Reactions of halogeno(phenyl)alkynes with complexes of platinum(0), palladium(0), rhodium(I), and iridium(I). The preparation of [1—2-η-chloro(phenyl)ethyne]bis(triphenylphosphine)platinum(0) and chloro-[1—2-η-chloro(phenyl)ethyne]bis(triphenylphosphine)rhodium(I) and the kinetics of isomerisation of the former to an alkynyl complex