New Arylruthenium(II) Complexes of the P,C,P‘-Coordinating Terdentate Monoanionic Aryl Ligands [C₆H₂(CH₂PPh₂)₂-2,6-R-4]^- (PCP-R-4; R = Ph, H). Synthesis of 16-Electron Species [Ru^IIX(PCP-R-4)(PPh₃)] (X = Cl, I, OTf) and Their Reactivity toward the Neutral Terdentate N-Donor Ligand 2,2‘:6‘,2‘‘-Terpyridine (terpy)

Abstract

The synthesis and characterization of new, five-coordinate, diamagnetic, 16-electron arylruthenium(II) complexes [RuIIX{C6H2(CH2PPh2)2-2,6-R-4}(PPh3)] (1, X = Cl, R = H; 2, X = Cl, R = Ph; 3, X = OSO2CF3, R = H; 4, X = I, R = H) are described. These coordinatively unsaturated complexes contain a stable Caryl−Ru σ-bond resulting from pseudomeridional terdentate P,C,P‘-bonding of the monoanionic {C6H2(CH2PPh2)2-2,6-R-4}- ligand (general abbreviation PCP-R-4; for R = H and R = Ph, abbreviated as PCP and PCP-Ph, respectively) that also provides two P → Ru bonds. This bonding mode of the PCP-R-4 ligands adopted in complexes 1−4 means that these species are structurally closely related to the complexes [RuCl{C6H2(CH2NMe2)2-2,6-R-4}(PPh3)] (R = H, Ph) in which there is terdentate N,C,N‘-coordination. Complexes 1 and 2 were synthesized via cyclometalation reactions of the respective neutral diphosphine compounds C6H3(CH2PPh2)2-2,6-R-4 (general abbreviation PC(H)P-R-4; for R = H and R = Ph, abbreviated as PC(H)P and PC(H)P-Ph, respectively) with [RuIICl2(PPh3)4]. The complex [RuII(OTf)(PCP)(PPh3)], 3, prepared by reaction of 1 with AgOTf (OTf = OSO2CF3 = triflate), has the triflate anion bound to ruthenium in noncoordinating solvents. On the NMR time scale complex 3 in solution exhibits temperature-dependent fluxionality that is associated with reversible changes of the complex stereochemistry. The triflate PCP complex 3 reacts cleanly with the neutral N-donor ligand 2,2‘:6‘,2‘‘-terpyridine (terpy) to afford [RuII(PCP)(terpy)][OTf], 5. However, whereas the reaction of terpy with the PCP-Ph complex 2 affords [RuII(PCP-Ph)(terpy)]Cl, 6, its reaction with PCP chloro complex 1 generates a mixture of products. These reactivities of PCP and PCP-Ph complexes (1−3) toward terpy are compared and contrasted with those of related ruthenium complexes containing the monoanionic aryldiamine ligand {C6H2(CH2NMe2)2-2,6-R-4}- (abbreviated as NCN-R-4).

Synthesis, Crystal Structure, and Redox and Photophysical Properties of Novel Bisphosphinoaryl RuII-Terpyridine Complexes

“…8b,f,i As shown in Scheme (10) 4, [Ru(PCP)(tpy)]Cl complexes 11 and 12 are readily prepared in high yield (86 and 84%, respectively) by reaction of [RuCl(PCP)(PPh 3 )] complexes 9 and 10, respectively, with tpy in dry MeOH at reflux temperature. 9 The red complexes 11 and 12 are soluble in apolar solvents and alcohols, such as methanol and ethanol, and were fully characterized by NMR spectroscopy in CD 2 Cl 2 and elemental analysis. Because of the long reaction times (3 days at reflux), other preparative procedures were examined in order to obtain the desired complexes faster and with comparable selectivity.…”

“…NMR data of the obtained complex 14 prepared by applying both synthetic procedures were consistent with values earlier reported. 9 Crystals suitable for X-ray diffraction determination were obtained by slow diffusion of diethyl ether vapor into a solution of 14 in CH 2Cl2. A selection of bond lengths, angles, and torsion angles is summarized in Table 2 …”

Structural Investigation in Solution of a Series of Five-Coordinate Bisphosphanylaryl Ruthenium(II) Complexes

“…Complexes 1, 2 [2] and 3 [25] were prepared according to literature procedures. All manipulations were performed under a dry nitrogen atmosphere using standard Schlenk techniques.…”

“…Interpretation of the 1 H, 13 C and 31 P NMR patterns of 7 was further frustrated by the lack of a detailed assignment of the 1 H and 13 C NMR spectra in complexes where the PCP-type ligand had phenyl groups attached to the phosphorus atoms, [8] mainly those with geometries other than square-planar. [2,3,5,9,10] In particular, a detailed understanding of the binding mode of the HϪPCHP ligand in 7 requires an accurate assignment of the aromatic region of the 1 H and 13 C NMR spectra of related complexes such as 1؊3. Furthermore, these PCP metal complexes have an increasing importance as novel catalysts [8b,8c,11Ϫ13] as well as materials with interesting new physico-chemical properties.…”

“…N, P, S) and an anionic carbon atom usually from an aryl fragment. Examples of this type of complexes, containing a bis-orthochelating amine [1] or phosphane, [2,3] aryl monoanion (commonly known as a ''pincer'' ligand) bound to a ruthenium(II) center, are presented in Scheme 1.…”