From Unsymmetrically Substituted Benzamidinato and Guanidinato Dichlorohydridosilanes to Novel Hydrido N-Heterocyclic Silylene Iron Complexes

Abstract

Starting from the unsymmetric N,N′-substituted thiourea compounds (R)N(H)C(S)N(H)( t Bu) (1, R = Dipp: 2,6-i Pr 2 -C 6 H 3 ; 2, R = 1-adamantyl), the corresponding asymmetric carbodiimines (R)NCN( t Bu) (3, R = Dipp; 4, R = 1-adamantyl) are readily accessible in high yields upon reduction with LiHMDS (Li[N(SiMe 3 ) 2 ]). The reaction of compound 3 with PhLi followed by SiCl 4 afforded, in a onepot reaction, the asymmetric benzamidinato-stabilized trichlorosilane [PhC{(N t Bu)(NDipp)}]SiCl 3 (5). Similarly, silanes [PhC{(N t Bu)(NDipp)}]SiHCl 2 (6), [(NMe 2 )C{(N t Bu)(NDipp)}]SiHCl 2 (7), and [PhC{(N t Bu)(NAd)}]SiHCl 2 ( 8) could also be isolated. All novel trichloro-or dichlorohydridosilanes were fully spectroscopically characterized and studied by single-crystal X-ray diffraction analyses, the latter revealing in all cases a distorted-trigonal bipyramidal five-coordinate silicon center. The reactions of silanes 5−8 with K 2 [Fe(CO) 4 ] were also explored: In the case of the reaction of silane 5 with K 2 [Fe(CO) 4 ], no reaction was observed even after prolonged heating. However, in the case of the silanes 6−8, the selective formation of the corresponding hydrido Si II :→Fe 0 complexes [[R 1 C{(N t Bu)(NR 2 )}](H)Si:→Fe(CO) 4 ] (9, R 1 = Ph, R 2 = Dipp; 10, R 1 = NMe 2 , R 2 = Dipp; 11, R 1 = Ph, R 2 = 1-adamantyl) could be achieved. Complexes 9−11 represent unprecedented hydrido-N-heterocyclic silylene complexes, bearing asymmetric ligand backbones. Complexes 9−11 were fully spectroscopically characterized, and in addition the single-crystal X-ray structure analysis of compound 10 is reported.

Synthesis, structure and reactivity of a donor-stabilised silylene with a bulky bidentate benzamidinato ligand

“…The two silicon coordination polyhedra are distorted tetrahedra (S-Si-S: 96.54(3)°; S-Si-N: 105.70(5)-118.51(5)°; N-Si-N: 113.39(7)°). The Si-S bond lengths range from 212.43(7) pm to 216.83(7) pm, and the Si-N dis-tances from 169.90 (15) pm to 178.31 (14) pm. The monodentate binding mode of the two amidinato ligands is also clearly reflected by the relatively short Si-N1 distance (178.31( 14) pm) and the different N1-C1 (140.1(2) pm; single bond character) and N2-C1 distances (128.8(2) pm; double bond character).…”

“…7) is a distorted tetrahedron (S-Si-N: 107.58( 9)-115.78( 10 9)), N1-Si1-N3 109.39 (11) (108.73(11)), N1-Si1-N4 116.56 (10) (117.37(11)), N2-Si1-N3 109.04 (11) (110.11(11)), N2-Si1-N4 120.56 (11) (118.27(11)), N3-Si1-N4 120.35 (12) (121.17(12)), Si1-N4-Si2 147.06 (14) (152.59(15)), N1-C1-N2 106.0(2) (106.1( 2)). 2), N2-C1 128.9(2), N4-C40 124.9(4); S-Si-N1 107.58( 9), S-Si-N3 110.86( 9), S-Si-N4 115.78 (10), N1-Si-N3 110.12( 11), N1-Si-N4 108.19 (10), N3-Si-N4 104.23 (11), Si-N4-C40 124.2( 2), N1-C1-N2 115.82 (14). The structure of 11 is partially disordered; the data given refer to the dominating molecule with an occupation factor of 82.3%.…”

“…7 Molecular structure of 11 in the crystal ( probability level of displacement ellipsoids 50%; hydrogen atoms omitted for clarity). Selected bond lengths [ pm] and angles [°]: Si-S 216.10(19), Si-N1 176.1(2), Si-N3 170.2(2), Si-N4 173.5(2), N1-C1 139.6(2), N2-C1 128.9(2), N4-C40 124.9(4); S-Si-N1 107.58(9), S-Si-N3 110.86(9), S-Si-N4 115.78(10), N1-Si-N3 110.12(11), N1-Si-N4 108.19(10), N3-Si-N4 104.23(11), Si-N4-C40 124.2(2), N1-C1-N2 115.82(14). The structure of 11 is partially disordered; the data given refer to the dominating molecule with an occupation factor of 82.3%.…”

“…SivE (E = Se, Te) bond lengths[ pm] of compounds 8, 9 and 20-34 as determined by single-crystal X-ray diffractionCompounds 5, 7•C 6 H 5 CH 3 , 8-12, 14 and 15 were studied by NMR spectroscopy in the solid state ( 15 N, 29 Si, 77 Se, 125 Te; T = 22 °C) and in solution ( 1 H, 13 C, 29 Si, 77 Se, 125 Te; C 6 D 6 (5, 8-12 and 15), [D 8 ]THF (7•C 6 H 5 CH 3 ) or CD 2 Cl 2(14); T = 25 °C). In addition, compound 6 was characterised by NMR spectroscopic studies in the solid state ( 15 N, 29 Si; T = 22 °C) and in solution ( 29 Si; C 6 D 5 CD 3 ; T = 90 °C),10 and 7′ was characterised by NMR spectroscopy in solution ( 1 H,13 C, 29 Si; C 6 D 5 CD 3 , T = 75 °C; [D 8 ]THF, T = 25 °C).…”

Hydrosilylation in Aryliminopyrrolide‐Substituted Silanes

“…The first stable silylene was developed by using a chelating dianionic N‐donor substituent that forms a five‐membered ring with silicon(II), in an analogous fashion to Arduengo's N‐heterocyclic carbene . In recent years, stable silylenes have also been isolated with a range of monoanionic, bidentate N‐donor substituents such as (bis)amidinato, (bis)guanidinato, and β‐diketiminates . Furthermore, a free silicon(II) anion has recently been afforded by cleavage of one pyrazolyl from a tetrapyrazolyl silane, which has been coordinated to transition metals such as Pd, Pt, and Cu, demonstrating the use of electron‐withdrawing heterocyclic substituents to stabilize novel low‐valent silicon chemistry.…”