Acetylide-Bridged Organometallic Oligomers via the Photochemical Metathesis of Methyl−Iron(II) Complexes

The acetylido methyl iron(II) complexes, cis/trans-[Fe(dmpe)2(C⋮CR)(CH3)] (1) and trans-[Fe(depe)2(C⋮CR)(CH3)] (2) (dmpe = 1,2-dimethylphoshinoethane; depe = 1,2-diethylphosphinoethane), were
synthesized by transmetalation from the corresponding alkyl halide complexes. Acetylido methyl iron(II)
complexes were also formed by transmetalation from the chloride complexes, trans-[Fe(dmpe)2(C⋮CR)(Cl)] or trans-[Fe(depe)2(C⋮CR)(Cl)]. The structure of trans-[Fe(dmpe)2(C⋮CC6H5)(CH3)] (1a) was
determined by single-crystal X-ray diffraction. The methyl acetylido iron complexes, [Fe(dmpe)2(C⋮CR)(CH3)] (1), are thermally stable in the presence of acetylenes; however, under UV irradiation, methane is
lost with the formation of a metal bisacetylide. Photochemical metathesis of cis- or trans-[Fe(dmpe)2(CH3)(C⋮CR)] (R = C6H5 (1a), 4-C6H4OCH3 (1b)) with terminal acetylenes was used to selectively synthesize
unsymmetrically substituted iron(II) bisacetylide complexes of the type trans-[Fe(dmpe)2(C⋮CR)(C⋮CR‘)]
[R = Ph, R‘ = Ph (6a), 4-CH3OC6H4 (6b), tBu (6c), Si(CH3)3 (6d), (CH2)4C⋮CH (6e); R = 4-CH3OC6H4, R‘
= 4-CH3OC6H4, (6g), tBu (6h), (CH2)4C⋮CH (6i), adamantyl (6j)]. The structure of the unsymmetrical iron(II)
bisacetylide complex trans-[Fe(dmpe)2(C⋮CC6H5)(C⋮CC6H4OCH3)] (6b) was determined by single-crystal
X-ray diffraction. The photochemical metathesis of the bis-acetylene, 1,7-octadiyne, with trans-[Fe(dmpe)2(CH3)(C⋮CPh)] (1a), was utilized to synthesize the bridged binuclear species trans,trans-[(C6H5C⋮C)Fe(dmpe)2(μ-C⋮C(CH2)4C⋮C)Fe(dmpe)2(C⋮CC6H5)] (11). The trinuclear species trans,trans,trans-[(C6H5C⋮C)Fe(dmpe)2(μ-C⋮C(CH2)4C⋮C)Fe(dmpe)2(μ-C⋮C(CH2)4C⋮C)Fe(dmpe)2(C⋮CC6H5)] (12) was synthesized
by the photochemical reaction of Fe(dmpe)2(C⋮CPh)(C⋮C(CH2)4C⋮CH) (6e) with Fe(dmpe)2(CH3)2.
Extended irradiation of the bisacetylide complexes with phenylacetylene resulted in insertion of the terminal
alkyne into one of the metal acetylide bonds to give acetylide butenyne complexes. The structure of the
acetylide butenyne complex, trans-[Fe(dmpe)2(C⋮CC6H4OCH3)(η1-C(C6H5)CH(C⋮CC6H4OCH3))] (9a) was
determined by single-crystal X-ray diffraction.

乙炔基甲基铁(II)配合物（acetylido methyl iron(II) complexes）包括顺式/反式-[Fe(dmpe)₂(C≡CR)(CH₃)]（1）与反式-[Fe(depe)₂(C≡CR)(CH₃)]（2）[其中dmpe=1,2-二甲基膦乙烷（1,2-dimethylphoshinoethane），depe=1,2-二乙基膦乙烷（1,2-diethylphosphinoethane）]，这类配合物可通过对应卤代烷基配合物的转金属化反应（transmetalation）合成。乙炔基甲基铁(II)配合物也可由氯化物配合物trans-[Fe(dmpe)₂(C≡CR)(Cl)]或trans-[Fe(depe)₂(C≡CR)(Cl)]经转金属化反应制得。反式-[Fe(dmpe)₂(C≡CC₆H₅)(CH₃)]（1a）的结构经单晶X射线衍射（single-crystal X-ray diffraction）表征确定。

[Fe(dmpe)₂(C≡CR)(CH₃)]（1）类甲基乙炔基铁配合物在炔烃存在下具备热稳定性；但在紫外辐照（UV irradiation）条件下会失去甲烷，生成双乙炔基金属配合物。以顺式或反式-[Fe(dmpe)₂(CH₃)(C≡CR)]（R=C₆H₅（1a）、4-CH₃OC₆H₄（1b））与末端炔烃的光化学复分解反应（photochemical metathesis），可选择性合成通式为trans-[Fe(dmpe)₂(C≡CR)(C≡CR’)]的不对称取代铁(II)双乙炔基配合物：其中R=Ph时，R’=Ph（6a）、4-CH₃OC₆H₄（6b）、叔丁基（tBu，6c）、三甲基硅基（Si(CH₃)₃，6d）、(CH₂)₄C≡CH（6e）；R=4-CH₃OC₆H₄时，R’=4-CH₃OC₆H₄（6g）、叔丁基（6h）、(CH₂)₄C≡CH（6i）、金刚烷基（adamantyl，6j）。不对称铁(II)双乙炔基配合物trans-[Fe(dmpe)₂(C≡CC₆H₅)(C≡CC₆H₄OCH₃)]（6b）的结构经单晶X射线衍射表征确定。

以双炔1,7-辛二炔与trans-[Fe(dmpe)₂(CH₃)(C≡CPh)]（1a）的光化学反应，可合成桥联双核物种trans,trans-[(C₆H₅C≡C)Fe(dmpe)₂(μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂(C≡CC₆H₅)]（11）。三核物种trans,trans,trans-[(C₆H₅C≡C)Fe(dmpe)₂(μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂(μ-C≡C(CH₂)₄C≡C)Fe(dmpe)₂(C≡CC₆H₅)]（12）则通过Fe(dmpe)₂(C≡CPh)(C≡C(CH₂)₄C≡CH)（6e）与Fe(dmpe)₂(CH₃)₂的光化学反应制得。

对双乙炔基配合物与苯乙炔进行长时间辐照，会发生末端炔烃向金属乙炔基键的插入反应，生成乙炔基丁炔烯配合物。乙炔基丁炔烯配合物trans-[Fe(dmpe)₂(C≡CC₆H₄OCH₃)(η¹-C(C₆H₅)=CH(C≡CC₆H₄OCH₃))]（9a）的结构经单晶X射线衍射表征确定。