79870-63-6Relevant academic research and scientific papers
Syntheses, molecular structures, and stabilities of binuclear complexes [Pt2Me4(μ-R2PCH2PR 2)2]
Manojlovi?-Muir, Ljubica,Muir, Kenneth W.,Frew, Aileen A.,Ling, Samson S. M.,Thomson, Mary A.,Puddephatt, Richard J.
, p. 1637 - 1645 (2008/10/08)
Synthetic routes to binuclear complexes [Pt2Me4(μ-R2PCH2PR 2)2] (1, R = Me; 2, R = Ph; 3, R = Et) and to the mononuclear complexes [PtMe2(R2PCH2PR2)] (4, R = Ph; 5, R = i-Pr) have been developed. The structures and conformations of the binuclear complexes have been studied in solution by variable-temperature 1H and 31P NMR spectroscopy. The molecular structures of 1 and 2, determined by X-ray diffraction techniques, each contain two cis-PtMe2 fragments held together by two bridging R2PCH2PR2 ligands. The approximate molecular symmetry is C2h in 1 and C2 in 2, and the eight-membered Pt2P4C2 dimetallacycles adopt twist-chair and twist-boat conformations, respectively. In 1 the local environments of the platinum atoms are sterically more open than in 2, where the phenyl substituents may hinder access of reagents to the metal centers. Crystals of 1 are monoclinic of space group P21/a with a = 16.634 (4) A?, b = 11.112 (3) A?, c = 12.469 (3) A?, β = 103.40 (2)°, and Z = 4. Crystals of 2 are monoclinic of space group P21/c with a = 13.957 (7) A?, b = 17.218 (5) A?, c = 21.649 (5) A?, β = 106.45 (3)°, and Z = 4. Least-squares refinement of the structural model of 1 defined by 181 parameters converged at a conventional R index on F of 0.043 for 3646 reflections with I ≥ 3σ(I). For 2, the structural model involved 175 parameters and the final value of the R factor based on F was 0.068 for 3818 reflections. It is concluded that increasing steric bulk of substituents R (i) stabilizes the mononuclear with respect to the binuclear complex, (ii) is primarily responsible for determining the ground-state conformations of the binuclear complexes and the activation energies for fluxionality, and (iii) greatly decreases the reactivity of the complexes, and particularly the binuclear ones, toward oxidative addition reactions.
