STRUCTURAL AND SPECTROSCOPIC STUDIES OF 2 PHASES OF THE ORGANOMETALLIC CHAIN POLYMER [RU-2(MU(2)MU(2)ETA(2)-O2PME2)(2)(CO)(4)](N)

The microcrystalline organometallic coordination polymer [Ru-2{mu(2):m u(2):eta(2)-O2PMe2}(CO)(4)](n) which results from the oxidative additi on of dimethylphosphinic acid to triruthenium dodecacarbonyl has been structurally characterized by X-ray powder diffraction, lambda = 1.149 49(1) Angstrom, at 295 and 50 K. At roam temperature the crystallites have a monoclinic unit cell with the space group C2/c with lattice co nstants a = 18.0792(3) Angstrom, b = 9.0626(2) Angstrom, c = 10.0372(2 ) Angstrom, beta = 112.107(1)degrees, and Z = 4; the final refinement of 52 variables converged to R-p, R-wp, R-F, and R-F2 of 8.2, 10.8, 4. 6, and 8.3%, respectively, for data collected between 4 and 60 degrees (2 theta). At 50 K the phase is described by a triclinic unit cell, s pace group P (1) over bar, and is characterized by the lattice constan ts a = 9.8639(6) Angstrom, b = 8.9290(6) Angstrom, c = 9.8870(5) Angst rom, alpha = 115.051(3)degrees, beta = 108.587(5)degrees, gamma = 92.0 15(5)degrees, and Z = 2; the final refinement of 102 variables converg ed to and R-p, R-wp, R-F, and R-F2 of 8.3, 12.4, 1.5, and 3.0%, respec tively, for data collected between 3 and 74 degrees (2 theta). The tra nsition between the two crystalline phases has been determined by diff erential scanning calorimetry to occur at circa 220 K, and the most pr onounced difference in the environment of the chains, as determined by variable-temperature LR spectroscopy, is in the rho(PCH3) modes for t he bridging dimethylphosphinate ligands.