A homologous family of low‐coordinate complexes of the formulation trans‐[M(2,2′‐biphenyl)(PR3)2][BArF 4] (M=Rh, Ir; R=Ph, Cy, iPr, iBu) has been prepared and extensively structurally characterised. Enabled through a comprehensive set of solution phase (VT 1H and 31P NMR spectroscopy) and solid‐state (single crystal X‐ray diffraction) data, and analysis in silico (DFT‐based NBO and QTAIM analysis), the structural features of the constituent agostic interactions have been systematically interrogated. The combined data substantiates the adoption of stronger agostic interactions for the IrIII compared to RhIII complexes and, with respect to the phosphine ligands, in the order PiBu3>PCy3>PiPr3>PPh3. In addition to these structure–property relationships, the effect of crystal packing on the agostic interactions was investigated in the tricyclohexylphosphine complexes. Compression of the associated cations, through inclusion of a more bulky solvent molecule (1,2‐difluorobenzene vs. CH2Cl2) in the lattice or collection of data at very low temperature (25 vs. 150 K), lead to small but statistically significant shortening of the M−H−C distances.

We report the synthesis of the U(III) bis(cyclopentadienyl) hypersilanide complex [U(Cp′′)2{Si(SiMe¬3)3}] (Cp′′ = {C5H3(SiMe3)2-1,3}), together with isostructural lanthanide and group 4 M(III) homologues, in order to meaningfully compare metal-silicon bonding...

In the context of advancing the use of metal-based building blocks for the construction of mechanically interlocked molecules, we herein describe the preparation of late transition metal containing [2]rotaxanes (1). Capture and subsequent retention of the interlocked assemblies are achieved by the formation of robust and bulky complexes of rhodium(iii) and iridium(iii) through hydrogenation of readily accessible rhodium(i) and iridium(i) complexes [M(COD)(PPh)][BAr] (M = Rh, 2a; Ir, 2b) and reaction with a bipyridyl terminated [2]pseudorotaxane (3·db24c8). This work was underpinned by detailed mechanistic studies examining the hydrogenation of 1 : 1 mixtures of 2 and bipy in CHCl, which proceeds with disparate rates to afford [M(bipy)H(PPh)][BAr] (M = Rh, 4a[BAr], t = 18 h @ 50 °C; Ir, 4b[BAr], t < 5 min @ RT) in CHCl (1 atm H). These rates are reconciled by (a) the inherently slower reaction of 2a with H compared to that of the third row congener 2b, and (b) the competing and irreversible reaction of 2a with bipy, leading to a very slow hydrogenation pathway, involving rate-limiting substitution of COD by PPh. On the basis of this information, operationally convenient and mild conditions (CHCl, RT, 1 atm H, t ≤ 2 h) were developed for the preparation of 1, involving in the case of rhodium-based 1a pre-hydrogenation of 2a to form [Rh(PPh)][BAr] (8) before reaction with 3·db24c8. In addition to comprehensive spectroscopic characterisation of 1, the structure of iridium-based 1b was elucidated in the solid-state using X-ray diffraction.

The synthesis and characterisation of a homologous series of rhodium 2,2′‐biphenyl complexes featuring intramolecular dative bonding of the nominally inert and weakly coordinating trifluoromethyl group are described. Presence of these interactions is evidenced in the solid state using X‐ray diffraction, with Rh−F contacts of 2.36–2.45 Å, and in solution using NMR spectroscopy, through hindered C−CF 3 bond rotation and the presence of time‐averaged 1 J RhF and 2 J PF coupling.