TY - JOUR
T1 - Mixed-metal cluster chemistry. 22. Synthesis and crystallographic, electrochemical, and theoretical studies of alkyne-coordinated group 6-iridium clusters linked by phenyleneethynylene groups
AU - Lucas, Nigel T.
AU - Notaras, Eleni G.A.
AU - Petrie, Simon
AU - Stranger, Robert
AU - Humphrey, Mark G.
PY - 2003/2/17
Y1 - 2003/2/17
N2 - Reaction between the tetrahedral cluster compound Mo2Ir2(CO)10(η5-C5 H4Me)2 (1) and 1-iodo-4-(oct-1′-ynyl)benzene afforded the pseudooctahedral cluster Mo2Ir2 {μ4-η2-Me(CH2)5 C2-4-C6 H4I}(CO)8 (η5-C5H4Me)2 (7). Similar reactions of 1 and W2Ir2(CO)10 (η5-C5H4Me)2 (2) with di- and triynes afforded the related mono-, di-, and tricluster compounds [M2Ir2(CO)8(η5 -C5H4Me)2]3{μ12 -η6-Me(CH2)5C2-4-C6 H4C2C6H4-4-C2 (CH2)5Me} (M = Mo (12), W (14)), [W2Ir2(CO)8(η5-C5 H4Me)2]2 {μ8-η4 -Me(CH2)5C2-4-C6H4 C2C6H4-4-C≡C(CH2) 5Me} (13), Mo2Ir2{μ4 -η2-Me(CH2)5C2C6 H3-3,5-[C≡C(CH2)5Me]2} (CO)8(η5-C5H4Me)2 (15), and [Mo2Ir2(CO)8(η5 -C5H4Me)2]2-{μ8 -η4-[Me(CH2)5C2]2-1, 3-C6H3-5-C≡C(CH2)5Me} (16). Compound 13 corresponds to the 1,2-dicluster adduct of the linear triyne Me(CH2)5C≡C-4-C6H4 C≡C-4-C6H4 C≡C(CH2)5Me. No 1,3-dicluster isomer was isolated from direct reaction, but the related molybdenum-containing 1,3-dicluster isomer was prepared by exploiting organic reaction chemistry on precoordinated functionalized alkyne ligands. Thus, Sonogashira coupling of 7 with Me3SiC≡CH and subsequent desilylation afforded Mo2Ir2{μ4 -η2-Me(CH2)5C2-4-C6 H4C≡CR}(CO)8(η5-C5 H4Me)2 (R = SiMe3 (8), H (9)). Sonogashira coupling of 7 and 9 gave the 1,3-isomer [Mo2Ir2 (CO)8(η5-C5 H4Me)2]2 {μ8-η4-Me (CH2)5C2-4-C6H4 C≡CC6H4-4-C2 (CH2)5Me} (18), as well as the homocoupling product [Mo2Ir2(CO)8(η5 -C5H4Me)2]2 {μ8 -η4-Me(CH2)5C2-4-C6 H4C≡CC ≡CC6H4-4-C2 (CH2)5Me} (19); the identity of the latter was confirmed by a single-crystal X-ray diffraction study. Cyclic voltammetric scans for 12-14, 18, and 19 all show a reversible/quasi-reversible oxidation followed by an irreversible oxidation process. Compounds 18 and 19 (in which clusters are linked by long unsaturated bridges) exhibit one irreversible reduction process, whereas 12-14 (in which n cluster cores are linked by a phenylene unit) show n irreversible reduction processes. Density functional calculations indicate that oxidation and reduction both proceed with retention of the pseudooctahedral core geometry but that loss of a carbonyl ligand concomitant with two-electron reduction is energetically accessible, suggesting that this accounts for the irreversibility of the reduction step.
AB - Reaction between the tetrahedral cluster compound Mo2Ir2(CO)10(η5-C5 H4Me)2 (1) and 1-iodo-4-(oct-1′-ynyl)benzene afforded the pseudooctahedral cluster Mo2Ir2 {μ4-η2-Me(CH2)5 C2-4-C6 H4I}(CO)8 (η5-C5H4Me)2 (7). Similar reactions of 1 and W2Ir2(CO)10 (η5-C5H4Me)2 (2) with di- and triynes afforded the related mono-, di-, and tricluster compounds [M2Ir2(CO)8(η5 -C5H4Me)2]3{μ12 -η6-Me(CH2)5C2-4-C6 H4C2C6H4-4-C2 (CH2)5Me} (M = Mo (12), W (14)), [W2Ir2(CO)8(η5-C5 H4Me)2]2 {μ8-η4 -Me(CH2)5C2-4-C6H4 C2C6H4-4-C≡C(CH2) 5Me} (13), Mo2Ir2{μ4 -η2-Me(CH2)5C2C6 H3-3,5-[C≡C(CH2)5Me]2} (CO)8(η5-C5H4Me)2 (15), and [Mo2Ir2(CO)8(η5 -C5H4Me)2]2-{μ8 -η4-[Me(CH2)5C2]2-1, 3-C6H3-5-C≡C(CH2)5Me} (16). Compound 13 corresponds to the 1,2-dicluster adduct of the linear triyne Me(CH2)5C≡C-4-C6H4 C≡C-4-C6H4 C≡C(CH2)5Me. No 1,3-dicluster isomer was isolated from direct reaction, but the related molybdenum-containing 1,3-dicluster isomer was prepared by exploiting organic reaction chemistry on precoordinated functionalized alkyne ligands. Thus, Sonogashira coupling of 7 with Me3SiC≡CH and subsequent desilylation afforded Mo2Ir2{μ4 -η2-Me(CH2)5C2-4-C6 H4C≡CR}(CO)8(η5-C5 H4Me)2 (R = SiMe3 (8), H (9)). Sonogashira coupling of 7 and 9 gave the 1,3-isomer [Mo2Ir2 (CO)8(η5-C5 H4Me)2]2 {μ8-η4-Me (CH2)5C2-4-C6H4 C≡CC6H4-4-C2 (CH2)5Me} (18), as well as the homocoupling product [Mo2Ir2(CO)8(η5 -C5H4Me)2]2 {μ8 -η4-Me(CH2)5C2-4-C6 H4C≡CC ≡CC6H4-4-C2 (CH2)5Me} (19); the identity of the latter was confirmed by a single-crystal X-ray diffraction study. Cyclic voltammetric scans for 12-14, 18, and 19 all show a reversible/quasi-reversible oxidation followed by an irreversible oxidation process. Compounds 18 and 19 (in which clusters are linked by long unsaturated bridges) exhibit one irreversible reduction process, whereas 12-14 (in which n cluster cores are linked by a phenylene unit) show n irreversible reduction processes. Density functional calculations indicate that oxidation and reduction both proceed with retention of the pseudooctahedral core geometry but that loss of a carbonyl ligand concomitant with two-electron reduction is energetically accessible, suggesting that this accounts for the irreversibility of the reduction step.
UR - http://www.scopus.com/inward/record.url?scp=0037450860&partnerID=8YFLogxK
U2 - 10.1021/om020910k
DO - 10.1021/om020910k
M3 - Article
SN - 0276-7333
VL - 22
SP - 708
EP - 721
JO - Organometallics
JF - Organometallics
IS - 4
ER -