Coordinated 1,3‐Diyne Diols as Organometallic Building Blocks for Large Macrocycles Containing Oxygen and Unsaturated Donor Units

The acid‐catalysed reaction of [{Co 2 (CO) 6 (μ‐η 2 ‐HOCH 2 C 2 ‐)} 2 ] ( 1a ) with a range of alkyl diols has been examined as means of preparing large crown‐type macrocycles (up to twenty eight‐membered) containing at least one coordinated 1,3‐diyne unit, multiple oxygen atoms and a variety of soft donor units. Thus, interaction of 1a with HOCH 2 (CH 2 ) n CH 2 OH, allows access to the monomeric cyclised complexes [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 OCH 2 (CH 2 ) n CH 2 O}] ( 3a : n = 2, 3b : n = 3, 3c : n = 4) along with the dimeric cyclised species [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 OCH 2 (CH 2 ) n CH 2 O}] 2 ( 4a : n = 2, 4b : n = 3, 4c : n = 4). Introduction of additional oxygen donor atoms into the macrocycle can be achieved by reaction of 1a with the glycols, HO(CH 2 CH 2 O) n H, to afford exclusively monomeric [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 O(CH 2 CH 2 O) n }] ( 5a : n = 3, 5b : n = 4). On the other hand, treatment of 1a with the 1,3‐diyne‐linked alkyl diols, HOCR 2 C≡CC≡CCR 2 OH, furnishes the more rigid monomeric [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 OCR 2 C 2 C 2 CR 2 O}] [ 6a : R = H, 6b : R = Me] and dimeric macrocycles [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 OCR 2 C 2 C 2 CR 2 O}] 2 [ 7a : R = H, 7b : R = Me], whereas the use of the alkynyl‐ or aryl‐linked alkyl diols, HOCH 2 (L)CH 2 OH, affords the unsymmetrical dimeric [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 } 2 O{OCH 2 (L)CH 2 O}] [ 8a : L = –C≡C–, 8b : L = 1,4‐C 6 H 4 ] and symmetrical dimeric species [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 OCH 2 (L)CH 2 O}] 2 [ 9a : L = –C≡C–, 9b : L = 1,4‐C 6 H 4 ]. Also isolated as a by‐product from all the above reactions is the self‐dimerised macrocycle [{Co 2 (CO) 6 } 2 { cyclo ‐μ‐η 2 :μ‐η 2 ‐CH 2 C 2 C 2 CH 2 O}] 2 ( 2 ) which can itself be synthesised more directly by treating 1a with catalytic quantities of HBF 4 · OEt 2 . Single crystal X‐ray diffraction studies have been performed on 2 , 3a , 5a , 7a , 8a , 8b and 9a . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)