H4S(O)2CH2PPh3]TfO, 1b·0.5CH2Cl2, 3·3CH2Cl2, 5a, 5c, 6d·THF, and 8b have been determined.

AuCl(SMe 2 )] reacts with HCtCR (R ) bpyl ) 2,2′-bipyridine-5-yl (1), phtpyl ) phenyl-4-(2,2′: 6′,2′′-terpyridine-4-yl) (2)) and NEt 3 (1:1:3) to afford the polymers [Au(CtCR)] n (R ) bpyl (3), phtpyl (4)). The new alkyne HCtCphccbpyl (5, phccbpyl ) 4-C 6 H 4 CtCbpyl) has been prepared by Sonogashira coupling of 4-Me 3 SiCtCC 6 H 4 I and 1 followed by desilylation of the resulting alkyne 4-Me 3 SiCtCphccbpyl. The alkynyl Au(I) complexes [Au(CtCR)L] (R ) bpyl, L ) PPh 3 (6), PTol 3 (7, Tol ) 4-MeC 6 H 4 ), PEt 3 (8); R ) phtpyl, L ) XyNC ( 9), PPh 3 (10); R ) phccbpyl, L ) PPh 3 ( 11)) have been prepared by reacting: (1) 3 or 4 with L or (2) the corresponding alkyne 1, 2, or 5 with [Au(acac)(PPh 3 )] (acac ) acetylacetonato). The reaction of 3 or 4 with diphosphines gives [{Au(CtCR)} 2 (µ-Ph 2 P(CH 2 ) x PPh 2 )] (R ) bpyl, x ) 1 (12), 2 (13), 4 (14), 10 (15); R ) phtpyl, x ) 10 ( 16)). ESI mass spectrometric studies show that complexes 12-14 are in equilibrium with the salts [Au 3 (CtCbpyl) 2 (µ-Ph 2 P(CH 2 ) x PPh 2 ) 2 ][Au(CtCbpyl) 2 ], although only when x ) 1 ( 17) was a significant concentration of the salt detected by NMR spectroscopy and isolated. The anionic complexes PPN[Au(CtCR) 2 ] (R ) bpyl ( 18), phtpyl ( 19), or phccbpyl ( 20)) have been prepared by reaction of the corresponding alkynes with PPN[Au(acac) 2 ]. Complexes 6, 10, 13, 14, 17, and 18 have been characterized by single-crystal X-ray diffraction studies. The alkynyl complexes are luminescent at room temperature, displaying dual emissions.

The palladated primary amines [Pd{C 6 H 3 CH 2 NH 2 -2-X-5}(µ-Br)] 2 [X ) H (1a), OMe (1b), NO 2 (1c), F (1d)] react with isocyanides (Pd:RNC ) 1:1) to give [Pd{C 6 When XyNC reacts with 1a (Pd:RNC ) 1:2) or with 2a (Pd:RNC ) 1:1), the complex [Pd{(CdNXy)C 6 H 4 CH 2 NH 2 -2}(XyNC)Br] (4a) is obtained. The reactions of complexes 1 with isocyanides in the ratio Pd:RNC ) 1:3 lead to Pd(I) complexes [Pd 2 Br 2 L 4 ] [L ) XyNC (5); L ) t Bu ( 6)]. On the basis of NMR data we propose the following reaction pathway for this reduction process: (1) formation of the corresponding monomer 2 or 3, (2) insertion of one molecule of the isocyanide into the Pd-C bond of 2 or 3 to give [Pd{(CdNR)C 6 H 3 CH 2 NH 2 -2-X-5}(RNC)Br], (3) cleavage of the N-Pd bond and coordination of a new isocyanide molecule to give complexes [Pd{(CdNR)C 6 H 3 CH 2 NH 2 -2-X-5}(RNC) 2 Br][detected in solution for R ) Xy, X ) H (7a) and isolated as an acetylated derivative of this complex [Pd{(CdNXy)C 6 H 4 CH 2 NHC(O)Me-2}(XyNC) 2 Br] (8a)], and (4) decomposition of these complexes to give 5 or 6. The organic product of these reactions was not identified. By refluxing mixtures of complexes 1 with RNC and TlOTf (Pd:RNC:TfO ) 1:1:1) the corresponding isoindolinium triflates 9‚OTf [R ) Xy, X ) H (9a‚OTf), OMe (9b‚OTf), F (9d‚OTf)] or 10‚OTf [R ) t Bu, X ) H (10a‚OTf), OMe (10b‚OTf), F (10d‚OTf)] were isolated and characterized. A mechanism of formation of these isoindolinium triflates is proposed. When the reaction between 1a and XyNC (Pd:RNC ) 1:1) was carried out in refluxing toluene in the absence of TlOTf, or when 2a was refluxed in toluene, an insertion of the isocyanide occurs in both cases to give [Pd{(CdNXy)C 6 H 4 CH 2 NH 2 -2}Br] 2 (11). If 1a or 2a is reacted with XyNC (Pd:RNC ) 1:1.25 or 1:0.25, respectively), the complex [PdBr 2 {2-(XyNH)-isoindole} 2 ] (12) is formed. A proposal for the reaction pathway of this process is discussed. The crystal structures of 3d, 9a‚OTf, and 12 have been determined.