Potassium yttrium hexaniobium octadecachloride, KYNb₆Cl₁₈

The structure of potassium yttrium hexaniobium octadeca­chloride is built of anionic [Nb₆Cl₁₂ⁱCl₆^a]^4- cluster units (where `i' and `a' denote inner and outer ligands, respectively), linked together by K⁺ and Y³⁺ cations. The K⁺ cations occupy half of the tetrahedral vacancies in the face-centered cubic lattice of cluster units, and are coordinated by 12 chloride ligands. The Y atom is located in an octahedral site and is bonded to six outer chloride ligands.

S1. Comment

A large number of metal-rich niobium chlorides with [Nb₆Cl₁₈]^n--type cluster units have been previously crystallized using a variety of metal cations, for instance, the two series ARENb₆Cl₁₈ (where A is an alkali and RE is a rare earth element; Ihmaine et al., 1987, 1988, 1989) and ATiNb₆Cl₁₈ (where A is an alkali or group 13 element; Nagele et al., 2000), and the recently prepared cluster compounds Cs₂PbNb₆Cl₁₈ (Gulo et al., 2001) and K₂SrNb₆Cl₁₈ (Duraisamy & Lachgar, 2002), which contain Pb²⁺ and Sr²⁺, respectively. For the series ARENb₆Cl₁₈, the crystal structures of compounds with RE = Gd³⁺ (Ihmaine et al., 1987) and Lu³⁺ (Ihmaine et al., 1988, 1989) have been reported, while compounds with other rare-earth metal cations are still unknown.

In the present paper, we report the crystal structure of potassium yttrium hexaniobium octadecachloride, KYNb₆Cl₁₈. The title compound crystallizes in trigonal space group R3. The structure is based on discrete anionic cluster units, [Nb₆Clⁱ₁₂Cl^a₆]⁴⁻ (where `i' and `a' denote `inner' and `outer' ligands, respectively). The anionic cluster unit consists of an Nb₆ octahedron in which all edges are bridged by chloride ligands, and six other ligands are in apical positions (Fig. 1). The intra-cluster bond lengths, Nb—Nb = 2.9143 (6)–2.9182 (6), Nb—Clⁱ = 2.4476 (10)–2.4556 (10) and Nb—Cl^a = 2.6497 (10) Å are typical for [Nb₆Cl₁₈]⁴⁻ clusters. The Nb—Nb bond length indicates that the VEC (valence electrons per cluster) is 16. The three-dimensional structure of the title compound is based on the cluster units interlinked to each other by K⁺ and Y³⁺ cations (Fig. 2). The cluster layers are arranged according to a face-centered cubic stacking along the c axis. The K⁺ ions occupy tetrahedral vacancies between the units and are coordinated -to 12 Cl ligands, with K—Cl distances in the range 3.4520 (11)–3.5292 (10) Å. The yttrium ions are located in octahedral sites between the units and are bonded to six Cl ligands from six different units in a regular octahedral geometry, with Y—Cl distances of 2.6414 (10) Å. Only half of the tetrahedral sites are occupied by K in the title compound, in contrast to to situation in both Cs₂PbNb₆Cl₁₈ (Gulo et al., 2001) and K₂SrNb₆Cl₁₈ (Duraisamy & Lachgar, 2002) where the alkali metal site is fully occupied.

S2. Experimental

The title compound, KYNb₆Cl₁₈, was initially obtained as shiny black cuboctahedral crystals from a reaction proposed to yield an oxychloride compound of the composition K₂Y₂Nb₆Cl₁₄O₅. The compound was prepared quantitatively from a stoichiometric mixture containing NbCl₅ (Alfa, 99.8%), Nb powder (Alfa 99.8%), YCl₃ (Alfa 99.9%), and KCl (Alfa, 99.99%). The mixture was handled under an argon atmosphere and the reaction was performed in a sealed quartz tube at 1023 K over a period of 4 d. The heating and cooling ramps were 20 and 10 K h⁻¹, respectively.

Computing details

Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: SHELXTL (Bruker, 1999); program(s) used to solve structure: SHELXTL; program(s) used to refine structure: SHELXTL.

Figures

	Fig. 1. The chloride cluster anion, [Nb6Cl^i12Cl^a6]^4−, present in KYNb6Cl18. The superscripts `i' and 1a' denote inner and outer ligands, respectively.
	Fig. 2. Projection of the crystal structure of KYNb6Cl18 in the [110] direction.

Potassium yttrium hexaniobium octadecachloride

Crystal data

KYNb6Cl18	Dx = 3.500 Mg m^−3
Mr = 1323.57	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 38 reflections
Hall symbol: -R 3	θ = 2.7–12.5°
a = 9.2527 (6) Å	µ = 7.00 mm^−1
c = 25.410 (2) Å	T = 293 K
V = 1884.0 (2) Å^3	Truncated cuboctahedron, black
Z = 3	0.20 × 0.17 × 0.15 mm
F(000) = 1830

Data collection

Bruker P4 diffractometer	1045 reflections with I > 2σ(I)
Radiation source: normal-focus sealed tube	Rint = 0.028
Graphite monochromator	θmax = 31.0°, θmin = 2.4°
ω scans	h = −1→13
Absorption correction: empirical (using intensity measurements) via ψ scan (North et al., 1968)	k = −13→1
Tmin = 0.709, Tmax = 0.965	l = −1→36
1803 measured reflections	3 standard reflections every 297 reflections
1342 independent reflections	intensity decay: none

Refinement

Refinement on F^2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.032	Secondary atom site location: difference Fourier map
wR(F^2) = 0.050	w = 1/[σ^2(Fo^2) + (0.0137P)^2 + 0.4236P] where P = (Fo^2 + 2Fc^2)/3
S = 1.03	(Δ/σ)max = 0.001
1342 reflections	Δρmax = 0.77 e Å^−3
42 parameters	Δρmin = −0.90 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.

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	Occ. (<1)
Nb	0.04066 (4)	−0.15832 (4)	0.046790 (12)	0.00829 (7)
Cl1	0.08430 (13)	−0.36696 (13)	0.10715 (4)	0.01615 (19)
Cl2	−0.18582 (12)	−0.23352 (12)	0.11040 (3)	0.01529 (18)
Cl3	0.27860 (13)	−0.14169 (13)	−0.00074 (4)	0.01407 (18)
Y	0.33333	−0.33333	0.16667	0.01086 (17)
K	−0.33333	−0.66667	0.11103 (19)	0.0419 (11)	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Nb	0.00856 (15)	0.00834 (16)	0.00833 (11)	0.00451 (13)	−0.00005 (13)	0.00062 (13)
Cl1	0.0166 (5)	0.0164 (4)	0.0169 (4)	0.0094 (4)	−0.0032 (4)	0.0027 (4)
Cl2	0.0162 (5)	0.0181 (5)	0.0139 (4)	0.0104 (4)	0.0046 (4)	0.0058 (4)
Cl3	0.0139 (4)	0.0169 (5)	0.0159 (3)	0.0111 (4)	0.0023 (4)	0.0034 (3)
Y	0.0111 (3)	0.0111 (3)	0.0103 (4)	0.00556 (13)	0.000	0.000
K	0.0420 (16)	0.0420 (16)	0.042 (2)	0.0210 (8)	0.000	0.000

Geometric parameters (Å, º)

Nb—Cl3	2.4476 (10)	Y—Cl1^vii	2.6414 (10)
Nb—Cl3^i	2.4498 (10)	Y—Cl1^viii	2.6414 (10)
Nb—Cl2^ii	2.4554 (10)	Y—Cl1^ix	2.6414 (10)
Nb—Cl2	2.4556 (10)	Y—Cl1^x	2.6414 (10)
Nb—Cl1	2.6497 (10)	Y—Cl1^xi	2.6414 (10)
Nb—Nb^i	2.9143 (6)	K—Cl1^xii	3.4520 (11)
Nb—Nb^iii	2.9142 (6)	K—Cl1^xiii	3.4520 (11)
Nb—Nb^ii	2.9182 (6)	K—Cl2^x	3.463 (4)
Nb—Nb^iv	2.9182 (6)	K—Cl2^v	3.464 (4)
Cl1—Y	2.6414 (10)	K—Cl2^xiv	3.464 (4)
Cl1—K	3.4520 (11)	K—Cl3^vi	3.486 (4)
Cl2—Nb^iv	2.4554 (10)	K—Cl3^xv	3.486 (4)
Cl2—K^v	3.464 (4)	K—Cl3^i	3.486 (4)
Cl2—K	3.5292 (10)	K—Cl2^xii	3.5292 (10)
Cl3—Nb^iii	2.4498 (10)	K—Cl2^xiii	3.5292 (10)
Cl3—K^vi	3.486 (4)
Cl3—Nb—Cl3^i	88.818 (12)	Cl1—K—Cl1^xiii	119.919 (8)
Cl3—Nb—Cl2^ii	89.67 (4)	Cl1^xii—K—Cl2^x	61.00 (4)
Cl3^i—Nb—Cl2^ii	162.98 (4)	Cl1—K—Cl2^x	93.03 (7)
Cl3—Nb—Cl2	162.94 (3)	Cl1^xiii—K—Cl2^x	120.15 (11)
Cl3^i—Nb—Cl2	88.05 (4)	Cl1^xii—K—Cl2^v	120.15 (11)
Cl2^ii—Nb—Cl2	88.43 (5)	Cl1—K—Cl2^v	61.00 (4)
Cl3—Nb—Cl1	82.62 (3)	Cl1^xiii—K—Cl2^v	93.03 (7)
Cl3^i—Nb—Cl1	80.56 (3)	Cl2^x—K—Cl2^v	59.26 (8)
Cl2^ii—Nb—Cl1	82.43 (3)	Cl1^xii—K—Cl2^xiv	93.03 (7)
Cl2—Nb—Cl1	80.32 (3)	Cl1—K—Cl2^xiv	120.15 (11)
Cl3—Nb—Nb^i	95.50 (3)	Cl1^xiii—K—Cl2^xiv	61.00 (4)
Cl3^i—Nb—Nb^i	53.45 (3)	Cl2^x—K—Cl2^xiv	59.26 (8)
Cl2^ii—Nb—Nb^i	143.55 (3)	Cl2^v—K—Cl2^xiv	59.26 (8)
Cl2—Nb—Nb^i	96.08 (3)	Cl1^xii—K—Cl3^vi	56.81 (4)
Cl1—Nb—Nb^i	134.01 (3)	Cl1—K—Cl3^vi	89.81 (7)
Cl3—Nb—Nb^iii	53.52 (2)	Cl1^xiii—K—Cl3^vi	118.80 (11)
Cl3^i—Nb—Nb^iii	96.62 (3)	Cl2^x—K—Cl3^vi	108.69 (2)
Cl2^ii—Nb—Nb^iii	96.09 (3)	Cl2^v—K—Cl3^vi	145.52 (2)
Cl2—Nb—Nb^iii	143.54 (3)	Cl2^xiv—K—Cl3^vi	146.64 (3)
Cl1—Nb—Nb^iii	136.13 (3)	Cl1^xii—K—Cl3^xv	89.81 (7)
Nb^i—Nb—Nb^iii	60.090 (15)	Cl1—K—Cl3^xv	118.80 (11)
Cl3—Nb—Nb^ii	96.57 (3)	Cl1^xiii—K—Cl3^xv	56.81 (4)
Cl3^i—Nb—Nb^ii	143.44 (3)	Cl2^x—K—Cl3^xv	145.52 (2)
Cl2^ii—Nb—Nb^ii	53.55 (3)	Cl2^v—K—Cl3^xv	146.64 (3)
Cl2—Nb—Nb^ii	95.92 (2)	Cl2^xiv—K—Cl3^xv	108.69 (2)
Cl1—Nb—Nb^ii	135.97 (3)	Cl3^vi—K—Cl3^xv	62.01 (8)
Nb^i—Nb—Nb^ii	90.0	Cl1^xii—K—Cl3^i	118.80 (11)
Nb^iii—Nb—Nb^ii	59.955 (8)	Cl1—K—Cl3^i	56.81 (4)
Cl3—Nb—Nb^iv	143.51 (2)	Cl1^xiii—K—Cl3^i	89.81 (7)
Cl3^i—Nb—Nb^iv	95.35 (3)	Cl2^x—K—Cl3^i	146.64 (3)
Cl2^ii—Nb—Nb^iv	95.92 (2)	Cl2^v—K—Cl3^i	108.69 (2)
Cl2—Nb—Nb^iv	53.54 (3)	Cl2^xiv—K—Cl3^i	145.52 (2)
Cl1—Nb—Nb^iv	133.85 (3)	Cl3^vi—K—Cl3^i	62.01 (8)
Nb^i—Nb—Nb^iv	59.955 (8)	Cl3^xv—K—Cl3^i	62.01 (8)
Nb^iii—Nb—Nb^iv	90.0	Cl1^xii—K—Cl2^xii	56.33 (2)
Nb^ii—Nb—Nb^iv	60.0	Cl1—K—Cl2^xii	63.68 (2)
Y—Cl1—Nb	133.42 (4)	Cl1^xiii—K—Cl2^xii	175.87 (8)
Y—Cl1—K	129.68 (7)	Cl2^x—K—Cl2^xii	60.38 (5)
Nb—Cl1—K	94.86 (6)	Cl2^v—K—Cl2^xii	90.62 (7)
Nb^iv—Cl2—Nb	72.91 (3)	Cl2^xiv—K—Cl2^xii	119.64 (11)
Nb^iv—Cl2—K^v	106.06 (5)	Cl3^vi—K—Cl2^xii	58.15 (4)
Nb—Cl2—K^v	106.05 (5)	Cl3^xv—K—Cl2^xii	120.13 (11)
Nb^iv—Cl2—K	134.16 (8)	Cl3^i—K—Cl2^xii	90.85 (7)
Nb—Cl2—K	96.63 (6)	Cl1^xii—K—Cl2^xiii	63.68 (2)
K^v—Cl2—K	119.62 (5)	Cl1—K—Cl2^xiii	175.87 (8)
Nb—Cl3—Nb^iii	73.03 (3)	Cl1^xiii—K—Cl2^xiii	56.33 (2)
Nb—Cl3—K^vi	136.02 (4)	Cl2^x—K—Cl2^xiii	90.62 (7)
Nb^iii—Cl3—K^vi	97.85 (5)	Cl2^v—K—Cl2^xiii	119.64 (11)
Cl1—Y—Cl1^vii	90.47 (3)	Cl2^xiv—K—Cl2^xiii	60.38 (5)
Cl1—Y—Cl1^viii	90.47 (3)	Cl3^vi—K—Cl2^xiii	90.85 (7)
Cl1^vii—Y—Cl1^viii	90.47 (3)	Cl3^xv—K—Cl2^xiii	58.15 (4)
Cl1—Y—Cl1^ix	180.0	Cl3^i—K—Cl2^xiii	120.13 (11)
Cl1^vii—Y—Cl1^ix	89.53 (3)	Cl2^xii—K—Cl2^xiii	119.998 (1)
Cl1^viii—Y—Cl1^ix	89.53 (3)	Cl1^xii—K—Cl2	175.87 (8)
Cl1—Y—Cl1^x	89.53 (3)	Cl1—K—Cl2	56.33 (2)
Cl1^vii—Y—Cl1^x	180.0	Cl1^xiii—K—Cl2	63.68 (2)
Cl1^viii—Y—Cl1^x	89.53 (3)	Cl2^x—K—Cl2	119.64 (11)
Cl1^ix—Y—Cl1^x	90.47 (3)	Cl2^v—K—Cl2	60.38 (5)
Cl1—Y—Cl1^xi	89.53 (3)	Cl2^xiv—K—Cl2	90.62 (7)
Cl1^vii—Y—Cl1^xi	89.53 (3)	Cl3^vi—K—Cl2	120.13 (11)
Cl1^viii—Y—Cl1^xi	180.00 (4)	Cl3^xv—K—Cl2	90.85 (7)
Cl1^ix—Y—Cl1^xi	90.47 (3)	Cl3^i—K—Cl2	58.15 (4)
Cl1^x—Y—Cl1^xi	90.47 (3)	Cl2^xii—K—Cl2	119.998 (1)
Cl1^xii—K—Cl1	119.919 (8)	Cl2^xiii—K—Cl2	119.998 (1)
Cl1^xii—K—Cl1^xiii	119.919 (8)

Symmetry codes: (i) y, −x+y, −z; (ii) −y, x−y, z; (iii) x−y, x, −z; (iv) −x+y, −x, z; (v) −x−1/3, −y−2/3, −z+1/3; (vi) −x, −y−1, −z; (vii) −x+y+1, −x, z; (viii) −y, x−y−1, z; (ix) −x+2/3, −y−2/3, −z+1/3; (x) x−y−1/3, x−2/3, −z+1/3; (xi) y+2/3, −x+y+1/3, −z+1/3; (xii) −x+y, −x−1, z; (xiii) −y−1, x−y−1, z; (xiv) y−1/3, −x+y−2/3, −z+1/3; (xv) x−y−1, x−1, −z.