Square-planar metal(II) complexes containing ester functionalised bis(phosphino)amines: Mild P−N methanolysis and Carene−H cyclometallation

Abstract

a b s t r a c tThe synthesis of three new ester functionalised bis(phosphino)amines Ph 2 PN{R}PPh 2 [R ¼ C 6 H 4 (3-CO 2 Me) 1a; C 6 H 3 (3,5-CO 2 Me) 2 1b; C 6 H 4 (4-CO 2 Me) 1c] upon stoichiometric reaction of Ph 2 PCl and the appropriate H 2 N{R} in Et 2 O is described. Reaction of 1 equiv. of 1aÀc with MCl 2 (cod) (M ¼ Pt, Pd) in CH 2 Cl 2 afforded the dichlorometal(II) complexes PtCl 2 (1a) 2a, PtCl 2 (1b) 2b, PtCl 2 (1c) 2c and PdCl 2 (1b) 2`b respectively. The corresponding dibromo (and diiodo) platinum(II) complexes 3b (and 4b) were synthesised, in >80% isolated yields, from PtBr 2 (cod) or PtI 2 (cod). When a suspension of 2b in MeOH was stirred at r.t. for ca. 16 h the mixed complex cis-PtCl 2 [Ph 2 PNH{R}](Ph 2 POMe) 5a [R ¼ C 6 H 3 (3,5-CO 2 Me) 2 ] was cleanly generated. Metathesis of 5a using excess NaBr or NaI in MeOH/acetone afforded cisPtBr 2 [Ph 2 PNH{R}](Ph 2 POMe) 5b or cis-PtI 2 [Ph 2 PNH{R}](Ph 2 POMe) 5c. Methanolysis of PtCl 2 (1a) 2a at ambient temperature afforded, in low yield (18%), the regiospecific P,C-orthometallated complex cis-PtCl [Ph 2 PNH{C 6 H 3 (3-CO 2 Me)}](Ph 2 POMe) 6. We speculate the CÀH activated complex 6 is obtained via initial formation of cis-PtCl 2 [Ph 2 PNH{C 6 H 4 (3-CO 2 Me)}](Ph 2 POMe) 7. A similar observation was also found using 2c whereupon examination of the isolated solid, by 31 P{ 1 H} NMR spectroscopy, revealed formation of three complexes namely orthometallated cis-PtCl[Ph 2 PNH{C 6 H 3 (4-CO 2 Me)}](Ph 2 POMe) 9, cis-PtCl[Ph 2 PNH{C 6 H 4 (4-CO 2 Me)}](Ph 2 POMe) 10 and cis-PtCl 2 (Ph 2 POMe) 2 8. All new compounds reported here have been characterised by multinuclear NMR and IR spectroscopy, microanalysis and in six cases by single crystal X-ray crystallography. The X-ray structure of cis-PtCl[Ph 2 PNH{C 6 H 3 (3-CO 2 Me)}](Ph 2 POMe) 6 revealed selective CÀH cycloplatination at the 6-position (as opposed to the 2-position) of the N-arene ring.

Functional Short-Bite Ligands: Synthesis, Coordination Chemistry, and Applications of N-Functionalized Bis(diaryl/dialkylphosphino)amine-type Ligands

“…Smith and colleagues reported the synthesis of two other DPPA-type ligands of general formula Ph 2 PN­(R)­PPh 2 [R = C 6 H 4 (3-CO 2 Me) ( 102 ), C 6 H 4 (4-CO 2 Me) ( 103 )] (Scheme ), which carry on their nitrogen atom a mono-ester-aryl function . These diphosphine ligands exhibit a single 31 P NMR resonance at 69.0 ( 102 ) and 68.5 ( 103 ) ppm, very close to that of the bis-ester derivative 99 (see above and Table ).…”

“…Both dinuclear Au(I) complexes were characterized in the solid-state by XRD studies and revealed a typical linear coordination geometry for the Au(I) 22), which carry on their nitrogen atom a mono-ester-aryl function. 72 These diphosphine ligands exhibit a single 31 P NMR resonance at 69.0 (102) and 68.5 (103) ppm, very close to that of the bis-ester derivative 99 (see above and Table 9). 71 The authors investigated the coordination chemistry of ligands 102 and 103, along with that of ligand 99, toward the group 10 metal centers of [MX 2 (COD)] (M = Pt, Pd; X = Cl, Br, I) (Scheme 22).…”

“…The authors observed that complexes 104 and 109 reacted with MeOH at room temperature, leading to clean and selective cleavage of one P−N bond, to afford complexes 110 and 111, respectively (Scheme 22). 72 The NMR and structural data of these monophosphine complexes will not be further discussed here.…”

The Backbone of Success of P,N-Hybrid Ligands: Some Recent Developments

“…Cu contacts [40]. We showed that PNP ligands, with ester groups on the central -N(arene)-core (e.g., 2g) could be synthesised from the amine/ClPPh 2 /NEt 3 in Et 2 O [41]. Ligands such as 2h could be prepared from Me 3 SiN(R')SiMe 3 /2 equiv.…”

The novel [Ni{(Ph2P)2N(CH2)3Si(OCH3)3-P,P´}I2] complex: Structural features and catalytic reactivity in the oligomerization of ethylene

“…[25] The main bond lengths and angles of the later, along with those of complexes 1 and 2 [17], are listed in Table 2. It should be noted that the structure of one [Pd(P,P)I 2 ] complex (bearing one Me and three Ph as R groups and R′ = i Pr) [26] and two [Pt(P,P)I 2 ] complexes (R = Ph, R′ = C 6 H 4 (CO 2 CH 3 ) [27] or Ph [28]), have been reported and are available in the CSD.…”