Giuseppe Tresoldi

Reactions of di-2-pyridyl sulfide with the palladium(II) and platinum(II) diene or methoxydiene complexes. Dynamic behaviour of the cationic compounds. Crystal structure of Pd(di-2-pyridyl sulfide)Cl2

Abstract The complexes [M(dps)Cl2] (MPdII (1); PtII (2)) and the labile compounds [M(MeOdiene)(dps)Cl] (MPdII, MeOdieneCH3OC8H12 (3) or CH3OC10H12 (4); MPtII, MeOdieneCH3OC8H12 (5) or CH3OC10H12 (6)) have been synthesized by reaction of dps (dps=di-2-pyridyl sulfide) with [M(diene)Cl2] (diene=cycloocta-1,5-diene or dicyclopentadiene) and the appropriate chloro-bridged methoxydiene complexes, respectively. The last reactions required drastic conditions. Also the reactions of dps with the solvento species [M(diene)(acetone)2]X2 and [M(MeOdiene)(acetone)2]X (X=BF4, PF6, ClO4) have been studied and the compounds [M(MeOdiene)(dps)]X (MPdII, MeOdieneCH3OC8H12 (7) or CH3OC10H12 (8); MPtII, MeOdieneCH3OC8H12 (9) or CH3OC10H12 (10)) were prepared. The structure of 1 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/n, with Z=4 in a unit cell of dimensions a=9.933(4), b=14.802(5), c=8.465(3) A, β=101.94(2)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full- matrix least-squares on the basis of 2163 observed reflections to R and R′ values of 0.0277 and 0.0348, respectively. In the square planar coordination around the Pd atom the dps molecule acts as a chelate ligand through the two pyridinic N atoms and adopts a N,N-inside conformation. The six-membered chelate ring shows a boat conformation with the Pd and S atoms out of the plane through the other four atoms on the same side. Although dissociation in the usual solvents prevents full characterization of 3–6 IR spectra suggest that the dps acts as monodentate ligand. The 1H NMR spectra, at variable temperature, and 13C NMR spectra of 7–10 show that the cationic complexes in solution undergo at least two dynamic processes; a ligand site exchange and a boat to boat inversion of the chelate dps ring. The ligand site exchange is fast, in the NMR time scale, at room temperature for palladium complexes and at higher temperature for the platinum complexes and makes equivalent the pyridine rings of dps. This process is interpreted in terms of formation of stereochemically non-rigid five- coordinate intermediates. The boat to boat inversion is fast at room temperature at least for platinum complexes. At low temperature the latter process is absent or occurs at markedly reduced rate for palladium complexes while the slow ligand site exchange results in equilibria between two conformers.

Polyfunctional phosphine ligands II. Iridium(I) complexes of the 7-diphenylphosphino-2,4-dimethyl-1,8-naphthyridine (dpnapy) ligand. X-ray crystal structure of [{Ir(cod)Cl}2(μ-dpnapy)]

Abstract The coordination chemistry of the polyfunctional phosphine ligand, 7-diphenylphosphino-2,4-dimethyl-1,8- naphthyridine (dpnapy) with iridium(I) complexes has been investigated. Dpnapy reacts with cis -[Ir(CO) 2 ( p - toluidine)Cl] in 1:2 and 1:1 molar ratios giving the P-monodentate containing ligand complexes trans - [Ir(CO)(dpnapy) 2 Cl] ( 1 ) and cis -[Ir(CO) 2 (dpnapy)Cl] ( 2 ), respectively. Complex 2 is unstable in solution; IR and 31 P NMR spectroscopic data show at r.t. it transforms into 1 in a short time. The reaction of dpnapy with [{Ir(cod)Cl} 2 ] (cod=cycloocta-1,5-diene) also depends on the metal to ligand ratio used. The mononuclear complex [Ir(cod)(dpnapy)Cl] ( 3 ), containing P-coordinated dpnapy, is obtained from the 1:2 dimer:ligand reaction. The 1 H and 13 C NMR spectra of 3 are temperature dependent. They show that the fluxional behaviour involves the cod ligand and is explained by the formation of a labile five-coordinate intermediate displaying a fast exchange of the non-equivalent cod protons and carbons. Treatment of 3 with AgClO 4 leads to a species, formulated on the basis of IR and analytical data, as [{Ir(cod)(dpnapy)}ClO 4 ] ( 4 ) in which dpnapy is very likely PN(8) chelated. The binuclear complex [{Ir(cod)Cl} 2 (μ-dpnapy)] ( 5 ), containing a bridging bidentate dpnapy, is obtained from the 1:1 [{Ir(cod)Cl}2]:dpnapy reaction. The bridging function of dpnapy is realized through the phosphorus and the terminal nitrogen binding sites in agreement with the NMR data and as confirmed by an X-ray analysis. Complex 5 crystallizes into the monoclinic space group P 2 1 / n with cell parameters a =17.813(4), b =12.339(3), c =18.221(5) A, β=106.73(2)° and with Z =4. The structure model, with all the non-H atoms anisotropic, was refined up to R =0.040 and R w =0.050 with the goodness-of-fit=0.91. The asymmetric unit contains one discrete molecule constitued by two independent square-planar iridium moieties, considering each ethylenic system of cycloocta-1,5-diene like a unique coordination site. No interaction exists between the two iridium metal centres.

Synthesis and spectroscopic properties of di-2-pyridyl sulfide (dps) compounds. Crystal structure of [Ru(dps)2Cl2]

Bis(di-2-pyridyl sulfide)ruthenium(II) complexes containing the ligands CI, NO2, NO, MeCN, py (pyridine), pyz (pyrazine) or 4,4′-bipy (4,4′-bipyridine) have been prepared by usual methods and a new direct procedure from robust [Ru(dps)2CI2]1a(dps = di-2-pyridyl sulfide). This is the main product of the reaction between dps and RuCl3 in refluxing dimethylformamide (dmf) while minor products are the complexes [Ru(dps)(dmf)(CO)CI2] and [Ru(dps)2(CO)CI][PF6]. The crystal structure of 1a has been determined: orthorhombic, space group Pbcn, a= 8.587(2), b= 16.421(3), c= 15.023(3)A, Z= 4 and R= 0.024. The Ru atom exhibits an almost ideal octahedral co-ordination geometry involving two CI atoms, in cis position, and the two dps ligands chelated through the respective pyridine N atoms. Each dps adopts a twisted N,N-inside conformation. The six-membered chelate rings show boat conformations with the Ru and S atoms out of the plane through the other four atoms on the same side. Oxidation of 1a by HNO3 or cerium(IV) salts, followed by precipitation with NH4PF6, gave [Ru(dps)2CI2][PF6]. The complexes have been characterized by infrared, UV/VIS, 1H and 13C NMR spectroscopies. The 1H NMR resonances of the pyz and 4,4′-bipy derivatives were assigned by employment of correlation spectra. The lowest-energy band in the visible spectrum of 1a, assigned as a dπ(Ru)→π*(dps) transition, is blue shifted with respect to that of [Ru(2,2′-bipy)2CI2]. Further blue shifts are observed on replacing in the Cl–1a by stronger π-acceptor ligands such as NO2–, MeCN and NO+.

Crystal structure of [Pd(μ3-2-propenyl)(dps)][Pd(μ3-2-propenyl)Cl2]. NMR evidence of binuclear μ3-allyl palladium(II) species with bridging dps

Abstract The reactions of di-2-pyridyl sulfide (dps) with (μ3-allyl)palladium chloride dimers gave the ionic compounds [Pd(μ3-allyl)(dps)][Pd(μ3-allyl)Cl2] (allyl=2-propenyl (1), 2-methyl-2-propenyl (2), 2-butenyl (3)). The structure of 1 has been determined by X-ray diffraction methods. Crystals are triclinic, space groupP 1 , with Z=2 in a unit cell of dimensions a=8.840(1), b=8.928(1), c=12.317(2) A, α= 98.82(1), β=90.46(1), γ=95.46(1)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares on the basis of 3855 observed relections to R and Rw values of 0.0269 and 0.0339, respectively. Compound 1 consists of discrete complex ion pairs, containing allyl groups coordinated to both the cationic and anionic palladium centres. In the cationic portion the dps acts as a chelate ligand and adopts an N,N inside conformation. The six-membered chelate ring shows a boat conformation. The cation and anion are connected by a short Pd2…Cl2 interaction (3.073(1) A) which determines pseudo-five-coordination for the cation. At low temperature the 1H NMR spectra in CD3OD of 1 and 2 confirm the presence of the cation and the anion while in CDCl3 they also indicate the presence of a binuclear species with bridging dps. The 1H NMR spectra, at variable temperature, show that 1, 2 and 3 in solution undergo dynamic processes. In CDCl3, a lower energy process makes the π-allyl groups equivalent at room temperature, a higher energy process determines the magnetic equivalence of syn and anti π-allyl protons at high temperature.

Synthesis and reactivity of formamidinato rhodium(I) complexes

Abstract The syntheses of [Rh(diol)(formamidine)] 2 complexes (diol  cycloocta-1,5-diene (1); diol  norbornadiene (2); formamidine  N , N ′-di- p -tolylformamidine) are reported. These complexes are dimeric and contain the bridging formamidino ligand. They react with CO, dppe and PPh 3 with displacement of the diene ligand to yield the known [Rh(CO) 2 (formamidine)] 2 , [Rh(dppe) 2 ] + and [Rh(PPh 3 ) 2 (formamidine)], respectively; the last complex, in which the formamidine acts as a chelating ligand, was isolated only as the O 2 adduct. With HCl or HBF 4 aqueous 1 and 2 do not form hydrides but instead the formamidino cation [ p -tolyl-NHCHNHtolyl- p ] + and the complexes [Rh(diol)X] 2 (X  Cl, F); a possible scheme for the reaction with HCl is proposed. The [Rh(C 8 H 12 )(formamidine)] 2 complex reacts with heterocumulenes as CS 2 , SO 2 , PhNCS and PhNCO with diene displacement; the only product isolated was [Rh(CS 2 ) 2 (formamidine], to which a polymeric structure is assigned.

Self-assembly of [Bu4N][M(qdt)2] [qdt=quinoxaline-2,3-dithiolate; M=Au and Cu] in a 2D network via combination of CH⋯M and CH⋯S interactions

Abstract The compounds [Bu4N][M(qdt)2] (M=Au 1 and M=Cu 2) have been prepared and characterized by X-ray diffraction studies. Complexes 1 and 2 are isomorph and their structure consists of a two-dimensional intermolecular cation–anion network with the [Bu4N] cation acting as a four H-bonded bridging ligand.

Synthesis and dynamic behaviour of rhodium(I) complexes containing the di-2-pyridyl sulphide ligand

The complexes [Rh(cod)(dps)]X 1(cod = cycloocta-1,5-diene; dps = di-2-pyridyl sulphide; X = BF4, PF6 or ClO4) has been prepared by reaction of dps and AgX with [{Rh(µ-Cl)(cod)}2]; [Rh(CO)2(dps)]X 2 can be prepared by a similar route but higher yields are obtained by bubbling CO through a CH2Cl2 solution of 1. Triphenyl-phosphine or -arsine easily replaces a molecule of CO in 2 to give [Rh(CO)(PPh3)(dps)]X 3 or [Rh(CO)(AsPh3)(dps)]X 4. These compounds have been characterized by usual spectroscopic techniques which indicate a N, N-inside conformation for the chelate dps ligand. The reaction of [{Rh(µ-Cl)(cod)}2] with dps gives rise to stoichiometry-, concentration-, solvent- and temperature-dependent equilibria in which the starting materials, the binuclear complex [{Rh(cod)Cl}2(µ-dps)]5a, [Rh(cod)(dps)]+, [Rh(cod)Cl2]– and Cl– are involved. Complex 5a and [Rh(cod)(dps)][Rh(cod)Cl2]5b can be isolated as solids whereas [Rh(cod)(dps)]Cl is present only in solution. Conductivity measurements and electronic spectra indicate that the ionic species are stabilized in methanol, whereas in CH2Cl2 the starting materials and binuclear species dominate at low and higher concentration respectively. Proton and 13C NMR spectra, in CD2Cl2 indicate that exchange of the Rh(cod) unit between the starting materials, binuclear and ionic species occurs rapidly in the NMR time-scale at room temperature. When dps is added to 5a or 5b(molar ratio 1:1) the concentration of the binuclear species decreases and an equilibrium occurs between [Rh(cod)(dps)]Cl and [Rh(cod)Cl(dps)] where the dps ligand is monodentate.

Ligating properties of thionitrosoamines: II. Crystal and molecular structure of cis-dichloro-(N-thionitrosodimethylamine)(triphenylarsine)-palladium(II) complex. Synthesis and characterization of neutral binuclear complexes of palladium(II) and cationic complexes of palladium(II) and platinum(II) containing N-thionitrosodimethylamine

Abstract The crystal and molecular structure of Pd(SNNMe2)(AsPh3)Cl2 was determined from single-crystal X-ray diffraction data. In agreement with the structure previously proposed on the basis of IR data, the complex has the cis-configuration with the Me2NNS ligand S-bonded to the metal. It crystallizes in the space group P 1 with a 9.407(2), b 10.540(2), c 12.265(4) A; α 68.1(1), β 78.3(1), γ 86.3(1)° and Z = 2. The structure was refined to R = 0.029 for 2664 diffractometer data with I ≥ 3σ(I. The palladium atom is in a nearly square planar coordination geometry with PdS 2.249(1), PdAs 2.362(1), Pd-Cl(1) 2.313(1), PdCl(2) 2.359(1) A. The very short PdS bond length may indicate a strong σ + π synergistic interaction of the Pd atom with the N-thionitrosodimethylamine ligand. Me2NNS reacts with Pd(PhCN)2Cl2 to give, besides the known cis-Pd(SNNMe2)2Cl2, the complex [μ-Cl)2{Pd(SNNMe2Cl}2] (IIIa), and an unstable compound which is probably [Pd(SNNMe2)4]Cl2. The stable salts [Pd(SNNMe2(BPh4)2 (IVa) and [Pd(SNNMe2)4]HgCl4 (IVd) were obtained from this unstable compound and NaBPh2 or HgCl4. Alternatively the stable salts [Pd(SNNMe2)4](PF6)2 (IVb) and [Pd(SNNMe2)]PdCl4 (IVc) were obtained from Me2NNS and [Pd(diene)(acetone)2](PF6)2 (diene = 1,5-cyclooctadiene, norbornadiene) or Na2PdCl4. Me2NNS reacts with Pt(PhCN)2Cl2 to form an unstable compound probably [Pt(SNNMe2)4]Cl2 which was obtained in the stable form as [Pt(SNNMe2)4]Y2 (Y = BPh4 (Va), PF6 (Vb); Y2 = PtCl4 (Vc)). The complexes [(μ-X)2{Pd(SNNMe2)Cl}2] (X = Cl (IIIa), Br (IIIb), SCN (IIIc), SeCN (IIId)) were prepared by reaction of Pd(PhCN)2Cl2 with Pd(SNNMe2)2X2.

Dicationic (η5-triphenylphosphonium cyclopentadienylide)(η4-diene)palladium(II) and -platinum(II) complexes

Abstract The complexes [M(Ph3PC5H4)(Diene)][PF6]2 (M = Pd, Diene = cycloocta-1,5-diene, norbornadiene; M = Pt, Diene = cycloocta-1,5-diene, norbornadiene, cyclooctatetraene) were prepared by treating the corresponding solvated species [M(Diene)(Acetone)2][PF6]2, generated in situ, with triphenylphosphonium cyclopentadienylide. (The palladium(II) complex with cyclooctatetraene could not be obtained by this method.) The compounds are stable as solids for a long time, but decompose rapidly in solution. The palladium(II) complexes decompose more easily than the analogous platinum(II) species; the stability sequence for variation of the coordinated diene, is: cycloocta-1,5-diene > norbornadiene > cyclooctatetraene. In all the complexes the triphenylphosphonium cyclopentadienylide ligand is η5-coordinated to the metal. In [Pt(Ph3PC5H4)(C8H8)[PF6]2 the cyclooctatetraene has a rigid structure at 25°C. Attempts to isolate methoxy derivatives of the type [M(Ph3PC5H4)(Diene-OCH3)]PF6 failed. The 1H NMR spectra of the complexes are discussed.

Cyclopentadienyl- and pentamethylcyclopentadienyl-rhodium(III) complexes containing isocyanide ligands

Abstract The complexes [(η5-C5H5)RhCl2]2 and [(η5-C5Me5)RhCl2]2 react with stoichiometric amounts of isocyanide ligands L to give (η5-C5H5)RhLCl2 and (η5-C5Me5)RhLCl2 (L = CNC6H11, CNC6H4CH3-p); an excess of ligand L reacts further with (η5-C5Me5)RhLCl2 to give the cationic complex [(η5-C5Me5)RhL2Cl]+ which was isolated as tetraphenylborate salt. The cationic complexes [(η5-C5Me5)RhL(PPh3)Cl]+ and [(η5-C5Me5)Rh(Ph2PC2H4PPh2)Cl]+ were obtained in the reaction of (η5-C5Me5)RhLCl2 with PPh3 and Ph2PC2H4PPh2 respectively. Unidentified solids which do not contain the cyclopentadienyl moiety were obtained in the analogous reactions of (η5-C5H5)RhLCl2 with an excess of isocyanide or of tertiary phosphine. The complexes (η5-C5H5)Rh(CNC6H11)Cl2 and (η5-C5Me5)Rh(CNC6H11)Cl2 react with SCN− or SeCN− giving the corresponding dithiocyanate or diselenocyanate derivatives in which the pseudohalogen groups are S- or Se-bonded to the metal atom. The analogous reactions with C6Cl5MgCl gave the chiral complexes (η5-C5H5)Rh(CNC6H11)(C6Cl5)Cl and (η5-C5Me5)Rh(CNC6H11)(C6Cl5)Cl. The potentially chelating anion Ph2PSS− reacts with (η5-C5H5)Rh(CNC6Hn11)Cl2 and (η5-C5Me5)Rh(CNC6H11)Cl2 to give (η5-C5H5)Rh(CNC6H11)(SSPPh3)Cl and (η5-C5Me5)Rh(CNC6H11)(SSPPh2)Cl in which the dithio ligand acts as monodentate; these compounds react with MeI or EtI to give the dihalide derivatives and the esters Ph2PSSMe and PSSEt. The complex [(η5-C5Me5)Rh(CNC6H11)(SSPPh2)]Cl was obtained by refluxing a benzene solution of the corresponding neutral complex; the cyclopentadienyl derivative failed to give the analogous chelate complex. The complexes (η5-C5H5)RhLCl2, (η5-C5Me5)RhLCl2 and [(η5-C5Me5)RhL2Cl]+ (L = CNC6H11) were found to be unreactive towards amines.