Structure and bonding in the isoelectronic series CnHnP5-n+: is phosphorus a carbon copy?

TY - JOUR

T1 - Structure and bonding in the isoelectronic series CnHnP5-n+: is phosphorus a carbon copy?

AU - Pantazis, D A

AU - McGrady, J E

AU - Lynam, J M

AU - Russell, C A

AU - Green, M

PY - 2004

Y1 - 2004

N2 - The relative stabilities of different isomers of the isoelectronic series CnHnP5-n+ have been investigated using G3X theory. The results indicate that all species containing one or more phosphorus atom adopt a three-dimensional nido geometry, in marked contrast to the planar structure favoured by the all-carbon analogue. Within isomeric nido clusters, a strong correlation between total energy and the nucleus-independent chemical shift (NICS) indicates that three-dimensional aromaticity plays a significant role in determining the stability of the cluster. In the context of these nido clusters, the extent to which phosphorus is a carbon copy proves to be highly dependent on the global electronic environment. The first isolobal substitution of CH by P causes a complete switch from localised to delocalised bonding, accompanied by a transition from a two- to a three-dimensional structure, with the phosphorus atom showing a strong preference for the unique apical site. In contrast, further increasing the phosphorus content causes no further change in structure or bonding, suggesting that, at the basal sites, phosphorus is a rather better carbon copy. The low-energy pathways for interconversion of apical and basal atoms previously identified in C2H2P3+ prove to be a general feature of all members of the series.

AB - The relative stabilities of different isomers of the isoelectronic series CnHnP5-n+ have been investigated using G3X theory. The results indicate that all species containing one or more phosphorus atom adopt a three-dimensional nido geometry, in marked contrast to the planar structure favoured by the all-carbon analogue. Within isomeric nido clusters, a strong correlation between total energy and the nucleus-independent chemical shift (NICS) indicates that three-dimensional aromaticity plays a significant role in determining the stability of the cluster. In the context of these nido clusters, the extent to which phosphorus is a carbon copy proves to be highly dependent on the global electronic environment. The first isolobal substitution of CH by P causes a complete switch from localised to delocalised bonding, accompanied by a transition from a two- to a three-dimensional structure, with the phosphorus atom showing a strong preference for the unique apical site. In contrast, further increasing the phosphorus content causes no further change in structure or bonding, suggesting that, at the basal sites, phosphorus is a rather better carbon copy. The low-energy pathways for interconversion of apical and basal atoms previously identified in C2H2P3+ prove to be a general feature of all members of the series.

KW - CYCLOPENTADIENYL CATION

KW - POLYTOPAL REARRANGEMENTS

KW - NIDO-5-VERTEX CLUSTERS

KW - PYRAMIDAL CLUSTERS

KW - CHEMICAL-SHIFTS

KW - LASER-ABLATION

KW - (CH)5

KW - AROMATICITY

KW - STATES

KW - ANTIAROMATICITY

U2 - 10.1039/b405609d

DO - 10.1039/b405609d

M3 - Article

SN - 1477-9234

SP - 2080

EP - 2086

JO - Dalton Transactions

JF - Dalton Transactions

IS - 14

ER -