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Complexes [M(η¹,η²-C8H12OMe)(pz2-YH2)]⁽⁺⁾ (M = Pd, Y = C, 1; M = Pt, Y = C, 2; M = Pt, Y = B, 3) and [M(η¹,η²-C8H12OMe)(pz3-YH)]⁽⁺⁾ (M = Pd, Y = C, 4; M = Pd, Y = B, 5; M = Pt, Y = C, 6; M = Pt, Y = B, 7) were synthesized by the reaction of the dimers [M(η¹,η²-C8H12OMe)Cl]2 with the poly(pyrazol-1-yl)borate and -methane ligands. Complexes 1−7 were characterized in solution by multinuclear and multidimensional low-temperature NMR spectroscopy. The solid-state structures of olefinic five-coordinate Pd complexes 4 and 5 were investigated by X-ray single-crystal studies. The relative cation−anion position (interionic structure) was investigated in solution, for all cationic complexes at room and low temperature by ¹⁹F, ¹H-HOESY NMR spectroscopy, and in the solid state for 4. A remarkable specifity of the interionic contacts is observed in solution:  the counterion is placed close to the peripheral protons of the pyrazolyl ligands probably due to the partial protection of the apical positions introduced by the nonplanar ligands and the delocalization of the positive charge on the pyrazolyl rings. In the case of complex 4 there is an excellent agreement between the solid state and solution results:  the anion selectively interacts with the CH and five protons of the pz3-CH ligand via an assembly of hydrogen bonds.

The reaction of the complexes cis,trans-[OsI(Me)(CO)2(PMe3)2] and fac-[OsI(Me)(CO)3(PMe3)] with silver salts (AgX) and bis- and tris(pyrazol-1-yl)methane ligands affords the complexes [Os(COMe)((pz)2CH2)(CO)(PMe3)Y]⁺[BPh4]^- (Y = PMe3, CO) and [Os(COMe)((pz)3CH-κ²)(CO)(PMe3)Y]⁺[BPh4]^- (Y = PMe3, CO) or the solvento complexes cis,trans-[Os(Me)(S)(CO)2(PMe3)2]⁺X^- depending on the reaction conditions. In the reaction of cis,trans-[OsI(Me)(CO)2(PMe3)2] with AgX in the presence of (pz)3CH, the intermediate complexes [(Me)(CO)2(PMe3)2Os(μ-I)Ag((pz)3CH)]⁺[X]^- (X^- = CF3SO3^-, BF4^-) were isolated. The solution interionic structures of cationic complexes were investigated by ¹H NOESY or ¹⁹F{¹H} HOESY NMR spectra.

Complexes [Pd(η¹,η²-C8H12OMe)bipy]⁺X^- (2a−f) (where X = BPh4^- (a), CF3SO3^- (b), BF4^- (c), PF6^- (d), SbF6^- (e), and B(3,5-(CF3)2C6H3)4^- (f); bipy = 2,2‘-bipyridine; C8H12OMe = cyclooctenylmethoxy group) were synthesized by the reaction of the dimer [Pd(η¹,η²-C8H12OMe)Cl]2 (1) with the bipy ligand in methanol containing Y⁺X^- salts. They were characterized in solution by multinuclear and multidimensional NMR spectroscopy. The solid-state structure of complex 2d was obtained by X-ray single-crystal investigation. The catalytic activity of complexes 2 toward CO/styrene copolymerization in methylene chloride was tested and related to the type of counterion. The order of the catalytic activity of complexes 2a−f is the following:  BPh4^- ≪ CF3SO3^- < BF4^- < PF6^- < SbF6^- < B(3,5-(CF3)2C6H3)4^-. If the copolymerization reactions are carried out in the presence of an excess of the bipy ligand, the anion effect is less important and the order is the following:  BPh4^- ≪ CF3SO3^- < BF4^- ≈ B(3,5-(CF3)2C6H3)4^- ≈ PF6^- ≈ SbF6^-. The interionic structure of all complexes was investigated in CD2Cl2 at room and low temperature by ¹⁹F{¹H} HOESY and ¹H NOESY NMR spectroscopies. In solution, the counterions are located above or below the bipy ligand shifted toward the pyridine ring trans to the Pd−C σ bond, while in the crystal structure of 2d, they are settled sideways to the cationic moiety. The best anion in catalysis is the least strong coordinating one that shows the weakest interionic contacts in the ¹⁹F{¹H} HOESY or ¹H NOESY NMR spectra. The dynamic process that exchanges the two pyridyl rings was investigated by variable-temperature NMR spectroscopy in CD2Cl2. The activation parameters were determined. ΔG^&thermod;298 values range from 54 to 58 kJ/mol. The negative values of ΔS^&thermod; (−58/−108 J K^-1 mol^-1), for all compounds, with the exception of 2f, suggest an associative mechanism.

Complex fac-Ru(PMe3)(CO)3(Me)I (1) reacts with tris- and bis(pyrazol-1-yl)methane, in the presence of NaBPh4, affording cis-[Ru(PMe3)(CO)2(COMe)(η²-pz3-CH)]BPh4 (2) and cis-[Ru(PMe3)(CO)2(COMe)(pz2-CH2)]BPh4 (4), respectively. Complexes 2 and 4 decarbonylate leading to [Ru(PMe3)(CO)(COMe)(η³-pz3-CH)]BPh4 (3) and a mixture of three methyl stereoisomers of cis-[Ru(PMe3)(CO)2(Me)(pz2-CH2)]BPh4 (5−7), respectively. The byproduct of the synthesis of 1, fac,cis-Ru(PMe3)(CO)3(I)2 (8), reacts with bis(pyrazol-1-yl)methane affording cis-[Ru(PMe3)(CO)2(I)(pz2-CH2)]BPh4 (9). The stereochemistry of the complexes, the dynamic processes existing between them, and the interionic structures of all of the cationic complexes were investigated by the phase-sensitive ¹H NOESY NMR spectra in CD2Cl2. The solid-state crystal structure of 4, obtained by single-crystal X-ray studies, was compared from the intramolecular and interionic point of views with that in solution with the help of 3-21G* ab initio and AMI−SM2 semiempirical quantum mechanical and docking mechanic calculations. In particular, the differences of interaction energy of the six solid-state ion pairs determined by the cation and the six symmetry-related anions surrounding it were estimated. The main result is that the averaged preferred position of the counterion in solution corresponds to the ion-pair electrostatically (ΔEel > 2.5 kcal/mol) and “sterically” (ΔEst > 3.7 kcal/mol) favored in the solid state.

The reactions of complexes trans, cis-M(PMe3)2(CO)2(Me)I (M = Fe (1a), Ru (1b)) with N,O ligands [2-acetylpyridine (2-apy), 2-benzoylpyridine (2-bzpy), and 2,2‘-dipyridyl ketone (2,2‘-dpk)] in the presence of NaBPh4 afford a mixture of the two possible stereoisomers trans-[M(PMe3)2(CO)(COMe)(N, O)]BPh4 having the N arm cis (A) or trans (B) to the acetyl group. The stereochemistry of the complexes was determined by ¹H NOESY NMR spectra. For all the iron complexes the major stereoisomer is B, while for ruthenium complexes it is A. When A/B mixtures are left in methylene chloride, the concentration of A increases, indicating that A and B are the thermodynamic and kinetic reaction products, respectively. Furthermore, the more basic the N,O ligands, the more B stereoisomer that forms. The solid-state structure of 4b was obtained using single-crystal X-ray diffraction. For all the complexes, the ion-pair structures and the localization of the counterion in solution with respect to the organometallic moiety were investigated by the detection of interionic contacts in the ¹H NOESY NMR spectra. Specific interactions were observed that indicate that the counterion is localized in solution in front of the face determined by PMe3 and the two arms of the N,O ligands.

The complexes trans,cis-M(PMe3)2(CO)2(Me)I (M = Fe and Ru, 1a,b) react with bis- and tris(pyrazol-1-yl)methane, in the presence of NaBPh4, affording trans-[M(PMe3)2(CO)(COMe)(pz2-CH2)]BPh4 (2a,b) and trans-[M(PMe3)2(CO)(COMe)(η²-pz3-CH)]BPh4 (3a,b), respectively (pz = pyrazolyl ring). The reactions of 1b with 5,5‘-Me2-pz2-CH2 and 3,5‘-Me2-pz2-CH2 produce trans-[Ru(PMe3)2(CO)(COMe)(5,5‘-Me2-pz2-CH2)]BPh4 (4) and trans-[Ru(PMe3)2(CO)(COMe)(3,5‘-Me2-pz2-CH2)]BPh4 (5), respectively. A mixture of trans,cis-[Ru(PMe3)2(CO)2(η¹-3,3‘-Me2-pz2-CH2)(Me)]BPh4 (6) and trans-[Ru(PMe3)2(CO)(COMe)(3,3‘-Me2-pz2-CH2)]BPh4 (7) is obtained from reaction of 1b and 3,3‘-Me2-pz2-CH2. The reactions of 2−7 with nucleophiles either give back the starting complex (Nu = I^-) or analogous complexes (Nu = Br^- and Cl^-) or produce decomposition products of the complexes (Nu = I2, Br2, Cl2, and OMe^-). The solid state structures of 2b and 3b were obtained using single-crystal X-ray diffraction. For all complexes, 2−7 as well as complex 8 (analogue to 2a, having a BF4^- counterion instead of BPh4^-), the ion-pair structures and the localization of the counterion in solution with respect to the organometallic moiety were investigated by the detection of interionic contacts in the ¹H-NOESY and ¹⁹F{¹H}-HOESY NMR spectra.

The disubstitution reaction Co(NO)(CO)2L+L = Co(CO)(NO)L2+CO has been investigated for a series of phosphine and phosphite ligands, in toluene solution up to about 65°C. Dissociative and associative reaction paths are generally competitive, their relative weights being strongly dependent on the properties of the ligand L.

The dipole moments of the complexes π (CH2CXCH2) Fe (CO) (NO) L, with X and L equal, respectively, to H, CO; H, P (C6H5)3; CH3, CO; Cl, CO; Br, CO, have been measured. From the results it is concluded that: