cis-Bis[(3-amino­prop­yl)dimethyl­phosphine-[kappa]²N,P]palladium(II) dichloride methanol solvate

In the title compound, cis-[Pd(C₅H₁₄NP)₂]Cl₂·CH₄O, the coordination geometry around the Pd^II center is distorted square planar, with a cis-P₂N₂ configuration of the two chelating (3-amino­prop­yl)dimethyl­phosphine (pdmp) ligands. The six-membered pdmp chelate rings adopt chair conformations, and pairing of the chairs designates the complex cation as a (C_s)-chair₂ conformer. The distances between the Pd^II center and the Cl^- anions are greater than 4.5 Å, indicating no obvious inter­action.

S1. Comment

In transition-metal complexes with chelating ligands, the chelate ring size, i.e. the number of backbone C atoms between two ligating atoms, often exerts severe effects on the thermal stabilities, molecular structures and chemical reactivities of the complexes (Stoppioni et al., 1982; Poverenov et al., 2005). Aminoalkylphosphines are bidentate ligands that can vary the chelate ring sizes, and their metal complexes have recently attracted much interest in application as effective homogeneous catalysts (Müller et al., 2002; Andrieu et al., 2006). We have previously prepared a number of transition metal complexes bearing (2-aminoethyl)dimethylphosphine (edmp, NH₂CH₂CH₂PMe₂), which is one of the most fundamental and less sterically demanding of the aminoalkylphosphines, forming a five-membered chelate ring (Kashiwabara et al., 1997; Suzuki et al., 1994, 1996; Kita et al., 1994; Kinoshita et al., 1980, 1981). In contrast, to our knowledge, there have so far been no reports on the metal complexes of (3-aminopropyl)dimethylphosphine (pdmp, NH₂CH₂CH₂CH₂PMe₂), which gives the corresponding six-membered amine–phosphine chelate ring. In the present study, we have prepared the first example of a pdmp complex of palladium(II), cis-[Pd(pdmp)₂]Cl₂·MeOH, (I), and compared the crystal structure with those of the analogous edmp and related complexes.

The analysis revealed that the Pd^II complex cation in (I) possesses two chelating pdmp ligands in a cis-P₂N₂ configuration (Fig. 1). The chelate bite angles of pdmp are 86.40 (5)–88.54 (6)° (Table 1), which are larger than those of edmp in cis-[Pd(edmp)₂]Cl(BF₄), (II) [83.9 (3)–84.5 (3)°; Suzuki et al., 1996]. This fact infers that the steric interaction between mutually cis-positioned –PMe₂ groups is somewhat larger in (I) than in (II). In general, in four-coordinate square-planar complexes, the trans-P₂N₂ isomer is advantageous in regard to the intramolecular steric congestion arising from the bulky substituents on P atoms, but the strong trans influence of the phosphines tends to stabilize the cis-P₂N₂ configuration. The preferential formation of the cis-isomer in complex (I) indicates that the trans influence of the –PMe₂ group is still the primary effect for determining the complex geometry, even in the sterically more demanding pdmp six-membered chelate ring system. The coordination geometry around the Pd^II center is significantly distorted from square-planar. The dihedral angle between the Pd/P1/N1 and Pd/P2/N2 planes is 14.5 (1)°. This tetrahedral distortion of the Pd^II coordination geometry is much larger than that observed in the related 8-dimethylphosphinoquinoline (Me₂Pqn) complex cis-[Pd(Me₂Pqn)₂](BF₄)₂ (the corresponding dihedral angle is 10.3°), where a severe steric repulsion was expected between ortho-H atoms of mutually cis-positioned quinolyl donor groups (Suzuki et al., 1995). It is noteworthy that the edmp complex (II) adopts an almost planar PdP₂N₂ coordination (Suzuki et al., 1996). In (I), each six-membered pdmp chelate ring takes a chair conformation, and a pair of chairs designate the complex cation as a (C_s)-chair₂ conformer. This is in contrast to a similar (3-aminopropyl)diphenylphosphine complex of cis-[Pt(H₂NCH₂CH₂CH₂PPh₂)₂]Cl, which was characterized as a (C₂)-chair₂ conformer (Habtemariam et al., 2001). In the (C_s)-chair₂ conformer, greater steric congestion is expected between the substituents on the mutually cis-positioned P donor atoms than in the (C₂)-chair₂ conformer. In fact, the C1···C6 distance is 3.257 (3) Å, and the closest H···H contact between the two methyl groups is 2.29 Å for H1C···H6A, which is nearly the sum of the van der Waals radii of two H atoms (2.44 Å).

The Pd—P and Pd—N bond lengths in (I) (Table 1) are comparable to those in (II) [Pd—P = 2.243 (3)–2.248 (3) Å and Pd—N = 2.123 (10)–2.153 (10) Å]. One of the most intriguing differences in the crystal structures of (I) and (II) is the location of the Cl⁻ anion(s). In (II), the anion is located above the Pd^II coordination plane with a Pd···Cl distance of 3.166 (3) Å, indicating a weak interaction between these atoms. In the crystal structure of cis-[Pd(Ph₂Pqn)₂]Cl₂ (Ph₂Pqn is 8-diphenylphosphinoquinoline), the two Cl⁻ anions are located above and below the Pd^II coordination plane, with Pd···Cl distances of 3.262 (3) and 3.386 (3) Å (Suzuki, 2004). In contrast to these compounds, complex (I) does not exhibit any interaction between the Pd^II center and Cl⁻ anions (> 4.5 Å), although one side of the Pd^II coordination plane is sterically open for such an interaction. Instead, the hydrogen-bonding interactions between the coordinated amino groups of pdmp ligands and Cl⁻ counter anions are effective in (I) (Table 2). It is expected that these hydrogen bonds stabilize the less preferable (C_s)-chair₂ conformer. The methanol molecule is hydrogen-bonded to atom Cl1 and not coordinated to the Pd atom, the Pd1···O1 distance being 3.800 (2) Å.

S2. Experimental

The compound (I) was prepared by a reaction of [PdCl₂(C₆H₅CN)₂] (283 mg, 0.74 mmol) and pdmp (0.25 ml, 2.1 mmol) in acetonitrile. The crude product obtained by evaporation of the solvent was purified by Sephadex LH-20 column chromatography using methanol as an eluant. Evaporation of the solvent from the eluate left a white powder of [Pd(pdmp)₂]Cl₂·MeOH·H₂O (yield 223 mg, 55%). Analysis, calculated for C₁₀H₂₈Cl₂N₂P₂Pd·CH₄O·H₂O: C 28.4, H 7.36, N 6.02%; found: C 28.6, H 7.33, N 6.01%. When the compound was recrystallized from dimethyl sulfoxide by vapor diffusion of diethyl ether, colorless needle-shaped crystals of the monohydrate were afforded. Analysis, calculated for C₁₀H₂₈Cl₂N₂P₂Pd·H₂O: C 27.7, H 6.97, N 6.46%; found: C 27.9, H 6.80, N 6.49%. Crystals of the methanol solvate, (I), suitable for X-ray analysis were deposited by vapor diffusion of diethyl ether into a methanol solution.

S3. Refinement

H atoms bonded to the C and N atoms were positioned geometrically and constrained to ride on their parent atoms, with C—H = 0.98 and 0.99 Å, N–H = 0.92 Å, and U_iso(H) = 1.2U_eq(C,N). The hydroxy H atom of the methanol molecule was located in a difference map and refined isotropically.

Computing details

Data collection: CrystalClear (Rigaku, 2001); cell refinement: CrystalClear; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. An ORTEP-3 (Farrugia, 1997) view of the cationic complex in (I), showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.

cis-Bis[(3-aminopropyl)dimethylphosphine-κ²N,P]palladium(II) dichloride methanol solvate

Crystal data

[Pd(C5H14NP)2]Cl2·CH4O	F(000) = 920
Mr = 447.65	Dx = 1.549 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71070 Å
Hall symbol: -P 2ybc	Cell parameters from 5814 reflections
a = 9.904 (6) Å	θ = 3.0–27.5°
b = 9.654 (6) Å	µ = 1.41 mm^−1
c = 20.130 (13) Å	T = 193 K
β = 94.228 (11)°	Prism, colorless
V = 1920 (2) Å^3	0.20 × 0.10 × 0.10 mm
Z = 4

Data collection

Rigaku Mercury diffractometer	4289 independent reflections
Graphite monochromator	4026 reflections with I > 2σ(I)
Detector resolution: 7.31 pixels mm^-1	Rint = 0.024
ω scans	θmax = 27.5°, θmin = 3.1°
Absorption correction: multi-scan (Jacobson, 1998)	h = −12→12
Tmin = 0.766, Tmax = 0.872	k = −12→10
14453 measured reflections	l = −26→23

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.029	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.056	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ^2(Fo^2) + (0.0206P)^2 + 1.828P] where P = (Fo^2 + 2Fc^2)/3
4289 reflections	(Δ/σ)max = 0.004
177 parameters	Δρmax = 0.57 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3

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

	x	y	z	Uiso*/Ueq
Pd1	0.131986 (15)	0.160063 (16)	0.858658 (8)	0.01466 (5)
Cl1	0.08812 (6)	0.22209 (7)	1.09481 (4)	0.03748 (16)
Cl2	−0.28040 (5)	0.21397 (6)	0.74459 (3)	0.02358 (12)
P1	0.06790 (5)	0.38268 (6)	0.86807 (3)	0.01779 (12)
P2	0.34122 (5)	0.20145 (6)	0.82568 (3)	0.01845 (12)
O1	0.3435 (2)	0.2723 (3)	1.01453 (11)	0.0466 (5)
N1	−0.07272 (17)	0.09998 (19)	0.87006 (9)	0.0178 (4)
H1A	−0.1230	0.1284	0.8323	0.021*
H1B	−0.0746	0.0047	0.8700	0.021*
N2	0.19239 (18)	−0.05356 (19)	0.86717 (10)	0.0204 (4)
H2A	0.1200	−0.1047	0.8796	0.024*
H2B	0.2131	−0.0845	0.8259	0.024*
C1	0.1862 (2)	0.5102 (2)	0.90242 (12)	0.0251 (5)
H1C	0.2421	0.5434	0.8675	0.030*
H1D	0.2445	0.4684	0.9385	0.030*
H1E	0.1365	0.5882	0.9200	0.030*
C2	−0.0048 (3)	0.4576 (3)	0.79215 (13)	0.0314 (6)
H2C	−0.0329	0.5529	0.8005	0.038*
H2D	−0.0837	0.4031	0.7756	0.038*
H2E	0.0625	0.4577	0.7588	0.038*
C3	−0.0585 (2)	0.3924 (3)	0.93015 (13)	0.0277 (5)
H3A	−0.0115	0.3733	0.9743	0.033*
H3B	−0.0913	0.4892	0.9311	0.033*
C4	−0.1815 (2)	0.2986 (3)	0.92226 (13)	0.0282 (5)
H4A	−0.2436	0.3223	0.9569	0.034*
H4B	−0.2299	0.3161	0.8783	0.034*
C5	−0.1464 (2)	0.1462 (2)	0.92778 (12)	0.0214 (5)
H5A	−0.0894	0.1296	0.9695	0.026*
H5B	−0.2305	0.0914	0.9297	0.026*
C6	0.4182 (2)	0.3695 (3)	0.81771 (16)	0.0350 (6)
H6A	0.4335	0.4119	0.8619	0.042*
H6B	0.3579	0.4287	0.7892	0.042*
H6C	0.5049	0.3591	0.7977	0.042*
C7	0.3478 (2)	0.1295 (3)	0.74282 (12)	0.0270 (5)
H7A	0.2862	0.1812	0.7115	0.032*
H7B	0.3204	0.0320	0.7431	0.032*
H7C	0.4404	0.1365	0.7290	0.032*
C8	0.4685 (2)	0.1108 (2)	0.87809 (12)	0.0236 (5)
H8A	0.5570	0.1229	0.8589	0.028*
H8B	0.4751	0.1551	0.9226	0.028*
C9	0.4443 (2)	−0.0439 (3)	0.88725 (13)	0.0264 (5)
H9A	0.4479	−0.0901	0.8435	0.032*
H9B	0.5191	−0.0817	0.9172	0.032*
C10	0.3105 (2)	−0.0805 (3)	0.91562 (12)	0.0270 (5)
H10A	0.3114	−0.1796	0.9282	0.032*
H10B	0.3006	−0.0253	0.9564	0.032*
C11	0.4144 (3)	0.3670 (3)	1.05687 (16)	0.0441 (7)
H11A	0.3583	0.4493	1.0623	0.053*
H11B	0.4984	0.3941	1.0375	0.053*
H11C	0.4361	0.3239	1.1004	0.053*
H01	0.278 (4)	0.251 (4)	1.0322 (19)	0.054 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pd1	0.01377 (8)	0.01199 (8)	0.01851 (9)	0.00047 (6)	0.00314 (5)	−0.00001 (6)
Cl1	0.0297 (3)	0.0185 (3)	0.0644 (5)	−0.0022 (2)	0.0048 (3)	0.0067 (3)
Cl2	0.0218 (2)	0.0230 (3)	0.0259 (3)	−0.0009 (2)	0.0020 (2)	0.0007 (2)
P1	0.0167 (2)	0.0126 (3)	0.0242 (3)	0.00069 (19)	0.0029 (2)	0.0009 (2)
P2	0.0144 (2)	0.0163 (3)	0.0252 (3)	0.0003 (2)	0.0052 (2)	0.0014 (2)
O1	0.0454 (13)	0.0586 (15)	0.0365 (12)	0.0079 (11)	0.0068 (10)	−0.0012 (10)
N1	0.0160 (8)	0.0138 (9)	0.0239 (9)	0.0002 (7)	0.0030 (7)	−0.0004 (7)
N2	0.0172 (8)	0.0165 (10)	0.0280 (10)	0.0014 (7)	0.0052 (7)	0.0005 (8)
C1	0.0253 (11)	0.0202 (12)	0.0295 (13)	0.0000 (9)	−0.0001 (9)	−0.0040 (10)
C2	0.0334 (13)	0.0248 (13)	0.0342 (14)	−0.0014 (10)	−0.0100 (10)	0.0082 (11)
C3	0.0292 (12)	0.0221 (12)	0.0325 (13)	0.0007 (10)	0.0081 (10)	−0.0048 (10)
C4	0.0284 (12)	0.0254 (13)	0.0321 (13)	0.0032 (10)	0.0117 (10)	−0.0020 (10)
C5	0.0193 (10)	0.0216 (12)	0.0244 (11)	−0.0011 (8)	0.0083 (8)	0.0026 (9)
C6	0.0250 (12)	0.0211 (13)	0.0610 (18)	−0.0025 (9)	0.0170 (12)	0.0031 (12)
C7	0.0213 (11)	0.0359 (14)	0.0245 (12)	0.0010 (9)	0.0066 (9)	0.0008 (10)
C8	0.0170 (10)	0.0246 (12)	0.0288 (12)	−0.0001 (8)	0.0001 (9)	0.0004 (10)
C9	0.0208 (10)	0.0247 (13)	0.0330 (13)	0.0046 (9)	−0.0031 (9)	0.0039 (10)
C10	0.0255 (11)	0.0259 (13)	0.0293 (13)	0.0024 (9)	0.0002 (9)	0.0088 (10)
C11	0.0426 (16)	0.0374 (17)	0.0525 (19)	0.0054 (13)	0.0045 (14)	0.0114 (14)

Geometric parameters (Å, º)

Pd1—N1	2.137 (2)	C3—H3A	0.9900
Pd1—N2	2.151 (2)	C3—H3B	0.9900
Pd1—P1	2.2528 (13)	C4—C5	1.514 (3)
Pd1—P2	2.2577 (14)	C4—H4A	0.9900
P1—C2	1.793 (3)	C4—H4B	0.9900
P1—C1	1.802 (2)	C5—H5A	0.9900
P1—C3	1.835 (3)	C5—H5B	0.9900
P2—C6	1.804 (3)	C6—H6A	0.9800
P2—C8	1.809 (2)	C6—H6B	0.9800
P2—C7	1.812 (3)	C6—H6C	0.9800
O1—C11	1.403 (4)	C7—H7A	0.9800
O1—H01	0.79 (4)	C7—H7B	0.9800
N1—C5	1.485 (3)	C7—H7C	0.9800
N1—H1A	0.9200	C8—C9	1.525 (3)
N1—H1B	0.9200	C8—H8A	0.9900
N2—C10	1.489 (3)	C8—H8B	0.9900
N2—H2A	0.9200	C9—C10	1.523 (3)
N2—H2B	0.9200	C9—H9A	0.9900
C1—H1C	0.9800	C9—H9B	0.9900
C1—H1D	0.9800	C10—H10A	0.9900
C1—H1E	0.9800	C10—H10B	0.9900
C2—H2C	0.9800	C11—H11A	0.9800
C2—H2D	0.9800	C11—H11B	0.9800
C2—H2E	0.9800	C11—H11C	0.9800
C3—C4	1.517 (3)
N1—Pd1—N2	89.53 (7)	C5—C4—C3	113.2 (2)
N1—Pd1—P1	88.54 (6)	C5—C4—H4A	108.9
N2—Pd1—P1	170.58 (5)	C3—C4—H4A	108.9
N1—Pd1—P2	167.98 (5)	C5—C4—H4B	108.9
N2—Pd1—P2	86.40 (5)	C3—C4—H4B	108.9
P1—Pd1—P2	97.26 (3)	H4A—C4—H4B	107.7
C2—P1—C1	105.09 (12)	N1—C5—C4	110.96 (18)
C2—P1—C3	107.97 (13)	N1—C5—H5A	109.4
C1—P1—C3	99.24 (12)	C4—C5—H5A	109.4
C2—P1—Pd1	114.27 (10)	N1—C5—H5B	109.4
C1—P1—Pd1	120.31 (9)	C4—C5—H5B	109.4
C3—P1—Pd1	108.47 (8)	H5A—C5—H5B	108.0
C6—P2—C8	101.89 (13)	P2—C6—H6A	109.5
C6—P2—C7	102.62 (13)	P2—C6—H6B	109.5
C8—P2—C7	106.29 (12)	H6A—C6—H6B	109.5
C6—P2—Pd1	126.02 (8)	P2—C6—H6C	109.5
C8—P2—Pd1	110.99 (9)	H6A—C6—H6C	109.5
C7—P2—Pd1	107.40 (8)	H6B—C6—H6C	109.5
C11—O1—H01	107 (3)	P2—C7—H7A	109.5
C5—N1—Pd1	121.82 (14)	P2—C7—H7B	109.5
C5—N1—H1A	106.9	H7A—C7—H7B	109.5
Pd1—N1—H1A	106.9	P2—C7—H7C	109.5
C5—N1—H1B	106.9	H7A—C7—H7C	109.5
Pd1—N1—H1B	106.9	H7B—C7—H7C	109.5
H1A—N1—H1B	106.7	C9—C8—P2	115.78 (16)
C10—N2—Pd1	114.83 (15)	C9—C8—H8A	108.3
C10—N2—H2A	108.6	P2—C8—H8A	108.3
Pd1—N2—H2A	108.6	C9—C8—H8B	108.3
C10—N2—H2B	108.6	P2—C8—H8B	108.3
Pd1—N2—H2B	108.6	H8A—C8—H8B	107.4
H2A—N2—H2B	107.5	C10—C9—C8	114.9 (2)
P1—C1—H1C	109.5	C10—C9—H9A	108.5
P1—C1—H1D	109.5	C8—C9—H9A	108.5
H1C—C1—H1D	109.5	C10—C9—H9B	108.5
P1—C1—H1E	109.5	C8—C9—H9B	108.5
H1C—C1—H1E	109.5	H9A—C9—H9B	107.5
H1D—C1—H1E	109.5	N2—C10—C9	112.2 (2)
P1—C2—H2C	109.5	N2—C10—H10A	109.2
P1—C2—H2D	109.5	C9—C10—H10A	109.2
H2C—C2—H2D	109.5	N2—C10—H10B	109.2
P1—C2—H2E	109.5	C9—C10—H10B	109.2
H2C—C2—H2E	109.5	H10A—C10—H10B	107.9
H2D—C2—H2E	109.5	O1—C11—H11A	109.5
C4—C3—P1	118.74 (18)	O1—C11—H11B	109.5
C4—C3—H3A	107.6	H11A—C11—H11B	109.5
P1—C3—H3A	107.6	O1—C11—H11C	109.5
C4—C3—H3B	107.6	H11A—C11—H11C	109.5
P1—C3—H3B	107.6	H11B—C11—H11C	109.5
H3A—C3—H3B	107.1
N1—Pd1—P1—C2	−82.88 (11)	P1—Pd1—N1—C5	−54.23 (15)
P2—Pd1—P1—C2	86.55 (10)	P2—Pd1—N1—C5	−173.37 (18)
N1—Pd1—P1—C1	150.65 (11)	N1—Pd1—N2—C10	−130.64 (16)
P2—Pd1—P1—C1	−39.91 (10)	P2—Pd1—N2—C10	60.67 (15)
N1—Pd1—P1—C3	37.61 (10)	C2—P1—C3—C4	71.4 (2)
P2—Pd1—P1—C3	−152.95 (9)	C1—P1—C3—C4	−179.3 (2)
N1—Pd1—P2—C6	121.7 (3)	Pd1—P1—C3—C4	−52.9 (2)
N2—Pd1—P2—C6	−167.89 (14)	P1—C3—C4—C5	63.9 (3)
P1—Pd1—P2—C6	3.39 (13)	Pd1—N1—C5—C4	72.0 (2)
N1—Pd1—P2—C8	−114.8 (3)	C3—C4—C5—N1	−68.3 (3)
N2—Pd1—P2—C8	−44.40 (10)	C6—P2—C8—C9	−171.83 (19)
P1—Pd1—P2—C8	126.88 (9)	C7—P2—C8—C9	−64.7 (2)
N1—Pd1—P2—C7	1.0 (3)	Pd1—P2—C8—C9	51.7 (2)
N2—Pd1—P2—C7	71.39 (11)	P2—C8—C9—C10	−57.3 (3)
P1—Pd1—P2—C7	−117.33 (9)	Pd1—N2—C10—C9	−78.6 (2)
N2—Pd1—N1—C5	116.55 (16)	C8—C9—C10—N2	70.1 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Cl2	0.92	2.41	3.325 (3)	171
N1—H1B···Cl1^i	0.92	2.31	3.195 (3)	162
N2—H2A···Cl1^i	0.92	2.44	3.356 (3)	174
N2—H2B···Cl2^ii	0.92	2.53	3.339 (3)	147
O1—H01···Cl1	0.79 (4)	2.36 (4)	3.138 (3)	171 (3)

Symmetry codes: (i) −x, −y, −z+2; (ii) −x, y−1/2, −z+3/2.