Anna Laura Bandini

Preparation and characterization of palladium(II) and platinum(II) complexes with bis(pyrazolyl)alkanes. crystal and molecular structures of [Pd2(pz)22][BF4]2 and of [PdCl2{(CH3)2C(pz)2}] (pzH = pyrazole), a new example of a Pd⋯HC agostic interaction

Abstract Neutral and cationic complexes of general formulae (LL)MCl 2 (M = Pd, (LL) = CH 2 (pz) 2 ( 1 ); CH 2 (3,5-Me 2 pz) 2 ( 2 ); (CH 3 ) 2 C(pz) 2 ( 3 ); M = Pt, (LL) = CH 2 (pz) 2 ( 4 ); CH 2 (3,5-Me 2 pz) 2 ( 5 ) and (LL) 2 M] 2+ (M = Pd, (LL) = CH 2 (pz) 2 ( 6 ); CH 2 (3,5-Me 2 pz) 2 ( 7 ); (CH 3 ) 2 C(pz) 2 ( 8 ); M = Pt, (LL) = CH 2 (pz) 2 ( 9 ); CH 2 (3,5-Me 2 pz) 2 ( 10 ) have been prepared and characterized by IR and 1 H NMR spectroscopy. The structures of 3 and 6 have been determined by X-ray diffraction; in both complexes the bis-(pyrazolyl)alkanes act as chelating ligands but the coordination around the palladium atom in the complex 6 is strictly square-planar whereas in 3 it is a slightly distorted towards pyramidal, with a significant Pd⋯HC agostic interaction. The six-membered rings in both the complexes adopt a boat-type conformations.

Reaction of platinum(II) derivatives with bis(pyrazolyl)propane. Cleavage of a C(sp3)-N bond in a bis(pyrazolyl)alkane promoted by platinum(II) derivatives. Crystal structure of cis-Pt(pzH)2CL2 (pzH = pyrazole)

The reactions of bis(pyrazolyl)propane (CH3)2C(pz)2, (pzH = pyrazole), with PtCl2, (RCN)2PtCl2 and K2[PtCl4 have been investigated, and the results compared with those described previously for the corresponding palladium(II) derivatives. In contrast with the behaviour of the palladium analogues, the platinum derivatives promote the rupture of the ligand: simple adducts of pyrazole, cis- or trans-Pt(pzH)2Cl2, or species containing the ligand [HNC(R)pz], formally arising from the insertion of a nitrile into the NH bond of pyrazole, are obtained. For comparison, the reaction of the platinum derivatives with pyrazole itself has been investigated under various conditions. The crystal structure of cis-Pt(pzH)2Cl2 has been determined by X-ray diffraction: monoclinic, space group C2/c, a 9.180(1), b 15.084(1), c 15.1445(9) A, β 101.536(7)°, Z - 8, R = 0.039, Rw = 0.040 for 2125 observed reflections.

Carbonylrhodium(I) derivatives of 3,5-dimethyl- and 3,5-bis(trifluoromethyl)pyrazole

Abstract Binuclear pyrazolato-bridged complexes such as [(OC) 2 Rh(μ-pyrazolato- N,N ′] 2 , I or II, were obtained in alkaline solution from (OC) 4

A Series of monohapto pyrazolates of iridium(I) and iridium(III)

Abstract The reaction of trans -IrCl(CO)L 2 with pz − 1 gives trans -Ir(pz- N )(CO)L 2 , where pzH is 3,5-dimethyl-, 3,5-dimethyl-4-nitro- or 3,5-bis(trifluoromethyl)-pyrazole, and L = PPh 3 . The nitrogen atom not involved in coordination can be protonated with HBF 4 to give the corresponding [Ir(CO)L 2 (pzH- N ] + cation. The iridium(I) pyrazolates undergo oxidative addition, yielding Ir(H) 2 (pz- N )(CO)L 2 species, while gaseous HCl cleaves the IrN bond, affording IrH(Cl) 2 (CO)L 2 . The iridium(I) derivatives can be obtained in several solid-state forms, each characterized by a slightly different CO stretching frequency. The presence of a monodentate pyrazolato ligand in trans -Ir(3,5-(CF 3 ) 2 pz- N )(CO)L 2 , in the form with ν(CO) at 1975 cm −1 , is supported also by an X-ray crystal structure determination. The compound crystallizes in the monoclinic system, space group P 2 1 / n , with cell dimensions a = 21.106(6), b = 19.700(5), c = 9.437(2) A, and β = 94.34(2)° and Z = 4.

FAB Mass Spectrometry of Palladium(II) Derivatives with 1,4-Benzodiazepin-2-ones: Evidence of the Stability of Cyclometallated Species

Abstract The FAB spectra of the adducts trans-Pd(L)2Cl2 (1: L=DIAZEPAM, D=7-chloro-1,3-dihydro-1- methyl-5-phenyl-2H-1,4-benzodiazepin-2-one; 2: L= PRAZEPAM, P=7-chloro-1-(cyclopropylmethyl)-1,3- dihydro-5-phenyl-2H-1,4-benzodiazepin-2-one) and of the cyclometallated derivatives [Pd(L=H)Cl]2 (L=D, 3; L=P, 4), Pd(Ph3P)(L=H)X (L=P, X=Cl, 5; L=D, X=Br, 6), Pd(D)(D=H)Cl (7) have been studied in detail. The main gas-phase fragmentation pathways of 1 and 2 consist in sequential HCl losses, while for compounds 3 and 4 only primary Cl· loss is observed. A peculiar behaviour is observed for 5 and 6, i.e. the lack of protonated molecular ions.

Mono and dinuclear gold(I) complexes with neutral and deprotonated 1,4-benzodiazepin-2-ones. Crystal and molecular structure of (L-H)Au(PPh3)·Et2O, where L = 1,3-dihydro-7-nitro-5-phenyl-2H-1,4-benzodiazepin-2-one, nitrazepam

Abstract The preparation of a series of neutral (L)AuCL (1a–3a) and cationic [(L)Au(PPh3)] [BF4] (1b–5b) gold(I) complexes is described (L = DIAZEPAM, 1; PRAZEPAM, 2; NITRAZEPAM, 3; LORAZEPAM, 4; NIMETAZEPAM, 5). In the presence of alkali, (PPh3)AuCl reacts with 1-unsubstituted 1,4-benzodiazepin-2-ones such as NITRAZEPAM (3) and LORAZEPAM (4) to give neutral gold(I) species (L-H)Au(PPh3) (3c and 4c). The benzodiazepine anion is bonded to Au via the N(1) atom, as shown, in the case of 3c, by X-ray analysis: (L-H)Au(PPh3)·Et2O, C33H25AuN3O3P· C4H10O, monoclinic, space group P21/c, a= 12.717(9), b=19.270(7), c=14.696(3) A, β= 107.85(3)°, Z= 4. AuP = 2.238(1), AuN = 2.071(3) A. The crystal structure was determined by standard methods and refined to R = 0.028 and Rw = 0.035 on the basis of 4456 unique reflections. p ]The complex 3c reacts with [(Ph3P)Au(S)][BF4], as obtained from (PPh3)AuCl and AgBF4 in methanol, to give the dinuclear cationic species [(Ph3P)Au{μ(L-H)}Au(PPh3)] [BF4] (3d) where the deprotonated NITRAZEPAM bridges two (Ph3P)Au groups through the N(1) and N(4) atoms. All the new derivatives were characterized by elemental analyses and spectroscopic methods (IR; 1H, 31P NMR).

Some gold(III) derivatives of pyrazoles

Abstract Various gold(III) derivatives of pyrazoles, pzH, were obtained and characterized. Besides the salt [3,5-Ph2pzH2][AuCl4], they included adducts, AuCl3·pzH, μ-pyrazolato-N,N′-derivatives, [Cl2Au(pz)]n (such as: n = 2 and pz = 3,5-diphenyl-4-chloropyrazolato), and one derivative containing both a neutral pyrazole and a pyrazolato ligand, Cl2Au(3,5-Ph2pz-N)(3,5-Ph2pzH).

Binuclear hydrido platinum(II) complexes: syntheses of [{Pt(PP)}2(μ-CHCH2R)(μ-H)][BF4] (R=C6H5, H) and easy cleavage of a PC bond in a chelating 1,4-bis (diphenyl)phosphinobutane (PP)

Abstract Reactions of the binuclear platinum(II) trihydrido complex, [Pt2{(Ph2P)2(CH2)4}2(H)3][BF4], with styrene or ethylene, at room temperature and low pressure, give μ-alkylidene, μ-hydrido cationic species [Pt2{(Ph2P)2(CH2)4}2(μ-CHCH2R)(μ-H)][BF4] (R=C6H5, 1; H, 2) together with an unexpected phosphido-bridged binuclear platinum(II) compound (3), originating from cleavage of a PC bond in the coordinated diphosphine. Complexes 1–3 are discussed on the basis of FAB MS, IR and multinuclear NMR spectra in solution.

X-ray crystal Structure of [1,2-bis(diphenylphosphino)ethane]bis(3,5-dimethylpyrazole-N)platinum(II) tetrafluoroborate dichloromethane solvate, [(Ph2PCH2CH2PPh2)Pt(3,4-Me2pzH)2][BF4]2·CH2Cl2

Abstract The crystal structure of the compound [(Ph2PCH2CH2PPh2)Pt(3,5-Me2pzH)2][BF4]2·CH2Cl2 has shown that the ligands around the Pt atom are approximately in a square planar coordination, whereas the pyrazole rings point roughly in the same direction, away from the coordination plane. This unusual conformation is probably due to the hydrogen bonds with fluorine atoms of the BF4− anion. Bond distances and angles are compared with those in other pyrazole complexes.

A series of pyrazole adducts and pyrazolato derivatives of platinum(II) containing various chelating phosphines as ligands: Characterization, 1H and 31P{1H} NMR spectra

New pyrazolato derivatives of platinum(II) are isolated, (LL)Pt(pz)2, A, [LL = Ph2P(CH2)nPPh2 (n = 1, 2, 3, or 4), Ph2PCH2CH2AsPh2, (Ph2AsCH2)2 or cis-Ph2PCHCHPPh2; pzH = pyrazole, 3,5-dimethyl,- 3,5-bis(trifluoromethyl)-, or 3,5-dimethyl-4-nitro-pyrazole] by reaction of (LL)PtCl2 with pyrazole and potassium hydroxide in methanol. By protonation of A with fluoboric acid the corresponding pyrazole adducts, [(LL)Pt(pzH)2][BF4]2, B, are obtained when pzH is 3,5-dimethylpyrazole. The properties of the compounds are discussed on the basis mainly of the NMR evidence; 31P data are related to the dimension of the PtP(C)nP ring (n = 1–4) and to the trans-influence of the pyrazolato and pyrazole ligand.