Synthesis and X-ray structure of cobalta-, rhodia- and iridia-cycloalkanes.The observation of novel structural features in the Me-cyclopentane ring

The metallacycloalkanes (e5-C5Me5M(CH2),(PPh3() M = Rh, n = 4-6; M = Ir, n = 4,5) and (e-C5H5)Co(CH2)4(PPh3) were prepared by the reaction of the alkylating reagents M'(CH2),M' (M' = MgBr, Li) with the appropriate dihalogeno complexes and were characterized by elemental analysis, IH NMR and mass spectroscopy, and protolytic and bromolytic decomposition studies. The crystal structures of the rhodium (l), iridium (4), and cobalt (6) metallacyclopentanes were determined from X-ray diffractometer data and refined by least squares. The crystal data and the final R values are as follows: 1, space group P21/n (Z = 4), with cell parameters a = 12.422 (1) A, b = 23.91 1 (2) A, c = 9.308 (1) A, @ = 97.75 (2)O, R = 0.047; 4, space group P2]/n ( Z = 4), with cell parameters a = 12.423 (1) %.b, = 23.949 (2) A, c = 9.344 81, ) A, @ = 98.25 (2)O, R = 0.055; 6, space group P2,/n (Z = 4), with cell parameters a = 16.018 (2) A, b = 15.673 (2) , c = 8.977 (1) A, @ = 103.33 (2)O, R = 0.039. All the structural details are discussed with the special reference to the puckering of the metallacyclic rings and to the different locations of shorter than "normal" C-C bond distances in the metallacyclopentane moieties.