Synthesis and Reactions of Mixed N,P Ligands

Abstract

The gold complexes [RN=C(RЈ)CH(R)PPh 2 (AuCl)] (6a, RЈ = tBu; 6b, RЈ = Ad; R = SiMe 3 ) were synthesised from the ketimines RN=C(RЈ)CH(R)PPh 2 (2a, RЈ = tBu; 2b, RЈ = Ad; R = SiMe 3 ) and Me 2 SAuCl. The hydrolysis of the complexes to [H 2 NC(RЈ)=CHPPh 2 (AuCl)] (8a, RЈ = tBu; 8b, RЈ = Ad) in protic solvents was studied and the reaction intermediate [H(R) NC(tBu)=CHPPh 2 (AuCl)] (7a) was isolated. The ketimines were further reacted with PhPCl 2 to the cyclic phosphonium

Chiral Memory in Silyl-Pyridinium and Quinolinium Cations

“…The solid state structure of 7 also exhibits a N–Si bond length of 1.892 Å, slightly longer than that reported for the trimethylsilylpyridinium iodide (1.858 Å) and much longer than that expected for an iminosilane N–Si bond (1.73 Å) (Table ). Pyramidalization of the silicon center in 7 was assessed through the sum of the covalent bond angles around Si (∑α­(Si) = 345.02°, Table ) and is less pronounced than that in the trimethylsilylpyridinium iodide (∑α­(Si) = 340.8°), yet revealing a rather large distortion from trigonal planar geometry (∑α­(Si) = 360°), which indicates that this system is getting as expected quite far from a true silylium ion. The most prominent feature of this crystal structure arose from a significant deformation of the bond angles in 7 , revealing the important constraint resulting from the formation of the nearly planar four-membered ring (C 1 –C 2 –N–Si, α = 3.0°), with a C 2 –C 1 –Si angle β of 87.93° (instead of 109° in 2 ), and the sum of the angles around the nitrogen of ∑α­(N) = 359.85°, very close to the ideal value.…”

“…The molecular structure of 7 shows a significant separation between the cation and the borate anion as indicated in Figure 2a, with distances (Si-F, N-F and H-F) that are significantly higher than the sum of the van der Waals radii of the corresponding atoms (Σr vdW,Si/F = 3.57 Å, Σr vdW,N/F = 3.02 Å and Σr vdW,H/F = 2.57 Å with r vdW,H = 1.10 Å, r vdW,F = 1.47 Å, r vdW,N = 1.55 Å and r vdW,Si = 2.10 Å). The solid state structure of 7 also exhibits a N-Si bond length of 1.892 Å, slightly longer than that reported for the trimethylsilylpyridinium iodide (1.858 Å) 25 and much longer than that expected for an iminosilane N-Si bond (1.73 Å), 26 reflecting the presence of a highly polarized bond ( Table 1). Pyramidalization of the silicon center in 7 was assessed through the sum of the covalent bond angle around Si (Σα(Si) = 345.02°, Table 1), and is less pronounced than that in the trimethylsilylpyridinium iodide (Σα(Si) = 340.8°), yet revealing a rather large distortion from trigonal planar geometry (Σα(Si) = 360°), which indicates that this system is getting as expected quite far from a true silylium ion.…”

The gold–hydrogen bond, Au–H, and the hydrogen bond to gold, Au⋯H–X

“…153 In a complex of AuCl with a tertiary phosphine bearing an enamine substituent, the amino group is clearly orientated towards the gold atom, but the conformation detected in the crystals has an AuÁ Á ÁH distance of 2.912 Å which does not indicate any major interaction (46). 154 A conformational preference could be inferred in gold(I) complexes of 2-aminophenylphosphines (47) with a gold atom in a rare trigonal planar configuration. However, the authors have pointed out that the AuÁ Á ÁH distances below and above the trigonal plane are in the range of 2.91-3.13 Å and the AuÁ Á ÁH-N angles are quite small (99-1151), casting doubt on the significance of these contacts.…”

Bidentate amino- and iminophosphine ligands in mono- and dinuclear gold(I) complexes: Synthesis, structures and AuCl displacement by AuC6F5

“…For example, various studies of gold(I) have been related to anti-arthritic [7,8], anti-tumour [7,9] and anti-microbial physiological activities [10,11]. Although gold(I) mono-and bisphosphine compounds have been extensively studied [12] together with their mechanisms of cytotoxity and anti-tumour activity [13], bidentate gold(I) compounds that utilise both a hard and soft donor atom are only poorly represented in the literature [14]. Among the 'hard' donor type atoms, the co-ordination chemistry of gold(I) oxygen compounds [15,16] shows a distinct paucity in the literature, while gold(I) complexes with nitrogen donor functions are more common yet less stable than their phosphine analogues [17,18].…”