Mixed-ligand compounds incorporating quadruply bonded dimolybdenum(II) core: Syntheses, structures and reactivity studies

Abstract

Reaction of cis-[Mo 2(OAc) 2(CH 3CN) 6][BF 4] 2 with NP-Et,Me (2-ethyl-3-methyl-1,8-naphthyridine) in acetonitrile provides trans-[Mo 2(NP-Et,Me) 2(OAc) 2(CH 3CN)][BF 4] 2 ( 1). Partial protonation of 1 by HBF 4·Et 2O in acetonitrile leads to trans-[Mo 2(NP-Et,Me) 2(OAc)(CH 3CN) 3][BF 4] 3 ( 2). In both compounds, NP-R ligands are arranged in a head-to-head (HH) fashion leaving one of the axial sites vacant. Substitution of acetonitriles by NP-Me (3-methyl-1,8-naphthyridine) in trans-[Mo 2(NP-tz) 2(OAc)(CH 3CN) 2][BF 4] 3 provides trans-[Mo 2(NP-tz) 2(OAc)(NP-Me)][BF 4] 3 ( 3) with retention of configuration. Fully solvated dimolybdenum(II) compound reacts with NP-NH 2 to provide [Mo 2(NP-NH 2) 2(NP-NH)(CH 3CN) 2][BF 4] 3 ( 4) in which the NP-NH 2 ligands are trans and arranged in a HH fashion. The deprotonated ligand (NP-NH −) binds the dimetal unit utilizing naphthyridine nitrogen and amido nitrogen. Treatment of [Mo 2(NP-tz) 2(CH 3CN) 4][CF 3SO 3] 4 with bpym (2,2 ′-bipyrimidine) followed by crystallization in air provided an oxo complex [Mo 2(NP-tz) 2( μ 2-O) 2(bpym) 2][CF 3SO 3] 4 ( 5). Compounds 1– 5 have been characterized by a variety of spectroscopic techniques and by X-ray crystallography. The reactivity pattern is rationalized based on ligand labilities and thermodynamic stabilities.