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• 51752-03-5 Mo₂Cl₄(C₅NH₅)4 

Relevant academic research and scientific papers

Tetrahalobis(diphosphine)dimolybdenum(II) compounds: β Isomers with seven-membered rings

The compound β-Mo2Cl4(1,3-dppp)2, where 1,3-dppp represents Ph2PCH2CH2CH2PPh2, has now been obtained in crystalline form, and its structure has been determined. The β-Mo2Br4(1,3-dppp)2 analogue has also been prepared. The presence of seven-membered MoMoPCCCP rings has been confirmed and the ring conformation established in detail. β-Mo2Cl4(1,3-dppp)2 crystallizes in space group P1 with Z = 4. The unit cell dimensions are a = 16.150 (4) A?, b = 19.054 (5) A?, c = 19.622 (5) A?, α = 72.67 (2)°, β = 87.06 (2)°, γ = 87.46 (2)°, and V = 5754 (3) A?3. Each of the two crystallographically independent molecular sites is occupied by a principal isomer and a secondary isomer with P:S ratios of 3:1 and 2:1. As in all previous cases, at each site only one set of ligand atoms could be located and refined, but the two differently oriented (essentially perpendicular) Mo2 units were easily recognized. The two P and two S isomers form very similar pairs, but P and S isomers have opposite chiralities. Average P-Mo-Mo-P twist angles for P and S isomers are -70.3 [2] and 74 [2]°, respectively, at one molecular site (site A) and are 68.5 [6] and -74.7 [4]°, respectively, at the other (site B). Mo-Mo, Mo-Cl, and Mo-P distances are perhaps slightly different in the P and S isomers.

Reactions of chloro complexes of dimolybdenum(II) containing quadruple metal-metal bonds with bidentate tertiary phosphines (C6H5)2P(CH2)n,P(C 6H5)2 (n = 1-3) and (C6H5)2P(CH2)2As(C 6H5)2 in alcohol media

The reactions of K4Mo2Cl8 with the bidentate tertiary phosphines bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1-(diphenylphosphino)-2-(diphenylarsino)ethane (arphos), and 1,3-bis(diphenylphosphino)propane (dppp) in methanol, ethanol, and 1-propanol produce complexes of the type Mo2Cl4(LL)2. The reactions of Mo2Cl4(py)4 and Mo2Cl4(P(n-Pr)3)4 with dppe and dppp have also been explored. The only form of Mo2Cl4(dppm)2 isolated from the three alcoholic solvents is the species known to have a bridging dppm structure. In refluxing methanol both Mo2Cl84- and Mo2Cl4(py)4 yield α-Mo2Cl4(LL)2 complexes (LL = dppe, dppp), whose spectral properties are consistent with structures containing chelating phosphine ligands. In 1-propanol these reactants lead to β-Mo2Cl4(LL)2 complexes (LL = dppe, dppp), which are believed to exhibit structures with a trans disposition of donor atoms in the MoCl2P2 moiety and with the phosphine bridging the Mo2 unit. Reaction in ethanol gives rise to mixtures. Under refluxing conditions only β-Mo2Cl4(arphos)2 is produced in pure or nearly pure form from K4Mo2Cl8 and arphos, whereas in methanol at lower temperatures mixtures of α and β isomers result from reaction with (NH4)5[Mo2Cl8]Cl·H 2O. The chelating isomers are converted to the bridging forms on reflux in 1-propanol or prolonged reflux in methanol (arphos, dppp). These results indicate a thermodynamic stabilization of the β-Mo2Cl4(LL)2 species in the higher alcohols while the α isomers are the kinetically favored products in methanol. Although the reaction of Mo2Cl4(P(n-Pr)3)4 and dppe in methanol yields a mixture of α- and β-Mo2Cl4(dppe)2, the reaction with dppp produces Mo2Cl4(P(n-Pr)3)2(dppp), whose spectral properties are similar to those of the known Mo2Cl4(PR3)4 species.