84835-95-0Relevant academic research and scientific papers
Stereochemistry of R2PX2- ligands (X2 = S2, OS, or O2) in molybdenum(II) dimers and polymers. A facile isomerization about the Mo-4Mo core
Burk, Johst H.,Whitwell II, George E.,Lemley, John T.,Burlitch, James M.
, p. 1306 - 1314 (2008/10/08)
Stoichiometric reactions of K4Mo2Cl8 with MS2PR2 (M = K or Na; R = C2H5 or C6H5) in aqueous methanolic media yielded green, diamagnetic tetrakis((diorganophosphino)dithioato)dimolybdenum(II) species, Mo2(S2PR2)4, characterized by analysis and by IR, NMR, and UV-visible spectroscopy. The diphenyl derivative was also synthesized from the reaction of Mo2(OAc)4 with excess (C6H5)2PS2H in diglyme. An X-ray crystal structure analysis of Mo2(S2PEt2)4 revealed the presence of two bridging and two chelating (diethylphosphino)dithioato groups coordinated with virtual C2υ symmetry to the Mo2 core having a Mo-Mo separation of 2.137 (1) A?. The complex crystallizes from toluene and hexane in the triclinic space group P1 with a = 11.543 (1) A?, b = 14.526 (1) A?, c = 11.293 (1) A?, α = 92.03 (1)°, β = 107.33 (1)°, γ = 85.82 (1)°, and Z = 2. Two Lewis base adducts of Mo2(S2PEt2)4 have also been isolated. The THF complex, Mo2(S2PEt2)4·THF, is a tetrabridged isomer of the preceding compound with virtual D4h symmetry and crystallizes from THF solution in space group P1 with a = 10.722 (1) A?, b = 9.741 (2) A?, c = 10.356 (1) A?, α = 108.71 (1)°, β = 116.79 (1)°, γ = 79.88 (1)°, and Z = 1. The structure, refined to a residual R = 0.044, displays a Mo-Mo bond length of 2.123 (1) A? and a single axially coordinated THF molecule with a Mo-O distance of 3.017 (12) A?. The analogous pyrazine complex, Mo2(S2PEt2)4·C 4H4N2, crystallizes from toluene and is found to be isomorphous with Mo2(S2PEt2)4·THF by X-ray powder diffraction. The novel equilibrium between the two isomers of Mo2(S2PEt2)4 was investigated by 31P NMR spectroscopy and appears to be the first such equilibrium reported for a Mo24+ system. In noncomplexing solvents, the C2υ isomer is favored by 5:2, while in THF the concentrations of the two isomers are approximately equal. Tetrakis((diethylphosphino)thioato)dimolybdenum(II), Mo2(SOPEt2)4, and the bis(dialkylphosphinato)molybdenum(II) compounds. [Mo(O2PRR′)2]x (R = R′ = n-octyl or C6H5; R = Me and R′ = C6H5) were all prepared by metathesis between K4Mo2Cl8 and the potassium salts of SOPEt2- or O2PRR′-, respectively. The first was isolated as a THF monoadduct and found to be tetrabridged by 31P NMR spectroscopy and a partial X-ray single-crystal structure determination. The last three are polymeric, weakly paramagnetic materials in which the molybdenum(II) ions are separated and probably in distorted octahedral environments.
