Single-crystal X-ray and neutron diffraction studies of an. eta. sup 2 -dihydrogen transition-metal complex: trans-(Fe(. eta. sup 2 -H sub 2 )(H)(PPh sub 2 CH sub 2 CH sub 2 PPh sub 2 ) sub 2 )BPh sub 4
- Univ. of Southern Maine, Portland (USA) Brookhaven National Lab., Upton, NY (USA)
- Brookhaven National Lab., Upton, NY (USA)
- Univ. of Toronto, Ontario (Canada)
The H-H distance in the {eta}{sup 2}H{sub 2} ligand in (Fe({eta}{sup 2}-H{sub 2})H(dppe){sub 2})BPh{sub 4}, 1 BPh{sub 4}, dppe = PPh{sub 2}CH{sub 2}CH{sub 2}PPh{sub 2}, is 0.816 (16) {angstrom} as determined by neutron diffraction on a crystal of volume 2.62 mm{sup 3} at 20 K: 1-BPh{sub 4} is monoclinic, space group C2/c, a = 16.999 (7) {angstrom}, b = 16.171 (2) {angstrom}, c = 22.114 (5) {angstrom}, {beta} = 102.52 (2){degree}, U = 5,934.4 (2) {angstrom}{sup 3}, and D{sub c} = 1.315 g cm{sup {minus}3} for Z = 4; R(F) = 0.071, R(F{sup 2}) = 0.110, R{sub w}(F{sup 2}) = 0.113 for 4,116 reflections with I {>=} 3{sigma}(I). The H-H separation is 0.87 (3) {angstrom} as determined by X-ray diffraction at 298 K: monoclinic, C2/c, a = 17.327 (3) {angstrom}, b = 16.407 (4) {angstrom}, c = 22.224 (3) {angstrom}, {beta} = 102.87 (1){degree}, U = 6,159.2 (1) {angstrom}{sup 3}, and D{sub c} = 1.267 g cm{sup {minus}3} for Z = 4; R(F) = 0.038, R{sub w}(F) = 0.034, for 3,673 reflections (I {>=} 3{sigma}(I)). These {eta}{sup 2}-H{sub 2} distances agree with the X-ray value of 0.89 (11) {angstrom} reported for the tetrafluoroborate salt, 1-BF{sub 4}. As was found for 1-BF{sub 4}, 1-BPh{sub 4} contains an {eta}{sup 2}-H{sub 2} ligand that is symmetrically side-on bonded to the iron and trans to the terminal hydride such that the Fe has a distorted octahedral configuration. These diffraction studies serve to calibrate H-H distances obtained by the T{sub 1} NMR method for dihydrogen complexes in solution where the H{sub 2} ligand is suggested to be rapidly spinning. The H-H distance is the same as that in W({eta}{sup 2}-H{sub 2})(CO){sub 3}(P(i-Pr){sub 3}){sub 2} despite the fact that the tungsten complex has a more labile H{sub 2} ligand. The terminal hydride-iron distance of 1.535 (12) {angstrom} as determined by neutron diffraction is shorter than the distances to the dihydrogen ligand (H-Fe = 1.616 (10) {angstrom}).
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6973450
- Journal Information:
- Journal of the American Chemical Society; (USA), Vol. 111:24; ISSN 0002-7863
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
TRANSITION ELEMENT COMPLEXES
CRYSTAL STRUCTURE
DATA ANALYSIS
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
NEUTRON DIFFRACTION
ORGANOMETALLIC COMPOUNDS
COHERENT SCATTERING
COMPLEXES
DATA
DIFFRACTION
ELEMENTS
INFORMATION
NUMERICAL DATA
ORGANIC COMPOUNDS
SCATTERING
360102* - Metals & Alloys- Structure & Phase Studies
400201 - Chemical & Physicochemical Properties