Synthesis and Characterization of Ir-(κ2-NSi) Species Active toward the Solventless Hydrolysis of HSiMe(OSiMe3)2

The reaction of [IrH(Cl)(κ2-NSitBu2)(coe)] (1) with 1 equiv of PCy3 (or PHtBu2) gives the species [IrH(Cl)(κ2-NSitBu2)(L)] (L = PCy3, 2a; PHtBu2, 2b), which reacts with 1 equiv of AgOTf to afford [IrH(OTf)(κ2-NSitBu2)(L)] (L = PCy3, 3a and PHtBu2, 3b). Complexes 2a, 2b, 3a, and 3b have been characterized by means of NMR spectroscopy and HR-MS. The solid-state structures of complexes 2a, 2b, and 3a have been determined by X-ray diffraction studies. The reversible coordination of water to 3a, 3b, and 4 to afford the corresponding adduct [IrH(OTf)(κ2-NSitBu2)(L)(H2O)] (L = PCy3, 3a-H2O; PHtBu2, 3b-H2O; coe, 4-H2O) has been demonstrated spectroscopically by NMR studies. The structure of complexes 3b-H2O and 4-H2O have been determined by X-ray diffraction studies. Computational analyses of the interaction between neutral [NSitBu2]• and [Ir(H)L(X)]• fragments in Ir-NSitBu2 species confirm the electron-sharing nature of the Ir–Si bond and the significant role of electrostatics in the interaction between the transition metal fragment and the κ2-NSitBu2 ligand. The activity of Ir-(κ2-NSitBu2) species as catalysts for the hydrolysis of HSiMe(OSiMe3)2 depends on the nature of the ancillary ligands. Thus, while the triflate derivatives are active, the related chloride species show no activity. The best catalytic performance has been obtained when using complexes 3a, with triflate and PCy3 ligands, as a catalyst precursor, which allows the selective obtention of the corresponding silanol.


■ INTRODUCTION
Silicones and siloxanes market reached a value of US$ 15.1 billion and US$ 8.8 billion in 2020, and despite the COVID-19 crisis, a continuous growth of ca.7.5% is expected by 2026. 1 In this context, the development of catalytic processes that use siloxanes as raw materials gains importance.Among them, hydrosiloxanes, which are obtained as side-products in the silicone industry, stand out because they have proven to constitute a cheap and easy-to-handle alternative to hydrosilanes as reducing and silylating agents. 2 One of the simplest applications of hydrosiloxanes is their catalytic hydrolysis, which allows production of hydrogen and silanols.The latter are not stable, and under the reaction conditions, they typically react with the Si−H bond of another hydrosiloxane molecule to give higher-molecular-weight siloxanes and hydrogen (Scheme 1). 3 The development of catalysts for the selective hydrolysis of hydrosiloxanes to give hydrogen and the corresponding silanol is of great interest.However, while several examples of transition-metal-based homogeneous catalysts (Cr, 4 Re, 5 Fe, 6 Ru, 7 Rh, 8 Ir, 9 Cu, 10 Ag, 11 Au, 12 and Zn 13 ) effective for the hydrolysis of organosilanes have been reported, the catalytic hydrolysis of the Si−H bond in hydrosiloxanes remains challenging.9c The first requirement that a hydrolysis catalyst must meet is to be stable in the presence of water, that is, the catalyst must not hydrolyze.This is a challenge when using transition metal catalysts with silyl-based ligands.In this regard, it should be noted that while metal-silicon bonds in late transition metal-silyl complexes are easily hydrolyzed, the reactivity with water of such bonds in transition metal compounds with κ 3 -ESiE-type (E = P 14 and N 15 ) pincer ligands is hindered and requires the presence of a base.Earlier examples of the reactivity of transition metal-(κ 3 -ESiE) complexes with water were reported by Stobart et al. in  2001. 16They described that the ruthenium(II) complex [RuH(PSiP Ph )(CO) 2 ] (PSiP Ph = mer-κ 3 -P,Si,P-Si(Me)-{(CH 2 ) 3 PPh 2 } 2 ) did not react with water at 100 °C, being necessary to heat its solutions in wet piperidine at 100 °C for 17 h to achieve the formation of the ruthenium-siloxyde complex [RuH(POP Ph )(CO)(piperidine)] (POP Ph = mer-κ 3 -P,O,P-OSi(Me){(CH 2 ) 3 PPh 2 } 2 ), which decomposes upon isolation but reacts in situ with CO or P(OMe) 3 to give the corresponding [RuH(POP Ph )(CO)(L)] (L = CO or P-(OMe) 3 ) species (Scheme 2). 16ome years later, Turculet et al. described that the addition of water to the ruthenium(II) complexes [Ru(X)(PSiP Cy )] (PSiP Cy = fac-κ 3 -P,Si,P-Si(Me){PCy 2 (C 6 H 4 )} 2 ; X = O t Bu and N(SiMe 3 ) 2 ) did not affect the Ru−Si bond but produced the protonolysis of the corresponding Ru−X bond to afford the dinuclear hydroxo-bridged species [{Ru(PSiP Cy )}(μ-OH) 2 ] (Scheme 3). 17la et al. have studied the reactivity of Ir-(κ 3 -P,Si,P-PSiP) species with water.They have found that the reaction outcome strongly depends on the nature of the PSiP ligand.Thus, while the complex [IrH(Cl)(PSiP Ph )] reacts with MeOTf and water to give the complex [IrH(OTf)(POP Ph )], 18 under the same reaction conditions, the Ir−Si bond in the related species [IrH(OTf)(PSiP iPr )] (PSiP iPr = mer-κ 3 -P,Si,P-Si(Me){P-( i Pr) 2 (C 6 H 4 )} 2 ) is stable.Indeed, under these conditions, the reversible coordination of two molecules of water to afford the complex [IrH(PSiP iPr )(H 2 O) 2 ][OTf] is observed (Scheme 4). 19n contrast with κ 3 -PSiP ligands, which are commonly bonded to transition metals in a meridional (mer) coordination mode, monoanionic κ 3 -NSiN ligands prefer to coordinate to late transition metal complexes in a fac-κ 3 -(N,Si,N)-tridentate coordination mode, with the metal in a pseudo-octahedral geometry. 15Examples of the hydrolysis of the metal-silicon bond in metal-(κ 3 -N,Si,N-NSiN) species have not been reported so far. 1 H and 29 Si NMR studies on the catalytic generation of hydrogen by hydrolysis of hydrosilanes using the Ir(III) complex [Ir(H)(OTf)(NSiN)(coe)] (NSiN = fac-κ 3 -(N,Si,N)-bis(pyridine-2-yloxy)methylsilyl and coe = cyclooctene) as a catalyst precursor did not evidence the hydrolysis of the Ir−Si bond.9c The low reactivity with water of this type of complexes becomes an advantage for their use as catalysts for the hydrolysis of hydrosilanes.The performance of Ir-{facκ 3 -(N,Si,N)-NSiN} species as catalysts for the hydrolysis of hydrosilanes is strongly dependent on the reaction solvent, and the best activities were obtained in THF.9c The highest activities were reported for Et 2 SiH 2 (TOF 1/2 = 107,140 h −1 ) and (Me 2 HSi) 2 O (TOF 1/2 = 96,770 h −1 ), whereas the lowest one was found for HSiMe(OSiMe 3 ) 2 (TOF 1/2 = 130 h −1 ).9c The activity trend shown in Scheme 5 has been attributed to the steric hindrance around the Si−H bond.

Inorganic Chemistry
catalysts for the solventless hydrolysis of hydrosiloxanes.In addition, the bonding situation in the novel species was analyzed in detail by means of density functional theory (DFT) calculations.
The structures proposed for 2a, 2b, and 3a in Scheme 6 have been confirmed by single-crystal X-ray diffraction.Selected geometrical parameters, describing the metal coordination sphere, are reported in Table 1.
As illustrated in Figures 1 and 2 and pointed out in Table 1, the geometry of the metal coordination sphere of pentacoordinate complexes 2a, 2b, and 3a depends on the phosphine ligand.On one hand, in complexes 2a and 3a, with bulkier PCy 3 , the coordination of the κ 2 -NSi tBu2 ligand through the N and Si atoms, together with that of the phosphorous, the hydride and a chloride (2a) or an oxygen atom of a triflate ligand (3a) leads to a square pyramidal geometry around the iridium atom, with a silicon atom in the apical position and the chloride (2a) or the oxygen atom of the triflate ligand (3a) located trans to the hydride.Geometry indexes for these compounds are τ =0.03 and 0.19 for 2a and 3a, respectively (τ = 0 and τ = 1 correspond to ideal square pyramidal and trigonal bipyramidal). 23Interestingly, in both crystal structures, a hydrogen atom of a cyclohexyl ring (H32A) directly points toward the lone pair of the metal.
On the other hand, complex 2b exhibits an intermediate situation between a square pyramidal geometry and a distorted trigonal bipyramidal iridium atom with nitrogen and the phosphorous atoms at apical positions and equatorial sites  (2.4921(11) and 2.6073(1) Å) are longer than those found in complex 3a (2.2355( 14) Å) where the trans effect of the hydride is evident, but they are also longer than those reported in related complexes where oxygen is trans to silicon, as in [Ir(μ-OTf)(κ 2 -NSi Me2 ) 2 ] 2 dinuclear complex (2.3653(12) and 2.4331(13) Å) 20b or in species [Ir(CF 3 CO 2 )(κ 2 -NSi Me2 ) 2 ] (2.363(3) and 2.418(3) Å). 20a The coordinated water molecule in 3b-H 2 O and 4-H 2 O is placed trans to the hydride ligand.Both hydrogen atoms of the water molecule establish hydrogen bond interactions with the oxygen atoms of the triflate ligands, whose geometrical parameters are reported in Table 3.In the 3b-H 2 O crystal, these interactions form a symmetric R 2 2 (8) pattern, 24    show the coalescence at 273 K (T c ), below T c , and an equilibrium between two unequally populated species is observed (Figure S31).
The 19  show a resonance at δ −78.6 at 298 K that broadens as the temperature decreases; below 253 K, the signal splits into two clearly different peaks at δ −78.7 and −79.2 ppm (ratio: 1.00:0.58),corresponding to Ir−OTf and free − OTf, respectively (Figure 5).Cooling the sample to 193 K produces not only a slight high-field shifting of the two signals to δ −78.9 and −79.4 ppm, respectively but also a population change (ratio: 1.00:0.77).These results suggest that in the case of complex 3a-H 2 O, probably due to the high steric demand of the PCy 3 ligand, a triflate ligand dissociation/coordination equilibrium also takes place.
The chemical shift variations with temperature observed in the 1 H, 19 F, and 29 Si NMR spectra of CD 2 Cl 2 solutions of species 4-H 2 O and 3b-H 2 O are not significant, and Inorganic Chemistry consequently, these data were not suitable to study the equilibria 4 ⇆ 4-H 2 O and 3b ⇆ 3b-H 2 O. Fortunately, the 31 P{ 1 H} NMR spectra of 3b-H 2 O (CD 2 Cl 2 ) show a greater chemical shift variation with temperature, and therefore, these data were used to calculate the ΔH°(−3.45± 0.35 kcal mol −1 ), ΔS°(−1.47 ± 0.15 cal mol −1 K −1 ), and ΔG°2 98 (−3.01 ± 0.30 kcal mol −1 ) values for the 3b ⇆ 3b-H 2 O equilibrium, accordingly to the fast exchange equations. 25,26he ΔG ‡ values for the interconversion 3a ⇆ 3a-H 2 O have been calculated using the Ir−H resonances in the 1 H NMR spectra and the equations for the interconversion between two unequally populated species 27 where T c is the coalescence temperature (273 K).The difference of populations between 3a and 3a-H 2 O (ΔP) at 193 K is 0.16, and the value of Δν, which is the difference between the two studied resonances in Hz, at 193 K is 729 Hz.The parameter X can be obtained from the equation ΔP = [(X 2 − 2)/3] 3/2 × 1/ X, and for ΔP = 0.16 is 1.8218. 28Thereby, the ΔG ‡ A and ΔG ‡ B values were calculated as 12.6 and 12.4 kcal mol −1 , respectively.
These results show that the coordination of the water molecule to the iridium atom in complexes 3a, 3b, and 4 to give the corresponding adduct depends on the temperature, being preferred at low temperatures.Accordingly, none of the aquo complexes 3a-H 2 O, 3b-H 2 O, or 4-H 2 O could be isolated at a preparative scale and even using an excess of water; the starting products are obtained after the workup.
Computational Studies on the Ir−Si and Ir−OTf Bonds.The remarkable stability of the Ir−Si bond in complexes 1−3 prompted us to investigate the nature of the Ir−Si bond in detail by means of computational tools at the relativistic and dispersion-corrected ZORA-BP86-D3/TZ2P// BP86-D3/def2-SVP level (see computational details in the Supporting Information).To this end, we applied state-of-theart methods based on the natural bond orbital (NBO) and energy decomposition analysis-natural orbital for chemical valence (EDA-NOCV) methods on the representative 1, 3b, and 4 complexes as well as on their corresponding H 2 O complexes.
Similar to the slightly related [Ir(H)(X)(NSiN)(coe)] (X = Cl and OTf) complexes, 29 the bonding situation in the considered [IrH(X)(κ 2 -NSi tBu2 )(L)] (X = Cl and OTf; L = coe, PCy 3 , and PH t Bu 2 ) species is best described as possessing a dative LP(N) → Ir bond (where LP(N) refers to the nitrogen lone pair) and a covalent (i.e., electron-sharing) Ir−Si bond.Indeed, the NOCV approach confirms the occurrence of three main orbital interactions in these species, namely, the covalent σ−Ir−Si bond (denoted as ρ 1 , Figure 6), the dative bond involving the donation from the lone-pair of the pyridine nitrogen atom to a vacant d atomic orbital of the transition metal (denoted as ρ 2 ), and the π-backdonation from a doubly occupied d atomic orbital of the iridium center to a vacant p π (Si) atomic orbital of the silicon atom (denoted as ρ 3 , Figure 6).Consistent with the data in Table 4, which gathers the   29 The remarkable long Ir•••OTf distance observed in the solid state of the aquo-complexes 3b-H 2 O and 4-H 2 O (2.4921(11) and 2.6073(1) Å, respectively) poses the question of whether there is indeed an interaction between the transition metal and the oxygen atom of the triflate ligand or the complexes are better described as ion pairs therefore dominated by    31 and the shortest value found for an interaction (3.606 Å in carbonyl-(pyridine)-bis(tris-(biphenyl-4-yl)phosphine)Ir OTf). 32oreover, our gas-phase calculations on 3b-H 2 O as a representative triflate complex concur quite well with the experiment and nicely reproduce the observed long Ir•••OTf distance (2.427 Å).This long bond distance is translated into a WBI of 0.09, which is much lower than that computed for its non-aquo complex counterpart 3b (0.20, 2.216 Å).Our EDA-NOCV calculations indicate that the [Ir] + •••(OTf) − interaction is mainly electrostatic as the ΔE elstat term contributes ca.65% to the total attractive interactions (ΔE elstat + ΔE orb + ΔE disp ) between the [Ir] + and (OTf) − fragments (see Table 4).Despite that, the orbital term (ΔE orb ) is not negligible (contributing ca.26% to the total bonding) and is mainly dominated by the dative bond involving the donation from the lone pair of the oxygen atom of the triflate to a vacant d atomic orbital of the transition metal.Therefore, it can be concluded that complex 3b-H 2 O presents an intermediate situation between an ion pair and a standard donor−acceptor complex.
In all the cases, the catalytic reactions were performed in a microreactor and monitored by measuring the hydrogen pressure generated during the hydrolysis processes.The resulting liquid residues were studied by 1 H and 29 Si NMR spectroscopy to identify the Si-containing reaction products.These studies confirm that 3a (TOF 1/2 = 284 h −1 ) is more active catalyst than 3b (TOF 1/2 = 190 h −1 ) and 4 (TOF 1/2 = 84 h −1 ) for the generation of H 2 from the hydrolysis of HSiMe(OSiMe 3 ) 2 at 323 K (Figure 8).
The activity of the 3a as a catalyst for the solventless hydrolysis of HSiMe(OSiMe 3 ) 2 depends on the reaction temperature.The best activity has been found at 353 K (TOF 1/2 = 2000 h −1 ).This value is the highest catalytic activity so far reported for a catalytic solventless hydrolysis of HSiMe(OSiMe 3 ) 2 .Moreover, while at 353 K, the catalytic system does not require an activation period; at 323 and 298 K, activation periods of around 7 and 56 min were required, respectively (Figure 9).However, at 353 K, a decrease in selectivity is observed and a mixture of the silanol HOSiMe-(OSiMe 3 ) 2 (88 mol %) and the siloxane O{SiMe(OSiMe 3 ) 2 } 2 (12 mol %) was obtained.
1 H- 29 Si HMBC NMR studies of the oily product obtained from the 3a-catalyzed hydrolysis of HSiMe(OSiMe 3 ) 2 show that along with the signals due to the reaction product, HOSiMe(OSiMe 3 ) 2 , a distinct signal appears corresponding to the correlation of a singlet at δ 1.04 ppm in 1 H NMR due to the Si-t Bu 2 protons, with a resonance that appears at δ −7.7 ppm in the 29 Si{ 1 H} NMR spectra.This value is upper-field shifted with respect to the value of around δ 43−45 ppm found for the Ir−Si bond in Ir-(κ 2 -NSi tBu2 ) species and δ 12.0 ppm reported for the ligand precursor. 22This observation allows us to conclude that catalyst deactivation involving hydrolysis of the Ir−Si bond takes place during the catalytic reaction.Accordingly, when an extra 1.0 mmol of HSiMe(OSiMe 3 ) 2 is added to the reactor at 323 K, a clear decrease in activity is observed.Indeed, it was only possible to achieve the hydrolysis of the 80% of the starting hydrosiloxane before catalyst deactivation (Figure S41).
To explore the scope of the reaction, we have also studied the potential of 3a as a catalyst for the hydrolysis of HSi(OSiMe 3 ) 3 .The results of these studies show that in the presence of catalytic amounts of 3a (0.5 mol %) at 323 K, the addition of 10 μL of H 2 O to HSi(OSiMe 3 ) 3 did not produce evolution of gas.Heating at 353 K, a very slow generation of H 2 was observed.These results suggest that the greater steric protection of the Si−H bond in HSi(OSiMe 3 ) 3 hinders its hydrolysis.

■ CONCLUSIONS
The reaction of the iridium(III) complex [Ir(Cl)(κ 2 -NSi tBu2 )-(coe)] ( 1 The results of our computational (EDA-NOCV) analysis of the interaction between neutral [NSi tBu2 ] • and [Ir(H)L(X)] • fragments in Ir-NSi tBu2 species show that the covalent (i.e., electron-sharing) Ir−Si bond is almost three times stronger than the dative LP(N) → d(Ir) bond, while the πbackdonation (ρ 3 ) is comparatively much weaker.The coordination of the water molecule produces a slight weakening of the Ir−Si bond.In all the studied cases, it becomes evident that the replacement of the chloride ligand by OTf leads to stronger Ir−Si bonds due to its higher electronwithdrawing character, which further polarizes the Ir−Si bond.
The activity of Ir-(κ 2 -NSi tBu2 ) species as a catalyst for the hydrolysis of HSiMe(OSiMe 3 ) 2 depends on the nature of the ancillary ligands.Thus, while the triflate derivatives are active, the related chloride species show no measurable activity.The best catalytic performance has been obtained when using complexes 3a, with triflate and PCy 3 ligands, as catalyst precursors at 323 K, which allows the selective obtention of the corresponding silanol (TOF 1/2 = 284 h −1 ).NMR studies confirm that the hydrolysis of the Ir−Si bond in 3a during the process results in the deactivation of the catalyst.
Single-Crystal Structure Determination.X-ray diffraction data were collected on an APEX DUO (compound 2b and 4-H 2 O) and D8 VENTURE (compounds 2a, 3a, and 3b-H 2 O) Bruker diffractometers, using graphite-monochromated Mo Kα radiation (λ = 0.71073 Å).Single crystals were mounted on a fiber or a MiTeGen support coated with protecting perfluoropolyether oil and cooled to 100(2) K with open-flow nitrogen gas.Data were collected using ω scans (and φ scans in compounds 2a, 3a, and 3b-H 2 O data collection) with narrow oscillation frame strategies.Diffracted intensities were integrated and corrected of absorption effects by using multiscan method using SAINT 34 and SADABS 35 programs included in APEX4 packages.Structures were solved by direct methods with SHELXS 36 and refined by full-matrix least squares on F 2 with the SHELXL program 37 included in the Wingx program system. 38

Inorganic Chemistry
Hydrogen atoms have been observed in Fourier difference maps.Most of them have been included in the models in calculated positions and refined with a riding model.Several strategies, adapted to data and structural model, have been applied to locate and refine hydride ligands.It has been included in the model in observed position and freely refined for compounds 2a, 3b-H 2 O, and refined with a restrain in the Ir−H bond length in 4-H 2 O structure refinement.For compounds 2b and 3a, the position of the hydride has been located with potential energy minimization with HYDEX program. 39The hydride position has been fixed (2b) or refined with a restraint in the Ir−H bond (3a).
Structural Data for 2a.CCDC-2177342-2177346 contains the supplementary crystallographic data for this paper.These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Computational Details.Geometry optimizations of the complexes were performed without symmetry constraints using the Gaussian09 40 energies and gradients at the BP86 41 /def2-SVP 42 level of theory using the D3 dispersion correction suggested by Grimme et al. 43 Vibrational analysis was performed to ensure that the optimized geometry corresponds to an energy minimum.NBO calculations were carried out using the NBO6.0 program 44 at the BP86-D3/def2-SVP level.
The interaction ΔE int between the selected fragments is analyzed with the help of the EDA method. 45Within this approach, ΔE int can be decomposed into the following physically meaningful terms: The term ΔE elstat corresponds to the classical electrostatic interaction between the unperturbed charge distributions of the deformed reactants and is usually attractive.The Pauli repulsion ΔE Pauli comprises the destabilizing interactions between occupied orbitals and is responsible for any steric repulsion.The orbital interaction ΔE orb accounts for electron-pair bonding, charge transfer (interaction between occupied orbitals on one moiety with unoccupied orbitals on the other, including HOMO−LUMO interactions), and polarization (empty-occupied orbital mixing on one fragment due to the presence of another fragment).Finally, the ΔE disp term takes into account the interactions, which are due to dispersion forces.Moreover, the NOCV 46 extension of the EDA method has been also used to further partition the ΔE orb term.The EDA-NOCV approach provides pairwise energy contributions for each pair of interacting orbitals to the total bond energy.
The program package AMS 2020.101 47was used for the EDA-NOCV calculations at the same BP86-D3 level, in conjunction with a triple-ζ-quality basis set using uncontracted Slater-type orbitals (STOs) augmented by two sets of polarization functions with a frozen-core approximation for the core electrons. 48Auxiliary sets of s, p, d, f, and g STOs were used to fit the molecular densities and to represent the Coulomb and exchange potentials accurately in each SCF cycle. 49Scalar relativistic effects were incorporated by applying the zeroth-order regular approximation (ZORA). 50This level of theory is denoted ZORA-BP86-D3/TZ2P//BP86-D3/def2-SVP.
Additional experimental details, NMR data, and methods and Cartesian coordinates of computed structures (PDF) Scheme 2 (2.4015(3) Å, 2a and 2.3902(4) Å, 2b) bond lengths compare well with the values 2.2853(6) Å and 2.3950(6) Å reported for 1,22 respectively.Geometrical parameters of the coordination of the bidentate (κ 2 -NSi tBu2 ) fragment and the phosphano ligands to the metal in 3a nicely agree with those observed for complexes 2a and 2b.Addition of Water to [IrH(X)(κ 2 -NSi tBu2 )(L)] (X = Cl and OTf; L = Coe, PCy 3 , and PH t Bu 2 ).While the 1 H NMR spectra of solutions of the Ir-chloride derivatives 1, 2a, and 2b in CD 2 Cl 2 (298 K) do not show detectable changes after the addition of water (10 μL), those of the related Ir-triflate complexes 4, 3a, and 3b evidenced a shift in most of the resonances, which is significant for the signals due to the Ir−H moiety.In particular, in the 1 H NMR (CD 2 Cl 2 ) spectra, they appear shifted downfield from δ −27.39 to −25.82 ppm (4), from δ −29.75 to −29.08 (3a), and from δ −29.71 to −28.98 (3b) (Figures S27−S29).Moreover, the serendipitous obtention of single crystals from wet C 6 D 6 and pentane solutions of 4 and 3b, respectively, allowed us to determine the solid-state structure of the water adducts and 3b-H 2 O and 4-H 2 O (Figure 3).In complexes 3b-H 2 O and 4-H 2 O, the metal atom exhibits a distorted pseudo-octahedral geometry with nitrogen, oxygen atom of water, hydride, and phosphorous (3b-H 2 O) or the olefinic bond of coe ligand (4-H 2 O) in the equatorial plane, while apical positions are fulfilled by silicon and an oxygen atom of the triflate ligand.The Ir−Si bonds (2.2835(5), 2.2876(4), and 2.2915(6) Å in 3a, 3b-H 2 O, and 4-H 2 O, respectively) (Table 2) are comparable to those found in complexes 1, 2a, and 2b, while the trans-located Ir•••O bonds in 3b-H 2 O and 4-H 2 O are found to be significantly elongated.These Ir−O triflate bond lengths in 3b-H 2 O and 4-H 2 O relative orientation of coordinated water and triflate ligand in the solid-state structure of 4-H 2 O leads to the formation of intermolecular O−H•••O triflate interactions, forming an R 2 4 (8) pattern, as depicted in Figure 4.The above-described results encouraged us to further study the reactivity of the Ir-triflate derivatives 3a, 3b, and 4 with water. 1 H NMR spectra of CD 2 Cl 2 solutions of complexes 3a-H 2 O, 3b-H 2 O, and 4-H 2 O are temperature-dependent (Figures S30−S35).In all the cases, a reversible shift of the signals was observed in the 1 H NMR spectra with decreasing

Figure 1 .
Figure 1.Molecular structures of complexes 2a and 2b.Hydrogen atoms (except hydrides) have been omitted for clarity.

Figure 2 . 1 H
Figure 2. Molecular structure of complex 3a.Hydrogen atoms (except hydride) have been omitted for clarity.

Figure 6 .
Figure 6.NOCV-deformation densities and associated stabilization energies computed for complex 4. The charge flow takes place in the direction red → blue.

Figure 7 .
Figure 7. Histogram of the statistical analysis of Ir−O distances in Ir−OTf fragments.Results for searches 1 and 2 are depicted in blue and orange, respectively.The Ir•••O distances found in 3b-H 2 O and 4-H 2 O complexes are indicated by arrows.