Multiple Bond Character Research Articles

(Eta5-cyclopentadienyl)(p-fluorophenoxo)(nitrosyl)(trimethylsilylmethyl)molybdenum(II).

The title complex, [Mo(C(5)H(5))(C(6)H(4)FO)(C(4)H(11)Si)(NO)], is formed by reacting CpMo(NO)(CH(2)SiMe(3))(2), where Cp is cyclopentadienyl, with one equivalent of p-FC(6)H(4)OH. The complex exhibits the expected piano-stool molecular structure, with a linear nitrosyl ligand [Mo-N-O 168.2(2) degree] having Mo-N and N-O distances of 1.764(2) and 1.207(3)A, respectively. The phenoxo Mo-O distance of 1.945(2)A is suggestive of some multiple-bond character.

Syntheses, vibrational spectra, and theoretical studies of the adamantanoid Sn(4)Ch(10)(4-) (Ch = Se, Te) anions: X-ray crystal structures of [18-crown-6-K](4)[Sn4Se10]*5en and [18-crown-6-K](4)[Sn4Te10]*3en*2THF.

The salts [18-crown-6-K](4)[Sn(4)Se(10)].5en and [18-crown-6-K](4)[Sn(4)Te(10)].3en.2THF were isolated upon addition of THF to the ethylenediamine (en) extracts of the alloys KSn(0.90)Se(1.93) and K(4)Sn(4)Te(10) that had been extracted in the presence of 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane). The Sn(4)Te(10)(4-) anion has been structurally characterized for the first time by a single-crystal X-ray diffraction study of [18-crown-6-K](4)[Sn(4)Te(10)].3en.2THF: P2(1)/n, a = 22.420(5) A, b = 19.570(4) A, c = 24.680(5) A, beta = 96.90(3)(o), Z = 4, and R(1) = 0.0468 at -183 degrees C. In addition to Si(4)Te(10)(4-) and Ge(4)Te(10)(4-), the Sn(4)Te(10)(4-) anion represents the only other known group 14 adamantanoid telluride. The X-ray crystal structure determination of the related [18-crown-6-K](4)[Sn(4)Se(10)].5en salt has also been determined: P2(1)/n, a = 22.003(2) A, b = 18.966(2) A, c = 24.393(2) A, beta = 97.548(8)(o), Z = 4, and R(1) = 0.0843 at -123 degrees C. The anion geometries are of the adamantanoid type where the Sn(IV) atoms occupy the bridgehead positions and the chalcogen atoms occupy the bridging and terminal sites. The energy minimized geometries of Sn(4)Ch(10)(4-) have also been determined using density functional theory (DFT). Mayer bond order analyses, Mayer valencies, and empirical bond valencies indicate that the terminal Sn-Ch bonds have significant multiple bond character, with the terminal Sn-Se bond having more multiple bond character than the terminal Sn-Te bond. The vibrational frequencies of the Sn(4)Se(10)(4-) and Sn(4)Te(10)(4-) anions have been calculated using DFT methods, allowing the Raman spectrum of Sn(4)Se(10)(4-) to be fully assigned.

Density-functional investigation of bonding in tetrahedral MO 4 anions

The structure and bonding in main-group and transition-metal oxoanions with MO 4 stoichiometry have been investigated by density-functional methods. Nine main-group (SiO 4 4− , PO 4 3− , SO 4 2− , ClO 4 − , GeO 4 4− , AsO 4 3− , SeO 4 2− , BrO 4 − , IO 4 − ) and ten transition-metal (TiO 4 4− , VO 4 3− , CrO 4 2− , MnO 4 − , NbO 4 3− , MoO 4 2− , TcO 4 − , TaO 4 3− , WO 4 2− , ReO 4 − ) oxoanions have been studied. For most species, the optimized geometry of the isolated molecule satisfactorily reproduces the experimental structural parameters in the crystalline phase. Mulliken charges have been calculated, and have been found to be, in all cases, significantly smaller than the formal oxidation states. Mayer bond-order indexes and the composition of the Kohn–Sham orbitals have been utilized for the analysis of bonding in the oxoanions. The former reveal some MO multiple-bonding character in all MO 4 systems, and are in good agreement with values determined from classical bond-valence analysis. The molecular-orbital analysis indicates that the chemical bonds possess Msp and Osp character in the main-group species, and Md and Op character in the transition-metal systems.

The origin of hindered rotation around the Pt-N bond in platinum amides.

Several platinum amides of formula trans-[PtCl(NHAr)(PEt(3))(2)] (Ar = 3-FC(6)H(4), 2; 4-FC(6)H(4), 3; 4-ClC(6)H(4), 4; 4-IC(6)H(4), 5; 4-Cl,3-NO(2)-C(6)H(3), 6) have been synthesized by reaction of [PtHCl(PEt(3))(2)] with aryl azides. All the complexes feature planar arylamido moieties and hindered rotation around the N-aryl and Pt-N bonds have been detected and separately studied. The X-ray crystal structures of complexes 5 and 6 have been determined. Complex 5 crystallizes in the orthorhombic space group Pnma, with a = 23.806(4) A, b = 15.099(2) A, c = 6.7593(10) A, alpha = beta = gamma = 90 degrees, and Z = 4. Compound 6 shows an N-H...O(NO) hydrogen bond and it crystallizes in the monoclinic space group P2(1)/n, with a = 12.215(3) A, b = 8.078(2) A, c = 13.052(4) A, alpha = gamma = 90 degrees, beta = 90.057(6) degrees, and Z = 2. Except for Ar = 4-Cl,3-NO(2)-C(6)H(3), the activation energies obtained for the complexes indicate that both dynamic processes occur simultaneously with a common barrier which originates in the multiple bond character of the N-aryl bond due to a strong pi-donor behavior of the N atom in the N-aryl bond. The rotation about the Pt-N bond is unfavorable because of steric congestion with the planar amide, which can be overcome only when the aromatic ring can rotate. For the complex trans-[PtCl[NH(4-Cl,3-NO(2)-C(6)H(3))](PEt(3))(2)] the barrier to rotation is mostly due to hydrogen bond interaction between the NO(2) ortho substituent and the amide H atom.

Evidence for multiple bonding in four-coordinate, cationic, platinumthiosilylenes via AIM and CDA; effects of phosphine choice

Abstract Hybrid DFT/HF calculations were performed on five complexes (PH 3 ) 2 (H)PtSi(SH) 2 + , (PH 3 ) 2 (H)PtSi(SMe) 2 + , (PMe 3 ) 2 (H)PtSi(SMe) 2 + , (P i Pr 3 ) 2 (H)PtSi(SEt) 2 + , and (PCy 3 ) 2 (H)PtSi(SEt) 2 + , and analyzed using CDA and Atoms-In-Molecules. Complexes were found to possess both SiS and SiPt multiple bond character, in contrast to earlier results at lower levels of theory. The origins of twisted geometries were determined to be primarily steric in nature. Increasing the size of aliphatic substituents on the phosphines leads to a more balanced bonding motif, but increases steric repulsion, while changing the substituent at silicon from hydrogen to methyl resulted in a lengthening of the SiPt bond. Based on these results, the use of PH 3 to substitute for PMe 3 and larger groups in calculations is discouraged, though methyl is an acceptable, if not electronically identical, substitute for larger aliphatic phosphines.

Schrock type transition metal complex formation of push–pull substituted phosphanyl-carbenes, a quantum chemical investigation by density-functional methods

The formation of coordination compounds of phosphanyl carbenes with a transition metal in a high oxidation state (Schrock type) is evaluated by density functional theory. In the Schrock type carbene complexes the transition metalcarbon bond possesses a multiple bond character. If one of the ligands at the carbene center possesses a leaving ability, e.g. as the diaminophosphenium unit, a facile distortion to a new type of an anionic metallaalkylidene donor-acceptor complex with a diaminophosphenium cation is predicted.

TcCl(CS)(dppe)2]·C6H6

The title compound, chlorobis[1,2-ethanediylbis(diphenylphosphine)-P,P′](thiocarbonyl-C)technetium benzene solvate, [TcCl(C46H42P4)(CS)]·C6H6, was obtained as one of two Tc-containing products isolated from the reaction between CS2and the electron-deficient complex [TcCl(dppe)2], where dppe is 1,2-ethanediylbis(diphenylphosphine). The structure exhibits an unusually short Tc—C distance [1.819 (6) Å], suggesting some multiple-bond character.

The first noncoordinated phosphonium diylide, [Me2P(C13H8)2]-, and its ylidic and cationic counterparts: synthesis, structural characterization, and interaction with the heavy group 2 metals.

Treatment of potassium or lithium fluorenide with MePCl2 generates the organophosphine MeP(C13H9)2, which on reaction with methyl iodide produces the phosphonium species [Me2P(C13H9)2]I in 74% yield. In the solid state, H...I contacts of < 3.3 A help generate a layered structure in which the fluorenyl rings are nearly parallel. On subsequent reaction of [Me2P(C13H9)2]I with either KH or K[N(SiMe3)2], the corresponding neutral phosphoylide, Me2P(C13H9)(C13H8), forms in 67% yield and was structurally characterized. The phosphonium iodide [Me2P(C13H9)2]I was allowed to react with Ae[N(SiMe3)2]2 (Ae = Ca, Ba), and the product from the reaction with the calcium complex was structurally identified as the salt [CaI(thf)5][Me2P(C13H8)2]. The anion, which is outside the coordination sphere of the calcium, represents the first structurally authenticated example of a free phosphonium diylide. The P-C(ylidic) bond length of 1.748(4) A reflects some partial multiple bond character. 1H and 31P NMR spectra suggest that the barium analogue is similar. Density functional theory calculations were performed on representative phosphonium diylides as an aid to interpreting the bonding in this class of compounds. Despite the strong electrostatic attraction that usually drives metal-ligand binding in highly ionic systems, calcium and barium prefer to coordinate to a single iodide ion and several neutral oxygen donors rather than to the charged diylide.

Reactions of the Binuclear Complexes [MIr(CO)3(Ph2PCH2PPh2)2] (M = Rh, Ir) with Alkyl Halides: Dramatic Reactivity Differences as a Function of Metal Combination and Alkyl Halide

Reactions of [Ir2(CO)3(dppm)2] (1; dppm = Ph2PCH2PPh2) with CH3I and CH3OCH2I give the oxidative-addition products [Ir2(R)(I)(CO)(μ-CO)(dppm)2] (R = CH3 (3), CH2OCH3 (4)). The X-ray structure determination of 4·CH2Cl2 shows that the alkyl group is the sole terminal ligand on one metal while the iodo and a carbonyl are terminally bound to the adjacent metal. The mixed-metal analogue [RhIr(CO)3(dppm)2] (2) does not react with CH3I but reacts with CH3OCH2I to give [RhIr(CH2OCH3)(I)(CO)(μ-CO)(dppm)2] (5). Reaction of 3 or 5 with methyl triflate results in iodide abstraction to yield the known compound [Ir2(CH3)(CO)(μ-CO)(dppm)2][CF3SO3] and [RhIr(CH2OCH3)(CO)(μ-CO)(dppm)2][CF3SO3] (8), respectively. In the mixed-metal compound iodide removal results in migration of the methoxymethyl group from Rh to Ir. Iodide abstraction from 4 results in a double C−H bond activation to yield the methoxycarbyne-bridged [Ir2(H)2(CO)2(μ-COCH3)(dppm)2][CF3SO3] (6). In the reactions of 4 and 5 with methyl triflate some methoxide abstraction also occurs, yielding the methylene-bridged products [MIr(CO)2(μ-CH2)(μ-I)(dppm)2][CF3SO3] (M = Ir (7), Rh (9)) as minor products in between 15 and 30% yield. The reactions of [MIr(CO)3(dppm)2] (M = Ir (1), Rh (2)) with CH2I2 and ICH2CN yield [MIr(CO)2(μ-I)(μ-CO)(Ph2PCHPPh2)(dppm)] (M = Ir (10), Rh (11)) together with CH3I and CH3CN, respectively, by hydrogen abstraction from one of the dppm ligands and iodine atom coordination at the metals. Reactions of 1 with allyl bromide and benzyl bromide yield the bromo analogue [Ir2(CO)2(μ-Br)(μ-CO)(Ph2PCHPPh2)(dppm)2] (12). The X-ray structure of 10·THF has been determined and shows a planar Ir−P−C(H)−P−Ir moiety, short P−C bonds (1.72(2) Å), and a 122(1)° angle at carbon of the Ph2PC(H)PPh2 ligand, as expected for sp2 hybridization and partial multiple-bond character in the P−C bonds.

Structure and energetics of SinNm clusters: Growth pathways in a heterogenous cluster system

We present a detailed study of the structures and energetics of SinNm clusters with n+m⩽6. We have determined the lowest-energy isomers of these clusters as a function of total cluster size and cluster stoichiometry. The properties of the low-energy isomers were calculated using an accurate, all-electron full-potential density-functional method at both the local density approximation (LDA) and the generalized gradient approximation (GGA) levels of theory. We found the most stable clusters by conducting an extensive phase space exploration for all the clusters containing up to 6 atoms, checking all bonding topologies and all possible atom type decorations. The search was done using a fast, but accurate, density-functional based tight-binding method. The calculations reveal several trends in the silicon–nitrogen binary cluster system. For N-rich clusters, linear or quasi-linear structures predominate, with strong multiple-bond character. Si-rich clusters favor planar or three-dimensional structures. Near the n=m stoichiometry the lowest energy isomers feature a strong alternation of Si and N atoms. Pairing of nitrogen atoms is unfavourable as is strong isolation of nitrogens. We use the results of the calculations to discuss possible growth pathways for the clusters.

Osmium(VI) Nitrido and Osmium(IV) Phosphoraniminato Complexes Containing Schiff Base Ligands

A series of osmium(VI) nitrido complexes containing Schiff base ligands, [Os(VI)(N)(L)Cl] (L = salophen or salen), have been synthesized by reaction of the ligand with [NBu(n)(4)][Os(VI)(N)Cl(4)] in the presence of 2,6-dimethylpyridine. The nu(Os&tbd1;N) for the salophen complexes occur at around 1070 cm(-)(1) and are insensitive to the nature of the substituents present on the Schiff base ligand. The structures of [Os(N)(salophen)(MeOH)]ClO(4) and [Os(N)(5,5-Cl(2)salophen)(MeOH)]ClO(4) have been determined by X-ray crystallography, and the Os&tbd1;N bond distances are 1.651 and 1.66 Å, respectively. The osmium(VI) nitrido complexes react rapidly with triphenylphosphine to produce the corresponding osmium(IV) phosphoraniminato complexes, [Os(IV)(NPPh(3))(L)Cl]. The osmium(IV) complexes exhibit reversible Os(V/IV) and Os(IV/III) couples in cyclic voltammetry. The E(1/2) values show linear correlations with the Hammett constants sigma(p) of the substituents on the Schiff base ligand. The structure of [Os(IV)(NPPh(3))(salophen)Cl] has been determined by X-ray crystallography. The rather long Os-N(P) bond length (1.92 Å) and acute Os-N-P bond angle (149.6 degrees ) suggest that there is no significant multiple-bond character in the Os-N bond. The kinetics of nitrogen atom transfer from a series of 5,5'-disubstituted salophen nitrido complexes to PPh(3) have been studied in CH(3)CN at 25.0 degrees C by stopped-flow spectrophotometric method. The following rate law was obtained: -d[Os(VI)]/dt = k(2)[Os(VI)][PPh(3)]. The reactivities of the complexes were found to follow a Hammett correlation of log(k(X)/k(H)) with sigma(p), with a rho value of 1.9 +/- 0.1. The positive rho value is consistent with a transition state involving electrophilic attack by the nitrido ligand on the phosphorus atom.

Chemistry of Diazaphosphole−Phosphines. 3. Complexation Reactions of Substituted (Fluoro, Dimethylamino, or Trifluoroethoxy)diazaphosphinephospholes with Ru(II), Rh(I), and Rh(III) Precursors: The Crystal and Molecular Structures of Cyclopentadienylbis(κP-4-(difluorophosphino)- 2,5-dimethyl-2H-1,2,3σ2-diazaphosphole Rhodium(I) andtrans-Chlorocarbonylbis(κP-4-(dimethylaminophosphino)- 2,5-dimethyl-2H-1,2,3σ2-diazaphosphole Rhodium(I)

Metal complexes of a series of diphosphorus ligands, 4-(difluorophosphino)-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (1), 4-(bis(dimethylaminophosphino)-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (2), and 4-bis(1,1,1-trifluoroethoxyphosphino)-2,5-dimethyl-2H-1,2,3σ2-diazaphosphole (3), were prepared. Ligand 1 reacted with CpRu(PPh3)2Cl to give the diastereotopic complex CpRu(PPh3)(1)Cl (4). With CpRh(CO)2 this same ligand gave CpRh(1)2 (5), which was structurally characterized. The Cp−rhodium center carries two difluorophosphinodiazaphole ligands. The P−N bond distances, (1.670(4) and 1.672(3) A), suggest partial multiple-bond character. [Cp*Rh(Cl)2] with (1) gave Cp*Rh(Cl)2(1). Ligand 2 with [Rh(CO)2Cl]2 gave trans-Rh(CO)Cl(2)2 (7), which was structurally characterized. The structure reveals two square-planar isomers in 75:25 ratio differing only in the interchange of Cl and CO. The two diazaphosphole ligands lie trans to each other and the planar diazaphosphole rings are oriented perpendicular to the square pl...

Bonding in mixed halogen and hydrogen peroxides

The geometries and vibrational frequencies of the hydrogen and halogen peroxides XOOX′ and the XOO and XO fragments (X, X′ = H, F, Cl, Br or I) have been studied using non-local density functional theory. The X–O, X′–O and O–O bond energies have been calculated and likely dissociation paths for these atmospherically important or potentially important molecules suggested. The sulfur analogues have also been examined. A unified model for these chemically diverse species is presented based on the interaction between O2 and X· · ·X fragments. The correlation between their electronic structures is outlined. The antibonding nature of the interaction between the halogen lone pairs and the π electrons of the O2 fragments causes lengthening and weakening of the halogen–oxygen bonds. The electronegativity of X and X′ determines the extent and direction of the electron transfer between the O2 and X· · ·X fragments. The O–O bond order is thus sensitive to the nature of the substituents and the multiple bond character decreases steadily as the electronegativity of X and X′ decreases. The O–O bond strengths, though, are also affected by steric interactions between the halogen `lone pairs'. The O–O bonds in the HO–OX′ species are thus much stronger than the bond orders and lengths suggest.

Can triple bonds exist between gold and main-group elements?

Pseudopotential ab initio calculations of several gold carbides, gold nitrides and their third-row analogues have been performed with the goal of finding species which contain triple bonds with gold. Multiple-bond character has been observed for Cl2AuCH and Cl2AuN. Bonding in these and related compounds is analysed and the reasons why gold prefers single bonds are outlined.

The crystal structures of (p-ClPh)3PO and (p-OMePh)3PO, including an analysis of the P-O bond in triarylphosphine oxides

The crystal structures of the compounds tris(para-chlorophenyl)phosphine oxide {(p-ClPh)3PO} and tris(para-methoxyphenyl)phosphine oxide {(p-OMePh)3PO} were determined by X-ray diffraction methods. (p-ClPh)3PO crystallizes in the space group P-1 (no. 2) with a = 11.828(2), b = 12.645(2), c = 14.072(2) A, α = 97.90(1), β = 109.45(1), γ = 115.43(1), V = 1692.3(2) A3 and Z = 4. The mean O–P and C–P distances are 1.481(6) and 1.806(2) A, respectively, and the mean C–P–C angle is 106.5(1.1). (p-OMePh)3PO crystallizes in the space group P21/c (no. 14) with a = 18.8642 (10), b = 10.3999(5), c = 21.3462(16) A, β = 115.414(6)°, V= 3782.6(4) A3, and Z = 8. The mean O–P and C–P distances are 1.484(5) and 1.798(4) A, respectively, and the mean C–P–C angle is 106.5(1.0). These two structures were analyzed along with the previously determined structures of triphenylphosphine oxide {Ph3PO} and tri-p-tolylphosphine oxide {(p-MePh)3PO}, and IR data were collected on all four compounds. Both the observed P–O distances and the IR stretching frequencies for these triarylphosphine oxides support the interpretation of the P–O bond as having substantial multiple-bond character, with a bond order between 1.7 and 1.8. The para-substituents on these triarylphosphines were shown to have a statistically insignificant effect on the P–O bond.

Pentacarbonyl(triphenylsilyl)manganese(I)

The title compound, [Mn(C18H15Si)(CO)5], crystallizes in the space group P\overline{1} with two molecules in the asymmetric unit. It is a strong covalent `bimetallic' complex with partial multiple-bond character in the `metal–metal' bond as evidenced by the short (average) Mn—Si distance of 2.504 (6) A.

Raman Spectroscopic Determination of the Structure and Orientation of Organic Monolayers Chemisorbed on Carbon Electrode Surfaces

Azobenzene (AB) and 4-nitroazobenzene (NAB) were covalently bonded to carbon surfaces by electrochemical reduction of their diazonium derivatives. The N(1s) features of XPS spectra of modified surfaces had intensities expected for monolayer coverage. However, the Raman spectra were significantly more intense than expected, implying an increase in scattering cross section upon chemisorption. A likely explanation is resonance enhancement of the carbon/adsorbate chromophore analogous to that reported earlier for dinitrophenylhydrazine (DNPH) chemisorption. Vibrational assignments indicate that the C-C vibration between azobenzene and the carbon surface is in the 1240-1280 cm(-1) region, and this conclusion is supported by spectra obtained from [(13)C]graphite. Observation of depolarization ratios for 4-nitroazobenzene and DNPH on graphite edge plane indicate that NAB is able to rotate about the NAB/carbon C-C bond, while chemisorbed DNPH is not. The partial multiple bond character of the DNPH linkage to graphite is consistent with the observation that the DNPH π system remains parallel to the graphitic planes.

Theoretical Calculation of Thermochemistry for Molecules in the Si−P−H System

Ab initio molecular orbital calculations have been performed on species belonging to the Si-P-H system. These computations have been coupled to a bond additivity correction procedure to obtain heats of formation for 27 species. The Si-P single bond energy was found to be nominally about 300 kJ/mol, which is somewhat weaker than a Si-Si single bond. Multiple bond character in Si-P was found to be relatively weak. 11 refs., 7 tabs.

Aminozirconocenes: a new class of zirconocenes with a nitrogen atom directly bonded to an η 5-cyclopentadienyl (indenyl) ligand

The reactions of 2-indanone or 3,4-diphenylcyclopent-2-enone with pyrrolidine and N,N'-dimethylethylenediamine respectively lead to the corresponding 2-aminoindenes and 1-amino-3,4-diphenylcyclopentadienes, whose lithium salts can be reacted with ZrCl 4 to generate the corresponding moisture-sensitive aminozirconocene dichlorides. The X-ray crystal structure of di-(2-N-pyrrolidine-η 5-indenyl)zirconium dichloride was determined, in which the zirconocene exists exclusively as a racemic-mixture, whereas the meso-rotamer is not present. The (indenyl) carbon-nitrogen bond lengths range from 132.5(7) to 134.9(8) pm, which is indicative of considerable multiple bond character.

Syntheses and X‐Ray Crystal Structures of 2‐Aminoindenes and Aminocymantrenes

AbstractSubstituted 2‐aminoindenes have been synthesized in almost quantitative yields by reactions of amines such as methylpiperazine, trimethylethylenediamine, 1,4‐diaza‐cycloheptane and N,N′‐dimethylethylenediamine with 2‐indanone. The 2‐aminoindenes can be deprotonated and reacted with BrMn(CO)3(Py)2 to produce the respective aminoindenyl‐cymantrenes in yields between 55–70%. The X‐ray crystal structures of 2‐(methylpiperazine)indenyl‐cymantrene 5 (P1, a = 12.667(3) Å, b = 16.630(3) Å, c = 17.382(3) Å, α = 72.70(3)°, β = 74.59(3)°, γ = 88.66(3)°, V = 3364.1(12) Å 3, Z = 8, R1(2σ(I)) = 4.02%, wR2(2σ(I)) = 10.30%) and the HClO4 adduct of 2‐(trimethylethylenediamine)‐indenyl‐cymantrene 6 (Cc, a = 23.722(5) Å, b = 6.9080 Å, c = 13.264 Å, β = 111.77(3)°, V = 2018.6(7) Å 3, Z = 4, R1(2σ(I)) = 2.94%, wR2(2σ(I)) = 7.90%) were determined. In both complexes the indenyl‐carbon bonded to nitrogen displays significantly longer bonds to manganese [223.5(3)–225.8(3) pm] than the other four carbon atoms [213.3(3)–219.1(3) pm]. The short indenyl‐nitrogen bonds of 136.2(4) and 137.8(4) pm are indicative of a substantial multiple bond character. The complexation of Zn2+ by the nitrogen atoms of 6 results in significant shifts of the CO stretching frequencies.