trans-Di­iodo­bis(1,3,5-tri­aza-7-phosphaadamantane)­platinum(II)

The crystal structure of the title compound, trans-[PtI₂(C₆H₁₂N₃P)₂], describes one of the few platinum(II) complexes containing two of the water-soluble 1,3,5-tri­aza-7-phosphaadamantane ligands reported to date. The complex crystallizes on an inversion centre with the most important bond lengths and angles being Pt-P 2.3128 (12) Å, Pt-I 2.6022 (6) Å, P-Pt-I 90.94 (3)° and P'-Pt-I 89.06 (3)°.

S1. Comment

The air-stable water-soluble 1,3,5-triaza-7-phosphaadamantane ligand, PTA, is highly versitile as it enables the synthesis of water-soluble complexes without the additional complication of introducing a charged species to the complex. Numerous PTA complexes exhibiting catalytic activity have been reported in the last few years underlining the world-wide interest in its unique characteristics (Darensbourg et al., 1994, 1995; Joó et al., 1996). While platinum(II) and palladium(II) complex containing three or more PTA ligands are fairly soluble in water and even methanol, the bis PTA complexes are only soluble to a limited extent in water and almost insoluble in methanol. No mono PTA complexes of platinum(II) and palladium(II) are reported to date. \sch

In this paper we report the structure of trans-diiodobis(PTA)platinum(II) as part of our systematic investigation to the basic coordination mode and solution properties of these complexes. Only a few platinum(II) bis PTA structures have been reported to date (Assefa et al., 1995; Darensbourg et al., 1997; Otto et al., 1998) and the title compound describes only the second example of such a complex with a trans geometry.

The compound crystallizes on an inversion centre as well defined square planar moieties with the phosphine ligands in a trans orientation. All angles in the coordination polyhedron are very close to the ideal 90° with P—Pt—I 90.94 (3) and Pⁱ—Pt—I 89.06 (3)°, respectively. The P—Pt—Pⁱ and I—Pt—Iⁱ angles are 180° on accord of the symmetry [(i) -x, -y, -z].

All bond distances and angles are within normal ranges and are very similar to those in analogous diiodo bisphosphine complex listed in Table 1. The Pt—I bond distance do not seem to be very sensitive to the phosphine ligand employed in the different structures with the distances ranging between 2.599 (2) and 2.626 (2) Å. Both the Pt—P and Pt—I bond distances of 2.3128 (12) and 2.6022 (6) Å are virtually identical to those found in the analogous PMe₃ complex of 2.315 (4) and 2.599 (2), respectively, indicative of the closely resembling characteristics of these two ligand systems. The Pt—P bond distances are comparable with the 2.318 (2) Å found for the corresponding PPh₃ complex while they are shorter than those found for the bulkier PCy₃ and P(o-Tol)₃ complexes. The Pt—P bond distances of the title compound are very similar to those found in other Pt complexes containing two PTA ligands in a trans orientation and even the 2.323 (2) and 2.3174 (11) Å found in the [PtCl(PTA)₃]Cl and [Pt(I)₂(PTA)₃] complexes containing 3 PTA ligands.

The average C—P—Pt and C—P—C angles of 119.21 (16) and 98.1 (2) ° respectively are indicative of the small steric demand of the PTA ligand. In addition to this the effective- and Tolman cone angles for the PTA ligand in the title compound were determined as 117.3 and 118.2°, respectively, using the actual Pt—P bond distance of 2.3128 (11) and a distance of 2.28 Å according to the definition (Tolman, 1977; Otto et al., 2000). These values are in excellent agreement with the 118.3 and 119.5° reported recently (Otto & Roodt, 2001), confirming the rigid character of the ligand.

Related literature

For related literature, see: Assefa et al. (1995); Darensbourg et al. (1994, 1995, 1997); Joó et al. (1996); Otto et al. (1998); Otto, Roodt & Smith (2000); Sheldrick (1997, 1997); Tolman (1977).

S2. Experimental

cis-[Pt(Cl)₂(PTA)₂] (7 mg, 0.0121 mmol) was dissolved in water (5 ml) and an aqueous solution (1 ml) of NaI (7 mg, 0.0467 mmol) was added. Slow evaporation of the solvent yielded bright yellow crystals suitable for X-ray analysis in a near quantitative yield.

S3. Refinement

The data were collected on a Bruker SMART CCD diffractometer. H atoms were introduced at calculated positions and refined using standard SHELXL97 (Sheldrick, 1997) constraints. The maximum residual electron density of 1.730 and -1.591 e Å^-3 are located within 1 Å of the platinum atom.

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SMART; data reduction: SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. Structure showing the numbering scheme and displacement ellipsoids (30% probability) for the title compound. Hydrogen atoms are omitted for clarity. [Symmetry code: (i) -x, -y, -z]

trans-diiodobis(1,3,5-triaza-7-phosphaadamantane)platinum(II)

Crystal data

[PtI2(C6H12N3P)2]	F(000) = 704
Mr = 763.20	Dx = 2.663 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 7.472 (2) Å	Cell parameters from 6552 reflections
b = 12.141 (4) Å	θ = 2.6–28.3°
c = 10.537 (3) Å	µ = 10.79 mm^−1
β = 95.348 (5)°	T = 293 K
V = 951.7 (5) Å^3	Rectangle, yellow
Z = 2	0.26 × 0.22 × 0.12 mm

Data collection

Bruker SMART CCD diffractometer	2345 independent reflections
Radiation source: fine-focus sealed tube	1944 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
ω scans	θmax = 28.3°, θmin = 2.6°
Absorption correction: empirical (SADABS; Sheldrick, 1996)	h = −9→5
Tmin = 0.083, Tmax = 0.285	k = −12→16
6552 measured reflections	l = −14→12

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: riding model
R[F^2 > 2σ(F^2)] = 0.022	H-atom parameters constrained
wR(F^2) = 0.050	w = 1/[σ^2(Fo^2) + (0.0254P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.98	(Δ/σ)max = 0.001
2345 reflections	Δρmax = 1.73 e Å^−3
108 parameters	Δρmin = −1.59 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0063 (2)

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.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
Pt	0.0000	0.0000	0.0000	0.02579 (8)
I	0.25022 (4)	−0.04039 (3)	−0.14965 (3)	0.04287 (10)
P	0.12312 (15)	0.17097 (8)	0.05070 (10)	0.0279 (2)
N1	0.3365 (5)	0.2837 (3)	0.2348 (3)	0.0385 (9)
N2	0.0959 (5)	0.3899 (3)	0.1148 (3)	0.0386 (9)
N3	0.3631 (6)	0.3377 (3)	0.0102 (4)	0.0426 (9)
C1	0.2569 (6)	0.1748 (3)	0.2064 (4)	0.0364 (11)
H1A	0.1807	0.1552	0.2726	0.043 (4)*
H1B	0.3522	0.1204	0.2072	0.043 (4)*
C2	−0.0158 (6)	0.2943 (4)	0.0706 (5)	0.0398 (11)
H2A	−0.0828	0.3121	−0.0100	0.043 (4)*
H2B	−0.1014	0.2787	0.1320	0.043 (4)*
C3	0.2884 (7)	0.2341 (4)	−0.0452 (4)	0.0434 (12)
H3A	0.3858	0.1825	−0.0531	0.043 (4)*
H3B	0.2317	0.2487	−0.1301	0.043 (4)*
C4	0.1947 (7)	0.3668 (4)	0.2393 (4)	0.0409 (11)
H4A	0.2483	0.4347	0.2732	0.043 (4)*
H4B	0.1101	0.3419	0.2975	0.043 (4)*
C5	0.2210 (7)	0.4200 (4)	0.0227 (4)	0.0422 (11)
H5A	0.2767	0.4897	0.0478	0.043 (4)*
H5B	0.1542	0.4303	−0.0599	0.043 (4)*
C6	0.4553 (6)	0.3167 (4)	0.1376 (5)	0.0460 (13)
H6A	0.5439	0.2592	0.1304	0.043 (4)*
H6B	0.5193	0.3830	0.1665	0.043 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt	0.02744 (13)	0.02412 (12)	0.02531 (12)	0.00359 (9)	−0.00027 (8)	−0.00592 (8)
I	0.04472 (19)	0.03609 (18)	0.05049 (19)	0.00399 (14)	0.01865 (15)	−0.01132 (13)
P	0.0306 (6)	0.0246 (5)	0.0282 (5)	0.0023 (4)	0.0009 (4)	−0.0053 (4)
N1	0.048 (2)	0.0266 (19)	0.038 (2)	−0.0035 (17)	−0.0127 (18)	−0.0012 (15)
N2	0.043 (2)	0.0245 (19)	0.047 (2)	0.0077 (16)	−0.0024 (18)	−0.0029 (15)
N3	0.050 (3)	0.031 (2)	0.048 (2)	−0.0054 (18)	0.011 (2)	−0.0055 (16)
C1	0.045 (3)	0.025 (2)	0.037 (2)	0.0014 (19)	−0.010 (2)	0.0012 (17)
C2	0.037 (3)	0.034 (2)	0.047 (3)	0.0103 (19)	−0.003 (2)	−0.0057 (19)
C3	0.054 (3)	0.036 (3)	0.042 (3)	−0.005 (2)	0.016 (2)	−0.009 (2)
C4	0.058 (3)	0.031 (2)	0.033 (2)	0.001 (2)	0.002 (2)	−0.0094 (18)
C5	0.059 (3)	0.026 (2)	0.042 (3)	0.003 (2)	0.001 (2)	0.0026 (18)
C6	0.036 (3)	0.027 (2)	0.072 (4)	−0.001 (2)	−0.009 (3)	−0.005 (2)

Geometric parameters (Å, º)

Pt—P^i	2.3128 (12)	N3—C6	1.473 (6)
Pt—P	2.3128 (12)	N3—C3	1.474 (5)
Pt—I^i	2.6022 (6)	C1—H1A	0.9700
Pt—I	2.6022 (6)	C1—H1B	0.9700
P—C3	1.835 (5)	C2—H2A	0.9700
P—C1	1.841 (4)	C2—H2B	0.9700
P—C2	1.845 (4)	C3—H3A	0.9700
N1—C4	1.467 (6)	C3—H3B	0.9700
N1—C1	1.469 (5)	C4—H4A	0.9700
N1—C6	1.473 (6)	C4—H4B	0.9700
N2—C5	1.455 (6)	C5—H5A	0.9700
N2—C4	1.471 (5)	C5—H5B	0.9700
N2—C2	1.480 (6)	C6—H6A	0.9700
N3—C5	1.473 (6)	C6—H6B	0.9700
P^i—Pt—P	180.00 (2)	P—C2—H2A	109.3
P^i—Pt—I^i	90.94 (3)	N2—C2—H2B	109.3
P—Pt—I^i	89.06 (3)	P—C2—H2B	109.3
P^i—Pt—I	89.06 (3)	H2A—C2—H2B	108.0
P—Pt—I	90.94 (3)	N3—C3—P	112.8 (3)
I^i—Pt—I	180.000 (13)	N3—C3—H3A	109.0
C1—P—C2	98.2 (2)	P—C3—H3A	109.0
C1—P—C3	98.2 (2)	N3—C3—H3B	109.0
C2—P—C3	97.9 (2)	P—C3—H3B	109.0
C1—P—Pt	113.57 (13)	H3A—C3—H3B	107.8
C2—P—Pt	122.61 (16)	N1—C4—N2	114.0 (3)
C3—P—Pt	121.44 (14)	N1—C4—H4A	108.7
C4—N1—C1	110.2 (4)	N2—C4—H4A	108.7
C4—N1—C6	108.6 (3)	N1—C4—H4B	108.7
C1—N1—C6	111.2 (3)	N2—C4—H4B	108.7
C5—N2—C4	110.0 (4)	H4A—C4—H4B	107.6
C5—N2—C2	111.4 (4)	N2—C5—N3	113.8 (3)
C4—N2—C2	110.6 (3)	N2—C5—H5A	108.8
C5—N3—C6	108.4 (4)	N3—C5—H5A	108.8
C5—N3—C3	111.4 (4)	N2—C5—H5B	108.8
C6—N3—C3	109.9 (4)	N3—C5—H5B	108.8
N1—C1—P	112.3 (3)	H5A—C5—H5B	107.7
N1—C1—H1A	109.1	N1—C6—N3	114.8 (4)
P—C1—H1A	109.1	N1—C6—H6A	108.6
N1—C1—H1B	109.1	N3—C6—H6A	108.6
P—C1—H1B	109.1	N1—C6—H6B	108.6
H1A—C1—H1B	107.9	N3—C6—H6B	108.6
N2—C2—P	111.5 (3)	H6A—C6—H6B	107.5
N2—C2—H2A	109.3

Symmetry code: (i) −x, −y, −z.