J.G.P. Delis

Insertion reactions involving palladium complexes with nitrogen ligands I. Reactivity towards carbon monoxide of methylpalladium(II) complexes containing bidentate α-diimine ligands: crystal structures of four methylpalladium(II) and acylpalladium(II) complexes

Abstract Neutral compounds of the type (2,2′-bipyridine)Pd(CH3)(Cl) and 6-R′ue5f8C5H3N-2-C(H)=Nue5f8R)Pd(CH3)(Cl) ( R = i Pr ; R ′ = H : i Pr ue5f8 PyCa ) ( R = t Bu ; R ′ = H : t Bu-PyCa ) ( R = i Pr ; R ′ = CH 3 : i Pr -6- Me ue5f8 PyCa ) (R = CH2CH2C6H5;R′ = H: Pheue5f8PyCa) ( R = t Bu ; R ′ = CH 3 : t Bu -6- Me ue5f8 PyCa ) ( R = i Pr ; R′ = C ( H ) O : i Pr ue5f8 IPA ) have been synthesized starting from (1,5-cyclooctadiene)Pd(CH3)(Cl) and ionic compounds of the type [(N-N)Pd(CH3)]BF4 (Nue5f8N = bipy, iPrue5f8PyCa, tBuue5f8PyCa or iPr-6-Meue5f8PyCa) by treatment of the methyl(chloro)palladium compounds with silver tetrafluoroborate. All products have been characterized by spectroscopic methods. Reaction of the compounds with carbon monoxide gives that neutral acyl compounds (Nue5f8N)Pd(C(O)CH3)(Cl) and ionic acyl compounds [(Nue5f8N)Pd(C(O)CH3)]BF4 (Nue5f8N = bipy, iPrue5f8Pyca, tBuue5f8PyCa, iPr-6-Meue5f8PyCa or Pheue5f8PyCa). The crystal structures of (iPr-6-Meue5f8PyCa)Pd(CH3)(Cl), (iPrue5f8IPA)Pd(CH3)(Cl), (bipy)Pd(C(O)CH3)(Cl) and (iPrue5f8PyCa)Pd(C(O)CH3(Cl), have been determined. Comparison of data for the Pdue5f8Nue5fbCue5f8C5H4N moieties of the complexes concerned show that the geometries are almost identical, the largest r.m.s. deviation (between (iPr-6-Meue5f8PyCa)Pd(CH3)(Cl) and (bipy)Pd(C(O)CH3)(Cl)) being 0.2 A. The Pdue5f8C bond distances in the two acetylpalladium complexes are 0.05 A shorter than those in the two methylpalladium complexes. The Pdue5f8N bond distances for the nitrogen atoms situated trans to the organic group are shorter by 0.11 A in the case of acetyl ligands. An unprecedented influence of the steric properties of the ligands on the half-life for the CO insertion is observed; substituents adjacent to the nitrogen donor atoms cause strongly acceleration.

Coordination chemistry of 1,1'-bis(2-pyridyl)ferrocene in palladium(II) and platinum(II) Complexes and Reaction of (BPF)Pd(Me)Cl with CO. X-Ray Structure of (1,1'-bis(2-pyridyl)ferrocene)Pd(Me)Cl and (1,1'-bis(2-pyridyl)ferrocene)[PtCl2(CH2=CH2)]2

Abstract The coordination chemistry of the ligand 1,1′-bis(2-pyridyl)ferrocene (BPF) towards palladium and platinum has been studied. The very stable complexes (BPF)Pd(Me)Cl and BPF[PtCl2(CH2 ue5fb CH2)]2 have been synthesized from (COD)Pd(Me)Cl and Zeises salt respectively and characterized by 1H-, 13C-NMR, elemental analysis and single crystal X-ray determination. The crystals of (BPF)Pd(Me)Cl crystallize in he monoclinic space group C2 c (No.15) with a = 17.4681(9), b = 9.1112(6), c = 27.598(2) A , β= 92926(5)° V = 4360.3(5) A 3 , Z = 8 . The structure refinement converged to R1 = 0.042 for 3541 F0 > 4σ(F0) and wR2 = 0.084 for all 4982 unique reflections. The X-ray structure shows a square planar palladium complex with the ligand coordinated in a bidentate way with a relatively large bite angle of 84.48(13)°. The crystals of BPF[PtCl2(CH2 ue5fb CH2)]2 have the space group P2 1 n with a = 13.8584(9), b = 13.128(3), c = 14.807(1) A and β = 90.13(1)°, V = 2693.9(7) A 3 , Z = 4 . The structure refinement converged to R = 0.043 for 4310 observed reflections. This structure contains two PtCl2(CH2 ue5fb CH2) fragments bridged by one BPF ligand. A fast CO insertion occurs into the palladium-methyl bond of the complex (BPF)Pd(Me)Cl. When the product of this reaction, (BPF)Pd(C(O)Me)Cl, is kept under an atmosphere of 13CO, low temperature NMR and IR measurements show the presence of four complexes, which are (BPF)Pd(C(O)Me)Cl and probably (BPF)Pd(C(O)Me)(CO)Cl, cis- and trans-Pd2(CO)2(C(O)Me)2Cl2. Both the complexes (BPF)Pd(Me)Cl and (BPF)Pd(C(O)Me)Cl show a fluxional behaviour of the coordinated PBF ligand in solution on the NMR time scale, which involves the interconversion of two enantiomers of the complexes and the exchange of the two pyridyl groups of the ligand. BPF(PtCl2(CH2 ue5fb CH2)]2, in which the ethylene is tightly coordinated to the metal centre, reacts with an additional BPF ligand to give the four-coordinated complex (BPF)PtCl2(CH2 ue5fb CH2).

Alkene rotation in [Ru(η5-C5H5) (L2) (η2-alkene][CF3SO3] with L2 = iPr- or pTol-diazabutadiene. X-ray crystal structure of [Ru(η5-C5H5(pTol-DAB) (η2-ethene][CF3SO3]

Reaction of RuCl(η5-C5H5(pTol-DAB) with AgOTf (OTf = CF3SO3) in CH2Cl2 or THF and subsequent addition of L′ (L′ = ethene (a), dimethyl fumarate (b), fumaronitrile (c) or CO (d) led to the ionic complexes [Ru(η5-C5H5)(pTol-DAB)(L′)][OTf] 2a, 2b and 2d and [Ru(η5-C5H5)(pTol-DAB)(fumarontrile-N)][OTf] 5c. With the use of resonance Raman spectroscopy, the intense absorption bands of the complexes have been assigned to MLCT transitions to the iPr-DAB ligand. The X-ray structure determination of [Ru(η5-C5H5)(pTol-DAB)(η2-ethene)][CF3SO3] (2a) has been carried out. Crystal data for 2a: monoclinic, space group P21/n with a = 10.840(1), b = 16.639(1), c = 14.463(2) A, β = 109.6(1)°, V = 2465.6(5) A3, Z = 4. Complex 2a has a piano stool structure, with the Cp ring η5-bonded, the pTol-DAB ligand σN, σN′ bonded (Ru-N distances 2.052(4) and 2.055(4) A), and the ethene η2-bonded to the ruthenium center (Ru-C distances 2.217(9) and 2.206(8) A). The C = C bond of the ethene is almost coplanar with the plane of the Cp ring, and the angle between the plane of the Cp ring and the double of the ethene is 1.8(0.2)°. The reaction of [RuCl(η5-C5H5)(PPh)3 with AgOTf and ligands L′ = a and d led to [Ru(η5-C5H5)(PPh3)2(L′)]OTf] (3a) and (3d), respectively. By variable temperature NMR spectroscopy the rottional barrier of ethene (a), dimethyl fumarate (b and fumaronitrile (c) in complexes [Ru(η5-C5H5)(L2)(η2-alkene][OTf] with L2 = iPr-DAB (a, 1b, 1c), pTol-DAB (2a, 2b) and L = PPh3 (3a) was determined. For 1a, 1b and 2b the barrier is 41.5±0.5, 62±1 and 59±1 kJ mol−1, respectively. The intermediate exchange could not be reached for 1c, and the ΔG# was estimated to be at least 61 kJ mol−. For 2a and 3a the slow exchange could not be reached. The rotational barrier for 2a was estimated to be 40 kJ mol−. The rotational barier for methyl propiolate (HC≡CC(O)OCH3) (k) in complex [Ru(η5-C5H5)(iPr-DAB) η2-HC≡CC(O)OCH3)][OTf] (1k) is 45.3±0.2 kJ mol−1. The collected data show that the barrier of rotational of the alkene in complexes 1a, 2a, 1b, 2b and 1c does not correlate with the strength of the metal-alkene interaction in the ground state.