1,3-Di(2-pyridyl)benzene undergoes regioselective orthometalation with Pd(OAc)2 on the central aryl ring, giving rise to a dimeric complex in which four acetate units act as bridges between two doubly metalated ligands and each pyridine ligand coordinates to a different metal atom. The reaction with chloride-containing Pd(II) complexes does not lead to C−H activation but to coordination complexes without Pd−C bonds. Cycloplatination of 1,3-di(2-pyridyl)benzene takes place at C-2 of the benzene ring, generating a terdentate ligand. This behavior is the same as that previously observed for Ru and Os. Both orthometalated complexes have been structurally characterized by X-ray diffraction.

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 complexes [Pd(C 6 H 4 X-2)BrL 2 ] (L 2 ) trans-(PR 3 ) 2 , R ) Ph, X ) CHdCH 2 (1a), CHO (1b), C(O)Me (1c), CN (1d) CN (2d′)) have been prepared by oxidative addition of the corresponding bromoarene BrC 6 H 4 X-2 to "Pd(dba) 2 " ()[Pd 2 (dba) 3 ]‚dba, dba ) dibenzylideneacetone) in the presence of the appropriate ligand. The compound [Pd{C 6 H 4 (CHdCH 2 )-2}(bpy)(PPh 3 )]TfO (3a; TfO ) CF 3 SO 3 ) has been obtained by reacting 1a with bpy in the presence of TlOTf. The cyclopalladated [Pd{κ 2 -C,O-C 6 H 4 {C(O)Me}-2}(bpy)]TfO (4c) has been prepared from 2c and TlOTf. The dimeric complexes [Pd(µ-Br) 5b′′), CN (5d′′)) have been synthesized by reacting complexes 1b-d with [PdCl 2 (NCPh) 2 ] in a 2:1 molar ratio or C 6 H 4 Br-1-X-2 with "Pd(dba) 2 " and P(o-To) 3 in 1:1:1 molar ratio. The latter method leads to the monomericThe complex 2c reacts with the alkyne PhCtCPh or EtCtCEt and TlOTf to give 1-methyl-2,3-diphenyl-1H-indenol (7) or 1-methyl-2,3-diethyl-1H-indenol (8), respectively. The crystal structures of complexes 1a‚2CH 2 Cl 2 , 1b‚CH 2 Cl 2 , 2b,d, and 6c′′ have been determined by X-ray diffraction studies. An interesting supramolecular layered structure is formed through CN‚‚‚H-C bpy and Br‚‚‚H-C bpy hydrogen bonds in complex 2d.

Reaction of the iminophosphorane Ph3PNC6H4Me-4 (1a) with Hg(OAc)2 and LiCl gives the mercurated iminophosphorane [Hg{C6H3(NPPh3)-2-Me-5}Cl] (2). The latter reacts with NaBr to give [Hg{C6H3(NPPh3)-2-Me-5}Br] (3). 2 reacts with MeC6H4NCO-4 or CX2 (X = O, S) to give [Hg{C6H3(NCNC6H4Me-4‘)-2-Me-5}Cl] (4) or [Hg{C6H3{NCNC6H3(HgCl)-1‘-Me-5‘}-2-Me-5}Cl] (5), respectively. Iminophosphoranes Ph3PNC6H4R-4 (1b) react with Pd(OAc)2 to give the complexes [Pd{κ2-C,N-C6H4(PPh2NC6H4R-4‘)-2}(μ-OAc)]2 (R = Me (6a), MeO (6b)), in which the palladation takes place at one of the phenyl substituents of the PPh3 group. Complex 6b reacts with NaBr or t BuNC to give [Pd{κ2-C,N-C6H4(PPh2NC6H4OMe-4‘)-2}(μ-Br)]2 (7) or [Pd{κ2-C,N-C6H4(PPh2NC6H4OMe-4‘)-2}(OAc)(CN t Bu)] (8), respectively. Complexes 6a,b react with NaClO4 and N,N,N ‘,N ‘-tetramethylethylenediamine (tmeda), yielding [Pd{κ2-C,N-C6H4(PPh2NC6H4R-4‘)-2}(tmeda)]ClO4 (R = Me (9a), MeO (9b)). The compound Ph3PNC6H4I-2 (1c) adds oxidatively to [Pd2(dba)3]·dba (dba = dibenzylideneacetone) in the presence of tmeda, resulting in the formation of complex [Pd{C6H4(NPPh3)-2}I(tmeda)] (10). The complex 10 reacts (i) with PPh3 and TlOTf (TfO = CF3SO3) to give [Pd{C6H4(NPPh3)-2}(tmeda)(PPh3)]TfO (11·TfO), (ii) with XyNC (Xy = C6H3Me-2,6) (1:3 molar ratio) to give [Pd{κ2-C,N-C(NXy)C6H4(NPPh3)-2}I(CNXy)] (12), and (iii) with XyNC and TlOTf (1:3:1) to give [Pd{κ2-C,N-C(NXy)C6H4(NPPh3)-2}(CNXy)2]TfO (13). An excess of the alkyne MeO2CC⋮CCO2Me reacts with 10 and AgClO4 (4:1:1) to give the inserted compound [Pd{κ2-C,N-C(CO2Me)C(CO2Me)C6H4(NPPh3)-2}(tmeda)]ClO4 (14·ClO4). The crystal structures of 2, 6a·CH2Cl2, 9a, 11·TfO, and 14·ClO4 have been determined by X-ray diffraction studies.