Do paramagnetic platinum metal hydrides really exist? A reinvestigation of the synthesis and magnetochemical properties of Ir(H)x(Cl)2(P-i-Pr3)2 (1). Syntheses and crystal structure determinations of trans-Ir(H) (Cl)2(CO) (P-i-Pr3)2 (2), cis-Ir(H)(Cl)2(CO)(P-i-Pr3)2 (4) and trans-Ir(Cl) (CO)

As further studies of our samples of Ir(H)(x)(Cl)(2)(P-i-Pr-3)(2) (1) led us to suspect that their paramagnetism was due to cooperative surface phenomena we decided a through reinvestigation of the system 1. The reaction of ethanolic solution of H-2[IrCl6] with P-i-Pr-3, in the presence of concentrated HCl, gave compound 1 in 70% yield. The magnetic moment of this sample does not exceed 0.5 BM. Washing the sample with water or with organic solvents and crushing it with a platinum spatula gave an increase in mu(eff). H-1 spin-lattice relaxation (T-1) measurement on solid samples of 1 at different mu(eff) values (0.5, 1.5 BM) suggest that the paramagnetism is due to cooperative surface phenomena and the bulk of 1 is diamagnetic. As found in the complex prepared starting from (NH4)(2)[IrCl6], the above sample shows two weak bands at 2116 and 2002 cm(-1). These, however, are not due to v(lr-H) but to the presence of small amounts of two carbonyl complexes. By bubbling CO gas into an ethanolic solution of 1, the trans-Ir(H) (Cl)(2)(CO) (P-i-Pr-3)(2) (2) compound is obtained. This carbonyl complex shows an extremely strong band at 2002 cm(-1). Trans-2, both in solution and in the solid state, isomerizes into cis-Ir(H) (Cl)(2)(CO) (P-i-Pr-3)(2) (4). By reacting an ethanolic solution of H-2[IrCl6] with P-i-Pr-3, without addition of HCl, a mixture of 1 and another complex, trans-Ir(Cl) (CO) (P-i-Pr-3)(2) (5), is obtained, characterized by a strong band at 1930 cm(-1). Subsequent refluxing of the mother liquor of the above synthesis gave pure 5. This new complex is responsible for the very strong band at 1930 cm(-1). Thus, the v(Ir-H) of complex 1 does not occur in the usual region, and may be masked by the H2O absorption at ca. 1700-1600 cm(-1). Crystallographic data: for trans-2 (at 298 K), a=15.515(6), b=8.633(4), c=19.521(9) Angstrom, beta=104.34(3)degrees in space group Ia (Z=4). For cis-4 (at 298 K), a=16.488(1), b=27.118(2), c=11.384(1) A in space group Pbca (Z=8). For trans-5 (at 298 K), a=8.152(3), b=8.918(3), c=16.639(6) Angstrom, beta=93.50(3)degrees in space group P2(1)/c (Z=2).