The rhodium(I) and iridium(I) isocyanide complexes [M(CNR)4]Z (M = Rh, Z = PF6, R = Me, Pri. cyclohexyl, But, p-MeOC6H4, p-MeC6H4, or p-ClC6H4; M = Rh, Z = Cl, R = But or p-ClC6H4; M = Ir, Z = PF6, R = But or p-ClC6H4) have been prepared. These undergo oxidative addition reactions giving trans-[M(CNR)4XY]+(various R; X = Cl, Y = Cl, PhCH2, C3H5, C3H4Me, MeCO, HgCl, or SnCl3; X = Br, Y = Br, CN, PhCH2, or C3H5; X = I, Y = I, Me, CF3, or C3F7). Addition of NO+, p-MeC6H4N2+, or SO2 afforded [Rh(NO)(CNR)4][PF6]2(R = Pri, cyclohexyl, or But), [Rh{N2(p-MeC6H4)}(CNBut)4][PF6]2 and [Rh(SO2)(CNR)4][PF6](R = Pri or p-MeC6H4), respectively. Treatment of [Rh(π-C3H6)2Cl]2 with one or two moles of RNC (R =p-MeC6H4), afforded either [Rh(π-C3H5)2(CNR)Cl] or [Rh(π-C3H5)(σ-C3H5)(CNR)2Cl].