Treatment of complexes of type mer-[IrCl3(PMe2R)3](R = Ph or Me) with strong bases, LiNPri2, LiBun, or Li(CH2)5Li, gives the three-membered ring metallocycles [Ir[graphic omitted]MeR)(PMe2R)2], (4a) and (4b), in high yield. Treatment of mer-[IrCl3{PMe(CH2Ph)2}3] with LiNPri2 probably gives a mixture of geometrical and optical isomers [Ir[graphic omitted]HPh)}{PMe(CH2Ph)2}2], (6) and (7). These three-membered ring metallocycles with hydrogen chloride are quantitatively converted back to mer-[IrCl3(PR3)3]. The reaction of complex (4a) with X2(X = Cl, Br, and I) gives [IrCl2X(PMe2Ph)2(PMePhCH2X)](8a), (8b), and (8c) respectively. The mer isomer (8a) on irradiation with visible light gives the corresponding fac isomer (9). I.r., 1H, 13C, and 31P n.m.r. data are given and discussed. The crystal structure of (4a) has been determined and refined to R 0.047. Cell dimensions are a= 11.619(2), b= 9.248(2), c= 25.498(5)Ă , and Z= 4, space group P212121.