Mixed-metal cluster chemistry IX: alkylarylphosphine derivatives of [CpWIr3(CO)11] and X-ray crystal structure of [CpWIr3(μ-CO)3(CO)7(PMe2Ph)]

Mixed-Metal Cluster Chemistry. 11.1Reactions of Tungsten−Iridium Clusters with Terminal Alkynes and Tungsten Acetylides: X-ray Crystal Structures of Cp2W2Ir2(μ4-η2-HC2Ph)(μ-CO)4(CO)4and Cp2W2Ir3(μ4-η2-C2C6H4Me-4)(μ-CO)(CO)9

“…The chemistry of mixed-metal clusters has been of enduring interest. − Mixed-metal clusters are potential precursors to supported bimetallic catalysts, the differing metals provide effective labels for ligand fluxionality studies, and the varying metals of the cluster core afford the possibility of metallo- and bond-selectivity and thus directing reactivity for a range of reagents. We have probed the last-mentioned feature utilizing phosphines and the systematically varied series of tetrahedral clusters Cp x M x Ir 4 - x (CO) 12 - x ( x = 0−2, M = W, Mo) − noting enhanced reactivity and differing site-selectivity and carbonyl fluxionality upon heterometal incorporation into the “parent” cluster Ir 4 (CO) 12 .…”

Mixed-metal cluster chemistry. 26 . Proclivity for “all-terminal” or “plane-of-bridging-carbonyls” ligand disposition in tungsten–triiridium clusters

“…The plane of bridging carbonyls about a WIr 2 face is in contrast to the crystallographically-reported all-terminal structures of analogous clusters with methylcyclopentadienyl [15] and cyclopentadienyl [12,16] ligands and a carbonyl substitution derivative of the former with two CNC 6 H 3 Me 2 -2,6 ligands [9], but a plane of bridging carbonyls about a WIr 2 face is also seen in the structure of the cyclopentadienyl-containing derivative where one of the carbonyl groups is replaced by PPh 3 [5] or P(OMe) 3 [17], or two of the carbonyls are replaced by P(OPh) 3 [7], or the methylcyclopentadienyl derivative where one carbonyl is replaced by PMe 3 [10], ligand replacements that increase electron donation to the cluster. Note that a plane of bridging carbonyls about the Ir 3 face is seen in the structures of cyclopentadienyl-containing derivatives where one of the carbonyls is replaced by PMe 3 [5] or P(OMe) 3 [8], or where two of the carbonyls are replaced by an Ir-Ir bridging bidentate diphosphine (bis(diphenylphosphino)methane, dppm; 1,2-bis(diphenylphosphino)ethane, dppe; bis(diphenylphosphino)acetylene, dppa) [4]. In all instances, a plane of bridging carbonyls is observed upon introduction of a sufficiently strongly electron-donating ligand.…”

“…Selected bond lengths and angles are collected in [12] and WIr 3 (l-CO) 3 (CO) 7 (PMe 2 Ph)(g-C 5 H 5 ) (Ir-Ir av ¼ 2.745, W-Ir av ¼ 2.854 A A) [8] reveals that increasing electron density at the cluster core by permethylation of the cyclopentadienyl ligand or by substitution of PMe 2 Ph for a carbonyl both result in increases in core bond lengths. As with previous structural determinations for this class of cluster, core angles are ca 60°as expected, with those at the sterically-more-congested tungsten ca 56°.…”

“…We have previously reported fluxionality studies of WIr 3 (l-CO) 3 (CO) 7 (L)(g-C 5 H 5 ) (L ¼ PPh 3 , PMe 3 [23]), WIr 3 (CO) 10 (CNBu t )(g-C 5 H 5 ) [9], and WIr 3 (l-CO) 3 (CO) 6 (L 2 )(g-C 5 H 5 ) (L 2 ¼ dppm, dppe [8]). Whereas the isonitrile-containing cluster was highly fluxional (cooling to 143 K revealed broadening of the 13 C NMR resonances only), low temperature limiting spectra of the phosphine-containing clusters could be obtained, the fluxionality being shown to proceed via the merry-goround process as a key step.…”

“…We have prepared a significant number of phosphine and isonitrile derivatives of these clusters [4][5][6][7][8][9][10][11] and, while all crystallographically-confirmed molybdenum-containing Journal of Organometallic Chemistry 689 (2004) 50-57 www.elsevier.com/locate/jorganchem clusters possess a MIr 2 plane of bridging carbonyls, crystallographically-verified tungsten-containing examples possess all-terminal or plane-of-bridging-carbonyls configurations, depending on the ligand set. We report herein the synthesis and crystallographic characterization of WIr 3 (l-CO) 3 (CO) 8 (g-C 5 Me 5 ), for which permethylation of the cyclopentadienyl ligand is sufficient to modify the carbonyl disposition in the ground state structure, together with a DFT study exploring the proclivity of these mixed group 6-iridium tetrahedral clusters to adopt the two carbonyl ligand arrangements, and studies of ligand fluxionality at WIr 3 (CO) 11 (g-C 5 H 5 ) and the related tetrahedral cluster W 2 Ir 2 (CO) 10 (g-C 5 H 5 ) 2 .…”