Alistair Usher

Synthesis and third-order nonlinear optical properties of [Mo3(μ3-S)(μ2-S2)3]4+ clusters with maleonitriledithiolate, oxalate and thiocyanate ligands

Substitution of the bromine ligands in [(n-Bu)4N]2[Mo3S7Br6] (1) by bidentate ligands such as maleonitriledithiolate (mnt) or oxalate (ox) affords the trinuclear clusters [Mo3S7(mnt)3]2− ([2]2−) and [Mo3S7(ox)3]2− ([3]2−) in moderate yields. The structures of clusters [2]2− and [3]2− have been determined by single-crystal X-ray diffraction as their tetrabutylammonium salts. Cluster 2 forms dimers by interaction of one sulfur atom of the mnt ligand with the anionic binding site of the cluster anion. The structure of 3 reveals the presence of aggregates between the anionic cluster and a Br− ion. The ESI-MS indicate that these cluster–bromine adducts are also present in solution. Electrochemical studies on complexes 1–3 show two irreversible waves associated with reductive cleavage of the disulfido bridges and one or two quasi-reversible oxidation processes for [Mo3S7(ox)3]2− or [Mo3S7(mnt)3]2−, respectively. No oxidation waves have been observed for compound 1 or for its thiocyanate derivative [(n-Bu)4N]2[Mo3S7(SCN)6] (4) within the acetonitrile solvent window. The optical limiting properties of the complexes 1–4 have been measured by the Z-scan technique employing 40 ns pulses at 523 nm. Power limiting was observed for clusters 1, 2 and 4, whereas the oxalate derivative 3 was photochemically unstable under our experimental conditions.

Mixed-metal cluster chemistry 25 ☆: Mixed ligand derivatives of MoIr3(μ-CO)3(CO)8(η-C5R5) (R=H, Me) and Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2; X-ray crystal structures of MoIr3(μ-CO)3(CO)6(PPh3)2(η-C5Me5) and Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CNBut)(CO)3(η-C5H5)2

Abstract Reactions of MoIr3(μ-CO)3(CO)8(η-C5Me5) (1) with stoichiometric amounts of the isocyanide ButNC afford the ligand substituted clusters MoIr3(μ-CO)3(CNBut)n(CO)8−n(η-C5Me5) (n=1 (2), 2 (3), 3 (4)) in fair to good yields (13–58%). In contrast, 1 reacts with PPh3 to afford a single unexpected product, namely MoIr3(μ-CO)3(CO)6(PPh3)2(η-C5Me5) (5). A single-crystal X-ray study of 5 reveals that the phosphines occupy coordination sites adjacent to the plane of bridging carbonyls in a radial–radial–axial conformation previously unobserved in structural studies of molybdenum–tri-iridium or tungsten–tri-iridium clusters. Reactions of Mo2Ir2(μ-CO)3(CO)7(η-C5H5)2 (6) with ButNC or diphenylacetylene proceed cleanly in high yield to afford Mo2Ir2(μ-CO)2(CNBut)2(CO)6(η-C5H5)2 (7) or Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CO)4(η-C5H5)2 (8), respectively; reacting 7 with diphenylacetylene or 8 with ButNC results in a more complex mixture of products from which Mo2Ir2(μ4-η2-PhC2Ph)(μ-CO)4(CNBut)(CO)3(η-C5H5)2 (9) can be isolated in low yield.

Mixed-metal cluster chemistry. 24. Isocyanide derivatives of [MoIr 3 (μ-CO) 3 (CO) 8 (η-C 5 H 5 )] and [Mo 2 Ir 2 (μ-CO) 3 (CO) 7 (η-C 5 H 5 ) 2

Abstract Reactions of MoIr 3 (μ-CO) 3 (CO) 8 (η-C 5 H 5 ) ( 1 ) with stoichiometric amounts of isocyanides afford the ligand-substituted clusters [MoIr 3 (μ-CO) 3 (CO) 8− n (L) n (η-C 5 H 5 )] (L=CNBu t , n =1 ( 3 ), 2 ( 4 ), 3 ( 5 ); L=CNC 6 H 3 Me 2 -2,6, n =1 ( 6 ), 2 ( 7 ), 3 ( 8 )) in moderate to excellent yields (13–75%). Single-crystal X-ray studies of 3 and 6 reveal that the isocyanides occupy coordination sites on an apical cluster core metal atom, a first for ligand-substituted derivatives of 1 . In contrast, reaction of Mo 2 Ir 2 (μ-CO) 3 (CO) 7 (η-C 5 H 5 ) 2 ( 2 ) with one or two equivalents of CNBu t affords Mo 2 Ir 2 (μ-CO) 2 (CNBu t ) 2 (CO) 6 (η-C 5 H 5 ) 2 ( 9 ) as the only major product. A single-crystal X-ray study of 9 reveals an unprecedented carbonyl configuration about the pseudotetrahedral cluster core.