Protonation Studies of a Tungsten Dinitrogen Complex Supported by a Diphosphine Ligand Containing a Pendant Amine

详细信息    查看全文

• 作者：Charles J. Weiss ; Jonathan D. Egbert ; Shentan Chen ; Monte L. Helm ; R. Morris Bullock ; Michael T. Mock
• 刊名：Organometallics
• 出版年：2014
• 出版时间：May 12, 2014
• 年：2014
• 卷：33
• 期：9
• 页码：2189-2200
• 全文大小：511K
• 年卷期：v.33,no.9(May 12, 2014)
• ISSN：1520-6041

文摘

Treatment of trans-[W(N₂)₂(dppe)(P^EtN^MeP^Et)] (dppe = Ph₂PCH₂CH₂PPh₂; P^EtN^MeP^Et = Et₂PCH₂N(Me)CH₂PEt₂) with 3 equiv of tetrafluoroboric acid (HBF₄路Et₂O) at 鈭?8 掳C generated the seven-coordinate tungsten hydride trans-[W(N₂)₂(H)(dppe)(P^EtN^MeP^Et)][BF₄]. At higher temperatures, protonation of a pendant amine is also observed, affording trans-[W(N₂)₂(H)(dppe)(P^EtN^Me(H)P^Et)][BF₄]₂, with formation of the hydrazido complex [W(NNH₂)(dppe)(P^EtN^Me(H)P^Et)][BF₄]₂ as a minor product. A similar product mixture was obtained using triflic acid (HOTf). The protonated products are thermally sensitive and do not persist at ambient temperature. Upon acid addition to the carbonyl analogue cis-[W(CO)₂(dppe)(P^EtN^MeP^Et)], the seven-coordinate carbonyl hydride complex trans-[W(CO)₂(H)(dppe)(P^EtN^Me(H)P^Et)][OTf]₂ was generated. A mixed diphosphine complex without the pendant amine in the ligand backbone, trans-[W(N₂)₂(dppe)(depp)] (depp = Et₂P(CH₂)₃PEt₂), was synthesized and treated with HOTf, selectively generating a hydrazido complex, [W(NNH₂)(OTf)(dppe)(depp)][OTf]. Computational analysis probed the proton affinity of three sites of protonation in these complexes: the metal, pendant amine, and N₂ ligand. Room-temperature reactions with 100 equiv of HOTf produced NH₄⁺ from reduction of the N₂ ligand (electrons come from W). The addition of 100 equiv of HOTf to trans-[W(N₂)₂(dppe)(P^EtN^MeP^Et)] afforded 0.81 equiv of NH₄⁺, while 0.40 equiv of NH₄⁺ was formed upon treatment of trans-[W(N₂)₂(dppe)(depp)] with HOTf, showing that the complexes containing proton relays produce more products of reduction of N₂.