ALLENE ADDUCTS OF DITUNGSTEN HEXAALKOXIDES - 3 MODES OF ALLENE COORDINATION TO DINUCLEAR CENTERS AS SEEN IN THE STRUCTURES OF W2(O-TERT-BU)6(C3H4), W2(O-TERT-BU)6(C3H4)2, AND W2(O-TERT-BU)6(C3H4)(CO)2

被引:42
作者
CHACON, ST
CHISHOLM, MH
FOLTING, K
HUFFMAN, JC
HAMPDENSMITH, MJ
机构
[1] INDIANA UNIV,DEPT CHEM,BLOOMINGTON,IN 47405
[2] INDIANA UNIV,CTR MOLEC STRUCT,BLOOMINGTON,IN 47405
关键词
D O I
10.1021/om00056a051
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Hydrocarbon solutions of W2(O-t-Bu)6 and allene (1 equiv) react at 0-degrees-C to give the monoallene adduct W2(O-t-Bu)6(C3H4) (1). Reactions involving W2(O-t-Bu)6 and an excess of allene (> 10 equiv) yield the 2:1 adduct W2(O-t-Bu)6(C3H4)2 (2). Compound 1 reacts with allene (> 10 equiv) and CO (> 2 equiv) to yield 2 and W2(O-t-Bu)6(C3H4)(CO)2 (3), respectively. A monoallene adduct involving methylallene and W2(O-t-Bu)6 has also been prepared, but reactions involving other W2(OR)6 compounds where R = i-Pr, c-Hex, c-Pen, and CH2-t-Bu all yield 2:1 adducts, W2(OR)6(C3H4)2. The molecular structures of 1-3 have been determined by low-temperature single-crystal X-ray crystallography. Crystal data for 1: monoclinic, P2(1)/n, a = 11.676 (1) angstrom, b = 16.771 (2) angstrom, c = 17.116 (2) angstrom, beta = 90.39 (0)-degrees, Z = 4. For 2: monoclinic, P2(1)/c, a = 9.516 (3) angstrom, b = 19.114 (7) angstrom, c = 19.438 (6) angstrom, beta = 103.32 (2)-degrees, Z = 4. For 3: monoclinic, P2(1)/c, a = 15.823 (4), angstrom, b = 18.807 (5) angstrom, c = 22.457 (6) angstrom, beta = 90.93 (1)-degrees, Z = 8. The monoallene adduct 1 has a mu-parallel-bridged allene with C-C-C = 141-degrees and W-W = 2.583 (1) angstrom, W-CH2 = 2.13 (1) angstrom, W-C = 2.09 (1) angstrom, and C-CH2 = 1.47 (1) angstrom. This novel W2(mu-C3H4) skeleton is supported by six terminal O-t-Bu ligands, three at each W center, W-O = 1.90 (2) angstrom (average). By contrast, the molecular structure of 2 shows a central W2(mu-eta-1,eta-3-C3H4) group with an attendant eta-2-allene ligand at one metal center. The W-W distance is 2.855 (1) angstrom and is supported by two bridging alkoxide ligands. The structure of 3 is related to that of 2 by the substitution of the terminal eta-2-allene by two eta-1-CO ligands. The W-W distance is 3.012 (4) angstrom, and the two O-t-Bu bridges are asymmetric with W-O = 1.99 (3) and 2.30 (4) angstrom (average), where the long W-O distances are trans to the CO ligands. The bonding in 3 may be viewed as W(6+)---W(2+) where the two CO ligands bond to a pseudooctahedral d4 metal center. The present work complements earlier studies involving the reactions between W2(OR)6 compounds with ethylene and alkynes, and the bonding in these adducts has been investigated by qualitative and semiempirical MO approaches.
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页码:3722 / 3735
页数:14
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