Substitution and fragmentation reactions of dibromododecacarbonyltriosmium with phosphines. Structure of dibromodecacarbonylbis(trimethyl phosphite)triosmium

Bromination of Os3(CO)11(EPh3) (E = P, Sb): Unexpected Formation of a Tandem Donor−Acceptor Metal Chain

“…Compounds 2 and 3 are unique pairs of isomers; isomers 3 are structurally similar to the Os 3 (CO) 10 (PR 3 ) 2 (Br) 2 chains reported earlier by Angelici et al Isomers 2 contain two donor−acceptor metal−metal bonds in tandem, and 2a and 2b are the only homonuclear examples yet reported. In the earlier reports on this class of compounds, it was noted that the metal−metal bond lengths were longer than comparable nondative bonds in closed polyhedra of metal atoms but in the usual range for linear metallic chains .…”

Formation of [Os3(CO)10(EPh3)2(μ-Br)]+ (E = P, As) by Bromination: First Direct Evidence for the Bromonium Mechanism in Cluster Chemistry

“…We were able to verify that 2a did not react directly with bromine, but it reacted fairly rapidly with Et 4 NBr at room temperature to give a similar mixture of products as in the reaction of 1 with excess Br 2 . Interestingly, the spectroscopic evidence showed that the expected initial product from this reaction, the trimetallic chain compound Os 3 (CO) 10 (PPh 3 ) 2 Br 2 obtained by Angelici et al from the reaction of Os 3 (CO) 12 Br 2 with PPh 3 , was not formed. Instead, it appears that the attack of Br - on the cationic bromonium cluster led to rapid cluster fragmentation.…”

“…The mechanism by which triosmium clusters undergo halogenation reactions has been of recent interest. Essentially, the two major possibilities are via a radical mechanism or a bromonium intermediate . It has recently been shown that the reaction of Br + with the parent carbonyl cluster Os 3 (CO) 12 gave the bromonium cluster [Os 3 (CO) 12 (μ-Br)] + , and it was also demonstrated that this cluster was not the intermediate involved in the direct bromination reaction .…”

Unexpected Reactions of 2,5-Dimethylthiophene (2,5-Me2T) in Cp*Ir(η5-2,5-Me2T)2+, Cp*Ir(η4-2,5-Me2T), and Cp*Ir(C,S-2,5-Me2T) with Cobaltocene

“…These results suggest that the reaction of 2 with Cp 2 Co occurs by initial isomerization to the more stable 3 , which reacts with Cp 2 Co to give 5 . Other reactions of 2 and 3 , e.g., with Lewis acids, ,, bases, and oxidizing agents, also give the same products. Complex 5 is soluble in both polar and nonpolar organic solvents.…”

“…Elemental analyses and the mass spectrum confirm the composition of 4 , and an X-ray diffraction study establishes its structure as that shown in eq 2. The structure (Figure ) is related to those of Cp*Ir(η 4 -SC 3 H 2 MeC(O)Me) ( A ) and Cp*Rh(η 4 -SC 3 Me 3 C(O)Me) ( B ). , Although there is disorder in the η 4 -2,5-Me 2 T·C 5 H 4 ligand, the C−C bond distances suggest that double bonds are located at C(5)−C(14) (1.37(3) Å), C(15)−C(16) (1.34(4)), and C(17)−C(18) (1.30(3)), and single bonds are at C(4)−C(5) (1.48(3) Å), C(14)−C(15) (1.50(3)), C(16)−C(17) (1.49(4)), and C(14)−C(18) (1.46(3)) . The conjugated triene system is conjugated with the allyl portion of the ligand.…”