Diboration of Dialkynes with [2]Boraferrocenophanes

A series of new [4]diboradicarbametalloarenophanes was synthesized via transition-metal-mediated diboration of selected dialkynes by [Fe{η5-C5H4B(NMe2)}2] (3) and [Fe{η5-C5H4B(NMe2)}2Pt(PEt3)2] (18), respectively. Hereby, we have found three different structural motifs: (i) single diboration of the dialkynes to afford [Fe{η5-C5H4B(NMe2)}2{R}CC–X–CC–R] (R = Me, no X; R = Ph, no X; R = SiMe3, X = C2H2; R = SiMe3, X = 1,4-C6H4), (ii) single diboration with additional coordination of the pendent CC triple bond to a [Pt(PEt3)2] fragment affording the dinuclear complexes [(3,4-η2-Fe{η5-C5H4B(NMe2)}2{R}CC–CC–R)Pt(PEt3)2] (R = Me; R = Ph), and (iii) double diboration of one dialkyne yielding [1,4-(Fe{η5-C5H4B(NMe2)}2{Me3Si}CC)2C6H4]. Additionally, a series of mononuclear and dinuclear platinum alkyne complexes, [(Et3P)2Pt(1,2-η2-R–CC–X–CC–R)] and [{(Et3P)2Pt}2(μ-1,2-η2-3,4-η2-R–CC–X–CC–R)] (R = Me, no X; R = Ph, no X; R = SiMe3, X = 1,4-C6H4), and the platinum alkene complex [(Et3P)2Pt(3,4-η2-E-R–CC–C{H}C{H}–CC–R)] (R = SiMe3) were derived from the reaction of [Pt(PEt3)3] (11) with the corresponding dialkynes. All compounds thus obtained were fully characterized by high-resolution NMR spectroscopy and, in selected cases (that is 14, 24, 26a, 27b, and 29), additionally by X-ray diffraction analysis.