Intermolecular c-cl activation reaction of (pi(5)-c5r5)re(co)(3) (r = h, me) with pentachlorobenzene: x-ray structure of cis- and trans-(eta(5)-c5me5)re(co)(2)(2,3,4,5-c6hcl4)cl and its conversion to (eta(6)-c5me4ch2)re(co)(2)(2,3,4,5-c6hcl4)