Syntheses, Structural Characterizations, and Reactivity Studies of Half-Sandwich Cobalt, Rhodium, and Iridium Metallatricarbadecaboranyl Complexes

Abstract

The syntheses and structural characterizations of the first extensive series of Group 9 (Co, Rh, and Ir) tricarbadecaboranyl halfsandwich complexes are reported. The carbonyl complexes 1,1-(CO) 2 -2-Ph-closo-1,2,3,4-MC 3 B 7 H 9 , M = Co (1), Rh (2), and 8,8,8-(CO) 3 -9-Phnido-8,7,9,10-IrC 3 B 7 H 9 (3) were obtained by the reactions of Li + (6-Phnido-5,6,9-C 3 B 7 H 9 ) − with Co(CO) 4 I, [Rh(CO) 2 Cl] 2 , and Ir(CO) 3 Cl, respectively. Further reactions of 1, 2, and 3 with 1,2-bis(diphenylphosphino)ethane (dppe) yielded the 1,1-dppe-2-Ph-closo-1,2,3,4-MC 3 B 7 H 9 , M = Co (4), Rh (5), and 8-CO-8,8-dppe-9-Ph-nido-8,7,9,10-IrC 3 B 7 H 9 (6) derivatives with their crystallographic determinations showing that 1 and 2 contain the η 6 -2-Ph-2,3,4-C 3 B 7 H 9 1− ligand with the metallatricarbadecaboranyl cluster fragments having closo-octadecahedral geometries, while 3 has a slipped-cage η 4 -9-Ph-7,9,10-C 3 B 7 H 9 1− coordination and a nido-cluster framework. The reaction of Li + (6-Ph-nido-5,6,9-C 3 B 7 H 9 ) − with [Rh(COD)Cl] 2 and [Ir(COD)Cl] 2 produced the COD coordinated complexes 1,1-COD-2-Ph-closo-1,2,3,4-MC 3 B 7 H 9 , M = Rh (7), Ir (8), with η 6 -2-Ph-2,3,4-C 3 B 7 H 9 1− ligands and closo-cluster structures. On the other hand, slipped-cage structures with η 4 -9-Ph-7,9,10-C 3 B 7 H 9 1− coordination were achieved by the reactions of 1, 3, or 8 with an excess of the stronger donor tert-butyl isocyanide to give 8,8,8-(CN t Bu) 3 -9-Ph-nido-8,7,9,10-MC 3 B 7 H 9 , M = Co (9), Ir (10), respectively, or by the reaction of 8 with 1 equiv of tert-butyl isocyanide to give 8,8-COD-8-CN t Bu-9-Ph-nido-8,7,9,10-IrC 3 B 7 H 9 (11). Upon the reaction of 1 with diphenylacetylene, both carbonyls were displaced with subsequent alkyne cyclization to form the tetraphenylcyclobutadienyl complex 1,1-(η 4 -C 4 Ph 4 )-2-Ph-closo-1,2,3,4-CoC 3 B 7 H 9 (12). The crystalline tetramethylcyclobutadienyl derivative 1,1-(η 4 -C 4 Me 4 )-2-Ph-closo-1,2,3,4-CoC 3 B 7 H 9 (13) was synthesized by the reaction of Li + (6-Ph-nido-5,6,9-C 3 B 7 H 9 ) − with (η 4 -C 4 Me 4 )Co(CO) 2 I, and its crystallographic determination confirmed the formation of a complex where a formal Co 3+ ion is sandwiched between η 4 -C 4 Me 4 2− and η 6 -2-Ph-2,3,4-C 3 B 7 H 9 1− ligands.In contrast to the reactions with diphenylacetylene, the reaction of 8 with 3-hexyne resulted in cage deboronation to produce 2,2-COD-10-Ph-closo-2,1,6,10-C 3 B 6 H 8 (14). Neither 7 nor 8 would undergo oxidativeaddition when treated with I 2 . Although 11 reacted with I 2 and perfluoro-1-iodohexane, oxidative-addition products were also not obtained, but instead, iodation of a cage boron occurred to produce 8,8-COD-1-CN t Bu-9-Ph-11-I-nido-8,7,9,10-IrC 3 B 7 H 8 (15).

A Neutral Heteroatomic Zintl Cluster for the Catalytic Hydrogenation of Cyclic Alkenes

“…The Rh–P distances (2.286(1) and 2.356(1) Å) are as expected for related compounds featuring a Rh(dppe) fragment (mean Rh–P distance 2.27(6) Å), 21 such the 2-Ph- closo -1,2,3,4-Rh(dppe)C 3 B 7 H 9 cluster, which has Rh–P distances of 2.232(1) and 2.285(1) Å. 19 …”

“…The Rh−P distances (2.286(1) and 2.356(1) Å) are as expected for related compounds featuring a Rh(dppe) fragment (mean Rh−P distance 2.27(6) Å), 21 such the 2-Ph-closo-1,2,3,4-Rh(dppe)C 3 B 7 H 9 cluster, which has Rh−P distances of 2.232(1) and 2.285(1) Å. 19 Compound 1 has a surface of accessible lone pairs from the unsubstituted germanium vertices. Reaction with 2 equiv of Ni(COD) 2 yields a species that exhibits two singlet resonances in its 1 H NMR spectrum, suggesting two inequivalent hypersilyl groups, that are accompanied by two sets of resonances for coordinated COD ligands in a 2:1 ratio (Scheme 3).…”

“…A single doublet resonance was observed in the 31 P­{ 1 H} NMR spectrum at 43.9 ppm [ J (Rh–P) = 160 Hz]. This is comparable to those of other closo clusters such as the metallacarborane 2-Ph- closo -1,2,3,4-Rh­(dppe)­C 3 B 7 H 9 (δ­( 31 P) 57.5 ppm, J (Rh–P) = 165 Hz) …”

“…This is comparable to those of other closo clusters such as the metallacarborane 2-Ph- closo -1,2,3,4-Rh(dppe)C 3 B 7 H 9 (δ( 31 P) 57.5 ppm, J (Rh–P) = 165 Hz). 19 …”

“…This is comparable to those of other closo clusters such as the metallacarborane 2-Ph-closo-1,2,3,4-Rh(dppe)C 3 B 7 H 9 (δ( 31 P) 57.5 ppm, J(Rh−P) = 165 Hz). 19 Crystals of 2 were grown from concentrated n-pentane solutions at −40 °C. The single-crystal X-ray structure (Figure 2) confirms that there is a change in the binding mode of the cluster.…”