Synthesis of Five‐Membered Osmacycloallenes and Conversion into Six‐Membered Osmacycloallenes

Abstract

Details of the preparation and characterization of 4 and 5 can be found in the Supporting Information.

Synthesis of Cyclic Vinylidene Complexes and Azavinylidene Complexes by Formal [4+2] Cyclization Reactions

“…Furthermore, in the case of model complex 4’ , the strain energy was calculated to be 3.1 kcal mol −1 . These DFT results agree well with previous reports, which showed that introduction of a transition‐metal atom or a main‐group heteroatom is an efficient strategy to reduce the inherent ring strain in cycloallenes …”

“…The structurald ata indicate that 3a is the first iso-metallapyridinium with form IV (Scheme 1), which is closely related to the iso-metallabenzenes.I ti sw orth noting that the Os1-C1-C2 angle (150.5(6)8)d eviates considerably from linearity and is even smaller than those of reported six-membered iso-metallabenzenes (155.1 (8)8 [5b] and 158.5(3)8 [5c] and iso-metallabenzenones (152.7(5)8 and 151.1(2)8). [6] This is further support that resonance form 3A is an important contribution to the overall structure of complex 3a.…”

“…Av iew of the complex cation is shown in Figure 3. The X-ray indicates that 4a (2) 173 (2) 173 (2) 173 (2) (17) 84.2(2) Os1-C1-C21 28.6(8)1 50.5 (6) 128.8(9)1 30.7(3)1 33.1(5) C1-C2-C3 125.8 (10) 115.2 (6) 127.2 (10) 127.0(4)1 23.5(6) C2-C3-C4 118.1(10) 114.7 (6) 109.0(9)1 11.5(4) 112.9(6) C3-C4-N1 121.0(11) 124.3 (7) 116.7 (10) 119.0(4) 123.5(6) C4-N1-Os1 139.4(9) 135.1(5) 152.5(8)1 52.9(3)1 34.8(5) Figure 2. Molecular structure of 3a.The hydrogen atoms of PPh 3 are omitted for clarity.…”

“…[5b, c] We have recently verifiedt he existence of the first five-membered metallacycles that contain am etal-vinylidene moiety (III)a nd the conversion of these compounds to their analogous six-membered metallacycles (II). [6] So far,r eported examples of cyclic vinylidene-metal complexes are limited to these three types.…”

Five‐Membered Cyclic Metal Carbyne: Synthesis of Osmapentalynes by the Reactions of Osmapentalene with Allene, Alkyne, and Alkene

“…The structures with CCC unit in five‐membered metallacycles, e.g., metallacycloallenes12 and metallacyclocumulenes,13 have been reported experimentally and theoretically. In contrast, the similar structure with a MCC unit in a five‐membered ring has only one example reported by us recently 14…”