Synthesis And Structures of Di- And Trinuclear Di-terf-butylphosphido And Di- Tert -butylarsenido Complexes of Iridium: X-ray Crystal Structures of [ir(m-f-bu₂e)(co)₂]₂(e = P, As), [ir(f-bu₂ph)(co)]₂(ai-h)(_m-f-bu₂p), [ir(f-bu₂ph)(co)(m-h)]₂(h)(_m-f-bu₂p), And Ir₃(ai-f-bu₂p)₃(co)₅

Reaction of Li-f-Bu₂P with [Ir(CO)₃Cl]„ in THF at -78 °C yields deep red [Ir(fi-f-Bu₂P)(CO)₂]₂(1) in ca. 35% yield. This complex has a planar central Ir₂P₂ core with an Ir-Ir double bond (Ir-Ir = 2.545 (1) A). Each Ir atom bears two CO units and has a distorted tetrahedral geometry. The /-Bu₂As analogue of 1, yellow [Ir(ji-f-Bu₂As)(CO)₂]₂(2), is produced in 12% yield in the reaction of Ir₄(CO)₁₂with /-Bu₂AsH in refluxing toluene. In contrast to 1, 2 has two Ir(I) atoms that have planar coordination geometries and no Ir-Ir bond (Ir-Ir = 3.89 (1) A). Reaction of Ir₄(CO)₁₂with ?-Bu₂PH in toluene under reflux yields the dinuclear hydrido- and phosphido-bridged complex [Ir(f-Bu₂PH)(CO)]₂0t-H)(M-f-Bu₂P) (4) (52%) as well as the trinuclear cluster Ir₃(ju-f-Bu₂P)₃(CO)₅(3) (24%). 3 consists of an Ir₃ triangle that bears one f-Bu₂P unit severely distorted from the Ir₃ plane and bridges two Ir atoms that bear two CO units each. The third Ir atom has only one CO group. The two other p-t-Bu₂P units lie much closer to the Ir₃ plane. 4 has two roughly planar Ir atoms (Ir-Ir = 2.901 (1) A) bridged by H and f-Bu₂P. The terminal f-Bu₂PH groups lie cis with respect to the Ir-Ir interaction and are trans to the ix-t-Bu₂P” unit. They occupy the same side of the molecule as the m-hatom. 4 reacts reversibly with H₂ (1 atm) in both solution and the solid state to give [Ir(f-Bu₂PH)(CO)(M-H)]₂-(h)(m-t-bu₂P) (5), which contains two bridging hydrides and one terminal hydride. 4 reacts with CO (1 atm) to replace one f-Bu₂PH ligand and give (f-Bu₂PH)(CO)Ir(M-H)(M-f-Bu₂P)Ir(CO)₂ (6), The structures of 1–5 have been determined by sin-gle-crystal X-ray diffraction studies. CAD-4 crystal data: (Mo Ka) (graphite monochromator) - 0.71073 A. Crystal data for 1: C₂₀H₃₆Ir₂O₄P₂, M_T 768.4, orthorhombic, Pnnm (No. 58), a = 8.535 (1) A, b = 11.990 (1) A, c = 12.574 (2) A, V= 1286.8 (5) A³, Z = 2, Z)_calcd * 2.03 g cm”³, m(moka) = 208.7 cm”¹, final R = 0.0301 (R_w= 0.0382) from 954 observed (/ > 3<r(/» reflections (1331 measured). Crystal data for 2: C₂₀H₃₆As₂Ir₂O₄, M_x 874.6, monoclinic, C2/m (No. 12), a = 12.009 (2) A, b = 11.214(2) A, c = 11.087 (2) A, (3 = 120.26 (2)°, V= 1289.6 (5) A³, Z = 2, Dealcd = 2.25 g cm”³, fx(Mo Ka) = 128.34 cm”¹, final R = 0.0392 (R_w = 0.0589) from 978 observed (/ > 3tr(/)) reflections (1246 measured). Crystal data for 3: C₂₉H₅₄Ir₃0₅P₃, M_t 1151.6, monoclinic P2\\\\\\\\/c (No. 14), a = 19.753 (6) A, b = 11.796 (5) k,c- 17.116 (6) A, 0 = 113.11 (9)°, V= 3668.1 (5) A³, Z = 4, Dcajod = 2.01 g cm^-3, fi(Mo Ka) = 112.65 cm”¹, final R ~ 0.039, R_w= 0.048 from 1782 observed reflections (/> 3cr(/)), 2701 measured. Crystal data for 4: C₃₂H₇₁Ir₂0₂P₃, Af_r965.24, orthorhombic, P2₁2₁2₁ (No. 19), a - 12.257 (9) A, b = 15.224 (4) A, c = 22.241 (8) A, V = 4150.0 (5) A³, Z = 4, D_M= 1.545 g cm”³, m(moKa) = 65.20 cm”¹, final R = 0.0713 (R_w= 0.0861) from 1833 observed (/ > 3tr(/)) reflections (4104 measured). Crystal data for 5: C₂₆H₆₁Ir₂0₂P₃, M_v 883.10, monoclinic Pljc (No. 14), a = 12.341 (2) A, b = 12.313 (4) A, c = 22.597 (9) A, 0 = 92.77 (2)°, V= 3429.9 (5) A³, Z = 4, Dcalcd = 1.710 g cm”³, it(Mo Ka) = 78.80 cm”¹, final R = 0.0592 (/?_w= 0.0711) from 3436 observed reflections (/ > 3cr(/)), 5346 measured.