28625-02-7Relevant articles and documents
The extraordinary ability of guanidinate derivatives to stabilize higher oxidation numbers in dimetal units by modification of redox potentials: Structures of Mo25+ and Mo26+ compounds
Cotton, F. Albert,Daniels, Lee M.,Murillo, Carlos A.,Timmons, Daren J.,Wilkinson, Chad C.
, p. 9249 - 9256 (2002)
Full characterization of the first homologous series of dimolybdenum paddlewheel compounds having electronic configurations of the types σ2π4σx, x = 2, 1, 0, and Mo-Mo bond orders of 4, 3.5, and 3, respectively, has been accomplished with the guanidinate-type ligand hpp (hpp = the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). Essentially quantitative oxidation of Mo2(hpp)4, 1, by CH2Cl2 gives Mo2(hpp)4Cl, 2. The halide in 2 can be replaced by reaction with TlBF4 to produce Mo2(hpp)4(BF4); 3. Further oxidation of 2 by AgBF4 produces Mo2(hpp)4ClBF4, 4. The change from bond order 4 (in 1) to 3.5 in Mo2(hpp)4Cl is accompanied by an increase in the Mo-Mo bond length of 0.061 to 2.1280(4) A. A further increase of 0.044 A in the Mo-Mo distance to 2.172(1) A is observed as the bond order decreases to 3 in 4. At the same time, the Mo-N distances decrease smoothly as the oxidation state of the Mo atoms increases. Electrochemical studies have shown two chemically reversible processes at very negative potentials, E1/21 = -0.444 V and E1/21 = -1.271 V versus Ag/AgCl. These correspond to the processes Mo26+/5+ and Mo25+/4+, respectively. The latter potential is displaced by over 1.5 V relative to those of the Mo2(formamidinate)4 compounds and the first one has never been observed in such complexes. Thus, in surprising contrast to previously observed behavior of the dimolybdenum unit, when it is surrounded by the very basic guanidinate ligand hpp, there is an extraordinary stabilization of the higher oxidation numbers of the molybdenum atoms.
Synthesis and catalytic properties of molybdenum(VI) complexes with tris(3,5-dimethyl-1-pyrazolyl)methane
Neves, Patricia,Gago, Sandra,Balula, Salete S.,Lopes, Andre D.,Valente, Anabela A.,Cunha-Silva, Luis,Paz, Filipe A. Almeida,Pillinger, Martyn,Rocha, Joao,Silva, Carlos M.,Gonc-Alves, Isabel S.
, p. 3490 - 3500 (2011/07/07)
The complex [MoO2Cl{HC(3,5-Me2pz)3}] BF4 (1) (HC(3,5-Me2pz)3 = tris(3,5-dimethyl-1- pyrazolyl)methane) has been prepared and examined as a catalyst for epoxidation of olefins at 55 °C using tert-butyl hydroperoxide (TBHP) as the oxidant. For reaction of cis-cyclooctene, epoxycyclooctane is obtained quantitatively within 5 h when water is rigorously excluded from the reaction mixture. Increasing amounts of water in the reaction mixture lead to lower activities (without affecting product selectivity) and transformation of 1 into the trioxidomolybdenum(VI) complex [{HC(3,5-Me2pz)3}MoO 3] (4). Complex 4 was isolated as a microcrystalline solid by refluxing a suspension of 1 in water. The powder X-ray diffraction pattern of 4 can be indexed in the orthorhombic Pnma system, with a = 16.7349(5) A, b = 13.6380(4) A, and c = 7.8513(3) A. Treatment of 1 in dichloromethane with excess TBHP led to isolation of the symmetrical [Mo 2O4(μ2-O){HC(3,5-Me2pz) 3}2](BF4)2 (2) and unsymmetrical [Mo2O3(O2)2(μ2- O)(H 2O){HC(3,5-Me2pz)3}] (3) oxido-bridged dimers, which were characterized by single-crystal X-ray diffraction. Complex 2 displays the well-known (Mo2O5)2+ bridging structure where each dioxidomolybdenum(VI) center is coordinated to three N atoms of the organic ligand and one μ2-bridging O atom. The unusual complex 3 comprises dioxido and oxidodiperoxo molybdenum(VI) centers linked by a μ2-bridgingO atom, with the former center being coordinated to the tridentate N-ligand. The dinuclear complexes exhibit a similar catalytic performance to that found for mononuclear 1. For complexes 1 and 2 use of the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate and N-butyl-3-methylpyridinium tetrafluoroborate as solvents allowed the complexes to be completely dissolved, and in each case the catalyst and IL could be recycled and reused without loss of activity.
Organic thallium compounds. Synthesis and chemical properties of phenylthallium(III) bis(tetrafluoroborate)
Gun'kin,Pankst'yanov,Popova,Kleimenova
, p. 37 - 39 (2007/10/03)
Phenylthallium(III) bis(tetrafluoroborate) was obtained by the reaction of phenylthallium dihydroxide with tetrafluoroboric acid in ether.
