Coordinatively Unsaturated Ruthenium Phosphine Half-Sandwich Complexes:  Correlations to Structure and Reactivity

Abstract

A number of 16e two-legged piano-stool complexes [Cp*Ru(PP)][BAr‘4] have been prepared by reaction of NaBAr‘4 with either [Cp*RuCl(PP)] (PP = (PEt3)2, iPr2PCH2CH2PiPr2 (dippe), (PPh3)2) or [Cp*RuCl(PR3)] plus PR3 (PR3 = PMeiPr2, PPhiPr2) in fluorobenzene under argon. The complexes [Cp*Ru(PEt3)2][BAr‘4], [Cp*Ru(dippe)][BAr‘4], and [Cp*Ru(PMeiPr2)2][BAr‘4] have been structurally characterized by X-ray crystallography. Attempts to isolate analogous species containing other phosphine ligands such as PiPr3, PCy3, and PMe3 led to the sandwich derivative [Cp*Ru(η6-FPh)][BAr‘4], which was also structurally characterized. Both [Cp*Ru(PPh3)2][BAr‘4] and [Cp*Ru(PPhiPr2)2][BAr‘4] are unstable and rearrange to the 18e sandwich species [Cp*Ru(η6-C6H5PR2)][BAr‘4] and to [Cp*Ru(η6-C6H5POR2)][BAr‘4] (R = Ph, iPr) under trace amounts of oxygen. The geometry of the 16e complexes as well as their affinity for an additional ligand depend on the substituents on the phosphorus. The reactivity with respect to the addition of N2, PR3, O2, H2, and HCl to form 18e derivatives has been studied. Some model systems have been analyzed using density functional theory (DFT) calculations. Also included are comparative studies on the NN counterparts. The moieties [CpRu(PP)]+ (PP = (PH3)2, H2PCH2CH2PH2) adopt typically pyramidal structures (i.e. in the absence of bulky and rigid substituents on P) versus planar structures of [CpRu(NN)]+ (NN = (NH3)2, H2NCH2CH2NH2). [CpRu(PP)]+ is more stable but has nevertheless a higher affinity of adding a σ ligand than [Cp*Ru(NN)]+.

Ruthenium (II) complexes of the chelating phosphine borane H2ClB·dppm

“…D 2 oxidatively adds to the Ru(II) centre in 1, presumably initially through a dihydrogen adduct with a g 1 -borane ligand. Oxidative addition of H 2 to ruthenium (II) cyclopentadienyl phosphine complexes is known to form dihydride complexes such as ½RuCp à H 2 ðP i Pr 3 Þ 2 ½BAr F 4 [24]. Breaking a B-H bond and making a B-D bond (similar to the exchange process observed in borohydride complexes such as OsH 3 (g 2 -BH 4 )(PR 3 ) 2 [25]) effects H/D exchange.…”

Structure and Reactivity of Coordinatively Unsaturated Half‐Sandwich Iron, Ruthenium and Osmium Complexes

“…[81,82] Complexes stabilized by bonding to CϭC bonds of either aryl or biarylphosphane group (Figure 15 and 16) display pyramidalization angles of 155Ϫ157°, consistent with their coordinatively saturated character. Extended Hückel [73,78,79] and DFT [73,82] (Figure 17). The TSC concept has also been applied recently to the MO analysis of [CpRu(L) 2 ] ϩ complexes.…”

“…The first stable compounds of the type [Cp*Ru(P) 2 ] ϩ were unequivocally characterized and recently reported by our research group. [81,82] The complex [Cp*Ru(PMe- (Figure 12) was prepared by reaction of [Cp*-RuCl(PMeiPr 2 )] [29] with NaBArЈ 4 in fluorobenzene under argon in the presence of PMeiPr 2 , whereas the derivatives [Cp*Ru(dippe)][BArЈ 4 ] ( Figure 13) and [Cp*Ru(PEt 3 ) 2 ]-[BArЈ 4 ] were similarly obtained by chloride abstraction from either [Cp*RuCl(dippe)] [9] or [Cp*RuCl(PEt 3 ) 2 ] [83] using NaBArЈ 4 in fluorobenzene under argon. Although this seems to be a general reaction for the preparation of cationic 16-electron half-sandwich ruthenium complexes, the range of stable compounds of this type amenable to isolation is in fact very limited.…”

“…In contrast, the model amine complexes adopt essentially planar structures (α ϭ 171Ϫ179°), with an almost flat inversion barrier. [82] It must be noted, however, that bending is hampered by bulky L 2 ligands, and the reactivity of the fragment is modified accordingly. Amine ligands participate much less than phosphane ligands in the LUMO, and this participation is further increased on bending.…”

“…[10,29,82] With the exception of the reaction with HCl, the amine complexes [(C 5 system for computation using a combination of DFT and quantum mechanics/molecular mechanics calculations. [97] Whereas the solid-state structures determined by X-ray crystallography for several alkynyl hydrido complexes show a transoid disposition of alkynyl and hydrido ligands (Figure 18 SO 3 ].…”