Treatment of the dimer [Rh(mu-Cl)(C8H14)(2)](2) (1a) with 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene [xant((PPr2)-Pr-i)2] leads to the d(8) square-planar complex RhCl{xant((PPr2)-Pr-1)(2)} (2), whereas reaction of the iridium counterpart [Ir(mu-Cl)(C8H14)(2)](2) (1b) gives the d(6) octahedral compound IrHC{xant((PPr2)-Pr-i)[(PrPCH)-Pr-i(Me)CH2]} (3) as a result of the intramolecular C H bond activation of one of the isopropyl substituents of the phosphine. Stirring 2 and 3 in 0.5 N KOH solutions of 2-propanol gives rise to the formation of hydrides RhH{xant((PPr2)-Pr-i)(2)} (4) and IrH3{xant((PPr2)-Pr-i)(2)} (5), respectively. In n-octane at 60 degrees C, complex 2 is stable. However, compound 3 activates the alkane to give the cis-dihydride IrH2Cl{xant((PPr2)-Pr-i)(2)} (6) and a mixture of 3- and 4-octene. Complex 6 can be also obtained by the reaction of 3 with H-2. Under the same conditions, 2 affords the rhodium analogue RhH2Cl{xant((PPr2)-Pr-i)(2)} (7). Compounds 2-4 react with triflic acid (HOTf to give RhHCl(OTf{xant((PPr2)-Pr-i)(2)} (8), IrHCl(OTf{xant((PPr2)-Pr-i)(2)} (9), and RhH2(OTf{xant((PPr2)-Pr-i)(2)} (10), respectively. The related iridium derivative IrH2(OTf{xant((PPr2)-Pr-i)(2)} (11) has also been prepared by the reaction of 6 with Tl(OTf. Complexes 2, 6, and 9 have been characterized by X-ray diffraction analysis. The {xant((PPr2)-Pr-i)(2)}M skeleton is T-shaped with the metal center situated in the common vertex.