Assembling Ligand Substitution Reactions Monitored by VT 31P{H} NMR Spectroscopy In Order to Shine Light on the Mechanism of Formation of the Pd–Pd Bond-Containing {Pd2 (dmb)2(diphos)2+} n , {Pd2(diphos′)2 (dmb)2+} n and {Pd2 (dppm)2 (diphos)2+} n Coordination/Organometallic Polymers

• Published in: Journal of inorganic and organometallic polymers and materials 2007-03, Vol.17 (1), p.251-258
• Main Authors: Samar, Dalila, Harvey, Pierre D.
• Format: Article
• Language: English
• Subjects: Chelation; Coordination; Ethane; Hexanes; Ligands; NMR spectroscopy; Organometallic polymers; Polymers; Spectrum analysis; Substitution reactions
• ISSN: 1574-1443; 1574-1451
• DOI: 10.1007/s10904-006-9079-y

The mechanism of formation of the related polymers {Pd2(dmb)2(diphos)2+}n, {Pd2(diphos′)2(dmb)2+}n and {Pd2(dppm)2(diphos)2+}n (dmb = 1,8-diisocyano-p-menthane; diphos = bis(diphenylphosphino)butane (dppb), bis(diphenylphosphino)pentane (dpppen), bis(diphenylphosphino)hexane (dpph); diphos‘ = bis(diphenylphosphino)ethane (dppe), bis(diphenylphosphino)propane (dppp); dppm = bis(diphenylphosphino)methane) was investigated through the bridging ligand substitution reaction between the d9–d9 Pd2(dmb)2Cl2 complex and dppm by means of VT 31P{H} NMR spectroscopy in 1:1 CD3OD/CD2Cl2mixture (193 < T < 293 K) in the presence or absence of LiClO4 and TlPF6. The reaction proceeds with the appearance and disappearance of intermediates, all easily identified from spectral comparison with related authentic samples, hence allowing determining the stepwise mechanism towards substitution, a process that contains all the necessary steps for the formation of the title polymers. For the polymers, which contains chelating diphosphines, this study indicates that the axial Cl-ligand must first dissociate to allow the primary P-coordination to form a η1-dppm-containing intermediate.