TRANSITION-METAL COMPLEXES OF CYCLOPENTADIENYLPHOSPHINES .14. REDUCTION REACTIONS OF VARIOUS DERIVATIVES OF THE CHELATE FRAGMENT [(ETA(5)ETA(1)-C5H4(CH2)(2)PPH2)M-III](2+), M=RH, IR

Iodide abstraction by silver salts from the complexes [{eta 5:eta(1)-C 5H4(CH2)(2)PPh2}MI2], (1, M = Rh; 2, M = Ir), yields products whose st ructures are dependent on the coordinating ability of the anion origin ally associated with silver. Silver trifluoroacetate gave fully charac terized disubstituted derivatives of the type [{eta(5):eta(1)-C5H4(CH2 )(2)PPh2}M(CF3COO)(2)], (3, M = Rh; 4, M = Ir), in which the trifluoro acetate anions are bound in a monodentate fashion. Silver hexafluoroph osphate gave a dinuclear dicationic compound (5):eta(1)-C5H4(CH2)(2)PP h2}Rh(mu-I)}(2)][PF6](2), 5, in which the metal atoms are bridged by i odide. Complex 3 crystallizes in the triclinic space group P1 with two molecules in the unit cell, with a=8.3060(7)Angstrom, b=18.289(2)Angs trom, c=7.9724(8)Angstrom, alpha=94.178(8)degrees, beta = 106.477(8)de grees, gamma = 93.964(7)degrees and V = 1153.2(2)Angstrom(3). Least sq uares refinement leads to conventional R values R(F-0) = 0.041 and Rw = 0.042 for 3361 reflections having I > 3 sigma(I). Complex 5 crystall izes in the monoclinic space group P2(1)/c with two molecules of 5 and two molecules of acetone in the unit cell, the dimensions of which ar e a=13.838(1)Angstrom, b=13.403(1)Angstrom, c=14.362(1)Angstrom beta = 103.73(1)degrees and V = 2576.2(5)Angstrom(3). Least squares refineme nt leads to conventional R values R(F-0) = 0.034 and Rw = 0.040 for 22 46 reflections having I > 2 sigma(I). Surprisingly, the treatment of t he bis-trifluoroacetato complexes 3 and 4 with lithium triethylhydrobo rate yields quantitatively the ethylene metal(I) derivatives [{eta(5): eta(1)-C5H4(CH2)(2)PPh2}M(C2H4)], (9, M = Rh; 10, M = Ir), whereas uns table polyhydride derivatives result from the reaction of the diiodo c omplex 1 with lithium triethylhydroborate, and from the reaction of th e bis-trifluoroacetato complex 3 with sodium tetrahydroborate. The che mical or electrochemical reduction of complex 5 leads to the solvated rhodium(III) species, [{eta(5):eta(1)-C5H4(CH2)(2)PPh2}RhI(THF)][PF6], 6, together with a dinuclear rhodium(II) species, [{{eta(5):eta(1)- C 5H4(CH2)(2)PPh2}RhI}, 7. The protonation of 7 with tetrafluoroboric ac id affords the monocationic dinuclear complex [{{eta(5):eta(1)-C5H4(CH 2)(2)PPh2}RhI)(2)}H][BF4], 8, in which the added proton bridges the rh odium atoms.