Regioselective Hydromethoxycarbonylation of Terminal Alkynes Catalyzed by Palladium(II)–Tetraphos Complexes

Abstract

An in situ generated dinuclear palladium hydride complex bearing cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphanyl)cyclobutane catalyzed the hydromethoxycarbonylation of terminal alkynes, giving the corresponding branched α,β-unsaturated ester (A) with high regioselectivity.

Versatile Supramolecular Coordination Behaviour of a Bis(bidentate) Tetraphosphane

“…[10] The formation of two fused seven-membered rings could be the thermodynamic driving force (see Figure 3). [12] Hence, the corresponding NiP 4 core for 1 has not been observed owing to the significantly shorter Ni-P bond lengths compared to Pd-P bonds (see Scheme 1). However, a structure type like that of 2 is not possible for 1.…”

“…However, as for 3 and 3Ј, both conformations of 4 show axial phosphanoyl and equatorial phosphanyl groups ( Figure 5). The analogous torsion angles for the second conformation are 139.68 (12) and 88.93(19)°, respectively. The analogous torsion angles for the second conformation are 139.68 (12) and 88.93(19)°, respectively.…”

“…[13] Therefore, the study of the synthetic protocol for these dyadic and related triadic assemblies in good yield is an important task. [12,15] The monometallic precursor complex [Ru(bpy) 2 -(dppcb)](PF 6 ) 2 [2] smoothly reacts with [NiBr 2 (DME)] to give the heterodimetallic species [Ru(bpy) 2 (dppcb)-NiBr 2 ](PF 6 ) 2 (1) in good yield (Scheme 1). [14] For tetraphosphane bridging ligands, different coordination modes containing more than one tetraphosphane ligand come into play (Schemes 1 and 2).…”

“…[12] Therefore, it is interesting to study the coordination behaviour of a different dioxide of dppcb, namely, 2,3-trans-dppcbO 2 (4, Scheme 2). [12] Therefore, it is interesting to study the coordination behaviour of a different dioxide of dppcb, namely, 2,3-trans-dppcbO 2 (4, Scheme 2).…”

“…To confirm that this versatile coordination behaviour of dppcb and its derivatives is a common property, the reaction of the new ligand cis , trans , cis ‐2,3‐bis(diphenylphosphanoyl)‐1,4‐bis(diphenylphosphanyl)cyclobutane (2,3‐ trans ‐dppcbO 2 , 4 )11 in isolated form with palladium(II) was also investigated (Scheme ). Usually, it is not possible to combine two dppcb ligands with one palladium(II) centre to generate a square‐planar PdP 4 core 12. However, two equivalents of 4 and one equivalent of [Pd(CH 3 CN) 4 ](BF 4 ) 2 exclusively produce meso ‐(MMMP/MPPP)‐[Pd(2,3‐ trans ‐dppcbO 2 ‐ P , P′ ) 2 ](BF 4 ) 2 ( 3 ), which has this square‐planar PdP 4 core.…”