Syntheses of Dimetallamacrocycles by Intramolecular Oxidative Couplings of Dinuclear Bis(1,3‐butadiynyl) Complexes: A New Approach to Steric Shielding in (sp‐Carbon chain)dirhenium Complexes [(η 5 ‐C 5 Me 5 )Re(NO)(PR 3 )(C≡CC≡CC≡CC≡C)(R 3 P)(ON)Re(η 5 ‐C 5 Me 5 )]

Reactions of the chiral racemic carbonyl complex [(η 5 ‐C 5 Me 5 )Re(NO)(NCCH 3 )(CO)] + ·BF 4 − and diphosphanes Ph 2 P(CH 2 ) n PPh 2 [2.4:1.0 mol ratio; n = 10 ( a ), 14 ( b )] give the (bridging phosphane)dirhenium complexes [(η 5 ‐C 5 Me 5 )Re(NO)(CO){μ‐[PPh 2 (CH 2 ) n Ph 2 P]‐ P , P }(OC)(ON)Re(η 5 C 5 Me 5 )] 2+ ·2BF 4 − (73−80%), which are reduced (LiAlH 4 ) to the dimethyl complexes [(η 5 ‐C 5 Me 5 )Re(NO)(CH 3 ){μ‐[PPh 2 (CH 2 ) n Ph 2 P]‐ P , P }(ON)(H 3 C)Re(η 5 ‐C 5 Me 5 )] (92−96%). Reactions with HBF 4 ·OEt 2 /C 6 H 5 Cl, HC≡CC≡CSiMe 3 , and t BuOK give, via π‐HC≡C adducts (89−94%), the bis(trimethylsilylbutadiynyl) complexes [(η 5 ‐C 5 Me 5 )Re(NO)(C≡CC≡ CSiMe 3 ){μ‐[PPh 2 (CH 2 ) n Ph 2 P]‐ P , P }(Me 3 SiC≡CC≡C)(ON)Re(η 5 ‐C 5 Me 5 )] ( 9a , b ; 95−66%). Desilylation (wet n Bu 4 NF) yields labile bis(butadiynyl) complexes, which are coupled [Cu(OAc) 2 /pyridine] to the μ‐octatetraynediyl complexes [(η 5 ‐C 5 Me 5 )Re(NO){μ‐[PPh 2 (CH 2 ) n Ph 2 P]‐ P , P }{μ‐(C 1 ≡CC≡CC≡CC≡C 8 )‐ C 1 ,C 8 }(ON)Re(η 5 ‐C 5 Me 5 )] ( 3a , b ; 10−23% from 9a , b ). These represent some of the few cases of intramolecular oxidative homocouplings of terminal alkynes in metal coordination spheres. The electrochemical properties of 3a , b , which undergo two one‐electron oxidations, are compared to nonmacrocyclic analogs that lack the diphosphane bridge. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)