Digna Vázquez-García

New cyclometallated platinum(II) compounds with thiosemicarbazones: crystal and molecular structure of [Pt{4-MeC6H3C(Me)NNC(S)NH2}(PPh3)]

Abstract 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.

A Simple Preparation of Pyridine‐Derived N‐Heterocyclic Carbenes and Their Transformation into Bridging Ligands by Orthometalation

Cat-ionic nickel(II) or palladium(II) complexes that have beenprepared in the laboratories of Raubenheimer, Herrmann, orFrenking by oxidative addition (or oxidative substitution) ofthe C X(X=halogen) bond of N-alkyl (or N-aryl) halopyr-idinium (or haloquinolinium, haloacridinium, etc.) salts toappropriate metal(0) precursors.

Novel structures of cyclometallated complexes of palladium(II) derived from terdentate ligands. Crystal and molecular structure of [Pd{C6H4C(H)NCH2CH2CH2NMe2}(X)] (X=Cl, Br, I)

Abstract Treatment of N-(2-chlorobenzylidene)-N,N-dimethyl-1,3-propanediamine (1) and N-(2-bromo-3,4-(MeO)2-benzylidene)-N,N-dimethyl-1,3-propanediamine (20) with tris(dibenzylideneacetone)dipalladium(0) in toluene gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)NCH2CH2CH2NMe2}(Cl)] (2) and [Pd{3,4-(MeO)2C6H2C(H)NCH2CH2CH2NMe2}(Br)] (21), respectively, via oxidative addition reaction with the ligand as a C,N,N terdentate ligand. Reaction of 2 with sodium bromide or iodide in an acetone–water mixture gave the cyclometallated analogues of 2, [Pd{C6H4C(H)NCH2CH2CH2NMe2}(Br)] (3) and [Pd{C6H4C(H)NCH2CH2CH2NMe2}(I)] (4), by halogen exchange. The X-ray crystal structures of 2, 3 and 4 were determined and discussed. Treatment of 2, 3, 4 and 21 with tertiary monophosphines in acetone gave the mononuclear cyclometallated complexes [Pd{C6H4C(H)NCH2CH2CH2NMe2}(L)(X)] (6: L=PPh3, X=Cl; 7: L=PPh3, X=Br; 8: L=PPh3, X=I; 9: L=PMePh2, X=Cl; 10: L=PMe2Ph, X=Cl) and [Pd{3,4-(MeO)2C6H2C(H)NCH2CH2CH2NMe2}(L)(Br)] (22: L=PPh3; 23: L=PMePh2; 24: L=PMe2Ph). A fluxional behaviour due to an uncoordinated CH2CH2CH2NMe2 could be determined by variable temperature NMR spectroscopy. Treatment of 2, 3 and 4 with silver trifluoromethanesulfonate followed by reaction with triphenylphosphine gave the mononuclear complex [Pd{C6H4C(H)NCH2CH2CH2NMe2}(PPh3)][F3CSO3] (11) where the Pd–NMe2 bond was retained. Reaction of 2, 3 and 4 with ditertiary diphosphines in a cyclometallated complex–diphosphine 2:1 molar ratio gave the binuclear complexes [{Pd[C6H4C(H)NCH2CH2CH2NMe2](X)}2(μ-L–L)][L–L=PPh2(CH2)4PPh2(dppb) (13, X=Cl; 14, X=Br; 15, X=I; L–L=PPh2(CH2)5PPh2(dpppe): 16, X=Cl; 17, X=Br; 18, X=I) with palladium–NMe2 bond cleavage. Treatment of 2, 3 and 4 with ditertiary diphosphines, in a cyclometallated complex–diphosphine 2:1, molar ratio and AgSO3CF3 gave the binuclear cyclometallated complexes [{Pd[C6H4C(H)NCH2CH2CH2NMe2]}2(μ-L–L)][F3CSO3]2 (11: L–L=PPh2(CH2)4PPh2(dppb), X=Cl; 12: L–L=PPh2(CH2)5PPh2 (dpppe), X=Cl). Reaction of 2 with the ditertiary diphosphine cis-dppe in a cyclometallated complex–diphosphine 1:1 molar ratio followed by treatment with sodium perchlorate gave the mononuclear cyclometallated complex [Pd{C6H4C(H)NCH2CH2CH2NMe2}(cis-PPh2CHCHPPh2–P,P)][ClO4] (19).

Cyclopalladated compounds derived from a [C,N,S] terdentate ligand: synthesis, characterization and reactivity. Crystal and molecular structures of [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)] and [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{μ-Ph2P(CH2)4PPh2}][CF3SO3]2

Treatment of the Schiff base 2-ClC6H4C(H)NCH2CH2SMe, 1, with palladium(II) acetate in dry toluene gave the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}(O2CMe)], 2. Reaction of 2 with aqueous sodium chloride gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)], 3, after a metathesis reaction. The X-ray crystal structure of 3 was determined and shows that the palladium atom is bonded to four different donor atoms: C, N, S and Cl. Treatment of 3 with triphenylphosphine in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}(Cl)(PPh3)] with cleavage of the Pd–S bond. However, treatment of 3 with silver triflate and triphenylphosphine gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}(PPh3)][CF3SO3], 10, in which the Pd–S bond is retained. Reaction of 3 with the diphosphines dppm, dppb or dppf in a 2 : 1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC6H3C(H)NCH2CH2SMe](Cl)}2{μ-Ph2P(CH2)nPPh2}], (n=1, 5; n=4, 6), and [{Pd[2-ClC6H3C(H)NCH2CH2SMe](Cl)}2(μ-Ph2PC5H4FeC5H4PPh2)], 7. Treatment of 3 with dppb in a 2 : 1 molar ratio and AgCF3SO3 gave the dinuclear cyclometallated complex [{Pd[2-ClC6H3C(H)NCH2CH2SMe]}2{μ-Ph2P(CH2)4PPh2}][CF3SO3]2, 11, which was characterized by X-ray crystal structure analysis. Reaction of 3 with dppe in a 1 : 1 molar ratio and sodium perchlorate gave the mononuclear complex [Pd{2-ClC6H3C(H)NCH2CH2SMe}{Ph2P(CH2)2PPh2-P,P}][ClO4], 8. Treatment of 3 with bis(2-diphenylphosphinoethyl)phenylphosphine in a 1 : 1 molar ratio, followed by treatment with sodium perchlorate gave [Pd{2-ClC6H3C(H)NCH2CH2SMe}{(Ph2PCH2CH2)2PPh-P,P,P}][ClO4], 9, in which the triphosphine is bonded to the palladium atom through the three phosphorus atoms.

Synthesis and reactivity of novel cyclometallated complexes derived from [C,N,O] terdentate ligands. Crystal structure of [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}(PPh3)]

Treatment of the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)N[2-(OH)C6H4], a, and 2,3,4-(MeO)3C6H2C(H)N[2-(OH)-4-MeC6H4], b, with palladium(II) acetate in toluene gave the cyclometallated complexes [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}]n, 1a, and [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]}]n, 1b, respectively, as air stable solids, with the [C,N,O] ligand terdentate after deprotonation of the –OH group. Reaction of the cyclometallated complexes with triphenylphosphine gave the mononuclear species [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]}(PPh3)], 2a, and [Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]}(PPh3)], 2b, with cleavage of the polynuclear structure. The molecular structure of 2a has been determined by X-ray crystallography. Treatment of 1a and 1b with the diphosphines dppm, dppp, dppb, dpppe and dppf in a 1∶2 molar ratio afforded the dinuclear cyclometallated complexes [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]})2{μ-PPh2(CH2)nPPh2}] (3a: n = 1; 4a: n = 3; 5a: n = 4; 6a: n = 5), [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)C6H4]})2(μ-PPh2C5H4FeC5H4PPh2)], 7a, [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]})2{μ-PPh2(CH2)nPPh2}] (3b: n = 3; 4b: n = 4) and [(Pd{2,3,4-(MeO)3C6HC(H)N[2-(O)-4-MeC6H4]})2(μ-PPh2C5H4FeC5H4PPh2)], 5b, as air stable solids. Treatment of 1a and 1b with an excess of mono- or diphosphine did not produce cleavage of the Pd–Ochelating bond.

The First Crystal and Molecular Structure of asyn-Acetato-Bridged Dinuclear Cyclometallated Complex [Pd{2,3,4-(MeO)3C6HC(H)=NCH2CH2OH}(μ-OAc)]2

Treatment of the Schiff base ligands 2,3,4-(MeO)3C6H2C(H)=NR (R = CH2CH2OH, 1; R = Me, 17; R = Et, 18; R = Pr, 19; R = tBu, 20) with palladium(II) acetate in toluene gave the dinuclear cyclometallated complexes [Pd{2,3,4-(MeO)3C6HC(H)=NR}(μ-O2CMe)]2 (R = CH2CH2OH, 2; R = Me, 21; R = Et, 22; R = Pr, 23; R = tBu, 24), with the ligand bonded to the palladium atom through the imine nitrogen and the C6 carbon atoms. The 1H and 13C{1H} NMR spectra of the complexes showed the presence of the anti and syn isomers in solution. The anti/syn ratio varies with the solvent and the nature of the imine nitrogen substituent R. Complex 24 with the bulky tBu group showed a 28:1 ratio in chloroform whilst the less bulky substituted complexes showed lower ratios. The X-ray crystal structure of the syn isomer of complex 2 is described. Reaction of the acetato-bridged complex 2 with PPh3 gave the mononuclear complex 4, in a bridge-splitting reaction. Reaction of 2 with the diphosphanes dppm, dppp and dppb in a 1:1 molar ratio gave the dinuclear cyclometallated complexes 5, 6 and 7, respectively. Treatment of 2 with an aqueous solution of sodium chloride gave the chloro-bridged complex 3. Treatment of the cyclometallated chloro-bridged complex 3 with PPh3 in acetone yielded the mononuclear complex 8, and reaction of 3 with silver triflate gave the cyclometallated complex 9, with the palladium atom bonded to four different atoms C, N, O and P. Treatment of 3 with the tertiary diphosphanes dppp, dppb and dppf, in a 1:1 molar ratio gave the dinuclear complexes 10, 11 and 12, respectively, with terminal chloride ligands. However, reaction of 3 with the small “bite” diphosphane dppm gave 13, with a bridging chloride ligand. Reaction of 11 with silver triflate in acetone gave the new dinuclear complex 14, with the Schiff base ligand as [C,N,O] terdentate. Reaction of 3 with the diphosphane dppe in a 1:2 molar ratio, and silver perchlorate, gave the mononuclear complex 15. Treatment of 3 with the triphosphane bis(2-diphenylphosphanylethyl)phenylphosphane in a 1:2 molar ratio, followed by treatment with sodium perchlorate, gave 16, in which the palladium atom was bonded to the triphosphane through the three phosphorus atoms. The X-ray crystal structures of complexes 8, 9, 15 and 16 are also reported. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Reactivity of cyclometallated palladium(II) compounds derived from N-(benzylidene)xylylendiamines

Abstract The reaction of [1,3-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](μ-O 2 CMe)} 2 C 6 H 4 ] ( 1 ), with triphenylphosphine in a 1:2 molar ratio gave the doubly cyclometallated complex [1,3-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](OAc)(PPh 3 )} 2 C 6 H 4 ] ( 3 ), after cleavage of the two acetate-bridges. Treatment of the chloro-bridged complexes [1,3-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](μ-Cl)} 2 C 6 H 4 ] 2 ( 2 ) and [1,4-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](μ-Cl)} 2 C 6 H 4 ] 2 ( 8 ) with the tertiary monophosphines PPh 3 , P( p -MeOC 6 H 4 ) 3 and P( p -NMe 2 C 6 H 4 )Ph 2 gave the doubly cyclometallated complexes [1,3-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](Cl)(PR 3 )} 2 C 6 H 4 ] (PR 3 =PPh 3 , 4 ; P( p -MeOC 6 H 4 ) 3 , 5 ; P( p -NMe 2 C 6 H 4 )Ph 2 , 6 ) and [1,4-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](Cl)(PR 3 )} 2 C 6 H 4 ] (PR 3 =PPh 3 , 9 ; P( p -MeOC 6 H 4 ) 3 , 10 ; P( p -NMe 2 C 6 H 4 )Ph 2 , 11 ). Reaction of complex 4 with PPh 3 did not yield the expected non-cyclometallated complex. Reaction of complexes 2 and 8 with the tertiary diphosphine cis -Ph 2 PCHCHPPh 2 , in a 1:4 molar ratio and NaClO 4 , yielded the doubly cyclometallated complexes [1,3-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](Ph 2 PCHCHPPh 2 - P , P )} 2 C 6 H 4 ][ClO 4 ] 2 ( 7 ) and [1,4-{Pd[2,3,4-(MeO) 3 C 6 HC(H)NCH 2 ](Ph 2 PCHCHPPh 2 - P , P )} 2 C 6 H 4 ][ClO 4 ] 2 ( 12 ), respectively, with the diphosphine as a chelating bidentate ligand.

Cyclopalladated compounds with a bidentate [C, N]/terdentate [C, N, S] benzylidenethiophene imine ligand. Crystal and molecular structures of [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(μ-OAc)]2, [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(Cl)·(PPh3)] and [{Pd[2,3-(MeO)2C6H2C(H)NCH2(C4H3S)](Cl)}2(μ-Ph2P(CH2)4PPh2)]

Abstract Reaction of the Schiff base ligand 2,3-(MeO)2C6H3C(H)NCH2(C4H3S) (1), with palladium(II) acetate in toluene gave the dinuclear cyclometallated complex [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(μ-OAc)]2 (2), with the ligand bonded to the palladium atom through the imine nitrogen and the C6 carbon atom. The X-ray crystal structure of complex 2 is described. The reaction of 2 with aqueous sodium chloride gave the chloro-bridged complex [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(μ-Cl)]2 (3), after a metathesis reaction. Reaction of 3 with PPh3 in acetone gave the mononuclear cyclometallated complex [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(Cl)(PPh3)] (4), in a bridge-splitting reaction. Treatment of 4 with silver triflate gave the cyclometallated complex [Pd{2,3-(MeO)2C6H2C(H)NCH2(C4H3S)}(PPh3)][CF3SO3] (7), with the palladium atom bonded to four different atoms C, N, S and P. Reaction of 3 with the diphosphines dppp and dppb in a 1:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2,3-(MeO)2C6H2C(H)NCH2(C4H3S)](Cl)}2(μ-Ph2P(CH2)nPPh2)] (5: n=3; 6: n=4), with the diphosphine bridging the two palladium atoms. The X-ray crystal structures of complexes 4 and 6 are reported.

Functionalized cyclopalladated compounds with bidentate Group 15 donor atom ligands: the crystal and molecular structures of [{Pd[5-(COH)C6H3C(H)NCy-C2,N](Cl)}2(μ-Ph2PRPPh2)] (R=CH2CH2, Fe(C5H4)2], [Pd{5-(COH)C6H3C(H)NCy-C2,N}(Ph2PCH2PPh2-P,P)][PF6] and [Pd{5-(COH)C6H3C(H)N(Cy)-C2,N}(Ph2PCH2CH2AsPh2-P,As)][PF6]

The chloro-bridged dinuclear compound [{Pd[5-(COH)C6H3C(H)N(Cy)-C2,N]}(μ-Cl)]2 (1), reacts with tertiary diphosphines in 1:1 molar ratio to give [{Pd[5-(COH)C6H3C(H)NCy-C2,N](Cl)}2(μ-Ph2PRPPh2)] (R: CH2, 2; CH2CH2, 3; (CH2)4, 4; (CH2)6, 5; Fe(C5H4)2, 6; trans-CHCH, 7; C≡C, 8). Treatment of 1 with Ph2PCH2CH2AsPh2 (arphos) gives the dinuclear complex [{Pd[5-(COH)C6H3C(H)N(Cy)-C2,N](Cl)}2(μ-Ph2PCH2CH2AsPh2)] (9). The reaction of 1 with tertiary diphosphines or arphos in 1:2 molar ratio in the presence of NH4PF6 yields the mononuclear compounds [Pd{5-(COH)C6H3C(H)NCy-C2,N}(Ph2PRPPh2-P,P)][PF6] (R: (CH2)4, 10; (CH2)6, 11; Fe(C5H4)2, 12; 1,2-C6H4, 13; cis-CHCH, 14; NH, 15) and [Pd{5-(COH)C6H3C(H)N(Cy)-C2,N}(Ph2PCH2CH2AsPh2-P,As)][PF6] (16). 1H-, 31P-{1H}- and 13C-{1H}-NMR, IR and mass spectroscopic data are given. The crystal structures of compounds 3, 6, 9 and 16 have been determined by X-ray crystallography.

Nucleophilic addition of 1,3-dicarbonyl compounds as a route to functionalized cyclopalladated complexes with chelated 1,1-bis(diphenylphosphino)ethene

Treatment of the chloride-bridged complex [Pd{2,4-(OMe)2C6H2C(H)N(Cy)-C6,N}(μ-Cl)]2 (1) with 1,1-bis(diphenylphosphino)ethene (vdpp) and NH4PF6 or NaClO4 in 1∶2 molar ratio afforded the mononuclear cyclometallated palladium(II) complexes [Pd{2,4-(OMe2)C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CCH2-P,P′}](X) (2, X = PF6; 3, X = ClO4). The structure of 2 has been determined by X-ray diffraction analysis. Reaction of 2 with acetylacetone in the presence of anhydrous sodium carbonate yielded in high yield the addition product [Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CHCH2CH(COMe)2-P,P′}](PF6) (4). The 31P-{1H} NMR spectrum showed a greater 2J(PP) coupling constant than the one observed for the starting complex. Reaction of 2 with diethyl malonate afforded a 7∶3 mixture of the addition product [Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CHCH2CH(COOEt)2-P,P′}](PF6) (5) and the starting complex. The desired addition compound could be isolated in pure form by treatment of 3 with diethyl malonate yielding [Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CHCH2CH(COOEt)2-P,P′}](ClO4) (16). The reaction of 2 with asymmetric nucleophiles such as methyl acetoacetate, ethyl propionylacetate, ethyl acetoacetate, methyl 4-chloroacetoacetate, 1,1,1-trifluoroacetylacetone and thenoyltrifluoroacetone afforded the corresponding addition derivatives, [Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(PH2P)2CHCH2CH(COR1)(COR2)-P,P′}](PF6) (R1 = Me, R2 = OMe, 6; R1 = Et, R2 = OEt, 7; R1 = Me, R2 = OEt, 8; R1 = CH2Cl, R2 = OMe, 9; R1 = Me, R2 = CF3, 10; R1 = CF3, R2 = 2-SC4H3, 11). The NMR spectra showed some resonances were duplicated, suggesting the existence of optical isomers, as a consequence of the existence of two chiral carbon atoms in the diphosphine moiety, (Ph2P)2C*HCH2C*H(COR1)(COR2). The molecular structure of compound 7 has been determined by X-ray crystallography confirming the spectroscopic data. The crystal structure of 7 comprises equimolar amounts of the (C16R, C18S) and (C16S, C18R) enantiomers. Reaction of 2 with 1-(2-furyl)-1,3-butanedione, ethyl 2-methylacetoacetate, 3-chloroacetylacetone and methyl 2-chloroacetoacetate gave compounds [Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CHCH2C(R1)(COMe)(COR2)-P,P′}](PF6) (R1 = H, R2 = 2-OC4H3, 12; R1 = Me, R2 = OEt, 13; R1 = Cl, R2 = Me, 14; R1 = Cl, R2 = OMe, 15). The 2J(PP) coupling constants for 14 and 15 were smaller than in the other addition compounds due to the presence of the neighbouring chlorine atom. Treatment of 2 with 3-ethylacetylacetone or 2,2,6,6-tetramethyl-3,5-heptanedione did not give any addition product. However, reaction of 3 with 3-ethylacetylacetone yielded a mixture of 3/[Pd{2,4-(MeO)2C6H2C(H)N(Cy)-C6,N}{(Ph2P)2CHCH2C(Et)(COMe)2-P,P′}](ClO4) (17) in 1∶1 molar ratio.