120120-97-0Relevant articles and documents
Thermal and photochemical reactivity of group VI open-mode bimetallic complexes based on a binucleating hexaphosphine ligand system. Crystallographic characterization of a novel ditungsten heptacarbonyl pentaphosphine compound
Saum, Suzanne E.,Fronczek, Frank R.,Laneman, Scott A.,Stanley, George G.
, p. 1878 - 1884 (2008/10/08)
The thermal and photochemical reactivities of an isomorphous series of group VI bimetallic complexes, M2(CO)6(eHTP) (M = Cr, Mo, W; eHTP = (Et2PCH2CH2)2PCH 2P(CH2CH2PEt2)2), are reported. Thermally, the pure complexes are stable to refluxing xylene for extended periods of time. In the synthesis of W2(CO)6(eHTP), however, the occasional in situ formation of tungsten metal causes a partial fragmentation of the eHTP ligand. Single-crystal X-ray data for the isolated yellow complex from this fragmentation shows that it crystallizes in the acentric monoclinic space group Pc with a = 15.072 (4) ?, b = 8.007 (2) ?, c = 15.104 (7) ?, β = 102.8 (1)°, V = 1778 (2) ?3, and Z = 2. The structure was refined to R = 0.029 and Rw = 0.039 by using 2281 unique data with Fo2 > 3σ(Fo2). The structure reveals a ditungsten heptacarbonyl compound with an unusual pentaphosphine ligand derived from eHTP with the formula W2(CO)7(C19H43P5). The original eHTP ligand has lost one of the four Et2PCH2CH2-arms, and the resulting unsaturated phosphorus atom has formed a new P-C bond (with loss of H) to the starred carbon atom on a Et2PC*H2CH2- arm from the other half of eHTP. This generates a multicycle pentaphosphine ligand that forms four- and five-membered chelate rings with one W(CO)3 moiety and a single standard five-membered bis(phosphine) chelate with the other W(CO)4 unit. The photolysis of the binuclear M2(CO)6(eHTP) (M = Cr, Mo, W) compounds in CH2Cl2 proceeds to give two distinct types of products: mer,mer-Cr2Cl6(eHTP) and M2Cl4(CO)4(eHTP) (M = Mo, W). Cr2(CO)6(eHTP) is extremely photoreactive toward CH2Cl2, with the chlorination reaction forming Cr2Cl6(eHTP) proceeding in good yield and driven by even ambient laboratory fluorescent lighting. The Mo and W systems are considerably less photoreactive, with mercury lamp irradiation taking 4-6 days to produce two isomeric forms of the open-mode 7-coordinate M2Cl4(CO)4(eHTP) (M = Mo, W) species.
