TRANSITION-METAL DERIVATIVES OF CYCLOPENTADIENYLPHOSPHINE LIGANDS .10. ((CYCLOPENTADIENYLETHYL)DIPHENYLPHOSPHINE)RHODIUM AND (CYCLOPENTADIENYLETHYL)DIPHENYLPHOSPHINE)IRIDIUM CHELATED AND BRIDGED COMPLEXES - CRYSTAL MOLECULAR-STRUCTURES OF THE CHELATED COMPLEXES (ETA-5-ETA-1-C5H4(CH2)2PPH2)RH(I)(C2H4) AND (ETA-5-ETA-1-C5H4(CH2)2PPH2)RH(III)I2

A series of new derivatives of (cyclopentadienylethyl)diphenylphosphine-a heterodifunctional ligand able to offer either chelating or bridging properties-has been synthesized from various rhodium and iridium derivatives. Interestingly, the synthesis of the monometallic chelated carbonyl compound (eta5:eta1-C5H4(CH2)2PPh2)Rh(CO) (8) starting from the square-planar dimeric complex [RhCl(CO)2]2 and [((diphenylphosphino)ethyl)cyclopentadienyl]lithium involves a pathway beginning with coordination of the phosphorus moiety of the difunctional ligand. This pathway then includes the transient formation of cisoid and transoid isomers, 9a,b, of the bridged dimetallic complex [(mu-eta5:eta1-C5H4(CH2)2PPh2)Rh(CO)]2, as kinetic products which transform into the thermodynamic product 8. A similar overall process is also suspected for the formation of the other chelated complexes-(eta5:eta1 C5H4(CH2)2PPh2)M(C2H4) (M = Rh (14), Ir (12)) and ((eta5:eta1-CrH4(CH2)2PPh2)M(cod) (M = Rh (15), Ir (16)), obtained from [RhCl-(C2H4)]2, [IrCl(C2H4)]n, and [MCl(cod)]2(M=Rh, Ir), respectively. From 8 and 12 the chelated diiodo compounds (eta5:eta1-C5H4(CH2)2 PPh2)M(III)I2 (M = Rh (17), Ir (18)) were also synthesized. All of the more stable products (8, 12, 14-18) were fully characterized by their spectroscopic data (including phosphorus-rhodium coupling constant measurements) and by electron impact mass spectroscopy. Complex 14 crystallizes in the monoclinic space group P2(1)/n with eight molecules in the unit cell, the dimensions of which are a = 9.808(1) angstrom, b = 28.515(3) angstrom, c = 13.094(1) angstrom, beta = 98.34(1)degrees, and V = 3623.3(8) angstrom3. Least-squares refinement leads to a value for the conventional R index of 0.031 for 3035 reflections having I > 3sigma(I). Complex 17 crystallizes in the monoclinic space group P2(1)/n with four molecules in the unit cell, the dimensions of which are a = 10.439(1) angstrom, b = 16.557(2) angstrom, c = 11.458(1), angstrom, beta = 95.85(1) angstrom, and V = 1970.1(8) angstrom3. Least-squares refinement leads to a value for the conventional R index of 0.027 for 1638 reflections having I > 3sigma(I). In both compounds 14 and 17, the P-C-C-C(Cp) chain of the chelating arm deviates from planarity but the H-1 NMR data clearly reveal for all the chelated complexes studied the occurrence of a fluxional process described essentially as an inversion of the Rh-P-CH2-CH2-C5H4 ring. In 14, this process is faster than the internal rotation also observed for the ethylene ligand.