Tetra­kis[μ-N-(2,4,6-trimethyl­phen­yl)acetamidato]-κ4N:O;κ4O:N-bis­[(benzo­nitrile-κN)rhodium(II)](Rh—Rh)

Eagle, C.T.; Kpogo, K.K.; Zink, L.C.; Smith, A.E.

doi:10.1107/S1600536812024518

metal-organic compounds

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ISSN: 2056-9890

Volume 68| Part 7| July 2012| Page m877

https://doi.org/10.1107/S1600536812024518

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Tetrakis[μ-N-(2,4,6-trimethylphenyl)acetamidato]-κ⁴N:O;κ⁴O:N-bis[(benzonitrile-κN)rhodium(II)](Rh—Rh)

Cassandra T. Eagle,^a ^* Kenneth K. Kpogo,^a Landon C. Zink ^a and Albert E. Smith ^a

^aChemistry Department, East Tennessee State University, PO Box 70695, Johnson City, Tennessee, TN 37614, USA
^*Correspondence e-mail: eaglec@etsu.edu

(Received 2 March 2012; accepted 29 May 2012; online 13 June 2012)

The title structure, [Rh₂(C₁₁H₁₄NO)₄(C₇H₅N)₂], contains a dinuclear Rh complex of point symmetry -4 with an Rh—Rh unit and two benzonitrile ligands located in special positions along the twofold axis passing through -4. Four symmetry-equivalent mesitylacetamidate ligands bridge the Rh—Rh unit. Thus, each Rh^II atom has an approximately octahedral coordination by one Rh [Rh—Rh = 2.4290 (6) Å], two acetamidate O atoms trans to each other [Rh—O = 2.044 (3) Å], two acetamidate N atoms trans to each other [Rh—N = 2.091 (4) Å], and a benzonitrile N atom trans to Rh [Rh—N = 2.222 (3) Å]. The structure is held together by weak van der Waals forces.

Related literature

For the synthesis and crystal structure of a related compound, see: Eagle et al. (2000 ).

Experimental

Crystal data

[Rh₂(C₁₁H₁₄NO)₄(C₇H₅N)₂]
M_r = 1117.01
Tetragonal, $[P \overline 42_1 c ]$
a = 10.9928 (19) Å
c = 21.4549 (19) Å
V = 2592.6 (7) Å³
Z = 2
Mo Kα radiation
μ = 0.69 mm⁻¹
T = 298 K
0.18 × 0.13 × 0.07 mm

Data collection

Rigaku XtaLAB mini diffractometer
Absorption correction: multi-scan (REQAB; Jacobson, 1998 ) T_min = 0.618, T_max = 0.953
48863 measured reflections
2969 independent reflections
1950 reflections with I > 2σ(I)
R_int = 0.105

Refinement

R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.074
S = 1.03
2969 reflections
165 parameters
H-atom parameters constrained
Δρ_max = 0.64 e Å⁻³
Δρ_min = −0.71 e Å⁻³
Absolute structure: Flack (1983 ), 1275 Friedel pairs
Flack parameter: −0.03 (5)

Data collection: CrystalClear (Rigaku, 2011 ); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: CrystalStructure (Rigaku, 2010 ); software used to prepare material for publication: CrystalStructure.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536812024518/qk2033sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812024518/qk2033Isup2.hkl

checkCIF report

Comment top

The title compound, a dinuclear Rh complex with a Rh—Rh bond and four equivalent bridging ligands (Fig. 1), is the mesitylacetamidato analogue of the previously published phenylacetamidato compound Rh₂[N(C₆H₅)C(O)CH₃]₄^.2NCC₆H₅ (Eagle et al., 2000), both having the 2,2-trans stereochemistry in the complex-core, which is one out of four possible isomers. The highest molecular symmetry that these two complexes can adopt is 42m with two mirror planes trough the acetamidate chelate ring pairs and twofold axes in bisecting directions. While in the crystal structure of Rh₂[N(C₆H₅)C(O)CH₃]₄^.2NCC₆H₅ the Rh complex has point symmetry 1 and adopts a considerably twisted conformation in the core and one benzonitrile ligand (significantly bent off from the Rh—Rh axis), the complex of the title structure is more regular and has 4 symmetry, not far from 42m if the axial benzonitrile ligands are disregarded. Thus, in Rh₂[N(C₆H₅)C(O)CH₃]₄^.2NCC₆H₅ the four N—Rh—Rh—O dihedral angles range from 9.03 to 11.89°, while in the title compound the same torsion angle is only 1.12 (9)°. The inclination angle of the mesityl phenyl rings to the Rh—Rh-bond is in the title compound about 26°, while about 34° in the phenylacetamidato complex. This makes the space between adjacent mesityl rings narrow and forces the benzonitrile phenyl rings into a more inclined orientation than in Rh₂[N(C₆H₅)C(O)CH₃]₄^.2NCC₆H₅, where they are not far from perpendicular to the acetamidinato phenyl rings. A packing diagram of the structure is shown in Fig. 2. It reveals that the molecules are held together by weak Van der Waals forces, which is not surprising in view of the 16 CH₃ groups on the outer surface of the Rh complex.

Related literature top

For the synthesis and crystal structure of a related compound, see: Eagle et al. (2000).

Experimental top

Approximately 10 mg of 2,2-trans-tetrakis[µ-(N-{2,4,6-trimethylphenyl}acetamidato-κN:κO)]dirhodium(II), synthesized by adapting the procedure described by Eagle et al. (2000), was dissolved in 5 mL of dichloromethane forming a green solution. Approximately 2.29 µL of benzonitrile was added to the solution causing the color to become blue. Crystals of the title compound were obtained using a vapor diffusion technique with acetonitrile for a week. The crystal was measured at 298 K on a Rigaku XtaLAB mini diffractometer.

Structure description top

For the synthesis and crystal structure of a related compound, see: Eagle et al. (2000).

Computing details top

Data collection: CrystalClear (Rigaku, 2011); cell refinement: CrystalClear (Rigaku, 2011); data reduction: CrystalClear (Rigaku, 2011); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: CrystalStructure (Rigaku, 2010); software used to prepare material for publication: CrystalStructure (Rigaku, 2010).

Figures top

	Fig. 1. The molecular structure of the title compound showing displacement ellipsoids at the 30% probability level. Hydrogen atoms are shown as small spheres.
	Fig. 2. Packing diagram of the title structure viewed along the a-axis. H-atoms omitted for clarity.

Tetrakis[µ-N-(2,4,6-trimethylphenyl)acetamidato]- κ⁴N:O;κ⁴O:N-bis[(benzonitrile- κN)rhodium(II)](Rh—Rh) top

Crystal data top

[Rh₂(C₁₁H₁₄NO)₄(C₇H₅N)₂]	D_x = 1.431 Mg m⁻³
M_r = 1117.01	Mo Kα radiation, λ = 0.71075 Å
Tetragonal, P42₁c	Cell parameters from 32577 reflections
Hall symbol: P -4 2n	θ = 3.2–27.7°
a = 10.9928 (19) Å	µ = 0.69 mm⁻¹
c = 21.4549 (19) Å	T = 298 K
V = 2592.6 (7) Å³	Prism, blue
Z = 2	0.18 × 0.13 × 0.07 mm
F(000) = 1156.00

Data collection top

Rigaku XtaLAB mini diffractometer	2969 independent reflections
Radiation source: fine-focus sealed tube	1950 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.105
Detector resolution: 6.827 pixels mm^-1	θ_max = 27.5°
ω scans	h = −14→14
Absorption correction: multi-scan (REQAB; Jacobson, 1998)	k = −14→14
T_min = 0.618, T_max = 0.953	l = −27→27
48863 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.074	w = 1/[σ²(F_o²) + (0.0213P)² + 2.1713P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.003
2969 reflections	Δρ_max = 0.64 e Å⁻³
165 parameters	Δρ_min = −0.71 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 1275 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.03 (5)

Crystal data top

[Rh₂(C₁₁H₁₄NO)₄(C₇H₅N)₂]	Z = 2
M_r = 1117.01	Mo Kα radiation
Tetragonal, P42₁c	µ = 0.69 mm⁻¹
a = 10.9928 (19) Å	T = 298 K
c = 21.4549 (19) Å	0.18 × 0.13 × 0.07 mm
V = 2592.6 (7) Å³

Data collection top

Rigaku XtaLAB mini diffractometer	2969 independent reflections
Absorption correction: multi-scan (REQAB; Jacobson, 1998)	1950 reflections with I > 2σ(I)
T_min = 0.618, T_max = 0.953	R_int = 0.105
48863 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.074	Δρ_max = 0.64 e Å⁻³
S = 1.03	Δρ_min = −0.71 e Å⁻³
2969 reflections	Absolute structure: Flack (1983), 1275 Friedel pairs
165 parameters	Absolute structure parameter: −0.03 (5)
0 restraints

Special details top

Refinement. Refinement was performed using all reflections. The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Rh1	0.5000	0.5000	0.556606 (14)	0.03097 (10)
O1	0.6695 (3)	0.4236 (3)	0.44533 (15)	0.0342 (8)
N1	0.5000	0.5000	0.66016 (16)	0.0443 (9)
N2	0.6716 (3)	0.4187 (3)	0.55161 (19)	0.0349 (10)
C1	0.5000	0.5000	0.7117 (2)	0.0490 (12)
C2	0.5000	0.5000	0.7799 (2)	0.0477 (11)
C3	0.5590 (5)	0.4097 (5)	0.8123 (2)	0.0669 (16)
H3	0.6002	0.3484	0.7913	0.080*
C4	0.5561 (7)	0.4115 (6)	0.8766 (2)	0.100 (2)
H4	0.5943	0.3493	0.8986	0.119*
C5	0.5000	0.5000	0.9084 (3)	0.118 (3)
H5	0.5000	0.5000	0.9517	0.141*
C6	0.7216 (3)	0.3988 (3)	0.4977 (3)	0.0376 (8)
C7	0.8472 (3)	0.3448 (4)	0.4909 (2)	0.0481 (11)
H7A	0.8635	0.3293	0.4476	0.072*
H7B	0.8516	0.2699	0.5138	0.072*
H7C	0.9064	0.4009	0.5069	0.072*
C8	0.7316 (4)	0.3860 (4)	0.60846 (17)	0.0350 (9)
C9	0.7176 (4)	0.2700 (4)	0.63427 (19)	0.0447 (10)
C10	0.7689 (4)	0.2470 (5)	0.6922 (2)	0.0538 (12)
H10	0.7613	0.1693	0.7089	0.065*
C11	0.8302 (5)	0.3333 (6)	0.7260 (2)	0.0585 (15)
C12	0.8474 (4)	0.4461 (5)	0.6986 (2)	0.0473 (12)
H12	0.8909	0.5050	0.7203	0.057*
C13	0.8015 (4)	0.4747 (4)	0.63927 (18)	0.0416 (11)
C14	0.6525 (5)	0.1711 (4)	0.5992 (2)	0.0578 (14)
H14A	0.6895	0.1608	0.5590	0.087*
H14B	0.5685	0.1931	0.5940	0.087*
H14C	0.6578	0.0963	0.6221	0.087*
C15	0.8820 (5)	0.3097 (6)	0.7897 (2)	0.080 (2)
H15A	0.8394	0.2431	0.8088	0.120*
H15B	0.8729	0.3812	0.8150	0.120*
H15C	0.9667	0.2897	0.7861	0.120*
C16	0.8312 (5)	0.5947 (4)	0.6108 (2)	0.0585 (15)
H16A	0.7604	0.6459	0.6117	0.088*
H16B	0.8567	0.5830	0.5685	0.088*
H16C	0.8955	0.6326	0.6340	0.088*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Rh1	0.0331 (3)	0.0354 (3)	0.02438 (14)	0.0012 (5)	0.000	0.000
O1	0.036 (2)	0.041 (2)	0.0255 (18)	0.0021 (19)	0.0032 (18)	−0.0047 (18)
N1	0.037 (4)	0.066 (5)	0.0301 (19)	−0.006 (7)	0.000	0.000
N2	0.031 (2)	0.041 (3)	0.033 (2)	0.006 (2)	−0.002 (2)	−0.003 (2)
C1	0.037 (4)	0.057 (5)	0.053 (3)	0.014 (7)	0.000	0.000
C2	0.039 (4)	0.068 (6)	0.035 (2)	−0.002 (10)	0.000	0.000
C3	0.093 (4)	0.062 (4)	0.045 (3)	0.025 (3)	−0.003 (3)	0.000 (2)
C4	0.155 (7)	0.086 (5)	0.057 (3)	0.049 (4)	−0.030 (4)	0.005 (3)
C5	0.206 (13)	0.116 (9)	0.030 (3)	0.033 (15)	0.000	0.000
C6	0.0387 (19)	0.0369 (18)	0.0373 (19)	0.0014 (16)	0.010 (3)	−0.007 (3)
C7	0.038 (2)	0.062 (3)	0.045 (3)	0.0112 (19)	0.003 (2)	−0.006 (3)
C8	0.036 (2)	0.040 (2)	0.029 (2)	0.005 (2)	−0.0011 (17)	−0.0024 (18)
C9	0.037 (3)	0.052 (3)	0.045 (2)	0.0105 (19)	−0.002 (2)	0.005 (2)
C10	0.056 (3)	0.056 (3)	0.050 (2)	0.013 (2)	−0.003 (3)	0.008 (3)
C11	0.049 (3)	0.084 (4)	0.042 (3)	0.025 (3)	−0.003 (2)	0.007 (3)
C12	0.039 (3)	0.060 (3)	0.043 (2)	0.007 (2)	−0.012 (2)	−0.011 (2)
C13	0.037 (2)	0.049 (3)	0.039 (2)	0.0027 (19)	−0.0053 (18)	0.003 (2)
C14	0.065 (4)	0.037 (3)	0.072 (3)	0.003 (3)	0.001 (3)	0.004 (3)
C15	0.072 (4)	0.121 (6)	0.048 (3)	0.010 (4)	−0.017 (3)	0.016 (4)
C16	0.057 (4)	0.051 (3)	0.068 (3)	−0.008 (3)	−0.018 (3)	−0.004 (3)

Geometric parameters (Å, º) top

Rh1—O1ⁱ	2.044 (3)	C7—H7B	0.9600
Rh1—O1ⁱⁱ	2.044 (3)	C7—H7C	0.9600
Rh1—N2	2.091 (4)	C8—C9	1.399 (6)
Rh1—N2ⁱⁱⁱ	2.091 (4)	C8—C13	1.406 (5)
Rh1—N1	2.222 (3)	C9—C10	1.389 (6)
Rh1—Rh1ⁱ	2.4290 (6)	C9—C14	1.504 (7)
O1—C6	1.290 (6)	C10—C11	1.370 (7)
O1—Rh1ⁱ	2.044 (3)	C10—H10	0.9300
N1—C1	1.106 (6)	C11—C12	1.385 (7)
N2—C6	1.300 (6)	C11—C15	1.504 (6)
N2—C8	1.432 (5)	C12—C13	1.406 (5)
C1—C2	1.463 (6)	C12—H12	0.9300
C2—C3ⁱⁱⁱ	1.375 (5)	C13—C16	1.489 (6)
C2—C3	1.375 (5)	C14—H14A	0.9600
C3—C4	1.380 (7)	C14—H14B	0.9600
C3—H3	0.9300	C14—H14C	0.9600
C4—C5	1.338 (6)	C15—H15A	0.9600
C4—H4	0.9300	C15—H15B	0.9600
C5—C4ⁱⁱⁱ	1.338 (6)	C15—H15C	0.9600
C5—H5	0.9300	C16—H16A	0.9600
C6—C7	1.510 (5)	C16—H16B	0.9600
C7—H7A	0.9600	C16—H16C	0.9600

O1ⁱ—Rh1—O1ⁱⁱ	177.67 (18)	C6—C7—H7C	109.5
O1ⁱ—Rh1—N2	88.85 (16)	H7A—C7—H7C	109.5
O1ⁱⁱ—Rh1—N2	91.03 (16)	H7B—C7—H7C	109.5
O1ⁱ—Rh1—N2ⁱⁱⁱ	91.03 (16)	C9—C8—C13	120.4 (4)
O1ⁱⁱ—Rh1—N2ⁱⁱⁱ	88.85 (16)	C9—C8—N2	121.0 (4)
N2—Rh1—N2ⁱⁱⁱ	174.1 (2)	C13—C8—N2	118.5 (4)
O1ⁱ—Rh1—N1	91.16 (9)	C10—C9—C8	118.4 (5)
O1ⁱⁱ—Rh1—N1	91.16 (9)	C10—C9—C14	120.7 (4)
N2—Rh1—N1	92.94 (11)	C8—C9—C14	120.9 (4)
N2ⁱⁱⁱ—Rh1—N1	92.94 (11)	C11—C10—C9	123.2 (5)
O1ⁱ—Rh1—Rh1ⁱ	88.84 (9)	C11—C10—H10	118.4
O1ⁱⁱ—Rh1—Rh1ⁱ	88.84 (9)	C9—C10—H10	118.4
N2—Rh1—Rh1ⁱ	87.06 (11)	C10—C11—C12	117.6 (4)
N2ⁱⁱⁱ—Rh1—Rh1ⁱ	87.06 (11)	C10—C11—C15	123.2 (6)
N1—Rh1—Rh1ⁱ	180.0	C12—C11—C15	119.2 (6)
C6—O1—Rh1ⁱ	120.6 (3)	C11—C12—C13	122.4 (5)
C1—N1—Rh1	180.000 (1)	C11—C12—H12	118.8
C6—N2—C8	121.4 (4)	C13—C12—H12	118.8
C6—N2—Rh1	119.9 (3)	C12—C13—C8	117.8 (4)
C8—N2—Rh1	118.6 (3)	C12—C13—C16	119.4 (4)
N1—C1—C2	180.000 (2)	C8—C13—C16	122.8 (4)
C3ⁱⁱⁱ—C2—C3	119.2 (5)	C9—C14—H14A	109.5
C3ⁱⁱⁱ—C2—C1	120.4 (3)	C9—C14—H14B	109.5
C3—C2—C1	120.4 (3)	H14A—C14—H14B	109.5
C2—C3—C4	119.0 (5)	C9—C14—H14C	109.5
C2—C3—H3	120.5	H14A—C14—H14C	109.5
C4—C3—H3	120.5	H14B—C14—H14C	109.5
C5—C4—C3	122.0 (5)	C11—C15—H15A	109.5
C5—C4—H4	119.0	C11—C15—H15B	109.5
C3—C4—H4	119.0	H15A—C15—H15B	109.5
C4—C5—C4ⁱⁱⁱ	118.8 (6)	C11—C15—H15C	109.5
C4—C5—H5	120.6	H15A—C15—H15C	109.5
C4ⁱⁱⁱ—C5—H5	120.6	H15B—C15—H15C	109.5
O1—C6—N2	123.5 (3)	C13—C16—H16A	109.5
O1—C6—C7	113.9 (4)	C13—C16—H16B	109.5
N2—C6—C7	122.6 (5)	H16A—C16—H16B	109.5
C6—C7—H7A	109.5	C13—C16—H16C	109.5
C6—C7—H7B	109.5	H16A—C16—H16C	109.5
H7A—C7—H7B	109.5	H16B—C16—H16C	109.5

O1—Rh1ⁱ—Rh1—N2	−1.10 (16)	Rh1—N2—C8—C9	91.8 (4)
O1ⁱ—Rh1—N2—C6	90.8 (3)	C6—N2—C8—C13	94.2 (5)
O1ⁱⁱ—Rh1—N2—C6	−86.9 (3)	Rh1—N2—C8—C13	−85.8 (4)
N1—Rh1—N2—C6	−178.1 (3)	C13—C8—C9—C10	3.2 (6)
Rh1ⁱ—Rh1—N2—C6	1.9 (3)	N2—C8—C9—C10	−174.3 (4)
O1ⁱ—Rh1—N2—C8	−89.2 (3)	C13—C8—C9—C14	−174.6 (4)
O1ⁱⁱ—Rh1—N2—C8	93.1 (3)	N2—C8—C9—C14	7.9 (6)
N1—Rh1—N2—C8	1.9 (3)	C8—C9—C10—C11	1.6 (7)
Rh1ⁱ—Rh1—N2—C8	−178.1 (3)	C14—C9—C10—C11	179.4 (5)
C3ⁱⁱⁱ—C2—C3—C4	0.8 (5)	C9—C10—C11—C12	−4.1 (7)
C1—C2—C3—C4	−179.2 (5)	C9—C10—C11—C15	177.8 (5)
C2—C3—C4—C5	−1.6 (10)	C10—C11—C12—C13	1.9 (7)
C3—C4—C5—C4ⁱⁱⁱ	0.8 (5)	C15—C11—C12—C13	−179.9 (4)
Rh1ⁱ—O1—C6—N2	0.6 (4)	C11—C12—C13—C8	2.6 (7)
Rh1ⁱ—O1—C6—C7	−179.0 (2)	C11—C12—C13—C16	−175.6 (5)
C8—N2—C6—O1	178.0 (4)	C9—C8—C13—C12	−5.2 (6)
Rh1—N2—C6—O1	−2.0 (5)	N2—C8—C13—C12	172.4 (4)
C8—N2—C6—C7	−2.4 (6)	C9—C8—C13—C16	172.9 (4)
Rh1—N2—C6—C7	177.6 (3)	N2—C8—C13—C16	−9.5 (6)
C6—N2—C8—C9	−88.2 (5)

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

Experimental details

Crystal data
Chemical formula	[Rh₂(C₁₁H₁₄NO)₄(C₇H₅N)₂]
M_r	1117.01
Crystal system, space group	Tetragonal, P42₁c
Temperature (K)	298
a, c (Å)	10.9928 (19), 21.4549 (19)
V (Å³)	2592.6 (7)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.69
Crystal size (mm)	0.18 × 0.13 × 0.07

Data collection
Diffractometer	Rigaku XtaLAB mini
Absorption correction	Multi-scan (REQAB; Jacobson, 1998)
T_min, T_max	0.618, 0.953
No. of measured, independent and observed [I > 2σ(I)] reflections	48863, 2969, 1950
R_int	0.105
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.074, 1.03
No. of reflections	2969
No. of parameters	165
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.64, −0.71
Absolute structure	Flack (1983), 1275 Friedel pairs
Absolute structure parameter	−0.03 (5)

Computer programs: CrystalClear (Rigaku, 2011), SIR2004 (Burla et al., 2005), SHELXL97 (Sheldrick, 2008), CrystalStructure (Rigaku, 2010).

Acknowledgements

The authors thank Dr Lee Daniels of Rigaku Americas for his training on the use of the Rigaku XtaLAB Mini and his helpful suggestions regarding this crystal structure. Support was provided by a Start Up Grant from ETSU. We thank Johnson Matthey for their generous loan of rhodium trichloride.

References

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