186787-99-5Relevant academic research and scientific papers
W2Cl4(NR2)2(PR′ 3)2 Molecules. 5. Preparation and Characterization of W2Cl4(NEt2)2(L-L) (L-L = dmpm, dmpe, dppe), W2Cl4(NBu2)2(L-L) (L-L = dmpm, dmpe), and W2Cl4(NHex2)2 (dmpm).
Albert Cotton,Dikarev, Evgeny V.,Wong, Wai-Yeung
, p. 902 - 912 (1997)
The triply-bonded ditungsten complexes W2Cl4(NEt2)2(L-L) (L-L = dmpm, dmpe), W2Cl4(NBu2)2(L-L) (L-L = dmpm, dmpe), and W2Cl4(NHex2)2(dmpm) are formed in the reactions between W2Cl4(NR2)2(NHR2) 2 (R = Et, Bu, Hex = n-C6H13 and bis(dimethylphosphino)methane (dmpm) or bis(dimethylphosphino)ethane (dmpe). In each case, three isomeric forms have been detected in solution by 31P{1H} NMR spectroscopy, and they are formulated as the trans,trans-, cis,trans-, and cis,cis-isomers. Complexes designated cis,trans have one P atom of the bridging diphosphine cis to the N atom on one W atom and another P atom trans to the N atom on the other W atom. The characterization of cis,trans-W2Cl4(NEt2)2(dmpm) ,(1). cis,cis-W2Cl4(NEt2(dmpm) (2), cis,trans-W2Cl4(NBu2)2(dmpm) (3), cis,cis-W2Cl4(NBu2)2(dmpm) (4a, 4b), cis,cis-W2Cl4(NHex2(dmpm) (5), cis,trans-W2Cl4(NEt2)2(dmpe) (6), and cis,trans-W2Cl4(NBu2)2(dmpe) (7) has been accomplished by X-ray crystallography. Pertinent crystal data are as follows: for 1, monoclinic space group C2/c, a = 33.210(3) ?, b = 8.725(4) ?, c = 17.052(4) ?, β= 100.44(1)°, Z = 8; for 2, monoclinic space group P21/c, a = 8.760(3) ?, b = 21.028(8) ?, c = 12.778(5) ?, β= 91.77(3)°, Z = 4; for 3, orthorhombic space group Pbca, a = 14.958(2) ?, b = 15.823(2) ?, c = 27.8014(9) ?, Z = 8; for 4a, C2/c, a = 18.011(4) ?, b = 17.221(4) ?, c = 21.264(6) ?, β= 103.33(2)°, Z = 8; for 4b (4a,b are polymorphic), Pbca, a = 14.772(2) ?, b = 17.188(1) ?, c = 25.370(3) ?, Z = 8; for 5, C2/c, a = 18.368(4) ?, b = 17.060(2) ?, c = 30.414(4) ?, β= 103.96(1)°, Z = 8; for 6, P21/c, a = 9.596(2) ?, b = 15.975(2) ?, c = 18.756(4) ?, β = 96.73(1)°, 2 = 4; for 7, monoclinic space group P21/n, a = 9.465(1) ?, b = 34.545(7) ?, c = 10.177(4) A, β= 97.220(1)°, Z = 4. Among them is one unprecedented type of geometrical isomer, namely, the cis,trans-isomers of W2Cl4P2N2 complexes. In order to structurally characterize a trans,trans-isomer for W2Cl4(NR2)2(L-L) molecules, a bis(diphenylphosphino)ethane (dppe) analogue, trans,trans-W2Cl4(NEt2)2(dppe) (8), has been prepared, and it crystallizes with a molecule of toluene, in the space group P21/n with a = 16.396(3) ?, b = 10.104(2) ?, c = 26.680(2) ?, β= 92.22(1)°, and Z = 4. Each of the compounds 1-8 has an essentially staggered W2Cl4P2N2 conformation with the W atoms bound by a triple bond. The W-W distances fall within the narrow range 2.314- 2.341 ?. All of them show significant torsion angles in the solid state.
