Reactivity of Tetrahalo- and Difluorodiboranes(4) toward Lewis Basic Platinum(0): Bis(boryl), Borylborato, and Doubly Boryl-Bridged Platinum Complexes

The
reaction of the tetrahalodiboranes(4) B2F4,
B2Cl4, and B2Br4 with
a Lewis basic platinum(0) complex led to the isolation of the cis-bis­(difluoroboryl) complex cis-[(Cy3P)2Pt­(BF2)2] (1) and the novel borylborato complexes trans-[(Cy3P)2Pt­{B­(X)–BX3}] (2, X = Cl; 3, X = Br), respectively. The trans influence
of the borylborato group was found to be one of the strongest ever
observed experimentally. Furthermore, the reactivity of little-explored
diaryldifluorodiboranes(4) F2B–BMes2 and
the new derivative F2B–BAn2 (An = 9-anthryl)
toward a range of platinum(0) complexes was investigated. Reactions
with relatively nonbulky platinum(0) complexes led to the formation
of unsymmetrical cis-bis­(boryl) complexes cis-[(R3P)2Pt­(BF2)­(BMes2)] (6, R = Me; 7, R = Et) as well
as the first example of a fourfold-unsymmetrical bis­(boryl) complex,
[(Me3P)­(Cy3P)­Pt­(BF2)­(BMes2)] (12). The use of a more bulky Pt complex provided
access to the unprecedented dinuclear bis­(boryl) complexes [{(iPr3P)­Pt}2(μ-BF2)­(μ-BAr2)] (8, Ar = Mes; 9, Ar = An), which
feature two different μ2-bridging boryl ligands.

四卤代乙硼烷(4)（tetrahalodiboranes(4)）B₂F₄、B₂Cl₄与B₂Br₄分别与路易斯碱性铂(0)配合物发生反应，可分离得到顺式双(二氟硼基)配合物cis-[(Cy₃P)₂Pt(BF₂)₂]（1）以及新型硼基硼酰配合物trans-[(Cy₃P)₂Pt{B(X)–BX₃}]（2，X=Cl；3，X=Br），其中Cy₃P为三环己基膦（tricyclohexylphosphine）。研究发现，该硼基硼酰配体的反位影响（trans influence）是目前实验观测到的最强反位影响之一。此外，本研究还探究了鲜有报道的二芳基二氟乙硼烷(4)（diaryldifluorodiboranes(4)）F₂B–BMes₂及其新型衍生物F₂B–BAn₂（An=9-蒽基，9-anthryl）与一系列铂(0)配合物的反应活性。采用空间位阻相对较小的铂(0)配合物进行反应，可得到不对称顺式双(硼基)配合物cis-[(R₃P)₂Pt(BF₂)(BMes₂)]（6，R=Me，甲基；7，R=Et，乙基），以及首例四配位不对称双(硼基)配合物[(Me₃P)(Cy₃P)Pt(BF₂)(BMes₂)]（12）。使用空间位阻更大的铂配合物，则可制备前所未有的双核双(硼基)配合物[{(iPr₃P)Pt}₂(μ-BF₂)(μ-BAr₂)]（8，Ar=Mes，均三甲苯基；9，Ar=An，9-蒽基），该类配合物含有两种不同的μ₂-桥联硼基配体（μ₂-bridging boryl ligands），其中iPr₃P为三异丙基膦（triisopropylphosphine）。