THE REACTION OF (PPRI3)2CL2H2IR WITH PHOSPHINES - CRYSTAL AND MOLECULAR-STRUCTURES OF MER-CIS-(PME2PH)2(PPRI3)-CIS-CL2HIRIII AND MER-CIS-(PME2PH)2(PPRI3)-TRANS-CL2HIRIII

Ambient temperature reactions of the complex (PPr3i)2H2Cl2Ir(IV) (1) with ethyl-substituted monodentate phosphine ligands axe shown to yield different product types to those obtained both with methyl-substituted analogues and with phosphine itself. With the phosphines PH3 and PMe3-nPhn (n = 0, 1) there is spontaneous reaction to give the complexes mer-trans-(PPr3i)2(PR3)H-trans-Cl2Ir(III), whereas with PEt3-nPhn (n = 0-2) the reaction yields mer-cis-(PR3)2(PPr3i)H-trans-Cl2Ir(III) complexes. Under reflux the phosphines PMe3 and PMe2Ph also yield mer-cis-(PR3)2(PPr3i)H-trans-Cl2Ir(III) complexes [PR3 = PMe3 (2), PMe2Ph (3)]. The differing course of the reactions of (1) with PMe3 and with PEt3 has permitted the synthesis of mer-(PMe3)-trans-(PPr3i)(PEt3)H-trans-Cl2Ir(III), the first example of an octahedral iridium complex containing three different monodentate phosphine ligands. All of the products obtained have been fully characterized by P-31 and H-1 n.mr.r. spectroscopy. Crystal structure analyses of (3) and of its photoisomer mer-cis-(PMe2Ph)2(PPr3i)H-cis-Cl2Ir(III) (4) have been carried out to permit comparison of the metal-ligand bonding in these complexes with that in their previously characterized, sterically less crowded, tris-PMe2Ph analogues. Summary data are as follows: (3), triclinic, P1BAR, a 13.414(1), b 12.062(1), c 9.077(1) angstrom, alpha 79.53(1), beta 88.05(1), gamma 79.47(1)-degrees [T 158+/-3 K], Z 2, R 0.022, R(w) 0.032 (4822 reflections); (4), monoclinic, P2,/n, a 19.694(1), b 15.972(1), c 9.548(1) angstrom, beta 101.45(1)-degrees (T 293+/-2 K), Z 4, R 0.026, R(w) 0.032 (5476 reflections). Both molecules exhibit distorted octahedral coordination of the metal atom and appreciably greater steric strain than in their (PMe2Ph)3HCl2Ir(III) analogues. Metal-ligand distances to the mutually trans PMe2Ph and PPr3i ligands are 2.322(1) and 2.372(1) angstrom, respectively, for (3), and 2.359(1) and 2.406(1) angstrom for (4), and suggest that the thermodynamically favoured cis-dichloro isomer (4) is the more strained. The preparations of the complexes (PCy3)2H2Cl2Ir(IV) (1a) and (PCY3)2H2Br2Ir(IV) (1b) (Cy = cyclohexyl), and their reactions with the same phosphines as used with (1), are also reported.