Hydrolysis of organonitriles and carboxamides in platinum(IV) complexes. X-ray structure determination of the crystalline clathrate {(C2H5)}4N [Pt(NH3)Cl5]· NH4Cl
“…The two iminoacyl ligands in both 1 and 3 are in a trans configuration which is the thermodynamically stable form for metals in high oxidation state . The values of the Pt−Cl bond distances (2.31−2.32 Å) agree well with previously characterized platinum(IV) chloride compounds .…”
Section: Resultssupporting
confidence: 87%
“…Recently two of us found that the addition of NH 3 to coordinated nitriles in [PtCl n (MeCN) 2 ] ( n = 2, 4) proceeds 10 times faster in the platinum(IV) compound as compared to the appropriate platinum(II) complex . Moreover, electrophilic activation of acetonitrile by platinum(IV) ion is such that this ligand is subject to facile two-step hydrolysis leading to [Pt IV ]−NH 3 complexes and MeCO 2 H . These experimental observations stimulated our current studies on the addition of oximes to platinum(IV)-bound nitriles.…”
Section: Resultsmentioning
confidence: 88%
“…In addition, the complexes remain intact in acetone- d 6 and methanol- d 4 containing 5% deuterium oxide for 1 week at room temperature and only then slowly start to decompose giving acetic acid and 2-propanone oxime among other unidentified hydrolysis products. In our opinion, such a resistance of the platinum(IV) complexes trans -[PtCl 4 (NHC(R)ONCR 1 R 2 ) 2 ] to hydrolysis is surprising from at least three viewpoints: (i) Quadruple charged platinum(IV) ion provides electrophilic activation of the nitrile carbon expressed in its enhanced reactivity toward nucleophiles in general and toward water−hydroxide in particular. ,, It would be perhaps reasonable to assume a similar high susceptibility of (imine)platinum(IV) species in the hydrolysis. Indeed, imines as, for example, N(Ph)CHR are subject to fast hydrolysis that occurs even in platinum(II) complexes in mild reaction conditions .…”
The metal-mediated iminoacylation reaction of ketoximes or aldoximes upon treatment with the organonitrile platinum(IV) complexes trans-[PtCl(4)(RCN)(2)] proceeds under relatively mild conditions in acetonitrile (R = Me) or in chloroform (R = CH(2)Ph, Ph) to give trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] (R(1) = R(2) = Me; R(1)R(2) = C(4)H(8), R(1)R(2) = C(5)H(10), R(1)R(2) = (H)Ph, R(1)R(2) = (H)C(6)H(4)(OH)-o; 1-14) in 90-95% yield. All these compounds were characterized by elemental analyses (C, H, N, Cl, Pt), FAB mass spectrometry, and IR and (1)H, (13)C{(1)H}, and (195)Pt NMR spectroscopies. X-ray structure determinations of [PtCl(4)(NH=C(Me)ON=CMe(2))(2)] (1) and [PtCl(4){NH=C(Me)ON=C(C(5)H(10))}(2)] (3) disclosed their overall trans-configuration and the amidine one-end rather than N,N-bidentate coordination mode of the N-donor ligands. The iminoacyl species are in E-conformation which is held by a rather weak N-H.N hydrogen bond between the amidine =NH atom and the oxime nitrogen with the following observed distances and angles for 1 and [3]: N(1).N(2), and N(1)-H, N(1)H.N(2) are 2.605 [2.592], 0.74 [0.71], and 2.20 [2.25] Å; N(1)-H.N(2) is 115 degrees [111 degrees ]. No evidence of the Z-conformation in solution was obtained by NMR spectroscopy. Compounds trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] are unexpectedly stable toward hydrolysis both in the solid state and in solutions.
“…The two iminoacyl ligands in both 1 and 3 are in a trans configuration which is the thermodynamically stable form for metals in high oxidation state . The values of the Pt−Cl bond distances (2.31−2.32 Å) agree well with previously characterized platinum(IV) chloride compounds .…”
Section: Resultssupporting
confidence: 87%
“…Recently two of us found that the addition of NH 3 to coordinated nitriles in [PtCl n (MeCN) 2 ] ( n = 2, 4) proceeds 10 times faster in the platinum(IV) compound as compared to the appropriate platinum(II) complex . Moreover, electrophilic activation of acetonitrile by platinum(IV) ion is such that this ligand is subject to facile two-step hydrolysis leading to [Pt IV ]−NH 3 complexes and MeCO 2 H . These experimental observations stimulated our current studies on the addition of oximes to platinum(IV)-bound nitriles.…”
Section: Resultsmentioning
confidence: 88%
“…In addition, the complexes remain intact in acetone- d 6 and methanol- d 4 containing 5% deuterium oxide for 1 week at room temperature and only then slowly start to decompose giving acetic acid and 2-propanone oxime among other unidentified hydrolysis products. In our opinion, such a resistance of the platinum(IV) complexes trans -[PtCl 4 (NHC(R)ONCR 1 R 2 ) 2 ] to hydrolysis is surprising from at least three viewpoints: (i) Quadruple charged platinum(IV) ion provides electrophilic activation of the nitrile carbon expressed in its enhanced reactivity toward nucleophiles in general and toward water−hydroxide in particular. ,, It would be perhaps reasonable to assume a similar high susceptibility of (imine)platinum(IV) species in the hydrolysis. Indeed, imines as, for example, N(Ph)CHR are subject to fast hydrolysis that occurs even in platinum(II) complexes in mild reaction conditions .…”
The metal-mediated iminoacylation reaction of ketoximes or aldoximes upon treatment with the organonitrile platinum(IV) complexes trans-[PtCl(4)(RCN)(2)] proceeds under relatively mild conditions in acetonitrile (R = Me) or in chloroform (R = CH(2)Ph, Ph) to give trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] (R(1) = R(2) = Me; R(1)R(2) = C(4)H(8), R(1)R(2) = C(5)H(10), R(1)R(2) = (H)Ph, R(1)R(2) = (H)C(6)H(4)(OH)-o; 1-14) in 90-95% yield. All these compounds were characterized by elemental analyses (C, H, N, Cl, Pt), FAB mass spectrometry, and IR and (1)H, (13)C{(1)H}, and (195)Pt NMR spectroscopies. X-ray structure determinations of [PtCl(4)(NH=C(Me)ON=CMe(2))(2)] (1) and [PtCl(4){NH=C(Me)ON=C(C(5)H(10))}(2)] (3) disclosed their overall trans-configuration and the amidine one-end rather than N,N-bidentate coordination mode of the N-donor ligands. The iminoacyl species are in E-conformation which is held by a rather weak N-H.N hydrogen bond between the amidine =NH atom and the oxime nitrogen with the following observed distances and angles for 1 and [3]: N(1).N(2), and N(1)-H, N(1)H.N(2) are 2.605 [2.592], 0.74 [0.71], and 2.20 [2.25] Å; N(1)-H.N(2) is 115 degrees [111 degrees ]. No evidence of the Z-conformation in solution was obtained by NMR spectroscopy. Compounds trans-[PtCl(4)(NH=C(R)ON=CR(1)R(2))(2)] are unexpectedly stable toward hydrolysis both in the solid state and in solutions.
“…The Pt atom in each case lies at an inversion center, and the two Cl atoms are mutually trans . The values of the Pt−Cl bond distances (2.312(1) for 1 and 2.319(1) Å for 2 ) agree well with previously characterized platinum(IV) chloride compounds . Two chelate ligands are trans , and the cycles containing the Pt atom are in an envelope-like conformation.…”
The platinum(II) complexes trans-[PtCl(2)(RR'C=NOH)(2)], where R = R' = Me, RR' = (CH(2))(4) and (CH(2))(5), react with m-chloroperoxybenzoic acid in Me(2)CO to give the platinum(IV) complexes [PtCl(2)(OCMe(2)ON=CRR')(2)] in 50-60% yields. The complexes [PtCl(2)(OCMe(2)ON=CRR')(2)] were characterized by elemental analysis, EI-MS, and IR and Raman spectroscopies; X-ray structure analyses were performed for both trans-[PtCl(2)(OCMe(2)ON=CC(4)H(8))(2)] and trans-[PtCl(2)(OCMe(2)ON=CC(5)H(10))(2)]. The former compound crystallizes in the triclinic space group P&onemacr; with a = 8.088(2) Å, b = 8.327(2) Å, c = 8.475(2) Å, alpha = 103.54(3) degrees, beta = 102.15(3) degrees, gamma = 108.37(3) degrees, V = 501.0(2) Å(3), Z = 1, and rho(calcd) = 1.917 g cm(-)(3). The latter complex crystallizes in the monoclinic space group C2/c with a = 12.5260(10) Å, b = 9.3360(10) Å, c = 18.699(2) Å, beta = 98.320(10) degrees, V = 2163.7(4) Å(3), Z = 4, and rho(calcd) = 1.862 g cm(-)(3). The structures of [PtCl(2)(OCMe(2)ON=CC(4)H(8))(2)] and [PtCl(2)(OCMe(2)ON=CC(5)H(10))(2)] show an octahedron of Pt where two Cl atoms and two chelate ligands are mutually trans, respectively.
“…All of the group 5 metal derivatives can be seen to have negative values of ∑α (as defined), consistent with the bending of these groups toward the donor ligand. We have also evaluated this parameter for all of the species [MCl 5 (L)] n - contained in the Cambridge Crystallographic Database (Table ). − A definite trend is evident, with the value of ∑α becoming less negative as the number of electrons in the formally nonbonding orbitals (t 2g in O h symmetry) increases. 6 Optimized structure (DFT/B3LYP) in C s symmetry for [Ta(OH) 2 (H) 2 (PH 3 )(Cl)].…”
The mixed chloro-aryloxide compounds [M(OC(6)H(3)Pr(i)(2)-2,6)(2)Cl(3)](2) (M = Nb (1a), Ta (1b); both structurally characterized) and [M(OC(6)H(3)Pr(i)(2)-2,6)(3)Cl(2)] (M = Nb (2a), Ta (2b)) react with pyridine (py) and PMe(2)Ph to produce a series of adducts cis-mer-[MCl(3)(OC(6)H(3)Pr(i)(2)-2,6)(2)(L)] (M, L: Nb, py (3a); Ta, py (3b); Nb, PMe(2)Ph (4a); Ta, PMe(2)Ph (4b)) and trans-mer-[MCl(2)(OC(6)H(3)Pr(i)(2)-2,6)(3)(L)] (M, L: Nb, py (5); Nb, PMe(2)Ph (6a); Ta, PMe(2)Ph (6b)). The assigned geometric arrangement of ligands is based upon (1)H NMR studies and single-crystal X-ray diffraction analyses of 3a, 3b, 4, 6a, and 6b. The salt complex [HPMe(2)Ph](+)[mer-NbCl(3)(OC(6)H(3)Pr(i)(2)-2,6)(3)](-) (7) has also been isolated and structurally characterized. The structural parameters for the neutral adducts are compared with those of previously reported hydrido aryloxides of tantalum. A small but consistent distortion away from octahedral geometry involving the bending of mutually trans anionic ligands toward the neutral donor group is observed. Theoretical analysis at several levels of theory (RHF, MP2, and DFT) on model compounds [Ta(OH)(2)(H)(2)(PH(3))(X)] (X = Cl, OH, H) show a distortion involving bending of the trans-hydride groups toward the PH(3) ligand for X = Cl and OH. This distortion can be accounted for in terms of an improvement in both X p to metal d pi-bonding and Ta-H sigma-bonding. The contribution of sigma-bonding effects is clearly shown in the case of X = H, where again a bend of the two hydride ligands toward the Ta-P bond is calculated. A smaller distortion of the Cl ligands in trans-mer-[Ta(OH)(3)(Cl)(2)(PH(3))] is also predicted.
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