Properties of [Pd2X2(dppm)2] (X = Cl, SnCl3, dppm = Bis(diphenylphosphino)methane) complexes on porous vycor glass

Abstract

Neste trabalho o vidro poroso Vycor foi utilizado como matriz para a imobilização de complexos contendo ligação metal-metal [Pd 2 Cl 2 (dppm) 2 ], [Pd 2 (SnCl 3 )Cl(dppm) 2 ] e [Pd 2 (SnCl 3 ) 2 (dppm) 2 ] A elevada reatividade das ligações metal-metal em reações de inserção de moléculas como CO e SO 2 é preservada no meio poroso, sendo reversível sob vácuo. Os espectros de RMN MAS 31 P, refletância difusa no infravermelho e Raman indicaram que há uma gama de interações possíveis entre o vidro e as moléculas, como resultado da disponibilidade de diferentes grupamentos presentes nas moléculas, bem como de uma topologia porosa irregular. O caráter estático das moléculas no ambiente restrito impede movimentos do anel Pd 2 P 4 C 2 entre as conformações barco e cadeira, de modo que as moléculas confinadas podem ter diferentes conformações.Porous Vycor glass (PVG) is used as a matrix for immobilization of complexes containing metal-metal bonds: [Pd 2 Cl 2 (dppm) 2 ], [Pd 2 (SnCl 3 )Cl(dppm) 2 ] and [Pd 2 (SnCl 3 ) 2 (dppm) 2 ]. The high reactivity of the metal-metal bonds in insertion reactions with small molecules such as CO and SO 2 is preserved in the pore medium, and is reversible under vacuum.31 P MAS-NMR and Raman spectra indicate that there is a range of interactions between the glass and the adsorbed molecules as a result of the availability of different groups in the molecules and of the irregular pore topology as well. The static character of the molecules in the restrictive pore environment precludes motions such as flipping of the ring Pd 2 P 4 C 2 between boat and chair conformations and rotation of the phenyl rings, and the molecules may present a range of conformations.Keywords: palladium complexes, Vycor, immobilization, 31 P NMR, Raman, metal-metal bond IntroductionMany adsorption studies related to organometallic compounds and transition metal complexes on porous glasses have been performed with the purpose of applications such as catalysis 1,2 and formation of nanoparticles by thermal decomposition or photolysis of the molecular species. [3][4][5][6][7] In this area, a number of papers describe the immobilization of carbonyl complexes of iron 3-7 and ruthenium 8-10 onto porous glasses, since these complexes are good precursors to metallic or oxide particles via thermal and photochemical decomposition.Immobilization studies of transition metal phosphine complexes were limited for many years by the lack of suitable characterization techniques. Infrared spectroscopy is very useful in the characterization of carbonyl complexes embedded in porous glasses, giving however spectra dominated by the silica matrix bands in the case of phosphine complexes. The use of solid-state NMR techniques in addition to complementary vibrational measurements can be helpful in providing information about the structure and interactions between molecules and substrates. 15 These compounds take part in different types of reactions, such as additions, substitutions and insertions, owing to the presence of a single metal-metal b...

Bimetallic oxamato complexes synthesized into mesoporous matrix as precursor to tunable nanosized oxide

“…These porous surface contains silanol groups, with acid hydrogens (pK a $ 9), which can be used as active sites for the incorporation of several compounds. A great variety of nanocomposites with PVG has been successfully produced using organometallic compounds, coordination compounds, semiconductors, oxides, and polymers to different goals [17,[23][24][25][26][27][28].…”