The reaction of Ni(COD)2
(COD = 1,5-cyclooctadiene) with triethylphosphine and pentafluoropyridine in hexane has been shown previously to yield trans-[NiF(2-C5NF4)(PEt3)2]
(1a) with a preference for reaction at the 2-position of the heteroaromatic. The corresponding reaction with 2,3,5,6-tetrafluoropyridine was shown to yield trans-[NiF(2-C5NF3H)(PEt3)2]
(1b). In this paper, we show that reaction of Ni(COD)2 with triethylphosphine and pentafluoropyridine in THF yields a mixture of 1a and 1b. Competition reactions of Ni(COD)2 with triethylphosphine in the presence of mixtures of heteroaromatics in hexane reveal a kinetic preference of k(pentafluoropyridine) : k(2,3,5,6-tetrafluoropyridine)
= 5.4 : 1. Treatment of 1a and 1b with Me3SiN3 affords trans-[Ni(N3)(2-C5NF4)(PEt3)2]
(2a) and trans-[Ni(N3)(2-C5NHF3)(PEt3)2]
(2b), respectively. The complex trans-[Ni(NCO)(2-C5NHF3)(PEt3)2]
(3b) is obtained on reaction of 1b with Me3SiNCO and by photolysis of 2b under CO, while trans-[Ni(η1-CCPh)(2-C5NF4)(PEt3)2]
(4a) is obtained by reaction of phenylacetylene with 1a. Addition of KCN, KI and NaOAc to complex 1a affords trans-[Ni(X)(2-C5NF4)(PEt3)2]
(5a X = CN, 6a X = I, 7a X = OAc), respectively. The PEt3 groups of complex 1a are readily replaced by addition of 1,2-bis(dicyclohexylphosphino)ethane (dcpe) to produce [NiF(2-C5F4N)(dcpe)]
(8a). Addition of dcpe to trans-[Ni(OTf)(2-C5F4N)(PEt3)2]
(10a), however, yields the salt [Ni(2-C5F4N)(dcpe)(PEt3)](OTf)
(9a) by substitution of only one PEt3 and displacement of the triflate ligand. The structures of 2b, 4a, 7a and 8a were determined by X-ray crystallography. The influence of different ancillary ligands on the bond lengths and angles of square-planar nickel structures with polyfluoropyridyl ligands is analysed.
Ni(COD)2的反应
(COD =
1,5-环辛二烯) 与
三乙基膦和五
氟吡啶在己烷中的反应先前已被证明可产生反式-[NiF(2-C5NF4)(PEt3)2]
(1a) 优选在杂芳族化合物的2-位上反应。与 2,3,5,6-四
氟吡啶的相应反应显示产生反式-[NiF(2-C5NF3H)(PEt3)2]
(1b)。在本文中,我们证明 Ni(COD)2 与
三乙基膦和五
氟吡啶在 THF 中反应生成 1a 和 1b 的混合物。 Ni(COD)2 与
三乙基膦在己烷中杂芳族化合物混合物存在下的竞争反应揭示了 k(五
氟吡啶) 的动力学偏好:k(2,3,5,6-四
氟吡啶)
= 5.4 : 1. 用 Me3SiN3 处理 1a 和 1b 得到反式-[Ni(N3)(2-C5NF4)(PEt3)2]
(2a) 和反式-[Ni(N3)(2-C5NHF3)(PEt3)2]
分别为(2b)。配合物反式-[Ni(NCO)(2-C5NHF3)(PEt3)2]
(3b) 是通过 1b 与 Me3SiNCO 反应并通过在 CO 下光解 2b 获得的,而反式-[Ni(β1-CCPh)(2-C5NF4)(PEt3)2]
(4a)由
苯乙炔与1a反应得到。将 KCN、KI 和 NaOAc 添加到配合物 1a 中得到反式-[Ni(X)(2-C5NF4)(PEt3)2]
(5a X = CN,6a X = I,7a X = OAc)。配合物 1a 的 PEt3 基团很容易通过添加 1,2-双(
二环己基膦基)
乙烷 (dCPe) 进行替换,生成 [NiF(2-C5F4N)(dCPe)]
(8a)。将 dCPe 添加到反式-[Ni(OTf)(2-C5F4N)(PEt3)2] 中
然而,(10a) 产生盐 [Ni(2-C5F4N)(dCPe)(PEt3)](OTf)
(9a)仅取代一个PEt3并置换
三氟甲磺酸酯
配体。 2b、4a、7a和8a的结构通过X射线晶体学测定。分析了不同辅助
配体对多
氟吡啶配体的方形平面
镍结构的键长和角度的影响。