Diboration of Dialkynes with [2]Boraferrocenophanes

A series of new [4]diboradicarbametalloarenophanes was synthesized via transition-metal-mediated diboration of selected dialkynes by [Fe{eta(5)-C5H4B(NMe2)}(2)] (3) and [Fe{eta(5)-C5H4B(NMe2))(2)Pt(PEt3)(2)] (18), respectively. Hereby, we have found three different structural motifs: (i) single diboration of the dialkynes to afford [Fe{eta(5)-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-eta(2)-Fe{eta(5)-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{eta(5)-C5H4B(NMe2)}(2){Me3Si}C=C)(2)C6H4]. Additionally, a series of mononuclear and dinuclear platinum alkyne complexes, [(Et3P)(2)Pt(1,2-eta(2)-R-C C-X-C C-R)] and [{(Et3P)(2)Pt}(2) (mu-1,2-eta(2)-3,4-eta(2)-R-C C-X-C)](R = Me, no X; R = Ph, no X; R = SiMe3, X = 1,4-C6H4), and the platinum alkene complex [(Et3P)(2)Pt(34-eta(2)-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, 2,4, 26a, 27b, and 29), additionally by X-ray diffraction analysis.