Diphenylphosphinoferrocene Gold(I) Acetylides: Synthesis of Heterotri- and Heterotetrametallic Transition Metal Complexes

The synthesis and reaction chemistry of heterobimetallic FcPPh2AuCl (1) and FcPPh2Au-CCR compounds (3a, R = bipy; 3b, R = C6H4-4-CN; 3c, R = C5H4N-4; 3d, R = NCN-H; 3e, R = NCN-I; Fc = (η5-C5H5)(η5-C5H4)Fe; bipy = 2,2′-bipyridyl-5-yl; NCN = [C6H2(CH2NMe2)2-2,6]−) toward diverse organometallic molecules is described. In context with this background, 1 was prepared by reacting FcPPh2 with (tht)AuCl (tht = tetrahydrothiophene). The reaction of 1 either with HCCR (2a, R = bipy; 2b, R = C6H4-4-CN; 2c, R = C5H4N-4) or with the lithium acetylides LiCCR (2d, R = NCN-H; 2e, R = NCN-I) gave complexes 3a−3e in good yield. In 1 the gold(I) chloride entity was further reacted with the organometallic alkyne HCCMLn (4a, MLn = (η6-C6H5)Cr(CO)3; 4b, MLn = Fc; 4c, MLn = Rc; Rc = (η5-C5H5)(η5-C5H4)Ru) to afford the heterotrimetallic complexes FcPPh2Au-CCMLn (5a, MLn = (η6-C6H5)Cr(CO)3; 5b, MLn = Fc; 5c, MLn = Rc) in which three different transition metal atoms are connected via rigid-rod structured carbon-rich units. Complexes 3a−3e feature with their terminal nitrogen donor groups a further binding site, which allows the introduction of a third metal-containing fragment. In this context, the reaction of 3b with [Ru]NN[Ru] (6) ([Ru] = [η3-mer-{2,6-(Me2NCH2)2C5H3N}RuCl2]) resulted in the formation of neutral heterotrimetallic FcPPh2Au-CC-C6H4-4-CN-[Ru] (7). The synthesis of an even heterotetrametallic complex [FcPPh2Au-CC-C5H4N-Cu{(Me3SiCC)2[Ti]}]OTf (9) could be achieved by treatment of 3c with the organometallic π-tweezer {[Ti](μ-σ,π-CCSiMe3)2}CuOTf (8a). Heterobimetallic 3a afforded in a straightforward reaction with equimolar amounts of (nbd)Mo(CO)4 (14) (nbd = 1,5-norbornadiene) and {[Ti](μ-σ,π-CCSiMe3)2}MX (8b, M = Cu(NCMe), X = PF6; 8c, M = Ag, X = OClO3), respectively, compounds FcPPh2Au-CC-bipy[Mo(CO)4] (15) and (FcPPh2Au-CC-bipy[{[Ti](μ-σ,π-CCSiMe3)2}M])X (16a, M = Cu, X = PF6; 16b, M = Ag, X = ClO4). The synthesis of the Fe-Au-Pt NCN pincer molecule FcPPh2Au-CC-NCN-Pt-CCR (13a, R = bipy; 13b, R = C6H4-4-CN) was possible by the consecutive reaction of Me3SiCC-NCN-PtCl (10) with Li-2a or Li-2b to give Me3SiCC-NCN-Pt-CCR (11a, R = bipy; 11b, R = C6H4-4-CN), which with [n-Bu4N]F produced HCC-NCN-Pt-CCR (12a, R = bipy; 12b, R = C6H4-4-CN). On reacting 12a and 12b with 1, complexes 13a and 13b were formed, which are highly insoluble, and hence, no further reactions were carried out. The solid state structures of 3a, 3b, 3e, 5b, 5c, and 16a are reported. Most characteristic for these complexes is that the appropriate transition metals are linked by carbon-rich organic bridging units. The electrochemical properties of selected samples (3a−3c, 5a−5c, 7, 9, 16a, and 16b) are reported. The cyclovoltammetric data show that there is no significant influence of the organic and organometallic acetylide units on the redox potential of the diphenylphosphino ferrocene in 3a− 3c and 5a−5c. Remarkable is that the chelate coordination of the bipyridyl unit to Cu(I) in 16a results in a reduction of Cu(I) followed by reoxidation of Cu(0) without any structural change of the molecule involved, which is unique in titanium(IV)−copper(I) chemistry.

本文报道了双金属异核配合物FcPPh2AuCl（1）与FcPPh2Au-C≡CR类化合物（3a，R = 2,2'-联吡啶-5-基（2,2′-bipyridyl-5-yl, bipy）；3b，R = C6H4-4-C≡N；3c，R = C5H4N-4；3d，R = NCN-H；3e，R = NCN-I；其中二茂铁（Ferrocene, Fc）= (η5-C5H5)(η5-C5H4)Fe；NCN = [C6H2(CH2NMe2)2-2,6]−）的合成与反应化学，用于构建各类有机金属分子。基于上述研究背景，配合物1通过FcPPh2与(tht)AuCl（其中四氢噻吩（tetrahydrothiophene, tht））反应制得。配合物1分别与炔烃HC≡CR（2a，R = bipy；2b，R = C6H4-4-C≡N；2c，R = C5H4N-4）或锂炔化物LiC≡CR（2d，R = NCN-H；2e，R = NCN-I）反应，以优异收率得到配合物3a~3e。配合物1中的氯化金(I)单元还可与有机金属炔烃HC≡CMLn（4a，MLn = (η6-C6H5)Cr(CO)3；4b，MLn = Fc；4c，MLn = Rc；其中钌茂（Ruthenocene, Rc）= (η5-C5H5)(η5-C5H4)Ru）反应，得到三金属异核配合物FcPPh2Au-C≡CMLn（5a，MLn = (η6-C6H5)Cr(CO)3；5b，MLn = Fc；5c，MLn = Rc），该类配合物中三种不同的过渡金属原子通过刚性棒状结构的富碳单元相连。配合物3a~3e的末端氮给体基团带有额外的配位位点，可用于引入第三类含金属片段。在此基础上，配合物3b与[Ru]N≡N[Ru]（6，其中[Ru] = [η3-mer-{2,6-(Me2NCH2)2C5H3N}RuCl2]）反应，得到中性三金属异核配合物FcPPh2Au-C≡C-C6H4-4-C≡N-[Ru]（7）。通过将配合物3c与有机金属π-镊子{[Ti](μ-σ,π-C≡CSiMe3)2}CuOTf（8a，其中三氟甲磺酰氧基（OTf, trifluoromethanesulfonate））反应，可合成四金属异核配合物[FcPPh2Au-C≡C-C5H4N-Cu{(Me3SiC≡C)2[Ti]}]OTf（9）。双金属异核配合物3a可分别与等摩尔量的(nbd)Mo(CO)4（14，其中1,5-降冰片二烯（1,5-norbornadiene, nbd））以及{[Ti](μ-σ,π-C≡CSiMe3)2}MX（8b，M = Cu(N≡CMe), X = PF6；8c，M = Ag, X = OClO3）发生简便反应，分别得到配合物FcPPh2Au-C≡C-bipy[Mo(CO)4]（15）与(FcPPh2Au-C≡C-bipy[{[Ti](μ-σ,π-C≡CSiMe3)2}M])X（16a，M = Cu, X = PF6；16b，M = Ag, X = ClO4）。Fe-Au-Pt型NCN钳形配合物FcPPh2Au-C≡C-NCN-Pt-C≡CR（13a，R = bipy；13b，R = C6H4-4-C≡N）的合成可通过如下步骤实现：先使Me3SiC≡C-NCN-PtCl（10）与Li-2a或Li-2b反应，得到Me3SiC≡C-NCN-Pt-C≡CR（11a，R = bipy；11b，R = C6H4-4-C≡N）；随后该中间体与四丁基氟化铵（tetra-n-butylammonium fluoride, [n-Bu4N]F）反应，得到HC≡C-NCN-Pt-C≡CR（12a，R = bipy；12b，R = C6H4-4-C≡N）。将12a与12b分别与配合物1反应，即可得到配合物13a与13b，该类配合物溶解性极差，因此未开展进一步反应。本文报道了配合物3a、3b、3e、5b、5c以及16a的固态晶体结构。该类配合物的典型特征为：不同过渡金属通过富碳有机桥联单元相连。本文还报道了所选样品（3a~3c、5a~5c、7、9、16a及16b）的电化学性质。循环伏安数据表明，在3a~3c与5a~5c中，有机及有机金属炔基单元对二苯基膦基二茂铁的氧化还原电位无显著影响。值得注意的是，在16a中，联吡啶单元与Cu(I)发生螯合配位后，会引发Cu(I)被还原为Cu(0)，随后Cu(0)又被重新氧化，且整个过程中分子结构未发生任何变化，这在钛(IV)-铜(I)化学领域中尚属首例。