X-RAY CRYSTAL-STRUCTURE AND P-31 NMR SOLUTION STUDIES OF [IR2(1,8-DIISOCYANO-PARA-MENTHANE)4(PPH3)AU(PPH3)](PF6)3 - OBSERVATION OF PARTIAL SITE PREFERENCE IN THE FORMATION OF OUTSIDE AG AND AU ADDUCTS

The reaction of [M(PPh3)2](PF6) (M = Ag, Au) with [Ir2(dimen)4](PF6)2 leads to the formation of heteronuclear complexes of the general formula [Ir2(dimen)4(PPh3)M(PPh3)](PF6)3. Recrystallization of the Au complex from CH3CN/ether solution afforded crystals of [Ir2(dimen)4(PPh3)Au(PPh3)](PF6)3-CH3CN (AuIr2C86H105Fi8N9P5) that were the subject of an X-ray crystal structure characterization. The complex crystallizes in the monoclinic space group Cc (No. 9) with Z = 4; a = 24.79 (2), b = 15.792 (6), c = 23.307 (6) Å; ° = 94.15 (4)°; V = 9102 Å3. At convergence, R = 0.055 and Rw = 0.064 for 6382 observed reflections. The crystal contains tripositive cations with a Au(PPh3)+ unit occupying one of the [Ir2(dimen)4]2+ axial sites and a PPh3 in the second axial position. The PPH3-Ir2-Au(PPh3) moiety features a two-electron two-center Ir-Au bond with a Ir-Au distance of 2.607 (2) Å. Au-P and Ir-P bond distances in the structure are 2.199 (7) and 2.482 (7) Å, respectively. The Ir(CNR)4 planes are nearly staggered with a twist angle of 39°. The Ir-Ir separation is 2.986 (2) Å.From 31P{1H} NMR solution studies and homonuclear 31P{1H}δ/J-resolved NMR spectroscopy, a nonstatistical distribution of five out of six different geometric isomers is present in CH2C12 solutions of both the Ag+ and Au+ complexes. © 1990, American Chemical Society. All rights reserved.