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Treatment of bis(iminophosphorane)phosphane ligands 2a–2e with Li2PdCl4 gave a set of novel diphosphane-derived complexes bearing two metallacycle rings, each one enclosing a P=N double bond: the unprecedented bis(iminophosphorane)phosphane-[C,N,S] palladacycles. In the case of the ligand derived from bis(diphenylphosphino)methane, 2a, both the single and the double palladacycle complexes were obtained. Reaction of 3a with bis(diphenylphosphino)ethane did not yield the expected product with the diphosphane bonded to both palladium atoms, but rather the novel coordination compound 5. The crystal structures of 3c and 5 are described.

Treatment of the double nuclear complex 1a, di-μ-cloro-bis[N-(4-formylbenzylidene)cyclohexylaminato-C6, N]dipalladium, with Ph2PCH2CH2)2PPh (triphos) and NH4PF6 gave the single nuclear species 2a, 1-N-(cyclohexylamine)-4-N-(formyl)palladium(triphos)(hexafluorophasphate). Reaction of 2a with Ph2PCH2CH2NH2 in refluxing chloroform via a condensation reaction of the amine and formyl groups to produce the C=N double bond, gave 3a, 1-N-(cyclohexylamine)-4- N-(diphenylphosphinoethylamine)palladium(triphos)(hexafluorophasphate); a potentially bidentate [N,P] metaloligand. However, attempts to coordinate a second metal by treatment of 3a with [PdCl2(PhCN)2] were to no avail. Notwithstanding, complexes 2a and 3a left to stand in solution spontaneously self-transformed to give in either case the double nuclear complex 10, 1,4-N,N-terephthalylidene(cyclohexilamine)-3,6-[bispalladium(triphos)]di(hexafluorophosphate), after undergoing further metalation of the phenyl ring, then bearing two mutually trans [Pd(Ph2PCH2CH2)2PPh)-P,P,P] moieties: an unprecedented and serendipitous result indeed. On the other hand, reaction of the double nuclear complex 1b, di-μ-cloro-bis[N-(3-formylbenzylidene)cyclohexylaminato-C6, N]dipalladium, with Ph2PCH2CH2)2PPh (triphos) and NH4PF6 gave the single nuclear species 2b, 1-N-(cyclohexylamine)-4-N-(formyl)palladium(triphos)(hexafluorophasphate), Treatment of 2b with H2O/glacial MeCOOH gave cleavage of the C=N double bond and of the Pd···N interaction, yielding 5b, isophthalaldehyde-6-palladium(triphos)hexafluorophosphate, which then reacted with Ph2P(CH2)3NH2 to yield complex 6b, N,N-(isophthalylidene(diphenylphosphinopropylamine)-6-(palladiumtriphos)di(hexafluorophosphate), with two pairs of non-coordinated nitrogen and phosphorus donor atoms. Treatment of 6b with [PdCl2(PhCN)2], [PtCl2(PhCN)2], or [PtMe2(COD)] gave the new double nuclear complexes 7b, 8b and 9b, palladiumdichloro-, platinumdichloro- and platinumdimethyl[N,N-(isophthalylidene(diphenylphosphinopropylamine)-6-(palladiumtriphos)(hexafluorophosphate)-P,P], respectively, showing the behavior of 6b as a palladated bidentate [P,P] metaloligand. The complexes were fully characterized by microanalysis, IR, 1H, and 31P NMR spectroscopies, as appropriate. The X-ray single-crystal analyses for compounds 10 and 5b have been previously described as the perchlorate salts by JM Vila et al.

Treatment of the imines a–c with palladium(II) acetate in acetic acid yielded the μ-acetate dinuclear complexes 1a–c, which readily reacted with sodium chloride or bromide to provide μ-halide analogues. The reaction of the latter with nitrogen, phosphorus and oxygen donor nucleophiles yielded new imine palladacycles following the cleavage of the Pd2X2 unit. The complexes were fully characterized by microanalysis, 1H, 13C and 31P NMR spectroscopies, as appropriate. The compounds were applied as catalysts in the Suzuki–Miyaura coupling reaction in aqueous and semi-aqueous media.

A solution of compound 3 in dichloromethane produced a crystalline solid whose crystal structural analysis yielded a molecular structure with an asymmetric unit comprising two different palladacycles: the acetylacetonate complex 3 and the chloro–bridged dinuclear compound 2. The parent solution was examined by IR and NMR spectroscopy showing the conversion of 3 into 2, which may be due to traces of chloride ion in the form of acid present in the solvent, whereas an acid‑free solution of compound 3 remained unchanged. DFT calculations of the transformation have been carried out.

Reaction of the thiosemicarbazones 3-FC6H4C(Me)=NN(H)C(=S)NHR, (R = Et, a; Ph, b) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complexes [Pd{3-FC6H3C(Me)=NN=C(S)NHR}]4 (1a, 1b). Reaction of 1a, 1b with the tertiary phosphines dppm, dppe, dppp, dppb or trans-dppen in 1:2 M ratio gave [(Pd{3-FC6H3C(Me)=NN=C(S)NHR})2(μ-PPh2(CH2)nPPh2)], (n = 1, 2a-b; 2, 3a-b; 3, 4a-b; 4, 5a-b), [(Pd{3-FC6H3C(Me)=NN=C(S)NHR})2(μ-PPh2CH=CHPPh2)], (6a-b). Treatment of 1a, b with dppm in 1:4 M ratio gave the mononuclear complexes [Pd{3-FC6H3C(Me)=NN=C(S)NHR}(Ph2PCH2PPh2-P)] (7a-b). Reaction of the latter with an equimolar amount of [PdCl2(PhCN)2] gave [PdCl2{Pd[3-FC6H3C-(Me)=NN=C(S)NHR](PPh2CH2PPh2)-P,S}], (8a-b). The molecular structure of ligands a and b, and of complex 6a have been determined by X-ray diffraction analysis. The ligands and complexes have also been characterized by Density Functional Theory (DFT) calculations in order to obtain structural information for the species for which no X-ray data were available.

Treatment of a or b with Li2[PdCl4] in methanol at room temperature for 48 h, gave the tetrametallic chlorine bridged complexes [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(μ-Cl)]2, 1a and 1b, containing a cyclic acetal on the metallated cyclopentadienyl ring. The reactions of 1a and 1b with the Ph2P(CH2)nPPh2 diphosphines in a 1:1 ratio gave the tetrametallic species [{Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(Cl)}2(μ-Ph2P(CH2)nPPh2)], n = 1–4 as appropriate, 2a–5a and 2b–5b, with the diphosphine in a bridging mode and terminal chlorine ligands. Treatment of 1a and 1b with monophosphines yielded the dimetallic compounds [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)NR]}(Cl)(L)] (L = PPh3, PPh2Me, PPh2Et) 6a–8a and 6b–7b. Reaction of the phosphine derivatives with aqueous acetic acid gave the corresponding functionalized compounds with transformation of the 1,3-dioxane ring into a formyl group on the metallated ring 9a–15a and 9b–14b. Reaction of 8a with acetic acid in methanol gave [Pd{CpFe[η5-C5H2{CH(OMe)2}C(H)N-2,4,6-Me3C6H2]}(Cl)(PPh2Et)] 16a, after a transacetalization reaction with an acetal moiety –CH(OMe)2 on the metallated five-membered ring. The molecular structure of compound 16a has been determined by X-ray diffraction analysis.

Bimetallic cyclometallated palladium(II) complexes readily react with silver perchlorate and tertiary diphosphines to give dipalladium compounds with terdentate [C,N,S] thiosemicarbazones, and with bridging and chelating [P,P] ligands, of the type [Pd(Ph2PCH2PPh2-P,P){Pd[4-MeOC6H3C(Me)NNC(S)NHMe](Ph2PCH2PPh2)-P,S}] [ClO4]2, 1a. The crystal structures of complexes [PdCl2{Pd[2-MeOC6H3C(Me)NNC(S)NHMe](Ph2PC(CH2)2PPh2)-P,S}] and [Pd(Ph2PCH2PPh2-P,P){Pd[3-MeOC6H3C(Me)NNC(S)NHMe](Ph2PC(CH2)2P-Ph2)-P,S}]-[ClO4]2, 6 and 4a, respectively, are the first reported examples of palladacycles with the diphosphine Ph2PC(CH2)2PPh2, bis(diphenylphosphine)cyclopropane (dcpc), in the bridging mode. The short-bite diphosphines produce strained four-membered rings at the metal; the structures for 1a and 4a show the P–C–P carbon atom puckered away from the metal coordination plane.

Treatment of the mononuclear complex [Pd{2,4-(MeO 2 )C 6 H 2 C(H) N(Cy)- C6,N }{(Ph 2 P) 2 C CH 2 - P,P ′}][PF 6 ] ( 1 ) with methyl 2-oxocyclopentanecarboxilate, α-acetylbutyrolactone or methyl phenylsulfonylacetate in the presence of anhydrous sodium carbonate yielded the addition products [Pd{2,4-(MeO) 2 C 6 H 2 C(H) N(Cy)- C6,N }{(Ph 2 P) 2 CHCH 2 C(R 1 )(R 2 )- P,P ′}][PF 6 ] (R 1 = COOCH 3 , R 2 = COCH 2 CH 2 CH 2 , 2 ; R 1 = COCH 3 , R 2 = COOCH 2 CH 2 , 3 ; R 1 = COOCH 3 , R 2 = SO 2 Ph, 4 ) in high yield. The existence of two chiral carbon atoms in the diphosphine moiety produces the existence of optical isomers. Reaction of 1 with acetone and potassium tert-butoxide afforded complex [Pd{2,4-(Me) 2 C 6 H 2 C(H) N(Cy)- C6,N }{(Ph 2 P) 2 CHCH 2 CH 2 COCH 3 - P,P ′}][PF 6 ] ( 5 ), via C–C bond formation. Complex 1 reacts in methanol and in ethanol to give the corresponding addition products [Pd{2,4-(MeO) 2 C 6 H 2 C(H) NCy- C6,N }{(Ph 2 P) 2 CHCH 2 OR- P,P ′}][PF 6 ] (R = CH 3 , 6 ; R = CH 2 CH 3 , 7 ) , via C–O bond formation. Treatment of complex 1 with cyclohexylamine or dimethylhidrazine gives place to [Pd{2,4-(MeO) 2 C 6 H 2 C(H) N(Cy)- C6,N }{(Ph 2 P) 2 CHCH 2 N(H)R– P,P ′}][PF 6 ] (R = C 6 H 11 , 8 ; R = N(CH 3 ) 2 , 9 ), via C–N formation. The crystal structure of 7 has been determined by X-ray crystallography and comprises equimolar amounts of the (C16 R ) and (C16 S ) enantiomers. Reaction of compound 1 with dl -alanine or dl -metionine and anhydrous sodium carbonate yields [Pd{2,4-(MeO) 2 C 6 H 2 C(H) N(Cy)- C6,N }{(Ph 2 P) 2 CHCH 2 NHCH(R 1 )(R 2 )- P,P ′}][PF 6 ] (R 1 = CH 3 , R 2 = COOH, 10 ; R 1 = CH 2 CH 2 SCH 3 , R 2 = COOH, 11 ). Treatment of complex 1 with piperazine give rise to the dinuclear compound [{Pd[2,4-(MeO) 2 C 6 H 2 C(H) N(Cy)- C6,N ]} 2 {(Ph 2 P) 2 CHCH 2 N(CH 2 CH 2 ) 2 NCH 2 CH(PPh 2 ) 2 - P,P,P ′ ,P ′}][PF 6 ] 2 12 , in which each N–H bond of the piperazine has been added to the vinylidene bond of one vdpp ligand.

Treatment of thiosemicarbazones (R 1C 6H 4)C(H)NN(H)C(S)NHR 2 [R 1,R 2: 4-Me,H (a); 4-Me,Me (b); 4-Me,Et (c); 2-Me,H (d); 2-Me,Me (e); 2-Me,Et (f)] with cis-[PtMe 2(cod)] afforded the tetranuclear platinum(II) compounds [Pt{(R 1C 6H 3)C(H)NNC(S)NHR 2}] 4 (1a-1f) with the ligand as terdentate [C,N,S] after C-H activation and NH deprotonation. The reaction of 1a-1f with PPh 3 in 1:4 M ratio gave the mononuclear compounds [Pt{(R 1C 6H 3)C(H)NNC(S)NHR 2}(PPh 3)] (2a-2f). Treatment of 1a-1f with large-bite diphosphines Ph 2P(CH 2) nPPh 2 (n = 2, dppe; n = 3, dppp; n = 4, dppb) afforded the dinuclear compounds [{Pt[(R 1C 6H 3)C(H)N-N = C(S)NHR 2]} 2{μ-Ph 2P(CH 2) nPPh 2}], (3a-3f, 4a-4f, 5a-5f), with the diphosphine in a bridging mode. Similar reactions with the short-bite diphosphines Ph 2PCH 2PPh 2 (dppm) and Ph 2PC(CH 2)PPh 2 (vdpp) yielded the mononuclear compounds [Pt{(R 1C 6H 3)C(H)NNC(S)NHR 2}(Ph 2PR 3PPh 2-P)] (R 3 = CH 2, 6a-6f; R 3 = C = CH 2, 7a-7f) with the diphosphine in a monodentate coordination. Treatment of 1a-1f with [W(CO) 5(Ph 2CH 2PPh 2)] gave the heterodinuclear species [{Pt[(R 1C 6H 3)C(H)NNC(S)NHR 2]} {Ph 2CH 2PPh 2W(CO) 5}] (8a-8f). The molecular structures of compounds 3e and 5c have been determined by X-ray crystal structure analysis. © 2012 Elsevier Ltd. All rights reserved.

Reaction of the Schiff base ligands CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)═NR] (R = 2,4,6-Me3C6H2, a; R = Cy, b) derived from the 1,2-disubstituted formylferrocene CpFe[(CHO){C(H)O(CH2)3O}-η5-C5H3] 1, with Li2[PdCl4] in methanol at room temperature for 48 h, gave the chlorine-bridged complexes [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)═NR]}(Cl)]2, 1a and 1b, after C–H activation of the cyclopentadienyl ring bearing the cyclic acetal. The reactions of 1a and 1b with the Ph2P(CH2)nPPh2 diphosphines in a 1:2 ratio, plus addition of ammonium hexafluorophosphate, gave the dinucelar compounds [Pd{CpFe[η5-C5H2{C(H)O(CH2)3O}C(H)═NR]}-(Ph2P(CH2)nPPh2-P,P)][PF6] 2a, 3a and 2b, 3b with the diphosphine in a chelating mode, as 1:1 electrolytes. Treatment of the latter with aqueous acetic acid gave the corresponding functionalized compounds with transformation of the 1,3-dioxane ring into a formyl group on the metalated ring, 4a, 5a and 4b, 5b.The Schiff base condensation reaction of 5b with 2-(methylthio)aniline in refluxing chlorofo...

Reaction of the thiosemicarbazones 3-FC6H4C(Me)NN(H) C(S)NHME a, 4-FC6H4C(Me)NN(H)C(S)NHEt b, and 2-BrC 6H4C(Me)NN(H)C(S)NHPh c, with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complexes [Pd{3-FC6H3C(Me)NNC(S)NHMe}] 4 1a, [Pd{4-FC6H3C(Me)NNC-(S)NHEt}]4 1b, and [Pd{2-BrC6H3C(Me)NNC(S)NHPh}]4 1c. Reaction of 1a-c with the diphosphines Ph2P(CH2) nPPh2 dppm (n = 1), dppe (n = 2), dppp (n = 3), dppb (n = 4) or Ph2PCHCHPPh2 trans-dppe, in a 1:2 molar ratio gave the dinuclear phosphine-bridged complexes [(Pd{XC6H 3C(Me)NNC(S)NHR})2(μ-Ph2P(CH 2)nPPh2)] 2a-c, 3a-c, 4a-c, 5a-c (n = 1-4) and [(Pd{XC6H3C(Me)NNC(S)NHR})2(μ-Ph 2PCHCH-PPh2)] 6a-c. Treatment of 1a-c with PPh 2CH2PPh2, dppm, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{XC6H3C(Me)NNC(S) NHR}-(Ph2PCH2PPh2-P)] 7a-c; however, the diphosphines with n ≥ 2 failed to give the analogous reaction. The molecular structures of 1a, 1b and 3c have been determined by X-ray diffraction analysis and the intra- and intermolecular interactions are discussed. © 2011 Elsevier Ltd. All rights reserved.

The reaction of the tetranuclear halide-bridged complexes 1−2(a−d) with Ph2PCH2PPh2 (dppm) or Ph2PC( CH2)PPh2 (vdpp) in 1:2 molar ratio and NH4PF6 afforded the novel tetarnuclear palladacycles 3−6 (a, c, d) as 1:2 electrolytes with bridging diphosphine and halogen ligands. The structure of 4a has been determined by X-ray diffraction analysis, and represents the first example of a tetranuclear palladacycle with bridging dppm and halogen ligands. Reaction of 1−2(a−d) with (Ph2PCH2CH2)2PPh (triphos) in 1:2 molar ratio gave 7(a−d) bearing two pentacoordinated palladium atoms. The structure of 7a, as determined by X-ray diffraction analysis, shows the distorted square pyramidal geometry around the metal centers. Treatment of 1−2(a−d) with dppm, vdpp or Ph2PN(Me)PPh2 (dppma) in 1:4 molar ratio gave the dinuclear palladacycles 8−10(a−d) with a chelating diphosphine ligand at each metal center; further treatment of 9(a−c) with the nucleophiles pyrrolidine, piperidine, morpholine or 4-methyl-piperidine gave the Michael addition derivatives 11−12(a−c), 13b, 13c and 14c, promoted by the withdrawing effect of the palladacycle which activates the C CH2 double bond.

Treatment of the thiosemicarbazones 4-FC6H4C(Me) NN(H)C( S)NHR, (R = Me, a; Ph, b) and 2-ClC6H4C(Me) NN(H)C( S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC6H3C(Me) NN C(S)NHR}]4 (1a, 1b) and [Pd{2-ClC6H3C(Me) NN C(S)NHPh}]4 (1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC6H3C(Me) NN C(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC6H3C(Me) NN C(S)NHPh})2(μ-Ph2PCH CHPPh2)], (3a, 3b) and [(Pd{2-ClC6H3C(Me) NN C(S)NHR})2(μ-Ph2P(CH2)nPPh2)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC6H3C(Me) NN C(S)NHPh})2(μ-PPh2CH CHPPh2)], (3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.

Treatment of the Schiff-base ligands C 6 H 5 C(H)=C(R)C(H)=NCy (R=H, a; R=Me, b) with Pd(OAc) 2 gave the acetato-bridged dinuclear compounds [Pd{C 6 H 5 C=C(R)C(H)=NCy}(O 2 CMe)] 2 (R=H, 1a; R=Me, 1b) after C-H activation of the aliphatic carbon atom. Reaction of 1a and 1b with aqueous sodium chloride gave the dinuclear chloro-bridged compounds [Pd{C 6 H 5 C=C(R)C(H)=NCy}(X)] 2 (R=H, 2a; R=Me, 2b), which could also be prepared by treatment of the ligands with Li 2 [PdCl 4 ] in methanol. Reaction of 1a with aqueous sodium bromide or iodide gave the halide-bridged species [Pd{C 6 H 5 C=C(H)C(H)=NCy}(X)] 2 (X=Br, 3a; X=I, 4a). Treatment of 1a and 1b with Tl(acac), Tl(C 5 H 5 ) or PPh 3 , as appropriate, gave the mononuclear complexes [Pd{C 6 H 5 C=C(R)C(H)=NCy}(acac)], (R=H, 5a; R=Me, 3b) [Pd{C 6 H 5 C=C(H)C(Me)=NCy}(C 5 H 5 )] (4b) and [Pd{C 6 H 5 C=C(H)C(Me)=NCy}(PPh 3 )] (5b). © 2002 Elsevier Science B.V. All rights reserved.

Treatment of N-(2-bromobenzylidene)cyclohexylamine, 2-BrC6H4C(H)NCy (a), with tris(dibenzylideneacetone)palladium(0) in refluxing benzene gave the cyclometallated compound [Pd{C6H4C(H)NCy}(Br)]2 (1). Treatment of 1 with thallium acetylacetonate gave the mononuclear cyclometallated compound [Pd{C6H4C(H)NCy}(MeCOCHCOMe)] (2). Reaction of a with palladium(II) acetate in refluxing acetic acid gave the dinuclear Pd(II) compound [Pd{2-BrC6H3C(H)NCy}(O2CMe)]2 (3). Treatment of 3 with aqueous sodium chloride gave the dimer complex [Pd{2-BrC6H3C(H)NCy}(Cl)]2 (4). Reaction of 4 with tertiary phosphines gave the cyclometallated complexes [Pd{2-BrC6H3C(H)NCy}(L)] (5: L=PPh3; 6: L=PEtPh2; 7: L=PMePh2), with the phosphine ligand trans to the imine nitrogen atom. Treatment of 2-Br4,5-(MeO)2C6H2C(H)NCH2CH2NMe2 (b), with palladium(II) chloride in refluxing octane or with tris(dibenzylideneacetone)palladium(0) gave [Pd{4,5-(MeO)2C6H2C(H)NCH2CH2NMe2}(X)] (8: X=Cl; 16: X=Br, respectively) and with the ligand as [C, N, N] terdentate. Treatment of 8 with tertiary phosphines gave [Pd{4,5-(MeO)2C6H2C(H)NCH2CH2NMe2}(Cl)(L)] (9: L=PPh3; 10: L=PEtPh2; 11: L=PMePh2). Reaction of 1,4-{2-Br4,5-(MeO)2C6H2C(H)N}2C6H4 (c), with PdCl2, Li2[PdCl4] or K2[PdCl4] gave the tetranuclear compound [1,4-{Pd[4,5-(MeO)2C6H2C(H)N](Cl)}2C6H4]2 (12), which when treated with tertiary phosphines gave the dinuclear species 13–15. The molecular structure of 2 has been determined by X-ray crystallography.

Reaction of the Schiff base ligand 1,3-[2,3,4-(MeO)3C6H2C(H)NCH2]2C6H4 (1) with palladium(II) acetate in toluene gave the doubly cyclometalated complex [1,3-{Pd[2,3,4-(MeO)3C6HC(H)NCH2](μ-O2CMe)}2C...

The oxidative addition reaction of 1,4-(CN(H)CH2CH2Me2)2-2,5-Cl2C6H2 with tris(dibenzylideneacetone)dipalladium(0) in benzene gave the doubly cyclometallated compound [(Cl)Pd{Me2NCH2CH2N(H)C}C6H2{C(H)NCH2CH2NMe2}Pd(Cl)] (1) with each palladium atom C,N,N′ bonded to the ligand. Treatment of 1 with thallium acetylacetonate gave the dinuclear cyclometallated complex 2 with two chelating acetylacetonate ligands. Reaction of 1 with tertiary monophosphines in a 1–phosphine 1:2 molar ratio gave dinuclear cyclometallated complexes 3–7, in which the palladiumNMe2 bond has been broken, whereas treatment of 1 with silver perchlorate, followed by reaction with PPh3 in a 1–phosphine 1:2 molar ratio gave cyclometallated complex 4 where the ligand remains C,N,N′ bonded and the chloride ligand has been substituted by triphenylphosphine. Treatment of 1 with tertiary diphosphines leads to dinuclear compounds 8, 10 and 11, whilst previous treatment of 1 with silver perchlorate followed by the diphosphine 1,4-bis(diphenylphosphino)butane (dppb) in a 1–diphosphine 1:1 molar ratio yielded the tetranuclear complex 9. Reaction of 1 with the tertiary triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio gave the complex [{(Ph2PCH2CH2)2PPh-P,P,P}Pd{Me2NCH2CH2N(H)C}-C6H2{C(H)NCH2CH2NMe2}Pd{(Ph2PCH2CH2)2PPh-P,P,P}][Cl]2 (12) in which both palladium atoms are pentacoordinated. The crystal structures of 1 and 12 are described.

Treatment of the cyclometallated complexes [Pd{4-MeC 6 H 3 C(Me)NN(H)C(O)NH 2 }(Cl)] ( a ), [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }(Cl)] ( b ) and [Pd{3,4-Me 2 C 6 H 2 C(Me)NN(H)C(O)NH 2 }(Cl)] ( c ) with tertiary monophosphine ligands in a complex–phosphine 1:1 molar ratio yielded [C, N] bonded cyclometallated complexes [Pd{4-MeC 6 H 3 C(Me)NN(H)C(O)NH 2 }(Cl)(L)] ( 1a – 4a ), [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }(Cl)(L)] ( 1b – 4b ) and [Pd{3,4-Me 2 C 6 H 2 C(Me)NN(H)C(O)NH 2 }(Cl)(L)] ( 1c – 4c ), [L=PPh 3 , PMePh 2 , PEtPh 2 and PEt 2 Ph]. Reaction of a , b and c with silver perchlorate, prior to the treatment with the monophosphine gave the [C, N, O] bonded cyclometallated complexes [Pd{4-MeC 6 H 3 C(Me)NN(H)C(O)NH 2 }(L)][ClO 4 ] ( 5a – 8a ), [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }(L)][ClO 4 ] ( 5b – 8b ) and [Pd{3,4-Me 2 C 6 H 2 C(Me)NN(H)C(O)NH 2 }(L)][ClO 4 ] ( 5c – 8c ). Reaction of a , b and c with tertiary monophosphines in a complex–phosphine 1:2 ratio gave the C only bonded non-cyclometallated complexes [Pd{4-MeC 6 H 3 C(Me)NN(H)C(O)NH 2 }(PEt 2 Ph) 2 (Cl)] ( 9a ), [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }(PPh 3 ) 2 (Cl)] ( 9b ) and [Pd{3,4-Me 2 C 6 H 2 C(Me)NN(H)C(O)NH 2 }(PEt 2 Ph) 2 (Cl)] ( 9c ). Treatment of a , b and c with the triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine (trifos) yielded the non-cyclometallated complexes [Pd{4-[MeC 6 H 3 C(Me)NN(H)C(O)NH 2 }{L- P , P , P }][Cl] ( 10a ), [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }{L- P , P , P }][Cl] ( 10b ) and [Pd{3,4-Me 2 C 6 H 2 C(Me)NN(H)C(O)NH 2 }{L- P , P , P }][Cl] ( 10c ) (L=(Ph 2 PCH 2 CH 2 ) 2 PPh). The complexes were characterised by their elemental analysis (C, H, N) and by IR and 31 P-{ 1 H} and 1 H-NMR spectroscopy. [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }(PPh 3 )][ClO 4 ] ( 5b ) and [Pd{C 6 H 4 C(Et)NN(H)C(O)NH 2 }{(Ph 2 PCH 2 CH 2 ) 2 PPh- P , P , P }][Cl] ( 10b ) were characterised crystallographically.

Treatment of the thiosemicarbazones 3-CH3(CH2)5OC6H4C(Me)NN(H)C(S)NH2 (a), 4-MeC6H4C(Me)NN(H)C(S)NH2 (b), C6H5C(Et)NN(H)C(S)NH2 (c), C6H5C{CH3(CH2)10}NN(H)C(S)NH2 (d) and 4-MeC6H4C(Me)NN(H)C(S)NHMe (e) with K2[PtCl4] gives tetranuclear platinum(II) compounds 1a–1e with deprotonation of the NH group and with the ligand acting as a terdentate [C,N,S] moiety. Reaction of 1a–1e with PPh3 and of 1a with P(4-MeOC6H4)3 yielded mononuclear species 2a–2e and 3a, respectively. Treatment of 1a with the diphosphines Ph2PCH2PPh2 (dppm), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp), Ph2P(CH2)4PPh2 (dppb), Ph2P(CH2)5PPh2 (dpppe), Ph2P(CH2)6PPh2 (dpph), and 1,1′-ferrocenebis(diphenylphosphine) (dppf) gives dinuclear compounds 4a–10a. In all cases the PdSchelating bond is strong enough to withstand reaction with the phosphorus ligands without bond cleavage. The molecular structure of 2b has been determined by X-ray crystallography. Mononuclear units are held together by hydrogen bonding, forming dimers in the solid state.

The palladium(II) compound [Pd{3,4-(MeO)2C6H2C(H)NCy}{(Ph2PCH2CH2)2PPh-P,P,P}][PF6] was synthesized and characterized by elemental analysis (C, H, N) and by 1H and 31P{1H} NMR spectroscopy in CDCl3 and 31P{1H} solid-state NMR spectroscopy. The molecular structure was determined by X-ray crystallography, showing it to be the first pentacoordinated cyclometalated palladium(II) complex.

Treatment of the potentially terdentate ligands C6RxH5−xC(H)N–CH2CH2NMe2 [R: a (x=2), 2,4-(MeO)2; b (x=2), 3,4-(MeO)2; c (x=2), 3-Me-4-MeO; d (x=3), 2,3,4-(MeO)3; e (x=2), 4,5-(OCH2O); f (x=1), 2-NO2] with [PtMe2(COD)] gave the platinated compounds [Pt{C6RxH4−xC(H)NCH2CH2–NMe2}(Me)] with two fused five-membered rings at platinum. The crystal and molecular structure of [Pt{3-Me-4-MeOC6H2C(H)NCH2CH2NMe2}(Me)] has been determined by X-ray crystallography. The reactivity of these complexes was tested by the reactions of [Pt{2,4-(MeO)2C6H2C(H)NCH2CH2NMe2}–(Me)] with tertiary phosphines and diphosphines. In the latter case, dinuclear and mononuclear platinum complexes were synthesized, with bridging or chelating diphosphine ligands, respectively, depending on the complex/diphosphine molar ratio used. The reaction of the related potentially hexadentate ligand 1,4-[Me2NCH2CH2N(H)C]2C6H4 with [PtMe2(COD)] gave the metallated compound [(Me)Pt{Me2NCH2CH2N(H)C}C6H2{C(H)N–CH2CH2NMe2}Pt(Me)] with five fused rings.

Treatment of the semicarbazones 4-MeC6H4C(Me)NN(H)C(O)NH2 a, 3,4-Me2C6H3C(Me)NN(H)C(O)NH2 b and C6H5C(Et)NN(H)C(O)NH2 c, gave the [C,N,O] cyclometallated compounds [Pd{4-MeC6H3C(Me)NN(H)C(O)NH2}(Cl)] 1a, [Pd{3,4-Me2C6H2C(Me)NN(H)C(O)NH2}(Cl)] 1b and [Pd{C6H4C(Et)NN(H)C(O)NH2}(Cl)] 1c, after CH activation. Treatment of compounds 1a, 1b, and 1c with silver perchlorate followed by treatment with tertiary diphosphine ligands gave the dinuclear [C,N,O] cyclometallated compounds [{Pd[4-MeC6H3C(Me)NN(H)C(O)NH2]}2(μ-L)][ClO4]2 2a–7a, [{Pd[3,4-Me2C6H2C(Me)NN(H)C(O)NH2]}2(μ-L)][ClO4]2 2b–7b, [{Pd[C6H4C(Et)NN(H)C(O)NH2]}2(μ-L)][ClO4]2 2c–7c, [L=Ph2P(CH2)4PPh2 (dppb), Ph2P(CH2)3PPh2 (dppp), Ph2P(CH2)2PPh2 (dppe), trans-Ph2PCHCHPPh2 (trans-dppe), Ph2PC(CH2)PPh2 (vdpp) and Ph2PCH2PPh2 (dppm)] as 1:2 electrolytes. Reaction of 1a and 1c with diphosphines gave the dinuclear [C,N] cyclometallated compounds [{Pd[4-MeC6H3C(Me)NN(H)C(O)NH2](Cl)}2(μ-L)] 8a, 9a, [{Pd[C6H4C(Et)NN(H)C(O)NH2](Cl)}2(μ-L)] 8c, 9c, [L=Ph2P(CH2)3PPh2 (dppp) and Ph2P(CH2)4PPh2 (dppb)]. The complexes were characterised by their elemental analysis (C,H,N) and by IR and 31P{1H} and 1H-NMR data, and [{Pd[C6H4C(Et)NN(H)C(O)NH2]}2(μ-Ph2P(CH2)3PPh2)][ClO4]2 (3c) was characterised crystallographically.

Treatment of the cyclometallated complexes [{Pd[3-(CHO)C 6 H 3 C(H)NCy}(X)} 2 ] [X=Cl ( 1 ), Br ( 2 ), I ( 3 )] with tertiary monophosphines in a complex/phosphine 1:2 or 1:4 molar ratio afforded the halide-bridged cleaved [Pd{3-(CHO)C 6 H 3 C(H)NCy}(X)(L)] ( 6 – 17 ) and non-cyclometallated complexes [Pd{3-(CHO)C 6 H 3 C(H)NCy}(X)(L) 2 ] ( 18 – 23 ) (X=Cl, Br or I; L=PPh 3 , PEtPh 2 , PEt 2 Ph or PMePh 2 ), respectively. Reaction of 6 – 17 with cyclohexylamine in a complex/amine 1:1 or 1:2 molar ratio gave [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(L)] ( 24 – 28 ) and the non-cyclometallated [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(L)(NH 2 Cy)] ( 29 – 32 ) complexes, respectively. Compounds 18 , 19 and 22 gave [Pd{3-(CyC(H)N)C 6 H 3 C(H)NCy}(X)(PR 3 ) 2 ] ( 33 – 35 ) with two uncoordinated CN groups, when treated with cyclohexylamine. Other reaction routes are also discussed. The complexes were characterised by their elemental analysis (C, H, N) and by IR and 31 P{ 1 H} and 1 H-NMR data, and [Pd{3-(CHO)(C 6 H 3 C(H)NCy}(Br)(PEtPh 2 )] ( 12 ) was characterised crystallographically.

Treatment of Pd(AcO)2 with 1-methyl-2-phenylimidazole, and subsequent treatment with sodium chloride or sodium bromide gave the corresponding halide-bridged cyclometallated complexes [Pdo-C6H4C=NC(H)=C(H)NMe(μ-X)]2 (2, X = Cl; 3, X = Br). Complexes 2 and 3 react with tertiary diphosphines in a 1:1 molar ratio to give dinuclear cyclometallated compounds with bridging diphosphine and halogen ligands [Pdo-C6H4C=NC(H)=C(H)NMe(μ-L-L)(μ-X)]X (4–9) or with only bridging diphosphine ligands [Pdo-C6H4C=NC(H)=C(H)NMe(μ-L-L)(X)2] (10–17), [X = Cl, Br; L-L = Ph2PCH2PPh2 (dppm), Ph2PC(=CH2)PPh2 (vdpp), Ph2PCH(CH3)PPh2 (1,1-dppe), trans-Ph2P(CH=CH)PPh2 (trans-dppe), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)3PPh2 (dppp), Ph2P(CH2)4PPh2 (dppb), as appropriate]. When the reaction is carried out in a 1:2 molar ratio and in the presence of NH4PF6 or NaClO4, mononuclear cyclometallated compounds with a chelating diphosphine ligand are obtained [Pdo-C6H4C=NC(H)=C(H)NMe(L-L-P,P)][Y] (18–27) [Y = PF6, ClO4; L-L = Ph2PCH2PPh2 (dppm), Ph2PC(=CH2)PPh2 (vdpp), Ph2PCH(CH3)PPh2 (1,1-dppe), Ph2PN(CH3)PPh2 (dppma), cis-Ph2P(CH=CH)PPh2 (cis-dppe), Ph2P(CH2)2PPh2 (dppe), Ph2P(CH2)PPh2 (dppp), Ph2P(CH2)4PPh2 (dppb)]. Compounds 18–22 and 25–27 could also be obtained by reaction of complexes 4–17 with the appropriate diphosphine and NH4PF6 or NaClO4. The diphosphines dppma and cis-dppe failed to behave as bridging ligands and only gave mononuclear compounds. The complexes were characterized by their elemental analysis (C, H, N) and by IR and 31P-1H and 1H NMR data. The X-ray crystal structure of complex 22 is described.

Treatment of N-(2-chlorobenzylidene)-N,N′-dimethylethylenediamine, 2-ClC6H4C(H)NCH2CH2NMe2, with tris(dibenzylideneacetone)dipalladium(0) in chloroform gave the oxidative addition cyclometallated product [Pd{C 6 H 4 C(H)NCH 2 CH 2 N Me2}(Cl)] (1) with the palladium atom bonded to a C,N,N′ terdentate donor ligand. Treatment of 1 with tertiary monophosphines gave the cyclometallated complexes [Pd{C 6 H 4 C(H)N CH2CH2NMe2}(Cl)(L)](2: L  PPh3; 3: L  PEtPh2; 4: L  PEt2Ph; 5: L  PEt3), where the phosphine ligand is either trans to the phenyl carbon atom (2, 3) or trans to the imine nitrogen atom (4, 5). Treatment of 1 with silver perchlorate followed by reaction with tertiary monophosphines gave the cyclometallated complexes [Pd{C 6 H 4 C(H)NCH 2 CH 2 N Me2}(L)][ClO4] (6: L  PPh3; 7: L  PEtPh2; 8: L  PEt2Ph; 9: L  PEt3). Reaction of 1 with thallium acetylacetonate gave the cyclometallated complex [Pd{C 6 H 4 C(H)N CH2CH2NMe2}(H3CCOCHCOCH3)] (10). Treatment of 1 with ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C 6 H 4 C(H)N CH2CH2NMe2](Cl)}2(LL)(11: LL = trans-Ph2PCHCHPPh2; 12: LL  Ph2P(CH2)3PPh2;13: LL  Ph2P(CH2)4PPh2), where the phosphorus atom is trans to the phenyl carbon atom. Treatment of 1 with silver perchlorate followed by ditertiary diphosphines in a complex 1/diphosphine 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[C 6 H 4 C(H)NCH 2 CH 2 N Me2]}2 (LL)][ClO4]2 [14: LL=trans-Ph2PCHCHPPh2; 15: LL  Ph2P(CH2)3PPh2; 16: LL  Ph2P(CH2)4PPh2)]. Reaction of 1 with ditertiary diphosphines in a complex 1/diphosphine 1:1 molar ratio, and silver perchlorate as appropriate, gave the cyclometallated complexes [Pd{C 6 H 4 C(H)N CH2CH2NMe2}(Ph2P(CH2)2PPh2-P,P)][ClO4] (17), [Pd{C 6 H 4 C(H)N CH2CH2NMe2}(Ph2P(CH2)3PPh2-P,P)][ClO4] (18), [ Pd{C 6 H 4 C(H)N CH2CH2NMe2}(cis-Ph2PCHCHPPh2-P,P)][Cl] (19) and [Pd{C6H4C-(H)NCH2CH2NMe2}(Cl)(Ph2P(CH2)4PPh2-P,P)] (20).

Treatment of the cyclometallated halide-bridged complexes [1,4-{ Pd [2,3,4-( MeO ) 3 C 6 HC (H) = N ]( X )} 2 C 6 H 4 ] 2 (1a, 2a), [1,4-{ Pd [2,4-( MeO ) 2 C 6 H 2 C(H) = N ]( X )} 2 C 6 H 4 ] 2 (1b, 2b), [1,4-{ Pd [3-( Me -4- MeOC 6 H 2 C(H) = N ]( X )} 2 C 6 H 4 ] 2 (1c, 2c), [1,4-{ Pd [4,5-( OCH 2 O )C 6 H 2 C(H) = N ]( X )} 2 C 6 H 4 ] 2 (1d, 2d), (X = Cl, Br) with ditertiary diphosphines in a complex/diphosphine 1:4 molar ratio and ammonium hexafluorophosphate gave the dinuclear cyclometallated complexes [1,4-{ Pd[2,3,4-(MeO) 3 C 6 HC(H)N ]} 2 C 6 H 4 (LL) 2 ][PF 6 ] 2 [LL  Ph 2 PCH(CH) 3 )PPh 2 , Ph 2 P(CH 2 ) 2 PPh 2 , 3a, 4a], [1,4-{ Pd [2,4-( MeO ) 2 C 6 H 2 C(H) = N ]} 2 C 6 H 4 ( LL ) 2 ][ PF 6 ] 2 [LL  Ph 2 PCH(CH 3 ) PPh 2 , Ph 2 P(CH 2 ) 2 PPh 2 , 3b, 4b] [1,4-{ Pd [3-( Me -4- MeOC 6 H 2 C(H) = N ]} C 6 H 4 ( LL ) 2 ][ PF 6 ] 2 [LL  Ph 2 PCH(CH 3 ) PPh 2 , Ph 2 P(CH 2 ) n PPh 2 , n = 2, 3 , 3c, 4c, 5c], [1,4-{ Pd [4,5-( OCH 2 O ) C 6 H 2 C(H) = N ]} 2 C 6 H 4 ( LL ) 2 ] [ PF 6 ] 2 [ LL = Ph 2 PCH(CH 3 ) PPh 2 , Ph 2 P(CH 2 ) n PPh 2 , n = 2, 3, 4 , 3d, 4d, 5d, 6d]. The influence of ring size on the phosphorus chemical shift is discussed. The compounds were characterized by microanalysis (C, H, N), IR and 31P-{1H} and 1H NMR spectroscopy. The structure of the dinuclear cyclometallated palladium(II) complex [1,4-{ Pd [2,4-( MeO ) 2 C 6 H 2 C(H) = N ]} 2 C 6 H 4 { Ph 2 P(CH 2 ) 3 PPh 2 −PP} 2 ][ PF 6 ] 2 is described. There are two different crystallographic molecules per asymmetric unit.

Treatment of N,N-isophthalylidenebis(cyclohexylamine), 1,3-(CyNCH)2C6H4 (L2) (Cy = cyclohexyl) with palladium(II) acetate in glacial acetic acid gave after column chromatography the monocyclometallated dimer complex [{ Pd[3-(CHO)C 6 H 3 C(H)N Cy](O 2 CMe)} 2 ] (1) with a free formyl group on each phenyl ring, and a mixture of 1 with the doubly cyclometallated complex [ Pd{3-(CyNCH)C 6 H 3 C(H)N Cy}(O 2 CMe) ] (2). Treatment of 1 with cyclohecylamine gave the corresponding dimer complex [{ Pd[3-(CyNCH)C 6 H 3 C(H)N Cy]O 2 CMe)} 2 ] (17 with an uncoordinated CN group on each phenyl ring. Treatment of 1 and 2 with aqueous NaX gave the dimer complexes [{ Pd[3-(CHO)C 6 H 3 C(H)N Cy](X)} 2 ] (3: X = Cl; 4 X = Br; 5: X = I) and a mixture of 3, 4 or 5 with the doubly cyclometallated complex [{ Pd[3-(CyNCH)C 6 H 3 C(H)N Cy}(X) ] (6: X = Cl; 7: X = Br; 8: X = I), respectively. The dicyclometallated iodo complex 8 was isolated pure. Treatment of 3, 4 or 5 with cyclohexylamine in a 1 : 2 or 1 : 4 molar ratio gave the cyclometallated complexes [ { Pd[3-(CHO)C 6 H 3 C(H)N Cy}(X)(NH 2 Cy) ] (9: X = Cl; 10: X = Br; 11: X = I) and [{ Pd[3-(CyNCH)C 6 H 3 C(H)N Cy}(X)(NH 2 Cy) ] (12: X = Cl; 13: X = Br; 14: X = I), respectively; the last three compounds each contain an uncoordinated C  N group. The corresponding bromo and iodo analogues were made similarly. Treatment of 3, 4 or 5 with thallium cyclopentadienyl or thallium acetylacetonate gave the mononuclear complexes [{ Pd[3-(CHO)C 6 H 3 C(H)N Cy}(C 5 H 5 ) ] (15) and [{ Pd[3-(CHO)C 6 H 3 C(H)N Cy}(H 3 CCOCHCOCH 3 ) ] (16), respectively. Treatment of L2 with MnMe(CO)5 in a 1 : 1 molar ratio gave the monocyclometallated complex [ (OC) 4 Mn{3-(CHO)C 6 H 3 C(H)N Cy} ] (18) by cleavage of one CN bond, whereas treatment of L2 with MnMe(CO)5 in a 1 : 1.2 molar ratio produced a mixture of the doubly cyclometallated complex 19 and the monocyclometallated complex 20 without cleavage of the C  N bond. Treatment of N,N-terephthalylidenebis(cyclohexylamine), 1,4-(CyNCH)2C6H4 (L1) (Cy = cyclohexyl), with MnMe(CO)5 in a 1 : 1.2 molar ratio gave a mixture of the monocyclometallated compound [ (OC) 4 Mn{4-(CHO)C 6 H 3 C(H)N Cy} ] (22) and the monocyclometallated compound [ (OC) 4 Mn{4-(CyNCH)C 6 H 3 C(H)N Cy} ] (23); compound 22 was isolated in a pure state.

The reaction of the halide-bridged dimer complex [{ Pd{2,3,4-(MeO) 3 C 6 HC(H)N Cy}Cl}2] with Ph2PC(CH2)PPh2 (vdpp) in a dimer/diphosphine 1 : 1 molar ratio gives a yellow solid, from whose dichloromethane solution suitable crystals of [{ Pd[2,3,4- (MeO) 3 C 6 HC(H)N Cy]}2{μ-Ph2PC(CH2)PPh2}Cl2] (1) were grown. The structure of 1 has been determined by X-ray crystallography. In the structure there are two [{ Pd[2,3,4-(MeO) 3 C 6 HC(H)N Cy]}Cl] units linked by a ditertiary diphosphine (vdpp) with each palladium atom showing a square-planar environment. Compound 1 is a non-electrolyte, as compared to a 1 : 1 electrolyte structure found for a similar complex.

Treatment of the Schiff bases 4-MeC 6 H 4 C(H)NCy (a), 3-Me-4-MeOC 6 H 3 C(H)N-2′,4′-6′-Me 3 C 6 H 2 ( b ) or 2,4-Me 2 C 6 H 3 C(H)N-2′,4′,6′-Me 3 C 6 H 2 (c) with palladium(II) acetate gave the cyclometallated complexes 1a , 1b and 1c . These reacted with NaX to give the halide-bridged complexes 2a , 2b and 2c (X = Cl), 3a , 3b and 3c (X = Br) and 4c (X = I). Reaction of the halide-bridged dimers with Ph 2 PCH 2 PPh 2 (dppm), trans - Ph 2 PCHCHPPh 2 ( trans -dppe), cis -Ph 2 PCHCHPPh 2 ( cis -dppe) or Ph 2 P(CH 2 ) 4 PPh 2 (dppb), as appropriate in a dimer/diphosphine 1:1 or 1:2 molar ratio gave the dinuclear phosphine-bridged 4a , 5a , 4b , 5b , 5c – 7c and 8c – 10c and mononuclear 6a , 6b , 11c and 12c complexes, respectively. The structure of the bromo-bridged palladium(II) complex [ Pd{4-Me—C 6 H 3 C(H)N Cy}(Br)] 2 ( 3a ) has been determined by X-ray crystallography. The structure has two asymmetrically bridging bromine atoms and a non-bonding Pd ⋯ Pd distance of 341.8(2) pm.

Treatment of 1,4-{2,3,4-(MeO)3C6H2C(H)=N-}2C6H, (a) or 1,4-{4,5-(OCH2O)C6H 3C(H)=N-}2-C6H4 (b) with palladium(II) acetate gave the cyclometallated acetato-bridged complexes [1,4-{ Pd [2,3,4-(MeO) 3 C 6 HC(H)=N ](O2CMe)}2C6H4]n (1a) and [1,4- Pd[4,5-(OCH 2 O)C 6 H 2 C(H)=N ](O2CMe)}2-C6H4]n (1b). These were converted into the analogous halide-bridged complexes by treatment with NaX (2a, 2b X = Cl; 3a, 3b X = Br). Reaction of a or b with PdCl2 also affords the chloro-bridged complexes 2a and 2b, which reacted with LiBr to give the bromo-bridged complexes 3a and 3b. The structure of 3a is described. This is the first example of a structurally characterized tetranuclear cyclometallated bromo-bridged palladium(II) complex. Crystals are triclinic, space group P 1 , with a 1109.1(4), b 1181.5(4), c 1481.5(5) pm, α 77.33(3), β 80.04(3), γ 82.50(3), U 1.857(1) nm3, Z = 1, R = 0.0558 and RW = 0.0610, for 3871 independent reflections with I > 2.0σ-(I). The structure is a centrosymmetric tetranuclear palladium(II) dimer with symmetrically bridging bromine atoms and non-bonding Pd ⋯ Pd distance of 366.2(5) pm.

The new complexes [{P d(2,3,4-(MeO) 3 C 6 HC(H)N R)} 2(μ—LL)(μ-O2CMe)] (O2CMe) [where LL = Ph 2PCH2PPh2 (dppm), Ph2PC(CH2)PPh2 (vdpp); R = Cy, 2′,4′,6′-(Me)3C6H2] were synthesized as 1 : 1 electrolytes by treating the cyclometallated Schiff base palladium(II) acetato-bridged dimers with the appropriate diphosphine in a 1 : 1 molar ratio. These were converted into the analogous halide-bridged complexes by treatment with NaX. Reaction of the palladium(II) cyclometallated halide-bridged dimers with dppm or vdpp in 1 : 1 and 1: 2 molar ratios gave the dinuclear and mononuclear species, [{P d(2,3,4-(MeO) 3 C 6 HC(H)N R)}2(μ-LL) (μ-X)](X) and [P d{2,3,4-(MeO) 3 C 6 HC(H)N R} (LL-P,P)](PF6), respectively, as 1 : 1 electrolytes. The stereochemistry of the complexes is discussed on the basis of spectroscopic data. The compounds were characterized by microanalysis (C, H, N), IR and 1H and 31 P{1H} NMR spectroscopy.

Reaction of cyclometalated halide-bridged Pd(II) complexes 1-4 with the tertiary triphosphine ligand (Ph2PCH2CH2)2PPh (triphos) yielded complexes [((Ph2PCH2CH2)2PPh-P,P,P)Pd(N(Cy)=(H)C)C6H2(C(H)=N(Cy))Pd((Ph2PCH2CH2)2PPh-P,P,P)][ClO4]2 5, [Pd(C6H4-N=NC6H5)((Ph2PCH2CH2)2PPh-P,P,P)][ClO4] 6, and [Pd(R-C6H3C(H)=NCy)((Ph2PCH2CH2)2PPh-P,P,P)][ClO4] (7; R = 4-CHO, 8; 3-CHO). Spectroscopic and analytic data suggest five-coordination on the palladium atom, which, for complexes 5, 6, and 7, was confirmed by X-ray crystallography. The geometry around palladium may be view as a distorted trigonal bipyramid, with the palladium, nitrogen, and terminal phosphorus atoms in the equatorial plane. Compound 5 is the first doubly cyclometalated palladium(II) compound with two pentacoordinated metal centers. The structure of 6 comprises two discrete cations with slightly different geometries, showing the importance of crystal packing forces in order to determine the coordination arrangement.

The reaction of palladium(II) acctate with N -(3-methoxy)benzylidenecyclohexylamine (Hmbcy) in glacial acetic acid yields the acetato-bridged complex 1 . From this the halide-bridged dimers 2 and 3 are synthesized. Treatment of 2 and 3 with bis(diphenylphosphino)methane (dppm) or 1,1-bis (diphenylphosphino)ethene (vdpp) in a 1:1 molar ratio gives the dinuclear specics 4 , 5 and 8 with the two palladium atoms bridged by a diphosphine and a halogen atom. Conductivity measurements show that they are 1:1 electrolytes. Treatment of 2 and 3 with dppm or vdpp and NaClO 4 or NH 4 PF 6 yields the mononuclear species 6 , 7 and 9 with the diphosphine as a chelating ligand. These complexex are also 1:1 electrolytes. The complexes have been characterized by IR, 31 P{ 1 H} and 1 H NMR spectroscopies. The crystal structure of the novel bipalladium(II) complex 8 has been determined: P 2 1 / n ; a =1166.7(3), b =2314.2(4), c =2603.3(5) pm, β=100.76(4)° and Z =4.