Mixed-metal cluster chemistry. 35. Syntheses and structural studies of Mo 3 Ir 3 (μ 3 -O)(μ-CO) 3 (CO) 8 ( η 5 -C 5 H 5 ) 3 , Mo 4 Ir 4 (μ-CO) 4 (CO) 9 ( η 5 -C 5 H 5 ) 4 and Mo 3 Ir 5 (μ-CO) 3 (Cl)(CO) 6 ( η 5 -C 5 H 5 ) 3 ( η 5 -C 5 HMe 4 )

Abstract

a b s t r a c tThe reaction of Ir(CO) 2 (h 5 -C 5 HMe 4 ) with Mo 2 Ir 2 (m-CO) 3 (CO) 7 (h 5 -C 5 H 5 ) 2 affords a complex mixture from which three structurally-characterized products were obtained following thin-layer chromatography. Mo 3 Ir 3 (m 3 -O)(m-CO) 3 (CO) 8 (h 5 -C 5 H 5 ) 3 (1) is Effective Atomic Number (EAN) Rule EAN-precise and possesses an edge-bridged trigonal bipyramidal core with the face-capping oxo ligand located in a Mo 2 Ir 2 butterfly cleft in the structure. Mo 4 Ir 4 (m-CO) 4 (CO) 9 (h 5 -C 5 H 5 ) 4 (2) possesses four electrons less than the Polyhedral Skeletal Electron Pair Theory (PSEPT)-expected count for a capped pentagonal bipyramidal cluster with the apical atoms within bonding distance. Mo 3 Ir 5 (m-CO) 3 (Cl)(CO) 6 (h 5 -C 5 H 5 ) 3 (h 5 -C 5 HMe 4 ) (3) possesses a tetracapped tetrahedral core and has six electrons less than the PSEPT-predicted electron count. The core geometries exhibited by clusters 2 and 3 have previously only been observed for clusters including significant group 10 and group 11 metal content. IntroductionTransition metal clusters occupy the regime between monometallic complexes and nanocrystalline materials. The challenge of rationalizing the stability of such species has spurred the development of theory, one key example of which is the polyhedral skeletal electron-pair theory (PSEPT, also known as the WadeMingos rules) [1,2]. The field of transition metal carbonyl clusters increased explosively following the advent of routine single-crystal X-ray diffraction studies that were needed to conclusively establish the identity of these clusters [3], to the extent that the field can now be considered mature. Notwithstanding the now-well-established nature of this area, it is still the case that mixed-metal clusters incorporating disparate metals remain comparatively underexploited, despite the practical advantages that locating two differing metals in the one cluster may afford, such as enhancing the prospects of controlling chemistry via metal-or bond-selectivity for substrates, labelling vertices to establish ligand fluxionality pathways, and controlling the spatial disposition and connectivity of heterobimetallic species in subsequent catalytic processes [4].We have reported comprehensive studies of the syntheses and chemistry of tetranuclear mixed molybdenum/tungsteneiridium carbonyl clusters [5] and have recently extended these studies to embrace pentanuclear examples [6]. On modifying the reaction conditions employed for the syntheses of one of the pentanuclear clusters, we observed the unexpected formation of several highernuclearity species, the syntheses and structural characterization of which are reported herein.