Synthesis and characterisation of alkynylacetal and alkynylaldehyde derivatives of Ni (II) and Fe(II) ; the X-ray crystal structure of Ni (η 5-C 5H 5) (PPh 3) CCCH (OEt) 2

Abstract

Alkynylacetal derivatives of Ni(II) and Fe(II) were synthesised using CuI in Et 3N from equimolar amounts of HCCCH(OEt) 2 with Ni( η 5-C 5H 5)(PPh 3)Br or Fe( η 5-C 5H 5) (CO) 2Cl, respectively. Deprotection of the Ni(II) complex Ni( η 5-C 5H 5)(PPh 3)CCCH(OEt) 2 ( 1) with oxalic acid conveniently yields the alkynylaldehyde complex Ni( η 5-C 5H 5) (PPh 3)CCCHO ( 2), whereas the Fe(II) complex could not be isolated from Fe( η 5-C 5H 5)(CO) 2CCCH(OEt) 2 ( 3) under similar conditions. The crystal structure of 1 has been determined and represents the first structural characterisation of a metalloalkynylacetal. Principal dimensions include NiP, 2.1301 (10), 2.1376(10) Å, Ni C alkyne, 1.853(4), 1.840(4) Å, CC 1.194(5), 1.193(4) Å and PNiC alkyne 90.27(11), 90.90(10) °, in the two independent molecules A and B, respectively.