Activation of C-F and C-H bonds by polyalkylcyclopentadienylrhodium complexes:: crystal structure of [(η5-C5Me4Et)RhCl{(C6F5)2PCH2CH2P(C6F5)2}]+.BF4-

The reaction between [(eta(5)-C5Me4Et)RhCl(mu-Cl)](2) and the diphosphine, (C6F5)(2)PCH2CH2P(C6F5)(2) (dfppe), proceeded via the activation of two C-F and two C-H bonds and the formation of two C-C bonds to give a mixture of isomers of a salt with formulation '[(eta(5)-C5Me4Et)RhCl{(C6F5)(2)PCH2CH2P(C6F5)(2)}-2HF](+). Cl-' (3a). Treatment of [(eta(5)-C5Me4Et)RhCl(mu-Cl)](2) with NH4BF4 followed by dfppe yielded [(eta(5)-C5Me4Et)RhCl{(C6F5)(2)PCH2CH2P(C6F5)(2)}](+). BF4- (4b) which, on thermolysis in ethanol underwent C-F and C-H bond activation to yield the tetrafluoroborate salt of 3a (3b). The structure of 4b was determined by a single crystal X-ray diffraction study. The salt 4b crystallizes in the triclinic space group P (1) over bar with a = 15.743 (4), b = 16.429 (2), c = 16.970 (3) Angstrom, alpha = 79.41 (2), beta = 84.34 (2), gamma = 82.01 (2)degrees and Z = 4. Refinement gave final R-1 and wR(2)[I > 2 sigma(I)] values of 0.0955 and 0.2200 respectively for 7254 observed reflections. When the reaction between [(eta(5)-C5Me4Et)RhCl(mu-Cl)](2) and dfppe was carried out in ethanol, a mixture of 3b, 4b and the singly C-F bond activated complex '[(eta(5)-C5Me4Et)RhCl{(C6F5)(2)PCH2CH2P(C6F5)(2)}-HF]+. BF4-' (5b) were obtained after addition of NH4BF4. The monophosphines P(C6F5)(3) and PPh(C6F5)(2) failed to react with [(eta(5)-C5Me5)RhCl(mu-Cl)](2) and the reaction between [(eta(5)-C5Me5)RhCl(mu-Cl)](2) and PPh2(C6F5) did not lead to C-F bond activation but yielded (eta(5)-C5Me5)RhCl2{PPh2(C6F5)} (6). (C) 1998 Elsevier Science S.A. All rights reserved.