metal-organic compounds
trans-dihydridobis[tris(dimethylamino)phosphane-κP]platinum(II)
ofaDepartment of Chemistry and Biochemistry, 1253 University of Oregon, Eugene, Oregon 97403-1253, USA
*Correspondence e-mail: dtyler@uoregon.edu
The molecule of the title compound, [PtH2(C6H18N3P)2], has a centrosymmetric square-planar structure in which the PtII atom is bonded to two H and two P atoms in a mutually trans configuration. The PtII atom sits on an inversion center and thus the contains only half the molecule. The Pt—P and Pt—H distances are 2.2574 (10) and 1.49 (7) Å, respectively.
Keywords: crystal structure; tris(dimethylamino)phosphane; platinum(II) complex; ligand-assisted hydration; nitrile hydration.
CCDC reference: 1051841
1. Related literature
For the synthesis of related compounds, see: Packett et al. (1985). For information on ligand-assisted hydration, see: Grotjahn (2005); Grotjahn et al. (2008a,b). For further information on nitrile hydration, see: García-Álvarez et al. (2011); Knapp et al. (2012, 2013a,b). For a review of the literature on nitrile hydration, see: Ahmed et al. (2011). For related structures, see: Packett et al. (1985); Robertson et al. (1986); Ferguson et al. (1979).
2. Experimental
2.1. Crystal data
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2.3. Refinement
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Data collection: APEX2 (Bruker, 2008); cell SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Supporting information
CCDC reference: 1051841
10.1107/S2056989015004351/pk2545sup1.cif
contains datablock I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S2056989015004351/pk2545Isup2.hkl
Synthesis of Pt(H)2(P(NMe2)3)2. In an inert atmosphere, PtCl2(COD) (0.1 g, 0.27 mmol) was dissolved in 10 ml dichloromethane. Two equivalents of P(NMe2)3 (0.1 ml, 0.54 mmol) were added dropwise with stirring. The solution turned from colorless to light yellow. The solution was stirred overnight. 31P NMR confirmed the formation of cis-PtCl2(P(NMe2)3)2: the free phosphane peak at 122 p.p.m. had disappeared and a peak with platinum satellites at 60 p.p.m. had appeared. The solvent and COD were removed in vacuo and the resulting light yellow powder was redissolved in acetonitrile. Two equivalents (0.02 g, 0.54 mmol) of NaBH4 were added with stirring. The solution was stirred for two hours and became bright orange; solids began to precipitate. The mixture was filtered through a celite plug to remove solids, and the solvent was removed. The brown solid was redissolved in minimal acetone and layered on top of water to precipitate brown crystals. 31P NMR: 129 p.p.m., Pt satellites at 138, 120 p.p.m.. JPt—P = 1,891 Hz. 1H NMR: t, 2.8 p.p.m. (JP—H = 5.5 Hz), tt, -3.5 (JP—H = 17.5 Hz, JPt—H = 405 Hz).
The structure was solved using
and refined with anisotropic thermal parameters for non-H atoms. The H atom bonded to the Pt atom was found in the residual density and refined with isotropic thermal parameters. H atoms in the Me groups were positioned geometrically and refined using a rigid group model: C—H = 0.98 Å, Uiso(H) = 1.5Ueq(C).The hydration of η6-p-cymene){P(NMe2)3}] complex is an excellent nitrile hydration catalyst (Knapp et al., 2012). Unlike related catalysts, this complex was active under acidic conditions (pH 3.5), and the improved stability of in an acidic medium yielded excellent results. Glycolonitrile (1) and lactonitrile (2) were hydrated fully to their corresponding and acetone cyanohydrin (3) was converted to 3-hydroxy-isobutyro nitrile (HIBAM) in 15% yield. Based on this result, we hypothesized that the tris(dimethylamino)phosphane ligand could be used in other homogeneous catalysts to enhance the rates of hydration. For this purpose, two new platinum complexes, Pt(H)(Cl)(P(NMe2)3)2 and Pt(H)2(P(NMe2)3)2, were synthesized and tested for hydration activity with a variety of including aromatic and aliphatic and cyanohydrins.
using homogeneous catalysts is often too slow for practical applications (Ahmed et al., 2011). Hydroxide is a much better than water, and thus to increase the rate, many hydration reactions are carried out at high pH. When a ligand on the catalyst is capable of hydrogen bonding, the entering water can be activated by hydrogen bonding interactions, avoiding the need for strongly basic solutions. Large rate accelerations in hydration reactions have been observed and attributed to this phenomenon, known as ligand assisted hydration or (Grotjahn, 2005; Grotjahn et al., 2008a,b). Complexes with phosphane ligands containing hydrogen bonding moieties, in particular tris(dimethylamino)phosphane (P(NMe2)3), have achieved excellent results in nitrile hydration reactions (García-Álvarez et al., 2011; Knapp et al., 2012, 2013a,b). In particular, we reported that the [RuCl2(Pt(H)2(P(NMe2)3)2 was characterized by single-crystal X-ray diffraction methods. The molecule has a square planar structure (P(1)(1 - x,2 - y,1 - z)-Pt(1) (x,y,z) –P(1)(x,y,z) = 180.0 °). The Pt—P bond lengths (2.2572 (8) Å) are comparable to other Pt(H)2(phosphane)2 complexes: Pt(H)2(PMe3)2, 2.259 (3) Å; Pt(PiPr3)2(H)2, 2.252 (1) Å; Pt(H)2(PtBu3)2, 2.276 (3) Å. (Packett et al., 1985; Robertson et al., 1986; Ferguson et al., 1979). The P atom coordination environments are slightly distorted tetrahedral: N(3)—P(1)—N(1) = 110.86 (15)°; N(3)—P(1)—N(2) = 100.94 (14)°; N(1)—P(1)—N(2) = 98.70 (13)°; N(3)—P(1)—Pt(1) = 112.12 (10)°; N(1)—P(1)—Pt(1) = 113.82 (9)°; N(2)—P(1)—Pt(1) = 119.08 (9)°). The three NMe2 groups bonded to each P atom have a staggered orientation with respect to the three NMe2 groups on the other P atom. Consequently, the two Pt—P—N(2) angles, with atoms in the same plane as the Pt—H bonds, are significantly distorted (119.08 (9)°) from the tetrahedral angle.
For the synthesis of related compounds, see: Packett et al. (1985). For information on ligand-assisted hydration, see: Grotjahn (2005); Grotjahn et al. (2008a,b). For further information on nitrile hydration, see: García-Álvarez et al. (2011); Knapp et al. (2012, 2013a,b). For a review of the literature on nitrile hydration, see: Ahmed et al. (2011). For related structures, see: Packett et al. (1985); Robertson et al. (1986); Ferguson et al. (1979).
Data collection: APEX2 (Bruker, 2008); cell
SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).[PtH2(C6H18N3P)2] | Z = 1 |
Mr = 523.51 | F(000) = 260 |
Triclinic, P1 | Dx = 1.689 Mg m−3 |
a = 7.8871 (19) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.9499 (19) Å | Cell parameters from 3285 reflections |
c = 9.891 (2) Å | θ = 3.0–26.9° |
α = 76.807 (4)° | µ = 6.97 mm−1 |
β = 73.241 (4)° | T = 173 K |
γ = 60.652 (3)° | Block, colorless |
V = 514.8 (2) Å3 | 0.08 × 0.06 × 0.03 mm |
Bruker APEXII CCD area-detector diffractometer | 2238 reflections with I > 2σ(I) |
Radiation source: Sealed tube with triumph monochromator | Rint = 0.020 |
φ and ω scans | θmax = 27.0°, θmin = 2.2° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1995) | h = −10→10 |
Tmin = 0.856, Tmax = 1.000 | k = −10→10 |
5813 measured reflections | l = −12→12 |
2238 independent reflections |
Refinement on F2 | 0 restraints |
Least-squares matrix: full | Hydrogen site location: mixed |
R[F2 > 2σ(F2)] = 0.023 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.059 | w = 1/[σ2(Fo2) + (0.0425P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.04 | (Δ/σ)max < 0.001 |
2238 reflections | Δρmax = 0.65 e Å−3 |
101 parameters | Δρmin = −0.69 e Å−3 |
[PtH2(C6H18N3P)2] | γ = 60.652 (3)° |
Mr = 523.51 | V = 514.8 (2) Å3 |
Triclinic, P1 | Z = 1 |
a = 7.8871 (19) Å | Mo Kα radiation |
b = 7.9499 (19) Å | µ = 6.97 mm−1 |
c = 9.891 (2) Å | T = 173 K |
α = 76.807 (4)° | 0.08 × 0.06 × 0.03 mm |
β = 73.241 (4)° |
Bruker APEXII CCD area-detector diffractometer | 2238 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1995) | 2238 reflections with I > 2σ(I) |
Tmin = 0.856, Tmax = 1.000 | Rint = 0.020 |
5813 measured reflections |
R[F2 > 2σ(F2)] = 0.023 | 0 restraints |
wR(F2) = 0.059 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.65 e Å−3 |
2238 reflections | Δρmin = −0.69 e Å−3 |
101 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
x | y | z | Uiso*/Ueq | ||
Pt1 | 0.5000 | 1.0000 | 0.5000 | 0.02501 (8) | |
P1 | 0.58089 (14) | 0.80751 (13) | 0.70124 (10) | 0.02302 (18) | |
N1 | 0.8017 (5) | 0.7594 (5) | 0.7244 (4) | 0.0332 (7) | |
N2 | 0.6130 (5) | 0.5757 (4) | 0.7200 (3) | 0.0272 (6) | |
N3 | 0.4051 (6) | 0.8932 (5) | 0.8436 (4) | 0.0405 (9) | |
C1 | 0.8862 (7) | 0.8928 (6) | 0.6632 (5) | 0.0372 (9) | |
H1A | 1.0160 | 0.8404 | 0.6880 | 0.056* | |
H1B | 0.7971 | 1.0185 | 0.7007 | 0.056* | |
H1C | 0.9028 | 0.9096 | 0.5597 | 0.056* | |
C2 | 0.9106 (7) | 0.6069 (7) | 0.8243 (5) | 0.0433 (11) | |
H2A | 1.0362 | 0.6085 | 0.8177 | 0.065* | |
H2B | 0.9382 | 0.4808 | 0.8019 | 0.065* | |
H2C | 0.8308 | 0.6284 | 0.9209 | 0.065* | |
C3 | 0.7765 (7) | 0.4524 (6) | 0.6164 (5) | 0.0400 (10) | |
H3A | 0.7849 | 0.3224 | 0.6347 | 0.060* | |
H3B | 0.9016 | 0.4438 | 0.6244 | 0.060* | |
H3C | 0.7529 | 0.5083 | 0.5205 | 0.060* | |
C4 | 0.4314 (7) | 0.5651 (7) | 0.7249 (5) | 0.0433 (11) | |
H4A | 0.4592 | 0.4288 | 0.7360 | 0.065* | |
H4B | 0.3844 | 0.6298 | 0.6366 | 0.065* | |
H4C | 0.3289 | 0.6295 | 0.8055 | 0.065* | |
C5 | 0.2224 (7) | 1.0666 (8) | 0.8357 (6) | 0.0543 (14) | |
H5B | 0.1401 | 1.0908 | 0.9314 | 0.081* | |
H5C | 0.1509 | 1.0512 | 0.7769 | 0.081* | |
H5D | 0.2511 | 1.1764 | 0.7935 | 0.081* | |
C6 | 0.4176 (8) | 0.7934 (7) | 0.9864 (5) | 0.0488 (12) | |
H6C | 0.2983 | 0.8692 | 1.0539 | 0.073* | |
H6D | 0.5356 | 0.7789 | 1.0119 | 0.073* | |
H6A | 0.4274 | 0.6649 | 0.9892 | 0.073* | |
H1 | 0.490 (10) | 1.163 (10) | 0.557 (7) | 0.070 (19)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pt1 | 0.03283 (12) | 0.02060 (11) | 0.02016 (11) | −0.01088 (8) | −0.01106 (8) | 0.00457 (7) |
P1 | 0.0288 (4) | 0.0194 (4) | 0.0196 (4) | −0.0097 (4) | −0.0092 (3) | 0.0027 (3) |
N1 | 0.0396 (18) | 0.0315 (17) | 0.0374 (19) | −0.0219 (15) | −0.0225 (15) | 0.0127 (14) |
N2 | 0.0358 (17) | 0.0198 (15) | 0.0279 (16) | −0.0138 (13) | −0.0115 (13) | 0.0031 (12) |
N3 | 0.043 (2) | 0.0329 (19) | 0.0202 (16) | −0.0017 (16) | −0.0033 (14) | 0.0009 (14) |
C1 | 0.037 (2) | 0.034 (2) | 0.047 (2) | −0.0233 (18) | −0.0090 (18) | 0.0020 (18) |
C2 | 0.047 (3) | 0.042 (2) | 0.048 (3) | −0.024 (2) | −0.030 (2) | 0.017 (2) |
C3 | 0.050 (3) | 0.024 (2) | 0.039 (2) | −0.0111 (18) | −0.0111 (19) | −0.0037 (17) |
C4 | 0.052 (3) | 0.050 (3) | 0.042 (2) | −0.035 (2) | −0.023 (2) | 0.014 (2) |
C5 | 0.040 (2) | 0.047 (3) | 0.041 (3) | 0.003 (2) | −0.003 (2) | −0.001 (2) |
C6 | 0.054 (3) | 0.043 (3) | 0.024 (2) | −0.008 (2) | −0.0055 (19) | 0.0046 (18) |
Pt1—P1 | 2.2574 (10) | C2—H2A | 0.9800 |
Pt1—P1i | 2.2574 (10) | C2—H2B | 0.9800 |
Pt1—H1 | 1.49 (7) | C2—H2C | 0.9800 |
P1—N3 | 1.660 (4) | C3—H3A | 0.9800 |
P1—N1 | 1.664 (3) | C3—H3B | 0.9800 |
P1—N2 | 1.705 (3) | C3—H3C | 0.9800 |
N1—C1 | 1.450 (5) | C4—H4A | 0.9800 |
N1—C2 | 1.451 (5) | C4—H4B | 0.9800 |
N2—C3 | 1.460 (5) | C4—H4C | 0.9800 |
N2—C4 | 1.462 (5) | C5—H5B | 0.9800 |
N3—C5 | 1.432 (6) | C5—H5C | 0.9800 |
N3—C6 | 1.458 (6) | C5—H5D | 0.9800 |
C1—H1A | 0.9800 | C6—H6C | 0.9800 |
C1—H1B | 0.9800 | C6—H6D | 0.9800 |
C1—H1C | 0.9800 | C6—H6A | 0.9800 |
P1—Pt1—P1i | 180.0 | N1—C2—H2C | 109.5 |
P1—Pt1—H1 | 90 (3) | H2A—C2—H2C | 109.5 |
P1i—Pt1—H1 | 90 (3) | H2B—C2—H2C | 109.5 |
N3—P1—N1 | 110.9 (2) | N2—C3—H3A | 109.5 |
N3—P1—N2 | 101.05 (19) | N2—C3—H3B | 109.5 |
N1—P1—N2 | 98.82 (17) | H3A—C3—H3B | 109.5 |
N3—P1—Pt1 | 112.10 (13) | N2—C3—H3C | 109.5 |
N1—P1—Pt1 | 113.77 (12) | H3A—C3—H3C | 109.5 |
N2—P1—Pt1 | 118.93 (12) | H3B—C3—H3C | 109.5 |
C1—N1—C2 | 112.8 (3) | N2—C4—H4A | 109.5 |
C1—N1—P1 | 121.1 (3) | N2—C4—H4B | 109.5 |
C2—N1—P1 | 125.2 (3) | H4A—C4—H4B | 109.5 |
C3—N2—C4 | 110.0 (4) | N2—C4—H4C | 109.5 |
C3—N2—P1 | 114.7 (3) | H4A—C4—H4C | 109.5 |
C4—N2—P1 | 113.4 (3) | H4B—C4—H4C | 109.5 |
C5—N3—C6 | 114.0 (4) | N3—C5—H5B | 109.5 |
C5—N3—P1 | 122.7 (3) | N3—C5—H5C | 109.5 |
C6—N3—P1 | 123.1 (3) | H5B—C5—H5C | 109.5 |
N1—C1—H1A | 109.5 | N3—C5—H5D | 109.5 |
N1—C1—H1B | 109.5 | H5B—C5—H5D | 109.5 |
H1A—C1—H1B | 109.5 | H5C—C5—H5D | 109.5 |
N1—C1—H1C | 109.5 | N3—C6—H6C | 109.5 |
H1A—C1—H1C | 109.5 | N3—C6—H6D | 109.5 |
H1B—C1—H1C | 109.5 | H6C—C6—H6D | 109.5 |
N1—C2—H2A | 109.5 | N3—C6—H6A | 109.5 |
N1—C2—H2B | 109.5 | H6C—C6—H6A | 109.5 |
H2A—C2—H2B | 109.5 | H6D—C6—H6A | 109.5 |
N3—P1—N1—C1 | −100.5 (4) | N3—P1—N2—C4 | 58.6 (3) |
N2—P1—N1—C1 | 154.0 (3) | N1—P1—N2—C4 | 172.0 (3) |
Pt1—P1—N1—C1 | 26.9 (4) | Pt1—P1—N2—C4 | −64.5 (3) |
N3—P1—N1—C2 | 67.7 (4) | N1—P1—N3—C5 | 130.0 (4) |
N2—P1—N1—C2 | −37.8 (4) | N2—P1—N3—C5 | −126.0 (5) |
Pt1—P1—N1—C2 | −164.9 (3) | Pt1—P1—N3—C5 | 1.7 (5) |
N3—P1—N2—C3 | −174.0 (3) | N1—P1—N3—C6 | −53.6 (5) |
N1—P1—N2—C3 | −60.5 (3) | N2—P1—N3—C6 | 50.4 (5) |
Pt1—P1—N2—C3 | 62.9 (3) | Pt1—P1—N3—C6 | 178.1 (4) |
Symmetry code: (i) −x+1, −y+2, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [PtH2(C6H18N3P)2] |
Mr | 523.51 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 173 |
a, b, c (Å) | 7.8871 (19), 7.9499 (19), 9.891 (2) |
α, β, γ (°) | 76.807 (4), 73.241 (4), 60.652 (3) |
V (Å3) | 514.8 (2) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 6.97 |
Crystal size (mm) | 0.08 × 0.06 × 0.03 |
Data collection | |
Diffractometer | Bruker APEXII CCD area-detector |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1995) |
Tmin, Tmax | 0.856, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5813, 2238, 2238 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.639 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.059, 1.04 |
No. of reflections | 2238 |
No. of parameters | 101 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.65, −0.69 |
Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2000), SHELXTL (Sheldrick, 2008).
Acknowledgements
Acknowledgment is made to the National Science Foundation (CHE 1360347) for the support of this research.
References
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The hydration of nitriles using homogeneous catalysts is often too slow for practical applications (Ahmed et al., 2011). Hydroxide is a much better nucleophile than water, and thus to increase the rate, many hydration reactions are carried out at high pH. When a ligand on the catalyst is capable of hydrogen bonding, the entering water nucleophile can be activated by hydrogen bonding interactions, avoiding the need for strongly basic solutions. Large rate accelerations in hydration reactions have been observed and attributed to this phenomenon, known as ligand assisted hydration or bifunctional catalysis (Grotjahn, 2005; Grotjahn et al., 2008a,b). Complexes with phosphane ligands containing hydrogen bonding moieties, in particular tris(dimethylamino)phosphane (P(NMe2)3), have achieved excellent results in nitrile hydration reactions (García-Álvarez et al., 2011; Knapp et al., 2012, 2013a,b). In particular, we reported that the [RuCl2(η6-p-cymene){P(NMe2)3}] complex is an excellent nitrile hydration catalyst (Knapp et al., 2012). Unlike related catalysts, this complex was active under acidic conditions (pH 3.5), and the improved stability of cyanohydrins in an acidic medium yielded excellent results. Glycolonitrile (1) and lactonitrile (2) were hydrated fully to their corresponding amides and acetone cyanohydrin (3) was converted to 3-hydroxy-isobutyro nitrile (HIBAM) in 15% yield. Based on this result, we hypothesized that the tris(dimethylamino)phosphane ligand could be used in other homogeneous catalysts to enhance the rates of hydration. For this purpose, two new platinum complexes, Pt(H)(Cl)(P(NMe2)3)2 and Pt(H)2(P(NMe2)3)2, were synthesized and tested for hydration activity with a variety of nitriles, including aromatic and aliphatic nitriles and cyanohydrins.
Pt(H)2(P(NMe2)3)2 was characterized by single-crystal X-ray diffraction methods. The molecule has a square planar structure (P(1)(1 - x,2 - y,1 - z)-Pt(1) (x,y,z) –P(1)(x,y,z) = 180.0 °). The Pt—P bond lengths (2.2572 (8) Å) are comparable to other Pt(H)2(phosphane)2 complexes: Pt(H)2(PMe3)2, 2.259 (3) Å; Pt(PiPr3)2(H)2, 2.252 (1) Å; Pt(H)2(PtBu3)2, 2.276 (3) Å. (Packett et al., 1985; Robertson et al., 1986; Ferguson et al., 1979). The P atom coordination environments are slightly distorted tetrahedral: N(3)—P(1)—N(1) = 110.86 (15)°; N(3)—P(1)—N(2) = 100.94 (14)°; N(1)—P(1)—N(2) = 98.70 (13)°; N(3)—P(1)—Pt(1) = 112.12 (10)°; N(1)—P(1)—Pt(1) = 113.82 (9)°; N(2)—P(1)—Pt(1) = 119.08 (9)°). The three NMe2 groups bonded to each P atom have a staggered orientation with respect to the three NMe2 groups on the other P atom. Consequently, the two Pt—P—N(2) angles, with atoms in the same plane as the Pt—H bonds, are significantly distorted (119.08 (9)°) from the tetrahedral angle.