The π‐Bonding Trend in VIB M(CO)6 Observed by NMR Spectroscopy — A Natural Bond Orbital View

• DOI: 10.1002/jccs.200900174
• Publication Date: 2015-05-01T18:07:23Z
• Authors: Shao‐Pin Wang; Ker‐Ming Yan; Wen‐Yi Hsu; Min‐Ying Huang; Hui‐Ying Wu
• Keywords: Natural bond orbital; Hyperconjugation

Abstract Analysis of carbonyl's 2π orbital populations, [2π], obtained by NMR relaxation time experiments VIB M(CO)(ẽ 6 ‐C H ) reveals the 3d < 4d 5d trend for M r̊ CO back‐donation, as reported values [2π] M(CO) 5 (quinuclidine). The same analysis performed on Mn(CO) 3 (ẽ C and Re(CO) also gives order back‐donation. distinctive ∼ > has been investigated second‐order perturbation theory within natural bond (NBO) scheme to search orbital‐based explanations. Besides conventional d π donor‐acceptor (DA) interaction in 5d, other DA arising from three‐center‐hyperbond (3CHB) hyperconjugation found >> 4d. Within family, this 3CHB is so much higher Cr(CO) than W(CO) render overall populations exhibiting trend.