Synthesis and Study of Ruthenium Silylene Complexes of the Type [(η⁵-C₅Me₅)(Me₃P)₂RuSiX₂]⁺(X = Thiolate, Me, and Ph)

Abstract

Various ruthenium silyl complexes of the type Cp*(Me3P)2RuSiR3 (Cp* = η5-C5Me5; SiR3 = SiCl3 (1), Si(NMe2)3 (2), Si(SEt)3 (3), Si(S-2-Naph)3 (4), (5), Si(SCy)2Cl (6), and Si(SMes)2Cl (7, Mes = 2,4,6-trimethylphenyl)) were prepared by the reaction of Cp*(Me3P)2RuCH2SiMe3 with the appropriate silane HSiR3. Compound 3 was converted to the triflate Cp*(Me3P)2RuSi(SEt)2OTf (8) by the reaction of 3 with Me3SiOTf. Similar reactions produced Cp*(Me3P)2RuSi(NMe2)2OTf (13), Cp*(Me3P)2RuSi(NMe2)(OTf)2 (14), Cp*(Me3P)2RuSi(SMes)2OTf (18), and Cp*(Me3P)2RuSi(SMes)(Cl)OTf (19). By NMR spectroscopy, compound 8 in dichloromethane solution appears to possess a labile triflate group. Reactions of the triflates 8 and Cp*(Me3P)2RuSi(S-p-Tol)2OTf (10) with NaBPh4 provided the silylene complexes [Cp*(Me3P)2RuSi(SR)2][BPh4] (20, R = Et; 21, R = p-Tol). Similarly, the reaction of 6 with NaBPh4 gave [Cp*(Me3P)2RuSi(SCy)2][BPh4] (22), and the reaction of 4 with B(C6F5)3 produced [Cp*(Me3P)2RuSi(S-2-Naph)2][MeB(C6F5)3] (23). Silylene complexes 20−23 display characteristic 29Si NMR shifts in the region of δ 250−270. The non-heteroatom-stabilized silylene complexes [Cp*(Me3P)2RuSiR2][B(C6F5)4] (24, R = Me; 25, R = Ph), obtained via reactions of (Et2O)LiB(C6F5)4 with Cp*(Me3P)2RuSiR2OTf (11, R = Me; 12, R = Ph) exhibit 29Si NMR shifts around δ 300. The crystal structure of 24 revealed a Ru−Si distance of 2.238(2) Å, and the Cp*(centroid)−Ru−Si−Me dihedral angle is 34°. Compound 24 reacts quantitatively with 1 equiv of PMe3 or PPh3 in dichloromethane-d 2 to form the base-stabilized silylene complexes [Cp*(Me3P)2RuSiMe2(PR3)][B(C6F5)4] (28, R = Me; 29, R = Ph), identified by 1H and 31P NMR spectroscopy. These complexes are thermally labile and decompose with elimination of the dimethylsilylene fragment to give [Cp*(Me3P)2RuPR3][B(C6F5)4] (R = Me, Ph). The ylide CH2PPh3 reacts with 24 to form [Cp*(Me3P)2RuSiMe2CH2PPh3][B(C6F5)4] (32a), and the characterization of [Cp*(Me3P)2RuSiMe2CH2PPh3][OTf] (32b) by X-ray crystallography suggests that the complex is best viewed as a ruthenium silyl derivative with the positive charge localized on the “ylide” phosphorus atom. Reactions of 20 and 24 with hydrogen proceed slowly and result in relatively complex product mixtures that contain various ruthenium hydride species. The reaction involving 20 also produced HSi(SEt)3, perhaps via redistribution of initially formed H2Si(SEt)2. For the reaction of 24 with hydrogen, no H2SiMe2 was detected in the product mixture. The reaction of 20 with H3SiSiPh3 gave [Cp*(Me3P)2Ru(H)(SiH2SiPh3)][BPh4] (35) and HSi(SEt)3, and the corresponding reaction of H3SiMes in dichloromethane gave [Cp*(Me3P)2RuHCl][BPh4] (34), BPh3, and H2SiMes(SEt), among other products. By NMR spectroscopy, the intermediate [Cp*(Me3P)2Ru(H)(SiH2Mes)][BPh4] (36) was observed for the latter process. Compound 36, generated independently by reaction of [Cp*(Me3P)2Ru(NCMe)][BPh4] with H3SiMes, was shown to react with HSi(SEt)3 to give H2SiMes(SEt).

Stable Systems with a Triple Bond to Silicon or Its Homologues: Another Challenge

“…Cationic silylene complexes of the type [L n MSiR 2 ] can be prepared by removing an anionic substituent X À from the corresponding silyl complex [L n MSiR 2 X]. [12] Variation of substituents at the Group 14 element as well as variations of the metal unit meanwhile have led to a huge number of stable complexes with ligands which are analogous to carbenes. [13] As for the Fischer carbene complexes, the Dewar ± Chatt ± Duncanson model can be applied to explain the bonding (Scheme 3).…”

Silver‐Catalyzed Silylene Transfer

“…32 Late transition metal silylenoid complexes were first synthesized by exploiting the lability of silicon-triflate bonds (Scheme 7.2). [34][35][36][37] Tilley and coworkers reported that ruthenium silylenoid could be accessed in two steps from the silyl ruthenium cyclopentadienyl complex 8. Ethyl thiolate abstraction by trimethylsilyl triflate generated 9, which formed the silylenoid complex (10) on exposure to sodium tetraphenylborate.…”

MOLECULAR STRUCTURE OF ORGANOSILICON COMPOUNDS WITH Si - Ru, Si - Rh and Si - Pd BONDS

“…?7 5 -Cyclopentadienyl (Cp) and rj 5 -pentamethylcyclopentadienyl (Cp*) derivatives 1 [3][4][5][6][7] as well as rj 6 -arene complexes 2-4 [8][9][10] adopt a three-legged piano stool geometry around ruthenium with legs composed of silyl and carbonyl or trimethylphosphine groups. The Ru -Si bond distance in trichlorosilyl complex 1 (Cp, L=Me 3 P) of 2.265 A, is consistent with a single bond.…”

“…In spite of the fact, that the most direct probe of Ru -Si multiple bond character is the Ru -Si bond length, often the Μ -Si single-bond distances for transition metal silyl complexes are shorter than expected on the basis of covalent radii. The molecular structure of the cation in complex 44 [7] consists of a dimethylsilylene ligand that is planar at silicon and coordinated to Cp*(Me 3 P) 2 Ru fragment. The Ru = Si distance of 2.238 A is shorter than in other silylene complexes, however, it is longer as compared with compound 28 containing Ru -Si bond bridged by two hydrogen atoms.…”