The cyclometallation of bis(di-p-methylbenzylphosphino)methane

The new diphosphine (4-MeC₆H₄CH₂)₂PCH₂P(4-MeC₆H₄CH₂)₂, L, was reacted with [MnMe(CO)₅] to give the novel cyclometallated compound [Mn{(4-MeC₆H₃CH₂)(4-MeC₆H₄CH₂)PCH₂P(4-MeC₆H₄CH₂)₂}(CO)₃], as the mer isomer, and with the ligand in a terdentate [C,P,P] fashion.     

Novel Cyclometallated Complexes Derived From a Halogenated Thiosemicarbazone. Crystal and Molecular Structures of 2‐FC6H4C(Me)=NN(H)C(=S)NHPh and [(Pd{2‐FC6H3C(Me)=NN=C(S)NHPh})2(μ‐PPh2(CH2)2PPh2)]

Treatment of the thiosemicarbazone 2‐FC₆H₄C(Me)=NN(H)C(=S)NHPh, a , with palladium(II) acetate in acetic acid, or with lithium tetrachloropalladate(II) in methanol, gave the tetranuclear cyclometallated complex [Pd{2‐FC₆H₃C(Me)=NN=C(S)NHPh}]₄ (1a) . Reaction of 1a with the diphosphines Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂PCH=CHPPh₂ (trans‐dpe) Ph₂P(CH₂)₃Ph₂ (dppp) or Ph₂P(CH₂)₄Ph₂ (dppb) in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{2‐FC₆H₃C(Me)=NN=C(S)NHPh})₂(μ‐Ph₂P(CH₂)_nPPh₂)], (n = 2, 2a ; 3, 4a ; 4, 5a ) and [(Pd{2‐FC₆H₃C(Me)=NN=C(S)NHPh})₂(μ‐Ph₂PCH=CHPPh₂)], ( 3a ). The X‐ray crystal structure of ligand a and of complex 2a are described. The structure of complex 2a shows the palladium atom is bonded to four different donor atoms: C, N, S and P.     

[Pd{2-CH2-5-MeC6H3C(H)NNC(S)NHEt}]3: An unprecedented trinuclear cyclometallated palladium(II) cluster through induced flexibility in the metallated ring

The reaction of 1-(2,5-dimethylbenzylidene)-3-ethylthiosemicarbazone and palladium acetate in acetic acid yields a trinuclear cyclometallated palladium(II) compound. Each thiosemicarbazone ligand is tridentate with the metal bonded to the carbon atom from the 2-methyl group, to the azomethine nitrogen and to the sulfur atom, which bridges to an adjacent palladium center. The crystal structure confirms the presence of a non-planar hexagonal metallated ring plus a central six-membered palladium-sulfur core within the trimer, which also displays a rather deep intramolecular cavity.     

Synthesis and characterization of new heterocyclic Schiff base palladacycles: Ring activation through N-oxide formation

Reaction of the Schiff base ligand derived from 4-pyridinecarboxaldehyde NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂], (1), with palladium(II) acetate in toluene at 60 °C for 24 h gave [Pd{NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂]}₂(OCOCH₃)₂], (2), with two ligands coordinated through the pyridine nitrogen. Treatment of the Schiff base ligand derived from 4-pyridinecarboxaldehyde N-oxide, 4-(O)NC₅H₄C(H)N[2′,4′,6′-(CH₃)C₆H₂], (4), with palladium(II) acetate in toluene at 75 °C gave the dinuclear acetato-bridged complex [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(OCOCH₃)]₂, (5) with metallation of an aromatic phenyl carbon. Reaction of complex 5 with sodium chloride or lithium bromide gave the dinuclear halogen-bridged complexes [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Cl)]₂, (6) and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Br)]₂, (7), after the metathesis reaction. Reaction of 6 and 7 with triphenylphosphine gave the mononuclear species [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(Cl)(PPh₃)], (8) and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}-(Br)(PPh₃)], (9), as air stable solids. Treatment of 6 and 7 with Ph₂P(CH₂)₂PPh₂ (dppe) in a complex/diphosphine 1:2 molar ratio gave the mononuclear complexes [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(PPh₂(CH₂)₂PPh₂)][Cl], (10), and [Pd{4-(O)NC₅H₃C(H)N[2′,4′,6′-(CH₃)C₆H₂]}(PPh₂(CH₂)₂PPh₂)][PF₆], (11), with a chelating diphosphine. The molecular structure of complex 9 was determined by X-ray single crystal diffraction analysis.     

Reactivity of 6-(2-tolyl)- and 6-(2,6-xylyl)-2,2′-bipyridines with palladium(II) derivatives. Selective C(sp)H vs. C(sp)H activation

Two new 6-substituted 2,2′-bipyridines, L, 6-(2-tolyl)bipy, L¹, and 6-(2,6-xylyl)bipy, L², have been synthesized. Their reactions with Na₂[PdCl₄] or {Pd(OAc)₂} afford either 1:1 adducts [Pd(L)X₂] (X=Cl, OAc) or five-membered cyclometallated derivatives [Pd(L¹-H)X] arising from C(sp²)H activation. From the chloro-alkyl intermediates [Pd(L)(Me)Cl], in the presence of Na[BAr′₄] (Ar′=3,5-(CF₃)₂C₆H₃), cationic species [Pd(L)(Me)(S)]⁺ (L=L¹, L²; S=CH₃CN) can be obtained. At variance, in less coordinating solvents, e.g. dichloromethane, unexpected activation of a C(sp³)H bond occurs with loss of methane, to afford 6-membered cyclometallated derivatives. The latter species were isolated as [Pd(L-H)(PPh₃)][BAr′₄].     

Reactivity of C(sp)-Pd and C(sp)-Pd bonded palladacycles with diphosphines. Crystal and molecular structure of the novel A-frame complex [{Pd[2,5-Me2C6H2C(H)N(2,4,6-Me3C6H2)-C6]}2(μ-Ph2PCH2PPh2)2(μ-Cl)][PF6]

Treatment of the halogen-bridged complexes [Pd{2,5-Me₂C₆H₂C(H)N(2,4,6-Me₃C₆H₂)-C6,N}(μ-X)]₂ (1a, X = Cl; 2a, X = Br) with the tertiary diphosphine Ph₂PCH₂PPh₂ (dppm), regardless of the molar ratio used, gave a mixture of two complexes: [Pd{2,5-Me₂C₆H₂C(H)N(2,4,6-Me₃C₆H₂)-C6}(μ-Ph₂PCH₂PPh₂)₂(μ-X)]₂[PF₆] (5a, X = Cl; 6a, X = Br), which presents an A-frame structure, and [Pd{2,5-Me₂C₆H₂C(H)N(2,4,6-Me₃C₆H₂)-C6,N}(Ph₂PCH₂PPh₂-P,P)][PF₆], 3a, with the diphosphine as chelating. The mixture could be separated and the corresponding complexes isolated. However, reaction of 1a and 2a with the diphosphine Ph₂PC(CH₂)PPh₂ (vdpp) exclusively gave the mononuclear complex [Pd{2,5-Me₂C₆H₂C(H)N(2,4,6-Me₃C₆H₂)-C6,N}{Ph₂PC(CH₂)PPh₂-P,P}][PF₆], 4a, analogous to 3a. Treatment of the halogen-bridged complexes [Pd{1-CH₂-2-[HCN(2,4,6-Me₃C₆H₂)]-4-MeC₆H₃-C,N}(μ-X)]₂ (1a′, X = Cl; 2a′, X = Br) with dppm or vdpp in a cyclometallated complex/diphosphine 1:2 M ratio, gave mononuclear complexes with the chelating diphospines [Pd{1-CH₂-2-[HCN(2,4,6-Me₃C₆H₂)]-4-MeC₆H₃-C,N}(Ph₂PCH₂PPh₂-P,P)][PF₆], 3a′, and [Pd{1-CH₂-2-[HCN(2,4,6-Me₃C₆H₂)]-4-MeC₆H₃-C,N}{Ph₂PC(CH₂)PPh₂-P,P}][PF₆], 4a′. When the reaction was carried out using a cyclometallated complex/diphosphine 1:1 M ratio the dinuclear complexes [{Pd[1-CH₂-2-{HCN(2,4,6-Me₃C₆H₂)}-4-MeC₆H₃-C,N]}₂(μ-X)(μ-Ph₂PCH₂PPh₂)][Cl], (5a′, X = Cl; 7a′, X = Br) and [{Pd[1-CH₂-2-{HCN(2,4,6-Me₃C₆H₂)}-4-MeC₆H₃-C,N]}₂(μ-Cl){μ-Ph₂PC(CH₂)PPh₂}][Cl], 6a′, were obtained. The molecular structures of complexes 3a, 4a, 5a and 6a′ were determined by X-ray single crystal diffraction.     

Cyclometallation of phenylhydrazones: Synthesis, reactivity, crystal structure analysis and novel trinuclear palladium(II) cyclometallated compounds with [C, N, N′] terdentate ligands

Reaction of the ligand C₆H₅N(H)NCMe(C₅H₄N) (a) with palladium(II) acetate in toluene gave the mononuclear cyclometallated complex [Pd{C₆H₄N(H)NCMe(C₅H₄N)}(AcO)] (1a). Reaction of 1a with sodium chloride gave the analogous chlorine compound [Pd{C₆H₄N(H)NCMe(C₅H₄N)}(Cl)] (3a) which could also be prepared by reaction of a with lithium tetrachloropalladate and sodium acetate in methanol for 48 h; whereas shorter reaction times afforded the non-cyclometallated complex [Pd{C₆H₅N(H)NCMe(C₅H₄N)}(Cl)₂] (2a). Reaction of the ligand 2-ClC₆H₄N(H)NCMe(C₅H₄N) · HCl (b), with palladium(II) acetate, or with lithium tetrachloropalladate and sodium acetate, yielded the cyclometallated complex [Pd2-ClC₆H₃N(H)NCMe(C₅H₄N)(Cl)] (1b). Treatment of 3a and 1b with silver trifluoromethanesulphonate (triflate) and triphenylphosphine in acetone gave the mononuclear complexes [Pd{2-RC₆H_nN(H)NCMe(C₅H₄N)}(PPh₃)][CF₃SO₃], (R = H, n = 4, 4a; R = Cl, n = 3, 2b) with the ligand as C,N,N′ terdentate and substitution of chlorine by triphenylphosphine. Reaction of 3a and 1b with silver triflate and the tertiary diphosphine Ph₂P(CH₂)₄PPh₂ (dppb) in a 2:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-RC₆H₃N(H)NCMe(C₅H₄N)]}₂(μ-Ph₂P(CH₂)₄PPh₂)][CF₃SO₃]₂ (R = H, 5a; R = Cl, 3b) with a μ₂-diphosphine bridging ligand. Similarly, treatment of 3a and 1b with silver triflate and the tertiary triphosphines MeC(CH₂PPh₂)₃ (tripod) and (Ph₂PCH₂CH₂)₂PPh (triphos), in 3:1 molar ratio, gave the novel trinuclear complexes [{Pd[C₆H₄N(H)NCMe(C₅H₄N)]}₃{μ₃-MeC(CH₂Ph₂)₃}][CF₃SO₃]₃ (6a) and [{Pd[2-ClC₆H₃N(H)NCMe(C₅H₄N)]}₃{μ₃-(PPh₂CH₂CH₂)₂PPh}][CF₃SO₃] ₃ (4b) regioselectively, with the phosphine as a μ₃-bridging ligand. When the reaction between 3a and triphos was carried out in 1:1 molar ratio the mononuclear complex [Pd{C₆H₄N(H)NCMe(C₅H₄N)}{(PPh₂CH₂CH₂)₂PPh-P,P,P}][ClO₄] (7a) was obtained. The crystal structures of 2b, 3a and 4a have been determined by X-ray crystallography.     

Pd-catalyzed intramolecular Heck reaction for the synthesis of 2-methylbenzofurans

A new strategy for the synthesis of 2-Methylbenzofurans via the intramolecular Heck reaction has been developed. This efficient palladium-catalyzed system showed good catalytic activity. Various substituted 2-methylbenzofurans could be afforded in good to excellent yields.     

Cyclopalladated acetate dimers: Crystal structures and VT-NMR

The X-ray structure of two cyclopalladated acetate bridged dimers has been solved, and they are shown to exhibit an open-book type core, analogous to those that have been previously reported. Variable temperature NMR studies on these molecules demonstrates that this core persists in chloroform solution, resulting in restrictions to the movement of ancillary parts of the molecule. The barrier to rotation of a pendant phenyl ring against this core has been measured: ΔH^‡ = 56 kJ mol⁻¹, and ΔS^‡ = 0.     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.     

The cyclopalladation of benzylidenebenzylamines

A number of isomeric N-benzylbenzalimine palladium(II) complexes of the type [P ·CH₂Ph]₂ (with C=N endo to the palladocycle) and [P =C(CH₃Ph]₂ (with C=N exo to the palladocycle), have been prepared and charcterised by ¹H and ¹³C NMR methods. The crystal structures of two analogous monomeric acac complexes, synthesized independently by oxidative addition of o-BrC₆H₄CH₂N=CH · Ph to Ph to Pd(dibenzylideneacetone)₂ have also been determined. These are [P · CH₂Ph)] (15a) and [P =CHPh)] (20a). Crystals of 15a are monoclinic, space group P2₁/a with Z = 4 in a cell of dimensions a 10.286(2), b 11.902(3), c 13.895(5) Å, β 93.52(2)° while 20a is monoclinic, space group P2₁/c with Z = 8 and a 10.353(3), b 20.600(5), c 16.545(7) Å, β 92.14(3)°. The structures 15a and 20a were refined to residuals R = 0.041 and 0.055 for 1661 and 2525 observed reflections respectively.     

Substituent effects on the cyclo-manganation reaction X-ray crystal structure of Mn{2-(Bu-N=CH) 5-(NO2) C6H3}(CO)4

The cyclometallation reaction between methylmanganese pentacarbonyl and a number of Schiff's bases has been studied. The dependence of the rate of reaction upon ligand substituents has been investigated, demonstrating a rate enhancement with more electron-rich ligands.

The X-ray structure of Mn2-(ⁿBu-N=CH)5-(NO₂)C₆H₃(CO)₄ has been determined.     

Cyclopalladation of thiophene-substituted thiosemicarbazones

The thiosemicarbazones obtained from the condensation of thiosemicarbazide or 4,4′-dimethylthiosemicarbazide with 2-acetylthiophene react with K₂PdCl₄ in the presence of a base to give dark, poorly soluble materials in high yields. Treatment of these oligomeric compounds with Ph₃P, dppe or dppf gives monomeric palladium(II) phosphine complexes in which the deprotonated thiosemicarbazones coordinate to the metal in a tridentate fashion through the C3-cyclometallated thiophene ring, the imine nitrogen atom and the sulphur atom. This coordination mode was confirmed by X-ray structure analysis of several derivatives.     

The optimization for cyclization reaction of 2-(2-carbomethoxyethynyl)aniline derivatives and formal synthesis of pyrroloquinoline quinone and its analogue utilizing a sequential coupling-cyclization reaction

The reaction conditions for the Pd-catalyzed cyclization reaction of 2-(2-carbomethoxyethynyl)aniline derivatives were investigated. The amounts of Pd(PPh₃)₄, methyl propiolate, and ZnBr₂ could be significantly reduced compared with those reported in our preliminary publication by careful tuning of the solvent and the reaction temperature. In addition to the above results, formal syntheses of pyrroloquinoline quinone (PQQ) and its analogue from 2-amino-5-nitrophenol using a Pd-complex-catalyzed sequential coupling-cyclization reaction between methyl propiolate and 2-iodoaniline derivatives are described.     

Are Organotin Reagents Derived from Bis(trimethylsilyl)picoline Suitable Precursors for the Preparation of Cyclometallated Complexes?

The organotin reagents [2‐PyC(SiMe₃)₂SnR₃] (R = Me, ⁿBu) were prepared in good yields from the reaction between the lithium salt of 2‐bis(trimethylsilyl)picoline and the corresponding trialkyltin chlorides. Reactions of these organotin reagents were carried out with various Pd and Pt complexes including [MCl₂(cod)] and [MCl₂(PhCN)₂] (M = Pd, Pt). The results show that a Me group is transferred to the metal atom, rather than the 2‐bis(trimethylsilyl)picolyl group. The mechanism for this reaction is discussed and reasons why Me group transfer occurs based on DFT computed structural data are given.     

Bridge cleavage reactions of cyclopalladated nitrosamines with thioamides and related compounds

The palladacycle [Pd(μ-O₂CMe){κ²C,N-4-MeC₆H₃N(Me)NO}]₂ readily undergoes bridge cleavage reactions with a variety of compounds containing donor functionalities including thioamides, 8-hydroxyquinoline, thioureas, selenoureas, acetylacetone derivatives, dithiocarbamates, xanthates, as well as bidentate N-donors to afford either the monomeric, neutral Pd(II) complexes [Pd{κ²C,N-4-MeC₆H₃N(Me)NO}{L-L}] or the monocationic complexes [Pd{κ²C,N-4-MeC₆H₃N(Me)NO}(N-N)]PF₆ in high yields. A series of 15 different complexes was prepared and fully characterised spectroscopically and, in some cases, by X-ray diffraction. It was also found that the dithiocarbamato complex undergoes a disproportionation reaction in solution to give the bis(cyclometallated) complex [Pd{κ²C,N-4-MeC₆H₃N(Me)NO}₂] as well as the bis(dithiocarbamato) complex [Pd{κ²S-S₂CNEt₂}₂].     

Computational study of the cyclopalladation mechanism of azobenzene with PdCl2 in N,N-dimethylformamide

The mechanism of cyclopalladation of azobenzene (L) with PdCl₂ in N,N-dimethylformamide (dmf) was studied computationally, using DFT (B3LYP) methods supplemented with a continuum solvation model. Since the exact nature of the reacting complex is unknown, several candidates were considered. These were: (1) a mononuclear adduct with two ligand molecules, L-PdCl₂-L, (2) a mononuclear adduct with one ligand and one solvent molecule, L-PdCl₂-dmf, (3) a dinuclear adduct with a double chloride bridge, [L-PdCl-(μ-Cl)]₂, and (4) a coordinatively unsaturated complex with an agostic interaction, L-PdCl₂. The reaction profile initiating from L-PdCl₂-dmf, which displays an agostic intermediate produced after displacement of the dmf molecule by the activating C-H bond, has the lowest barrier (20.4 kcal/mol in the step with the proton transfer to the O(dmf) atom). In all other reaction pathways, the proton migration is to a chlorine atom and is associated with remarkably high barriers. The results are related to previous experimental and other computational findings. While none of the reaction profiles includes explicit dissociation of the ligand, the proton transfer was found to occur only after the ligand is almost completely displaced from the coordinating shell. It was concluded that the transition state corresponds to 14-electron coordination of Pd and that ease of a ligand dissociation is an important, but not necessarily decisive, factor for cyclopalladation.     

Synthesis and characterization of 2-phenylaniline cyclopalladated complexes

Reaction of the dinuclear complex [Pd{κ2-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}Cl]₂ (1) with ligands (L = 4-picoline, sym-collidine) gave the six-membered palladacycles [Pd{κ2-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}Cl(L)] (2). The complex 1 reacted with AgX (X = CF₃SO₃, BF₄) and bidentate ligands [L–L = phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), bipy(2,2′-bipyridine) and dppp (bis(diphenylphosphino)propane)] giving the mononuclear orthopalladated complexes [Pd{κ2-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}(L–L)] (3) [L–L = phen, dppe, bipy and dppp]. These compounds were characterized by physico-chemical methods, and the structure of [Pd{κ2-N2′,C1-2-(2′-NH₂C₆H₄)C₆H₄}Cl(L)] (L = sym-collidine) was determined by single-crystal X-ray analysis.     

Cyclometallated complexes derived from pyrimidin- and pyridazinehydrazones: Structural evidence of intermolecular “chelate metal ring” π-π interactions

Reaction of 3,4-(Me)₂C₆H₃C(Me)NN(H)[3′-(CF₃)C₄H₂N₂] (a) and 3,4-(Me)₂C₆H₃C(Me)NN(H)(4′-ClC₄H₂N₂) (b) with palladium(II) acetate gave the mononuclear cyclometallated complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(OAc)] (1a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(OAc)] (1b) with the ligand as terdentate [C,N,N]. Treatment of a and b with Li₂[PdCl₄] and sodium acetate in methanol at room temperature yielded the mononuclear cyclometallated complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(Cl)] (2a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(Cl)] (2b), respectively. Recrystallization of 2b from a dimethylsulfoxide solution gave [Pd{3,4-(Me)₂C₆H₂C(Me)NN(4′-ClC₄H₂N₂)}][(CH₃)₂SO] after deprotonation of the hydrazine nitrogen. The reaction of 2a and 2b with silver trifluoromethanesulfonate and triphenylphosphine, yielded [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}-(PPh₃)][CF₃SO₃] (3a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}(PPh₃)]-[CF₃SO₃] (3b) with the phosphine ligand occupying the vacant coordination position after chlorine abstraction; these were deprotonated at the hydrazine nitrogen after treatment with sodium acetate. Reaction of 2a with Ph₂P(CH₂)₂AsPh₂ (arphos), after AgCl removal gave mononuclear complex Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}(Ph₂P(CH₂)₂AsPh₂)][ClO₄] (5a) with a non-coordinated As atom. Reaction of 2a and 2b with a Ag(I) salt and the tertiary diphosphine Ph₂P(CH₂)₄PPh₂ (dppb) in 2:1 molar ratio gave the dinuclear complexes [{Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}}₂(μ-Ph₂P(CH₂)₄PPh₂)][CF₃SO₃]₂ (6a) and [{Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}}₂(μ-Ph₂P(CH₂)₄PPh₂)][ClO₄]₂ (6b) with the diphosphine as a bridging ligand. Similarly, treatment of 1b with silver triflate followed by reaction with the tertiary triphosphine (Ph₂PCH₂CH₂)₂PPh (triphos), in a 3:1 molar ratio, gave the new trinuclear complex [{Pd[3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)]}₃{μ₃-(Ph₂PCH₂CH₂)₂PPh}][CF₃SO₃]₃ (8b). However, reaction of 2a and 2b with (triphos), in 1:1 molar ratio gave the mononuclear complexes [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)[3′-(CF₃)C₄H₂N₂]}{(Ph₂PCH₂CH₂)₂PPh-P,P,P}][ClO₄] (7a) and [Pd{3,4-(Me)₂C₆H₂C(Me)NN(H)(4′-ClC₄H₂N₂)}-{(Ph₂PCH₂CH₂)₂PPh-P,P,P}][ClO₄] (7b) with a is five-coordinated palladium. The crystal structures of 2b, 3a, 3b, 7a and 7a have been determined by X-ray crystallography and they show π-π interactions between the metallacycle and the heterocyclic pyrimidine or pyridazine rings, which controls the crystal packing.