Steven J. Rettig

The reactivity of five-coordinate Ru(II) (1,4-bis(diphenylphosphino)butane) complexes with the N-donor ligands: ammonia, pyridine, 4-substituted pyridines, 2,2′-bipyridine, bis(o-pyridyl)amine, 1,10-phenanthroline, 4,7-diphenylphenanthroline and ethylenediamine

Abstract A series of Ru(II)(1,4-bis(diphenylphosphino)butane)(L)2 complexes was synthesized from [RuCl2(dppb) l2 (μ-dppb) or RuCl2 (dppb)- (PPh3); dppb = Ph2P(CH2)4PPH2, L = NH3, pyridine (py), 4-aminopyridine (4-NH2py), 4-cyanopyridine (4-CNpy), 4-dimethylaminopyridine (4-Me2Npy), 4-methylpyridine (4-Mepy), 4-phenylpyridine (4-Phpy), 4-vinylpyridine (4-Phy) and N-methylimidazole (Melm) and L2 = 2,2′-bipyridine (bipy), bis(o-pyridyl)amine (bpa), 1,10-phenanthroline (phen), 4,7-diphenylphenanthroline (or bathophenanthroline, batho) and ethylenediamine (en). The complexes were characterized by elemental analysis, cyclic voltametry, UV-Vis, NMR and IR spectroscopies. The structures of trans-RuCl2(dppb) (py)2 (3), cis-RuCl2(dppb)(bipy) (4) and cis-RuCl2(dppb) (phen) (5) were established by X-ray crystallographic analyses. Crystals of trans-3, cis-4-CH2Cl2 and cis-5-solvate are all monoclinic, space group P21/c, with Z=4; a = 12.946 (2), b = 14.204(3), c = 18.439(4) A , β = 90.08(2)° for trans-3; a=10.694(6), b=18.485(6), c=18.632(7) A , β = 90.26(3)° for cis-4·CH2Cl2; a = 17.094 (1), b = 9.923(2), c = 21.905(2) A , β = 98.883 (6)° for cis-5 solvate. The structures were solved by the heavy atom Patterson method and were refined by full-matrix least-squares procedures to R=0.069, 0.071 and 0.036 (Rw = 0.069, 0.076 and 0.039) for 1957, 4165 and 4824 reflections with l ≥ 3σ (l), respectively.

Crystal and molecular structure of phenylboronic acid, C6H5B(OH)2

Crystals of phenylboronic acid are orthorhombic, a = 17.9049(7), b = 115.3264(5), c = 9.8113(2) A, Z = 16, space group Iba2. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.031 and Rw of 0.041 for 1409 reflections with I ≥ 3σ(I). The asymmetric unit consists of two independent molecules linked by a pair of O—H … O hydrogen bonds. Each dimeric unit is also hydrogen bonded to four other such units (at ) to form an infinite array of layers which stack along the c axis. Mean bond lengths corrected for libration (rms deviations from the mean in parentheses) are: O—B, 1.371(7), B—C, 1.565(3), and C—C(phenyl), 1.394(11) A.

Activation of dihydrogen by ruthenium(II)-chelating phosphine complexes, and activation of dioxygen by ruthenium(II) porphyrin complexes: an update

Abstract This presentation reviews some recent studies from these laboratories that concern activation of dihydrogen and of dioxygen by various ruthenium complexes in solution. Part 1 describes developments in the catalytic chemistry of Ru(II)/chelating ditertiary phosphine complexes, in particular their applications in asymmetric hydrogenation, while Part 2 outlines work on O 2 -oxidation of thioethers catalyzed by Ru(II) porphyrin complexes. An experimental section, giving full details on the syntheses and characterization of the complexes, including X-ray crystallographic analyses, and on the catalysis experiments, is not given in this paper; such details will appear in future publications, but are meanwhile available on request.

Synthesis, characterization and reactivity of some mono- and dinuclear chlororuthenium complexes containing chelating ditertiary phosphines (PP) with PP:Ru=1

Mixed-valence complexes of the type (PP)ClRu(μ-Cl) 3 RuCl(PP), and the [RuCl(PP)] 2 (μ-Cl) 2 products formed by their reduction with H 2 , are synthesized, where PP is a chelating ditertiary phosphine Ph 2 P(CH 2 ) n PPh 2 (n=3–6) or some related chiral analogues such as diop, chiraphos, dppcp, dpcycp, bdpp, binap, phenop or norphos (diop=Ph 2 PCH 2 HCH 2 PPh 2 ; chiraphos=Ph 2 PCH(Me)CH(Me)PPh 2 ; dppcp=Ph 2 P HPPh 2 ; dpcycp=(C 6 H 11 ) 2 P HP(C 6 H 11 ) 2 ; bdpp(skewphos)=Ph 2 PCH(Me)CH 2 CH(Me)PPh 2 ; binap=2,2′-bis(diphenylphosphine)-1,1′-binaphthyl; phenop=Ph 2 PN(Et)CH(CH 2 Ph)CH 2 OPPh 2 ; norphos=Ph 2 P HPPh 2 ). The [RuCl(binap)] 2 (μ-Cl) 2 species is also formed in solution by dissociation of PPh 3 from RuCl 2 (binap)(PPh 3 ) which is synthesized by phosphine exchange with RuCl 2 (PPh 3 ) 3 . From the [RuCl(PP)] 2 (μ-Cl) 2 complex (PPPh 2 (CH 2 ) 4 PPh 2 ), a range of L(P-P)Ru(μ-Cl) 3 RuCl(PP) species is readily formed, where L includes an amine, acetone, N,N-dimethylacetamide, MeI, PhCN, CO, N 2 or H 2 ; the LNEt 3 adduct is made also from RuCl 2 (dppb)(PPh 3 ), while the corresponding dimethyl sulfoxide adduct (LDMSO), 17e , is synthesized directly from cis - RuCl 2 (DMSO) 4 and the phosphine. 31 P{ 1 H} NMR data are presented for the Ru(II) species, while characterization of 17e includes an X-ray crystallographic analysis that confirms the trichloro-bridged formulation. Crystal data are as follows: triclinic, P , a =12.796(1), b =14.559(1), c =18.429(1) A, a =103.983(5), β=99.634(6), γ=99.634(6)°, Z =2, R =0.037 and R w =0.046 for 9088 reflections with I ≥ 3σ( I )

Synthesis, structure and hydrogenation of η3-benzyl diphosphine complexes of rhodium and iridium

Abstract The preparation of (COD)Rh(η 3 -CH 2 Ph) is described starting from [(COD)Rh] 2 (μ-Cl) 2 by the addition of either Zn(CH 2 Ph) 2 or Mg(CH 2 Ph) 2 (THF) 2 . The addition of the bulky chelating diphosphines t Bu 2 P(CH 2 ) 3 P t Bu 2 , i Pr 2 P(CH 2 ) 3 P i Pr 2 , i Pr 2 P(CH 2 ) 2 -P i Pr 2 , i Pr 2 PCH 2 P i Pr 2 and Cy 2 PCH 2 PCy 2 to (COD)Rh(η 3 -CH 2 Ph) yields the coordinatively unsaturated, four-coordinate rhodium complexes of the form P 2 Rh(η 3 -CH 2 Ph). Iridium complexes of the form P 2 Ir(η 3 -CH 2 Ph) (where P 2  t Bu 2 P(CH 2 ) 3 P t Bu 2 and i Pr 2 P(CH 2 ) 3 P i Pr 2 ) can be prepared from [P 2 Ir] 2 (μ-Cl) 2 and Zn(CH 2 Ph) 2 or Mg(CH 2 Ph) 2 (THF) 2 . Reaction of the benzyl complexes with H 2 (1 atm) yields binuclear hydride derivatives of varying composition depending on the chelate ring size of the coordinated diphosphine. For the diphosphines with only a single methylene in the backbone, binuclear hexahydride complexes are formed in which the diphosphine is binucleating. The X-ray structure of { i Pr 2 P(CH 2 ) 3 P i Pr 2 }Rh(η 3 -CH 2 Ph) shows a square planar geometry about rhodium with alternating single and double bonds in the η 3 -coordinated benzyl fragment. Crystals of {1,3-bis(diisopropylphosphino)propane}rhodium(η 3 -benzyl)are monoclinic, a = 10.540(3), b = 15.030(9), c = 14.858(5) A, β = 92.91(3)°, Z = 4, D c = 1.329 g cm −3 , space group P 2 1 / n . The structure was solved by the Patterson method and was refined by full-matrix least-squares procedures to R = 0.036 and R w = 0.043 for 4152 reflections with I >- 3σ( I ).

Cationic ruthenium(II) complexes containing 1,4- bis(diphenylphosphino)butane and coordinated solvent molecules

Abstract Efforts to develop catalysts for asymmetric hydrogenation using ruthenium(II)- chelated ditertiary phosphine complexes have led to the synthesis of the complexes [{Ru(PP)(CH 3 CN)} 2 μ-Cl 3 ] + PF 6 − , [RuCl(PP)(CH 3 CN) 3 ] + PF 6 − , and [RuCl(η 6 - toluene)(PP)] + PF 6 − , where PP=1,4-bis(diphenylphosphino)butane. The characterization of the complexes, including X-ray data for the pseudo-tetrahedral toluene complex, is described. In preliminary tests, the tris(acetonitrile) complex has been shown to be a precursor for a catalyst that effects homogeneous hydrogenation of terminal olefins, CH,CN, and imines.

Organometallic nitrosyl chemistry. 18. Electrophile-induced reduction of coordinated nitrogen monoxide. Sequential conversion of a .mu.3-nitrosyl group to .mu.3-hydroxylimido and .mu.3-imido ligands by protonic acids

The principal impetus for the investigation of the reactivity of coordinated nitrogen monoxide derives from the widespread occurrence of nitrogen oxides as atmospheric pollutants. Initial studies in this regard were focused primarily on the behavior of nucleophiles or electrophiles toward linear or bent M-NO linkages, respectively. More recent research has begun to examine the analogous reactivity patterns of transition-metal complexes containing doubly bridging NO groups. However, maximum reduction of the N-O bond order (and hence optimum activation of the bond NO) should occur in M/sub 3/(..mu../sub 3/-NO) systems. Accordingly, we have investigated the reactions of one such system with strong protonic acids and now report unprecedented, sequential transformations where M = (n/sup 5/C/sub 5/H/sub 4/Me)Mn(NO) which involve an overall formal reduction of the ..mu../sub 3/-NO ligand.The principal impetus for the investigation of the reactivity of coordinated nitrogen monoxide derives from the widespread occurrence of nitrogen oxides as atmospheric pollutants. Initial studies in this regard were focused primarily on the behavior of nucleophiles or electrophiles toward linear or bent M-NO linkages, respectively. More recent research has begun to examine the analogous reactivity patterns of transition-metal complexes containing doubly bridging NO groups. However, maximum reduction of the N-O bond order (and hence optimum activation of the bond NO) should occur in M/sub 3/(..mu../sub 3/-NO) systems. Accordingly, we have investigated the reactions of one such system with strong protonic acids and now report unprecedented, sequential transformations where M = (n/sup 5/C/sub 5/H/sub 4/Me)Mn(NO) which involve an overall formal reduction of the ..mu../sub 3/-NO ligand.

Triply-bridged diruthenium(II) 1,4-bis(diphenylphosphino)butane (dppb) and (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (binap) complexes, including structural characterisation of [(dppb) ClRu(μ-D2O)-(μ-Cl)2RuCl(dppb)], [(η2-H2) (dppb)Ru(μ-Cl)3RuCl(dppb)] and the [(dppb)ClRu(μ-Cl)3RuCl(dppb)]− anion

Abstract Several triply-bridged diruthenium(II)(1,4-bis(diphenylphosphino)butane) complexes were synthesised and characterised by elemental analysis, UV-Vis, NMR and IR spectroscopies. The solid-state structures of [(dppb)ClRu(μ-D2O)(μ-Cl)2RuCl(dppb)] (1), [(η2-H2) (dppb)Ru(μ-Cl)3RuCl(dppb)] (2) and [Tmp][(dppb)ClRu(μ-Cl)3RuCl(dppb)] (3) were established by X-ray crystallographic analyses (TMP = 1,1,3-trimethyl-2,3-dihydroperimidinium; dppb = Ph2P(CH2)4PPh2). Crystals of 1·1.5C6D6, 2·1.5C7D8 and 3·2Me2CO·2H2O are all monoclinic, space groups P21/c, P21/n and C2/c, respectively, with Z = 4; a = 16.8681(6), b = 13.3542(4), c = 26.4966(7) A, β = 91.877(1)° for 1·1.5C6D6; a = 19.8123(1), b = 14.5246(2), c = 22.1803(1) A, β = 106.58(1)° for 2·1.5C7D8; a = 21.596(2), b = 16.019(2), c = 22.317(2) A, β= 106.15(1)° for 3·2Me2CO·2H2O. The structures of 1 and 2 were solved by direct methods while 3 was solved by heavy atom methods and all were refined by full-matrix least-squares procedures to R1 = 0.0433, 0.0612 and R = 0.039 (wR2 = 0.0709 (1), 0.1178 (2)) for 7751, 6757 and 5237 reflections with I ≥ 2σ(I) for 1 and 2 and I ≥ 3σ(I) for 3, respectively. Complex 1 was also studied in the solid-state by 31P CP/MAS NMR spectroscopy. The bromo- and iodo-analogues of 1 were prepared, and these three species were screened as catalysts for hydrogenation of aldimines. The complexes [H2NR2][{RuCl(P-P)}2(μ-Cl)3] were synthesised by the addition of NR3 or [H2NR2]Cl to RuCl2(P-P) (PPh3), where P-P = dppb or (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (binap) and R - Et, n-Bu or n-Oct. The syntheses of [(DMA)2H][(PPh3)2ClRu(μ-Cl)3RuCl(PPh3)2], [(py)(dppb)Ru(μ-Cl)3RuCl(dppb)] and [(C2H4) (dppb)Ru(μ-Cl)3RuCl(dppb)] were also accomplished (DMA = N,N-dimethylacetamide; py = pyridine).

RUTHENIUM COMPLEXES CONTAINING TERTIARY PHOSPHINES AND IMIDAZOLE OR 2,2'-BIPYRIDINE LIGANDS

Complexes RuCl3(PPh3)L2 (L = MeIm (1a, Im (1b)) and [RuCl2(PPh3)2(bipy)]Cl·4H2O (2) have been synthesized via the ruthenium(III) precursor RuCl3(PPh3)2 (DMA), and characterized, including an X-ray structural analysis for 1a (MeIm = N-methylimidazole, Im = imidazole, bipy = 2,2′-bipyridyl, and DMA = N, N′-dimethylacetamide). Crystals of 1a are monoclinic, space group P21/n, a = 10.5491(5), b = 20.4934(9), c = 12.8285(4) A, β = 90.166(4)°, Z = 4. The structure, which reveals a mer configuration for the chlorides, and cis-methylimidazoles, was solved by conventional heavy atom methods and was refined by full-matrix least-square procedures to R = 0.041 and Rw = 0.042 for 3328 reflections with I ⩾ 3σ(I). From the RuCl2(PPh3)3 precursor, the ruthenium(II) complexes RuCl2(PPh3)2L2 and [RuCl(PPh3)L4]Cl have been made (L = Im or MeIm), while [RuCl(dppb)Im3]Cl has been made from [RuCl2(dppb)]2(μ-dppb) (dppb = Ph2P(CH2)4PPh2).

Reaction of primary silanes with dinuclear rhodium hydride complexes: silane coupling reactions

Abstract The reaction of the dinuclear rhodium hydride dimer [(dippe)Rh]2(μ-H)2 (dippe=l,2-bis(diisopropylphosphino)ethane) with primary silanes is described. In the presence of two equivalents of RSiH3 (R=Bun and TolP), dinuclear bis(μ-silylene) complexes of the formula [(dippe)Rh]2(μ-SiHR)2 result. Attempts to generate silylhydride complexes of the formula [(dippe)Rh]2(μ-H)(μ-H-SiHR) by the addition of one equiv. of RSiH3 failed. The bis(μ-silylene) complexes react with hydrogen to form adducts wherein two equivalents of H2 per dimer unit have been activated; on the basis of NMR spectral studies these complexes are proposed to have the following formula: [(dippe)RhH]2(μ-H-SiHR)2. These molecules are extremely fluxional and lose H2 rather readily. Addition of more than three equivalents of primary silane to 1 generated dinuclear rhodium derivatives with three silicon-containing ligands, having the formula [(dippe)Rh]2(μ-SiHR)(μ-H-SiHR)2. In the presence of excess primary silane, the dinuclear rhodium hydride 1 acts as a catalyst precursor for the dehydrogenative coupling of silanes. With the p-tolylsilane, dimerization does occur but the process is complicated by dispro- portionation reactions to generate (TolP)2SiH2 and (TolP)3SiH; with butylsilane, SiSi chains with up to five silicons have been produced with no evidence of disproportionation. Crystals of [(dippe)Rh]2(μ-SiHBun)2 (2a) are monoclinic, a=10.889(1), b=13.105(2), c=16.676(2) A,β=104.06(1)°, Z=2, space group P21/n.; and those of [(dippe)Rh]2(μ-η2-H-SiHTolP)2(μ-SiHTolP) (4b) are monoctinic, a=25.839(4), b=13.084(3), c=17.133(3) A, β=107.10(1)°, Z=4, space group P21/a. The structures were solved by Patterson (2a) and direct (4b) methods and were refined by full-matrix least-squares procedures to R=0.035 and 0.047 (Rw=0.030 and 0.060) for 3184 and 5997 reflections with 1⩾3η(I), respectively.