123125-59-7Relevant articles and documents
CO labilization and hydrogen-transfer pathways in cationic phosphido-bridged Re-Pt heterobimetallic systems and the molecular structures of [η5-Cp(ON)Re(μ-PR2)(μ-H)Pt(PPh3) 2]X (R = Cy, X- = PF6-; R = Ph, X- = BF4-) and [η5-Cp(ON)HRe(μ-PCy ...
Powell, John,Sawyer, Jeffery F.,Stainer, Matthew V. R.
, p. 4461 - 4470 (2008/10/08)
Full title: CO labilization and hydrogen-transfer pathways in cationic phosphido-bridged Re-Pt heterobimetallic systems and the molecular structures of [η5-Cp(ON)Re(μ-PR2)(μ-H)Pt(PPh3) 2]X (R = Cy, X- = PF6-; R = Ph, X- = BF4-) and [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3) 2]BF4, a rare example of bridging- and terminal-hydrido geometric isomers. Oxidative addition of the cationic secondary phosphine complexes [η5-Cp(OC)(ON)Re(PR2H)]+ (6) (R = Ph, Cy, Pr) to Pt(C2H4)(PPh3)2 gives [η5-Cp(OC)(ON)Re(μ-PR2)PtH(PPh3) 2]+ (7). In contrast, reaction of 6 with Pt(PPh3)4 leads to CO loss and the formation of the terminal rhenium hydride derivative [η5-Cp(ON)HRe(μ-PR2)Pt(PPh3) 2]+ (8) as the kinetic product. On standing, 8 slowly transforms into the thermodynamically preferred bridging-hydrido isomer [η5-Cp(ON)Re(μ-PR2)(μ-H)-Pt(PPh 3)2]+ (9). The cations 7 will undergo slow CO loss to form 8 in the presence of base (e.g. F-, proton sponge), and the isomerization of 8 to 9 is promoted by added chloride ion with -d[8]/dt = k[8][Cl-]2. Complex 7 (R = Cy) reacts with added Cl- to give [η5-Cp(OC)(ON)Re(μ-PCy2)PtHCl(PPh3)] (10b), which reacts with Cl- abstractors (Ag+ or NaBPh4) to give an equilibrium mixture of [η5-Cp(ON)Re(μ-PCy2)(μ-H)Pt(PPh 3)(CO)]+ (11b) and [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3)(CO)] +, (12b) (PPh3 trans to μ-PCy2), which slowly transform to give [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3)(CO)] + (13b) (PPh3 cis to μ-PCy2). Cations 12b and 13b react rapidly with PPh3 to give 8 while 11b reacts with PPh3 to give 9b. The mechanism of formation of 7 and 8 from 6 and the mechanism of the base-promoted 7 to 8 rearrangement and the Cl--catalyzed 8 to 9 isomerization process are discussed. The molecular structures of [η5-Cp(ON)HRe(μ-PCy2)Pt(PPh3) 2]BF4 ((8b)BF4) and [η5-Cp(ON)Re(μ-PCy2)(μ-H)Pt(PPh 3)2]PF6 ((9b)PF6) (a rare example of terminal- and bridging-hydrido isomers) and [η5-Cp(ON)Re(μ-PPh2)(μ-H)Pt-(PPh 3)2]BF4 ((9a)BF4) have been determined. Crystal data for (8b)BF4: C53H58BF4NOP3PtRe·CH 2Cl2 crystallizes in space group P21/n with a = 11.031 (2) A?, b = 22.391 (5) A?, c = 21.603 (7) A?, β = 94.04 (2)°, V = 5322 A?3, and Z = 4. The structure was refined to R = 0.0407 and Rw = 0.0419. Crystal data for (9a)BF4: C53H46BF4NOP3PtRe, space group P1 with a = 12.563 (2) A?, b = 12.896 (1) A?, c = 15.024 (2) A?, α = 94.14 (1)°, β = 96.93 (2)°, γ = 92.01 (1)°, V = 2407 A°3, and Z = 2. The structure was refined to R = 0.0310 and Rw = 0.0325. Crystal data for (9b)PF6: C53H58F6NOP4PtRe·2.5CH 2Cl2, space group P1, a = 12.532 (2) A?, b = 13.077 (2) A?, c = 19.101 (2) A?, α = 94.85 (1)°, β = 105.40 (1)°, γ = 91.23 (1)°, V = 3004 A?3, and Z = 2. The structure was refined to R = 0.0471 and Rw = 0.0508. Cations 9a and 9b contain a planar "Re(μ-PR2)(μ-H)Pt" unit, the bridging hydrogen atom being located in both structures from difference Fourier maps, refined by least squares. The cation 8b contains a planar "HRe(μ-PCy2)Pt" unit. The position of the terminal hydride is inferred to be bonded to Re (confirmed by 1H NMR) in a position approximately trans to the Pt-Re bond by using (i) the approach of Orpen for the calculation of minimization of van der Waals repulsion energies and (ii) EHMO calculations. In contrast to previous studies a good correlation between 1J195Pt-31P and Pt-P bond lengths is observed for the complexes 8b, 9a, and 9b.
