Mixed-Metal Cluster Chemistry. 23. Synthesis and Crystallographic and Electrochemical Studies of Alkyne-Coordinated Group 6−Iridium Clusters Linked by Heterocyclic Groups

Abstract

Reaction between the tetrahedral cluster compound Mo 2 Ir 2 (CO) 10 (η 5 -C 5 H 4 Me) 2 (1) and 2-iodo-5-(oct-1′-ynyl)thiophene afforded the pseudooctahedral cluster Mo 2 Ir 2 {µ 4 -η 2 -Me-(CH 2 ) 5 C 2 -5-C 4 H 2 S-2-I}(CO) 8 (η 5 -C 5 H 4 Me) 2 ( 17) by formal insertion of the alkyne CtC group into the Mo-Mo bond. Similar reactions of 1 or W 2 Ir 2 (CO) 10 (η 5 -C 5 H 4 Me) 2 (2) with heterocyclic di-or triynes afforded the related mono-, di-, or tricluster compounds [M 2 Ir 2 (CO) 8 (ηCompounds 27 and 29 correspond to the 1,2-dicluster adducts of the linear triyne Me(CH 2 ) 5 CtC-5-C 4 H 2 S-2-CtC-2-C 4 H 2 S-5-CtC(CH 2 ) 5 Me. No 1,3-dicluster isomer was isolated from direct reaction, but the molybdenum-containing 1,3-dicluster isomer was prepared by exploiting organic reaction chemistry on precoordinated functionalized alkyne ligands. Thus, Sonogashira coupling of 17 with trimethylsilylacetylene and subsequent desilylation gave Mo 2 Ir 2 {µ 4 -η 2 -Me(CH 2 ) 5 C 2 -5-C 4 H 2 S-2-CtCR}(CO) 8 (η 5 -C 5 H 4 Me) 2 [R ) SiMe 3 (18), H ( 19)]. Sonogashira coupling of 17 and 19 gave the 1,3-isomer [Mo 2 Ir 2 (CO) 8 (η 5 -C 5 H 4 -Me) 2 ] 2 {µ 8 -η 4 -Me(CH 2 ) 5 C 2 -2-C 4 H 2 S-5-CtC-2-C 4 H 2 S-5-C 2 (CH 2 ) 5 Me} (32), as well as the homocoupling product [Mo 2 Ir 2 (CO) 8 (η 5 -C 5 H 4 Me) 2 ] 2 {µ 8 -η 4 -Me(CH 2 ) 5 C 2 -2-C 4 H 2 S-5-CtCCtC-2-C 4 H 2 S-5-C 2 (CH 2 ) 5 Me} (33). The identities of 21, 29, and 31 were confirmed by single-crystal X-ray diffraction studies. Cyclic voltammetric scans for these complexes all show a reversible/ quasi-reversible oxidation followed by an irreversible oxidation process. Dicluster compounds linked by one heterocycle, and tricluster compounds, show two reduction processes, whereas dicluster compounds with longer bridges reveal only one reduction process.

Ruthenium cluster chemistry: Monodentate bis(diphenylphosphino)acetylene-ligated cluster modules in chain and dendrimer formation

“…Elemental microanalyses were carried out by the Microanalysis Service Unit in the Research School of Chemistry, ANU. 9 (g 1 -dppa) 3 …”

“…The first band (R f = 0.83) was identified as unreacted dppa (85 mg) by 1 H and 31 P NMR. Band 2 (R f = 0.56, red) was identified as Ru 3 (CO) 9 (g 1 -dppa) 3 (2) (80 mg, 30%). Anal.…”

“…Found: C, 60.53; H, 3.88%. C 87 H 60 O 9 P 6 Ru 3 (l-dppm)(CO) 9 (g 1 -dppa) (1) (105.7 mg, 0.079 mmol) were placed in a Schlenk tube and a mixture of CH 2 Cl 2 /MeCN (10 mL/5 mL) was added. The resultant red mixture was stirred at room temperature for 3 days, after which time the solution was taken to dryness and subjected to TLC (11:9 CH 2 Cl 2 :petroleum spirit eluant).…”

“…We have previously reported the synthesis of Ru 3 -(CO) 9 {(Ph 2 PC 6 H 4 -4-C"C)Ru(PPh 3 ) 2 (g-C 5 H 5 )} 3 , a cluster-centered organometallic star [5], tetrametallic group 6-group 9 mixed-metal cluster-containing oligourethanes [6], and di-and tri-cluster compounds in which the mixed-metal cluster modules are linked by a variety of potentially p-delocalizable organic bridging units [7][8][9]. We report herein the synthesis of Ru 3 (CO) 9 (g 1 -dppa) 3 , which contains three monodentate dppa ligands, the single-crystal X-ray study of Ru 3 (l-dppm)(CO) 9 (g 1 -dppa), which contains one monodentate dppa ligand, and studies examining the utility of these two clusters in the construction of a tri-cluster chain and a tetra-cluster dendrimer.…”

“…We report herein the synthesis of Ru 3 (CO) 9 (g 1 -dppa) 3 , which contains three monodentate dppa ligands, the single-crystal X-ray study of Ru 3 (l-dppm)(CO) 9 (g 1 -dppa), which contains one monodentate dppa ligand, and studies examining the utility of these two clusters in the construction of a tri-cluster chain and a tetra-cluster dendrimer. …”