Javier Martínez

Synthesis of Cyclic Carbonates Catalysed by Aluminium Heteroscorpionate Complexes.

New aluminium scorpionate based complexes have been prepared and used for the synthesis of cyclic carbonates from epoxides and carbon dioxide. Bimetallic aluminium(heteroscorpionate) complexes 9-14 were synthesised in very high yields. The single-crystal X-ray structures of 12 and 13 confirm an asymmetric κ(2)-NO-μ-O arrangement in a dinuclear molecular disposition. These bimetallic aluminium complexes were investigated as catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide in the presence of ammonium salts. Under the optimal reaction conditions, complex 9 in combination with tetrabutylammonium bromide acts as a very efficient catalyst system for the conversion of both monosubstituted and internal epoxides into the corresponding cyclic carbonates showing broad substrate scope. Complex 9 and tetrabutylammonium bromide is the second most efficient aluminium-based catalyst system for the reaction of internal epoxides with carbon dioxide. A kinetic study has been carried out and showed that the reactions were first order in complex 9 and tetrabutylammonium bromide concentrations. Based on the kinetic study, a catalytic cycle is proposed.

The key role of sulfur in thiosemicarbazone compounds. Crystal and molecular structure of [Pd{4-MeOC6H4C(Me)NNC(S)NHPh}2]

Abstract The reaction of thiosemicarbazones 4-MeOC 6 H 4 C(H)ue605NN(H)C(ue605S)NHMe ( a ), 4-MeOC 6 H 4 C(H)ue605NN(H)C(ue605S)NHEt ( b ) and 4-MeOC 6 H 4 C(H)ue605NN(H)C(ue605S)NHPh ( c ), with Li 2 [PdCl 4 ], K 2 [PdCl 4 ] or Pd(AcO) 2 leads to the tetranuclear palladium(II) compounds, [Pd{4-MeOC 6 H 3 C(H)ue605NNue605C(S)NHMe}] 4 ( 1a ), [Pd{4-MeOC 6 H 3 C(H)ue605NNue605C(S)NHEt}] 4 ( 1b ) and [Pd{4-MeOC 6 H 3 C(H)ue605NNue605C(S)NHPh}] 4 ( 1c ); the ligands are terdentate through the [C, N, S] atoms and they are deprotonated at the –NH– group. Reaction of thiosemicarbazones 3-MeOC 6 H 4 C(H)ue605NN(H)C(ue605S)NHMe ( d ) and 3-MeOC 6 H 4 C(H)ue605NN(H)C(ue605S)NHEt ( e ), with Li 2 [PdCl 4 ] or K 2 [PdCl 4 ] gave the mononuclear palladium(II) compounds [Pd{3-MeOC 6 H 4 C(H)ue605NNue605C(S)NHMe} 2 ] ( 1d ) and [Pd{3-MeOC 6 H 4 C(H)ue605NNue605C(S)NHEt} 2 ] ( 1e ); the ligands are bonded only through the azomethine nitrogen and sulfur atoms. Treatment of thiosemicarbazone 4-MeOC 6 H 4 C(Me)ue605NN(H)ue605C(S)NHPh ( f ) with Li 2 [PdCl 4 ] gave the tetranuclear compound [Pd{4-MeOC 6 H 3 C(Me)ue605NNue605C(S)NHPh}] 4 ( 1f ), which upon treatment with bis(diphenylphosphino)methane, dppm in 1:2 molar ratio gave the dinuclear species [{Pd[4-MeOC 6 H 3 C(Me)ue605NNue605C(S)NHPh]} 2 (μ-Ph 2 PCH 2 PPh 2 )] ( 2f ). The recrystallization of 2f gave the chiral compound [Pd{4-MeOC 6 H 4 C(Me)ue605NNue605C(S)NHPh} 2 ] ( 3f ). The molecular structure has been determined by single-crystal diffraction, showing O⋯H and S⋯H hydrogen bonding.

One-Component Aluminum(heteroscorpionate) Catalysts for the Formation of Cyclic Carbonates from Epoxides and Carbon Dioxide

New neutral and zwitterionic chiral NNO-donor scorpionate ligands 1 and 2 were designed to obtain new mononuclear and dinuclear NNO-heteroscorpionate aluminum complexes. Reaction of 1 with [AlR3 ] (R=Me, Et) in a 1:1 or 1:2 molar ratio afforded the neutral mononuclear alkyl complexes [AlR2 (κ2 -bpzappe)] {R=Me (3), Et (4); bpzappeH=2,2-bis(3,5-dimethylpyrazol-1-yl)-1-[4-(dimethylamino)phenyl]-1-phenylethanol} and bimetallic complexes [{AlR2 (κ2 -bpzappe)}(μ-O){AlR3 }] [R=Me (5), Et (6)]. By reaction of complexes 3-6 with PhCH2 Br, mononuclear and dinuclear cationic aluminum complexes [AlR2 (κ2 -bbpzappe)]Br {R=Me (7), Et (8); bbpzappeH=N-benzyl-4-[2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1-hydroxy-1-phenylethyl]-N,N-dimethylbenzenaminium bromide} and [{AlR2 (κ2 -bbpzappe)}(μ-O){AlR3 }]Br [R=Me (9), Et (10)] were synthesized. Both neutral aluminum complexes in the presence of Bu4 NBr and cationic aluminum complexes were investigated as catalysts for cyclic carbonate formation from epoxides and carbon dioxide. Amongst them, complexu200510 was found to be an efficient one-component catalyst for the synthesis of cyclic carbonates from both monosubstituted and internal epoxides and was shown to have broad substrate scope.

Novel cyclopalladated ferrocenyl Schiff base compounds with bridging and chelating diphosphines. Crystal and molecular structure of [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)N-2,4,6-Me3C6H2]}{Ph2P(CH2)nPPh2P,P}][PF6] (n=1, 2)

Abstract The reaction of the ferrocenylimine (η5-C5H5)Fe(η5-C5H4)C(H)ue605NR (R=2,4,6-Me3C6H2) (a), with Pd(AcO)2 or with Li2[PdCl4] leads to the heterotetrametallic compounds [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR}(μ-O2CMe)]2 (1) and [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR}(μ-Cl)]2 (2), respectively. Compound 2 may also be obtained by treatment of 1 with aqueous sodium chloride. Compound 2 reacts with tertiary diphosphines in 1:1 or 1:2 molar ratio to give [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR]Cl}2{μ-Ph2P(CH2)nPPh2}] (n=1, 3; n=2, 4; n=3, 5; n=4, 6), [{Pd[(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR]Cl}2(μ-Ph2PC5H4FeC5H4PPh2)] (7), and [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR}{Ph2P(CH2)nPPh2ue5f8P,P}][PF6] (n=1, 8; n=2, 9; n=3, 10; n=4, 11), [Pd{(η5-C5H5)Fe(η5-C5H3)C(H)ue605NR}(Ph2PC5H4FeC5H4PPh2ue5f8P,P)][PF6] (12), respectively. The crystal structures of compounds 8 and 9 have been determined by X-ray crystallography.

New palladium(II) cyclometallated compounds derived from trans-cinnamalylideneimines via CH activation of an sp2-aliphatic carbon atom

Abstract Treatment of the Schiff-base ligands C 6 H 5 C(H)ue605C(R)C(H)ue605NCy (R=H, a ; R=Me, b ) with Pd(OAc) 2 gave the acetato-bridged dinuclear compounds [Pd{C 6 H 5 Cue605C(R)C(H)ue605NCy}(O 2 CMe)] 2 (R=H, 1a ; R=Me, 1b ) after Cue5f8H 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 Cue605C(R)C(H)ue605NCy}(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 Cue605C(H)C(H)ue605NCy}(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 Cue605C(R)C(H)ue605NCy}(acac)], (R=H, 5a ; R=Me, 3b ) [Pd{C 6 H 5 Cue605C(H)C(Me)ue605NCy}(C 5 H 5 )] ( 4b ) and [Pd{C 6 H 5 Cue605C(H)C(Me)ue605NCy}(PPh 3 )] ( 5b) .