Transition-metal complexes of cyclopentadienylphosphines XIV. Reduction reactions of various derivatives of the chelate fragment [{ η5: η1-C 5H 4(CH 2) 2PPh 2}M III] 2+, M = Rr Ir

Abstract

Iodide abstraction by silver salts from the complexes [{ η 5: η 1-C 5H 4(CH 2) 2PPh 2}MI 2], ( 1, M = Rh; 2, M = Ir), yields products whose structures are dependent on the coordinating ability of the anion originally associated with silver. Silver trifluoroacetate gave fully characterized disubstituted derivatives of the type [{ η 5: η 1-C 5H 4(CH 2) 2PPh 2}M(CF 3COO) 2], ( 3, M = Rh; 4, M = Ir), in which the trifluoroacetate anions are bound in a monodentate fashion. Silver hexafluorophosphate gave a dinuclear dicationic compound [{{ η 5: η 1-C 5H 4(CH 2) 2PPh} 2}Rh (μ−1)} 2][PF 6] 2, 5, in which the metal atoms are bridged by iodide. Complex 3 crystallizes in the triclinic space group P 1 with two molecules in the unit cell, with a = 8.3060(7) A ̊ , b = 18.289(2) A ̊ , c = 7.9724(8) A ̊ , α=94.178(8)°, β = 106.477(8)°, γ = 93.964(7)° and V = 1153.2(2) A ̊ 3 . Least squares refinement leads to conventional R values R( F o ) = 0.041 and Rw = 0.042 for 3361 reflections having 1 > 3σ(1). Complex 5 crystallizes 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 are a = 13.838(1) A ̊ , b = 13.403(1) A ̊ , c = 14.362(1) A ̊ , β = 104.73(1)° and V = 2576.2(5) A ̊ 3 . Least squares refinement leads to conventional R values R( F o ) = 0.034 and Rw = 0.040 for 2246 reflections having 1 > 2σ(1). Surprisingly, the treatment of the bis-trifluoroacetato complexes 3 and 4 with lithium triethylhydroborate yields quantitatively the ethylene metal(I) derivatives [{ η 5: η 1-C 5H 4(CH 2) 2PPh 2}M(C 2H 4)], ( 9, M = Rh; 10, M = Ir), whereas unstable polyhydride derivatives result from the reaction of the diiodo complex 1 with lithium triethylhydroborate, and from the reaction of the bis-trifluoroacetato complex 3 with sodium tetrahydroborate. The chemical or electrochemical reduction of complex 5 leads to the solvated rhedium(III) species. [{( η 5: η 1-C 5H 4(CH 2) 2PPh 2}RhI(THF)][PF 6], 6, together with a dinuclear rhodium(II) species. [{{ η 5: η 1-C 5H 4(CH 2) 2PPh 2}RhI} 2], 7. The protonation of 7 with tetrafluoroboric acid affords the monocationic dinuclear complex [{{ η 5: η 1-C 5H 4(CH 2) 2PPh 2}RhI} 2}H][BF 4], 8, in which the added proton bridges the rhodium atoms.