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Heptahapticity in Binuclear (Cycloheptatrienyl)molybdenum Carbonyl Derivatives: The Interplay between Ring Hapticity/Planarity and Metal–Metal Multiple Bonding
Author(s) -
Feng Xuejun,
Xie Chanyuan,
Xie Yaoming,
King R. Bruce,
Schaefer Henry F.
Publication year - 2010
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200900363
Subject(s) - molybdenum , chemistry , triple bond , planarity testing , bond length , crystallography , quadruple bond , metal , metal carbonyl , double bond , stereochemistry , single bond , chromium , oxidative addition , crystal structure , bond order , polymer chemistry , inorganic chemistry , catalysis , group (periodic table) , organic chemistry
Theoretical studies on the binuclear (cycloheptatrienyl)molybdenum carbonyl complexes [(C 7 H 7 ) 2 Mo 2 (CO) n ] ( n =6, 5, 4, 3, 2, 1, 0) indicate structures with fully bonded heptahapto η 7 ‐C 7 H 7 rings and four or fewer carbonyl groups to be energetically competitive. This is in striking contrast to the corresponding chromium derivatives. The lowest energy of such a structure for [(η 7 ‐C 7 H 7 ) 2 Mo 2 (CO) 4 ] is a singlet unbridged structure with a formal MoMo single bond with a length of approximately 3.2 Å. A higher‐energy pentahapto structure [(η 5 ‐C 7 H 7 ) 2 Mo 2 (CO) 4 ] is also predicted with a formal Mo≡Mo triple bond with a length of approximately 2.56 Å. Low‐energy structures are predicted for [(C 7 H 7 ) 2 Mo 2 (CO) 3 ] with two heptahapto η 7 ‐C 7 H 7 rings, either one or two bridging carbonyl groups, and formal MoMo double bonds with a length of approximately 2.8 Å. However, the global minimum for [(C 7 H 7 ) 2 Mo 2 (CO) 3 ] is a [(η 7 ‐C 7 H 7 )(η 5 ‐C 7 H 7 )Mo 2 (CO) 3 ] structure with a formal Mo≡Mo triple bond with a length of approximately 2.53 Å. The lowest‐energy structures for [(C 7 H 7 ) 2 Mo 2 (CO) 2 ] and [(C 7 H 7 ) 2 Mo 2 (CO)] have heptahapto η 7 ‐C 7 H 7 rings and predicted metal–metal bond lengths of approximately 2.54 and 2.31 Å, respectively, consistent with the formal triple and quadruple bonds, respectively, needed to give both metal atoms the favored 18‐electron configuration. The lowest‐energy structures for the carbonyl‐richer systems [(C 7 H 7 ) 2 Mo 2 (CO) n ] ( n =6, 5) contain one trihapto η 3 ‐C 7 H 7 ring and one pentahapto η 5 ‐C 7 H 7 ring.