Article

Synthesis, characterization and olefin/CO exchange reactions of pyrazolylborato complexes of copper(I)

Università di Pisa, Dipartimento di Chimica e Chimica Industriale, Via Risorgimento 35, I-56126, Pisa, Italy.
Dalton Transactions (Impact Factor: 4.1). 08/2006; DOI: 10.1039/b600915h
Source: PubMed

ABSTRACT New bis(pyrazolyl)borato olefin complexes of copper(I) of general formula Cu[BH2(3,5-(CF3)2Pz)2](olefin) have been prepared (olefins: coe = cyclooctene, van = 4-vinylanisole, clsty = 4-chlorostyrene, tevs = triethylvinylsilane, fn = fumaronitrile). The structures of Cu[BH2(3,5-(CF3)2Pz)2](L), L = coe, van, tevs, fn, have been determined by X-ray diffraction methods. Considering the two N atoms of the bis(pyrazolyl)borate ligand and the midpoint of the C-C double bond of the coordinated olefin, the compounds with L = coe, van and tevs contain a copper atom in a trigonal planar coordination. A coordination polymer with N-coordinated fumaronitrile and tetrahedral coordination of copper atoms is obtained in the case of L = fn. The carbonylation reactions of Cu[BH(2)(3,5-(CF3)2Pz)2](olefin) (olefin = coe, clsty, van, tevs), Cu[BH2(3,5-(CF3)2Pz)2](olefin) + CO<==>Cu[BH2(3,5-(CF3)2Pz)2](CO) + olefin, have been studied gas volumetrically and the thermodynamical parameters of the equilibria for the displacement of the coordinated olefin by carbon monoxide have been determined. These data for copper(I) are compared with those reported in the literature.

0 Followers
 · 
66 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: New fluorinated bis(pyrazolyl)methanes with the general formula RCH(PzF)2 [R = H, PzF = 3-(trifluoromethyl)pyrazolyl, 3,5-bis(trifluoromethyl)pyrazolyl; R = Ph, PzF = 3,5-bis(trifluoromethyl)pyrazolyl] have been prepared, and their reactivity with copper and silver salts has been studied. Copper derivatives Cu[RCH(PzF)2](L)(OTf) [R = H, PzF = 3-(trifluoromethyl)pyrazolyl, 3,5-bis(trifluoromethyl)pyrazolyl; R = Ph, PzF = 3,5-bis(trifluoromethyl)pyrazolyl, L = CO, cyclooctene (coe); R = Ph, PzF = 3,5-bis(trifluoromethyl)pyrazolyl, L = coe, 4-vinylanisole (van), and triethylvinylsilane (tevs)] have been isolated by reacting Cu(OTf)(toluene)0.5 with the bis(pyrazolyl)methane ligand in the presence of olefin or CO. Some of them have been structurally characterized (R = H, PzF = 3-(trifluoromethyl)pyrazolyl, 3,5-bis(trifluoromethyl)pyrazolyl, L = CO). These compounds are monomeric and show strong interactions between copper and one oxygen atom of the triflate moiety. [Bis[3,5-bis(trifluoromethyl)pyrazolyl]methyl]silver complexes have been prepared from AgBF4 and the ligand. The coe derivative [Ag{CH2(3,5-(CF3)2Pz)2}(coe)]BF4 has been obtained in good yields.
    Organometallics 07/2007; 26(17). DOI:10.1021/om700325t · 4.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sodium salts of two new tris(pyrazolyl)borates [HB(4-Cl-3,5-(CF3)2Pz)3](-) and [HB(4-(NO2)-3,5-(CF3)2Pz)3](-), which are not only highly fluorinated, but also loaded with additional electron-withdrawing substituents, have been synthesized by reacting 4-Cl-3,5-(CF3)2PzH or 4-(NO2)-3,5-(CF3)2PzH with NaBH4 under nitrogen in a solventless process, and isolated after a work up in tetrahydrofuran (THF) or diethyl ether (Et2O), as their THF or Et2O adducts. Metathesis of these sodium salts with AgOTf in THF leads to [HB(4-Cl-3,5-(CF3)2Pz)3]Ag(THF) and [HB(4-(NO2)-3,5-(CF3)2Pz)3]Ag(THF). The corresponding cis-cyclooctene (c-COE) complexes [HB(4-Cl-3,5-(CF3)2Pz)3]Ag(c-COE) and [HB(4-(NO2)-3,5-(CF3)2Pz)3]Ag(c-COE) were obtained by displacing THF with cis-cyclooctene. The related [HB(3,5-(CF3)2Pz)3]Ag(c-COE) can also be obtained via a similar process. X-ray crystal structures show that [HB(4-(R)-3,5-(CF3)2Pz)3]Ag(c-COE) (R = H, Cl, NO2) feature pseudo-tetrahedral silver sites supported by κ(3)-bound tris(pyrazolyl)borate ligands. [HB(4-(NO2)-3,5-(CF3)2Pz)3]Ag(c-COE) displays the smallest upfield shift of the alkene carbon peak (versus free alkene) followed by [HB(4-Cl-3,5-(CF3)2Pz)3]Ag(c-COE) and [HB(3,5-(CF3)2Pz)3]Ag(c-COE). Experimental and computational data indicate very electron poor silver(i) sites in all three [HB(4-(R)-3,5-(CF3)2Pz)3]Ag(c-COE) adducts with minimal Ag → (cis-cyclooctene) backbonding. Although the impact of R (H, Cl, NO2) on the alkene carbon chemical shift of these adducts and the olefin π/π* populations is small, the (13)C NMR chemical shifts and NBO analysis suggest that [HB(4-(NO2)-3,5-(CF3)2Pz)3]Ag(c-COE) possesses the most electrophilic metal site, which correlates with the pKa values of the free pyrazoles. [HB(4-(R)-3,5-(CF3)2Pz)3]Ag(c-COE) adducts effectively catalyze the insertion of the carbene moiety of ethyl diazoacetate into C-H bonds of 2,3-dimethylbutane. The [HB(4-(NO2)-3,5-(CF3)2Pz)3]Ag(c-COE) catalyst shows a higher selectivity for primary C-H bonds compared to the reactions catalyzed by [HB(3,5-(CF3)2Pz)3]Ag(c-COE).
    Dalton Transactions 09/2013; 42(43). DOI:10.1039/c3dt52152d · 4.10 Impact Factor