SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF ([RE2CL4(PME2PH)4]N+ (N = 0, 1, OR 2) - A SERIES OF COMPLEXES POSSESSING METAL METAL BOND ORDERS OF 4, 3.5, AND 3 AND THE DEPENDENCE OF BOND LENGTH UPON BOND ORDER
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The following three compounds have been prepared in crystalline form and thoroughly characterized by chemical, electrochemical, magnetic, spectroscopic, and structural methods: Re2Cl4(PMe2Ph)4, 1; [Re2Cl4(PMe2Ph)4](PF6), 2; [Re2Cl4(PMe2Ph)4](PF6)2, 3. Compound 1 forms crystals in space group C2/c with a = 17.571 (2) A, b = 9.991 (1) A, c = 22.316 (3) , - 107.47 (1), V= 3737 (1) 3, and Z = 4. Olive green 2, obtained by oxidation of i with NOPF6, crystallizes in space group P21/c with a = 10.596 (2) A, b = 33.129 (6) , c = 13.801 (2) ;, = 111.16 (1), V= 4518 (2) 3, and Z = 4. Compound 3, also green and also obtained from 1 by oxidation with NOPF6, crystallizes in space group P21/c with a = 24.317 (8) , b = 10.485 (4) , c = 20.284 (7) , = 111.61 (3), V= 4808 (3) 3, and Z = 4. Compounds 1-3 are reversibly electrochemically interconvertible with 1/2 values of +0.85 and -0.26 V vs. SCE. 1 and 3 are diamagnetic while 2 has a magnetic moment of 1.35 B (per Re2 unit) and exhibits an ESR spectrum with g| = 2.19 and g = 2.24. Compound 2 has its * transition at 1360 nm. In going through the series 1 to 2 to 3, the Re-Cl distances decrease (ca. 0.048 at each step), the Re-P distances increase (ca. 0.045 A at each step), and the Re-Re distances change by -0.023 (2) A from 1 to 2 and by -0.003 (2) A (i.e., not significantly) from 2 to 3. These bond length changes, which do not correlate simply with the bond order, are discussed and explanations proposed. 1983, American Chemical Society. All rights reserved.
