Crystal structure of trans-dihydrido­bis[tris­(di­methyl­amino)­phosphane-κP]platinum(II)

Abstract

The mol­ecule of the title compound, [PtH₂(C₆H₁₈N₃P)₂], has a centrosymmetric square-planar structure in which the Pt^II atom is bonded to two H and two P atoms in a mutually trans configuration. The Pt^II atom sits on an inversion center and thus the asymmetric unit contains only half the mol­ecule. The Pt—P and Pt—H distances are 2.2574 (10) and 1.49 (7) Å, respectively.

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 ▸).

Experimental  

Crystal data  

• [PtH₂(C₆H₁₈N₃P)₂]

• M _r = 523.51

• Triclinic,

• a = 7.8871 (19) Å

• b = 7.9499 (19) Å

• c = 9.891 (2) Å

• α = 76.807 (4)°

• β = 73.241 (4)°

• γ = 60.652 (3)°

• V = 514.8 (2) ų

• Z = 1

• Mo Kα radiation

• μ = 6.97 mm⁻¹

• T = 173 K

• 0.08 × 0.06 × 0.03 mm

Data collection  

• Bruker APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1995 ▸) T _min = 0.856, T _max = 1.000

• 5813 measured reflections

• 2238 independent reflections

• 2238 reflections with I > 2σ(I)

• R _int = 0.020

Refinement  

• R[F ² > 2σ(F ²)] = 0.023

• wR(F ²) = 0.059

• S = 1.04

• 2238 reflections

• 101 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.65 e Å⁻³

• Δρ_min = −0.69 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▸); cell refinement: 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.

Supplementary Material

CCDC reference: 1051841

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

S1. Comment

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.

S2. Experimental

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.. J_Pt—P = 1,891 Hz. ¹H NMR: t, 2.8 p.p.m. (J_P—H = 5.5 Hz), tt, -3.5 (J_P—H = 17.5 Hz, J_Pt—H = 405 Hz).

S3. Refinement

The structure was solved using direct methods 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, U_iso(H) = 1.5U_eq(C).

Figures

Fig. 1.

The crystal structure of trans-dihydridobis[tris(dimethylamino)phosphane]platinum (II) with 50% probability displacement ellipsoids. H atoms in the Me groups are omitted for clarity. [Symmetry code (A): 1 - x, 2 - y, 1 - z].

Crystal data

[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

Data collection

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

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

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	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)*

Atomic displacement parameters (Ų)

	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)

Geometric parameters (Å, º)

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.