Syntheses of η¹‐Alkyl‐η³‐Allyl‐η⁵‐Cyclopentadienyl Cobalt(III) Complexes and Their Use in Low‐temperature Atomic Layer Deposition of Cobalt‐Containing Thin Films

Abstract

Herein, we report the design and scalable synthesis of three new Co(III) complexes, which have an unusual hydrocarbon η1‐alkyl‐η3‐allyl‐η5‐cyclopentadienyl ligation structure, from the reactions of readily available cobalt(II) compound CoCl2(PPh3)2 and biomass material β‐pinene via C−C bond activation. These Co(III) complexes are air‐stable, fairly volatile, and thermally stable, so they are excellent candidates as the metal precursors for the vapor deposition of cobalt‐containing thin films. As a demonstration, we show that the Co(III) complex of [(3’‐5’‐η,1‐σ)‐methylene(2,2,4‐trimethyl‐4‐cyclohexene‐1,3‐diyl)](η5‐methylcyclopentadienyl)Co (i. e. (seco‐pinene)(MeCp)Co) is well suited for the atomic layer deposition (ALD) of Co3O4 and CoS2 thin films, and the deposited Co3O4 and CoS2 films are able to conformally cover trench structures with a fairly high aspect ratio of 10 : 1.

Efficient hole extraction and dark current suppression in organic photodetectors enabled by atomic-layer-deposition of ultrathin Co3O4 interlayers

“…Co 3 O 4 thin films were deposited on ITO glass substrates by ALD using ((seco-pinene)(MeCp)Co) and O 2 plasma as the cobalt precursor and co-reacting oxidant, respectively. 21 The deposition was carried out at 180 °C, and the cobalt precursor was kept at 50 °C. In each ALD cycle, the exposures of ((seco-pinene)(MeCp)Co) and O 2 plasma were 225 and 900 mTorr s −1 , respectively, and they were separated by 30 s of N 2 purging.…”

Organotransition Metal Chemistry of Terpenes: Syntheses, Structures, Reactivity and Molecular Rearrangements

“…A different application of this approach involves the reaction of (C 5 Me 5 )Co(PPh 3 ) 2 with β-pinene, whereupon bond fission leads to 222 containing both η 1 -and η 3 -allyl attachments to cobalt, a structure closely analogous to that of the iron complex 161 shown in Figure 4. However, the goal here is very different; this molecule, and a number of its variants, have been found to be ideal for the low-temperature atomic-layer deposition of cobalt-containing thin films to cover complex 3D structures [121]. One should always respect and admire those pioneers in the chemistry of terpenoids who attempted to determine the structures of complex organic and organometallic molecules without access to the spectroscopic equipment now available.…”