Hydrogenating an organometallic carbon chain: buten-yn-diyl (CHCHCC) as a missing link

The sequential reaction of [Ru(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] with [Ru(CO)2(PPh3)3], and N-chlorosuccinimide affords the binuclear tetracarbido complex [Ru2(μ-C[triple bond, length as m-dash]CC[triple bond, length as m-dash]C)Cl2(CO)4(PPh3)4]. This may be compared with the first example of a butenyndiyl bridged bimetallic complex [Ru2(μ-CH[double bond, length as m-dash]CHC[triple bond, length as m-dash]C)Cl2(CO)4(PPh3)4] which is obtained from the reaction of [Ru(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] with [RuHCl(CO)(PPh3)3] followed by carbonylation. Characterisational data are discussed with reference to constituent model complexes [Ru(C[triple bond, length as m-dash]CH)Cl(CO)2(PPh3)2] and [Ru(CH[double bond, length as m-dash]CH2)Cl(CO)2(PPh3)2] in addition to DFT analysis of the bonding in the complexes [Ru2(μ-L)Cl2(CO)4(PMe3)4] (L = C[triple bond, length as m-dash]C-C[triple bond, length as m-dash]C, CH[double bond, length as m-dash]CHC[triple bond, length as m-dash]C, CH[double bond, length as m-dash]CH-CH[double bond, length as m-dash]CH). A range of other tetracarbido complexes which may be prepared from [RuCl(C[triple bond, length as m-dash]CC[triple bond, length as m-dash]CH)(CO)2(PPh3)2] is also described and includes [RuAu(μ-C4)Cl(CO)3(PPh3)3], [RuIr(μ-C4)Cl(CO)3(PPh3)4], [RuIr(μ-C4)H(NCMe)(CO)3(PPh3)4]BF4, [RuIr(μ-C4)Cl(η2-O2)(CO)3(PPh3)4], [Ru2Hg(μ-C4)2Cl2(CO)4(PPh3)4], [Ru2Pt(μ-C4)2Cl2(CO)4(PPh3)6] and [Ru2(μ-C4)HCl(CO)4(PPh3)4].