Unsymmetrical Diborane(4) as a Precursor to PBP Boryl Pincer Complexes: Synthesis and Cu(I) and Pt(II) PBP Complexes with Unusual Structural Features

An unsymmetrical diamino dialkoyx diborane(4), (1,2-((iPr)2PCH2N)2(C6H6))­B−B­((OCMe2)2), with additional
P donor
moieties in the diaminoboryl moiety was straightforwardly obtained
by the reaction of a copper­(I) boryl complex as a boron nucleophile
and the respective borane, (1,2-((iPr)2PCH2N)2(C6H6))­B−H,
as boron electrophile. This diborane(4) reacted with copper­(I) tert-butoxide via σ-bond metathesis and [Pt­(P­(iPr)3)2] via oxidative addition. The
first reaction results in a novel bis-μ-boryl
di-copper­(I) complex, featuring an unprecedented unsymmetrical structure,
whereas the latter reaction leads initially to a cis-bis-boryl platinum­(II) complex, that converts to an unprecedented trans-bis-boryl complex as the thermodynamic
product. All complexes have been comprehensively characterized by
NMR spectroscopy in solution and by single-crystal X-ray diffraction
in the solid state, complemented by computations of thermodynamic
data and relaxed force constants at the DFT level of theory.