Cleavage of phosphorus–phenyl and phosphorus-2-pyridyl bonds in the reactions of mixed phenyl-(2-pyridyl) phosphines with [Ru₃(CO)₁₂]

Abstract

The compound [Ru,(CO),,] reacts at room temperature in tetrahydrofuran with tri(2-pyridyl)phosphine, P(2-C,H,N),, when catalysed by [N(PPh,),]CI, to give a product derived by cleavage of a phosphorus-2-pyridyl bond, [Ru,(p-2-C,H,N){p3-P(2-C5H,N),}(CO),] 1. No simple substitution compounds could be isolated. The likely intermediates [Ru,(CO),{P(~-C,H,N)~}] ( n = 10 and/or 11 ) spontaneously decarbonylate while a 2-pyridyl group migrates from phosphorus to ruthenium atoms. A similar reaction using phenyldi(2-pyridy1)phosphine. PPh(2-CSH4N),, leads to the competitive transfer of 2-pyridyl and phenyl groups to give almost equal quantities of two products, [Ru3(p-2-C,H,N){b-PPh(2-C,H,N)}-(CO),] and [Ru3(p-PhCO){~-P(2-C5H4N)30,1. The crystal structure of 1 shows that the 2-pyridyl group that has migrated bridges two ruthenium atoms with no Ru-Ru bond between them and that the di(2-pyridy1)phosphido ligand is triply bridging with one nitrogen co-ordinated and one free. As in the reported reaction of [RuJCO),,] with PPh2(2-C,H,N) to give [Ru3(p-PhCO){~-PPh(2-C,H,N)}( CO),], the reason why P-C bond cleavage occurs under remarkably mild conditions and the mechanism of the processes have still to be determined.

Reactions of diphenylpyridylphosphine with H2Os3(CO)10 and H4Ru4(CO)12, P–C bond splitting in the coordinated ligand and isolation of the oxidative addition products

“…The low field part of the spectrum consists of four multiplets (8.86 ppm, d, J = 5.5 Hz, H 6 ; 7.64 ppm, dd, J = 5.7, 3.6 Hz, H 4 ; 7.03 ppm, ddd J = 5.7, 5.5, 1.2 Hz, H 5 ; 6.47 ppm, dd, J = 3.6, 7.5 Hz, H 3 ) corresponding to the pyridyl protons and of the complex phenyl multiplet (10 H) centred at 7.4 ppm. The position and multiplicity of the pyridyl proton signals are in excellent agreement with the data obtained earlier for Ru 3 and Os 3 pyridyl-phosphide clusters [10,14]. The proton and phosphorus NMR data obtained for 1 indicate that the structure found in the solid state remains unchanged in solution.…”

“…In line with the chemistry described above and other examples of pyridylphosphines reactions with the nonhydride Ru 3 [12][13][14] and Os 3 [10] clusters we found that coordinated Ph 2 P(2-C 5 H 4 N) easily breaks a P-C bond to afford the phosphide H 3 Ru 4 (CO) 10 (l 3 ,j 2 -PhP(2-C 5 H 4 N)) cluster (4). The stoichiometry of 4 clearly indicates that this is a product of reductive elimination of benzene from 3, which occurs under very mild conditions compared to the 1 !…”

“…This situation looks very similar to immediate elimination of benzene or benzaldehyde from the nonhydride Ru 3 (l-C(O)Ph)(l 3 ,j 2 -PhP-(2-C 5 H 4 N))(CO) 9 [15] upon their treatment with H 2 , [BH 4 ] À or HPPh 2 . Formation of this intermediate containing oxidatively added phenyl moiety is well supported by the results obtained for analogous reactions of the nonhydride Ru 3 clusters [12][13][14][15]. It is worth noting that the reaction with [BH 4 ] À occurs at room temperature with immediate release of benzaldehyde.…”

“…Reactions of pyridylphosphines with ruthenium, rhodium and osmium clusters were studied in detail because of the versatile coordination chemistry of these ligands on the polymetal centers [1][2][3][4][5][6][7][8][9][10][11], which includes oxidative P-C bond cleavage to give the face-bridging pyridylphosphide and formation of either r-phenyl or bridging pyridyl or benzoyl moieties derived from the starting phosphine [10,[12][13][14]. It is well known that r-bonded (M-C) organic ligands can be easily removed from coordination sphere of transition metal complexes by reductive coupling with adjacent cis-hydride.…”

Chiral hexarhodium carbonyl clusters containing heterobidentate phosphine ligands; a structural and reactivity study

“…The chemistry of transition metal complexes containing X-functionalised P-donor ligands (PX), where X is a two electron donor containing sulfur, nitrogen or oxygen atoms, or a C᎐ ᎐ C double bond, has been investigated quite intensively for both mononuclear, 2-6 and cluster compounds. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] From the viewpoint of structural chemistry, coordination of these potentially heterobidentate ligands to a cluster core can occur in various ways: chelating, bridging or in a simple κ 1 mode, usually through the phosphorus atom. Each of these is governed by particular properties of the ligand and metal centre or centres, as well as by particular mechanistic features of the ligand coordination process.…”