Free Imine Research Articles

Synthesis and Complexation of Monotosylated 4-Aminopyridine with Nickel (II) and Iron (II) Ions

Tosylated 4-aminopyridine and other sulfonylated compounds of amines comprise a substantial class of pharmaceutical drugs used as antibiotics in the field of medicine. This research aimed at the synthesis of tosylated 4-aminopyridine and the complexation of the tosyated 4-aminopyridine with Ni(II) and Fe(II) ions. The sulfonamide was prepared by the action of tosyl chloride on 4-aminopyridine in an aqueous alkaline medium. The complexes were synthesized by the reaction of Ni(NO3)2.6H2O /Fe(NO3)2.6H2O with sulfonamide derivative. These compounds were characterized through Ultraviolet Visible spectroscopy (UV–Vis), Fourier Transform Infer-Red (FTIR) spectroscopy, Proton Nuclear Magnetic Resonance (1HNMR), Carbon-13 Nuclear Magnetic Resonance (13CNMR) and Electron Spray Ionisation-Mass Spectrometer (ESI-MS) and micro-analysis. The IR spectral data suggested that the sulfonamide derivative acts as a neutral ligand towards Ni (II) and Fe (II). In their complexes, the coordination frequency bands of 1665.55 and 1674.21 cm−1 were assigned to Ni−N and Fe−N bonds, and 1687.70 cm−1 was assigned to free tosylated 4-aminopyridine. This decrease in the frequency band of free imine to coordinated imine complexes indicates that electron transfer occurred from the ligand to the d-orbitals of the metals. The complexation of4-Methyl-N-(pyridin-4-yl)benzene sulfonamide can increase the biological and catalytic potential of the ligand in the pharmaceutical and chemical industries.

Synthesis and evaluation of pyrrolobenzodiazepine dimer antibody-drug conjugates with dual β-glucuronide and dipeptide triggers

Antibody-drug conjugates (ADCs) containing pyrrolobenzodiazepine (PBD) dimers are currently being evaluated in human oncology clinical trials with encouraging results. To further improve the therapeutic window, next-generation PBD drug-linker design has focused on the inclusion of additional tumor-selective triggers and use of lower-potency PBDs. β-Glucuronidase is a well-known target for discovery prodrugs due to increased presence in tumor cells and microenvironment. In this study, a β-glucuronidase cleavable cap was investigated at the PBD N10-position and compared with corresponding free imine ADCs. SG3600 (glucuronide) ADCs showed in vitro and in vivo efficacy/tolerability comparable to SG3400 (imine) ADCs, and good 50% inhibitory concentration differentials were observed in vitro between control non–antigen-targeted ADCs and targeted ADCs. Dependence on β-glucuronidase for SG3600 activity was demonstrated through CRISPRCas9 knockdown studies and addition of exogenous β-glucuronidase. SG3600 showed better serum stability, improved conjugation efficiency and was able to reach high drug-to-antibody ratio without aggregation.

ChemInform Abstract: A Comparative Investigation: Group 9 Cp*M(III)‐Catalyzed Formal [4 + 2] Cycloaddition as an Atom‐Economic Approach to Quinazolines.

AbstractThe cobalt catalyst exhibits excellent efficiency and selectivity in the novel formal [4 + 2] cycloaddition of arenes with a free imine unit and dioxazolones to quinazoline derivatives.

A Comparative Investigation: Group 9 Cp*M(III)-Catalyzed Formal [4+ 2] Cycloaddition as an Atom-Economic Approach to Quinazolines.

A comparative study on the catalytic activity of different group 9 [Cp*M(III)] complexes in the formal [4 + 2] cycloaddition of arenes with rarely explored free imines and dioxazolones for the construction of multisubstituted quinazolines is reported herein. This investigation revealed that the cobalt catalyst is uniquely suited to this transformation due to its strong Lewis acidity and high sensitivity to steric hindrance.

Synthesis of 4-chalcogeno-1-aza-1,3-butadiene derivatives by intramolecular cyano-Diels-Alder reaction and borane-coordination-induced fluorescence enhancement.

4-Thio-1-aza-1,3-butadiene derivatives 3 incorporating a rigid dibenzobarrelene skeleton were synthesized by the intramolecular cyano-Diels-Alder reaction of 9-anthryl cyanoethenyl sulfides 6. The thermal reaction of 6 afforded an equilibrium mixture of 3 and 6, but the cyclization was effectively promoted by the addition of BF3·Et2O or B(C6F5)3 to yield imine-borane adducts 8 and 9. The imine-borane adducts emit intense blue fluorescence both in solution and in the crystalline state. This is in stark contrast to free imines 3, which are weakly fluorescent. Selenium analogue 4 and N-oxide 12 of 3a were synthesized, along with their B(C6F5)3 adducts.

Alignment of Palladium Complexes into Columnar Liquid Crystals Driven by Peripheral Triphenylene Substituents

A new triphenylene-imine (ImH) and its ortho-palladated complexes (μ-X)2[Pd2Im2] (X = CH3COO(-), Cl(-), Br(-)), (μ-Cl)(μ-SCnH2n+1)[Pd2Im2] (n = 6, 12), [PdIm(acac)] [PdIm Cl(CNC6H4OC12H25)], [PdImCl(CNC6H3(OC12H25)2)], and [PdImCl(CNC6H2(OC12H25)3)] have been prepared. The free imine ligand is not a liquid crystal, but most ortho-metalated dinuclear palladium complexes and the mononuclear trialkoxyphenyl isocyanide derivative display columnar mesophases at temperatures close to ambient. For the dimeric complexes the mesophase obtained is always columnar rectangular (Colr), with an uncommon structure: the dimeric triphenylene-Pd complex-triphenylene molecules give rise to a triple-column stacking consisting of two columns of stacked triphenylene groups connected to a central column formed by stacking of two ortho-palladated dimeric moieties. For the trialkoxyphenyl isocyanide derivative a related polymer-like arrangement of columns alternating stacking of triphenylenes with stacking of two ortho-palladated dimeric moieties is found. The mesophase structure is columnar oblique (Colob). The free imine and all palladium complexes exhibit fluorescence at room temperature in dichloromethane solution, associated with the triphenylene core.

Branched Polyamines Functionalized with Proposed Reaction Pathways Based on <sup>1</sup>H-NMR, Atomic Absorption and IR Spectroscopies

Three novel branched polyamines N,N,N’,N’-tetrakis-[3((pyridine-2-methyl)-amine) propyl]-1,4- butanediamine (1), N,N,N’,N’-tetrakis-[N-((2-methylpyridine)ethyl)propanamide]ethylenediamine (2) and N,N,N’,N’-tetrakis-[3((2-hidroxibenziliden)-amine)propyl]-1,4-butanediamine (3), were synthesized starting from 2-pyridinecarboxaldeyde with DAB-Am-4 for 1, PAMAM G0 for 2 and from salicylaldehyde with DAB-Am-4 for 3. The pathway reactions have been proposed by 1H-NMR, IR and Atomic Absorption Spectroscopy. The optimal reaction time was set by IR spectroscopy following aldehyde peak modification. 1 and 2 were obtained as both hydrochlorides and as free amines and 3 only as free imine. These polyamines were characterized by UV-Vis, IR, 1H-NMR and 13C-NMR and Mass Spectrometry.

Pyridine vs. Bipyridine Coordination in PtCl2 Complexes of 4‐tButyl‐4'‐(4‐pyridinyl)‐2, 2'‐bipyridine

AbstractThe reaction of the new terpyridine ligand 4‐tbutyl‐4'‐(4‐pyridinyl)‐2, 2'‐bipyridine L with various sources of “PtCl2” selectively yields either trans‐[PtCl2(L)2] (1) with L bonded in a monodentate fashion via its pendant 4‐pyridyl ring or cis‐[PtCl2(L)] (2), where L coordinates in a bidentate fashion through its 2, 2'‐bipyridine subunit. The molecular structures of L and of complex 1 were determined by X‐ray crystallography and exhibit intra‐ and intermolecular hydrogen bonding. We have also converted the dichloro complex 2 into the bis(coumarin thiolate) complex 3. Owing to their free imine coordination sites, complexes 1–3 constitute interesting building blocks for multimetal structures in a “complexes as ligands” approach. The reductive behaviour of L and of complexes 1–3 has been investigated by cyclic and square wave voltammetry.

Carboranylamidinates

AbstractThis Research Report provides an overview on synthesis, structure, and reactivity of the recently discovered carboranylamidinate ligands. Carboranylamidinate anions of the type [(o‐C2B10H10C(NHR)(=NR)]– (R = iPr, cyclohexyl) are readily accessible via addition of o‐lithiocarborane to N,N′‐carbodiimides R–N=C=N–R. They combine the highly versatile characteristics of both amidinates and carboranes in one unique ligand system. Unlike simple amidinate anions, the carboranylamidinates coordinate to metal ions not as typical N,N′‐chelating ligands but adopt an unexpected κ2C, N‐bonding mode. The free imine functionality in carboranylamidinates can be further deprotonated. The resulting dianions were demonstrated to be excellent starting materials for novel boron‐rich heterocycles incorporating e.g. Si, Sn, P, or transition metals such as Ti, Zr, Rh, and Ir. Further modification of the carboranylamidinate cage structure includes the introduction of additional functional groups like –SH or –SeH as well as the selective removal of a boron atom with formation of novel nido‐type dicarbollylamidinate ligands. An initial study already showed that transition metal carboranylamidinates are potentially useful as polymerization catalysts.

Titanium(iv) imido complexes of imine imidazol-2-imine ligands

Free imine imidazol-2-imine ligands with two different substitution patterns have been isolated for the first time and they were found to exist as an equilibrium mixture of geometric and mesomeric isomers. The relative ratios of these isomers are dependent on both the nature of the substituents and of the solvent. The synthesis of the titanium(IV) alkyl and arylimido complexes of these ligands was unexpectedly found to be very selective and was successfully achieved only with the lesser sterically-demanding 2,4,6-trimethylphenyl derivative IMesN^Imine 2a. The solid-state structure of the alkylimido complex further confirms the zwitterionic character of the ligand. The isolated titanium imido complexes were found to be active catalysts for the polymerisation of ethylene.

Cyclopalladated complexes of perylene imine: mononuclear complexes with five- or six-membered metallacycles

Mononuclear palladium complexes [Pd(C^N)L(2)] (HC^N = 3-C(20)H(11)CH=NC(6)H(4)-p-C(2)H(5)) have been prepared with Pd bound to the peri site or to the ortho site of the perylenyl fragment. These metallations correspond, respectively to six-membered (L(2) = S(2)COMe (3); acac (4); Cl, PMe(3) (5); Cl, PPh(3) (6); S(2)CNEt(2) (7)) or five-membered (L(2) = S(2)COMe (8); acac (9)) isomeric palladacyclic compounds. The X-ray structures of 3, 5, 7 and 8 show that the perylenyl fragment remains essentially flat for 3, 7 and 8 and twisted for 5. Intermolecular π-π stacking of perylenyl rings is observed only for 7. All palladium complexes exhibit fluorescence associated to the perylene fragments, with emission quantum yields (in solution at room temperature) in the range 0.01-0.12 (compared to 0.13 for the free imine), and emission lifetimes ∼ 1 ns. The complexes with five-membered palladacycles show lower quantum yields than their six-membered analogs. The similarity in shape of the luminescence spectra of these metallated complexes with perylene, although red-shifted, strongly suggests a perylene-dominated intraligand π-π* emissive state, metal-perturbed by interaction of the perylene orbitals with the palladium fragment.

Supramolecular Structures from Polycarbene Ligands and Transition Metal Ions

The synthesis of cylinder-type carbene complexes from polycarbene ligands and coinage metal ions via metal-controlled self-assembly has been explored. Imidazole reacts with 1,2,4,5-tetrabromobenzene or 1,3,5-tribromobenzene to give 1,2,4,5-tetrakis(1-imidazolyl)benzene (1) and 1,3,5-tris(1-imidazolyl)benzene (3), respectively. The tetrakisimidazolium salts of type H4-2a,b(Br)4 and the trisimidazolium salts of type H3-4a,b(Br)3 have been prepared by alkylation of the remaining free imines of the tetrakis- and trisimidazoles (H4-2a4+, H3-4a3+: R = n-butyl; H4-2b4+, H3-4b3+: R = ethyl). Polyimidazolium salts H4-2a,b(PF6)4 and H3-4a,b(PF6)3 have been synthesized by anion exchange from H4-2a,b(Br)4 and H3-4a,b(Br)3. Two equivalents of tetraimidazolium salt H4-2a(Br)4 or H4-2a,b(PF6)4 reacts with four equivalents of Ag2O to yield via self-assembly molecular cylinders of type [Ag4(2a)2]Y4 (Y− = [AgBr2]− and/or Br−) or [Ag4(2a,b)2](PF6)4, respectively. Similarly, reaction of two equivalents of trisimidazolium sal...

Synthesis, crystal structure and second-order nonlinear optical properties of the trinuclear palladium orthometalated complex [( μ3-S)( μ3-OH)Pd 3(C^N) 3] (HC^N = p- [formula omitted]–C 6H 4–CH [dbnd]N–C 6H 4–NO 2- p)

A smooth reaction of [(μ 2-OH) 2Pd 2(C^N) 2] ( 3) with CS 2·(HC^N = p- ( Bu 2 n N ) –C 6H 4–CH N–C 6H 4–NO 2- p) provides [( μ 3-S)( μ 3-OH)Pd 3(C^N) 3] ( 4). The X-ray structures of 4 shows that the complex contains a ( μ 3-S)( μ 3-OH)Pd 3 core which forces an all-cis arrangement of the three orthometalated ligands. The variation of the β(0) value per imine moiety, on going from the free imine to the trinuclear complex ( 4) is negative: −17%. In contrast, for the dinuclear complexes [( μ 2-SBu)( μ 2-OAc)Pd 2(C^N) 2] ( 5) or [( μ 2-SBu)( μ 2-Cl)Pd 2(C^N) 2] ( 6), having also a cis-arrangement of the orthometallated imines, this variation is positive: +14% and +30%, respectively. The β(0) variation seems to be concordant with the trend of the molar extinction coefficients values.

Supramolecular Aggregates in Fluid Phases: Mesomorphic ortho‐Palladated Complexes with Substituted Crown Ethers and Their Potassium Adducts

AbstractNew imines (HL) containing substituted dibenzo‐18‐crown‐6‐ethers and their dinuclear ortho‐palladated complexes, [Pd(μ‐X)L]2 (X– = CH3COO–, Cl–), have been prepared. The free imine ligands are not liquid crystals, but the palladium complexes, including acetato‐bridged derivatives, show liquid‐crystal properties. The mesomorphic palladium complexes bear six or eight alkoxy chains. Although a columnar arrangement of these chains might be expected, a smectic arrangement is in fact preferred for half of the metallomesogens prepared, which show a smectic C mesophase. Complexation with potassium produces a significant increase in the mesophase range and stability. Moreover, both the free imines and the corresponding liquid‐crystalline ortho‐palladated complexes form stable Langmuir films at the air–water interface.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Unusual Reaction between (Nitrile)Pt Complexes and Pyrazoles: Substitution Proceeds via Metal-Mediated Nitrile−Pyrazole Coupling Followed by Elimination of the Nitrile

The reaction of platinum(IV) complex trans-[PtCl4(EtCN)2] with pyrazoles 3,5-RR'pzH (R/R' = H/H, Me/H, Me/Me) leads to the formation of the trans-[PtCl4{NH=C(Et)(3,5-RR'pz)}2] (1-3) species due to the metal-mediated nitrile-pyrazole coupling. Pyrazolylimino complexes 1-3 (i) completely convert to pyrazole complexes cis-[PtCl4(3,5-RR'pzH)2] by elimination of EtCN upon reflux in a CH2Cl2 solution or upon heating in the solid state; (ii) undergo exchange at the imino C atom with another pyrazole different from that contained in the pyrazolylimino ligand. The reaction of trans-[PtIICl2(EtCN)2] and 3,5-RR'pzH, conducted under conditions similar to those for trans-[PtIVCl4(EtCN)2], is much less selective, and the composition of the products strongly depends on the pyrazole employed: (a) with pzH, the reaction gives a mixture of three products, i.e., [PtCl2NH=C(Et)pz-kappa2N,N}] (4), [PtCl(pzH){NH=C(Et)pz-kappa2N,N}]Cl (5), and [Pt(pzH)2{NH=C(Et)pz-kappa2N,N}]Cl2 (6) (complexes 5 and 6 are rather unstable and gradually transform to trans-[PtCl2(pzH2] and [Pt(pzH)(4)]Cl(2) and free EtCN); (b) with 3,5-Me(2)pzH, the reaction leads to the formation of [PtCl2NH=C(Et)(3,5-Me2pz)-kappa2N,N}] (7) and [PtCl(3,5-Me2pzH)3]Cl (8); (c) in the case of asymmetric pyrazole 3(5)-MepzH, which can be added to EtCN and/or bind metal centers by any of the two nonequivalent nitrogen sites, a broad mixture of currently unidentified products is formed. The reduction of 1-3 with Ph3P=CHCO2Me in CHCl3 allows for the formation of corresponding platinum(II) compounds trans-[PtCl2{NH=C(Et)(3,5-RR'pz)}2] (9-11). Ligands NH=C(Et)(3,5-RR'pz) (12-14) were almost quantitatively liberated from 9-11 with 2 equiv of 1,2-bis-(diphenylphosphino)ethane in CDCl3, giving free imines 12-14 in solution and the precipitate of trans-[Pt(dppe)2](Cl)2. Pyrazolylimines 12-14 undergo splitting in CDCl3 solution at 20-25 degrees C for ca. 20 h to furnish the parent propiononitrile and the pyrazole 3,5-RR'pzH, but they can be synthetically utilized immediately after the liberation.

Solution and Solid-State Characteristics of Imine Adducts with Tris(pentafluorophenyl)borane

Adducts of the N-benzyl imines Ph(R)CNBn (R = Ph, CH3, H) and tBu(CH3)CNBn and the N-phenyl imine Ph(H)CNPh with the Lewis acid tris(pentafluorophenyl)borane, B(C6F5)3, have been prepared and characterized in solution and in the solid state. For each imine, the Lewis acid is N-bound, with the exception of the sterically demanding base tBu(CH3)CNBn, which reacts with B(C6F5)3 through its enamine tautomer to form an α-C bound adduct, 5. In the N-bound imine−borane adducts 1−4, steric crowding and π-stacking between C6F5 and C6H5 rings results in restricted rotation about the B−N and B−C bonds; the dynamic behavior which results can be studied using variable-temperature 19F and 1H NMR spectroscopy. For the unsymmetrical ketimines and aldimines, kinetic adducts of the thermodynamically dominant free imine are observed to form initially upon treatment with B(C6F5)3; these adducts slowly convert thermally to the thermodynamic adducts of the less stable imine. For the ketimine Ph(CH3)CNBn, both the kinetic adduct 2-k and the thermodynamic adduct 2-t were fully characterized. In the solid-state structures of all the adducts except 5, one or two C6F5/C6H5 stacking interactions are present; in one case, the adduct 3-t between B(C6F5)3 and Ph(H)CNBn, intermolecular stacking interactions are apparent in the crystal-packing diagram. The implications of the structures of these adducts for Lewis acid mediated addition of nucleophiles to imines is discussed.

Stereoselective Formation of (Aminoalkyl)platinum Complexes from Imines

Reaction of [PtMe2(μ-SMe2)]2 with cis-1,2-C6H10(NCH-2-C5H4N)2 (1) and cis-1,2-C6H10(NCH-2-C9H6N)2 (2) gives the complexes [PtMe2{cis-1,2-C6H10(NCH-2-C5H4N)2}] (3) and [PtMe2{cis-1,2-C6H10(NCH-2-C9H6N)2}] (4), respectively (C5H4N = pyridyl; C9H6N = quinolyl), in which the ligand is bidentate such that each complex is chiral and contains a free imine substituent. Complexes 3 and 4 react with protic acids, HCl and CF3CO2H, to form (aminoalkyl)platinum(IV) products that contain a new asymmetric carbon center, often with very high stereoselectivity. In these products the complex ligand may act as a tridentate N,N,C donor or, in complexes containing an azaplatinacyclobutane ring, as a tetradentate N,N,N,C donor. The absolute configurations of five (aminoalkyl)platinum(IV) products were determined by X-ray crystal structure determinations and gave a benchmark such that the stereochemistries of other complexes could be assigned by NMR. It is suggested that the reactions occur by protonation at the free imine nitrogen to give an iminium ion, and the carbocation then adds to the adjacent platinum(II) center. The initially formed products may rearrange by mechanisms involving reversible ligand dissociation from platinum(IV) or deprotonation of the aminoalkyl group.

Activation of Imines by Platinum(II) To Give Aminoalkyl Complexes: Scope and Limitations of the Reaction

Reaction of an excess of the ligand 1,2-C2H4(NCH-2-C5H4N)2 (1), 1,2-C2H4(NCH-2-C9H6N)2 (2), or 1,3-C3H6(NCH-2-C5H4N)2 (3) with [Pt2Me4(μ-SMe2)2] gives the following platinum(II) complexes that contain a free imine functional group: [PtMe2{C2H4(NCH-2-C5H4N)(NCH-2-C5H4N)}] (4), [PtMe2{C2H4(NCH-2-C9H6N)(NCH-2-C9H6N)} (5), or [PtMe2{C3H6(NCH-2-C5H4N)(NCH-2-C5H4N)}] (6) (C5H4N = pyridyl, C9H6N = quinolyl). The reaction of complexes 4−6 with excess CF3CO2H or HCl gave aminoalkylplatinum(IV) products, and it is suggested that the reactions occur by protonation of the free imine nitrogen atom followed by oxidative addition of the transient iminium group so formed. The products were formed as a mixture of isomers whose structures were deduced from their spectroscopic properties and, for the complexes [PtMe2{C2H4(NCH-2-C5H4N)(NH2CH-2-C5H4NH)}(O2CCF3)][O2CCF3]2 (7a) [PtMe2{C2H4(NCH-2-C5H4N)(NH2CH-2-C5H4NH)}Cl][Cl]2 (8a), and [PtMe2{C3H6(NCH-2- C5H4N)(NH2-CH-2-C5H4N)Cl][Cl] (14a), by X-ray structure determinations. The reaction of 5 with an equimolar amount of CF3CO2H gave [PtMe2{C2H4(NCH-2-C9H6N)(NHCH-2-C9H6N)}][CF3CO2] (9), which was shown by X-ray structure determination to contain a four-membered azametallacyclobutane ring. Attempts to effect the intermolecular protonation/metalation of imines by platinum(II) were unsuccessful, since reactions of [PtMe2(bu2bpy)] (bu2bpy = 4,4‘-di-tert-butylbipyridine) with N-benzylidenemethylamine or N-benzylideneaniline and CF3CO2H led only to protonolysis of the methyl−platinum bonds.

Synthesis of Unsymmetrical Diolate, Oxametallacyclopentene, Amido-Alkoxide and Thiolato-Alkoxide Complexes Using Dialkyl and Diaryl Titanium Aminotroponiminate Complexes: A Route to Unsymmetrical Vicinal Diols

The reactivity of [TiR2(Me2ATI)2] complexes, where Me2ATI = N,N‘-dimethylaminotroponiminate, or L, with CO or RNC in the presence of various organic electrophiles has been investigated. The compounds TiMe2L2 and TiPh2L2 react with CO and aldehydes or ketones to afford unsymmetrical diolate complexes that convert to the corresponding vicinal diols after hydrolysis. Phenyl acetylene also reacts to form the oxametallacyclopentene complex [Ti(OCMe2CHCPh)(Me2ATI)2]. Treatment of TiMe2L2 with RNC yields the free imine and a source of low-valent titanium. Trapping this intermediate with 2 equiv of benzaldehyde or benzil affords the titanium diolate or enediolate complex, respectively. When 1 equiv each of benzophenone and either N-tosylbenzaldimine or acetone were added to the intermediate, [Ti(Ph2COCN(SO2tol)HPh)(Me2ATI)2] and [Ti(Ph2COCOMe2)(Me2ATI)2], respectively, were obtained. The titanium thiolato-alkoxide complex [Ti(Ph2CSCOMe2)(Me2ATI)2] was prepared by use of thiobenzophenone and acetone. This chemistr...

Synthesis and Second-Order Nonlinear Optical Properties of New Palladium(II) and Platinum(II) Schiff-Base Complexes

The second harmonic generations of the dimeric complexes [M2(μ-X)(μ-SCnH2n+1)(RC6H3CHNC6H4R‘)] (M = Pd, Pt; X = Cl, CH3COO, (R)-CH3CHClCOO; R, R‘ = NO2 and OC8H17 or N(C4H9)2; n = 4 or 8) and the monomeric complexes [Pd(RC6H3CHNC6H4R‘)L] (L = C5H5 (Cp), CH3COCHCOCH3 (acac)) and [Pd(RC6H3CHNC6H4R‘)(CNC6H4R‘‘)Cl] (R‘‘ = NO2, OCnH2n+1, N(CmH2m+1)2; n = 4 or 8; m = 1 or 4) have been measured, and the influence of the position of donor and acceptor groups is discussed and compared with that of the free imine ligands. The value of the hyperpolarizability (β) is raised only when a strong donor group is located in the cyclometalated ring. Moreover, the β value has been enhanced, too, in the cyclopentadienyl monomer complex by as much as 80% with respect to the β value of the corresponding free imine. The molecular structure of [Pd2(μ-Cl)(μ-SC4H9)(N(C4H9)2C6H3CHNC6H4NO2] has been determined by an X-ray diffraction analysis.