Germanes, R3GeH (R = Me, Et, or Cl) react with (Ph3P)2Ir(CO)CI to form six-co-ordinate dihydrido-complexes, (Ph3P)2Ir(CO)(H)2GeR3(IV); their stereochemistry in solution has been elucidated from their 1H n.m.r. and i.r. spectra. Triphenylgermane behaves differently forming the five-co-ordinate complex, Ph3PIr(CO)(H)(CI)-GePh3(XII). The Ge–Ir bond in (IV)(R = Me or Et) is cleaved at 150° with regeneration of the germane. It is also cleaved by oxygen, C2H4Br2, I2, and HCI, H2, and HgCl2. Triphenylphosphine in (IV) may be replaced by Et3P or (Ph2PCH2)2. Ethylene is hydrogenated by (IV) to yield the iridium(I) complex, (Ph3P)2Ir(CO)GeR3(XI) which is reconverted into (IV) by H2. Trimethylgermane and (Et3P)2Ir(CO)CI form H2, Me6Ge2, and (Et3P)2Ir(CO)(H)2CI. Bistrimethylgermylmercury and (Ph3P)2Ir(CO)CI react to give the germylmercury complex (Ph3P)2Ir(CO)·Hg·GeMe3 together with mercury and trimethylchlorogermane.