Jump to main content
Jump to site search

Issue 16, 2015
Previous Article Next Article

Phosphine, isocyanide, and alkyne reactivity at pentanuclear molybdenum/tungsten–iridium clusters

Author affiliations

Abstract

The trigonal bipyramidal clusters M2Ir3(μ-CO)3(CO)65-C5H5)25-C5Me4R) (M = Mo, R = Me 1a, R = H; M = W, R = Me, H) reacted with isocyanides to give ligand substitution products M2Ir3(μ-CO)3(CO)5(CNR′)(η5-C5H5)25-C5Me4R) (M = Mo, R = Me, R′ = C6H3Me2-2,6 3a; M = Mo, R = Me, R′ = tBu 3b), in which core geometry and metal atom locations are maintained, whereas reactions with PPh3 afforded M2Ir3(μ-CO)4(CO)4(PPh3)(η5-C5H5)25-C5Me4R) (M = Mo, R = Me 4a, H 4c; M = W, R = Me 4b, H), with retention of core geometry but with effective site-exchange of the precursors’ apical Mo/W with an equatorial Ir. Similar treatment of trigonal bipyramidal MIr4(μ-CO)3(CO)75-C5H5)(η5-C5Me5) (M = Mo 2a, W 2b) with PPh3 afforded the mono-substitution products MIr4(μ-CO)3(CO)6(PPh3)(η5-C5H5)(η5-C5Me5) (M = Mo 5a; M = W 5b), and further reaction of the molybdenum example 5a with excess PPh3 afforded the bis-substituted cluster MoIr43-CO)2(μ-CO)2(CO)4(PPh3)25-C5H5)(η5-C5Me5) (6). Reaction of 1a with diphenylacetylene proceeded with alkyne coordination and C[triple bond, length as m-dash]C cleavage, affording Mo2Ir34–η2-PhC2Ph)(μ3-CPh)2(CO)45-C5H5)25-C5Me5) (7a) together with an isomer. Reactions of 2a and 2b with PhC[triple bond, length as m-dash]CR afforded MIr43–η2-PhC2R)(μ3-CO)2(CO)65-C5H5)(η5-C5Me5) (M = Mo, R = Ph 8a; M = W, R = Ph 8b, H; M = W, R = C6H4(C2Ph)-3 9a, C6H4(C2Ph)-4), while addition of 0.5 equivalents of the diynes 1,3-C6H4(C2Ph)2 and 1,4-C6H4(C2Ph)2 to WIr4(μ-CO)3(CO)75-C5H5)(η5-C5Me5) gave the linked clusters [WIr4(CO)85-C5H5)(η5-C5Me5)]26–η4-PhC2C6H4(C2Ph)-X) (X = 3, 4). The structures of 3a, 4a–4c, 5b, 6, 7a, 8a, 8b and 9a were determined by single-crystal X-ray diffraction studies, establishing the core isomerization of 4, the site selectivity for ligand substitution in 3–6, the alkyne C[triple bond, length as m-dash]C dismutation in 7, and the site of alkyne coordination in 7–9. For clusters 3–6, ease of oxidation increases on increasing donor strength of ligand, increasing extent of ligand substitution, replacing Mo by W, and decreasing core Ir content, the Ir-rich clusters 5 and 6 being the most reversible. For clusters 7–9, ease of oxidation diminishes on replacing Mo by W, increasing the Ir content, and proceeding from mono-yne to diyne, although the latter two changes are small. In situ UV-vis-near-IR spectroelectrochemical studies of the (electrochemically reversible) reduction process of 8b were undertaken, the spectra becoming increasingly broad and featureless following reduction. The incorporation of isocyanides, phosphines, or alkyne residues in these pentanuclear clusters all result in an increased ease of oxidation and decreased ease of reduction, and thereby tune the electron richness of the clusters.

Graphical abstract: Phosphine, isocyanide, and alkyne reactivity at pentanuclear molybdenum/tungsten–iridium clusters

Back to tab navigation

Supplementary files

Article information


Submitted
05 Feb 2015
Accepted
11 Mar 2015
First published
13 Mar 2015

Dalton Trans., 2015,44, 7292-7304
Article type
Paper

Phosphine, isocyanide, and alkyne reactivity at pentanuclear molybdenum/tungsten–iridium clusters

P. V. Simpson, M. D. Randles, V. Gupta, J. Fu, G. J. Moxey, T. Schwich, M. Morshedi, M. P. Cifuentes and M. G. Humphrey, Dalton Trans., 2015, 44, 7292 DOI: 10.1039/C5DT00525F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.


Social activity

Search articles by author

Spotlight

Advertisements