Crystal structure of cis-[Ru(bpy)2{PMe(o-tol)2}Cl+][ClO-4]: Steric effects in some PMen(o-tol)3-n (n = 1-3) derivatives of ruthenium(II)

Article abstract of DOI:10.1023/A:1009585713855

The complex cis-[Ru(bpy)₂{PMe(o-tol)₂}Cl⁺][ClO^-₄] crystallizes in space group P2₁/c with a = 9.375(2) A, b = 22.019(7) A, c = 16.153(4) A, β= 90.83(2)°, V = 3333.9(16) A³ and D(calc'd) = 1.547 g/cm³ for Z = 4. The Ru-PMe(o-tol)₂ bond length of 2.357(3) A is significantly longer than distances of Ru-PMe₂(o-tol) = 2.324(2) A and Ru-PMe₃ = 2.310(2) A in analogous complexes. The corresponding Ru-P(o-tol)₃ complex has eluded synthesis, probably due to steric hindrance.

Full text of DOI:10.1023/A:1009585713855

Journal of Chemical Crystallography, Vol. 30, No. 1, 2000
Crystal structure of cis-[Ru(bpy)2͕PMe(o-tol)2͖Cl؉][ClO؊4 ]:
Steric effects in some PMen(o-tol)3؊n (n ؍ 1-3) derivatives
of ruthenium(II)
Melvyn Rowen Churchill,(1)* David George Churchill,(1,2) My Hang Vo Huynh,(1) and
Kenneth J. Takeuchi(1)
Received December 19, 1999
The complex cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ][ClO4Ϫ] crystallizes in space group P21/c with
3
˚
˚
˚
˚
a ϭ 9.375(2) A, b ϭ 22.019(7) A, c ϭ 16.153(4) A, ͱ ϭ 90.83(2)Њ, V ϭ 3333.9(16) A and
3
˚
D(calc’d) ϭ 1.547 g/cm for Z ϭ 4. The Ru-PMe(o-tol)2 bond length of 2.357(3) A is
significantly longer than distances of Ru-PMe2(o-tol) ϭ 2.324(2) A and Ru-PMe3 ϭ 2.310(2)
A in analogous complexes. The corresponding Ru-P(o-tol)3 complex has eluded synthesis,
˚
˚
probably due to steric hindrance.
KEY WORDS: Steric effects; ruthenium(II).
Introduction
of I2 were stirred together for 2 h to form Ͱ-bromo-
magnesium toluene. P(CH3)Cl2 (1.71 g, 14.6 mmol)
We have previously reported the crystal struc-
was added slowly and the solution was stirred for a
further 2 h.
tures of cis-[Ru(bpy)2(PMe3)2Clϩ][ClO4Ϫ]1 and cis-
[Ru(bpy)2͕PMe2(o-tol)͖Clϩ][ClO4Ϫ]1 and now report
the crystal structure of the more hindered species cis-
[Ru(bpy)2͕PMe(o-tol)2Clϩ][ClO4Ϫ]. We have been un-
able to synthesize the tri-(o-tolyl)phosphine deriva-
tive cis-[Ru(bpy)2͕P(o-tol)3͖Clϩ][ClO4Ϫ], which would
complete the series; this is, presumably, due to ste-
ric hindrance.
The solution was washed with 10% aqueous
NH4Cl (3 ϫ 25 mL) and the compound was extracted
with methylene chloride and reduced to dryness on
a rotary evaporator. The compound was purified by
column chromatography on basic alumina with hex-
ane being used as the eluent. The first band that
eluted from the column was reduced to dryness using
a rotary evaporator, producing 2.02 g of an off-white
1
solid (60.7% yield), which was characterized by H
Experimental
NMR (CDCl3): ͳ 7.2 (m 8HUC6H4CH3), 2.4 (s,
6H,UC6H4CH3), 1.5 (d, 3H,UCH3).
Synthesis of PMe(o-tol)2
In an inert atmosphere glovebox, Ͱ-bromoto-
luene (5 g, 29.2 mmol), magnesium (0.711 g, 29.3
mmol), tetrahydrofuran (30 mL) and a small crystal
Synthesis of cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ][ClO4Ϫ]
This synthesis is based upon the method of Mar-
mion and Takeuchi.2 Ru(bpy)2Cl2·2H2O (521 mg, 1
mmol) and PMe(o-tol)2 (228 mg, 1 mmol) were added
to 100 mL of a nitrogen-deaerated ethanol-water mix-
ture (80/20 v/v) and refluxed for 6 h. The solution
(1) Department of Chemistry, University at Buffalo, The State Uni-
versity of New York, Buffalo, New York 14260-3000.
(2) Present address: Department of Chemistry, Columbia Univer-
sity, New York, New York 10027.
* To whom correspondence should be addressed.
17
1074-1542/00/0100-0017$18.00/0  2000 Plenum Publishing Corporation

18
Churchill, Churchill, Huynh, and Takeuchi
Table 1. Data for the X-Ray Diffraction Study
was reduced to dryness; 50 mL of water and an excess
of sodium perchlorate were added to precipitate the
perchlorate salt. The red solid was collected by suc-
tion filtration, air-dried and then dried in a vacuum
oven overnight, without heating. Purification was
achieved by column chromatography on basic alu-
mina utilizing 1% methanol in methylene chloride as
an eluent. The first red band to elute was collected
and the solvent removed with a rotary evaporator.
The product was then redissolved in a minimum
amount of methylene chloride and added dropwise
into hexane. The microcrystalline product was col-
lected by suction-filtration, air-dried and dried in a
vacuum oven overnight.
Compound
cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ]
[ClO4Ϫ]
CCDC deposit no.
Color/shape
CCDC-1003/5727
Red/plate
Chemical formula
Formula weight
Temperature, K
Crystal system
C35H33Cl2N4O4PRu
776.6
295
Monoclinic
Space group
Unit cell dimensions
P21/c(No. 14)
a ϭ 9.375(2) A
˚
˚
b ϭ 22.019(7) A
˚
c ϭ 16.153(4) A
ͱ ϭ 90.83(2)
3333.9(16)
3
˚
Volume, A
Z
4
Yield 0.582
g (75.4%). Anal. Calcd. for
Density (calculated),
1.547
Mg/m3
C35H33Cl2N4O4PRu: C 54.13, H 4.28%. Found: C 53.98,
H 4.34%. UV-vis data (CH2Cl2) ␭max, nm (␧, MϪ1 cmϪ1):
476 (7300); 339 (7300); 295 (46000).
Crystals suitable for an x-ray study were pre-
pared by recrystallization from CH2Cl2/toluene.
Absorption coefficient,
mmϪ1
F (000)
Diffractometer/scan
2␪ range, deg./radiation
0.713
1584
Siemens R3m/2␪–␪
4.5 to 35.0/MoKͰ(␭
0.71073A)
4629
2117 (Rint ϭ 2.10%)/1495 [I Ͼ
2␴(I)]
1495/0/249
˚
Reflections measured
Independent/observed re-
flection
Data/retraints/parameters
Goodness-of-fit
Attempted Synthesis of cis-[Ru(bpy)2͕P(o-tol)3͖Clϩ]
[ClOϪ4 ]
1.42
Final R indices [I Ͼ 2␴(I)]
R indices (all data)
Largest diff. peak, hole
R1 ϭ 0.0430, wR2 ϭ 0.0361
R1 ϭ 0.0731, wR2 ϭ 0.0405
ϩ0.39, Ϫ0.33
Attempts to synthesize this species from [Ru
(bpy)2Cl2]·2H2O and P(o-tol)3 , in a manner analogous
to that described above, were not successful.3a
Caution: Perchlorate salts of metal salts of or-
ganic ligands are potentially explosive. (See also de-
tailed caution in ref 1.)
Ϫ
3
˚
(e /A )
‘‘observed’’ with I Ͼ 2␴(I). Refinement led to R1 ϭ
0.0430 for the observed data and R1 ϭ 0.0731 for all
2117 unique data. The limitations of the data set
prompted us to refine anisotropically only the
RuN4ClP portion of the cation and atoms of the
[ClOϪ4 ] anion. Carbon atoms were refined with iso-
tropic thermal parameters and hydrogen atoms were
Crystallographic studies
Data were collected as described previously;4 ex-
perimental data are compiled in Table 1.
The crystals grew as thin plates; the largest we
were able to produce (0.3 ϫ 0.2 ϫ 0.05 mm, volume
approximately 3 ϫ 10Ϫ3 mm3) was used for the single-
crystal x-ray diffraction study but gave rise to a rather
weak diffraction pattern. Data were collected with a
Siemens R3m/V diffractometer. The Laue symmetry
(2/m) and the systematic absences (h0l for l ϭ 2nϩ1
and 0k0 for k ϭ 2nϩ1) uniquely define the ubiquitous
centrosymmetric monoclinic space group P21/c. Data
were collected for one hemisphere of reciprocal space
(ϩh, Ϯk, Ϯl) to the limit of observable reflections
(2␪ ϭ 35Њ; Mo KͰ radiation). The 4629 measured
reflections were corrected for absorption and Lp fac-
tors and were reduced to a unique set of 2117 reflec-
tions (Rint ϭ 2.10%) of which 1495 were considered
included in calculated positions with d(CUH) ϭ
5
˚
0.96A. All calculations were performed under the
SHELXTL PLUS (Release 4.11 (VMS))6 set of com-
puter programs. The analytical scattering factors for
neutral atoms7a were corrected for both the real and
imaginary components of anomalous dispersion.7b
Discussion
The labeling of atoms is shown in Fig. 1, while
the packing of cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ] cations
and [ClOϪ4 ] anions is illustrated in Fig. 2. The crystal

cis-[Ru(bpy)2͕PMe(o-tol)2͖Cl؉] [ClO4؊]
19
tropic thermal parameters are given in Table 2. Se-
lected interatomic distances and angles are provided
in Table 3. The central ruthenium(II) cation has no
elements of symmetry (point group C1) and is chiral;
the crystal as a whole contains an ordered racemic
Table 2. Final Atomic Coordinates (ϫ104) and Equivalent Iso-
2
tropic Thermal Parameters (A ϫ 103) for cis-[Ru(bpy)2͕PMe
˚
(o-tol)2͖Clϩ][ClO4Ϫ]
x
y
z
U(eq)
(A) Atoms in ruthenium(II) cation
Ru(1)
P(1)
125(1)
1011(3)
Ϫ622(3)
Ϫ640(10)
1950(9)
Ϫ1746(8)
417(9)
2081(1)
2993(1)
2519(1)
1265(3)
1737(4)
2272(3)
1621(3)
985(5)
451(5)
228(5)
505(5)
1036(5)
1241(5)
988(5)
1244(5)
1726(5)
1949(5)
2004(5)
2125(5)
2529(5)
2785(5)
2640(5)
1610(5)
1226(5)
875(5)
526(1)
1098(2)
Ϫ787(2)
17(5)
Ϫ39(5)
1133(5)
1609(5)
Ϫ491(6)
Ϫ914(6)
Ϫ806(6)
Ϫ289(6)
134(7)
Ϫ529(6)
Ϫ973(6)
Ϫ932(7)
Ϫ415(7)
23(6)
1880(7)
2392(6)
2097(7)
1337(6)
861(6)
38(1)
43(1)
60(1)
43(4)
42(4)
33(3)
33(3)
39(3)
47(3)
50(3)
52(3)
48(3)
37(3)
54(4)
63(4)
61(4)
47(3)
39(3)
53(3)
64(4)
54(3)
48(3)
35(3)
50(3)
62(4)
51(3)
47(3)
44(3)
59(4)
69(4)
79(4)
69(4)
51(3)
78(4)
41(3)
54(4)
66(4)
75(4)
74(4)
54(4)
75(4)
54(3)
Cl(1)
N(11)
N(21)
N(31)
N(41)
C(12)
C(13)
C(14)
C(15)
C(16)
C(22)
C(23)
C(24)
C(25)
C(26)
C(32)
C(33)
C(34)
C(35)
C(36)
C(42)
C(43)
C(44)
C(45)
C(46)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
C(57)
C(61)
C(62)
C(63)
C(64)
C(65)
C(66)
C(67)
C(71)
308(11)
Fig. 1. Labeling of atoms for cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ]
[ClO4Ϫ]. This diagram shows 30% probability envelopes for thermal
vibrations, with hydrogen atoms artificially reduced.
Ϫ123(11)
Ϫ1449(11)
Ϫ2378(11)
Ϫ1935(13)
1707(11)
2835(12)
4144(13)
4402(12)
3271(12)
Ϫ1875(10)
Ϫ3040(11)
Ϫ4063(12)
Ϫ3967(11)
Ϫ2791(11)
Ϫ702(12)
Ϫ724(11)
430(12)
1598(12)
1580(12)
2267(11)
2951(12)
3990(12)
4304(13)
3573(12)
2534(11)
2678(12)
Ϫ363(11)
Ϫ1048(12)
Ϫ2143(12)
Ϫ2553(13)
Ϫ1953(13)
Ϫ831(11)
Ϫ671(12)
2033(10)
structure is stabilized by a series of weak CUHиииO
hydrogen bonds involving the aromatic CUH moie-
ties of o-tolyl rings and perchlorate anions.
Final atomic coordinates and equivalent iso-
2127(7)
2818(6)
2988(7)
2495(7)
1815(7)
528(6)
908(5)
1275(5)
3464(5)
3984(5)
4263(5)
4059(6)
3571(5)
3286(5)
4272(5)
3527(4)
3953(5)
4307(5)
4209(5)
3774(5)
3434(5)
4070(5)
2809(5)
850(7)
367(7)
Ϫ425(8)
Ϫ747(8)
Ϫ291(6)
1670(7)
1479(6)
973(7)
1319(7)
2109(8)
2592(8)
2299(7)
87(7)
2040(5)
(B) Atoms in perchlorate anion
C1(2A)
O(1A)
O(2A)
O(3A)
O(4A)
4470(4)
5286(10)
2993(9)
4707(11)
4878(10)
Ϫ559(2)
Ϫ50(5)
Ϫ436(3)
Ϫ716(5)
Ϫ1041(5)
Ϫ1886(2)
Ϫ1704(8)
Ϫ1784(5)
Ϫ2695(7)
Ϫ1380(7)
59(2)
139(5)
78(4)
146(6)
142(6)
Fig. 2. Packing diagram for cis-[Ru(bpy)2͕PMe(o-tol)2͖Clϩ]
[ClO4Ϫ], projected on (100). (The c-axis is horizontal and the b-
axis is vertical.) Note the CUHиииO interactions.

20
Churchill, Churchill, Huynh, and Takeuchi
˚
Table 3. Selected Interatomic Distances (A) and Angles (Њ) for cis-[Ru(bpy)2͕PMe
(o-tol)2͖Clϩ][ClO4Ϫ]
Ru(1)UP(1)
Ru(1)UN(11)
Ru(1)UN(31)
P(1)UC(51)
P(1)UC(71)
N(11)UC(16)
N(21)UC(26)
N(31)UC(36)
N(41)UC(46)
C(12)UC(22)
C(14)UC(15)
C(22)UC(23)
C(24)UC(25)
C(32)UC(33)
C(33)UC(34)
C(35)UC(36)
C(43)UC(44)
C(45)UC(46)
C(51)UC(56)
C(52)UC(57)
C(54)UC(55)
C(61)UC(62)
C(62)UC(63)
C(63)UC(64)
2.357(3)
2.098(8)
2.065(8)
1.828(11)
1.831(9)
Ru(1)UC1(1)
Ru(1)UN(21)
Ru(1)UN(41)
P(1)UC(61)
2.424(3)
2.093(8)
2.034(7)
1.855(10)
1.366(13)
1.366(13)
1.352(13)
1.352(14)
1.417(14)
1.350(15)
1.413(15)
1.351(16)
1.375(15)
1.452(15)
1.354(15)
1.400(15)
1.365(16)
1.409(15)
1.398(16)
1.392(17)
1.380(16)
1.416(15)
1.503(15)
1.353(17)
1.385(11)
1.372(11)
N(11)UC(12)
N(21)UC(22)
N(31)UC(32)
N(41)UC(42)
C(12)UC(13)
C(13)UC(14)
C(15)UC(16)
C(23)UC(24)
C(25)UC(26)
C(32)UC(42)
C(34)UC(35)
C(42)UC(43)
C(44)UC(45)
C(51)UC(52)
C(52)UC(53)
C(53)UC(54)
C(55)UC(56)
C(61)UC(66)
C(62)UC(67)
C(64)UC(65)
C1(2A)UO(1A)
C1(2A)UO(3A)
1.332(14)
1.326(14)
1.340(13)
1.368(14)
1.429(15)
1.360(15)
1.401(15)
1.369(15)
1.405(14)
1.389(15)
1.390(15)
1.354(15)
1.364(15)
1.405(14)
1.493(16)
1.373(17)
1.395(15)
1.411(16)
1.354(17)
1.381(16)
1.423(9)
C(65)UC(66)
C1(2A)UO(2A)
C1(2A)UO(4A)
P(1)URu(1)UCl(1)
Cl(1)URu(1)UN(11)
Cl(1)URu(1)UN(21)
P(1)URu(1)UN(31)
N(11)URu(1)UN(31)
P(1)URu(1)UN(41)
N(11)URu(1)UN(41)
N(31)URu(1)UN(41)
Ru(1)UP(1)UC(61)
Ru(1)UP(1)UC(71)
C(61)UP(1)UC(71)
1.390(11)
95.7(1)
P(1)URu(1)UN(11)
179.3(3)
101.2(2)
78.2(3)
84.5(2)
89.4(2)
86.4(2)
94.2(3)
92.6(2)
87.3(3)
78.4(3)
115.3(3)
108.3(3)
102.9(4)
P(1)URu(1)UN(21)
N(11)URu(1)UN(21)
Cl(1)URu(1)UN(31)
N(21)URu(1)UN(31)
Cl(1)URu(1)UN(41)
N(21)URu(1)UN(41)
Ru(1)UP(1)UC(51)
C(51)UP(1)UC(61)
C(51)UP(1)UC(71)
95.6(2)
170.5(3)
169.4(2)
95.4(3)
120.8(3)
105.3(5)
102.2(5)
array of the two enantiomeric forms of this cation.
The immediate coordination geometry about the
metal atom may be regarded as a rather distorted
octahedral arrangement. The bipyridyl ligands are
associated with the reduced bite angles N(11)U
Ru(1)UN(21) ϭ 78.2(3)Њ and N(31)URu(1)UN(41)
ϭ 78.4(3)Њ. The PMe(o-tol)2 ligand is trans to one
the PMe(o-tol)2 ligand. Angles to the bulky o-tolyl
groups (ЄRu(1)UP(1)UC(51) ϭ 120.8(3)Њ and
ЄRu(1)UP(1)UC(61) ϭ 115.3(3)Њ) are substantially
larger than those to the sterically undemanding
methyl group (ЄRu(1)UP(1)UC(71) ϭ 108.3(3)Њ).
The CUPUC angles behave analogously, albeit with
smaller perturbations, with ЄC(51)UP(1)UC(61) ϭ
105.3(5)Њ as compared to ЄC(51)UP(1)UC(71) ϭ
102.2(5)Њ and ЄC(61)UP(1)UC(71) ϭ 102.9(4)Њ.
The RuUP and RuUN bond lengths in the pres-
ent complex are compared to those in related RuU
PMen(o-tol)3Ϫn (n ϭ 1-3) complexes and to the related
RuUPPhn(o-tol)3Ϫn (n ϭ 1-3)complexes8–10 in Table 4.
As can clearly be seen, the RuUP distances increase
steadily along the series RuUPMe3, RuUPMe2(o-
nitrogen atom, with ЄP(1)URu(1)UN(11)
ϭ
179.3(3)Њ and the other trans angles are reduced to
N(21)URu(1)UN(31) ϭ 170.5(3)Њ and N(41)U
Ru(1)UCl(1) ϭ 169.4(2)Њ.
The RuUPMe(o-tol)2 bond length is given by
˚
Ru(1)UP(1)
ϭ
2.357(3)
A
and the trans
˚
Ru(1)UN(11) distance is 2.098(8) A. The RuU
PUC(ipso) angles reflect the asymmetric nature of

cis-[Ru(bpy)2͕PMe(o-tol)2͖Cl؉] [ClO4؊]
21
Table 4. Ligand Cone Angles (␪Њ)a, RuUP and the trans RuUN distances and cisUPURuUCl angles in some
cis-[Ru(bpy)2(phosphine)Clϩ] cations
Cation
␪
RuUP
trans-RuUN
ЄPURuUCl
Ref
cis-[Ru(bpy)2(PMe3)Clϩ]
118
141
169
145
161
178
2.310(2)
2.324(2)
2.357(3)
2.328(1)
2.360(3)
2.382(2)
2.112(6)
2.124(5)
2.098(8)
2.109(4)
2.092(7)
2.088(7)
86.4(1)
90.1(1)
95.7(1)
93.8(1)
94.1(1)
97.3(1)
1
1
cis-[Ru(bpy)2(PMe2(o-tol)͖Clϩ]
cis-[Ru(bpy)2(PMe(o-tol)2͖Clϩ]
cis-[Ru(bpy)(PPh3)Clϩ]
This work
8
9
10
cis-[Ru(bpy)͕PPh2(o-tol)͖Clϩ]
cis-[Ru(bpy)͕PPh(o-tol)2͖Clϩ]
a Cone angle of phosphine ligand (see refs 3b and 11).
tol), RuUPMe(o-tol)2 (for which the phosphine cone
angles are respectively 118Њ, 143Њ, and 169Њ)11 and
along the series RuUPPh3, RuUPPh2(o-tol), RuU
PPh(o-tol)2 (for which the ligand cone angles are
145Њ, 161Њ, and 178Њ). The analogous complex with a
RuUP(o-tol)3 ligand (cone angle 194Њ) has eluded
synthesis, but, if it ever could be prepared, it would be
expected to have an unusually long RuUP linkage.
The steric, rather than electronic, cause of these
results is confirmed by a study of the cis-PURuUCl
angles in these two series’ of compounds. This angle
expands steadily along each series: 86.4(1)Њ for
ЄClURuUPMe3, 90.1(1)Њ for ЄClURuUPMe2(o-
tol), 95.7(1)Њ for ЄClURuUPMe(o-tol)2; 93.8(1)Њ
for ЄClURuUPPh3, 94.1(1)Њ for ЄClURuU
PPh2(o-tol) and 97.3(1)Њ for ЄClURuUPPh(o-tol)2.
This bond angle correlates strongly with ␪, the cone
angle of the phosphine ligand.
Acknowledgments
Purchase of the Siemens R3m/V diffractometer
was made possible by Grant 89-13733 from the Chem-
ical Instrumentation Program of the National Sci-
ence Foundation.
References
1. Churchill, M.R.; Krajkowski, L.M.; Huynh, M.H.V.; Takeuchi,
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8. Churchill, M.R.; Krajkowski, L.M.; Huynh, M.H.V.; Takeuchi,
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9. Churchill, M.R.; Krajkowski, L.M.; Huynh, M.H.V.; Takeuchi,
K.J. J. Chem. Crystallogr. 1996, 26, 111.
Although studies on the RuUPPhn(o-tol)3Ϫn de-
rivatives (n ϭ 1-3) have been published previously,
all three structures contained unusual combinations
of solvent molecules of crystallization.8–10 The present
RuUPMen(o-tol)3Ϫn derivatives confirm our findings
for a series of complexes uncontaminated by solvent
of crystallization.
10. Churchill, M.R.; Krajkowski, L.M.; Huynh, M.H.V.; Takeuchi,
K.J. J. Chem. Crystallogr. 1996, 26, 67.
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