The activation of tertiary amines by osmium cluster complexes: Further studies of the reaction of Os 3 (CO) 10 (NCMe) 2 with triethylamine

The reactions of Os 3 (CO) 12 and Os 3 (CO) 10 (NCMe) 2 with NEt 3 have been reinvestigated. Two new products, Os 3 (CO) 10 (μ‐CH 2 C(H)NEt 2 )(μ‐H)) (2) and Os 3 (CO) 10 ( syn ‐μ‐η 1 ‐CHCHNEt 2 )(μ‐H) (3) were obtained in low yields, 4% and 7%, in addition to the previously reported compound Os 3 (CO) 10 ( anti ‐μ‐η 1 ‐CHCHNEt 2 (μ‐H) (1) (20% yield) when the reaction was conducted at 25°C using Os 3 (CO) 10 (NCMe) 2 . Compounds 2 and 3 were characterized by IR, 1 H NMR and single‐crystal X‐ray diffraction analyses. Compound 2 contains a bridging methyl‐metallated N ‐ethylimine ligand formed by the cleavage of one ethyl group from the NEt 3 . Compound 3 is an isomer of 1 in which the bridging ligand has a syn conformation with respect to the cluster as compared with the anti conformation in 1. Compound 3 slowly isomerizes to 1. Compound 3 is de‐carbonylated by exposure to UV radiation and is transformed to the new compound Os 3 (CO) 9 (μ 3 ‐CC(H)NEt 2 )(μ‐H) 2 (4) (58% yield) by an additional CH activation to form a triply bridging η 1 ‐diethylaminovinylidene ligand. Compound 4 isomerizes to the compound Os 3 (CO) 9 (μ 3 ‐HCCNEt 2 )(μ‐H) 2 (5) (70% yield) at 68°C. The latter contains a triply briding ynamine ligand which exhibits structural and reactivity features that are characteristic of a carbene ligand at the amine‐substituted carbon atom. Crystal data: for 2, space group = P 2 1 /c, a = 9.236(2) Å, b = 12.469(2) Å, c = 18.107(3) Å, β = 104.67(1)°, Z = 4, 2518 reflections, R = 0.031; for 3, space group = P 2 1 /m, a = 7.644(1) Å, b = 12.706(2) Å, c = 11.912(2) Å, β = 108.02(1)°, Z = 2, 1295 reflections, R = 0.030; for 4, space group = P 2 1 /n, a = 10.233(2) Å, b = 14.834(4) Å, c = 14.538(2) Å, β = 99.88(2)°, Z = 4, 2403 reflections, R = 0.036.