The interaction of mer-IrCI,(SEt,),with Mg(mes),(thf), [mes = mesityl (2,4,6-trimethylphenyl), thf = tetrahydrofuran] in Et,O-thf gives trans-Ir(mes),(SEt,),1. With PMe, 1 gives trans-Ir(mes),( PMe,), 2; both compounds are paramagnetic. With NO, 2 reacts to form the formally iridium(t1t) complex Ir(mes),(NO)(PMe,), 4 that has a bent lrNO group, while H, gives the known hydride IrH,(PMe,),. With CO 1 forms the square iridium(i) complex Ir(mes) (CO), (SEt,) 3. The trans-square planar molecules of compound 1 lie on centres of symmetry; Ir-S and Ir-C 2.298(4) and 2.09(1) A, respectively, with a unique S-lr-C angle of 88.2(3)". Molecules of 2 are also trans square planar, but lie in general positions; Ir-P 2.302(4), 2.305(4) A, Ir-C 2.097(9), 2.1 12(9) A and P-lr-C 89.6(3)-90.5(3)". The crystal structure of 4 contains t w o crystallographically independent molecules, both of which lie on two-fold axes, coincident with the Ir-N bond. The geometry is slightly distorted square pyramidal; N-lr-P and N-lr-C 91.7(2) ( x 2) and 99.1 (3), 99.3(3)", respectively. The lr-N, Ir-P and Ir-C bond lengths are 1.90(1), 1.91 (1 ); 2.324(5), 2.328(4); and 2.1 86(9), 2.1 82(12) A, respectively.The bent Ir-N-0 system [133.7(10) and 133.4( 8)"] is disordered over two sites related by the twofold axes, but in a single molecule is fixed in one position and believed to associate, via 0 .=. P interaction, with the phosphorus atom of one phosphine.
