The η2-alkyne complex [Fe(CO)2P(OPh)3}2(η2-PhCCPh)] 1 reacts readily with PR3 to give [Fe(CO)2P(OPh)3}(PR3)(η2-PhCCPh)], and then [Fe(CO)2(PR3)2(η2-PhCCPh)] (R = OMe, 2a; OEt, 2b; OnBu, 2c; Me, 2d; nBu, 2e; Ph, 2f). The ability of the alkyne ligand to act as a four-electron donor to a ligand-dissociated 16-electron reaction intermediate promotes site-specific replacement of the axial phosphite ligands; there is no evidence for equatorial CO replacement. Reaction of 1 with CO affords six-coordinate ferracyclopent-3-ene-2,5-dione (maleoyl) complexes [Fe(CO)mP(OPh)3}nη1 â¶Â η1-C(O)C(Ph)C(Ph)C(O)}] (m = 3, n = 1, 3; m = n = 2, 4a) in which CO groups have inserted into each of the FeâC(alkyne) bonds. Analogues of 4a, [Fe(CO)2P(OR)3}2η1 â¶Â η1-C(O)C(Ph)C(Ph)C(O)}] (R = Me, 4b; Et, 4c), are similarly obtained as the sole products from the reaction of CO with 2a and 2b, respectively. The mechanism proposed for this reaction depends on replacement of an axial phosphite ligand by CO which is then susceptible to migratory attack by C(alkyne), whereas the existing equatorial CO ligands are not. The crystal structure of 3 has been determined: the complex exhibits a distorted octahedral geometry about the iron centre with a facial arrangement of the three CO ligands and the remaining coordination sites occupied by the P(OPh)3 ligand and by the two C(O) groups of the maleoyl moiety. Reaction of 1 and CNR (R = Me and Ph) also proceeds via alkyneâCNR coupling to give [Fe(CO)2P(OPh)3}η1 â¶Â η1 â¶Â η1 â¶Â η1-C(NR)C(Ph)C(Ph)C(NR)}] which is proposed to have a square pyramidal geometry on the basis of spectroscopic data.
η2-
炔烃络合物[Fe(CO)2P(OPh)3}2(η2-PhCCPh)] 1与PR3反应,生成[Fe(CO)2P(OPh)3}(PR3)(η2-PhCCPh)],然后进一步生成[Fe(CO)2(PR3)2(η2-PhCCPh)](R = OMe, 2a; OEt, 2b; OnBu, 2c; Me, 2d; nBu, 2e; Ph, 2f)。
炔烃配体作为四电子供体的能力促进了轴向
磷酸酯
配体的特定位点替换;没有证据表明发生了赤道CO替换。1与CO反应生成六配位的
铁环戊-3-烯-2,5-二酮(马来酰)络合物[Fe(CO)mP(OPh)3}nη1 ‡ η1-C(O)C(Ph)C(Ph)C(O)}](m = 3, n = 1, 3;m = n = 2, 4a),其中CO基团插入了每一个Fe-C(
炔烃)键中。与2a和2b的CO反应分别得到的类似物4a,[Fe(CO)2P(OR)3}2η1 ‡ η1-C(O)C(Ph)C(Ph)C(O)}](R = Me, 4b;Et, 4c),是反应的唯一产物。该反应的机制依赖于通过CO替换轴向
磷酸酯
配体,随后CO易于受到C(
炔烃)的迁移攻击,而现有的赤道CO
配体则不受影响。复合物3的晶体结构已被确定:该复合物在
铁中心周围呈现扭曲的八面体几何形状,三个CO
配体呈面状排列,其余配位位点由P(OPh)3
配体和马来酰的两个C(O)基团占据。1与CNR(R = Me和Ph)的反应也通过
炔烃-CNR耦合进行,生成[Fe(CO)2P(OPh)3}η1 ‡ η1 ‡ η1 ‡ η1-C(NR)C(Ph)C(Ph)C(NR)}],基于光谱数据,推测其具有方锥形几何结构。