Catalytic Dehydrogenative Coupling of Stannanes by Alkoxysilyl Heterobimetallic Complexes:  Influence of the Assembling Ligand † (original) (raw)

Reactivity of Heterobimetallic Alkoxysilyl and Siloxy Complexes in the Catalytic Dehydrogenative Coupling of Tin Hydrides

Organometallics, 1998

Heterobimetallic complexes [(OC) 3 (R 3 Si)Fe(µ-dppm)Pd(η 3 -allyl)] 1 (R ) OMe, Me, OSiMe 3 , OSi(H)Me 2 ) and [(OC) 3 Fe{µ-Si(OR) 2 (OR)}(µ-dppm)PdCl] 6 (R ) Me, SiMe 3 ) are effective catalyst in the dehydrogenative coupling of triorganotin hydrides HSnR′ 3 (R′ ) Ph, n Bu). Although the elementary transformations during catalysis appear to take place at palladium, the function of the iron fragment is to provide the palladium center with the appropriate coordination environment through metal-metal bonding and the Si-containing ligand. Indeed, complexes 1 and 6 revealed a higher catalytic activity than mononuclear Pd catalysts. Modifications of the substituents at silicon resulted in considerable variations of the TON (turnover number) and TOF (turnover frequency) values as well as in the lifetime of the catalysts. In the case of siloxy derivatives, TON and TOF values higher than in the case of the alkoxysilyl analogs have been obtained whereas the lifetime of the catalyst is much longer for the latter. Possible mechanisms which rationalize the role of the silicon ligand are discussed. Solvent effects have also been observed. One of the key features of these systems is the retention of the bimetallic nature of the catalyst. TON and TOF higher than 2 × 10 5 and 3 × 10 7 h -1 , respectively, have been obtained in the case of HSn n Bu 3 . The catalytic activity of 1 toward the dehydropolymerization of tin dihydrides has been tested.

Heterobimetallic alkoxysilyl cationic complexes: investigations into the displacement of a μ-η2-Si,O bridge by functional phosphine ligands

Journal of the Chemical Society, Dalton Transactions, 1999

The lability of the SiO→M interaction unique to some bimetallic complexes may confer hemilabile properties to the Si(OR) 3 ligand and various bifunctional phosphines P-Z have been used in order to evaluate the possible competition for co-ordination between the bridging SiO→M interaction and P-Z chelation. Thus, treatment of the heterobimetallic complexes [(OC) 3 Fe{µ-Si(OMe) 2 (OMe)}(µ-dppm)MCl] (M = Pd 4 or Pt 6; dppm = Ph 2 PCH 2 PPh 2 ) and [(OC) 3 Fe{µ-Si(OMe) 2 (OMe)}(µ-dppa)PdCl] 5 (dppa = Ph 2 PNHPPh 2 ) with TlPF 6 in the presence of P-Z afforded the corresponding cationic compounds

Synthesis and reactivity of bimetallic alkoxysilyl complexes. Crystal structure of [cyclic][Fe(CO)3{.mu.-Si(OMe)2(OMe)}(.mu.-dppm)Rh(CO)] (dppm = Ph2PCH2PPh2): a complex with a .mu.2-.eta.2-SiO bridge between iron and rhodium

Organometallics, 1991

Bimetallic F e R h complexes have been prepared from the (alkoxysily1)iron derivatives [HFe(CO),{Si-(OMe),)(dppm-P)] or [HFe(C0)3(Si(OMe)3J(dppm-P)]-, the dppm ligand of which helps assembling and stabilizing the dinuclear unit. The crystal structure of [Fe(CO)3{p-Si(OMe)2(OMe)l(p-dppm)Rh(CO)] (la) has been determined: monoclinic, space group P2,/n, a = 22.717 (5) A, b = 11.348 (2) A, c = 14.202 (2) A, p = 94.47 (2)O, V = 3650.2 A,, Z = 4, R = 0.033, R, = 0.052 for 4531 reflections with I > 3u(n. Complex la contains an unusual p2-q2-Si0 bridge between the Fe and Rh atoms (Fe-Rh = 2.6283 (7), Rh-07 = 2.167 (3), 07-Si = 1.683 (31, Si-Fe = 2.249 (1) A). Complex [Fe(CO)3(p-Si(OMe)2(OMe)l(Cc-dppm)Rh(PPh3)] (2) reacts with P(OPh), to give [Fe(C0)3{p-Si(OMe)2(OMe)J(p-dppm)Rh(P(OPh)3)] (3). Complex la reacts reversibly with CO with opening of the p2-v2-SiO bridge to give [Fe(CO),{Si(OMe),l(p-dppm)Rh(CO),] (4). Protonation of the Fe-Rh bond of la with HBF, yields [Fe(CO)2(p-Si(OMe2(OMe)](p-dppm)(p-H)(p-CO)Rh(PPh,)] [BF,] (51, which is isoelectronic with [Fe(CO)2{p-Si(OMe)2(0Me)l(p-dppm)(p-H)(p-CO)-RhCl] (6a), prepared by the addition of [HFe(CO),(Si(OMe),)(dppm-P)] to a suspension of [Rh,(p-Cl),-, i A L 1 (COD),] in EhO. Reaction of K[Fe(CO),(Si(OMe),)(dppm-P)] with [RhCl(CS)(PPh,),] afforded [Fe-(CO),(Si(OMe),l(p-dppm)Rh(CS)(PPh,)] (8). The stronger Rh-CS interaction compared with the Rh-CO

Synthesis, reactivity, molecular structure, and catalytic activity of the novel dichlorodihydridoosmium(IV) complexes OsH2Cl2(PR3)2 (PR3 = P-i-Pr3, PMe-t-Bu2)

Inorganic Chemistry, 1991

The six-coordinate diamagnetic osmium(1V) complexes O S H~C I~( P R~)~ [PR, = P-i-Pr, (Z), PMe-?-Bu2 (3)] are prepared from OsC1,.xH20 and PR, in boiling 2-propanol in ca. 80% yield. Treatment of 3 with CO leads to reductive elimination of H2 and formation of aIl,rran.~-OsC1~(CO)~(PMe-f-B~~)~ (4). Likewise, 3 reacts with excess PMe, to give ci~-OsCl~(PMe~)~ (5). The crystal and molecular structure of 2 has been determined. Crystal data for 2: monoclinic, P2,/c, 4 = 12.2791 (6) A, b = 8.5700 (3) A, c = 23.5061 (9) A, fi = 103.526 (4)O, Z = 4, R = 0.022, R, = 0.024 based on 3705 observed unique reflections. The coordination polyhedron around the six-coordinate osmium atom is described as a somewhat distorted variant of the Du square antiprism with two vacant coordination sites in alternate positions at one square base of this polyhedron. The reaction of 4 with LiAIH, in THF leads to the formation of all,tr~ns-OsH~(CO)~(PMe-i-B~~)~ (6), whereas treatment of 2 and 3 with NaBH, in

Facile substitution of triphenylphosphine in Wilkinson's catalyst by Sn(N-tert-Bu)2SiMe2. Syntheses and molecular structures of square-planar and homoleptic trigonal-bipyramidal stannylene complexes of rhodium(I)

Inorganic Chemistry, 1989

1.0 x 105 0.293 (NH3)sRu11'(BPA)Fe1i(CN)s 368 4.3 4.3 x 102 (NH3)sRu11(BPA)Fe11(CN)5-408, 368d 8.7, 5.7 5.0 x 104' (NH3)5C011'(BPA)Fe1'(CN)s 365b 4.5 (NH3)5Ru11i(BPA)Fe11'(CN)5+ 415, 365 1.4, 1.3 0.447/0.29W (NH3)sRh11'(BPA)Fe11(CN)5 367 3.3 0.50 0.440 (NH3)sRu11(BPA)Co'11(CN)5h 403 OAt 25 O C , I = 0.10 M (NaCI), pH = 5.5 (H2EDTA2-/CH3C02-). *Reference 6. CIn 0.10 M HCI. dShoulder. 'Oxidation of Ru". /Reduction site which is oxidized more readily, could have important implications in biological electron-transport chains. of 2 to 1. #Reduction of 1 to 3. X 10" M were obtained by reduction of 1 with ascorbic acidlo or via eq 4 by mixing equimolar solutions of R U " (N H~)~B P A~+ In KBr pellet; solution studies precluded by insolubility of complex. Ru1*(NH3),BPAZ-+ Fe11(CN)50H23-* 3 k4, k, (4) (prepared by reduction of Ru"'(NH3),BPA3+ with ascorbic acid or with zinc amalgam) and Fe"(CN),OHZ3-. Solutions of 3 display the MLCT bands of both Ru(I1) and Fe(I1) centers (Table

Ditantalum Hydride Complexes with Bridging (2,6- i Pr 2 C 6 H 3 )NSiHPh Silanimine Ligands Resulting from PhSiH 3 −Imido Ligand Coupling. A Combined Spectroscopic and Theoretical Investigation

Organometallics, 2000

The preparation and characterization of two novel dinuclear tantalum hydride complexes featuring bridging silanimine ligands are reported. The reaction of Cp*(ArNd)Ta-[Si(SiMe 3) 3 ]H (Cp*) η 5-C 5 Me 5 ; Ar) 2,6-i Pr 2 C 6 H 3) with PhSiH 3 resulted in formation of [Cp*(ArNd)TaH(µ-H)] 2 (4% yield), yellow, paramagnetic Cp* 2 (ArNd)Ta 2 H 2 (µ-ArNSiHPh) (1, 18% yield), and dark green, diamagnetic Cp* 2 Ta 2 H 2 (µ-ArNSiHPh) 2 (2, 71% yield). For 1 and 2, X-ray structure determinations characterize the ArNSiHPh silanimine ligand as possessing a SiN single bond. This is confirmed by molecular orbital calculations that provide an average bond order of 0.7 for the SiN bond. The ArNSiHPh fragment is therefore best viewed as a bifunctional silyl-amido ligand. For diamagnetic complex 2, the X-ray analysis revealed a molecular structure possessing nearly exact 2-fold symmetry (the hydride ligands were not located), while NMR spectroscopy indicates that the two Cp*Ta(µ-ArNSiHPh) fragments in the molecule are chemically inequivalent. To analyze the structure and bonding in this compound, a theoretical study based on density functional theory and ab initio molecular dynamics was carried out. Calculations of the entire 140-atom dinuclear tantalum system confirm a structure with an asymmetric substitution of the two hydride ligands, with one terminal and one bridging. The paramagnetic compound 1 exhibits structural features that are similar to those for 2. For this complex, the spectroscopic data and density functional calculations are consistent with a structure featuring terminal and bridging hydride ligands. Scheme 1

Synthesis of dppm-stabilized Si?Fe?M (M = Zn, Cd, Hg or Tl) complexes and crystal structure of a heterotetranuclear Fe2Cd2 complex (dppm = Ph2PCH2PPh2)

Journal of the Chemical Society, Dalton Transactions, 1992

(dppm = Ph,PCH,PPh,) with CdX, (X = CI or Br) in tetrahydrofuran (thf ) in a 1 : 1 ratio afforded the tetranuclear iron-cadmium complexes mer- [{[(MeO),Si](OC),Fe(p-dppm)Cd(p-X) },] 2a (X = CI) and 2b (X = Br) in 78 and 65% isolated yield, respectively. Each Fe-Cd bond is supported by a dppm ligand. The reaction of the ketophosphinesubstituted metalate K[Fe(CO),{Si(OMe),}{Ph,PCH,C(O) Ph}] with CdCI, in a 1 : 1 ratio similarly afforded mer-[{ [(MeO),Si] (OC),Fe[p-Ph,PCH,C(O)Ph]Cd(p-Cl)},] 2c, in which a bridging mode for the functional (P,O) ligand is assumed for the first time. Reaction of K[Fe(CO),{Si(OMe),}(dppm-P ) ] with ZnCI, afforded the Fe-Zn analogue 3, which is very labile. Similarly, Fe-Hg complexes of the type mer-[{(MeO),Si}(OC),Fe(p-dppm)HgX] (R = Et, X = Ph; R = Me, X = C,CI, or CI) were prepared. The chloride bridges of 2a are easily split by nucleophiles. Using Ph,PCH,C(O)Ph, mer-[{(MeO),Si}(OC),Fe(p-dppm)CdCI{Ph,PCH,C(O)Ph}] and mer-[{( MeO),Si}(OC),Fe(p-dppm)HgCI-{Ph,PCH,C(O) Ph}] were obtained. They reacted with TI[PF,] to yield cationic complexes in which the ketophosphine acts as a chelating ligand. The synthesis of the Fe-TI"' complex mer-[{(MeO),Si}(OC),Fe(p-dppm)TI(C,F,),]